Food Process Engineering Drying Methods & Types PDF

ABEN 4510 FOOD PROCESS ENGINEERING DRYING (Air convective drying and Types of Dryer) MAY ALISBO-CABRAL Department of Agricultural and Biosystems Engineering College of Engineering Central Luzon State University...

ABEN 4510 FOOD PROCESS ENGINEERING DRYING (Air convective drying and Types of Dryer) MAY ALISBO-CABRAL Department of Agricultural and Biosystems Engineering College of Engineering Central Luzon State University 1 TOPIC OUTLINE Air convective drying Types of Dryer Air Convection Drying DEHYDRATION OR ARTIFICIAL DRYING - defined as drying under controlled conditions of temperature and humidity to a specific end point in a given time. AIR CONVECTION – most commonly used method of artificial drying due to its simple operation and low cost HOT AIR DEHYDRATORS -work essentially on the same principle where preheated air is made to pass through the moist product and in the process it evaporates and carries the moisture out of the dryer through some exhaust port TYPICAL CABINET DEHYDRATOR (COMPONENTS) DRYING CHAMBER BLOWER OR FAN HEATING SYSTEM TRAYS CONTROL SYSTEM Basic parts of food dryer (Source Carpio,2000) TYPICAL CABINET DEHYDRATOR (COMPONENTS) DRYING CHAMBER space where the product is contained an insulated chamber with a suitable duct and baffle system to promote uniform air distribution adjustable baffles may be used to direct air down through a drying tray or horizontally across the product surface Dampers may be installed to regulate the exhaust of air leaving the tray section, allowing the intake of fresh air to make up for the exhaust and recirculate the rest of the mainstream air TYPICAL CABINET DEHYDRATOR (COMPONENTS) BLOWER OR FAN used to moved the air within the drying chamber from the heat source to the product aim to promote even or uniform air velocity distribution within the drying chamber the recommended air speed across food materials is between 1 and 4 m/s. the capacities of fans and blowers intended for food dehydration should be designed to meet this air velocity requirement  TYPICAL CABINET DEHYDRATOR (COMPONENTS) HEATING SYSTEM temperature of the air can be raised to the desired drying temperature by either direct or indirect heating. The direct method of heating forces the air to pass directly through an open flame or some other heat source and in the process mixes with it whatever product of combustion is produced (limited to grain drying) Cabinet dryers for food applications require clean hot air that is indirectly heated by passing air across the heat exchanger supplied with steam or heated by direct combustion of fuel. In some dryers, particularly the experimental types, air is heated using electrical resistance units. AGBE2223: AB Products Processing and Storage TYPICAL CABINET DEHYDRATOR (COMPONENTS) TRAYS it support the products within the drying chambers the construction of which depends on the product being dried and the manner in which the air moves within the drying chamber pans- products with very high moisture, such as pastes and slurries pans since it will allow drying only on the top surface making them suitable for cross-flow type dryers where the air movers parallel to the tray. the most common types of trays are those with screen bottoms because perforated bottoms allow the passage of the drying medium through the trays. as long as the product can be retained over the tray perforations, this type of product support is ideal for both cross-flow and through-flow dryers. TYPICAL CABINET DEHYDRATOR (COMPONENTS) CONTROL SYSTEMS System for regulation the condition within the drying chamber (a specified air velocity, air temperature and humidity) humidity is the most difficult to control. In A computer-controlled food dryer (Source: Carpio,2000) systems where air is taken from the surroundings, the drying chamber humidity is limited by the conditions of the ambient air. Source:https://www.google.com/url?sa=i&url=http%3A%2F% 2Fwww.unido.or.jp%2Fen%2Ftechnology_db%2F6436%2F&ps ig=AOvVaw2sMiReTOBZTeXNAQq8Ehat&ust=16200220137840 00&source=images&cd=vfe&ved=0CAIQjRxqFwoTCJiGrrmqqv ACFQAAAAAdAAAAABAJ TYPE OF DRYER/DRYING SUNDRYING FLUIDIZED BED ROLLER OR DRUM DRYERS TRAY or CABINET PNEUMATIC DRYERS DRYING VACUUM SHELF TUNNEL DRYERS ROTARY DRYING DRYER BIN DRYER TROUGH DRYERS FREEZE DRYER SPRAY DRYER BELT DRYER SUNDRYING Sunlight is a portion of the electromagnetic radiation given off by the sun, in particular infrared, visible and ultraviolet light Sundrying is a traditional Source:https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.researchgate.net%2Ffigure%2FSliced-tomatoes- on-drying-racks-in-open-sun-drying_fig1_327560619&psig=AOvVaw19Cov4fm4umDO0_Sx- VC7_&ust=1620022793349000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCMCw86qtqvACFQAAAAAdAAAAABAD method of reducing the moisture content of paddy by spreading the grains under the sun (IRRI) Source:https://www.google.com/url ?sa=i&url=http%3A%2F%2Fwww. knowledgebank.irri.org%2Fstep-by- The solar radiation heats up the step- production%2Fpostharvest%2Fdryi grains as well as the surrounding ng%2Ftraditional-drying- systems%2Fsun- drying&psig=AOvVaw19Cov4fm4u air and thus increases the rate of mDO0_Sx- VC7_&ust=1620022793349000&so urce=images&cd=vfe&ved=0CAIQj water evaporating from the RxqFwoTCMCw86qtqvACFQAAAAAd AAAAABAI grains. Tray or cabinet dryers small-capacity dryers that use hot air as the drying medium. products being dried are often carried on trays that can be supported either by tray guides attached on the walls of the drying chamber or by tray trucks that could be rolled into and Source:https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.slideshare.net%2Fphysics101%2Fdrying-equipments- 8453309&psig=AOvVaw1QmPWXvGlARfYrpTPrT6d0&ust=1620022975758000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCIC1oo OuqvACFQAAAAAdAAAAABAD out of the dryer. generally low-cost and easy to construct and operate ideal for laboratory drying experiments and other drying tests because of its small size. can be connected to a source of air Source:https://www.google.com/url?sa=i&url=https%3A%2F%2Fww w.indiamart.com%2Fproddetail%2Fcabinet-dryers- 11322245448.html&psig=AOvVaw1QmPWXvGlARfYrpTPrT6d0&ust=16 heated by gas, diesel or biomass such Source:https://www.google.com/url?sa=i&url=https%3A%2 F%2Fthermopedia.com%2Fcontent%2F710%2F&psig=AOvV 20022975758000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCIC1 ooOuqvACFQAAAAAdAAAAABAV as rice husk. aw1QmPWXvGlARfYrpTPrT6d0&ust=1620022975758000&so urce=images&cd=vfe&ved=0CAIQjRxqFwoTCIC1ooOuqvACF QAAAAAdAAAAABAP TUNNEL DRYERS a modification of tray dryer in which the oven is replaced by a tunnel which receives damp materials at one end and discharges the dried products at the other end. consist of long drying chambers that can accommodate a train of carts loaded with a number of trays. the drying medium moves from one end of the tunnel to the other and in the process picks up moisture from the product. auxiliary heaters are commonly installed at certain section of the drying chamber because the drying air temperature tends to drop along the length of the tunnel. designed for continuous operation by providing means of moving the tray carts from one end of the tunnel to the other. co-current tunnel dryers, the trucks move within the drying chamber along the direction of the hot air flow(the product is exposed to the maximum dryer temperature when its moisture is highest, this, minimizing the risk of product heat damage) counter-current flow dryers are also known for their efficient and economical used of heat.  Solar tunnel dryer TUNNEL DRYERS https://www.google.com/url?sa=i&url=https %3A%2F%2Fwww.indiamart.com%2Fproddet ail%2Fsolar-tunnel-dryers- 4547619448.html&psig=AOvVaw07oJ1lr6b9ng 3hSLcAhBEr&ust=1620023378286000&source =images&cd=vfe&ved=0CAIQjRxqFwoTCMj1g 8avqvACFQAAAAAdAAAAABAO Source:https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.slideshare.net%2Fmahmudulmithun%2Fdehydration- 96285431&psig=AOvVaw07oJ1lr6b9ng3hSLcAhBEr&ust=1620023378286000&source=images&cd=vfe&ved=0CAIQjRxqFwoTC Mj1g8avqvACFQAAAAAdAAAAABAJ Source:https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.wymasolutions.com%2Fproducts%2Fdrying%2Fdrying- tunnel%2F&psig=AOvVaw07oJ1lr6b9ng3hSLcAhBEr&ust=1620023378286000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCMj1g8avqvACFQAAA AAdAAAAABAU BIN DRYERS Soirce:https://www.google.com/url?sa =i&url=https%3A %2F%2Ffyi.extensi on.wisc.edu%2Fen ergy%2Fgrain- drying-and- storage%2Fbatch- grain- Applicable for drying cereal grains, as dryers%2F&psig=A OvVaw1IoUh12dW hNZDhRgTql9lw&u st=1620023798656 well as other relatively dry granular 000&source=image s&cd=vfe&ved=0C AIQjRxqFwoTCLiH- o6xqvACFQAAAAAd products of dryer AAAAABAf consists of a container bin with perforated flooring and a drying air Source:https://www.google.com/url?sa=i&url=ht tps%3A%2F%2Ffyi.extension.wisc.edu%2Fener plenum underneath. gy%2Ffiles%2F2016%2F09%2FFS_BatchDryers. pdf&psig=AOvVaw1IoUh12dWhNZDhRgTql9lw& ust=1620023798656000&source=images&cd=vf Hot air is forced from the plenum e&ved=0CAIQjRxqFwoTCLiH- o6xqvACFQAAAAAdAAAAABAJ through the flooring and through the bed of granular food product. https://sites.google.com/a/mytu.tuskeg Drying can take place only if the air ee.edu/biofuelsacademy/home/web- modules/equipment/bin-storage- units/dryer-feed- can pass through the bed of bin?tmpl=%2Fsystem%2Fapp%2Ftemp lates%2Fprint%2F&showPrintDialog=1 commodity being dried. generally require low capital and operating costs but they allow relatively low drying rates FLUIDIZED BED DRYERS Source:https://ww w.google.com/url? sa=i&url=https%3 A%2F%2Fwww.sli deshare.net%2FAl auddinBadol%2Ffl optional method for controlled, gentle and even drying of uidized-bed- dryers&psig=AOvV aw2YW22gMgyDc2 wet solids HlcaLvrDyr&ust=1 620024980359000 &source=images& used for drying materials such as granules, tablet, powder, cd=vfe&ved=0CAI QjRxqFwoTCJjD- fertilizers and plastics 721qvACFQAAAAA dAAAAABAe popular in production industries pharmaceutical, chemical, food, dairy, metallurgical dyes and other process industries works on a principle of fluidization of the feed materials (converting materials from a static solid-like state to a dynamic fluid-like state). hot gas or air is introduced through a perforated distribution plate into the area holding the material. This hot gas pumps through the spaces between solid particles. As the velocity of the gas or air increases, the upward forces on the particles increase, Source:https://www.google.com/url?sa=i&url=https%3A%2 F%2Fwww.saintyco.com%2Ffluid-bed-dryer-the-ultimate- causing them to equal the gravitational forces below. guide-for- importers%2F&psig=AOvVaw2YW22gMgyDc2HlcaLvrDyr&ust This creates a state of fluidization where the particles are =1620024980359000&source=images&cd=vfe&ved=0CAIQj RxqFwoTCJjD-721qvACFQAAAAAdAAAAABAN suspended in what appears to be a boiling bed of liquid FLUIDIZED BED DRYERS Source:https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.tianlienergy.com%2Fproducts%2FFluidized_Bed_Dryer.html&psig=AOvVaw2YW22gMgyDc2HlcaLvrDyr&ust=1620024 980359000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCJjD-721qvACFQAAAAAdAAAAABAI PNEUMATIC DRYING Also known as flash dryers one of the most https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.solid common types of swiki.com%2Findex.php%3Ftitle%3DPneumatic_Dryers&psig=AOvVa w2A4HLiDwmz31I1wPos30wW&ust=1620025529404000&source=ima ges&cd=vfe&ved=0CAIQjRxqFwoTCIiOkMq3qvACFQAAAAAdAAAAAB Ad industrial drying units, are characterized by continuous convective heat and mass transfer processes. particulate solids to be dried travels through the drying duct along A schematic diagram of the pneumatic dryer for high moisture paddy: (1) high-pressure blower, (2) electric heater, (3) drying column, (4) cyclone, (5) with hot air and it get temperature controller, (6) globe valve, and (7) hopper dried during transport Source:https://www.researchgate.net/publication/338505315/figure/fig1/AS:845785373609985@1578662355599/A- in a hot gas stream. schematic-diagram-of-the-pneumatic-dryer-for-highmoisture-paddy-1-high-pressure.ppm ROTARY DRYING utilize a hot gas stream or cold gas stream, that mixes with the air stream by utilizing lifters that showers the product in the air stream. used in the chemical and mineral industry. In food, industry, their most common applications are for dehydrating waste materials (citrus peels, vegetable https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.di dion.com%2Frotary- dryers.html&psig=AOvVaw2UWT3quCxybAYkDfFjVdlW&ust=1620 trimmings) and animal feedstuffs 026073573000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCM Cu-8m5qvACFQAAAAAdAAAAABAD (alfalfa). consist of a metal cylinder (slightly inclined) with internal flights or louvers. ROTARY DRYING Material is fed at the high end and discharged at the low end. Hot air is blown in co-current or countercurrent direction. As the cylinder rotates, the material climbs in the direction of rotation. When it reaches a position where its angle of repose has been exceeded, the material falls back to the bottom of the cylinder. Most of the drying takes place while the material https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.di dion.com%2Frotary- falls through the air blast. dryers.html&psig=AOvVaw2UWT3quCxybAYkDfFjVdlW&ust=1620 026073573000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCM Cu-8m5qvACFQAAAAAdAAAAABAD Using very hot air or combustion gases, rotary dryers can also function as roasters for nuts, sesame seeds, and cocoa beans ROTARY DRYING Source: https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.gea.com%2Fen%2Fproducts%2Fdryers-particle-processing%2Frotary-dryers- coolers%2Frotary-dryer.jsp&psig=AOvVaw2UWT3quCxybAYkDfFjVdlW&ust=1620026073573000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCMCu- 8m5qvACFQAAAAAdAAAAABAJ TROUGH DRYER the materials to be dried are contained in a trough – shaped conveyor belt, made from mesh, and air is blown through the bed of material. movements of conveyor continually turn over the material, exposing fresh surfaces to the hot air. Schematic cross section of belt-trough dryer. (From Sokhansanj, S. and Jayas, D.S., in: Handbook of Industrial Drying, Mujumdar, A.S., Ed., Marcel Dekker, New York, 1987.) BELT DRYING continuous convective belt dryer. well – ventilated layer of product is put on a wire mesh or perforated plate belt conveyor and conveyed continuously through drying chamber Source:https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.food-machines.org%2Fvegetable-processing-machinery%2Fbelt-type-fruit-vegetable-drying- machine.html&psig=AOvVaw3_QdRf2Gi8h0mqa8tHohBl&ust=1620027724570000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCLiqnuC_qvACFQAAAAAdAAAAABAO ROLLER OR DRUM DRYERS a method used for drying out liquids from raw materials with drying drum. pureed raw ingredients are dried at relatively low temperatures over rotating, https://www.google.com/url?sa=i&url=https%3A%2F %2Fwww.aveka.com%2Fprocessing%2Froll- drying%2F&psig=AOvVaw1QRQhotUHG4TmPG6YxcvnT &ust=1620028097550000&source=images&cd=vfe&ve high capacity drums that d=0CAIQjRxqFwoTCNj6zo3BqvACFQAAAAAdAAAAABAD produce sheets of drum dried product. ROLLER OR DRUM DRYERS consist of rotating drums that are heated from within, generally, by steam. during its rotation, the heated drum surface is allowed to come in contact with a pool of liquid material. liquid immediately boils and sticks to the drum surface where it dries. the dried film of food sticking on the surface is removed from the rotating drum with a stationary https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.aveka.com%2Fprocessing%2Froll- drying%2F&psig=AOvVaw1QRQhotUHG4TmPG6YxcvnT&ust=1620028097550000&source=images&c scraper d=vfe&ved=0CAIQjRxqFwoTCNj6zo3BqvACFQAAAAAdAAAAABAD provide high drying rates and economical use of heat(suited only for liquid or slurry foods that can stand high temperatures for short periods ranging from 2 to 30 seconds). In the food industry, therefore, drum dryers are used for milk, soups and baby foods ROLLER OR DRUM DRYERS A schematic diagram of a single drum dryer A schematic diagram of a double drum dryer (Source: Carpio,2000) (Source: Carpio,2000) VACUUM SHELF-DRYER https://www.g oogle.com/url? sa=i&url=https %3A%2F%2F www.slideshar e.net%2FSURA JKUMAR1229 %2Fdrying- Drying of heat-sensitive food products and- dehumidificatio n- 147657438&ps at temperatures below 100°C may be ig=AOvVaw0d TF9oL5mchPq Z- achieved using vacuum dryers. DcYkw19&ust =1620028285 890000&sourc These dryers consist of an air-tight e=images&cd =vfe&ved=0C AIQjRxqFwoTC MCl3ObBqvAC chamber with food products heated at FQAAAAAdAAA AABAX low pressures. https://www. google.com/ur The pressure ranging from 0.135 to l?sa=i&url=ht tps%3A%2F %2Flacotech. 9.45 kPa allows evaporation of com%2Fprod ucts%2Fcusto m-solution- high-vacuum- moisture from the product at low product- testing- chamber-for- temperatures. fuel- components& psig=AOvVaw Drying cost using this system is 0dTF9oL5mch PqZ- DcYkw19&ust =1620028285 relatively high because additional work 890000&sourc e=images&cd =vfe&ved=0C is needed to pull a vacuum within the AIQjRxqFwoT CMCl3ObBqvA CFQAAAAAdA AAAABAj drying chamber. FREEZE DRYER works on the principle of sublimating ice from a frozen food product and removing the vapor in a partial vacuum of about 13.5 to 270.0 Pa pressure. At these pressures, the product is below point of water, A schematic diagram of freeze dryer (Source: Carpio,2000) hence, the vapor is removed without passing through phase. The removal of moisture from within the product in the Source:https://www. google.com/url?sa=i vapor for in limiting the movement of soluble solids, &url=https%3A%2F %2Flivingrational.co maintaining the tissue and minimizing product m%2Fproduct%2Fha rvest-right-freeze- dryer- shrinkage. small%2F&psig=AOv Vaw26bEOV5lnFLoId Pwg9mlJt&ust=1620 Sublimation can take place at temperature below 028531666000&sour ce=images&cd=vfe& ved=0CAIQjRxqFwo 0°C, hence, foods can be dried without heat damage. TCOjCxuHCqvACFQA AAAAdAAAAABAD Unlike the other drying procedures described previously, freeze drying is an expensive process suited mainly for special types of dried products FREEZE DRYER Source: https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.sciencedirect.com%2Ftopics%2Fagricultural-and-biological-sciences%2Ffreeze- dryers&psig=AOvVaw26bEOV5lnFLoIdPwg9mlJt&ust=1620028531666000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCOjCxuHCqvACFQAAAAAdAAAAABAK REFERENCES Carpio, 2000. E.V. Engineering for Food Technologist. UPLB Publishing Center. Singh R. P and Heldman, D.R.. 2009. Introduction to Food Engineering Fourth Edition. Elsevier Inc. Retrieved at http://www.ucarecdn.com/fb7332e8-c35a-47b0-9805-051fa171f8fa/. Food Process Engineering and Technology. https://doi.org/10.1016/B978-0-12-812018-7.00003-8# 2018 Elsevier Inc. All rights reserved. Earl and Earl. UNIT OPERATIONS IN FOOD PROCESSING. Retrieved at Unit Operations in Food Processing - R. L. Earle  Thank you and God bless! Keep safe and stay healthy AGBE2223: AB Products Processing and Storage