Advance in mass transfer in food application

mass transfer apllication in food industry

1. ADVANCE IN MASS TRANSFER IN FOOD APPLICATION 4/20/2016 1 Prasented by Swapnil Prashant Gautam 15/PFT/007 M.Tech (food tech) First Year

2. DIFINITION 4/20/2016 2 Mass transfer  is the net movement of mass from one location, usually meaning stream, phase, fraction or component, to another. Mass transfer occurs in many processes, such as absorption,evaporation,adsorption,drying,precipitation,membrane filtration,and distillation. Mass transfer is used by different scientific disciplines for different processes and mechanisms . The phrase is commonly used in  engineering  for physical processes that involve  diffusive  and  convective  transport of  chemical species  within  physical systems .

3. EXAMPLE 4/20/2016 3 Some common examples of mass transfer processes are the  evaporation  of  water  from a pond to the  atmosphere , the purification of blood in the  kidneys  and  liver , and the distillation of alcohol . In industrial processes, mass transfer operations include separation of chemical components in distillation columns, absorbers such as scrubbers, adsorbers such as activated carbon beds, and liquid-liquid extraction . Mass transfer is often coupled to additional  transport processes , for instance in industrial  cooling towers . These towers couple heat transfer to mass transfer by allowing hot water to flow in contact with hotter air and evaporate as it absorbs heat from the air.

4. FUNDAMENTAL OF MASS TRANSFER 4/20/2016 4 A group of unit operations for separating the components of mixtures is based on the transfer of material from one homogenous phase to another . The driving force for transfer is a concentration difference or a concentration gradient; much like a temperature difference or a temperature gradient provides the driving force for heat transfer. These methods, covered by the term mass-transfer operations, include such techniques as indicated below: • Distillation • Gas absorption • Dehumidification • Liquid extraction • Leaching • Drying

5. Distillation 4/20/2016 5 The purpose of distillation is to separate, by vaporization, a liquid mixture of miscible and volatile substances into individual components or, in some cases, into groups of components . The separation of a mixture of alcohol and water into its components; of air into nitrogen, oxygen, and argon; and of crude petroleum into gasoline, kerosene, fuel oil, and lubricating stock are examples of distillation

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7. distillation has many applications 4/20/2016 7 In the fossil fuel industry distillation is a major class of operation in obtaining materials from  crude oil for fuels and for chemical  feedstocks . Distillation permits separation of air into its components — notably  oxygen ,  nitrogen , and  argon  — for industrial use . In the field of industrial chemistry, large ranges of crude liquid products of  chemical synthesis  are distilled to separate them, either from other products, or from impurities, or from unreacted starting materials. Distillation of  fermented  products produces  distilled beverages  with a high alcohol content, or separates out other fermentation products of commercial value.

8. GAS ABSORPTION 4/20/2016 8 Gas absorption  (also known as scrubbing) is an operation in which a  gas  mixture is contacted with a liquid for the purpose of preferentially dissolving one or more components of the  gas  mixture and to provide a solution of them in the liquid.

9. continue 4/20/2016 9 The principal requirements of a tower packing are It must be chemically inert to the fluids in the tower . It must be strong without excessive weight . It must contain adequate passages for both streams without excessive liquid holdup or pressure drop. It must provide good contact between liquid and gas . It must be reasonable in cost.

10. Dehumidification 4/20/2016 10 The process in which the moisture or water vapor or the humidity is removed from the air keeping its dry bulb (DB) temperature constant is called as the dehumidification process. This process is represented by a straight vertical line on the  psychrometric chart  starting from the  initial  value of relative humidity, extending downwards and ending at the final value of the relative humidity. Dehumidification process along with cooling or heating is used in number of air conditioning applications. Let us see how these processes are obtained and how they are represented on the psychrometric chart

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12. L iquid extraction 4/20/2016 12 Liquid – liquid extraction  also known as solvent  extraction  and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible  liquids , usually water and an organic solvent. It is an  extraction  of a substance from one  liquid  into another  liquid phase .

13. Leaching 4/20/2016 13 Leaching normally refers to the removal of a substance from a solid via a liquid extraction media. The desired component diffuses into the solvent from its natural solid form. Examples of leaching include the removal of sugar from sugar beets with hot water and the removal of nickel salts or gold from their natural solid beds with sulfuric acid solutions. Application: It is used for leaching of gold from its ore by using sodium cyanide solutions . It is used for extraction of oil from oilseeds such as soyabeans by using hexane or petroleum ether as a solvent . It is used for extraction of sugar from sugar beats using hot water . It is used for extraction of tannin from tree barks using water . It is used for extraction of medicinal compounds from plant roots, leaves and stems. It is used for extraction of perfumes from flowers . It is also used for preparation of tea and coffee.

14. 4/20/2016 14 Drying Drying  is a  mass transfer  process consisting of the removal of water or another   solvent  by  evaporation  from a  solid ,  semi-solid  or  liquid . This process is often used as a final production step before selling or packaging products Applications of drying: Food source : Foods are dried to inhibit microbial development and quality decay. However, the extent of drying depends on product end-use. Cereals and oilseeds are dried after harvest to the moisture content that allows microbial stability during storage. Vegetables are blanched before drying to avoid rapid darkening, and drying is not only carried out to inhibit microbial growth, but also to avoid browning during storage Non food source : Among non-food products, those that require considerable drying are  wood  (as part of Timber processing), paper, flax, and washing powder. The first two, owing to their organic origins, may develop mold if insufficiently dried. Another benefit of drying is a reduction in volume and weight.

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