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1 Advances in Environmental Biology, 7(9): , 2013 ISSN This is a reereed journal and all articles are proessionally screened and reviewed ORIGINAL ARTICLE New Method to Save Energy with CHP Dryer in Drying Agriculture Product Seyed Hashem Samadi, Barat Ghobadian, Gholam Hassan Najai, Ali Motevali Department o Agricultural Machinery Engineering, Agricultural Faculty, Tarbiat Modares University, Jalal Ale Ahmad Highway, Tehran , Iran. Seyed Hashem Samadi, Barat Ghobadian, Gholam Hassan Najai, Ali Motevali; New Method to Save Energy with CHP Dryer in Drying Agriculture Product ABSTRACT About 30% o the energy input in an internal combustion engine is wasted through exhaust gas. Thereore the internal combustion engine is a suitable option to be used in CHP systems, especially at drying agriculture product. In this present work, the waste heat o exhaust gas o an engine-generator was used or the process o orange slice drying. The drying kinetic o orange slices was studied at 4 engine load levels (25, 50, 75, and 100%) and at three levels o drying product thickness (3, 5, and 7mm) in a combined heat and power dryer system. The results showed that drying time decreased signiicantly with increasing the engine load and decreasing thickness o samples. The speciic energy consumption o orange drying varied between kWh/kg water. The lowest value o SEC was observed at 75% engine load and thickness o 3 mm. Also, the perormance o the engine with and without heat recovery is evaluated. It is ound that nearly 11 19% o the total energy rom the uel input is saved using the heat recovery system. Analysis shows that an overall eiciency around 37% could be achieved with systems designed with simultaneous production or heat drying and electricity generation. Considering these results utilization CHP dryer is very suitable or signiicant energy saving perormance. Key words: CHP Dryer, Exhaust Gas Energy, Energy Eiciency, Engine. Introduction Engaging new methods and technologies or energy production with the lack o the disadvantages o classical methods has become common in the world. One o these advanced and eicient technologies is combined heat and power (CHP). Combined Heat and Power, or CHP is the simultaneous production o heat and mechanical power. These systems are requently used to reduce energy consumption in a acility due to the increased energy eiciency [7,26]. CHP is typically used or large towns, universities, hospitals, hotels, oil reineries, chemical plants, paper mills, wastewater treatment plants, enhanced oil recovery wells, drying products and numerous other industrial plants with signiicant heating needs [3,8,20,23]. CHP oers energy and environmental beneits over electric-only and thermal-only systems in both central and distributed power generation applications [13,25]. There are many variations o CHP. Power production options include steam turbines, gas turbines, microturbines, reciprocating engines, stirling engines, and uel cells. Heat recovery typically consists o a waste heat recovery boiler which uses the exhaust gas o power production to heat another luid [5]. Corresponding Author Citrus are tropical and subtropical ruits which with the acreage o 256 hectares and production o about 3.9 million tons per year in Iran are one o the most important horticultural products [22]. The orange is the ruit o the citrus species in the amily Rutaceae. Orange trees are widely grown in tropical and subtropical climates or their sweet ruit, which can be eaten resh or processed to obtain juice [11]. According to statistics published by Agriculture Organization o Iran, more than 30% o horticultural products in Iran beore reaching the consumers are destroyed due to corruption ungi, insects and bacteria [22]. Thereore, ind a good way in reduction o agriculture product waste will be useul or armers and the country. In many cases, drying is probably the oldest method o ood preservation ater harvesting. Drying preserves oods by removing enough moisture rom ood and reduces microbiological activity and minimizes physical and chemical changes during storage to prevent decay and spoilage [6,26]. Due to the importance o drying in post harvesting operations, various drying methods have been developed and used. It has become apparent that energy consumption in industrial drying is relatively high. Hot-air drying is commonly used to dry agriculture product. A major disadvantaged Barat Ghobadian, Department o Agricultural Machinery Engineering, Agricultural Faculty, Tarbiat Modares University, Jalal Ale Ahmad Highway, Tehran , Iran. ghobadib@modares.ac.ir

2 associated with hot air drying is that is high energy consumption [16]. About two-third o the energy input in the internal combustion engine is wasted through exhaust gas and cooling system [19]. Thereore the internal combustion engine is a suitable option to be used in CHP systems, especially at drying agriculture product. Several studies have been carried out in drying o dierent material with waste heat rom the internal combustion engine such as: drying o paddy [4], biomass drying [14,17], pulp and paper mill [10], clay minerals [9] and grand composite [12]. However, there is no complete research on evaluation o energy aspects in the drying o agricultural products using waste heat o exhaust gas o internal consumption engine in dierent condition. In this study, the waste heat o exhaust gas o an internal combustion engine was used or the process o orange slice drying. The objectives o this study are to investigate drying kinetics, energy aspects, comparison o energy consumption and eiciency in the CHP dryer at dierent engine condition. Materials and Methods 2.1. Sample preparation: In this study, orange slices were used to conduct the experiments. The study samples were reshly provided which was purchased rom the local market in Tehran and were stored in the rerigerator at temperature o 4±1 C until the experiments were carried out. AOAC standard [2] was used to determine sample initial moisture content. According to this standard, or determining thyme leaves 2333 moisture content, the samples were placed in a 105 ±1 ºC oven or 3 to 4 hours [2]. Initial moisture content o orange samples 84.7% on a wet basis was obtained. orange were cut into slices o thickness approximately 3, 5 and 7 mm. Each drying process, about 56 g samples were used in each experiment. Drying process was done until the moisture content about 5% on a wet basis was achieved. All measurements were carried out in triplicate Equipment and Methodology: In this study, waste heat rom exhaust an enginegenerator was used or drying process. This dryer consist o a single cylinder IC engine that works with natural gas uel, a generator that produces 2 kw o electricity, gas low meter or measuring uel consumption, a dryer chamber which samples placed in it, a an to remove hot air o the dryer chamber, a digital balance or weighing samples, temperature sensor or measuring temperature and a PC to record hot air temperature and sample weight. The schematic diagram o this CHP dryer system is shown in Fig.1. An engine and a generator with the ollowing speciication were used: Engine Type: single cylinder- 4-stroke Aircooled, power: rpm, Displacement: 196 CC, Bore Stroke: mm, Fuel Types: Natural gas (N), LPG (L), Ignition system: Transistor Coil Ignition (T.C.I). Generator Type: Single-Phase AC Synchronous, Frequency: 50 HZ, Current (A) / DC voltage (V): 12V/8A, Maximum power: 2.3 kw, Power rating: 2 kw. Fig. 1: Schematic diagram o the CHP dryer. Waste heat rom the engine exhaust was directed into the dryer chamber. The produced heat is approaches under the chamber tray directly and the dryer's chamber is warmed. Hot air is circulated inside the chamber and is removed rom the chamber by a an. Engine was run or a ew minutes to reaches steady state condition. The drying experiments were perormed at constant speed and

3 our load levels, 25%, 50%, 75% and ull load (100%). About 56g samples with a thickness o 3, 5 and 7 mm were placed in the dryer chamber and were dried. Samples were weighted by a digital balance (GF-600, A & D, Japan) with ±0.01 accuracy per 5min. Also, air parameters were adjusted by measuring temperature and velocity using thermometer (Lutron, TM-925, Taiwan) and anemometer (Anemometer, Lutron-YK, 80AM, Taiwan) Energy and Eiciency: The energy utilization calculated by applying the irst law o thermodynamics. The total energy consumption was measured every minute during drying process. During the test, dryer energy consumption is calculated using Eq. (1). mq Q t = 3.6 LCV t (1) where, Q t is the uel energy consumption in kwh, m is the uel consumption in 3 m hr which is obtain with a gas low meter, Q LCV is the lower caloriic 3 value o gas uel in MJ m and t is the engine time o operation in hours. The drying kinetics relates the moisture ratio to the drying time: M = M t e MR M 0 M e (2) where, MR is the moisture ratio (dimensionless); M t is the moisture content o drying material at any sampling time (% db), M e is the equilibrium moisture content (% db) and M o is the initial moisture content(% db). The values o M e are relatively small compared to M t and M 0, Thus, the moisture ratio can be calculated as ollows [1]: M MR = M t 0 (3) Many empirical equations are given to describe thin layer drying kinetics o agricultural and ood materials. Midilli et al equation is the most convenient mathematical model o thin layer drying kinetics and the best model to describe the drying curve in CHP dryer [20]: n MR = a exp( kt ) + bt (4) where a, b, n is the dimensionless drying constant and k is the drying constant (min 1 ) that values are estimated rom the experimental data. The calibration 2334 o model parameters was perormed using MATLAB 2011 sotware. Energy o the waste exhaust gases includes a signiicant portion o the uel energy in the IC engine [18]. This portion o energy was used or drying orange samples. With having mass low rate and temperature o the exhaust gases, available energy o the exhaust gases is achieved using equation (5): Q ex = m (1 + AF) C p(tin,ex T out,ex ) t 3600 (5) where, Q ex is the energy o exhaust gases in kwh, T in, ex and T out, ex is the exhaust gas temperature at the inlet and outlet o dryer chamber in ºC respectively, C p is the speciic heat at constant pressure o exhaust gases in J/kg K, m is the mass low rate o uel in m 3 /h and AF is the air to uel ratio. The overall eiciency o the system (CHP eiciency) is deined as the heat used to evaporate moisture rom the ruits divided by the heat input rom uel engine plus the eiciency o single generation: m C (T T ) ex p in,ex out,ex η CHP =η s.g m QLCV 100 (6) η is the eiciency o single generation which is s.g obtained using equation (7): Pel η s.g = mq LCV (7) where, P is the electric power generation (kw). el Another parameter known as speciic energy consumption (SEC) can be used to compare energy eiciencies o dierent types o dryer. The speciic energy consumption is oten used that is equal to the energy required to evaporate a unit weight o water rom the eed [21]: Qt SEC = m w (8) Where, SEC is the speciic energy consumption in kwh/kg, is the amount o water evaporated during the drying process in kg. Energy saving is very important in heat-recovery systems. The energy saving depends on the heattranser rate rom the engine exhaust gas and the total heat-transer rate in the system. The heat saving o the system can be calculated as: Q P rec el Saving Energy = 100 Pel (9)

4 Results and Discussion 3.1. CHP Drying Behavior o Orange Slice: The moisture ratios versus drying time or dierent thickness o orange slice at the selected engine loads are shown in Figs. 2-5, respectively. Also, a comparison between experimental and predicted dying curve (Midilli et al) or orange slice revealed a close (R2=0.99) agreement or dierent dying condition. Simulation has been used as preliminary evaluation o CHP dying. It is clearly seen rom Figures with increasing in engine loads, at constant sample thickness, the time needed to reach equilibrium moisture content was reduced. In thickness o 3 mm, the total drying times to reach the inal moisture content or the orange sample were 225, 190, 155 and 140 min at 25, 50, 75, and 100 W, respectively. The exhaust gas temperature and low rate with increasing the engine load is increased. The higher temperatures o produce inside provide a larger water vapor pressure deicit. At a high engine loads, the temperature proile o the orange sample continuously rises aster than that in the case engine loads. The temperature in the dryer chamber at 25%, 50%, 75% and ull load is approximately 50, 65, 80 and 95, respectively. Also the eects o sample thickness on the drying behavior were studied. It is ound that, the drying time increases as the product becomes thicker. The reason is that, as the product s thickness decreases moisture transer rom the body to the surace was asted, thereore the drying time was decreased [15,24] Energy consumption and eiciency system: 2335 Figs. 6 show the useul energy in CHP dryer in dierent operating condition. In this system, useul energy includes the electric energy and the heat recovery energy rom the engine that was used or drying process. It is seen that at each engine loads, total useul energy increases with increasing sample thickness because drying time has been increased. With increasing drying processes, the available useul energy that is pulse electrical energy and the heat recovery energy was increased. Also, the maximum useul energy was occurred the high loads o engine (75 and 100%). For high loads, the drying temperature and the mass low rate o exhaust gases is higher as compared to other loads thereore the heat recovery energy was increased. Fig. 7 shows the comparison o the system eiciency in the dierent operating condition. It can be seen that the energy eiciency (electrical and overall) is low and increases with the increasing engine load. When the engine load is greater than hal load, the energy eiciency reaches a high level. It is observed rom Fig. 7 that as the engine load is increased rom 25% to 75%, the overall eiciency is increased rom a minimum 22.32% to a maximum 37.94% and electrical eiciency is increased rom a minimum 7.5% to a maximum 17.44%. It turns out that the electrical and overall eiciency is highest at engine load o 75% due to reducing the primary energy consumption and high available useul energy. In the ull load o engine, the system eiciency is lower than that o 75% engine load. This is mainly because, uel consumption in ull load is extremely increased. Fig. 2: Drying curves o orange slice based on Midilli et al model and the experiment o CHP drying at dierent thickness when engine load is 25%.

5 2336 Fig. 3: Drying curves o orange slice based on Midilli et al model and the experiment o CHP drying at dierent thickness when engine load is 50%. Fig. 4: Drying curves o orange slice based on Midilli et al model and the experiment o CHP drying at dierent thickness when engine load is 75%. Energy eiciency at the dierent thickness o the samples nearly equal each other. The speciic energy consumption (SEC) o the drying process at dierent conditions to compare energy drying at dierent thickness and engine loads, were used. The speciic energy consumption o the drying process at dierent conditions is showed in ig.8. It was ound that speciic energy consumption decreased with an increase in the thickness o sample, as expected. The SEC was in the range o kWh/kg water. The lowest value o SEC was observed at 75% engine load and thickness o 3 mm while the maximum o SEC was at ull load and thickness o 7mm. This is due to the act that higher engine load

6 led to a higher temperature o drying process. Thereore, in the thinner sample and higher engine load drying time was reduced. The higher rate o water evaporation led to a lower speciic energy consumption. Also, at the ull load although the drying time was reduced, but the uel consumption and hence speciic energy consumption was increased. The percentage energy saved due to the integrated heat recovery system at dierent load 2337 conditions is given in Fig. 9. Compared with the single systems (only electricity generation), the energy-saving rate o this CHP dryer system can reach the range o % in various engine load. Also, it is seen that the energy saved was increased at higher loads due to the shorter duration o the drying process. Although, at the ull load the drying time was reduced, but the uel consumption was increased and hence energy saved was decreased than that all other engine loads conditions. Fig. 5: Drying curves o orange slice based on Midilli et al model and the experiment o CHP drying at dierent thickness when engine load is 100%. Fig. 6: Total useul energy in the CHP dryer at dierent thickness and engine loads.

7 2338 Fig. 7: Overall and electrical eiciency at dierent thickness and engine loads. Fig. 8: Speciic energy requirement or orange drying at dierent thickness and engine loads.

8 2339 Fig. 9: Percentage energy saved at dierent loads. 4. Conclusions: The exhaust gas o an internal combustion engine carries a lot o heat and this energy can be recovered and this energy can be utilized or drying agriculture product. In the present work, the drying kinetics and energy parameters o CHP dryer or orange sample was evaluated under various operating conditions o engine. According to the result, rate o water evaporation increased signiicantly with increasing engine load and decreasing sample thickness. The minimum o drying time was ound or thickness o 3 mm o samples and engine ull loads. Also, in the present investigation, energy and eiciently o CHP dryer was analyzed in various engine loads. This work it is concluded that, using application o the heat recovery system, system eiciency was increased to 37.94%. It is observed rom the energy analysis that 19% o the total energy rom the uel input is saved using the heat recovery system. The maximum eiciency and Percentage o energy saved was obtained at 75% engine load. The results showed that the speciic energy consumption (SEC) decreased with a decrease in the thickness o the sample and increasing engine load. The lowest speciic energy consumption or the process o orange slice drying was obtained around kwh/kg water that were observed in 75% engine load and thickness o 3 mm. Reerences 1. Akgun, N.A. and I. Doymaz, Modelling o olive cake thin-layer drying process. Journal o Food Engineering, 68: AOAC, Oicial Methods o Analysis. Association o Oicial Analytical Chemists, Arlington, VA. 3. Barigozzi, G., A. Perdichizzi and S. Ravelli, Wet and dry cooling systems optimization applied to a modern waste-to-energy cogeneration heat and power plant. Applied Energy, 88: Basunia, M.A. and T. Abe, Perormance study o a small engine waste heated bin dryer in deep bed drying o paddy. Agricultural Engineering International: the CIGR Ejournal Manuscript X. 5. Beith, R., Small and micro combined heat and power (CHP) systems. Advanced design, perormance, materials and applications. Woodhead Publishing, USA. 6. Doymaz, İ., Eect o citric acid and blanching pre-treatments on drying and rehydration o Amasya red apples. Food and Bioproducts Processing, 88: EPA, Catalog o CHP Technologies. United States Environmental Protection Agency (EPA), USA. 8. Eriksson, G. and B. Kjellström, Assessment o combined heat and power (CHP) integrated with wood-based ethanol production. Applied Energy, 87: Fath, H.S.E., Diesel engine waste heat recovery or drying o clay minerals. Heat Recovery Systems and CHP, 11: Holmberg, H. and P. Ahtila, Optimization o the bark drying process in combined heat and power production o pulp and paper mill. in: A.F. Odilio, T.M. Eikevik, I. Strommen (Eds.), Proceedings o the 3rd Nordic Drying Conerence, Karlstad, Sweden. 11. Janick, J., Horticultural Reviews. John Wiley & Sons, Inc, New York. 12. Kemp, I.C., Reducing Dryer Energy Use by Process Integration and Pinch Analysis. Drying Technology, 23:

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