Designing a Toasting Oven in Order to Produce Corn Flakes

Prof. Dr. Suat Ungan Fd. E. 425 food Engineering Design Coordinator Middle East Technical University Food Engineering incision Ankara 06531 November 25, 2011 Dear Mr. Ungan, Please accept the accompanying Work Term Report, aimed designing a toasting oven in position to produce corn flakes. In the designed scheme 10 tons corn flakes per twenty-four hours is produced. After some processes, corn flakes enters the roasting oven at 20% humidity and exits at 4%humidity. The roasting oven can ope outrank at (10 ? C) 225 0C. Toasting oven is designed by considering its aloofness, argona and operating temperature.Optimizations are d one(a) according to these factors on the price of the native design. In the design dodging, rotary hum drier is used. 350 days of the year plant works and crosswayion occurs 16 hours in a day. give flakes enter the oven at 225 0C . Amount of childs play is measured as 0,648 kg dry out wrinkle/s . Length of the drier is calculated as 2. 27 m. in the result of optimizations done according to proper drying magazine and dried diameter. Heat energy needed to raise the inlet temperature of transfer to 225 0C, is bring as 157kw and wake up loss is found as 23. 6kw.Through these data, total investment which contains irrigateless cost and electricity cost is found as 92794. 98TL. Sincerely, group 3 members table OF CONTENT SUMMARY In this design a rotary desiccated is designed for drying of corn flakes which have the wet content 20%. Corn flakes are dried with air 9 % moisture content. The outpution is done for 16 hours in a day and 10 tons corn flakes are produced per day. In production process, corn flakes are cooked under pressure. After cooking step, big masses are broken to pieces and sent to driers in order to carry the moisture level at 20%. After this process, roduct is flaked between declamatory steel cylinders and cooled with internal water be given. Soft flakes are sent to rotary sunbakeds in order to dehyd ration to 4% final moisture content and toasting. In the toasting oven, flakes are exposed to 225 0C air for 2-3 min. The drier continuance is calculated as 2. 27 m with the diameter of 0. 082m with the boldness of 4%moisture content inlet air and 9%content waiver air. F crushed rate of feed is calculated as 0. 206kg/s. Mass flow rate of the inlet air is calculated as 0,648 kg dry air/s. Energy needed for bring the temperature of air to 225 0C is calculated as 157kw and heat loss in the trunk is 23. kw. By making optimizations total capital investment is calculated as92794. 98TL which implys 84881TL electricity cost and 7913TL dryer cost. Finally by making optimizations, in order to have minimum duration and suitable energy for the drier, 215 0C is chosen the best temperature for the inlet air. I. INTRODUCTION band dryers potentially represent the oldest continuous and undoubtedly the near common high volume dryer used in industry, and it has evolved more adaptations of the t echnology than any former(a) dryer classification. 1 Drying the materials is an important consumption process.It is also one of the important parts in cement production process, and affects the quality and consumption of the grinding machine. Drum dryer is the main equipment of drying materials, it has simple structure, reliable operation, and convenient to manage. However thither are some problems which are huge heat loss, low thermal efficiency, high heat consumption, more dust, and difficult to control the moisture out of the machine. It plays a significant role in improving drying technology level and thermal efficiency in drying process, reduce the thermal and production lost. 2 In this design we are asked to design a rotary drier which works 16 hours in a day and produces 10 tones corn flakes per day. Also it is mentioned that, corn flakes enters to drier at 20 %humidity and exits 3-5%humidity. This report is about designing a rotary dryer with its dimensions for considering t o get the minimum total cost. Optimizations are done according to inlet temperature of the air to the drier. In the design organization heat needed for heating the inlet temperatures and length of the rotary dryer as material cost is thought, and optimization is done by considering minimum total cost for the system.II. PREVIOUS WORK Drying is perhaps the oldest, most common operation of chemical engineering unit operations. Over four hundred types of dryers have been reported in the literature while over one hundred distinct types are commonly available3 Drying occurs by effecting vaporization of the liquid by providing heat to the wet feedstock. Heat may be supplied by convection (direct dryers), by conduction (contact or indirect dryers), radiation or by microwave. Over 85 percent of industrial dryers are of the convective type with fervid air or direct combustion bobblees as the drying medium.Over 99 percent of the screenings involve remotion of water. 3 * Rotary Dryer All rot ary dryers have the feed materials passing by a rotating cylinder termed a drum. It is a cylindrical shell normally constructed from steel plates, slightly inclined, typically 0. 3-5 m in diameter, 5-90 m in length and rotating at 1-5 rpm. It is operated in some cases with a negative internal pressure (vacuum) to prevent dust escape. Depending on the arrangement for the contact between the drying gas and the impregnables, a dryer may be classified as direct or indirect, con-current or counter-current.Noted for their flexibility and heavy construction, rotary dryers are less sensitive to good fluctuations in throughput and product size. 4 * Pneumatic/Flash DryerThe pneumatic or flash dryer is used with products that dry rapidly owing to the easy removal of free moisture or where any needed diffusion to the surface occurs readily. Drying takes place in a matter of seconds. Wet material is mixed with a stream of heated air (or other gas), which conveys it through a drying duct where high heat and mass transfer rates rapidly dry the product.Applications include the drying of filter cakes, crystals, granules, pastes, sludge and slurries in fact almost any material where a powdered product is required. * Spray Dryers Spray drying has been one of the most energy-consuming drying processes, tho it remains one that is essential to the production of dairy and food product powders. Basically, spray drying is accomplished by atomizing feed liquid into a drying chamber, where the small droplets are subjected to a stream of hot air and converted to powder particles.As the powder is discharged from the drying chamber, it is passed through a powder/air separator and collected for packaging. intimately spray dryers are equipped for primary powder gathering at efficiency of about 99. 5%, and most can be supplied with secondary collection equipment if necessary * Fluidised Bed Dryer Fluid bed dryers are found throughout all industries, from heavy mining through food, fine chemicals and pharmaceuticals. They provide an in effect(p) method of drying relatively free flowing particles with a reasonably narrow particle size distribution.In general, fluid bed dryers operate on a through-the-bed flow pattern with the gas passing through the product perpendicular to the direction of travel. The dry product is discharged from the same section. * Hot Air Dryer- Stenter Fabric drying is usually carried out on either drying cylinders (intermediate drying) or on stenters (final drying). Drying cylinders are basically a series of steam-heated drums over which the fabric passes. It has the drawback of pulling the fabric and effectively bring down its width.For this reason it tends to be used for intermediate drying * Contact Drying- Steam Cylinders/Can This is the simplest and cheapest mode of drying woven fabrics. It is mainly used for intermediate drying rather than final drying (since there is no means of controlling fabric width) and for pre drying prior to s tentering. * Infra red drying Infrared energy can be generated by electric or gas infrared heaters or emitters. Each energy source has advantages and disadvantages.Typically, gas infrared systems are more expensive to buy because they require safety controls and gas- cut intoling equipment, but they oft are less expensive to run because gas usually is cheaper than electricity. Gas infrared is often a good choice for applications that require a push-down storage of energy. harvests such as nonwoven and textile webs are examples where gas often is a good choice. 5 * III. DISCUSSION For the designed system a rotary drum dryer is chosen. Rotary drum dryeris used for drying material with humidity or granularity in the industries of mineral dressing, building material, metallurgy and chemical.It has advantage of reasonable structure, high efficiency, low energy consumption6 advantages of drum dryer Suitable for handling liquid or pasty feeds. Product is powdery, flaky form Uniform dr ying collect to uniform application of film. Medium range capacities. Very High thermal efficiency Continuous operation Compact installation Closed construction is possible7 By hot air stream, heat for Toasting of the flakes in the drier, or in the oven, is provided instead development flat baking surfaces. Depending on the production type and flow rate, drum dryer satisfies rotating at a constant promote, the slope and the length.The drum is also perforated so that allows the air flow inside. The perforation should not too much large but also prevent the escape of flakes. Also, during the thermal treatment browning, expansion degree, texture, flavour, storage stability is determined. In order to obtain the correct values, the drying temperature and time should be adjusted properly. For the optimization of the system, length of the drier, diameter value, working temperature are affect fixed cost, variable cost and the heat loss from the system is considered.First at all, ever-ch anging by temperature how affect necessary length is calculated T air in Z 210 2,308504 215 2,296091 220 2,284367 225 2,273274 230 2,262764 235 2,252792 It is seen that after temperature of the hot air increases, the necessary length of the system decreases . Due to decreasing of necessary length of the system , area decreases also , so fix cost is decreased (Money of dryer + installation) on the other hand according to table 6 T air in Q system electric cost field of battle money for cost of dryer + installation total cost 210 146,708 79222,32709 ,231014 7949,192995 87171,52 215 cl,2011 81108,57297 1,224622 7936,763821 89045,34 220 153,6941 82994,81886 1,218584 7925,023661 90919,84 225 157,1872 84881,06474 1,212872 7913,916768 92794,98 230 160,6802 86767,31062 1,20746 7903,393249 94670,7 235 164,1733 88653,5565 1,202325 7893,408318 96546,96 TABLE 6 Q loss is increased , by temperature increase so variable cost(electric cost ) is increased also. owever, due to not big changing in the areas fix cost variable do not change too much by increasing or decreasing the temperature, but Q loss, on the other hand, makes too much difference by increasing or decreasing the temperature and also electrical cost for one kw/h is 0. 15 TL ,the difference of changing one temperature to other one is too big than fix cost. And according to data and tables, the optimum temperature is 2100C due to this reasons do not have a specific curve to us , the result is predicted as the minimum temperature. i. Assumptions * Working time of the plant is assumed as 16 hours Drying time is assumed as 150 seconds (optimum time is given as 2-3 minutes). * Surface temperature of the corn flakes entering the drier is assumed as 25oC(Tfeed=25oC) * humidity of the air at the inlet and the outlet is assumed as 0. 04 and 0. 09, respectively. * Specific heat of the air is assumed as constant. ( cp,air=1. 02kj/kg*K) * Only the constant drying rate is considered in the calculations since it has a criti cal moisture of 4. 5-5. 2 %. 4 * The shape of the flakes is assumed as spherical. * Radius of dryer is taken as 0. 082 m The efficiency of the drier is assumed as 85% to realize the calculations. ii. Possible source of errors * The shape of the corn flakes may not be perfect spheres. * Calculations may be done improperly due to the air humidity assumptions. * The corn flakes may be stuck on each other. * IV. RECOMMENDED DESIGN 1. Drawing of proposed design 2. Tables Listing Equipment an Specifications Equipment Specifications Rotary Drum Dryer oestrus Medium Hot Air * Temperature 225 o C * Humidity in 0. 04 kg water / kg dry air * Humidity out 0. 09 kg water / kg dry airLength 2. 27 mPeripheral Area 1. 13 m2 bodily Stainless SteelType PerforatedProcessing time 3 minutes or 150 seconds TABLE 1 3. Tables for Material and Energy Balances T air, in (C) 210 215 220 225 230 235 T air, out (C) 163. 67 167. 57 171. 48 175. 37 179. 27 183. 16 Product rate (kg/s) 0. 174 0. 174 0. 174 0. 1 74 0. 174 0. 174 Feed rate (kg/s) 0. 206 0. 206 0. 206 0. 206 0. 206 0. 206 Mass of air (kg/s) 0. 648 0. 648 0. 648 0. 648 0. 648 0. 648 H in, air (kj/kg) 226. 107 231. 490 236. 874 242. 257 247. 641 253. 25 H out, air (kj/kg) 192. 191 196. 767 201. 343 205. 912 210. 495 210. 071 Q (kj/s) 33. 916 34. 724 35. 531 36. 339 37. 146 37. 954 Q loss (kj/s) 22. 006 22. 530 23. 054 23. 578 24. 102 24. 626 T feed in (C) 25 25 25 25 25 25 T feed out (C) 46. 253 46. 275 46. 298 46. 320 46. 343 46. 366 Z, length (m) 2. 32 2. 296 2. 284 2. 273 2,263 2. 253 A, peripheral area (m) 1. 231 1. 224 1. 219 1. 213 1. 207 1. 202 time (seconds) 150 150 150 150 150 150 TABLE 2 4. Process Economics According to 225oC QSYSTEM =157,18 kJ TEDAS ,for 1KW/hour electric , cost is 0. 5TL. - galvanising cost = QSYSTEM *3600*0,15 Eqn 19 Electric cost=84881,065TL - Area =(2*? *r*z)+(2*? *r2) Eqn 20 AREA=1,2128m2 For money cost dryer and installation a formula is found which is - Cost = 5555,56+ 1944,44*area Eqn 21 mo ney cost dryer and installation= 7913. 91TL - Total cost = electric cost + money cost dryer +installationEQN 22 Total cost=92794,98TL T air in Q system electric cost area money for cost of dryer + installation total cost 210 146,708 79222,32709 1,231014 7949,192995 87171,52 215 150,2011 81108,57297 1,224622 7936,763821 89045,34 220 153,6941 82994,81886 1,218584 7925,023661 90919,84 225 157,1872 84881,06474 1,212872 7913,916768 92794,98 230 160,6802 86767,31062 1,20746 7903,393249 94670,7 235 164,1733 88653,5565 1,202325 7893,408318 96546,96 TABLE 6 externalize 1 FIGURE 2 V.CONCLUSION AND RECOMMENDATIONS To sum up, the aim of this design project is to design a toasting oven for corn flakes to decrease its moisture content from %20 to 3-5 %. For this purpose, by using inlet temperature, humidity of air and inlet temperature and moisture content of corn flakes the system is designed. Moreover, during calculations length and radius of dryer, operating time, operating capacity and heat losses from the system is considered. After doing this calculation, the optimization done by altering the working temperature of the system and dryer radius and by considering heat losses from the system.These alterations affect to the some(prenominal) variable and fixed costs and different fixed and variable cost values are obtained. Different total costs values are obtained by using fixed cost and variable cost values and optimization is done. Finally, it is conculed that the dryer length is 2. 27 m when inlet air temperature is 225 oC. However, optimum length is obtained when the inlet air temperature is 215 oC which is 2. 296 m by considering total cost for the system. As a result, theoretical calculations are integrated with practical approach and feasible system is designed for the problem.As a recommendation, for the drying process of corn flakes other dryer types can be used. Fluidized bed dryer can be used for this process. There are some important advantages of this dyer . As an example, this type of dryer has very high thermal efficiency and low processing temperature can be used for the processing. 8 Moreover, the system should be controlled carefully, because any fluctuations in the temperature or other variables could made adverse effects. Temperature of the inlet air should be censored and color censor should be added to outlet of product to control the quality in a best way. VI. ACKNOWLEDGMENT Special thanks for their help and support to our instructors Prof. Dr. Suat UNGAN Assist. Cem BALTACIOGLU * VII. TABLE OF NOMENCLATURE xfeed = kg solid/kg feed xproduct = kg solid/kg product Xfeed = kg water/kg dry solid Xproduct = kg water/kg dry solid Humidity air in= kg water/kg dry air ? =density (kg/m3) Q =volumetric flow rate (m3/s) V=speed (m/s) D= diameter (m) g= gravitational acceleration (m/s2) Qloss = kJoule Hin = Kj /kg dry air hproduct = kJ/kg Gair = kg dry air/m2. s * VIII. REFERENCES 1 Retrieved on November 2011 from http//www. process-hea ting. om/Articles/Drying_Files/d238aadb9d268010VgnVCM100000f932a8c0____ 2 Retrieved on November 2011 from http//www. rotary-drum-dryer. com/Knowledge/2011-05-08/141. html 3 Retrieved on November 2011 from http//www. energymanagertraining. com/bee_draft_codes/best_practices_manual-DRYERS. pdf 4 Retrieved on November 2011 from http//www. barr-rosin. com/products/rotary-dryer. asp 5 Retrieved on November 2011 from http//www. thinkredona. org/rotary-dryer 6 Retrieved on November 2011 from http//www. blcrushers. com/chanping/2011-08-17/111. html? gclid=CM39p73vxKwCFQkLfAodemc4rw 7 Retrieved on November 2011 from http//www. rrowhead-dryers. com/drum-dryer. html 8retrieved on November 2011 from http//www. directindustry. com/prod/british-rema-processing-ltd/fluidized-bed-dryers-62696-580253. html * IX. APPENDIX standard CALCULATIONS Mass values and fractions data Capacity = 10000 kg per day product As assumed working time = 16 hours per day Product flow rate = (10000kg/day)*(1day/16hours) *(1 hour/3600) Product flow rate=0,174 kg/s Feed flow rate = (0,174*0,95)/0,8 Feed flow rate= 0,206 kg/s Moisture content of feed = 0,2 kg water/kg feed Moisture content of product = 0,05 kg water/kg product xfeed = 0,8 kg solid/kg feed product = 0,95 kg solid/kg product Xfeed = 0,2/0,8(=0,2/0,8=0,25 kg water/kg dry solid) Xfeed= 0,25 kg water/kg dry solid Xproduct = 0,05/0,95(=0,05/0,95=0,053 kg water/kg dry solid) = 0,053 kg water/kg product Xproduct= 0,053 kg water/kg product Temperature & humidity data Temperature of the air in = 225 oC Temperature of the feed = 25 oC Humidity air in = 0,04 kg water/kg dry air Humidity air out = 0,09 kg water/kg dry airH For finding G value, water balance is made as - G*Hin + F*Xfeed/(1+Xfeed) = G*Hout + P*XproductEqn 1. G*0,04 + 0,206*0,25/(1+0,25) = G*0,09 + 0,174*0,053/(1+0,053) G= 0,648 kg dry air/s For finding energy balance, Hin , Qloss , Hout are calculated - Hin = (1,005+1,88* Hin)*Tair,in Eqn2. (Material and Energy Balances in Food Engi neering, Esin, A. 1993, p. 429) Hin = (1,005+1,88*0,04)*225 Hin = 242,25 kJ/kg dry air As efficiency is taken 85% - Qloss = 0,15*Hin (85% efficiency) Eqn3. Qloss = 36,33 kJ/kg dry air - Qloss in system = G*QlossEqn4. Qloss in system = 0,648*36,456 Qloss in system = 23,578 kJ/s - Hout = (1,005+1,88* Hout)*Tair,out Eqn5. (Material and Energy Balances in Food Engineering, Esin, A. 1993, p. 429) Hout = 1,1742*Tout Energy balance - G*Hin = G*Hout + Qloss Eqn6. 0,648*243,045 = 0,648*(1,1742Tair,out) + 23,626 Tout air = 175,369oC Use eqn 5. And Hout is found as Hout = 205,91 kJ/s - Siebels Equation 33,49*(H2O) + 837,4Eqn 7. (Material and Energy Balances in Food Engineering, Esin, A. 1993 Eqn 5-33 p. 211) So , by using this equation cp,feed = 1,5 kJ/kg. oC cp,product = 0,98kJ/kg . oC ? feed = 1390 kg/m3 - hfeed = cp,feed*Tfeed Eqn. 8 hfeed = 1,5*25 hfeed = 37,5 kJ/kg - hproduct = cp,feed*Tproduct Eqn. 9 hproduct = 0,98*Tproduct Energy Balance G*Hin + F*hfeed = G*Hout + P*hproduct + Qloss Eq n 10. 0,648*243,045 + 0. 206*37. = 0. 648*206. 59 + 0. 174*0. 98* Tproduct + 23. 63 Tproduct = 46,32 oC hproduct = =45,39 kJ/kg As mentioned, assumption of radius of dryer is taken 0. 082 m - Gair = 0,648/(? *r2) Eqn. 11 Gair = 30,68 kg dry air/m2. s - hair = 1,17*(Gair)0,37 Eqn. 12(Transport Process and Separation Process Principles, Geankoplis , Eqn 9-6-10 p. 583) hair= 4. 5 kj/ kg cp,air=1. 02kj/kg*K - HTOG = (Gair*cp,air)/hair Eqn. 13 (Mass Transfer Operation, Treybal, p. 704) HTOG= 7. 535 Tair,in = 225 Tair,out = 175. 369 Tfeed = 25 Tproduct =46. 32 So TG is found by - TG = Tair,in Tair,out Eqn. 14 TG = 49. 06 - TM = (Tair,in Tfeed) + (Tair,out Tproduct)/2 Eqn. 15 TM = 164,52 -NTOG = TG/TM Eqn. 16 NTOG = 0,301 - z = NTOG*HTOG Eqn 17 z= 2,27 m - QSYSTEM=Gair*Hin Eqn 18 =242,25*0,648 QSYSTEM =157,18 kJ TEDAS ,for 1KW/hour electric , cost is 0. 15TL. - Electric cost = QSYSTEM *3600*0,15 Eqn 19 Electric cost=84881,065TL Area =(2*? *r*z)+(2*? *r2) Eqn 20 AREA=1,2128m2 For mone y cost dryer and installation a formula is found which is - Cost = 5555,56+ 1944,44*area Eqn 21 (Plant Design and Economics for Chemical Engineers, Max . S. Peters) money cost dryer and installation= 7913. 91TL - Total cost = electric cost + money cost dryer +installation EQN 22 Total cost=92794,98TLFor finding changes due to increasing temperature to higher or lower ( 10 ? C) from 225oC Humidityin and Humidityout are taken constant. Humidity air in = 0,04 kg water/kg dry air Humidity air out = 0,09 kg water/kg dry airH T air in Hin Q loss Qloss in SYSTEM Tair out Hout 210 226,107 33,91605 22,00620197 163,6782 192,191 215 231,4905 34,72358 22,53015916 167,5753 196,7669 220 236,874 35,5311 23,05411635 171,4724 201,3429 225 242,2575 36,33863 23,57807354 175,3695 205,9189 230 247,641 37,14615 24,10203073 179,2666 210,4949 235 253,0245 37,95368 24,62598792 183,1637 215,0708 TABLE 4Gair and h are constant , as I found before as hfeed = 37,5 kJ/kg and Gair =30,68 T air in T product h prod uct h air h TOG TG TM N TOG z 210 46,25308 45,32802 4,152621 7,535866 46,32179 151,2126 0,306336 2,308504 215 46,27571 45,3502 4,152621 7,535866 47,42469 155,6498 0,304688 2,296091 220 46,29834 45,37238 4,152621 7,535866 48,52759 160,087 0,303133 2,284367 225 46,32097 45,39455 4,152621 7,535866 49,63049 164,5243 0,301661 ,273274 230 46,3436 45,41673 4,152621 7,535866 50,73339 168,9615 0,300266 2,262764 235 46,36623 45,43891 4,152621 7,535866 51,83629 173,3987 0,298943 2,252792 TABLE 5 T air in Q system electric cost area money for cost of dryer + installation total cost 210 146,708 79222,32709 1,231014 7949,192995 87171,52 215 150,2011 81108,57297 1,224622 7936,763821 89045,34 220 153,6941 82994,81886 1,218584 7925,023661 90919,84 225 157,1872 84881,06474 1,212872 7913,916768 92794,98 230 160,6802 86767,31062 1,20746 7903,393249 94670,7 235 164,1733 88653,5565 1,202325 7893,408318 96546,96 TABLE 6 FIGURE1 FIGURE 2 FIGURE 3 According to figures, most suitable temperature is 210oC by making optimization.