Roland Span
Ruhr-Universität Bochum, Mechanical Engineering, Faculty Member
An empirical equation of state in terms of the Helmholtz energy is presented for n-octane. It is valid from the triple-point temperature 216.37 K to 650 K with a maximum pressure of 1000 MPa and allows for the calculation of all... more
An empirical equation of state in terms of the Helmholtz energy is presented for n-octane. It is valid from the triple-point temperature 216.37 K to 650 K with a maximum pressure of 1000 MPa and allows for the calculation of all thermodynamic properties in the vapor and liquid phase, in the supercritical region, and in equilibrium states. In the homogeneous liquid phase, the uncertainty in density is 0.03% at atmospheric pressure. For pressures up to 200 MPa and temperatures between 270 and 440 K, density is described with an uncertainty of 0.1%. Outside this region, the uncertainty in the liquid phase increases to 0.5%. Densities in the vapor phase are estimated to be accurate within 0.5%. The uncertainty in vapor pressure depends on the temperature range and varies from 0.02% to 0.4%. Speed of sound in the liquid phase at temperatures below 500 K is described with an uncertainty of 0.1% or less. The isobaric heat capacity in the liquid phase can be calculated with an uncertainty o...
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Dans le cas d'une installation de production d'energie comprenant au moins un circuit turbine a gaz pourvu d'une chaudiere a recuperation (4) et au moins un circuit turbine a vapeur fonctionnant a l'aide de la chaudiere a... more
Dans le cas d'une installation de production d'energie comprenant au moins un circuit turbine a gaz pourvu d'une chaudiere a recuperation (4) et au moins un circuit turbine a vapeur fonctionnant a l'aide de la chaudiere a recuperation (4). Le circuit turbine a gaz est a moitie ferme, sensiblement exempt d'emissions et comprend sensiblement un compresseur (1), une chambre de combustion (2) implantee en aval du compresseur (1), une turbine a gaz (3) implantee en aval de la chambre a combustion (2), une chaudiere a recuperation (4) implantee en aval de la turbine a gaz (3) et au moins un generateur (8) couple a la turbine a gaz (3). L'invention concerne egalement des modes de fonctionnement de circuits turbines a gaz a l'arret permettant un demarrage a l'air frais, sachant que des premiers moyens (12) permettent d'introduire de maniere alternative ou complementaire du gaz chaud dans la voie de gaz chaud (23) situee entre la turbine a gaz (3) et la ch...
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Thermodynamic fluid properties with low uncertainties are needed for the development of a variety of industrial and scientific applications. Although significant improvements have been made in predicting properties from theoretical... more
Thermodynamic fluid properties with low uncertainties are needed for the development of a variety of industrial and scientific applications. Although significant improvements have been made in predicting properties from theoretical methods, the need for more accurate empirical equations of state for...
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Eine Gasturbinenanlage (16) mit einem Verdichter (1), einer Brennkammer (2), einer Turbine (3) und mindestens einer Warmesenke (4) wird mit einem Arbeitsmedium in Form eines Kohlendioxid/Wasser-Gemisches betrieben. In der Brennkammer (1)... more
Eine Gasturbinenanlage (16) mit einem Verdichter (1), einer Brennkammer (2), einer Turbine (3) und mindestens einer Warmesenke (4) wird mit einem Arbeitsmedium in Form eines Kohlendioxid/Wasser-Gemisches betrieben. In der Brennkammer (1) reagiert ein Kohlenwasserstoff als Brennstoff (7) mit Sauerstoff (8), und das dadurch entstehende uberschussige Kohlendioxid und Wasser (14) wird dem Kreislauf entnommen. Der Verdichter (1) und die Turbine (3) weisen jeweils einen Rotor mit Laufschaufeln und ein Gehause mit Stromungskanalen und Leitgittern auf. Erfindungsgemass wird bei dem Verdichter (1) und/oder der Turbine (3) die Anpassung an das von Luft verschiedene Expansionsverhalten des Arbeitsmediums durch Modifikationen der Stromungskanale, der Laufschaufeln und/oder der Leitgitter bewirkt.
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During the last several years, accurate multiparameter equations of state have become a common data base for thermodynamic properties both in scientific and industrial applications. This development has been fueled not only by the general... more
During the last several years, accurate multiparameter equations of state have become a common data base for thermodynamic properties both in scientific and industrial applications. This development has been fueled not only by the general increase in the available computing power but also by the availability of corresponding software. Today, interactive programs are available which support common Microsoft Windows® data exchange formats both for numerical and graphical results. These programs are widely used as replacements for printed data tables and charts. When thermodynamic properties have to be included in process calculations directly, Dynamic Link Libraries (DLL’s) are often used in combination with, e.g., Microsoft Excel® sheets. This technique enables calculations of thermodynamic properties within spreadsheets — calculating thermodynamic properties becomes almost as convenient as calculating trigonometric functions in this way. At the same time, the use of classical source code libraries for the calculation of thermodynamic properties, where the user has to specify his or her own main program and very often has to deal with problems depending on features of special compilers, is retrogressive and is becoming increasingly restricted to applications where the computational speed is a major criterion. Finally, there is still a small number of users who develop their own programs since they have special requirements either with regard to the code or with regard to the algorithms.
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Comprehensive (p, ρ, T) measurements on two binary mixtures (0.10 CO2+0.90 N2 and 0.15CO2+0.85 N2) were carried out in the gas phase at seven isotherms between (250 and 400)K and pressures up to 20MPa using a single sinker densimeter with... more
Comprehensive (p, ρ, T) measurements on two binary mixtures (0.10 CO2+0.90 N2 and 0.15CO2+0.85 N2) were carried out in the gas phase at seven isotherms between (250 and 400)K and pressures up to 20MPa using a single sinker densimeter with magnetic suspension coupling. A total of 69 (p, ρ, T) data for the first mixture and 69 (p, ρ, T)
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Densities in the homogeneous liquid phase of (mono-)ethanolamine (MEA) and diethanolamine (DEA) were investigated using a commercially available high-pressure vibrating-tube densimeter (VTD). Due to the melting point of the experimental... more
Densities in the homogeneous liquid phase of (mono-)ethanolamine (MEA) and diethanolamine (DEA) were investigated using a commercially available high-pressure vibrating-tube densimeter (VTD). Due to the melting point of the experimental materials, the setup of the VTD had to be modified by an insulated housing of the entire piping including the pressure pump. The insulated housing could be heated up by a temperature-controlled heating fan. The liquid samples with a purity of (0.9994 or 0.9950) mole fraction, respectively, were decanted within an inert protective argon atmosphere and further degassed by several freeze–pump–thaw cycles. Density measurements were carried out at temperatures between (293, respectively, 313 and 423) K and at pressures between (5 and 90) MPa. The resulting 140, respectively, 120 (p, ρ, T) data points, explicitly extend the published database for MEA and DEA, with regards to pressure. A comparison with the currently used equations of state for MEA and DEA ...
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We report experimental speeds of sound in methanol. Measurements were conducted at temperatures from 233 to 353 K with pressures up to 20 MPa using the double-path length pulse-echo technique. The relative expanded combined uncertainty... more
We report experimental speeds of sound in methanol. Measurements were conducted at temperatures from 233 to 353 K with pressures up to 20 MPa using the double-path length pulse-echo technique. The relative expanded combined uncertainty (k = 2) in measurement was estimated to vary from 0.012 to 0.014%, considering contributions from temperature, pressure, path length calibration, pulse timing, and purity of the sample. Experimental speeds of sound gained in the scope of this work were compared with the equation of state by de Reuck and Craven, as well as with further data from literature.
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For carbon capture and storage (CCS) applications different sets of equations of state are used to describe the whole CCS-chain. While for the transport and pipeline sections highly accurate equations of state (EOS) explicit in the... more
For carbon capture and storage (CCS) applications different sets of equations of state are used to describe the whole CCS-chain. While for the transport and pipeline sections highly accurate equations of state (EOS) explicit in the Helmholtz energy are used, properties under typical geological storage conditions are described by more simple, mostly cubic EOS, and brines are described by Gibbs energy models. Combining the transport and storage sections leads to inconsistent calculations. Since the used models are formulated in different independent variables (temperature and density versus temperature and pressure), mass and energy balances are challenging and equilibria in the injection region are difficult to model. To overcome these limitations, a predictive combination of the Gibbs energy-based IAPWS seawater model (IAPWS R13-08, 2008) with Helmholtz energy-based multi-parameter EOS is presented within this work. The Helmholtz energy model used in this work is based on the EOS-CG...
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1 Introduction.- 2 History and Potentials - an Overview.- 3 Using Multiparameter Equations of State for Pure Substances.- 4. Setting Up Multiparameter Equations of State for Pure Substances.- 5 The Performance of Multiparameter Equations... more
1 Introduction.- 2 History and Potentials - an Overview.- 3 Using Multiparameter Equations of State for Pure Substances.- 4. Setting Up Multiparameter Equations of State for Pure Substances.- 5 The Performance of Multiparameter Equations of State.- 6 Generalised Functional Forms.- 7 Generalised Equations of State.- 8 Describing Mixtures with Multiparameter Equations of State.- References.
An equation of state (EOS) is presented for the thermodynamic properties of benzene that is valid from the triple point temperature (278.674 K) to 725 K with pressures up to 500 MPa. The equation is expressed in terms of the Helmholtz... more
An equation of state (EOS) is presented for the thermodynamic properties of benzene that is valid from the triple point temperature (278.674 K) to 725 K with pressures up to 500 MPa. The equation is expressed in terms of the Helmholtz energy as a function of temperature and density. This formulation can be used for the calculation of all thermodynamic properties. Comparisons to experimental data are given to establish the accuracy of the EOS. The approximate uncertainties (k = 2) of properties calculated with the new equation are 0.1% below T = 350 K and 0.2% above T = 350 K for vapor pressure and liquid density, 1% for saturated vapor density, 0.1% for density up to T = 350 K and p = 100 MPa, 0.1 – 0.5% in density above T = 350 K, 1% for the isobaric and saturated heat capacities, and 0.5% in speed of sound. Deviations in the critical region are higher for all properties except vapor pressure.
Adiabatic Compressed Air Energy Storage (A-CAES) represents a zero emission electrical storage technology together with acceptably high cycle efficiency. Therefore the application of internal heat storage becomes necessary. One main... more
Adiabatic Compressed Air Energy Storage (A-CAES) represents a zero emission electrical storage technology together with acceptably high cycle efficiency. Therefore the application of internal heat storage becomes necessary. One main characteristic of such A-CAES is that the heat generated during compression exceeds the amount of usable heat for the expansion process afterwards. In real life cycling mode this could lead to a heat storage overload. For heat storage management four possible solutions are proposed and discussed quantitatively. A dynamic model of the whole A-CAES process is under development with the focus on the stratified high-temperature heat storage. After an introduction to basic mechanisms relevant for the understanding of heat management in an A-CAES context, a brief explanation of model structure is given.
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Abstract This study reports new density measurements of the (CO2 + CO) system at temperatures from (283 to 373) K and pressures up to 48 MPa for four different mixtures, with compositions ranging from (5 to 50) mol% CO. A commercial... more
Abstract This study reports new density measurements of the (CO2 + CO) system at temperatures from (283 to 373) K and pressures up to 48 MPa for four different mixtures, with compositions ranging from (5 to 50) mol% CO. A commercial vibrating-tube densimeter was used to measure the density of each mixture as a function of pressure and temperature. Temperature and pressure were measured with expanded uncertainties (k = 2) of 0.05 K and 0.035 MPa, respectively. The relative combined expanded uncertainty (k = 2) of the density was estimated to be between (0.2 and 1.8) %, with values ≤1% for most state points. The new data significantly expand the pressure and composition ranges of the available density data for the (CO2 + CO) system. Together with recently published vapour-liquid-equilibrium data, the new data enabled the development of an improved Helmholtz-energy-explicit mixture model. The new model is based on the mathematical approach of the GERG-2008 and EOS-CG models with new adjustable parameters. As a result, the new mixture model allows for a significantly more accurate description of the thermodynamic properties of the (CO2 + CO) system than GERG-2008 and EOS-CG. A detailed comparison among our density data, experimental data from the literature and the different mixture models is presented.
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Abstract Pyrolysis experiments on a high volatile bituminous Columbian coal were performed in a laminar drop tube reactor at T = 1300 K and 1475 K. Measurements in CO2 were carried out at different residence times up to 150 ms, and the... more
Abstract Pyrolysis experiments on a high volatile bituminous Columbian coal were performed in a laminar drop tube reactor at T = 1300 K and 1475 K. Measurements in CO2 were carried out at different residence times up to 150 ms, and the data were complemented by end-point measurements in N2 at approximately 165 ms. These low residence times are typical for the duration of pyrolysis in pulverized coal flames. Mass loss has been determined by solid sampling based on the ash tracer method, and the evolution of porosity was evaluated. Pyrolysis mass loss kinetics were determined based on a single first order reaction and a competing two-step reaction model with distributed activation energies. The particle temperature and residence time needed for the determination of the kinetics were derived by CFD simulations. Results indicate that, despite the low residence time selected, the influence of the Boudouard reaction on mass loss and, hence, evolution of porosity cannot be neglected. In general, porosity increases with increasing residence time and progressing mass loss and porosity is influenced by the both, the release of volatiles and the contribution of gasification.
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Abstract Liquid air energy storage (LAES) is a storage technology for electric energy, using liquefied air as storage medium. Balancing fluctuating power in- and outputs, storage systems improve the integrability and availability of... more
Abstract Liquid air energy storage (LAES) is a storage technology for electric energy, using liquefied air as storage medium. Balancing fluctuating power in- and outputs, storage systems improve the integrability and availability of renewable energies. Due to the high energy density of liquefied gases, the storage volume is small, especially compared to similar storage technologies as pumped hydro or compressed air energy storage. During the charging process, ambient air is liquefied with an adopted Claude-cycle using additional cold from a cold storage. When the electricity demand is high, liquid air is released from the storage tank for power generation in the discharging phase. Therefore, liquid air is pressurized with a cryo-pump, heated up in the cold storage and finally expanded using an air-expander. The cold storage is cooled down to cryogenic temperatures again. Transferring cold from the discharging to the charging phase, the cold storage is one of the key components, influencing the process efficiency of the LAES-system. One option to design the cold storage is a packed bed cold storage (PBCS), which consists of a simple cylinder and a packed bed of storage material. Investigations on thermodynamic properties show that the temperature-dependent heat capacity of the storage material has a major influence on the performance of the cold storage. The influence of different heat capacity characteristics on the performance of the PBCS is systematically analyzed. The resulting theory is applied to existing storage materials and their related heat capacities. Nine storage materials are investigated, ranging from metals to ceramics, minerals and plastics.
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Abstract The DFG Collaborative Research Center SFB/TRR129 “Oxyflame” is devoted to developing a fundamental understanding of effects relevant for the combustion of solid fuels in oxyfuel atmospheres. 17 complementary research projects at... more
Abstract The DFG Collaborative Research Center SFB/TRR129 “Oxyflame” is devoted to developing a fundamental understanding of effects relevant for the combustion of solid fuels in oxyfuel atmospheres. 17 complementary research projects at RWTH Aachen, TU Darmstadt, and Ruhr-Universitat Bochum both numerically and experimentally deal with various aspects on scales reaching from single particles to complete combustion chambers. As part of this framework, this project experimentally addresses the impact of sorption effects on the surface of chars and of the diffusion into pores. Since the adsorption of different components of oxyfuel atmospheres is selective and since the composition of a boundary layer on the surface of char particles is relevant for equilibria and dynamics of heterogeneous reactions during char burnout, selectivities of sorption and effective diffusion coefficients are considered important inputs for the advancement of particle-burnout models. This paper describes results of measurements of the sorption of main components of oxyfuel atmospheres (CO 2 and O 2 ) on char particles. Selectivities are derived from the experimental results. The extrapolation of selectivities to higher temperatures, which is essential for their application in burnout models, is discussed.
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Abstract The revised Klosek and McKinley (RKM) method is a well-established model for the calculation of saturated liquid densities within the field of liquefied natural gas (LNG) custody transfer. Due to pressures higher than the vapor... more
Abstract The revised Klosek and McKinley (RKM) method is a well-established model for the calculation of saturated liquid densities within the field of liquefied natural gas (LNG) custody transfer. Due to pressures higher than the vapor pressure in pipes from tanks to transfer stations, the densities resulting from this easy-to-use approach often deviate from the true density of the compressed liquid phase. However, higher pressures are typical for pipe flows in receiving terminals. Therefore, the applicability of the RKM method was expanded with the most recent highly accurate ( p , ρ , T , x ) data sets for six compressed LNG mixtures measured with a special densimeter for cryogenic liquid mixtures. The newly developed enhanced RKM (ERKM) method now enables density calculations of LNG mixtures at pressures up to 10 MPa, and the temperature restriction of the RKM method ( T k = 2) of the newly developed equation is 0.10% for the temperature range from (100 to 115) K and 0.15% for temperatures between (115 and 135) K at pressures up to 10 MPa. Further restrictions of the method are basically the same as for the RKM method and are specified in more detail within the present paper.
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Abstract The (p, ρ, T, x) behaviour of five different synthetic liquefied natural gas (LNG) mixtures was investigated over the temperature range from (105 to 135) K at pressures up to 8.9 MPa utilizing a single-sinker magnetic suspension... more
Abstract The (p, ρ, T, x) behaviour of five different synthetic liquefied natural gas (LNG) mixtures was investigated over the temperature range from (105 to 135) K at pressures up to 8.9 MPa utilizing a single-sinker magnetic suspension densimeter for cryogenic liquid mixtures. Due to the supercritical liquefaction procedure and the integration of a special VLE-cell, it was possible to measure densities in the homogeneous liquid phase of LNG without changing the composition. The mixtures were prepared gravimetrically and then analysed by gas chromatography according to highest metrological standards. The relative combined expanded uncertainty (k = 2) in density considering all effects, including the uncertainty in composition, was approximately 0.044% for all measurements. Comparisons of the new experimental data to the GERG-2008 equation of state for natural gas mixtures revealed clear and systematic deviations up to 0.22%. The reported uncertainty for the GERG-2008 equation is (0.1 to 0.5)% for the conditions considered, thus, all measured densities are represented well within this uncertainty range. Comparisons to density calculation methods often used in LNG industry, such as the revised Klosek and McKinley method as well as the COSTALD correlation, revealed that the quality of the calculations clearly depends on the pressure range and on the composition of the LNG mixture.
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As a full service provider of power generation plants and equipment, ALSTOM Power (hereafter called ALSTOM), is aware of the present scientific concerns regarding greenhouse gas emissions and the role of fossil fuel use for power... more
As a full service provider of power generation plants and equipment, ALSTOM Power (hereafter called ALSTOM), is aware of the present scientific concerns regarding greenhouse gas emissions and the role of fossil fuel use for power generation. ALSTOM R&D laboratories run various programs aimed at finding options that reduce or avoid emissions through: - high efficiency power generation equipment with the most modern technologies to utilize fossil fuels with the lowest possible emissions, - technologies to remove and sequester CO 2 created in power plants in an environmentally and economically favorable manner, and - technologies to utilize biomass fuel as a method for CO 2 neutral power generation. In this paper, an overview of on-going CO 2 mitigation activities is addressed. Energy efficiency improvements for both new and existing power plants are briefly reviewed for natural gas. The status of development of ALSTOM technology for biomass in industrial gas turbines is presented. Additionally, combustion in O 2 /CO 2 atmospheres including different novel power generation cycles using pure or enriched oxygen are discussed. Conclusions are drawn regarding efficiency, energy consumption and technical feasibility.