PERFORMANCE EVALUATION OF SPRAY DRYER

CHAPTER ONE 1.0 INTRODUCTION Spray drying is a process of suspending sprayed liquid particles and moisture removal by hot air leading to produce high quality products. The high quality of the spray-dried products is due to the protection of the suspended particles through evaporative cooling during the process. Spray dryers are commonly used for powder production of some products such as milk, coffee, tea, egg, enzymes, whey protein, fruits and vegetables extracts, ceramic materials, dyes and detergents. The dryers are one of the most functional types of dryers (Vincent, J. Pinto, J. Menezes, J. and Gasper, F. 2013). During recent years, the need for reduction in weight and volume of food products has led to significant developments in the design of spray dryers. These dryers increase surface to volume ratio of the liquid particles and consequently enhance the heat and mass transfer during the drying process. Of among other advantage of spray dryers, continuous operation, and full automatic control system, rapid drying, reduced corrosion problems and manufacture of products with desirable size and density can be referred. However, their main disadvantages include high installation costs and removal of aromatic volatiles (Vicente et al., 2013). The spray dryer to be evaluated is a commercial spray dryer that was purchased by the management into the Department of Chemical Engineering, Bida Niger State as at the year 1990. Ever since the spray dryer was purchased its purpose has not been fully actualized, and it is for this sole purpose that this particular group of student has been given the task to work on it and to see it work real life at the end of this research work. Today, application of spray dryers in different industries is growing more than ever. For example, preparation and processing of medicinal and food microcapsules with the aid of spray dryers is one of these recent advances (Frascareli et al., 2012; Borrmann et al., 2013; Estevinho et al., 2013). Microencapsulation is a high throughput process by which the particles or droplets are coated with organic or mineral substances. The core material is located inside the coating (membrane). This process is aimed at controlled release of the core materials at a given time and fixing their concentration in the required environment (Fritzen-Freire et al., 2012; Medina-Torres et al., 2013). In spray dryers, a liquid material is pumped into a nozzle from feed source and is sprayed as tiny droplets into a drying chamber (Vicente et al., 2013). On the other hand, hot air is circulated inside the chamber. Hot air contact with the liquid droplets leads to the heat and mass transfer between the droplets and the air followed by rapid evaporation of moisture. The produced powder and the air is sucked into a cyclone and separated from each other by centrifugal force. In the last step of the drying process, the produced powder exits from the bottom of the cyclone and the air exits from the top (Mazidi et al., 2009). This research project is intended to evaluate the spray dryer, thereby replacing any missing accessories, installation of the accessories as directed by the operating manual, test running of the spray dryer using a concentrated feedstock to be dried, proposed and design of a commercial scale spray-drying process for a powered food item and lastly commissioning of the spray dryer. 1.1 AIM AND OBJECTIVES The aim of this project is to evaluate an already existing spray dryer that will be used to produce a powdered item; this, which could be achieved through the following: To understand the principle of operation of a simple spray dryer. To troubleshoot the spray dryer to be evaluated. To provide the vital accessories and installation of the spray dryer. To carry out a performance test of the spray dryer by producing a powdered food item. To propose a profitable powdered food item to be produced within the polytechnic environs. Commissioning of the spray dryer by the school management. 1.2 SCOPE OF WORK This work is limited to the performance evaluation of an APV Anhydro spray dryer. 1.3 PROBLEM STATEMENT The problem statement is to evaluate the spray dryer, make it work and thereby carry out a performance test to produce a powdered food item. 1.4 JUSTIFICATION After the completion of this work, the research is justified as follows: The institution can venture into the production of a powdered food items in the polytechnic environs such as the polytechnic bakery and other entrepreneurship trade in the school environment to generate income and job opportunity. This project would be of ultimate importance to the Department of Chemical Engineering by training chemical engineering students by a senior trainee so as to gain more self-employed ground in the society. Different product types can be ventured such as agglomerates and granules apart from the proposed powdered food. Future plan of expansion due to different sizes and different capacity. CHAPTER TWO 2.0 REVIEW OF RELATED LITERATURE 2.1 Brief History of Spray Drying The development of spray drying equipment and techniques evolved over a period of several decades from the 1870s through the early 1900s. The first known spray dryers used nozzle atomizers, with rotary atomizers introduced several decades later. Because of the relatively unsophisticated designs of the early spray dryers and practical difficulties in operating them continuously, very little commercial use of the process was made until the 1920s. By the second decade of the twentieth century, the evolution of spray dryer design made commercial operations practical. Milk drying was the first major commercial application of the technology. During the next 20 years, manufacturers developed designs to accommodate heat-sensitive products, emulsions and mixtures. Spray drying came of age during World War II, with the sudden need to reduce the transport weight of foods and other materials. This surge in interest led to developments in the technology that greatly expanded the range of products that could be successfully spray dried. (Obón et al., 2009) 2.2 What is Spray Drying Spray drying is a technology used to preserve foods. The core of this technique is spraying a feed material in a liquid state into a hot drying medium (temperature ranging from 100 to 300°C) in which liquid (often water) is evaporated. The final product of a spray drying process is a dried form of powders, granules or agglomerates, depending upon the physical and chemical properties of the feed, the dryer design and operation. Evaporation of water from the droplets is facilitated by heat and vapor transfer through/from the droplets. It is believed that the wet-bulb temperature of the droplets is in the range of 30- 50°C and total duration of drying is only a few seconds. Spray dried food powders show high storage stability, good handling characteristics (for some applications) and minimized transportation weight in comparison with liquid concentrates (Obón et al., 2009). Spray drying is a common method of encapsulation of food ingredients in the food industry. Several studies have demonstrated the efficiency of spray drying to encapsulate food products such as carotenoids, vitamins, minerals, flavours, polyunsaturated oils, enzymes and probiotic microorganisms. (Schuck et al., 2009) The basic steps in the microencapsulation involves the preparation of a stable emulsion to be processed; homogenization of the emulsion; atomization o7f the emulsion; and dehydration of the atomized particles (Dziezak, 1988; Shahidi & Han, 1993). A stable emulsion of fine droplets of the core material in the wall solution is critical during microencapsulation (Kenyon & Anderson, 1988). Therefore, the wall materials need to have emulsifying characteristics as well (Sheu & Roserberg, 1995). In addition, it is reported that the rheological properties of the emulsion is a key parameter in the spray drying process; thus, an emulsion with high viscosity causes the formation of large droplets which affects the drying rate (Drusch, 2007). The spray drying procedure involves: Concentration of the feed prior to spray drying. Atomization of the feed to create the optimum conditions for evaporation to a dried product having the desired characteristics. Droplet–air contact in the chamber, the atomized liquid is brought into contact with hot gas, resulting in the evaporation of +95% of the water contained in the droplets in a matter of a few seconds. Droplet drying, moisture evaporation takes place in two stages: During the first stage, there is enough moisture in the drop to replace the liquid evaporated at the surface and the evaporation rate is relatively constant (Keey & Pham, 1976), and The second moisture evaporation stage begins when there is no longer enough moisture to maintain saturated conditions at the droplet surface, causing a dried shell to form at the surface. The evaporation rate depends on the diffusion of moisture through the shell, which increases in thickness as the evaporation proceeds. The final step in a conventional spray drying process is: Separation: this involves the use of cyclones, bag filters, and/or electrostatic precipitators (Patel et al., 2009). Spray drying is a technology that can be used with both heat-resistant and heat sensitive products, and from which nearly spherical particles can be produced. According to Patel et al. (2009), the critical elements of a spray drying system includes the atomizer, the air flow, and the spray drying chamber 2.3 Unit Operations of spray drying Spray drying consists of the following unit operations: Pre-concentration of liquid. Atomization (creation of droplets). Drying in stream of hot, dry air. Separation of powder from moist air. Cooling. Packaging of product. Plate 2.1: Spray drying (Gharsallaoui et al., 2007) 2.4 Principle of Operation of a Spray Dryer The liquid product is pumped to the atomizer front where it is dispersed into a mist of fine droplets in the drying chamber. The intensive contact between the hot process air and the atomized liquid ensures fast and gentle drying. The basic plant is supplied with a two-fluid spray nozzle placed in the chamber cone (fountain mode). And the atomization of the liquid is effectuated by means of compressed air, the process air is heated indirectly in an electrical air heater prior to entering the drying chamber product and drying air are in counter-current flow. The drying air and powder leave the chamber through the outlet in the conical bottom and are conveyed to a cyclone front where the powder is discharged into a powder container while the outlet air is discharged at the top of the cyclone. 2.5 Essential components of a spray dryer Atomizer The atomizer is the “heart” of any spray drying system. One of the functions of the atomizer is to disperse the feed material into small droplets, which increases the surface are and allows a well distribution of the feed within the dryer chamber. The atomized droplets must not be large that they produce an incomplete dried product, nor so small that the product recovery is difficult. There are different configurations of atomizers; however, the most common designs are in the form of high-speed rotating disc, two fluid nozzles; airless atomization nozzles; pressure nozzle; an ultrasonic nozzle. Air flow pattern Co-current flow: in a co-current dryer, the spray is directed into the hot air entering the dryer and both pass through the chamber in the same direction. Counter-current flow: in this dryer design, the spray and the air are introduced at opposite ends of the dryer, with the atomizer positioned at the top and the air entering at the bottom. Mixed flow: dryers of this type combine both co-current and counter current flow. In a mixed flow dryer, the air enters at the top and the atomizer is located at the bottom. Spray drying chamber Air circulating with the chamber keeps a flow pattern, this prevent the deposition of partially dried product on the wall or atomizer (Ronald, 1997). Air movement and temperature of inlet air influences the type of final product. In addition to the critical elements of a spray drying system, (Patel et al.,2009) describes the inlet air temperature, outlet air temperature, viscosity of the feed, solid content of the feed, surface tension of feed, feed temperature, volatility of the solvent, and nozzle material as critical parameters of spray drying process. Spray drying technology is widely used by the food industry. This is an ideal process where the end-product must comply with precise quality standards regarding particle size distribution, residual moisture content, bulk density and morphology. The production of food powders by spray drying has gained more attention in the recent years due to the versatility and controllability of a spray drying system. Plate 2.2: Airflow pattern Plate 2.3: Centrifugal Atomizer Plate 2.4: Drying Chamber Plate 2.5: Nozzle Atomizer 2.6 Types of a spray dryer Two stage dryer: Two stage dryers allow the use of lower temperatures in the dryer, making the design a good choice for products that are particularly heat sensitive (Katta & Gauvin, 1976). Horizontal dryer: The horizontal spray dryer consist of a horizontal drying chamber with a conveyor embedded inside to convey the dried product to be separated by the cyclone. Vertical dryer: It is suited for both non-fat and fat-containing products, producing non-agglomerated and agglomerated free-flowing powders. Manufacturers of vertical spray dryers include Stork, Niro and APV Anhydro. Fluidized dryer: Fluidized Spray Dryer combines spray drying and fluid bed drying technologies and offer excellent product flexibility and excellent thermal efficiency. Sticky products can be dried successfully, and the concept is ideal for drying heat sensitive products, and improved aroma retention is accomplished (Sommerfeld & Blei, 1992). Multi stage dryer: The process produces non-dusty, free flowing agglomerated powders with high flavour retention. It operates with low outlet-temperatures, achieving high thermal efficiency. This design concept is successful for drying high fats, hygroscopic, and sticky products that are difficult to handle in more conventional designs. Compact spray dryer: Atomization is created by either a rotary atomizer or spray nozzle atomizer. The location of the fluid bed within the drying chamber achieves drying at lower temperature levels. It results in higher thermal efficiencies and cooler conditions for powder handling. Integrated filter dryer: Integrated Filter Dryer - Combines an integrated fluid bed and filter arrangement. It is an adaptable and flexible spray dryer for the food ingredients, food, dairy, chemical, and pharmaceutical industries. The Integrated Filter Dryer (IFD™): features and benefits includes: improves powder quality, no handling of product outside drying chamber, reduced noise level and lower energy consumption. Foam spray dryer: In this method liquid food is foamed, such as milk or coffee, before spraying it into the drier. The result is faster drying rate from the expanded foamed droplet surface area, and lighter density dried product. This is known as foam-spray drying (Hanrahan & Webb, 1961). Filtermat dryer: The FILTERMAT® Spray Dryer is frequently used in food and dairy applications. It operates at a low outlet temperature, achieving high thermal efficiency. It is the recommended system for drying high fat, sugar-based, hydrolyzed, and fermented products (Buckton & Roser, 2005). 2.7 Advantages of a spray dryer Able to operate in applications that range from aseptic pharmaceutical processing to ceramic powder production. Can be designed to virtually any capacity required. Feed rates range from a few pounds per hour to over 100 tons per hour. Powder quality remains constant during the entire run of the dryer. Operation is continuous and adaptable to full automatic control. A great variety of spray dryer designs are available to meet various product specifications. Can be used with both heat-resistant and heat sensitive products As long as they are can be pumped, the feedstock can be abrasive, corrosive, flammable, explosive or toxic. Feedstock can be in solution, slurry, paste, gel, suspension or melt form. Product density can be controlled Nearly spherical particles can be produced. Material does not contact metal surfaces until dried, reducing corrosion problems. 2.8 The limitations of spray drying High installation cost. Large air volumes at low product hold-up implies gas cleaning costly. Lower thermal efficiency. Heat degradation possibility in high temperature spray drying. 2.9 Dryer Selection Chart Plate 2.6: Dryer chart (BETE Manual, 2005) Plate 2.7: Dimensions of pilot scale spray dryer 2.10 Spray Nozzle Maintenance 2.10.1 Nozzle Wear Nozzles used for spray drying are generally operated at high pressures. Feedstock is abrasive and travel through the nozzles at high velocities, removing material from the internal components. As the nozzle components wear, the performance degrades. The most common symptoms of worn nozzles are an increase in flow rate, degradation of spray pattern uniformity and an increase in droplet size. (BETE spray dryer manual, 2005). 2.10.2 Swirl There are three areas of the swirl that will show the first visible signs of wear: the narrow “tongue” that forms one side of the inlet, the corner between the bottom and wall of the chamber and the bottom of the chamber itself. Of these three areas, the one that will have the most effect on the spray pattern will be the tongue. Once the tongue shows significant signs of wear, the swirl should be replaced. (BETE spray dryer manual, 2005). 2.10.3 Orifice disk In most cases, the orifice will wear uniformly and the hole diameter will grow in size, causing the flow rate to increase. (BETE spray dryer manual, 2005) recommends that operators change orifice disks when the flow rate increases by 5%, which is equivalent to a hole diameter increase of 2.5%. 2.10.4 Seals Leaking nozzles in a spray dryer can cause serious problems, including ruined product, fires and explosions. For this reason, it is critical to ensure that the nozzles will not leak during operation. Most Twist & Dry nozzles use o – rings as seals. Because of the high operating pressures and high temperatures of the spray dry chamber, BETE recommends that the o – rings be replaced each time that the nozzle is disassembled. BETE recommends the use of a USDA approved lubricant on all o – rings. Twist & Dry nozzles with o – ring seals are designed to be assembled with very low torque. BETE recommends that these nozzles be assembled hand tight only. (BETE spray dryer manual, 2005). 2.10.5 Body The velocity of feedstock through the internal passages of the body are much lower than the velocity through the swirl and orifice and, as a result, wear rates are much lower. The body is attached to the feed pipe either by welding or by tapered pipe threads. For bodies with a threaded connection to the supply pipe, (BETE spray dryer manual, 2005) recommends the use of Loctite 272 thread sealant. To apply Loctite 272 thread sealant: Clean threads with wire brush. Clean thoroughly with clean, untinted alcohol. Apply a coating of Loctite 7471 primer to the threads and allow 15 minutes to cure. The prime ensures clean threads and assists with rapid setting of the thread sealant. Apply a generous coating of Loctite 272 thread sealant to the male thread. Assemble the nozzle body onto the feed pipe. Remove excess sealant. Allow sealant to cure before using. At room temperature, curing time is approximately 24 hours. At 100-120°F (40-50°C) the curing time is reduced to approximately 1 hour. (BETE spray dryer manual, 2005). 2.11 Spray Dryer Applications (BETE spray dryer manual, 2005) has detailed information from published reference sources for many specific spray drying applications. The following are brief descriptions of the broad applications. 2.11.1 Chemical industry Applications for spray drying in the chemical industry are growing faster than in any other industrial segment. The huge increase in the use of synthetics has triggered a demand for plastic resins. The spray drying of PVC is a particular stand out. There are two main techniques of PVC production that may require spray drying: emulsion polymerization (E-PVC) and suspension polymerization (S-PVC). Spray drying using either nozzles or rotary atomizers is the only practical way to dry E-PVC. Spray drying of S-PVC is usually dried in drum dryers or flash/fluid bed dryers, but it may occasionally be dried in spray dryers. Melamine, urea formaldehyde, SBR and ABS resins are usually atomized with rotary atomizers. Polycarbonate resins are often atomized with nozzles. (BETE spray dryer manual, 2005). 2.11.2 Ceramic materials Spray dried powders in the ceramics industry are ideal for pressing and sintering operations. Spray dryers produce free-flowing ceramic powders that allow rapid filling of pressing dies. Spray dryers for ceramic materials use either rotary atomizers or nozzles. Nozzles are mainly used to produce coarse powders in medium-to-low-capacity dryers. Spray drying, using both rotary atomizers and nozzles is used extensively in manufacturing ceramic oxides. Nozzles are normally used to produce coarse (250-300 micron) powders. Hard ferrites (barium and strontium iron oxides) are used extensively in the manufacture of permanent magnets. Soft ferrites (manganese-zinc and nickel zinc- iron oxides) are used to produce electromagnets. Spray dryers with rotary atomizers do the initial drying of green materials prior to calcining. Spray dryers with nozzle atomizers produce the final coarse powder from the calcined material. Steatite, a material used to manufacture electrical insulators, is generally produced in spray dryers using nozzle atomizers. Spray dried glass is used for insulating material. Carbide (tungsten, titanium, tantalum and niobium) suspended in organic milling liquids is spray dried with nozzle atomizers. Because of the explosive hazard caused by the organic materials, these dryers are closed-cycle. Abrasive grits are spray dried in order to produce a dried product of uniform moisture and narrow size distribution. Because of the extreme abrasiveness of the material, rotary atomizers are normally used for this, but occasionally low-pressure nozzles are used. (BETE spray dryer manual, 2005). 2.11.3 Detergents, Soaps and Surface Active Agents The production of washing powders is one of the most common spray dry applications. Counter – current dryers with nozzle atomization are preferred for high-bulk-density detergents. Open-cycle dryers are most commonly used, but some installations use self – inertizing designs. Co-current dryers are used for low-bulk-density detergents. Optical brighteners are chemicals used to brighten fabrics during washing. Optical brighteners are spray dried in co-current dryers with rotary atomizers or nozzles. Scents for washing powders are spray dried in co – current dryers with either rotary atomizers or nozzles. During the spray drying process small droplets of perfume oil are micro-encapsulated within a protective colloid capsule. The colloid forms a protective skin to prevent the loss of fragrance due to evaporation. (BETE spray dryer manual, 2005). CHAPTER THREE 3.0 METHODOLOGY 3.1 MATERIAL AND METHOD 3.2 Materials A complete set of tool box supplied by the manufacturer of the equipment were used; the tools contained includes: mallet hammer, set of spanners, set of Allen keys, and lubricating oil were used to carryout necessary troubleshooting and installation. The parts to install was also provided by the manufacturer of the spray dryer includes: centrifugal atomizer, atomizer spin, and the motor to drive the atomizer. Cleaning and dusting materials was also used to render the equipment free from dirt. Digital multi – meter was also used to carry out the continuity test of the electrical components such as the transformers, speed controller for DC motor, speed transistor, the overload relay box etc. 3.3 Methods 3.3.1 Cleaning and Dusting Of the Equipment The equipment was set free from dirt using detergent, mops, brooms, and water. 3.3.2 Troubleshooting This step which means fault finding was carried out using a digital multi – meter. All the electrical components was well checked to detect faults. It was found out that all the electrical parts such as the transformers, speed controller, overload relay fuse, overload relay box, the electric contactors, speed transistor, etc. were all working properly. In the process it was discovered that the centrifugal atomizer and feed pump module responsible to drive the electrical motor of the atomizer and feed pump were found faulty. However, reasonable effort was done to ensure that the module will be repaired or replaced. The electric air heaters, which has not been in operation for rather long period resulted to small leakage of currents which arises because of condensation in or on the insulating material. In order to restore the electric air heater, the accumulated condensation was removed and successive increase in the heating unit was done. The electric heater controllers were found to be malfunctioning, but now repaired. 3.3.3 Installation The installation of the parts includes both electrical and mechanical installation: Electrical installation: the materials listed below was installed to power the spray dryer: ELCB circuit breaker three (3) phase, three (3) 100 Amp industrial fuse, neutral fuse, four (4) coils 25 mm (cable 85 meter) aluminum conductor, two (2) coils of 10 mm copper, one (1) meter board and one(1) pack of 3 inches concrete nails. The functions of some material used to power the spray dryer is explained as follows: Circuit breaker: is an automatically operated electrical switch designed to protect the electrical circuit from damage caused by overcurrent or overload or short circuit. Its basic function is to interrupt current flow after protective relays detect a fault in the spray dryer. Industrial fuse: its function is to prevent the conductors or any part carrying short –circuit from attaining temperature greater than its design value and electrodynamic – withstand ‘levels. Cables: the 25 mm cable made of aluminum conductor was used to supply power from the change – over in the control room down to the industrial fuse Vis circuit breaker. And the 10 mm copper cable was used to supply power from the circuit breaker to the spray dryer. Mechanical installation: the mechanical installation of the equipment includes: the centrifugal atomizer coupled with the motor, nozzle atomizer, welding of the leg equipment layout and the chimney. Centrifugal atomizer: With the aid of the assembling instructions from the compact spray dryer manual, the centrifugal atomizer was installed with the motor attached to the centrifugal atomizer. This was done by placing the insert cone in the air distributor, the insert cone is provided with guide vent which are normally used to give the air flow a rotating movement in the same direction as the atomizer direction of the rotation. A rubber gasket for ceiling between the atomizer and the drying chamber was also placed. The atomizer was then lowered into the air distribution chamber in such a way that the feed pipe union fits with the feed pipe. The feed pipe was kept in place and sealed by means of a retainer ring. In using a centrifugal atomizer, the reinforced plastic tube leading from the pressure side of the feed pump was connected the other end of the feed pipe. Nozzle atomizer: In installing the nozzle atomizer, the plug in the atomizer access opening was removed and the atomizer inserted ensuring that the guide pin was in the correct position. The reinforced plastic tube connected to the pressure side of the pump was fastened to the lower connection, the compressed air supply also connected to the upper nipple through a reinforce plastic tube. It was noted that, if the nozzle atomizer is to be used, the centrifugal atomizer will be removed and the cover will be placed over the roof. A check was also carried out to see whether the nozzle is correctly position by pouring water into the feed vet, and pumping it through the nozzle without applying compressed air. Welding: one of the supporting leg of the spray dryer got broken during the process of relocating the machine to its layout. The welding was done using arc welding which was done by jacking the spray dryer with a heavy duty jack from mechanical engineering department. Equipment layout: The compact spray dryer was positioned at an angle 90, corner edge of the workshop, with its control panel facing the fuse and circuit breaker installed in the workshop. The reason for positioning the spray dryer at that position was to enable an easy outlet of the chimney (exhaust line) from the spray dryer. Chimney: The chimney is to be passed through the top window by the side of the spray dryer, and it will be supported with a set of laid blocks in other to not to cause vibration. Before the chimney was constructed, critical analysis was done on where to place the equipment which was 1.5 meters away from the wall and the diameter of the opening at the top of the equipment was measured so as to enable appropriate fittings of the constructed chimney. The chimney was constructed using four (4) pieces of 16 grade black sheets, six (6) pieces of 10 – 11 inches bolt and nuts, one (1) pack of electrode and two (2) gallons of oil paint. 3.4 Safety Precautions Care was taken to follow the order described below for start-up and shut down. Equipment damage or personal injury may result. Caution was observed when operating the heater. The chamber door was not opened when the equipment is in operation, except when following the cleaning procedure as described below. Observation ports are provided to view the drying chamber interior. Checking of the air filter before operating. 3.5 Installation Cost Table 3.1: Detailed cost of installing the spray dryer. S/N Material Quantity Amount Total 1. ELCB Circuit breaker (A&B) 1 ₦14, 000 ₦14, 000 2. Recline 25 mm Aluminum cable 85 m ₦350 per m ₦29, 750 3. 100 mm Industrial fuse 3 ₦1,200 ₦3, 600 4. 10 mm Copper cable 30 m ₦200 per m ₦6, 000 5. Neutral fuse 1 ₦600 ₦600 6. Meter board 2 ₦100 ₦200 7. Concrete nails 2.5” 1 pack ₦250 ₦250 8. Allen keys 2 set ₦2, 450 ₦2, 450 9. Welding 1 piece ₦4, 000 ₦4, 000 10. Earth rod 1 piece ₦4, 000 ₦4, 000 11. Hoist cable 7 yard ₦400 per yard ₦2,800 12. Slurry making (maize) 30 cups ₦45 per cup ₦1, 350 13. Workmanship 2 persons ₦15, 000 each ₦30, 000 14. Sack covering 1 ₦2, 700 ₦2, 700 14. Miscellaneous ₦7,870 ₦7,870 15. Total ₦109, 520 3.6 Experimental Procedure for centrifugal atomizer 3.6.1 Start – up Procedure The centrifugal atomizer was checked and assembled as described in the manual. It was ensure that the rubber seal on which the atomizer is to rest is intact and position correctly. The atomizer in air distributor was placed and the plug was inserted into the socket. The feed pipe was connected to the atomizer and was checked if the reinforced plastic tube from the pressure side of the pump is connected to the feed pipe. The oil cup of the atomizer was filled. And the oil type was ISO VG 32 or similar. The chamber bottom and cyclone was assembled and the clamp ring was tightened to seal all connection. A powder bucket was fasten under the cyclone and the powder valve was opened to collect the powder. We ensured that the air filter was cleaned and position correctly. The drying chamber door was closed. The door gasket was kept free from impurities so that it should not be damaged from hard object. The feed vat was feed with water. And to avoid calcareous deposit in the drying chamber, distilled water was used. The atomizer speed control and feed pump control was set in the lowest position. The fan was started to depress the start button for the fan. And the built-in lamp light up to indicate that the fan is now running. The atomizer was started and the speed was slowly increased to what is required (25,000 min-1 is the normal speed). The thyristor convertor is with built-in current limitation which protect the motor against overload during normal operation. (The electrical heated units) the electric air heater consist of three sections that totally can heat the air by app. 300oc. the two first section are not equipped with control equipment and can only be applied by on/off operation. Each unit heat the air by approximately 85oc. the third section is equipped with a thyristor control. The third section heat the air by app. 130oc. The control unit was used alone when using the inlet air temperature up to 120oc. and at approximately 200oc was advisable to connect all three section. When the outlet temperature was up to 90oc, water was applied to the atomizer by depressing the start – button for the feed pump and increasing the pump speed. 3.6.2 Drying of feed product After some 20 minutes, the outlet temperature was stable. Then one could switch from water to feed. As the feed product contains dry matter, the mass flow of the product was increased compared to the mass flow of water. To avoid dilution of the product with water, the product was not introduced into the feed vat until it is nearly empty of water. The pump was never allowed to run dry. When the plant was in operation over a prolonged period, the oil level in the oil cup was checked at interval of approximately 8 hours. This was refilled with oil of quality “SHELL TELLUS 37 or equal”. The used oil was rejected and not to be reused. 3.6.3 Shutting – Down the plant When all the liquid to be dried has passed through the feed system, some distilled water was feed to the atomizer in other to clean the feed pipe and the atomizer disc, and to prevent the plant from being overheated. The power for the air heater was switched off and the supply of the water was gradually reduced to maintain an out.et air temperature at a constant level say 90ooc. When the temperature of the inlet air has decreased to about 130oc, the pump control was turned to minimum. When the inlet temperature as decreased to 80oc, the plant was stopped by turning the atomizer control to it zero position and depressing all the buttons. 3.6.4 Cleaning of the plant Cleaning of the plant was commenced by removing the chamber button and dismantling the cyclone. Then the centrifugal atomizer was started and a generous amount of worm water was pumped through the feed vat, pump, and feed pipe and into the chamber. With most product it was thus possible to clean the feed system and most of the chamber. The rest of the chamber could be normally raised down with worm water. In order to inspect the pump, the cover with the inlet tube was removed and the rubber stator was taking out. The atomizer was dismantled for cleaning as prescribed by the instruction manual. The duct from the chamber bottom to cyclone and the cyclone part was normally raised down with warm water. The sensor for the outlet temperature was removed cleaned with a brush in a warm water. 3.7 Experimental procedure for Nozzle Atomization 3.7.1 Preparations for Nozzle Atomization The round was placed over the air distributor. The plug in the chamber cone was removed and the nozzle atomizer was inserted. The reinforced plastic tube was connected to the lower connection on the atomizer. The air pressure control valve was closed by unscrewing the adjustment spindle. Compressed air was connected to the air pressure control valve if it was not connected permanently. The start – stop button “Nozzle – Atomizer” was activated to switch off the interlocking. 3.7.2 Choice of Air Pressure Before the nozzle atomizer was commenced, it was considered that inlet and outlet temperature at which air pressure the product should be dried. The air pressure was mainly governed by the following factors: powder particle size, feed rate, liquid pressure, viscosity and the object of preventing build – up in the chamber. The nozzle which was provided as standard, is of the syphon type with external mixing. With this nozzle a given feed rate was achieved with widely varying pressures. The guideline given below was used to assist in finding the optimal pressure conditions: increased air pressure results in increased feed rate at a constant liquid pressure, increased air pressure results in smaller particle size at a constant liquid rate and increased viscosity demands and increased air pressure to maintain a constant feed rate. 3.7.3 Starting – Up the Plant The plant was started – up as explained in the procedure for centrifugal atomizer. While the plant was being heated, the compressed air was turned on. The air pressure control valve was adjusted to a pressure of approximately 1 bar applied to the nozzle. The pump control was set at minimum and water was poured into the feed vat (preferably distilled water). When the outlet temperature is approximately 900c, the feed rate slowly increased in order to maintain the outlet temperature constant. 3.7.4 Operating Instructions When the temperatures of the inlet and outlet air has been kept constant for some time at the desired values and the feed vat was nearly empty of water, the vat is fed with the product to be dried (note that the liquid should be filtered in the best possible way before it is poured in the feed vat). The air pressure control valve was adjusted in such a way that the desired pressure is applied to the nozzle and the feed pump was adjusted so that the outlet temperature remains constant. 3.7.5 Shutting – down the plant When the feed vat is almost empty of the product which is being dried, distilled water is poured in. this was done partly in order to clean the feed pipes and the nozzle, and partly in order to avoid the plant from being overheated. Immediately after the distilled has in being poured into the feed vat, the speed of the feed pump was reduced, because the smaller quantity of liquid was atomized (no solids in distilled water). If the feed rate were not reduce when changing from product to water, the outlet temperature will drop causing the chamber to become wet. The current supplied for the air heater was switched off, and the supply of water is gradually reduced keeping the outlet air temperature at a constant level, say 90oc. when the temperature of the inlet air has decreased to approximately 130oc, the water supply is completely turned off. When the inlet air temperature has decreased to 80oc, the compressed air is turned off. The plant is then shut down by depressing all the stop buttons. 3.7.6 Cleaning of the plant The feed vat, pump and feed pipe was cleaned by pumping warm water through the system. During this operation the compressed air supply were slightly opened. The nozzle assembly was removed from chamber and dismantle for cleaning as described in maintenance instruction. The pump was inspected by removing the end cover with the inlet tube and removing the rubber stator. The rest of the plant was cleaned normally by removing the chamber button and dismantling the cyclone and rising the plant into warm water. 3.8 Maintenance plan for the compact spray dryer 3.8.1 Centrifugal Atomizer After 8 hours operation the oil cups of the atomizers are refilled with the ISO VG 32 oil. After 24 hours operation the used oil is removed. After each ended production, the atomizer wheel and the liquid distributor are dismounted. Spindle: After 8000 hours of operation the spindle is dismounted, and new ball bearing are mounted. Atomizer motor: After 12 hour’s operation the ball bearing must be dismounted, cleaned and refilled with new grease. Motor brush, spring, brush holder and commutator must be clean and checked. 3.8.2 Pump module After 500 hours operation, stator is dismounted for cleaning and checked for wear. After 300 hours operation the v-belt is checked for wear and tension. After 6000 hours operation the pump is dismounted and the ball bearings are cleaned and refilled with new grease. The shaft seal is checked for wear, and replace if necessary. D.C. Motor for pump: After 12,000 hour’s operation the ball bearings must be dismounted, cleaned and refilled with new grease. Motor brush, spring, brush holder and commutator must be cleaned and checked. 3.8.3 Electric Air Heater Module After 3000 operation hours the electric air heater must be dismounted and lifted out of the duct. The heating element must be checked and cleaned with compressed air. If there are deposits on the heating elements, they must be washed with hot soapy water and dried before being built-in. 3.8.4 Fan Fan module: -After 3000 hours operation the impeller of the fan is checked for dust deposits. The impeller can be checked by dismounting the cleaning door of the fan. If there are powder deposits on the impeller, it must be cleaned with hot water. Before the fan is washed, the drain plug shall be removed and replaced by a hose connection with 1’ RG, thus enabling the cleaning water to run out of the fan. We also recommend to cover the electric board with folio to prevent water from running into the board. V-belt Drive for fan: After the running in the v-belt must be checked after 3000 operating hours. Data for belt tension is stated in the operating instructions for fan. Ball Bearing for fan: After 2100 operating hours the ball bearing must be lubricated during operation. After 2100 operating hours the ball bearing must be dismounted, checked, cleaned and refilled with new grease. Motor fan belt: After 24000 operating hours, the ball bearings of the motor must be dismounted, checked, cleaned and refilled with new grease. 3.8.5 Drying Chamber When the production with the plant is ended and the drying chamber is cleaned, the door packing and the drying chamber bottom are checked. If the packing are damaged they must be replaced. CHAPTER FOUR 4.0 RESULTS AND DISCUSSION 4.1 Results After running the plant, the water evaporation capacity of the plant at an inlet air temperature of 200oc and outlet temperature of 90oc was approximately 16 kg/hr. And the water evaporation rate of the plant capacity when the inlet air temperature of 3000c and outlet air temperature of 90oc was approximately of 30 kg/hr. Furthermore, it can be said that evaporation capacity is a function of inlet air temperature with outlet temperature. The table of results obtained below shows the evaporation rate at varying inlet air temperatures and outlet air temperature of 90oc, 105oc and 1150c. The feed rate was calculated using the equation below: ---- 3.1 F = feed rate, kg/hr. W = water evaporation rate, kg/hr. TP = total solids in powder, % TF = total solids in feed, % The product used have a solid content of 40% by weight. Moisture content in the powder was 3%. Table 4.1: Evaporation capacity as a function of inlet temperature at 90oc outlet temperature. S/N Inlet air Temp TI oC Evaporation rate at (TO = 90oC) kg/hr. Feed rate kg/hr. 1 150 5.55 9.43 2 175 8.61 14.64 3 200 12.78 21.73 4 225 16.25 27.63 5 250 20.28 34.47 6 275 23.75 40.37 7 300 27.50 46.75 8 325 31.25 53.13 9 350 34.58 58.79 10 375 38.19 64.92 11 400 42.64 72.49 12 425 45.55 77.44 13 450 49.44 84.05 Table 4.2: Evaporation capacity as a function of inlet temperature at 105oc outlet temperature. S/N Inlet air Temp TI oC Evaporation rate at (TO = 105oC) kg/hr. Feed rate kg/hr. 1 175 5.55 9.43 2 200 9.17 15.59 3 225 12.78 21.73 4 250 16.53 28.10 5 275 20.28 34.47 6 300 23.75 40.37 7 325 26.94 45.80 8 350 31.11 52.89 9 375 34.44 58.55 10 400 38.33 65.16 11 425 41.67 70.84 12 450 45.69 77.67 Table 4.3: Evaporation capacity as a function of inlet temperature at 115oc outlet temperature. S/N Inlet air Temp TI oC Evaporation rate at (TO = 115oC) kg/hr. Feed rate kg/hr. 1 200 5.28 8.97 2 225 8.89 15.11 3 250 12.50 21.25 4 275 16.39 27.86 5 300 20.00 34.00 6 325 23.61 40.14 7 350 27.36 46.51 8 375 31.39 53.36 9 400 35.00 59.50 10 450 42.22 71.77 Table 4.4: Relation between operating parameters S/N Alteration Effect 1. Higher atomizer speed Smaller particles 2. Lower atomizer speed Larger particles 3. Higher inlet temperature Higher capacity. Higher water content in powder. 4. Lower inlet temperature Lower capacity. Lower water content in powder. 5. Higher outlet temperature Lower capacity. Lower water content in powder. 6. Lower outlet temperature Higher capacity. Higher water content in powder. 7. Higher total solid content in feed Higher capacity. Higher water content in powder. 8. Lower total solid content in feed Lower capacity. Lower water content in powder. 9. Higher feed temperature Higher capacity. Can have influence on capacity and thus on particle size. Fig 4.1: Relationship between evaporation rates and air inlet temperature at 900C, 105oC and 115o C Fig 4.2: Relationship between feed rate and inlet air temperature at 90oC, 105oC and 115oC. 4.2 Discussion Thirteen runs was done for different inlet air temperature as shown in table 5.1 from 150oC to 450oC at a set outlet temperature of 90o C with interval of 250C. It was observed that as the inlet air temperature increases, the evaporation rate increases steadily at an average interval of 3.68 kg/hr. The feed rate was also calculated using equation 3.1, which shows that there is a need to increase the feed rate as inlet air temperature increases. Therefore increasing the drying rate of the feed. From table 5.2, twelve runs was carried out for different inlet air temperature with value from 175o C to 4500 C at a set outlet temperature of 105o C with interval of 250 C. It was observed that as the inlet air temperature increases, the evaporation rate increases steadily at an average rate of 3.65 kg/hr. When the feed rate was calculated, it was observed that drying rate increases at steady state with increase in inlet temperature. Furthermore, table 5.3 shows how the inlet air temperature varies from 200o C to 4500 C with interval of 25o C at a set outlet temperature of 115o C. The results obtained was quite similar to the results obtained in table 5.1 and table 5.2. Lastly, the graphs in fig. 5.1 and fig 5.2 show a critical relationship between the air inlet temperature and evaporation rate and feed rate respectively. These graphs shows a linear relationship. Table 5.4 also shows the relationship between operating parameters and how it affects the initial operating conditions. CHAPTER FIVE 5.0 CONCLUSION AND RECOMMENDATIONS 5.1 Conclusion In conclusion, it can be deduced that the rate of evaporation is a function of the inlet air temperature and the feed concentration. The particle size was influenced by the speed of the atomizer and the quantity of production per time was a function of the inlet temperature, feed rate and concentration of feed. With higher feed temperature, there was an influence on capacity and thus particle size. An alteration in the outlet temperature has ten (10) times as much influence on the water content in the powder. 5.2 Recommendation After carrying out troubleshooting, installation and performance on the compact spray dryer, the following recommendations were obtained: Proper and accurate maintenance should be carried out regularly on the machine. Further research should be carried out using different sample to fully test the efficiency of the machine. The pump and centrifugal atomizer module should be fixed prior to running more experiment. A compressor should be fixed so as to test the performance of the nozzle atomizer. The chimney should also be constructed so as to take out particles in the exhaust. REFERENCE Arun, S. (2011). Spray drying of foods. Singapore: National University of Singapore publications. Barbosa Canovas GV, Vega-Mercado H. 1996. Dehydration of food. New York: Chapman & Hall. BETE® Spray Dry Manual (2005). www.bete.com. Drusch, S. (2007). Sugar beet pectin: A novel emulsifying wall component for Microencapsulation of lipophilic food ingredients by spray-drying. Food Hydrocolloid, 21(7):1223-1228. Dziezak, J.D. (1988). Microencapsulation and Encapsulated Ingredients. Food Technology, 42(4):136-151. Estevinho, B.N., Rocha F., Santos L., and Alves A. (2013). Microencapsulation with chitosan by spray drying for industry applications - A review. Trends in Food Science & Technology 31: 138-155. 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Fundamental analysis of particle formation in spray drying. Powder technology 247: 1 – 7. APPENDIX A Technical Data Capacity The water evaporation rate of the dryer varies with the air temperatures as applied to the drying process. Inlet Temperature: 300o C 200o C (570o F) (390o F) Outlet Temperature: 90o C 90o C (195o F) (195o F) Evaporation rate: 28 kg/hr. 13 kg/hr. (60 lbs/hr.) (28 lbs/hr.) Air Heater Air inlet temperature: Variable up to 3000 C (570o F) Power at 300o C: 42 kw Centrifugal Atomizer Disc speed: Variable up to 35 000 min-1 Disc diameter: 100 mm Nozzle Atomizer Throughput: Variable up to 60 l/hr. Air pressure (max.): 4 bar (60 psig) Air consumption (max.): 250 l/min. (8.8 SCFM) Installed Motors Atomizer motor: 0.9 kw Feed pump motor: 0.29 kw Fan motor: 2.2 kw Chamber Diameter Internal: 1.25 m (49 inch) Floor Space 1.5 m x 2.0m (4’11’’ x 6’7’’) Height Without Atomizer: 2.7 m (8’11’’) With Atomizer installed: 3.1 m (10’2’’) For removing atomizer: 3.6 m (11’10’’) Recommended free height: 4.0 m (13’2’’) Weight: 1100 kg (2400 lbs) Feed rate calculation: ---- 3.1 F = feed rate, kg/hr. W = water evaporation rate, kg/hr. TP = total solids in powder, % TF = total solids in feed, % Plate 2.8: Control panel of the Spray Dryer APPENDIX B 43