Mechanical separation in food processing
Mechanical separation in food processing

1.Introduction


Separation is a significant unit activity in the dairy and food processing industries. Sieving, filtering, membrane separation, gravity separation, centrifugal separation, and other physical separation procedures are examples. They can also be roughly classed as Liquid-Liquid, Liquid-Gas, Solid-Solid, and Solid-Gas separations. Each operation would require a unique separation application. Some frequent procedures in the dairy business include separating fat from milk, separating extraneous matter from milk, separating fine powder particles from spray drier exhaust air, filtering moisture from various dairy products, and so on. The process of passing a fluid containing suspended particles through a porous media is known as filtration. The suspended solids are trapped by the medium, resulting in a cleared filtrate.

 

Separation is a major unit activity in the dairy industry. Most phases of the food industry employ processes that rely primarily on physical forces to achieve the necessary separation of components. These processes, known as mechanical separations, include filtering, sedimentation, and centrifugation. Each of these procedures requires applying a force to the fluid of interest, which results in the separation of the product components due to the varied reactions of the components to the force applied. The force involved in filtering is the force required to move a fluid through a filter medium. In the case of sedimentation, the forces are gravity and the action of gravitational forces on the various components of the sediment.

 

2.Sedimentation


Gravitational forces are used in sedimentation to remove particulate particles from fluid streams. The particles are normally solid, but they can also be minute liquid droplets in a fluid that can be either liquid or gas. In the food industry, sedimentation is frequently used to separate dirt and debris from incoming raw material, crystals from their mother liquor, and dust or product particles from air streams.

 

Gravitational force causes materials to settle to the bottom of a fluid, separating suspended particles from fluids. The particles are normally solid, but they can also be small liquid droplets, and the fluid might be liquid or gas. In the food industry, sedimentation is frequently used to separate dirt and debris from incoming raw material, crystals from their mother liquor, and dust or product particles from air streams. Gravity sedimentation is classified into two types: clarity and thickening. Clarification is the process of removing small amounts of suspended particulates from a liquid stream to produce a clarified effluent or overflow stream. Thickening, on the other hand, is the process of concentrating dilute solutions for future treatment in

 

2.1. Clarifier

 

Clarifiers are settling tanks with mechanical mechanisms for continuously removing sediment-deposited particles. A clarifier is typically used to remove solid particles or suspended solids from a liquid to clarify and/or thicken it. Sludge refers to concentrated pollutants discharged from the tank's bottom, whereas scum refers to particles that float to the liquid's surface.

 

3.Filtration


The insoluble solid component of a solid-liquid suspension is separated from the liquid component in this method of separation by passing the latter through a porous membrane known as the filter medium, which retains the solid particles within its structure and/or as a layer on its upstream face. The filter cake is a layer of solid particles that forms on the upstream face of the medium. The filtrate is the clear liquid that passes through the media. The liquid can pass through the medium and cake using gravity alone (gravity filtration), under pressure (pressure filtration), or by establishing a partial vacuum downstream of the medium (vacuum filtration).

 

3.1. Filtration equipment

 

· Plate and frame filter


In this type of filter, the plates and frames are closely pressed together to Create a liquid-tight unit. The feed is injected into the hollow frames via holes in one of the frames' corners. The cake accumulates in the frames, and the filtrate flows through the filter medium onto the grooved surface of the plates, where it leaves through an outlet channel in each plate. When the filtering is finished, the wash liquid can be pumped through the press in the same manner as the filtrate. Special wash plates are available on some presses. Each plate in the frame is a wash plate. These serve as filter plates during filtration.


During washing, the wash plates' ports are closed, and the wash liquid is pushed onto their surfaces through an inlet channel. Before entering the filter plates, the wash liquid travels through the entire thickness of the cake and two layers of filter media. This is supposed to result in more effective washing than would be possible without the wash plates. The press is opened after washing, the cake is taken from the frames, and the filter media is cleaned.




4.Centrifugation

Centrifugation is the separation of materials through the application of centrifugal force. It can be used to separate immiscible liquids as well as to separate insoluble particles from liquids.

 

4.1. Centrifugal equipment


· Solid bowl decanter

A bowl shaped can be used to separate solid particles that settle rather quickly.

The bowl wall, however, is not perforated, and no filter material is utilized. Solids accumulate on the inside of the bowl wall, while clear liquid pours out over the bowl's top rim into the outside casing. The feed is stopped at intervals, and the solids are removed with a knife and released through an opening in the bottom of the bowl. This type of clarifier can handle feeds containing up to 2.0% solids.

 

 

5.References


https://nscpolteksby.ac.id/ebook/files/Ebook/Hospitality/Food%20Processing%20(2011)/14%20-%20Separations%20in%20Food%20Processing.pdf


https://link.springer.com/chapter/10.1007/978-94-010-9337-8_8#:~:text=Processes%20which%20depend%20primarily%20on,filtration%2C%20sedimentation%2C%20and%20centrifugation.


https://sci-hub.se/10.1007/978-94-010-9337-8_8


 

 


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