Design of an Efficient Drying System – Project | BAE 4012, Study Guides, Projects, Research of Engineering

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Design of an Efficient Drying System Kyle Dollins Becca Hoey Michael Matousek Adviser: Dr. Paul Weckler Technical Adviser: Dr. Tim Bowser Prepared for S & S Farms BAE 4012 Fall 2007 Table of Contents Problem Introduction...............................................................................................3 Previous Work..........................................................................................................5 Patents....................................................................................................................................5 Sales Literature.....................................................................................................................7 Research Articles..................................................................................................................9 Design Specifications.............................................................................................12 Design Concepts.....................................................................................................12 Concept #1 Peerless Dryer Modification..........................................................................13 Concept #2 Modified Air Flow and Temperature...........................................................14 Concept #3 Air-to-Air Heat Exchanger............................................................................15 Concept #4 Continuous Flow Dryer..................................................................................16 Concept #5 Recirculation.....................................................................................................16 Cost Analysis...........................................................................................................20 Peerless Dryer Modification Cost Summary.......................................................................20 Modified Air Flow Cost Summary....................................................................................20 Air-to-Air Heat Exchanger Cost Summary......................................................................20 Continuous Flow Dryer Cost Summary...........................................................................21 Recirculationn to Dryer Cost Summary..............................................................................21 Alternating Bin Recirculation to Bin Cost Summary.........................................................21 Next Semester.........................................................................................................22 Works Cited.............................................................................................................24 Appendix A.............................................................................................................26 Appendix B.............................................................................................................31 Problem Introduction...............................................................................................3 Previous Work..........................................................................................................5 Patents....................................................................................................................................5 Sales Literature.....................................................................................................................7 Research Articles..................................................................................................................9 Design Specifications.............................................................................................12 2 associated with the incorporation of our solution. Reducing the maintenance will reduce the labor cost and the possibility of slowing the process. Previous Work Patents Spicy Solutions started researching patents to determine what was in use and if our design ideas would infringe on existing patents. We found several patents on the topic, but none presented much concern. Below is the team’s understanding of the patents that were found. US Patent Application No. 20,070,160,729 Capsinoid-Containing Dried Chili Pepper Product and Method of Drying the Same Date of Issue: July 12, 2007 The purpose of this patent is to discover suitable drying conditions that prevent the decomposition of capsinoid compounds and increase the yield when drying capsinoid-containing chili peppers. Another purpose is to maintain the stability of capsinoids during drying of chili peppers. Chili peppers cut either before or during drying have increased surface area and ruptured outer skin. These conditions accelerate the evaporation of internal moisture, enhance drying efficiency and permit rapid drying. Frequent and uniform mixing and stirring causes moisture to evaporate evenly from the peppers, thus preventing uneven heating. The patent covers stirring at least once per hour. An air speed of 0.3 m/s or greater works well for batch drying. An air speed of 0.2 m/s or greater works well for continuous drying. An air temperature of 65°C to 80°C is used. The hot air is directed through the bulk chili pepper material. These conditions prevent excessive heating of capsinoid and thus suitably prevented it from decomposing. The patent covers drying Manganji peppers, Shishito peppers, Fushimi Amanaga peppers, and CH-19 Sweet peppers. It specifies that weight of peppers is reduced to less than 5 20% and the moisture content is reduced to less than 10% of the raw fruit. It covers the following driers: band-type, fluidized bed-type, draft-type, rotating-type, spraying-type, stirring- type, box-type, moving bed-type or drum-type. It further covers drying with a convective heat- transfer dryer, using either continuous stirring or stirring at least once an hour. U.S. Patent No. 7,137,580 System and method for pulverizing and extracting moisture The patent covers an apparatus for pulverizing material and extracting moisture from material. It is composed of an inlet tube, a venturi coupled to the inlet tube, an airflow generator to generate airflow with an inlet aperture, an axel coupled to the airflow generator, a balancer coupled to the axel to compensate for imbalance in the axel during rotation, and a housing at least partially encompassing the airflow generator. An outlet communicates with the input aperture, the airflow generator communicates with the venturi to direct the airflow through the venturi, and toward the input aperture. The material introduced into the airflow passes through the venturi and is subject to pulverization and moisture extraction. A material flow rate is measured by an acoustic emission sensor, which receives the resonant frequencies generated by the material passing through the airflow generator. The material flow rate is measured to avoid overloading the system. This patent is specific to the balancing apparatuses and methods for the rotating axel. U.S. Patent No. 7,059,550 System and method for pulverizing and extracting moisture This patent is relevant to the same system as the previous patent, U.S. Patent 7,137,580. This patent is specific to the apparatuses that create, direct, and handle the air flow. It also covers the heat generation, pulverizing system, and material feed equipment. It contains the 6 elaborate process of material flowing through the system. It also contains the communication between components. U.S. Patent No. 7,040,557 System and method for pulverizing and extracting moisture This patent is relevant to the same system as the previous patent, U.S. Patent 7,137,580. This patent is specific to the methods and apparatuses for the sensors, controllers, acoustic emission sensor, and the communication between apparatuses. Sales Literature Market research was an important part of the team’s research. We were interesting in determining what is available and if the client is using the best product. Listed below are the results of our market research. Peerless Dryers Spicy Solutions looked at this information because the client is currently using the Peerless regular dryers. Other dryers that Peerless makes are whisper dryers, quiet dryers, which are a lot like the regular dryers but they produce less noise, and semi dryers, which have been tested to dry open- top semi containers in the same way as the wagon dryers. GT Mfg. Inc Grain Dryer Specs. These dryers are recirculating batch grain dryers that would not be feasible for our project because of the set up of the dryers. They are geared more towards 7 Figure 1. Peerless 103 Dual 3- Phase Dryer Figure 2. GT Mfg. Inc. Grain Dryer retention capabilities. The fan sucks air through the solar collector and then into the containers with the onions or hay bales. These drying options will not work for this project most likely because the air used will not be warm enough to dry the peppers to the desired moisture content without a heater attached to the process. The article Dehydration of Food Crops Using a Solar Dryer with Convective Heat Flow discussed the possible design based on the principles of convective heat flow and using it to dry food crops. By using a solar collector an ambient air of 32°C and relative humidity of 80% could be heated to 45°C at 40% relative humidity (Ayensu 1997). The crops were able to reach moisture content of <14%. The article also discusses the factor of free water in the product compared to the bound water. The use of solar energy is not applicable to this project given the season when the drying takes place. The article Design and Performance of an Air Collector for Industrial Crop Dehydration reviews a test of the operation of unglazed and single-glazed solar collectors used to heat air. The collectors were tested in a range of sizes and lengths so that the pressure drops and heat transfer rates would vary (Niles 1978). Although this article is geared to industrial size crop drying operations, it introduced the possibility of solar panels to reduce some of the cost of natural gas that the client is currently facing. Once again, the use of solar energy would not be cost effective for this project. 10 Figure 5. Dryer Set Up The paper Curing Peanuts Using Continuous Flow Dryers explained the results from a comparison of a single-pass continuous flow dryer, a recalculating batch dryer and a wagon drying process (Butts 2001). The study monitored drying time and quality of the peanuts after being dried. The results can be applied to the drying of peppers. The paper concluded that “using the continuous flow dryers were dried at a much faster rate than conventionally-cured peanuts” (Butts 2001). This information is applicable to this project since peppers are dried in a similar way to peanuts. The presentation titled Effects of Drying Procedure, Cultivar, and Harvest Number on Capsaicin Levels in Dried Jalapeno Peppers discusses a study on how to harvest and process pepper to maintain the maximum amount of capsaicin (Pordesimo 2001). The study focused on the effects of cultivation, harvesting time and drying. The study concluded that a change in drying temperature “did not affect the concentration of total capsinoids in dried jalapeno peppers” (Pordesimo 2001). The information from this study can be easily applied to our study because it focused on non-food use peppers. The article Modelling of Thin-Layer Drying Kinetics of Red Chillies investigates which temperature works best for drying peppers in a thin-layer dryer. The temperature range that was tested was 50-65°C (Kaleemullah 2006). The study took into consideration, capsaicin content, color, and drying time. The results showed that the optimal drying temperature was 55°C. This article is useful to the project if the final solution implements a thin layer drying method. The experiment titled Drying of Red Pepper (Capsicum Annuum): Water Desorption and Quality dried red peppers at different air-drying temperatures. The results of the experiment show that the air drying temperature influenced the final quality of the dried red pepper (Simal 2005). It was also found an optimum range of drying for peppers to be within 50°C and 70°C 11 (Simal 2005). The information from this experiment will be helpful when the team begins looking at desired temperature ranges for the solution. The Web site titled Drying Chili Peppers was helpful to the team by describing several traditional small scale methods for drying chilies. The team did notice that typically these methods resulted in a moisture content in the chili from 8% to 12%, which is not low enough for the desired process (Sanut). Even though the Web site mentioned that the methods could be adapted to large scale processes, it does not reduce the moisture content enough to be applicable to this project. Design Specifications • Reduce fuel consumption of drying process • Decrease dependence on manual labor • Meet current production rates • Simple operation Design Concepts Spicy Solutions is presenting S&S Farms with five design concepts. These concepts are discussed in more details below. The five concepts do not result in the same process efficiency, and the five concepts vary greatly in cost. 1. Peerless Dryer Modification a. Modified Burner b. Modified Bed Depth 2. Modified Air Flow and Temperature 3. Air-to-Air Heat Exchanger 4. Continuous Flow Dryer 12 by the high humidity heated air before it ever reaches the dryers burner. To gain the most efficiency, the building must be enclosed, so the exhaust air is forced around the intake tubes and not blown directly into the environment by the wind. The air-to-air heat exchanger can be placed in three locations. The first location allows the intake tube to hang from the rafters of the building. This allows the bin to move in and out without moving the heat exchanger. The second location is placing the heat exchanger on top of the drying bed. This option requires the operator to remove each exchanger before the bin can be moved. The third location is to permanently place the exchanger in the bins and allow the duct to be connected to the bin, similar to how the dryer connects to the current bins. Locating the heat exchanger in the building’s rafters requires no modification the current dryer bins. The only ducting needed for this set-up is to the dryer’s intake. Locating the heat exchanger on top of the drying bed requires flexible tubing that can be moved or lifted off the bin as easily as possible. Permanently locating the heat exchanger inside the drying bin requires additional ducting to be connected to the drying bin that is flexible and can be removed easily. Concept #4 Continuous Flow Dryer In the continuous flow dryer the peppers are conveyed through different temperature airstreams. Belt dryers can also provide agitation by designing multiple pass dryers. A multiple pass continuous belt drying system can use the concept of recirculation easily by allowing the wet peppers to enter into the top of the dryer and the dry peppers to exit the bottom. The heated air can then be forced form the bottom of the dryer to the top. The hot dry air passes through the semi-dry 15 Figure 7. Belt-o-matic Dryer. peppers to finish the drying process. The air then passes through a bed of wet peppers because it still has the ability to remove moisture. Figure 7. illustrates this process. Designing a dryer that is capable of drying at the same rate as the traditional drying system is crucial. For this design, it would be ideal for the dryer’s capacity to be more than what is currently being produced to accommodate the future technological advances in the growing, milling and harvesting processes. Concept #5 Recirculation Air can hold a certain amount of moisture before it reaches 100 percent relative humidity, a condition known as saturation. The amount of moisture air can hold depends on the temperature of the air, hotter air can hold more moisture than colder air. Thus, heating the air that is passed through the peppers allows for more moisture to be removed before the air reaches saturation. Figure 8 illustrates how the relative humidity of the exhaust air from the bins decreases as the peppers dry. As the drying process proceeds, the exhaust air from the bins has the ability to absorb more moisture. The recirculation concept involves reusing exhaust air from the bins that has yet to reach saturation. This concept is based on utilizing as much heat as possible from the air. Doing so should decrease the amount of natural gas needed to dry the peppers, thus reducing cost. Two methods were developed: recirculation to dryer and alternating bin recirculation. 16 Exhaust Air Humidity Throughout Drying Process Time H u m id it y Saturated Air Exiting Air Humidity ` Figure 8. Air Humidity of Exhaust Air from Bin Throughout Drying Process To Dryer The recirculation to the dryer is done by conveying exhaust air from the bins back into the dryer. The air can be conveyed by an air duct. This material could be the same flexible material used in the dryer air ducts. A metal or hard plastic could also be used. The ducting would be suspended from the frame of the roof over the bins. The frame of the roof would need to support the weight of the ducting in order to suspend it. The fan from the dryer will create suction to move the air through the ducting. Figure 9 illustrates this method. It shows a dryer blowing air into two bins and the air exhaust from the bin blowing back into the air intake of the dryer. Figure 9. Exhaust Air Recirculation to Dryer Another unknown is whether recirculated air will need to be exhausted to the environment and new outside air be added to the recirculation. This depends on what 17 Partially Dry Partially Dry Partially Dry Partially Dry Partially Dry Partially Dry Cost Analysis Peerless Dryer Modification Cost Summary The Peerless Dryer Modification uses the majority of current drying components and current drying bins. This concept would result in increased burner and drying efficiency, resulting in a decrease of fuel consumption. A new burner costs $800 per burner and $200 per drying bin to increase bed depth. Modified Air Flow Cost Summary The MAT system, when implemented into the drying of hops, resulted in a twenty percent savings of fuel. A new burner costs $800, the burner and fan controllers costs $6,000 and the humidity sensor costs $200. Air-to-Air Heat Exchanger Cost Summary The estimated cost associated with the air-to-air heat exchanger is dependent on the location of the heat exchanger. The different locations require a considerable difference in exchanger tube length. The concept requires the already built barns to be enclosed this would cost $5,000. Spicy Solutions estimated the cost of exchanger tubes would be $5,000. Continuous Flow Dryer Cost Summary The continuous flow dryer is the most expensive concept, because of the capital investment. A new custom built continuous flow dryer from Belt-o-matic dryers cost $500,000 to $750,000. This dryer is designed to be used in the final drying process of packaged food 20 production. This quality of food grade drying is not required for our pepper drying, but it does have the capacity to dry to the reduced moisture of the process. Recirculation to Dryer Cost Summary Air ducts are estimated at $225 per dryer. Humidity sensors are estimated to cost $200, for an equivalent $400 per dryer. All components of this method are estimated to cost $625 per dryer, for a total cost of $13,750. Recirculation to Bin Cost Summary Additional fans are estimated to cost $325 per dryer, and the air ducts are estimated at $225. This method is estimated to cost about $550 per dryer, for a total of $12,100 for all 22 dryers. Table 1 contains a summary of estimated costs for each concept. Table 1. Cost Summary of Design Concepts Concept Cost Peerless Dryer Modification $1,000/dryer Modified Airflow and Temperature $7,000/dryer Air-To-Air Heat Exchanger $450/dryer Continuous Flow Dryer $500,000 Recirculation to Dryer $625/dryer Alternating Bin Recirculation $550/dryer Next Semester Spicy Solutions has outlined several tasks that will be completed next semester. Some of these tasks are explained in further detail below. A detailed Gantt chart is located in Appendix B. Burner Efficiency Determination 21 Spicy Solutions has decided to determine the efficiency of the current burners. The results of this test will allow us to calculate potential cost savings for buying new burners. The following will be measured in this test: temperature and humidity of ambient air, air entering the bin, and air exiting the bin; pressure at the inlet of the dryer and entrance of the bin; flow rate of gas entering burner. The temperature and humidity data will be recorded throughout the entire drying period of a bin of peppers. The other data should be consistent and does not need to be taken constantly. Continue Component Cost Search Spicy Solutions plans to continue searching for more cost effective components of the design concepts to reduce the cost to the client. As designs become more specific, the required components can be better selected from a range of possibilities. Our cost can then change from a rough estimate to a good estimate. Choose a Design Concept Spicy Solutions will select a final design concept using client feedback, results from tests, and costs savings. The potential cost savings can be calculated after we perform our planned test. 22 Appendix A Patents Search 25 26 27