MATHEMATICAL MODELING OF DRYING KINETICS OF CORN IN ELECTRON FIRED FLUIDIZED BED DRYER

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1 International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 6, June 2017, pp , Article ID: IJMET_08_06_006 Available online at ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed MATHEMATICAL MODELING OF DRYING KINETICS OF CORN IN ELECTRON FIRED FLUIDIZED BED DRYER Prof. Dayanand N. Deomore Asst. Prof. D. Y. Patil College of Engineering and Technology, Kolhapur Prof. R. B. Yarasu Associate Professor, Government College of Engineering, Nagpur ABSTRACT The conventional method of electrical heating is replaced by electron firing system. The drying kinetics of wheat is studied using electron fired fluidized bed dryer. The results are simulated by using ANSYS. It was observed that the graphs are in agreement with each other. Therefore the new proposed electronic firing system can be employed instead of electrical firing. It was observed that The drop in relative humidity for Conventional system is % for temp reaching upto 70 C in 175 C for 10 psi, while for electron firing system it is 37.88% and temp reaches to 73.1 C in 174 sec for pressure drop of psi. It can be concluded from the results that for the grins like corn with high initial moisture content, electron firing system is more efficient than the conventional electric heating system. Key words: Fluidized Bed, Mathematical Modelling, Simulation. Cite this Article: Prof. Dayanand N. Deomore and Prof. R. B. Yarasu. Mathematical Modeling of Drying Kinetics of Corn in Electron Fired Fluidized Bed Dryer. International Journal of Mechanical Engineering and Technology, 8(6), 2017, pp INTRODUCTION In its simplest terms, fluidization is a physical process that transforms solid particles into a fluidized state through suspension in a liquid or gas. Fluidization is most commonly considered with gas-solid systems in mind, but the use of liquid-solid contacting is also a very important research area. Of all the unit operations used by the process industries, drying is probably the oldest and the most common one found in diverse fields such as agricultural, chemical, food, pharmaceutical, pulp and paper, mineral, polymer, ceramic, and textile industries. Industrial dryers consume a significant fraction of the total energy used in many manufacturing process on average some 12%. For an individual dryer, energy costs account for the bulk of the overall costs, typically some 60-70%[1].The strategy of modeling followed 51 editor@iaeme.com

2 Mathematical Modeling of Drying Kinetics of Corn in Electron Fired Fluidized Bed Dryer by system optimization and overall experimental validation of the results is a cost-effective and efficient method for furthering drying technology. Electron firing is a novel concept. Conventionally the air is heated by means of electrical heating and the hot air is flown through the bed comprising drying material. In electron firing air is flown over electrodes which will carry free electrons along with it. When the electrons come in contact with bio-material (wheat in our case), due to effect of ionization heat is generated which in turn is responsible for drying of grains. The modeling is done by assuming the physics behind this process by using ANSYS and the results were compared with experimental results obtained by conventional electrical heating system. Also mathematical modeling is done for the same parameters by using MATLAB. All the results were compared with each other to check the feasibility of employing electron firing system. 2. ELECTRON FIRING SYSTEM Figure 1 Electron Firing Concept The air bombarded with fired electron makes the ionization effect, which makes the biomass to dry without any damage in its bio properties[2]. Figure 1 incorporated with electron direction, its bombardment on biomass body and related fire point. This effect remain for some specific time for specific area, which increases the specific heat area of biomass solid for some specific time period, and this particular area makes more heat gain from surrounding for some specific time. Independent of time component the area makes solid mass to gain heat around the mass. This also makes solid mass to gain equal heat in all direction editor@iaeme.com

3 Prof. Dayanand N. Deomore and Prof. R. B. Yarasu Figure 2 Electron Fired Fluidized Bed Dryer Figure 3 Combustion Chamber The model was designed according to the theory as shown in figure 2. It comprise of blower, bed column, electron firing chamber, feeder and cyclone separator. Figure 3 shows the electron firing chamber which comprise of electrodes placed in the way of flowing air. 3. EXPERIMENTAL SETUP For present study a laboratory scale fluidized bed dryer system was fabricated. The schematic of the fabricated system is shown in figure4 mainly consisting of a fluidized bed column, electric heater and blower. Air is supplied via a root blower and then passed through a Nichrome heater. The fluidization air was supplied by a blower with flow rate measured by air flow sensor connected at the outlet of blower. The orifice plate for fluid flow in closed conduits was designed as per ASME standards. Fluidization air s temperature was measured to be approximately 40 C. This value was the steady-state discharge temperature of the blower. An 8.0% open area perforated plate with 2.0- mm diameter orifices drilled on a 6.0- mm square pitch was used to distribute the gas across the bed inlet. The air then enters the plenum filled with rings where air flow is distributed before passing through the distributor plate. The distributor plate is constructed from cast iron of 6 mm thickness, with 25 holes of 2 mm diameter arranged in a triangular pattern, resulting in 8 % free area. The pressure drop across the distributor plate and the bed was measured by another differential transducer. The bed pressure drop was measured across the freeboard and 3 cm above the distributor plate. The measurements of pressure drop were collected at 400 Hz. This is to ensure that all frequencies relevant to the analysis of the hydrodynamics are captured. The data was displayed in an LCD display unit attached to the system. And readings were tabulated at regular interval of time. The cylinder bed column is made of Cast iron with 7mm wall thickness, 175mm internal diameter with overall length of 1200 mm. A digital thermometer was used to measure the temperature at inlet and outlet of the bed. The wall temperature was measured at 60 mm above the distributor plate on the inner side of the column. All digital thermometers were same type and specifications are given in Table 1. The relative humidity of exit air was measured by using humidity transducer located before the exit. It is calibrated using solutions with different vapor pressures and equilibrium relative humidity. The specifications of relative humidity are given in Table editor@iaeme.com

4 Mathematical Modeling of Drying Kinetics of Corn in Electron Fired Fluidized Bed Dryer Table 1 Specifications of digital thermometers Type Material Probe Diameter DS18B20 digital thermometer High quality stainless steel tube encapsulation Maximum Temperature Length Junction Type 1/8 inch C 4 inch enclosed Table 2 Specifications of humidity transducer Type RH- Range Temperature Accuracy Sensor Output Signal DHT % C ±5% RH DFRobot DHT ma The moisture content of the wheat and corn was determined by taking samples from the bed. These samples were taken from the middle region of a well-mixed bed therefore assuming spatial homogeneity of moisture in the bed. The granule samples were analyzed for moisture content with moisture analyzer. 4. MATERIAL AND METHODOLOGY 4.1. Corn Second material used for the drying test was shelled corn. The corn kernel is found to have a shape factor close to the unity with an average diameter of 6.45 mm and the density of 1260 Kg/m 3. The moisture diffusion coefficient (D) of corn is given by [3] = exp ( ) Thermal Conductivity (k t ) and Specific Heat (C P ) of corn are given as [4] = = Method of Grain Conditioning The grains taken for the experiment had moisture content of 10-18% on a dry basis initially. In order to raise the moisture content to 21-40% and simulate condition of newly harvested grain, water was added to the material. The conditioning procedure used in this work was carried out by filling a plastic bucket with necessary amount of grain. The calculated amount of water was added to raise the moisture content to the desired value and at the same time the grain was mixed with a mechanical agitator. The grain was stored at room temperature for 48 hours with repeated mixing at periodic intervals. The bucket of the grain is then stored in a refrigerator at 5-7 degree centigrade until drying time to prevent degradation or germination of the grain. Generally, the storage time was 5 days and after that sample was used in the experiment editor@iaeme.com

5 Prof. Dayanand N. Deomore and Prof. R. B. Yarasu It should be noted that the lost bed mass due to drying was not made up between moisture content experiments. Although these changes are considerable, minimum fluidization velocity and bed voidage are particle properties and therefore not influenced by bed mass Moisture Content Determination of the Grain Before starting experiment moisture content of the grains were determined. The moisture content of the grain was determined by a standard method developed by American Society of Agricultural Engineers, ASAE standard: S Table 3 shows the sample weight and temperature and time of drying. Table 3 ASAE standard for drying of the grains Grain Weight of Sample Temperature(± 0 C) Drying Time Wheat 10 g hours Corn 15 g hours Weights of the dry gains were taken before and after conditioning for determination of the moisture content of the gain. All moisture content refer to in this work are on a dry basis. The moisture content o dry basis is calculated by: = (3) W B = Weight of grain before drying W A = Weight of grain after drying M= Moisture content of a grain on a dry basis The moisture content on a wet basis is given by = (4) 4.4. Experimental Conditions Experiments were carried out at wheat moisture contents of 22 to 5 +/- 1 wt. %( decreasing in 5 wt. % increments). This represents the typical range of moisture experienced during drying of wheat and shell corn seed granule. Starting with 10 gm of weight at 20 wt. % moisture, static pressure drop measurements were collected over the velocity range of 0.04 to 0.8 m/s. The data collected at each velocity were recorded for two minutes. After each pressure drop versus velocity experiment, a weight sample was taken from the bed and the moisture content was measured to ascertain the change in moisture content that had occurred. After concluding an experiment, the weight granule was then dried to reduce the moisture content to the next desired value. Once this moisture content was achieved, another pressure drop versus velocity experiment was run. This procedure was repeated till a granule moisture content of 5 wt. % was reached. Three batches of weight granule were dried in this manner to check for reproducibility in the pressure drop versus gas velocity experiment was conducted Drying Run Procedure Initial moisture content of the sample was determined before drying. In order to attain a uniform working condition, hot air is blown through the bed for five minutes before charging with the material. The air supply and power to heater was turned off as bed reached required temperature, the material was charged into bed as quickly as possible. The air supply and heat power is then reinstated and the pressure drop across the distributor and the bed at the corresponding gas velocity was measured. Temperature, pressure, humidity, and velocity are taken continuously at regular interval of time through LCD display attached to the system editor@iaeme.com

6 Mathematical Modeling of Drying Kinetics of Corn in Electron Fired Fluidized Bed Dryer Since the digital thermometers and the humidity transducer were exposed to hot air before the start of the drying process, there might be some experimental errors in the initial reading of them. 5. RESULTS AND DISCUSSION 5.1. Experimental Results Table 4 Experimental Results Obtained for Corn VALUES TEMPERATURES 30 0 C 40 0 C 50 0 C 60 0 C 70 0 C Time (sec) Relative Humidity At Bed Height 80% 75% 63% 63% 53% Relative Humidity Of Exit Air 60% 58% 53% 52% 48% Pressure ( psi) Results Obtained by CFD Figure 7 Ionization of Electrons Figure 8 Interaction of Free Electrons with bio-mass Figure 7 shows, when the air is passed through the electrodes, it carries free electrons with it. The mathematical equations are used to simulate the phenomenon in ANSYS. When the electrons come in contact with bio-mass, they emit heat energy. The rise in temperature is seen to be C. Figure 8 shows the relative humidity of the air which in turn is responsible for drying of grain editor@iaeme.com

7 Prof. Dayanand N. Deomore and Prof. R. B. Yarasu Figure 9 Temperature and Relative Humidity After 2 sec Various trials are run by using the concept of electronic firing. The first trial is after 2 sec when the temperature of grain is C and the relative humidity is 81.25%. The results are shown in figure 9 Figure 10 Temperature and Relative Humidity after 80 sec From figure 10 it is clear that with time the temperature of grain goes on increasing while the relative humidity goes on decreasing. after 80 sec of trials run the temperature is raised to C while the relative humidity is dropped to % editor@iaeme.com

8 Mathematical Modeling of Drying Kinetics of Corn in Electron Fired Fluidized Bed Dryer Table 5 Results Obtained from CFD analysis of Electron Fired System CFD Results for Corn TEMPERATURES VALUES 30 0 C C C C C C Time (sec) Relative Humidity At Bed Height 83.03% 68.36% 72.31% 61.03% 58.34% 54.07% Pressure ( psi) CONCLUSIONS The drop in relative humidity for Conventional system is % in 174 sec, while for electron firing system it is 37.88% in 175 sec. The drop in relative humidity for Conventional system is % for temp reaching upto 70 0 C in 175 C, while for electron firing system it is 37.88% and temp reaches to C in 174 sec. The drop in relative humidity for Conventional system is % for 10 psi, while for electron firing system it is 37.88% for Therefore we can conclude for the High initial moisture content grains like corn, electron firing system shows good results. REFERENCES [1] R. E. Bahu, "Energy Consumption in Dryer Design," Elsevier Science Publishers, pp , [2] D. C. Joy, " [Online]. Available: [Accessed ]. [3] S. T. Chu and A. Hustrulid, "Numerical Solution of Diffusion Equations," Trans. ASAE, vol. 11, pp , [4] E. A. Kazarian and C. W. Hall, "Thermal Properties of Grain," Transaction of the ASAE, vol. 8, pp , [5] D. N. Deomore and R. B. Yarasu, "Mathematical Modelling and Simulation of Fluidized Bed Drying System," International Journal of Application or Innovation in Engineering & Management (IJAIEM), vol. 6, no. 1, pp , [6] M. Senthil Kumar and S. Vivekanandan, Mathematical Modelling To Predict The Cold Gas Efficiency of Rice Husk in Biomass Gasifier. International Journal of Mechanical Engineering and Technology, 7(6), 2016, pp [7] S. Naga Kishore, T. Venkateswara Rao and M. L.S. Deva Kumar, Furnace Design of 210 MW Circulating Fluidized Bed Boiler-Numerical Investigation, International Journal of Mechanical Engineering and Technology, 8(3), 2017, pp editor@iaeme.com