Selection of Centrifuges in Breweries

1. Principle of Centrifuge

Centrifugal separation is the separation of liquid heterogeneous mixture by inertial centrifugal force.

The settling speed is directly proportional to the square of solid particle diameter, density difference and centrifugal factor, and inversely proportional to the viscosity of solution. The separation factor is an important index of its separation performance.

The production capacity is determined by three factors:

(1) Drum speed.

(2) Drum radius.

(3) Drum height.

Because the change of rotating speed will change the settling speed in the form of the second power, the drum diameter of the centrifuge with fast rotating speed should be very small, otherwise, the force will be large, exceeding the allowable stress of the machine material, resulting in the damage of the centrifuge.

2. Advantages and Disadvantages of Common Centrifuges

2.1 Plate Centrifuge

The main components of the machine are conical plates made of many layers of stainless steel with a spacing of about 0.3-2.0mm. According to the different content and size of solid particles in the separated materials, the spacing can be increased or decreased, so as to increase the equivalent clarification area of the conical plates. The rotating speed is 5000-10000r/min, and the centrifugal factor is 4000-6000.

The separation process is as follows:

(1) The beer liquid is pushed from the inlet to the drum by the pump pressure (about 3×105Pa) .

(2) The beer liquid is divided into many small tributaries through the surface of the conical plates.

(3) The beer liquid tributaries flow up between the conical plate gaps to the top outlet by the large centrifugal force.

(4) The solid particles flow along the edge of the conical plates to the sewage chamber at the bottom of the drum. At this time, the beer has become clear.

Advantages:

(1) Before the sewage chamber fully filled, the good clarification effect remains unchanged.

(2) The settlement capacity is large.

(3) The liquid with high solid content can be well treated.

(4) There is no need for a agitator in the wort tank.

Disadvantages:

(1) Need manual cleaning.

(2) It will reduce the production capacity by using beer pollen.

2.2 Disc Separator

Disc separator is similar to the plate centrifuge, only the sewage chamber is made into a flat disc with holes in the center, and each hole is connected into a vertical channel. Due to the large centrifugal force, the sewage is discharged with part of beer. The sewage must to be disposed again, or the loss will be too large. The rotation speed is 5000-10000r/min, and the separation factor is 4000-10000.

The separation process is:

(1) The beer liquid is pushed from the inlet to the drum by the pump pressure (about 3×105Pa) .

(2) When the beer liquid rises through the holes on the discs, it is distributed in the narrow gaps between two discs by the centrifugal force.

(3) Part of the liquor and sewage are called heavy liquor, discharged from the heavy phase outlet. And the clarified liquor is discharged from the light phase outlet.

Advantages:

(1) Large production capacity, suitable for mass production.

(2) The liquid with high solid content can be well treated.

(3) Automatic operation.

Disadvantages:

The heavy liquor must be disposed again by filter.

With the improvement of people’s life and the increasing demand for beer, the production capacity of breweries must be expanded. The use of centrifuges can greatly improve the production capacity of beer. In conclusion, disc separator is a better choice than plate centrifuge.

3. Attentions in Using Centrifuges in Breweries

(1) The centrifuge must be installed on a independent platform to avoid resonance during operation.

(2) When starting, first feed the water until the drum is fully filled. When the drum reaches the full speed, start feeding the beer liquid and stop feeding the water.

(3) During operation, the whole machine should be sealed to avoid losing CO2.