Thermal Design Margins for Heat Exchangers
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 TERMINOLOGY
5 REASONS FOR SPECIFYING A DESIGN MARGIN
5.1 Instantaneous Rates
5.2 Future Uprating
5.3 Plant Upsets
5.4 Process Control
5.5 Uncertainties in Properties
5.6 Uncertainties in Design Methods
5.7 Fouling
6 COMBINATION OF DESIGN MARGINS
7 CRITICAL AND NON-CRITICAL DUTIES
7.1 General
7.2 Penalties of Over-design
8 OPTIMIZATION OF EXCHANGER DUTY
9 WAYS OF PROVIDING DESIGN MARGINS
9.1 The Provision of Excess Surface
9.2 Decreasing the Design Temperature Difference
9.3 Increasing the Design Process Throughput
9.4 Increasing the Design Fouling Resistance
9.5 Reducing the Design Process Outlet Temperature Approach
9.6 Adjusting the Physical Properties
10 ACCURACY OF THE DESIGN METHODS FOR SHELL AND TUBE EXCHANGERS
10.1 Pressure Drop
10.2 Heat Transfer
11 SUGGESTED DESIGN MARGINS
11.1 No Phase Change Duties
11.2 Condensers
11.3 Boilers
12 EFFECT OF UNDER- OR OVER-SURFACE ON PERFORMANCE
FIGURES
1 EFFECT OF LENGTH ON EXCHANGER DUTY COUNTERCURRENT FLOW, C* = 1.0
2 EFFECT OF NUMBER OF TUBES ON EXCHANGER PERFORMANCE COUNTERCURRENT FLOW, C* = 1.0, ALL RESISTANCE IN TUBES
3 EFFECT OF TUBE LENGTH ON NUMBER OF TUBES, AREA AND PRESSURE DROP
101 Things That Can Go Wrong on a Primary Reformer - Best Practices GuideGerard B. Hawkins
This document discusses common problems that can occur in primary reformers and associated equipment. It identifies issues that can lead to plant shutdowns or efficiency losses, grouping them under catalysts, tubes, furnace boxes, burners, flue gas ducts, headers, and refractories. Some examples discussed include carbon formation, tube overheating, flame impingement, leaks in air preheaters, combustion air maldistribution, and damage to coffins. The document provides an overview of these issues to improve plant reliability over its lifespan.
This document provides best practices for loading catalyst into steam reformer tubes. It discusses using socks to uniformly distribute catalyst at a controlled rate of 3 feet or less of freefall. Pressure drop should be measured across tubes to ensure uniform packing. Common problems like bridging or uneven settling can be addressed through vibration or repacking. Precise loading techniques help minimize issues like temperature variations or methane slip that reduce efficiency and tube life.
Fired heaters face challenges regarding safety, inefficient operations, asset sustainability, and operator skillset. Most fired heaters have low levels of control and lack instrumentation for measuring critical parameters like oxygen and carbon monoxide in the combustion chamber. This introduces safety risks and prevents optimization of air-to-fuel ratio for efficiency. Industry standards recommend continuous monitoring of combustibles in the radiant section to improve safety.
Amine Gas Treating Unit - Best Practices - Troubleshooting Guide Gerard B. Hawkins
Amine Gas Treating Unit Best Practices - Troubleshooting Guide for H2S/CO2 Amine Systems
Contents
Process Capabilities for gas treating process
Typical Amine Treating
Typical Amine System Improvements
Primary Equipment Overview
Inlet Gas Knockout
Absorber
Three Phase Flash Tank
Lean/Rich Heat Exchanger
Regenerator
Filtration
Amine Reclaimer
Operating Difficulties Overview
Foaming
Failure to Meet Gas Specification
Solvent Losses
Corrosion
Typical Amine System Improvements
Degradation of Amines and Alkanolamines during Sour Gas Treating
APPENDIX
Best Practices - Troubleshooting Guide
Low Temperature Shift Catalyst Reduction Procedure
VSG-C111 as supplied contains copper oxide; it is activated for the low temperature shift duty by reducing the copper oxide component to metallic copper with hydrogen. The reaction is highly exothermic. In order to achieve maximum activity, good performance and long life, it is essential that the reduction is conducted under correctly controlled conditions. Great care must be taken to avoid thermal damage during this critical operation.
The document discusses air cooled heat exchangers. It describes how air cooled heat exchangers work by using air as the cooling medium, making them useful when water supply is limited. The document outlines the main components of air cooled heat exchangers, including axial fans, tube bundles, headers, fins and nozzles. It also discusses types of fans, headers, fins, factors that affect performance like fouling, and considerations for inspection and design of air cooled heat exchangers.
How to use the GBHE Reactor Technology Guides
0 INTRODUCTION / PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 BACKGROUND
5 THE DECISION TREE
6 GBHE REACTION ENGINEERING
7 GENERAL ASPECTS OF REACTOR TECHNOLOGY
7.1 Criteria of Reactor Performance
7.2 Factors of Economic Importance
7.3 Physicochemical Mechanisms
8 GENERAL GUIDE TO SELECTION OF REACTOR TYPE AND OPERATION
8.1 Choice of Reactor Type
8.2 Reaction Mechanism and Kinetics
8.3 Thermodynamics
8.4 Other Factors
9 GENERAL REFERENCES AND SOURCES OF
INFORMATION
APPENDICES
A RELATIONSHIP BEWTEEN DEFINED TERMS
FIGURES
1 DECISION TREE
2 RELATIVE YIELDS OF B FOR BATCH (OR PLUG FLOW) AND CST REACTORS
3 REACTOR SURVEY FORM
Gas-Solid-Liquid Mixing Systems
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 SELECTION OF EQUIPMENT
5 THREE-PHASE MASS TRANSFER WITH CHEMICAL REACTION
6 STIRRED VESSEL DESIGN
6.1 Agitator Design
6.2 Design for Solids Suspension
6.3 Vessel Design
6.4 Gas-Liquid Mass Transfer Coefficient and Surface Area
7 THREE-PHASE FLUIDIZED BEDS
7.1 Gas and Liquid Hold-Up
7.2 Calculation Procedure
7.3 Bubble Size
7.4 Mass Transfer
7.5 Heat Transfer
7.6 Elutriation
8 SLURRY REACTORS
8.1 Gas Rate
8.2 Mass Transfer
9 NOMENCLATURE
10 BIBLIOGRAPHY
DESIGN OF VENT GAS COLLECTION AND DESTRUCTION SYSTEMS Gerard B. Hawkins
DESIGN OF VENT GAS COLLECTION AND DESTRUCTION SYSTEMS
CONTENTS
1 INTRODUCTION
1.1 Purpose
1.2 Scope of this Guide
1.3 Use of the Guide
2 ENVIRONMENTAL ISSUES
2.1 Principal Concerns
2.2 Mechanisms for Ozone Formation
2.3 Photochemical Ozone Creation Potential
2.4 Health and Environmental Effects
2.5 Air Quality Standards for Ground Level Concentrations of Ozone, Targets for Reduction of VOC Discharges and Statutory Discharge Limits
3 VENTS REDUCTION PHILOSOPHY
3.1 Reduction at Source
3.2 End-of-pipe Treatment
4 METHODOLOGY FOR COLLECTION & ASSESSMENT OF PROCESS FLOW DATA
4.1 General
4.2 Identification of Vent Sources
4.3 Characterization of Vents
4.4 Quantification of Process Vent Flows
4.5 Component Flammability Data Collection
4.6 Identification of Operating Scenarios
4.7 Quantification of Flammability Characteristics for Combined Vents
4.8 Identification, Quantification and Assessment of Possibility of Air Ingress Routes
4.9 Tabulation of Data
4.10 Hazard Study and Risk Assessment
4.11 Note on Aqueous / Organic Wastes
4.12 Complexity of Systems
4.13 Summary
5 SAFE DESIGN OF VENT COLLECTION HEADER SYSTEMS
5.1 General
5.2 Process Design of Vent Headers
5.3 Liquid in Vent Headers
5.4 Materials of Construction
5.5 Static Electricity Hazard
5.6 Diversion Systems
5.7 Snuffing Systems
6 SAFE DESIGN OF THERMAL OXIDISERS
6.1 Introduction
6.2 Design Basis
6.3 Types of High Temperature Thermal Oxidizer
6.4 Refractories
6.5 Flue Gas Treatment
6.6 Control and Safety Systems
6.7 Project Program
6.8 Commissioning
6.9 Operational and Maintenance Management
APPENDICES
A GLOSSARY
B FLAMMABILITY
C EXAMPLE PROFORMA
D REFERENCES
DOCUMENTS REFERRED TO IN THIS PROCESS GUIDE
TABLE
1 PHOTOCHEMICAL OZONE CREATION POTENTIAL REFERENCED
TO ETHYLENE AS UNITY
FIGURES
1 SCHEMATIC OF TYPICAL VENT COLLECTION AND THERMAL OXIDIZER SYSTEM
2 TYPICAL KNOCK-OUT POT WITH LUTED DRAIN
3 SCHEMATIC OF DIVERSION SYSTEM
4 CONVENTIONAL VERTICAL THERMAL OXIDIZER
5 CONVENTIONAL OXIDIZER WITH INTEGRAL WATER SPARGER
6 THERMAL OXIDIZER WITH STAGED AIR INJECTION
7 DOWN-FIRED UNIT WITH WATER BATH QUENCH
8 FLAMELESS THERMAL OXIDATION UNIT
9 THERMAL OXIDIZER WITH REGENERATIVE HEAT RECOVERY
10 TYPICAL PROJECT PROGRAM
11 TYPICAL FLAMMABILITY DIAGRAM
12 EFFECT OF DILUTION WITH AIR
13 EFFECT OF DILUTION WITH AIR ON 100 Rm³ OF FLAMMABLE GAS
This document compares different methods for designing a shell and tube heat exchanger, including a manual design, HTRI software, and Aspen Exchanger Design and Rating (EDR). It first provides background on heat exchangers and describes the constraints that must be met in a heat exchanger design, including thermal and hydraulic evaluations. It then presents an example design case and shows the initial geometry selection. Finally, it discusses using HTRI and Aspen EDR software for simulation, rating, and designing shell and tube heat exchangers, noting both programs iterate to find a design meeting constraints.
This document provides an introduction to heat exchangers, including their classification, types, components, and design considerations. Heat exchangers transfer thermal energy between fluids or between fluids and solids. Common types include shell and tube, plate and frame, air cooled, and spiral designs. Key components of shell and tube heat exchangers are the shell, tubes, tubesheet, baffles, and nozzles. Tube layout, pitch, pass arrangements, and baffle design impact heat transfer and pressure drop. Bypass and leakage streams must be minimized for optimal performance.
This document discusses ammonia (NH3) formation over steam reforming catalysts. It provides rules of thumb for NH3 formation in primary and secondary reformers, noting it is kinetically limited and does not reach equilibrium. NH3 formation is influenced by nitrogen concentration, hydrogen concentration, temperature, catalyst activity, residence time, and pressure. The document also presents theoretical rate equations and discusses how process conditions like steam:carbon ratio affect NH3 production. Graphs demonstrate the effect of temperature and pressure on NH3 production.
Definition and selection of design temperature and pressure prg.gg.gen.0001Efemena Doroh
This document provides guidelines for determining the design temperature and pressure of equipment and piping for oil and chemical plants. It defines key terms like operating temperature, design temperature, minimum metal temperature, and design pressure. It outlines general criteria for setting design temperature, such as adding 30°C to the maximum operating temperature below 343°C. It also provides special considerations and guidelines for various equipment types. Minimum design metal temperature should be set to avoid material brittleness at low temperatures and pressures.
The document provides an overview of a module on flare system design and calculation. It discusses gas flaring definitions, components of a flare system, types of flares, environmental impacts, and considerations for flare system design and sizing calculations. Key aspects covered include gas flaring principles, when flaring occurs, composition of flared gases, reducing flaring through recovery systems, and sizing the flare header to minimize backpressure while limiting gas velocity.
Getting the Most Out of Your Refinery Hydrogen PlantGerard B. Hawkins
Getting the Most Out of Your Refinery Hydrogen Plant
Contents
Summary
1 Introduction
2 "On-purpose" Hydrogen Production
3 Operational Aspects
4 Uprating Options on the Steam Reformer
4.1 Steam Reforming Catalysts and Tube Metallurgy
4.2 Oxygen-blown Secondary Reformer
4.3 Pre-reforming
4.4 Post-reforming
5 Downstream Units
6 Summary of Uprating Options
7 Conclusions
Line Sizing presentation on Types and governing Equations.Hassan ElBanhawi
Based on my 8 years of experience in Oil & Gas industry I can claim that you can find here All what you need to know about Pipeline Sizing. This is an introduction to understand more about their:-
-The basic idea.
-Simplified method for calculations.
-Equations.
-Data Tables.
-Worked Examples.
-Excel Sheets for Calculation.
-Links to other topics which may be interesting.
You can find also more at:
http://hassanelbanhawi.com/staticequipment/linesizing/
All the data and the illustrative figures presented here can be found through two reference books:-
ENGINEERING DATA BOOK by Gas Processors Suppliers Association
Process Technology - Equipment and Systems by Charles E. Thomas
Thank you.
CENTRIFUGAL COMPRESSOR SETTLE OUT CONDITIONS TUTORIALVijay Sarathy
Centrifugal Compressors are a preferred choice in gas transportation industry, mainly due to their ability to cater to varying loads. In the event of a compressor shutdown as a planned event, i.e., normal shutdown (NSD), the anti-surge valve is opened to recycle gas from the discharge back to the suction (thereby moving the operating point away from the surge line) and the compressor is tripped via the driver (electric motor or Gas turbine / Steam Turbine). In the case of an unplanned event, i.e., emergency shutdown such as power failure, the compressor trips first followed by the anti-surge valve opening. In doing so, the gas content in the suction side & discharge side mix.
Therefore, settle out conditions is explained as the equilibrium pressure and temperature reached in the compressor piping and equipment volume following a compressor shutdown
The Design and Layout of Vertical Thermosyphon ReboilersGerard B. Hawkins
The Design and Layout of Vertical Thermosyphon Reboilers
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 THE DESIGN PROBLEM
5 COMPUTER PROGRAMS
6 GENERAL CONSIDERATIONS
6.1 Heating Medium Temperature
6.2 Fouling Resistance
7 DESIGN PARAMETERS
7.1 Overall Arrangement and Specifications
7.2 Geometry Elements
8 ANALYSIS OF COMMERCIALLY AVAILABLE
PROGRAM RESULTS
8.1 Main Results
8.2 Supplementary Results
8.3 Error Analysis
8.4 Adjustments to Design
9 OPERATING RANGE
10 CONTROL
10.1 Control of Condensing Heating Medium Pressure
10.2 Control of The Condensate Level
10.3 Control of Sensible Fluid Flow Rate
11 LAYOUT
11.1 Factors Influencing Design
11.2 A Standard Layout
12 BIBLIOGRAPHY
Selection and Design of Condensers
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 CHOICE OF COOLANT
5 LAYOUT CONSIDERATIONS
5.1 Distillation Column Condensers
5.2 Other Process Condensers
6 CONTROL
6.1 Distillation Columns
6.2 Water Cooled Condensers
6.3 Refrigerant Condensers
7 GENERAL DESIGN CONSIDERATIONS
7.1 Heat Transfer Resistances
7.2 Pressure Drop
7.3 Handling of Inerts
7.4 Vapor Inlet Design
7.5 Drainage of Condensate
8 SUMMARY OF TYPES AVAILABLE
8.1 Direct Contact Condensers
8.2 Shell and Tube Exchangers
8.3 Air Cooled Heat Exchangers
8.4 Spiral Plate Heat Exchangers
8.5 Internal Condensers
8.6 Plate Heat Exchangers
8.7 Plate-Fin Heat Exchangers
8.8 Other Compact Designs
9 BIBLIOGRAPHY
FIGURES
1 DIRECT CONTACT CONDENSER WITH INDIRECT COOLER FOR RECYCLED CONDENSATE
2 SPRAY CONDENSER
3 TRAY TYPE CONDENSER
4 THREE PASS TUBE SIDE CONDENSER WITH INTERPASS LUTING FOR CONDENSATE DRAINAGE
5 CROSS FLOW CONDENSER WITH SINGLE PASS COOLANT
Pipeline Design for Isothermal, Turbulent Flow of Non-Newtonian FluidsGerard B. Hawkins
Pipeline Design for Isothermal, Turbulent Flow of Non-Newtonian Fluids
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 DESCRIPTION OF ANOMALOUS EFFECTS
4.1 Wall Slip
4.2 Drag Reduction in Polymeric Materials
4.3 Transition Delay by Polymeric Materials
4.4 Drag Reduction in Suspensions
5 DESIGN PROCEDURE FOR PRESSURE DROP
IN TURBULENT PIPE FLOW IN THE ABSENCE
OF DRAG REDUCTION
5.1 Pressure Drop in the Absence of Wall Slip and
Drag Reduction
5.2 Wall Slip
5.3 Pipe Roughness
5.4 Pipe Fittings
6 DESIGN PROCEDURE FOR DRAG REDUCING
POLYMERIC MATERIALS
6.1 General
6.2 Transition Delay
6.3 Pipe Roughness
6.4 Pipe Fittings
7 DESIGN PROCEDURE FOR DRAG REDUCING
FIBRE SUSPENSIONS
8 BIBLIOGRAPHY
9 NOMENCLATURE
FIGURES
1 DRAG REDUCTION PHENOMENA
2 TRANSITION DELAY PHENOMENA
3 PROCEDURE FOR THE CALCULATION OF
PRESSURE DROP IN TURBULENT NON-NEWTONIAN
PIPE FLOW
4 TYPICAL RELATIONSHIP FOR Ψ VERSUS ʋ*
Turbulent Heat Transfer to Non Newtonian Fluids in Circular TubesGerard B. Hawkins
Turbulent Heat Transfer to Non Newtonian Fluids in Circular Tubes
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 THE INTEGRATION OF THE ENERGY EQUATION
5 THE EDDY VISCOSITY FOR NON-NEWTONIAN AND DRAG REDUCING FLUIDS
6 THE CALCULATION OF HEAT TRANSFER
COEFFICIENTS FOR NON-NEWTONIAN AND DRAG
REDUCING FLUIDS IN TURBULENT PIPE FLOW
6.1 General
6.2 Drag Reducing Fibre Suspensions
6.3 Transition Delay
7 NOMENCLATURE
8 BIBLIOGRAPHY
Fouling Resistances for Cooling Water
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 GENERAL
5 COOLING WATER FOULING
6 CHROMATE SYSTEMS
6.1 General
6.2 Constraints
6.3 Requirements
6.4 Fouling resistances
7 NON-CHROMATE SYSTEMS
7.1 General
7.2 Requirements and Constraints
7.3 Fouling resistances
8 UNTREATED COOLING WATER
9 MATERIALS OTHER THAN MILD STEEL
APPENDICES
A FOULING RESISTANCES FOR COOLING WATER
B FOULING FILM THICKNESS
How to Use the GBHE Mixing Guides
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 THE MIXING GUIDES
4.1 Mixing Guides
4.2 GBHE Mixing and Agitation Manual
5 DEVICE SELECTION
6 MIXING QUESTIONNAIRE
6.1 What is being mixed?
6.2 Why is it being mixed?
6.3 How is it to be mixed?
6.4 Is Heat Transfer Important?
6.5 Is Mixing Time Important?
6.6 Is Inventory Important?
6.7 Is Subsequent Phase Separation Important?
6.8 What Quantities?
6.9 What are the Selection Criteria?
6.10 What Data are required?
7 BASICS
7.1 Bulk Movement
7.2 Shear and Elongation
7.3 Turbulent Diffusion
7.4 Molecular Diffusion
7.5 Mixing Mechanisms
APPENDICES
A ROTATING MIXING DEVICES
B MIXING DEVICES WITHOUT MOVING PARTS
Pipeline Design for Isothermal, Laminar Flow of Non-Newtonian FluidsGerard B. Hawkins
Pipeline Design for Isothermal, Laminar Flow of Non-Newtonian Fluids
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 RHEOLOGICAL BEHAVIOR OF PURELY VISCOUS
NON-NEWTONIAN FLUIDS
4.1 Experimental Characterization
4.2 Rheological Models
5 PRESSURE DROP-FLOW RATE RELATIONSHIPS
BASED DIRECTLY ON EXPERIMENTAL DATA
5.1 Use of Shear Stress – Shear Rate Data
5.2 Tubular Viscometer Data
6 PRESSURE DROP – FLOW RATE RELATIONSHIPS BASED ON RHEOLOGICAL MODELS
7 LOSSES IN PIPE FITTINGS
7.1 Entrances Losses
7.2 Expansion Effects
7.3 Contraction Losses
7.4 Valves
7.5 Bends
8 EFFECT OF WALL SLIP
9 VELOCITY PROFILES
9.1 Velocity Profile from Experimental Flow-Curve
9.2 Velocity Profile from Rheological Model
9.3 Residence Time Distribution
10 CHECKS ON THE VALIDITY OF THE
DESIGN PROCEDURES
10.1 Rheological Behavior
10.2 Validity of Experimental Data
10.2 Check on Laminar Flow
11 NOMENCLATURE
12 REFERENCES
FIGURES
1 FLOW CURVES FOR PURELY VISCOUS FLUIDS
2 PLOTS OF D∆P/4L VERSUS 32Q/ɳD3 FOR PURELY VISCOUS FLUIDS
3 LOG-LOG PLOT OF t VERSUS ý
4 FLOW CURVE FOR A BINGHAM PLASTIC
5 LOG-LOG PLOT FOR A GENERALIZED BINGHAM
PLASTIC
6 CORRELATION OF ENTRANCE LOSS
7 CORRELATION OF EXPANSION LOSS
8 EFFECT OF “WALL SLIP” ON VELOCITY PROFILE
9 D∆P/4L VERSUS Q/ɳR3 WITH WALL SLIP
10 EVALUATION OFUs WITH Ʈw
11 VARIATION OF Us WITH Ʈw
12 PLOT OF D∆P/4L VERSUS 8 (ū- Us)/D FOR
CONDITIONS OF WALL SLIP
13 CUMULATIVE RESIDENCE TIME DISTRIBUTION
TO POWER LAW FLUIDS
14 EFFECTS OF TUBE LENGTH AND DIAMETER ON
RELATIONSHIP BETWEEN D∆P/4L AND 32Q/ɳD3
Shortcut Methods of Distillation Design
0 INTRODUCTION/PURPOSE
1 SCOPE
2 ESTIMATIONOF PLATEAGE AND REFLUX
REQUIREMENTS
2.1 Generalized Procedure for Nmin and Rmin
2.2 Equation based Procedure for Nmin and Rmin
3 PREDICTION OF OVERALL PLATE EFFICIENCY
4 SIZING OF MAIN PLANT ITEMS
4.1 Column Diameter
4.2 Surface Area of Condensers and Reboilers
FIGURES
1 NON-IDEAL EQUILIBRIUM CURVE
2 AT A GLANCE CHART BASED ON FENSKE,
UNDERWOOD
3 PLATE EFFICIENCY CORRELATION OF O’CONNEL
TEMPERATURE MEASUREMENT:
RESISTANCE ELEMENTS AND THERMOCOUPLES
SPECIFICATION OF FUNCTION
DESCRIPTION OF FLUID
NORMAL OPERATING TEMPERATURE
REQUIRED TEMPERATURE RANGE
ALARM SETTINGS
TRIP SETTINGS
FLUID VELOCITY
REYNOLDS NUMBER
LINE SIZE
LINE REFERENCE
EQUIPMENT REFERENCE
NOZZLE SIZE
MINIMUM DESIGN PRESSURE
CORRESPONDING TEMPERATURE
MAXIMUM DESIGN PRESSURE
CORRESPONDING TEMPERATURE
GBH Enterprises provides guidelines for managing pressure systems, pressure relief streams, protective devices, and pressure vessels. The document outlines responsibilities for design review, registration, and periodic inspection to ensure safety. It also references national regulations and standards that must be followed.
Reactor Modeling Tools - An Overview
CONTENTS
1 SCOPE
2 OPTIONS IN REACTOR MODELING
2.1 General
2.2 Level of Complexity of Model
2.3 Mode of Operation of Model
2.4 Deterministic versus Empirical Modeling
2.5 Platforms for Model
2.6 Steady State versus Dynamic Model
2.7 Dimensions Modeled in Reactor
2.8 Scale of Modeling for Multiphase Reactors
2.9 Writing and Using the Model
APPENDICES
A CHARACTERISTICS OF DIFFERENT REACTOR MODELS
B NEEDS FOR MODELING AT DIFFERENT SCALES IN
HETEROGENEOUS CATALYTIC REACTORS
C REACTOR MODELS EMPLOYED WITHIN GBHE
DOCUMENTS REFERRED TO IN THIS PROCESS ENGINEERING GUIDE
This document provides an engineering design guide for pumps used in ammonium nitrate service. It discusses the properties of ammonium nitrate and its solutions, including decomposition, combustion, detonation, density, viscosity, vapor pressure, and freezing point. It also covers the calculation of pump duty, choice of pump type (centrifugal, rotary, reciprocating), recommended line diagrams, construction features of different pump types, materials of construction, and appendices on bearing lubricants. The guide is intended to help with the integration and design of pump systems for handling ammonium nitrate and its solutions in industrial processes.
Mixing of Solid-Liquid Systems
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 TYPICAL APPLICATIONS
5 AGITATED VESSELS
5.1 Suspension of Heavier-than-Liquid Solids
5.1.1 Dispersion
5.1.2 Agitator Speed Correlation
5.2 Floating Solids
5.3 Mass Transfer
6 JET MIXING FOR SOLID LIQUID AGITATION
6.1 Flat Bottomed Vessel
6.2 Changes in the Shape of the Vessel Base
7 NOMENCLATURE
8 BIBLIOGRAPHY
APPENDICES
A WORKED EXAMPLE
TABLES
1 VALUES OF Po AND ZWIETERING CONSTANT "S"
FOR USE IN EQUATION 1
FIGURES
1 RECOMMENDED CONFIGURATION
2 RECOMMENDED CONFIGURATION FOR DRAW-DOWN OF FLOATING SOLIDS IN AGITATED VESSEL
3 ALTERNATIVE RECOMMENDED CONFIGURATION
FOR DRAW-DOWN OF FLOATING SOLIDS IN FOR
AGITATED VESSEL
4 JET MIXING FOR SOLIDS SUSPENSION
5 ESTIMATION OF S FROM KNOWN DATA
This document appears to be the title page and table of contents for the second edition of the book "Heat Exchanger Design Handbook" by Kuppan Thulukkanam. The title page provides publication details about the book and its author. The table of contents gives an overview of the book's chapter structure and topics covered, including an introduction to heat exchangers, their classification and selection, thermohydraulic fundamentals, design considerations for different heat exchanger types, and applications.
The Preliminary Choice of Fan or Compressor
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 METHOD FOR PRELIMINARY SELECTION
OF COMPRESSOR
5 PROCESS DATA SHEET
5.1 Essential Data for the Completion of a
Process Data Sheet
5.2 Gas Properties
5.3 Discharge Requirements
6 PRELIMINARY CHOICE OF FAN AND
COMPRESSOR TYPE
6.1 Essential Data for Preliminary Selection
7 FAN AND COMPRESSOR APPLICATIONS
7.1 Fans
7.2 Centrifugal Compressors
7.3 Axial Compressors
7.4 Reciprocating Compressors
7.5 Screw Compressors
7.6 Positive Displacement Blowers
7.7 Sliding Vane Compressors
7.8 Liquid Ring Compressors
8 PROVISION OF INSTALLED SPARES
9 PRELIMINARY ESTIMATE OF COSTS
Batch Distillation
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 BACKGROUND TO THE DESIGN
4.1 General
4.2 Choice of batch/continuous operation
4.3 Boiling point curve and cut policy
4.4 Method of design
4.5 Scope of calculations required for design
5 SIMPLE BATCH DISTILLATION
6 FRACTIONAL BATCH DISTILLATION
6.1 General
6.2 Approximate methods
6.3 Rigorous design - use of a computer model
6.4 Other factors influencing the design
6.4.1 Occupation
6.4.2 Choice of Batch Rectification or Stripping
6.4.3 Batch size
6.4.4 Initial estimate of cut policy
6.4.5 Liquid Holdup
6.4.6 Total reflux operation and heating-up time
6.4.7 Column operating pressure
6.5 Optimum Design of the Batch Still
6.6 Special design problems
7 GENERAL ASPECTS OF EQUIPMENT DESIGN
7.1 Kettle reboilers
7.2 Column Internals
7.3 Condensers and reflux split boxes
8 PROCESS CONTROL AND INSTRUMENTATION IN
BATCH DISTILLATION
9 MECHANICAL DESIGN FEATURES
10 BIBLIOGRAPHY
APPENDICES
A McCABE - THIELE METHOD - TYPICAL EXAMPLE
Cost Estimating: Turbo Blowers
This GBHE Engineering Guide provides information to assist in preparing an estimate for the cost of single stage, integrally geared, turbo-blowers. The data contained is based on analysis of past purchases for projects and offers by vendors.
Design and Simulation of Continuous Distillation ColumnsGerard B. Hawkins
Design and Simulation of Continuous Distillation Columns
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 FRACTIONAL DISTILLATION
5 ROUGH METHOD OF COLUMN DESIGN
5.1 Sharp Separations
5.2 Sloppy Separations
6 DETAIL DESIGN USING THE CHEMCAD DISTILLATION PROGRAM
6.1 Sharp Separations
6.2 Sloppy Separations
7 COMPLEX COLUMNS
7.1 Multiple Feeds
7.2 Sidestream Take-Offs
8 DESIGN USING A LABORATORY COLUMN
SIMULATION
9 DESIGN USING ACTUAL PLANT DATA
9.1 Uprating or Debottlenecking Exercises
10 REFERENCES
APPENDICES
A WORKED EXAMPLE
B SLOPPY SEPARATIONS
C SIMULATION USING PLANT DATA : CASE HISTORIES
TABLES
Reciprocating Compressors - Protection against Crank Case ExplosionsGerard B. Hawkins
Reciprocating Compressors - Protection against Crank Case Explosions
1 SCOPE
2 OIL MIST/AIR MIXTURE EXPLOSIONS
3 PREVENTION AND PROTECTION
3.1 Design
3.2 Maintenance and Operation
FIGURES
1 FLAMMABILITY LIMITS AND SPONTANEOUS IGNITION REGION FOR MIXTURES OF LUBRICATING OIL VAPOR IN AIR.
This document provides guidance on implementing procedures for managing critical pressure systems as outlined in PEG 4. It covers the design, manufacture, repair, modification and periodic examination of pressure vessels, piping systems, and pressure relief streams. Key requirements include using recognized standards, qualified personnel, design verification, registration of equipment, and periodic inspections to ensure safety. The document is intended to support the development of detailed local engineering procedures for managing pressure equipment over its lifecycle.
Fixed Bed Reactor Scale-up Checklist
The purpose of this checklist is to identify the stages and potential problems associated with the scale up of fixed bed reactors from the drawing board to the full scale plant, and to determine how they should be checked.
The checking can be done using various methods. These are:
• Literature data.
• Lab testing.
• Calculation.
• Modeling.
• Semi-tech testing.
• Piloting or Sidestream testing.
Identifying the stages that need to be addressed for a particular catalyst/reactor development will help in estimating the time needed for the development of the reactor
Data Sources For Calculating Chemical Reaction EquilibriaGerard B. Hawkins
Data Sources For Calculating Chemical Reaction Equilibria
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 BACKGROUND TO THEORY
5 BIBLIOGRAPHY
Large Water Pumps
CONTENTS
1 SCOPE
SECTION ONE: INTEGRATION OF PUMPS INTO THE PROCESS
2 PROPERTIES OF FLUID
2.1 Cooling Water
2.2 Brine
2.3 Estuary Water
2.4 Harbor Water
2.5 Oil-field water
3 CALCULATION OF DUTY
4 CHOICE OF TYPE AND NUMBER OF PUMPS
4.1 Type of Pump
4.2 Points to Consider
4.3 Number of Pumps
5 RECOMMENDED LINE DIAGRAM
5.1 Check List for Each Pump
6 RECOMMENDED LAYOUT
SECTION TWO: CONSTRUCTION FEATURES
7 HORIZONTAL, AXIALLY SPLIT CASING PUMPS
7.1 Pressure Casing
7.2 Bolting
7.3 Flanges and Connections
7.4 Rotating Elements
7.5 Wear Rings
7.6 Running Clearances
7.7 Mechanical Seals
7.8 Packed Glands
7.9 Bearings and Bearing Housings
7.10 Lubrication
7.11 Couplings
7.12 Guards
7.13 Baseplates
7.14 Flywheels
8 VERTICAL PUMPS
8.1 General
8.2 Pressure Casing
8.3 Bolting
8.4 Flanges and Connections
8.5 Rotating Element
8.6 Packed Glands
8.7 Bearings and Bearing Housings
8.8 Pump Head
8.9 Column Pipes
8.10 Line Shaft and Couplings
8.11 Reverse Rotation
8.12 Gearboxes
9 MATERIALS
9.1 Castings
9.2 Casings
9.3 Impellers
9.4 Shafts
9.5 Shaft Sleeves
9.6 Bolts and Nuts
10 DRIVERS
10.1 Electric Motor Drives
11 BIBLIOGRAPHY
APPENDICES:
A COOLING WATER - EUROPEAN SITE
B TIDAL RIVER ESTUARY
C FLYWHEEL INERTIA FOR PRESSURE SURGE ABATEMENT
D RESIN COATING OF CASINGS FOR WATER PUMPS
E AREA RATIO METHOD
F NOTES ON PUMP IMPELLERS CASTINGS
G LIMIT ON SHAFT DIAMETER FOR HORIZONTAL PUMPS HAVING
ONE DOUBLE-ENTRY IMPELLER SUPPORTED BETWEEN BEARINGS
H FORCES AND BENDING MOMENTS ON RISING MAIN ASSEMBLY
I POWER COSTS
J PUTATIVE COST COMPARISON SHEET
K TECHNICAL COMPARISON SHEETS
FIGURES
2.1 VAPOR TEMPERATURE CURVES
2.2 DENSITY TEMPERATURE CURVES
3.1 TYPICAL HEAD OF PUMPS
3.2 TOTAL HEAD OF VERTICAL IMMERSED PUMP
3.3 TYPICAL TIDAL RIVER ESTUARY LEVELS
3.5 SUBMERGENCE LIMITS
4.1 TYPES OF PUMP
4.2 GUIDE TO PUMP TYPE AND SPEED
5.1 TYPICAL LINE DIAGRAM
6 GUIDE TO SUCTION PIPEWORK DESIGN
7 CASING AND IMPELLER DETAILS
8.1 DRY WELL AND WET WELL PUMP INSTALLATIONS
8.2 BELLMOUTH DIMENSIONS FOR VERTICAL INTAKES
8.3 MAXIMUM SPACING BETWEEN SHAFT GUIDE BUSHING
8.4 LINE SHAFT COUPLING
9 TYPICAL VOLUTE CASING
10 TYPICAL CASE WEAR RINGS
11 SEAL AREA
TABLES
1 LIQUID PROPERTIES SODIUM CHLORIDE (25% W/W)
2 LIQUID PROPERTIES SODIUM CHLORIDE (20% W/W)
3 LIQUID PROPERTIES SODIUM CHLORIDE (16.25% W/W)
4 LIQUID PROPERTIES SODIUM CHLORIDE (15% W/W)
5 LIQUID PROPERTIES SODIUM CHLORIDE (10% W/W)
6 LIQUID PROPERTIES SODIUM CHLORIDE (5% W/W)
7 GUIDE TO PUMP TYPE AND SPEED
8 RECOMMENDED CAST MATERIALS FOR USE IN THE PUMP INDUSTRY
GRAPHS
1 GUIDE TO ROTOR INERTIA
2 LIMITS BETWEEN BEARINGS
DOCUMENTS REFERRED TO IN THIS ENGINEERING DEPARTMENT DESIGN GUIDE
Gas Mixing
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 RECOMMENDATIONS FOR GAS MIXING:
PLUG FLOW
5 RECOMMENDATIONS FOR GAS MIXING:
BACKMIXED INITIAL ZONE
6 BIBLIOGRAPHY
Hydrogen Compressors
Engineering Design Guide
1 SCOPE
2 PHYSICAL ROPERTIES
2.1 Data for Pure Hydrogen
2.2 Influence of Impurities
3 MATERIALS OF CONSTRUCTION
3.1 Hydrogen from Electrolytic Cells
3.2 Pure Hydrogen
4 DESIGN
4.1 Pulsation
4.2 Bypass
5 TESTING OR COMMISSIONING RECIPROCATING COMPRESSORS
6 LUBRICATION
7 LAYOUT
8 REFERENCES
FIGURES
1 MOLLIER CHART - HYDROGEN
2 COMPRESSIBILITY CHART
3 NELSON DIAGRAM
4 WATER CONTENT IN HYDROGEN FOR OIL-LUBRICATED COMPRESSORS AS GRAMM/M2 SWEPT CYLINDER AREA
Troubleshooting in Distillation Columns
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 FLOW DIAGRAM FOR TROUBLESHOOTING
5 GENERAL APPRAISAL OF PROBLEM
5.1 Is the Problem Real?
5.2 What Is the Magnitude of the Problem?
5.3 Is it the Column or the Associated Equipment which is Causing the Problem?
6 PROBLEMS IN THE COLUMN
6.1 Capacity Problems
6.2 Efficiency Problems
7 PROBLEMS OUTSIDE THE COLUMN
7.1 Effect of Other Units on Column Performance
7.2 Column Control System
7.3 Improper Operating Conditions
7.4 Auxiliary Equipment
8 USEFUL BACKGROUND READING
9 BIBLIOGRAPHY
FIGURES
1 FLOW DIAGRAM FOR TROUBLESHOOTING
2 DETERMINATION OF COLUMN CAPACITY
Application of Process to Management of Change and ModificationsGerard B. Hawkins
Application of Process to Management of Change and Modifications
Hazard Study Process: GBHE-PGP-006
CONTENTS
1.0 PURPOSE
1.1 THE NEED FOR MODIFICATIONS
1.2 GENERAL DESCRIPTION OF A MODIFICATION
1.3 PRINCIPLES TO BE FOLLOWED
1.4 REPLACEMENT OF ’LIKE WITH LIKE’
1.5 REMOTE / SMALLER SITES
1.6 GENERAL GUIDANCE TO INDIVIDUALS DOING SHE ASSESSMENTS FOR MODIFICATIONS
1.7 MODIFICATIONS HAZARD STUDY DECISION MECHANISM
1.7.1 Purpose
1.7.2 Methodology
FIGURE 1 MODIFICATION FLOWCHART
M1 Title, description, registration and process flowsheet
Gate 1 Preliminary authorization
Table 1 Difference between a Modification and a Project
M2 Risk Assessment
Gate 2 Approval
M3 Detailed design and implementation
Gate 3 Pre-Commissioning check
M4 Commissioning
Gate 4 Commissioned
M5 Final review and file
APPENDIX
APPENDIX A CHECKLIST FOR MODIFICATIONS
APPENDIX B DOCUMENTATION PROMPT LIST
APPENDIX C TYPICAL MODIFICATION FORM
G1 PRELIMINARY AUTHORIZATION
M2 PRELIMINARY SSHE ASSESSMENT
G2 REVIEW PRELIMINARY SSHE ASSESSMENT
M3 DESIGN and ESTIMATION
SSHE ASSESSMENT
G3 APPROVAL
M4 DETAILED DESIGN AND IMPLEMENTATION
G4 PRE-COMMISSIONING CHECK
M5 COMMISSIONING
G5 COMMISSIONED
M6 FINAL REVIEW AND FILE
Heating and Cooling of Batch Processes
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
3.1 units
4 STATEMENT OF THE PROBLEM
5 DEVELOPMENT OF THE METHOD
5.1 Assumptions
5.2 Basic Equations
6 APPLICATION OF THE METHOD
6.1 Determining the Behavior of an Existing System
6.2 Specifying the Heat Transfer Duty for a New System
APPENDICES
A DERIVATION OF THE EQUATIONS
B WORKED EXAMPLES
FIGURES
1 CASES CONSIDERED
Integration of Special Purpose Centrifugal Fans into a ProcessGerard B. Hawkins
Integration of Special Purpose Centrifugal Fans into a Process
0 INTRODUCTION
1 SCOPE
2 NOTATION
3 PRELIMINARY CHOICE OF NUMBER OF FANS
3.1 Volume Flow Q o
3.2 Definitions
3.3 Estimate of Equivalent Pressure Rise Δ P e
3.4 Choice of Fan Type
3.5 Choice of Control Method
4 GAS DENSITY CONSIDERATIONS
4.1 Calculation of Inlet Pressure
4.2 Calculation of Gas Density
4.3 Atmospheric Air Conditions
5 CAPACITY AND PRESSURE RISE RATING
5.1 Calculation of Fan Capacity
5.2 Calculation of Fan Pressure Rise
5.3 Multiple Duty Points
5.4 Stability
5.5 Parallel Operation
6 GUIDE TO FAN SELECTION
6.1 Effect of Gas Contaminants
6.2 Selection of Blade Type
6.3 Selection of Rotational Speed
6.4 Wind milling and Slowroll
6.5 Estimate of Fan External Dimensions
7 POWER RATING
7.1 Estimate of Fan Efficiency
7.2 Calculation of Absorbed Power
7.3 Calculation of Driver Power Rating
7.4 Motor Power Ratings
7.5 Starting Conditions for Electric Motors
8 CASING PRESSURE RATING
8.1 Calculation of Maximum Inlet Pressure ΔP i max
8.2 Calculation of Maximum Pressure Rise Δ P s max
8.3 Calculation of Casing Test Pressure
8.4 Rating for Explosion
9 NOISE RATING
9.1 Estimate of Fan Sound Power Rating LR
9.2 Acceptable Sound Power Level LW
9.3 Acceptable Sound Pressure Level L p
9.4 Assessment of Silencing Requirements
APPENDICES
A RELIABILITY CLASSIFICATION
B FAN LAWS
FIGURES
3.4 GUIDE TO FAN TYPE
4.5 VARIATION OF AIR DENSITY WITH TEMPERATURE AND ALTITUDE
6.3.1 DUTY BOUNDARY FOR SINGLE - INLET IMPELLERS
6.3.3 RELATIONSHIP BETWEEN HEAD COEFFICIENT AND SPECIFIC SIZE
6.3.6 ROTATIONAL SPEEDS FOR FAN IMPELLERS WITH BACK SWEPT VANES
6.3.7 ROTATIONAL SPEED FOR FAN IMPELLERS WITH RADIAL VANES
6.3.8 RELATIONSHIP OF IMPELLER TIP SPEED TO SHAPE
6.3.9 BOUNDARY DEFINING ARDUOUS DUTY
7.1 NOMOGRAPH FOR ESTIMATING THE EFFICIENCY OF A SINGLE STAGE FAN
7.2 GRAPH: COEFFICIENT OF COMPRESSIBILITY vs PRESSURE RATIO
7.5 GRAPH: MOMENT OF INERTIA OF FAN AND MOTOR (wR2) vs kW
SMR PRE-REFORMER DESIGN
Case Study #0618416GB/H
Contents
1. SMR Pre-Reformer Design
2. Inlet Baffle Design
3. Outlet Collector
4. Hold Down Grating
5. Floating Hold Down Screen
6. Catalyst Drop Out Nozzle
7. Thermowell Detail
8. Technical Performance requirements
9. SMR Pre-Reformer Isolation
Technical Review and Commentary on Proposed Design
APPENDIX
A. Operating / Mechanical Data
B. Materials Specifications
C. Fabrication and Inspection Requirements
D. Weights
E. Nozzle Data
F. Instrument Connections
G. Manholes
Distillation Sequences, Complex Columns and Heat IntegrationGerard B. Hawkins
Distillation Sequences, Complex Columns and Heat Integration
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 SEQUENCING OF SIMPLE COLUMNS
4.1 Sidestream Columns
4.2 Multi-Feed Columns
5 SIMPLE COLUMN SEQUENCING AND HEAT
INTEGRATION INTERACTIONS
5.1 Energy Quantity and Quality
5.2 Heat Integration within the Total Flowsheet
6 COMPLEX COLUMN ARRANGEMENTS
6.1 Indirect Sequence with Vapor Link
6.2 Sidestream Systems
6.3 Pre-Fractionator Systems
7 COMPLEX COLUMNS AND HEAT INTEGRATION
INTERACTIONS
FIGURES
1 DIRECT AND INDIRECT SEQUENCES
2 A SINGLE SIDESTREAM COLUMN REPLACING 2
SIMPLE COLUMNS
3 A TYPICAL MULTI-FEED COLUMN
4 TYPICAL GRAND COMPOSITION CURVE
5 TYPICAL INDIRECT SEQUENCE WITH VAPOUR LINK
6 SIDESTREAM STRIPPER AND SIDESTREAM
RECTIFIER
7 SIMPLEST PRE-FRACTIONATOR SYSTEM
8 SIMPLEST PRE-FRACTIONATOR SYSTEM
9 PETLYUK COLUMN
Integration of Special Purpose Centrifugal Pumps into a ProcessGerard B. Hawkins
Integration of Special Purpose Centrifugal Pumps into a Process
CONTENTS
1 SCOPE
2 PRELIMINARY CHOICE OF PUMP
SECTION A - INLET CONDITIONS
Al Calculation of Basic Nett Positive Suction Head (NPSH)
A2 Correction to Basic NPSH for Temperature Rise at Pump Inlet
A3 Correction to Basic NPSH for Acceleration Head
A4 Calculation of Available NPSH
A5 Correction to NPSH for Fluid Properties
A6 Calculation of Suction Specific Speed
A7 Priming
A8 Submergence
SECTION B – FLOW / HEAD RATING SEQUENCE
B1 Calculation of Static Head
B2 Calculation of Margins for Control
B3 Calculation of Q-H Duty
B4 Stability and Parallel Operation
B5 Corrections to Q-H Duty for Fluid Properties
B6 Guide to Pump Type and Speed
SECTION C – DRIVER POWER RATING
C1 Estimation of Pump Efficiency
C2 Calculation of Absorbed Power
C3 Calculation of Driver Power Rating
C4 Preliminary Power Ratings of Electric Motors
C5 Starting Conditions for Electric Motors
C6 Reverse Flow and Reverse Rotation
SECTION D - CASING PRESSURE RATING
D1 Calculation of Maximum Inlet Pressure
D2 Calculation of Differential Pressure
D3 Pressure Waves
D4 Pressure due to Liquid Thermal Expansion
D5 Casing Hydrostatic Test Pressure
SECTION E – SEALING CONSIDERATIONS
E1 Preliminary Choice of Seal
E2 Fluid Attributes
E3 Definition of Flushing Arrangements
APPENDICES
A RELIABILITY CLASSIFICATION
B SYMBOLS AND PREFERRED UNITS
DOCUMENTS REFERRED TO IN THIS ENGINEERING DESIGN GUIDE
Similar to Thermal Design Margins for Heat Exchangers (20)
Pressure Relief Systems Vol 2
Causes of Relief Situations
This Volume 2 is a guide to the qualitative identification of common causes of overpressure in process equipment. It cannot be exhaustive; the process engineer and relief systems team should look for any credible situation in addition to those given in this Part which could lead to a need for pressure relief (a relief situation).
This document provides guidelines for engineering design of pressure relief systems. It discusses key principles such as identifying potential overpressure and underpressure causes, sizing relief systems to prevent hazards, and safely disposing of relieved materials. The guidelines cover statutory requirements, recommended design procedures, and documentation standards. The overall goal is to preserve equipment integrity and prevent failure from over or under pressure during all process phases.
GAS DISPERSION - A Definitive Guide to Accidental Releases of Heavy GasesGerard B. Hawkins
GAS DISPERSION - A Definitive Guide to Accidental Releases of Heavy Gases
This Process Safety Guide has been written with the aim of assisting process engineers, hazard analysts and environmental advisers in carrying out gas dispersion calculations. The Guide aims to provide assistance by:
• Improving awareness of the range of dispersion models available within GBHE, and providing guidance in choosing the most appropriate model for a particular application.
• Providing guidance to ensure that source terms and other model inputs are correctly specified, and the models are used within their range of applicability.
• Providing guidance to deal with particular topics in gas dispersion such as dense gas dispersion, complex terrain, and modeling the chemistry of oxides of nitrogen.
• Providing general background on air quality and dispersion modeling issues such as meteorology and air quality standards.
• Providing example calculations for real practical problems.
SCOPE
The gas dispersion guide contains the following Parts:
1 Fundamentals of meteorology.
2 Overview of air quality standards.
3 Comparison between different air quality models.
4 Designing a stack.
5 Dense gas dispersion.
6 Calculation of source terms.
7 Building wake effects.
8 Overview of the chemistry of the oxides of nitrogen.
9 Overview of the ADMS complex terrain module.
10 Overview of the ADMS deposition module.
11 ADMS examples.
12 Modeling odorous releases.
13 Bibliography of useful gas dispersion books and reports.
14 Glossary of gas dispersion modeling terms.
Appendix A : Modeling Wind Generation of Particulates.
APPENDIX B TABLE OF PROPERTY VALUES FOR SPECIFIC CHEMICALS
El impacto en el rendimiento del catalizador por envenenamiento y ensuciamien...Gerard B. Hawkins
El documento describe los procesos de refinería y catalizadores, así como los efectos del envenenamiento y ensuciamiento en el rendimiento de los catalizadores. El envenenamiento reduce la actividad de los catalizadores al bloquear los sitios activos o modificar la química de la superficie, lo que afecta la actividad y selectividad. Los niveles bajos de contaminantes tienen un mayor impacto en catalizadores con menor área de superficie. El envenenamiento también puede causar cambios estructurales en el catalizador y permitir
Theory of Carbon Formation in Steam Reforming
Contents
1 Introduction
2 Underpinning Theory
2.1 Conceptualization
2.2 Reforming Reactions
2.3 Carbon Formation Chemistry
2.3.1 Natural Gas
2.3.2 Carbon Formation for Naphtha Feeds
2.3.3 Carbon Gasification
2.4 Heat Transfer
3 Causes
3.1 Effects of Carbon Formation
3.2 Types of Carbon
4 What are the Effects of Carbon Formation?
4.1 Why does Carbon Formation Get Worse?
4.1.1 So what is the Next Step?
4.2 Consequences of Carbon Formation
4.3 Why does Carbon Form where it does?
4.3.1 Effect on Process Gas Temperature
4.4 Why does Carbon Formation Propagate Down the Tube?
4.4.1 Effect on Radiation on the Fluegas Side
4.5 Why does Carbon Formation propagate Up the Tube?
5 How do we Prevent Carbon Formation
5.1 The Role of Potash
5.2 Inclusion of Pre-reformer
5.3 Primary Reformer Catalyst Parameters
5.3.1 Activity
5.3.2 Heat Transfer
5.3.3 Increased Steam to Carbon Ratio
6 Steam Out
6.1 Why does increasing the Steam to Carbon Ratio Not Work?
6.2 Why does reducing the Feed Rate not help?
6.3 Fundamental Principles of Steam Outs
TABLES
1 Heat Transfer Coefficients in a Typical Reformer
2 Typical Catalyst Loading Options
FIGURES
1 Hot Bands
2 Conceptual Pellet
3 Naphtha Carbon Formation
4 Heat Transfer within an Reformer
5 Types of Carbon Formation
6 Effect of Carbon on Nickel Crystallites
7 Absorption of Heat
8 Comparison of "Base Case" v Carbon Forming Tube
9 Carbon Formation Vicious Circle
10 Temperature Profiles
11 Carbon Pinch Point
12 Carbon Formation
13 Effect on Process Gas Temperature
14 How does Carbon Propagate into an Unaffected Zone?
15 Movement of the Carbon Forming Region
16 Effect of Hot Bands on Radiative Heat Transfer
17 Effect of Potash on Carbon Formation
18 Application of a Pre-reformer
19 Effect of Activity on Carbon Formation
Adiabatic Reactor Analysis for Methanol Synthesis Plant Note Book Series: P...Gerard B. Hawkins
The document discusses adiabatic reactor analysis for methanol synthesis from syngas. It provides the reaction kinetics and calculates conversion, temperature, and reactor volume needed at different conversions. Energy and mass balances are used to derive relationships between conversion, temperature and reaction rate. Data is generated to plot conversion versus volumetric flow rate for reactor sizing. The plot indicates a continuous stirred tank reactor (CSTR) could achieve 85% conversion before switching to a plug flow reactor (PFR) for higher conversion with less volume.
STEAMING PROCEDURE FOR VULCAN STEAM REFORMING CATALYSTSGerard B. Hawkins
The document discusses procedures for steaming Vulcan steam reforming catalysts to recover from sulfur poisoning and carbon formation incidents. It describes maintaining steam flow at 30-40% of design levels and an outlet temperature above 780°C. Gas samples should be taken hourly to monitor CO2, CH4, H2S and SO2. Steaming is complete when CO2 levels stabilize over 2-3 samples after increasing the temperature. The process typically takes 12-24 hours to complete and closely monitors pressure drop and tube conditions. After steaming, the catalyst requires reduction before restarting hydrocarbon feed.
Calculation of an Ammonia Plant Energy Consumption: Gerard B. Hawkins
Calculation of an Ammonia Plant Energy Consumption:
Case Study: #06023300
Plant Note Book Series: PNBS-0602
CONTENTS
0 SCOPE
1 CALCULATION OF NATURAL GAS PROCESS FEED CONSUMPTION
2 CALCULATION OF NATURAL GAS PROCESS FUEL CONSUMPTION
3 CALCULATION OF NATURAL GAS CONSUMPTION FOR PILOT BURNERS OF FLARES
4 CALCULATION OF DEMIN. WATER FROM DEMIN. UNIT
5 CALCULATION OF DEMIN. WATER TO PACKAGE BOILERS
6 CALCULATION OF MP STEAM EXPORT
7 CALCULATION OF LP STEAM IMPORT
8 DETERMINATION OF ELECTRIC POWER CONSUMPTION
9 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT ISBL
10 ADJUSTMENT OF ELECTRIC POWER CONSUMPTION FOR TEST RUN CONDITIONS
11 CALCULATION OF AMMONIA SHARE IN MP STEAM CONSUMPTION IN UTILITIES
12 CALCULATION OF AMMONIA SHARE IN ELECTRIC POWER CONSUMPTION IN UTILITIES
13 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT OSBL
14 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT
Ammonia Plant Technology
Pre-Commissioning Best Practices
GBHE-APT-0102
PICKLING & PASSIVATION
CONTENTS
1 PURPOSE OF THE WORK
2 CHEMICAL CONCEPT
3 TECHNICAL CONCEPT
4 WASTES & SAFETY CONCEPT
5 TARGET RESULTS
6 THE GENERAL CLEANING SEQUENCE MANAGEMENT
6.6.1 Pre-cleaning or “Physical Cleaning
6.6.2 Pre-rinsing
6.6.3 Chemical Cleaning
6.6.4 Critical Factors in Cleaning Success
6.6.5 Rinsing
6.6.6 Inspection and Re-Cleaning, if Necessary
7 Systems to be treated by Pickling/Passivation
Ammonia Plant Technology
Pre-Commissioning Best Practices
Piping and Vessels Flushing and Cleaning Procedure
CONTENTS
1 Scope
2 Aim/purpose
3 Responsibilities
4 Procedure
4.1 Main cleaning methods
4.1.1 Mechanical cleaning
4.1.2 Cleaning with air
4.1.3 Cleaning with steam (for steam networks only)
4.1.4 Cleaning with water
4.2 Choice of the cleaning method
4.3 Cleaning preparation
4.4 Protection of the devices included in the network
4.5 Protection of devices in the vicinity of the network
4.6 Water flushing procedure
4.6.1 Specific problems of water flushing
4.6.2 Preparation for water flushing
4.6.3 Performing a water flush
4.6.4 Cleanliness criteria
4.7 Air blowing procedure
4.7.1 Specific problems of air blowing
4.7.2 Preparation for air blowing
4.7.3 Performing air blowing
4.7.4 Cleanliness checks
4.8 Steam blowing procedure
4.8.1 Specific problems of steam blowing
4.8.2 Preparation for steam blowing
4.8.3 Performing steam blowing
4.8.4 Cleanliness checks
4.9 Chemical cleaning procedure
4.9.1 Specific problems of cleaning with a chemical solution
4.9.2 Preparation for chemical cleaning
4.9.3 Performing a chemical cleaning
4.9.4 Cleanliness criteria
4.10 Re-assembly - general guideline
4.11 Preservation of flushed piping
PRACTICAL GUIDE ON THE SELECTION OF PROCESS TECHNOLOGY FOR THE TREATMENT OF A...Gerard B. Hawkins
PRACTICAL GUIDE ON THE SELECTION OF PROCESS TECHNOLOGY FOR THE TREATMENT OF AQUEOUS ORGANIC EFFLUENT STREAMS
CONTENTS
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
3.1 IPU
3.2 AOS
3.3 BODs
3.4 COD
3.5 TOC
3.6 Toxicity
3.7 Refractory Organics/Hard COD
3.8 Heavy Metals
3.9 EA
3.10 Biological Treatment Terms
3.11 BATNEEC
3.12 BPEO
3.13 EQS/LV
3.14 IPC
3.15 VOC
3.16 F/M Ratio
3.17 MLSS
3.18 MLVSS
4 DESIGN/ECONOMIC GUIDELINES
5 EUROPEAN LEGISLATION
5.1 General
5.2 Integrated Pollution Control (IPC)
5.3 Best Available Techniques Not Entailing Excessive Costs (BATNEEC)
5.4 Best Practicable Environmental Option (BPEO)
5.5 Environmental Quality Standards(EQS)
6 IPU EXIT CONCENTRATION
7 SITE/LOCAL REQUIREMENTS
8 PROCESS SELECTION PROCEDURE
8.1 Waste Minimization Techniques (WMT)
8.2 AOS Stream Definition
8.3 Technical Check List
8.4 Preliminary Selection of Suitable Technologies
8.5 Process Sequences
8.6 Economic Evaluation
8.7 Process Selection
APPENDICES
A DIRECTIVE 76/464/EEC - LIST 1
B DIRECTIVE 76/464/EEC - LIST 2
C THE EUROPEAN COMMISSION PRIORITY CANDIDATE LIST
D THE UK RED LIST
E CURRENT VALUES FOR EUROPEAN COMMUNITY ENVIRONMENTAL QUALITY STANDARDS AND CORRESPONDING LIMIT VALUES
F ESTABLISHED TECHNOLOGIES
G EMERGING TECHNOLOGY
H PROPRIETARY/LESS COMMON TECHNOLOGIES
J COMPARATIVE COST DATA
PRACTICAL GUIDE ON THE REDUCTION OF DISCHARGES TO ATMOSPHERE OF VOLATILE ORGA...Gerard B. Hawkins
PRACTICAL GUIDE ON THE REDUCTION OF DISCHARGES TO ATMOSPHERE OF VOLATILE ORGANIC COMPOUNDS (VOCs)
FOREWORD
CONTENTS
1 INTRODUCTION
2 THE NEED FOR VOC CONTROL
3 CONTROL AT SOURCE
3.1 Choice or Solvent
3.2 Venting Arrangements
3.3 Nitrogen Blanketing
3.4 Pump Versus Pneumatic Transfer
3.5 Batch Charging
3.6 Reduction of Volumetric Flow
3.7 Stock Tank Design
4 DISCHARGE MEASUREMENT
4.1 By Inference or Calculation
4.2 Flow Monitoring Equipment
4.3 Analytical Instruments
4.4 Vent Emissions Database
5 ABATEMENT TECHNOLOGY
5.1 Available Options
5.2 Selection of Preferred Option
5.3 Condensation
5.4 Adsorption
5.5 Absorption
5.6 Thermal Incineration
5.7 Catalytic Oxidation
5.8 Biological Filtration
5.9 Combinations of Process technologies
5.10 Processes Under Development
6 GLOSSARY OF TERMS
7 REFERENCES
Appendix 1. Photochemical Ozone Creation Potentials
Appendix 2. Examples of Adsorption Preliminary Calculations
Appendix 3. Example of Thermal Incineration Heat and Mass Balance
Appendix 4. Cost Correlations
EMERGENCY ISOLATION OF CHEMICAL PLANTS
CONTENTS
1 Introduction
2 When should Emergency Isolation Valves be Installed
3 Emergency Isolation Valves and Associated Equipment
3.1 Installations on existing plant
3.2 Actuators
3.3 Power to close or power to open
3.4 The need for testing
3.5 Hand operated Emergency Valves
3.6 The need to stop pumps in an emergency
3.7 Location of Operating Buttons
3.8 Use of control valves for Isolation
4 Detection of Leaks and Fires
5 Precautions during Maintenance
6 Training Operators to use Emergency Isolation Valves
7 Emergency Isolation when no remotely operated valve is available
References
Glossary
Appendix I Some Fires or Serious Escapes of Flammable Gases or Liquids that could have been controlled by Emergency Isolation Valves
Appendix II Some typical Installations
Investigation of the Potential Use of (IILs) Immobilized Ionic Liquids in Sha...Gerard B. Hawkins
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1. GBH Enterprises, Ltd.
Process Engineering Guide:
GBHE-PEG-HEA-504
Thermal Design Margins for Heat
Exchangers
Information contained in this publication or as otherwise supplied to Users is
believed to be accurate and correct at time of going to press, and is given in
good faith, but it is for the User to satisfy itself of the suitability of the information
for its own particular purpose. GBHE gives no warranty as to the fitness of this
information for any particular purpose and any implied warranty or condition
(statutory or otherwise) is excluded except to the extent that exclusion is
prevented by law. GBHE accepts no liability resulting from reliance on this
information. Freedom under Patent, Copyright and Designs cannot be assumed.
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Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass
Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance
Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts /
Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals
Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries
Web Site: www.GBHEnterprises.com
2. Process Engineering Guide:
Thermal Design Margins for
Heat Exchangers
CONTENTS
SECTION
0
INTRODUCTION/PURPOSE
3
1
SCOPE
3
2
FIELD OF APPLICATION
3
3
DEFINITIONS
3
4
TERMINOLOGY
3
5
REASONS FOR SPECIFYING A DESIGN MARGIN
3
5.1
5.2
5.3
5.4
5.5
5.6
5.7
Instantaneous Rates
Future Uprating
Plant Upsets
Process Control
Uncertainties in Properties
Uncertainties in Design Methods
Fouling
4
4
4
4
4
4
4
6
COMBINATION OF DESIGN MARGINS
5
7
CRITICAL AND NON-CRITICAL DUTIES
5
7.1
7.2
General
Penalties of Over-design
5
6
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Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts /
Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals
Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries
Web Site: www.GBHEnterprises.com
3. 8
OPTIMIZATION OF EXCHANGER DUTY
6
9
WAYS OF PROVIDING DESIGN MARGINS
6
9.1
9.2
9.3
9.4
9.5
The Provision of Excess Surface
Decreasing the Design Temperature Difference
Increasing the Design Process Throughput
Increasing the Design Fouling Resistance
Reducing the Design Process Outlet Temperature
Approach
Adjusting the Physical Properties
7
7
7
8
9.6
10
ACCURACY OF THE DESIGN METHODS FOR
SHELL AND TUBE EXCHANGERS
8
8
8
10.1
10.2
Pressure Drop
Heat Transfer
8
9
11
SUGGESTED DESIGN MARGINS
10
11.1
11.2
11.3
No Phase Change Duties
Condensers
Boilers
10
10
10
12
EFFECT OF UNDER- OR OVER-SURFACE ON
PERFORMANCE
10
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4. FIGURES
(1)
2
3
EFFECT OF LENGTH ON EXCHANGER DUTY
COUNTERCURRENT FLOW, C* = 1.0
12
EFFECT OF NUMBER OF TUBES ON EXCHANGER
PERFORMANCE COUNTERCURRENT FLOW,
C* = 1.0, ALL RESISTANCE IN TUBES
13
EFFECT OF TUBE LENGTH ON NUMBER OF TUBES,
AREA AND PRESSURE DROP
14
DOCUMENTS REFERRED TO IN THIS PROCESS
ENGINEERING GUIDE
15
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Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals
Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries
Web Site: www.GBHEnterprises.com
5. 0
INTRODUCTION/PURPOSE
This document is one of a series on heat transfer prepared for GBH Enterprises.
When designing a heat exchanger it is usual to include some form of over-design
or "safety factor" to allow for uncertainties in the design process. This can be
done in many different ways, which have advantages and drawbacks. Unless the
specifying engineer is aware of the implications of the chosen method, the
effective safety margin may be different from the intention.
1
SCOPE
This Guide explains the reasons for including a design margin, discusses the
various ways in which one can be provided and comments on the relative merits
of the different ways. It also gives some information on the accuracy of heat
exchanger designs with special reference to shell and tube heat exchangers.
2
FIELD OF APPLICATION
This Guide applies to process engineers in GBH Enterprises worldwide, who
may be involved in the specification, design or rating of heat transfer equipment.
3
DEFINITIONS
For the purposes of this Process Engineering Guide, the following definitions
apply:
HTRI
Heat Transfer Research Incorporated. See GBHE-PEG-HEA-502.
HTFS
Heat Transfer and Fluid Flow Service. One of the suppliers of
thermal design software. See GBHE-PEG-HEA-502.
With the exception of terms used as proper nouns or titles, those terms with initial
capital letters which appear in this document and are not defined above are
defined in the Glossary of Engineering Terms.
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6. 4
TERMINOLOGY
Several alternative terms are commonly used to describe the "design margin", for
example "safety factor", "% excess surface", "% over-design", "actual to required
area ratio".
5
REASONS FOR SPECIFYING A DESIGN MARGIN
An item of equipment may be designed to be larger than that needed to meet the
average design throughput of the plant at design conditions for several reasons.
The following list has been produced with heat exchangers in mind, but much of
it is equally applicable to other items of equipment.
5.1
Instantaneous Rates
The section of plant may be required to run at instantaneous rates above the
normal plant throughput as part of the normal plant operation to allow for different
availabilities of different sections of the plant. Designing for this condition does
not represent a true design margin, as the higher rate represents a normal
condition.
5.2
Future Uprating
The engineer may wish to make provision for future plant uprating. If it is
probable that the plant will be uprated at some future date, there may be a case
for increasing the design throughput, with a corresponding increase in heat load.
However, the heat transfer coefficient under the initial operating conditions will be
lower than the design figure because of the lower velocities; the performance
under the initial operating conditions should be checked to determine the
expected safety margin at the initial conditions. Again, this does not represent a
true design margin, as after the uprating there will be no margin left.
Rather than installing the larger size unit initially, it may be preferable to make
provision for increasing the size of the exchanger at some later date, either by
replacing it with a larger unit, by adding an additional exchanger in parallel with
the original one or by adding heat transfer enhancement devices.
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7. 5.3
Plant Upsets
Variations in the inlet flowrates, temperatures or compositions of the feeds to the
exchanger, due to disturbances in other parts of the plant, may require a duty
above the nominal design. Although ideally such disturbances should be
identified at the time when the duty was specified, and the worst case taken for
design, it may be desirable to include an additional margin to allow for
unforeseen disturbances.
5.4
Process Control
The duty required from an exchanger may need to be above the steady state
value in order to provide some control function for another piece of equipment.
5.5
Uncertainties in Properties
Many heat exchangers are required to handle a complex mix of compounds
where the physical properties of the mixture may be uncertain. This can result in
errors in the required heat duty, the estimated heat transfer coefficients or the
temperature driving force (by affecting the dew point of a condensing stream, for
example).
5.6
Uncertainties in Design Methods
In spite of improvements made over many years, there are still uncertainties in
the predictive methods for heat transfer, especially for processes involving a
phase change. It is generally advisable for a critical duty to provide some form of
safety margin to allow for uncertainties in the design methods.
5.7
Fouling
It is normal when specifying a heat exchanger duty to include the expected
fouling resistances. The prediction of such resistances is not a precise science,
often being more of a guess. As such, the fouling resistance may be considered
itself to be a safety margin over the predicted clean performance, to allow for the
(unpredictable) variation in fouling. However, it is normal to include an additional
margin above that represented by the assumed fouling resistance. The
extra pressure drop due to the fouling layer thickness should not be forgotten.
See sub clause10.1.
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8. 6
COMBINATION OF DESIGN MARGINS
Beware of over specifying design margins. During the course of a plant design,
several stages occur between the overall concept and detailed equipment
design. These might include:
(a)
Preparation of overall flowsheet.
(b)
Preparation of section flowsheet.
(c)
Specification of equipment duty.
(d)
Detailed equipment design.
Each of these stages may be the responsibility of a different engineer. If each
engineer adds his/her own design margin at each stage, the final item design
may be considerably oversized for the duty. If the instantaneous section
throughput has been increased to compensate for periods when the flowsheet
rate cannot be achieved, it is unreasonable to design an air cooled exchanger for
an ambient temperature which is exceeded for only a few hours each year.
Frequently, there may be more than one type of uncertainty associated with the
design of a heat exchanger, each of which might justify the inclusion of a design
margin. For example, there may be uncertainties in fouling resistance, physical
properties and ambient conditions. If the standard deviations for each area on
uncertainty are d1, d2, d3, .... then the overall uncertainty of design will have a
standard deviation of d0 where:
This is equivalent to saying that the combined margin for design M0 should be
given by:
where M1, M2, M3 are the margins which would be applied for the uncertainties
considered in isolation, expressed as fractional excess areas. This resulting
margin will be less than that obtained by a straight summation of the individual
margins. In particular, if the margin due to one particular factor is large compared
with the others, then the other margins will be largely irrelevant.
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9. (Strictly speaking, the above approach is only correct if the uncertainties follow a
normal distribution, but it will be reasonable even if they do not).
7
CRITICAL AND NON-CRITICAL DUTIES
7.1
General
Critical exchangers can be defined as:
(a)
Exchangers which, if they failed to perform as required, would have a
significant effect on plant safety; for example, the inability to control a
potential runaway reaction.
(b)
Exchangers which directly affect the plant production rate. Typical
examples are distillation column reboilers and condensers, some feed
heaters and run-down coolers and some fired heaters.
Other exchangers will be "non-critical", if they do not perform as required then
plant efficiency may be reduced and running costs increased with very little effect
on plant production. Examples of these are compressor suction and interstage
coolers, chillers, vacuum and refrigeration condensers and most interchangers.
The distinction between "critical" and "non-critical" duties in some cases may be
somewhat arbitrary. Ultimately, a trade-off needs to be made in some way
between the cost of the exchanger and the consequences of under-design.
.Whereas the provision of a suitable design margin for a critical duty may be
necessary, this is not true for non-critical duties. In general, no margin should be
provided for non-critical duties.
7.2
Penalties of Over-design
Design margins are provided to compensate for uncertainties which could reduce the
calculated performance. However, these uncertainties could be unfounded, or even act
to improve performance, resulting in an oversized exchanger for the duty. In most cases,
the only penalty associated with an oversized exchanger is the extra capital cost.
However, there may be cases where an oversized exchanger can have positively
harmful effects.
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10. If the oversized unit is part of an exchanger network, its over-performance could result in
problems with other exchangers in the network. It may be possible to overcome this by
the provision of suitable control schemes, such as bypassing of some of the fluid round
the unit, but this could result in other problems, such as excessive fouling. In the
extreme, it may require the installation of additional trim heaters or coolers, thus
detracting from the benefits of the network.
Thermosyphon boilers can present particular problems. The turndown ratio of such units
is limited; typically a 3:1 turndown is the most that can be achieved without running into
problems with stability or total failure to circulate. The performance and stability of such
units is influenced not only by the installed area but by also by the design of the
circulation pipework and the distribution of pressure drop around the circuit. For steam
heated boilers, it may also be necessary to run with sub-atmospheric steam to achieve
turn-down conditions with an oversized boiler. This can lead to problems of condensate
removal. It is imperative that the designer carry out performance runs for the design for
the complete operating range under both clean and fouled conditions. For more
information on vertical thermosyphon boilers, see GBHE-PEG-HEA-515
8
OPTIMIZATION OF EXCHANGER DUTY
So far, it has been assumed that the required duty of the exchanger is fixed, and
the margin is required to ensure that this duty can be met. The exchanger
designer will then try to produce the "best" design which meets the duty within
the constraints, with some agreed margin.
However, in many cases, the duties of specific exchangers within the process are
not fixed a priori. The duty of these exchangers should be optimized by the
correct trade-off between capital and running costs, possibly with the assistance
of heat exchanger network design methods. Discussion of these methods is
beyond the scope of this guide.
Many such exchangers can be classified as "non-critical". For these, designs
based on normal fouling resistances without additional margins should be
considered.
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11. 9
WAYS OF PROVIDING DESIGN MARGINS
A thermal design margin (safety factor) may be provided in several different
ways, which have their own advantages and disadvantages. It is important that
the engineer understands the implications of these. The engineer should be wary
of disclosing design margins to a supplier who is to perform the design, as the
latter may be tempted to design with negative margins in order to maintain a
competitive position, knowing that in many cases, actual performance checks
under design conditions may be difficult or impossible. Because of this, it may be
advisable to produce a separate data sheet to send to the manufacturer, on
which certain items have been removed or altered. This sheet should be
included, suitably annotated, in the plant manual, along with the correct data
sheets, so that the true situation is recorded.
9.1
The Provision of Excess Surface
Excess surface may be provided in one of two ways:
(a)
Adding extra surface in parallel:
Providing the extra surface by increasing the number of tubes or passages
per pass over that theoretically necessary is generally unsatisfactory for
cases where convective transfer is the dominant mechanism. It will result
in a more expensive unit but because of the reduced velocity, and hence
coefficient, there may be little effective increase in performance. See
Clause 12 for more information.
(b)
Adding extra surface in series:
Increasing the flowpath, by increasing the exchanger length or the number
of passes, is generally more satisfactory. This will, however, increase the
pressure drop, and it may be necessary to increase the number of
passages as well, to restore the pressure drop to the desired value. A
check on the predicted performance of the oversized exchanger will
confirm the actual pressure drop to be expected.
Note that the "area ratio" obtained when rating an exchanger, or the "percentage
over-design" obtained when rating an exchanger, is an indication of the extra
length of exchanger above that required.
It is not possible to use this approach without declaring it to the manufacturer.
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12. 9.2
Decreasing The Design Temperature Difference
Sometimes a higher air or cooling water inlet temperature is specified for critical
services than for non-critical duties. This suffers from the disadvantage that the
actual margin on performance at normal air or water temperatures will depend on
the required product temperature. A refrigerant condenser designed using this
approach might have a 25% margin; for a reactor cooler/condenser, with a higher
outlet temperature, it might be only 5%.
The specification of design ambient temperature for air cooled heat exchangers
is discussed in sub clause 3.5 of GBHE-PEG-HEA-513. It should be used to
ensure that a critical unit is designed to meet its duty on warm days, but it is not
recommended to use this parameter to control design margins at other ambient
conditions.
This approach can be useful when designing vertical thermosyphon reboilers.
Because of the coupling between heat transfer performance and circulation, the
extra length concept cannot safely be used. It is better to design the unit for
operation with a lower steam pressure, and hence condensing temperature, than
is available. A check on the predicted performance with the higher steam
pressure will give the maximum heat duty possible; the ratio of this to the
desired duty is a measure of the safety margin. However, beware that the higher
steam pressure does not result in problems such as film boiling, particularly
under clean conditions. See GBHE-PEG-HEA-515 for more details.
9.3
Increasing the Design Process Throughput
As a means of providing a design margin, this suffers from the same
disadvantage as increasing the number of tubes, namely that under normal
conditions the tubeside performance will be poorer than design, so the margin
may be less than expected.
If this approach is used, and the higher throughput is not actually likely to occur,
the allowable pressure drop supplied to the manufacturer should be increased
above the actual value by the square law, in order that he be not unduly
constrained. As the unit will end up being designed for a flowrate above that at
which the plant will run, it will not be possible to do performance checks at design
conditions.
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13. 9.4
Increasing the Design Fouling Resistance
This reduces the overall heat transfer coefficient, hence resulting in a larger
surface area being selected for the exchanger. The designer will seek to
minimize the area, within the constraints of allowable pressure drop; the film
coefficients used will not be affected by the "safety margin" as is the case for
using an increased throughput. The approach is useful when dealing with a
manufacturer, as it enables the safety margin to be hidden from him. However, it
is good practice to disclose the actual safety margins in the final documentation,
so the expected fouling resistance should be recorded in the final revisions of the
data sheets.
9.5
Reducing the Design Process Outlet Temperature Approach
In many ways this is the most satisfactory form of safety margin, and it does
allow the final unit to be checked against design conditions. However, it suffers
from the same drawback as does raising the design air or water temperature, in
that the margin will appear greater for units with a low outlet temperature.
9.6
Adjusting the Physical Properties
If there is uncertainty in the physical properties, it may be worth considering
adjusting the values used. However, some care has to be taken over how this is
done. Ideally, a sensitivity analysis ought to be performed on the effects of all
properties on the predicted performance. In practice, this is unrealistic; even
using only two values for each of the main properties for a two phase system
(latent heat, quality, specific heat, viscosity and thermal conductivity for each
phase)
As a general rule, a "safe" design will be produced if the heat load and viscosity
are overestimated and the thermal conductivity, specific heat and density are
underestimated. The percentage error in the prediction due to an error in any one
of these properties will be less than the percentage error in the property, typically
around one half. Note that for single phase cases, the specific heat and heat load
cannot be specified independently. For these cases, the "safe" design results
from overestimating the specific heat.
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14. 10
ACCURACY OF THE DESIGN METHODS FOR SHELL AND TUBE
EXCHANGERS
It was stated earlier that one of the reasons for providing a design margin was
due to uncertainty in the design methods used. This Clause gives some
indication as to the likely magnitude of such errors.
10.1 Pressure Drop
10.1.1 Tubeside Flow
For single phase flow in clean heat exchanger tubes, the estimated pressure
drop is likely to be accurate to within ±2%, assuming the physical properties are
known. The pressure drop in a fouled tube may be significantly higher, and may
not be estimated correctly by the computer programs used for exchanger design.
There are two factors resulting from fouling which are important here.
(a)
Firstly, the fouling layer reduces the effective bore of the tube. For a
smooth tube, in turbulent single phase flow, the pressure drop is
inversely proportional to the diameter raised to the power 4.75.
Thus, a dirt layer which reduces the bore by 10% will increase
the pressure drop by 65%, all other things being equal.
(b)
Secondly, the dirt layer is likely to increase the relative roughness
of the tube. The roughness of moderately rusty carbon steel is
typically 10 times that of clean steel. The effect this has on
pressure drop increases with Reynolds number. At a Reynolds
number of 10,000 it will give an increase in pressure drop of about
30-40%, at Re=100,000 about 90-100% and at Re=1,000,000
about 250%. These increases will be compounded with
those due to the reduction in bore.
Commercially available programs, allow the user to input the thickness of the
fouling layer, and use this to determine the effective tube diameter for pressure
drop calculations. However, these calculations take no account of the effect of
fouling on roughness.
Some programs make no allowance for the effect of fouling on pressure drop.
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15. The basic correlations for two phase pressure drop have considerably greater
error than is the case for single phase flow, even without considering the effects
of fouling. Errors of up to a factor of 2 in the estimated frictional pressure drop in
smooth tubes may occur. However, the effects of surface roughness are less
pronounced for two phase systems.
10.1.2 Shell-side Flow
Shell-side flow is considerably more complex than tubeside flow. The models
used in some commercially available programs are based on a method usually
known as "stream analysis". The shell-side flow is divided between five parallel
routes: tube-to-baffle leakage, cross-flow over the bundle, bypassing round the
outside of the bundle, baffle-to-shell leakage and pass-partition
lane leakage. (referred to in some programs as the "A", "B", "C", "E" and "F"
streams respectively.) The models adjust the flow split until the calculated
pressure drops for each stream are equal.
The relative magnitudes of these streams affect not only the heat transfer, but
also the pressure drop. It is not possible to give simple guidance here on the
magnitude of such effects. However, some feel for the problem can be obtained
by performing computer runs with different clearances. This simulates the
blockage of the leakage paths by fouling deposits. It is not unusual for the
predicted pressure drop to double if the baffle-to-shell and tube-to-baffle
clearances are reduced from the normal design figures to zero.
Some programs will adjust the clearances between tube and baffle to allow for
the effect of the fouling layer thickness input by the user. Some programs do not;
in order to simulate the fouled condition, the clearance has to be input. Note that
in some programs a value of zero clearance may be interpreted as a request for
the default value. If zero clearance is required, it may be necessary to input a
small number. See program manuals of the software for more detail.
10.2 Heat Transfer
10.2.1 Tube Side
For single phase turbulent flow in tubes, the ESDU correlation, has a
claimed (root mean square) error of 10.2%. Similar accuracy can be
expected from other correlations. For transitional and laminar flow, higher
errors can be expected.
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16. 10.2.2 Shell Side
As for pressure drop, heat transfer predictions for the shell side of shell
and tube exchangers are complicated by the flow distribution. Some
programs suggest an accuracy of ±25% for single phase turbulent flow.
11
SUGGESTED DESIGN MARGINS
The choice of design margin ultimately lies with the process engineer and the
designer and will be influenced by the nature of the process and the criticality of
the exchanger in question. The degree of uncertainty in the fouling resistances
should also be taken into consideration. The figures given in 11.1 to 11.3 should
be regarded only as guides.
11.1
No Phase Change Duties
For non-critical duties, a margin of 0 - 5% on the exchanger length should be
adequate, and it may be worth even considering small negative margins if this
leads to a design which fits in better with any standard tube length chosen for the
process.
For more critical duties, a value of 5-10% is appropriate.
11.2
Condensers
For pure component systems, the condensing coefficient is unlikely to be limiting;
the values given above for single phase cases will be appropriate.
For multi-component cases, values around 10% for non-critical duties and 20%
for critical duties are suggested, the margin being provided by extra tube length.
11.3
Boilers
For boilers, it is generally worth considering the design margin in terms of the
ratio of the maximum to desired evaporation capacity. For cases where the
boiling resistance is dominant, particularly for multi-component systems, a
margin of 10-20% is recommended.
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17. 12
EFFECT OF UNDER- OR OVER-SURFACE ON PERFORMANCE
An exchanger which has less than the necessary surface will have a lower heat
duty than required. However, the effect is generally not directly proportional to
the shortfall in surface; an exchanger with only 90% of the required surface will
generally perform more than 90% of the required duty.
For single phase duties it is possible to estimate the effects of over- or undersurface on exchanger performance from a theoretical analysis. The change in
heat load for a given change in surface area depends on the exchanger pass
arrangement, the ratio of the product of heat capacity and flowrate for the hot and
cold streams, C*, and the number of heat transfer units in the exchanger, NTU,
(NTU = U.A/Cmin, where U is the overall heat transfer coefficient, A is the
area and Cmin is the product of heat capacity and flowrate for the stream showing
the greater temperature change.) The NTU value is a measure of the "thermal
length" of the exchanger; duties with a large temperature overlap between the
streams have a large value of NTU.
Figure 1 shows the effect of changes in exchanger length on heat load for a pure
countercurrent exchanger with C* = 1. It can be seen that as the number of
transfer units for the base case is increased, the effect on performance of a given
fractional change in length reduces. For a duty requiring an NTU value of 5, a
50% increase in length only results in a 6% increase in duty. Conversely, an
exchanger of only the necessary length is still capable of 85% of the required
duty.
Figure 2 shows the effects on performance of changes in the number of tubes.
Again, a pure countercurrent flow is assumed, with C* = 1. For this case, all the
thermal resistance is assumed to occur on the tubeside. It can be seen that the
performance is very insensitive to the number of tubes.
Even for a very low value of NTU, a 50% increase in the number of tubes gives
only 8.5% improvement in performance, whilst for NTU=5 the improvement is
only 1.3%. This confirms what was said above, that the provision of a design
margin by adding additional surface in parallel is not a good policy.
The above analysis is based on several assumptions, including a constant heat
transfer coefficient along the exchanger and linear temperature/enthalpy
relationships. It is less easy to perform a theoretical analysis for cases involving
multi-component phase change, but experience suggests that a similar behavior
can be expected. For example, the heat transfer performance of vertical tubeside
inerts condensers is generally insensitive to the number of tubes, but does
depend significantly on tube length.
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18. FIGURE 1
EFFECT OF LENGTH ON EXCHANGER DUTY
COUNTERCURRENT FLOW, C* = 1.0
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19. FIGURE 2 EFFECT OF NUMBER OF TUBES ON EXCHANGER
PERFORMANCE COUNTERCURRENT FLOW, C* = 1.0, ALL RESISTANCE IN
TUBES
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20. FIGURE 3 EFFECT OF TUBE LENGTH ON NUMBER OF TUBES, AREA AND
PRESSURE DROP
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21. DOCUMENTS REFERRED TO IN THIS PROCESS ENGINEERING GUIDE
This Process Engineering Guide makes reference to the following documents:
GBH ENTERPRISES ENGINEERING GUIDES
Glossary of Engineering Terms
(referred to in Clause 3).
GBHE-PEG-HEA-502
Computer programs for the thermal
design of heat Exchangers (referred to
in Clause 3 and 9.1).
GBHE-PEG-HEA-515
The design and layout of vertical
thermosyphon reboilers (referred to in
9.2).
GBHE-PEG-HEA-513
Air cooled heat exchangers
(referred to in 9.2).
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