Application of Disc Separator in Soy Sauce Production

In the traditional Chinese production of condiments, especially soy sauce and vinegar, the most important process step besides fermentation is to separate the different liquid and solid substances from each other. At present, the commonly used method is to use filter cloth and frame filter. For the pressed soy sauce, the filtering effect of the filter cloth is not ideal, the filter aids are usually added, and it also needs batch production.

Now, the use of filter aids has been gradually restricted due to the increasing high environment requirements in China. Secondary, the rising labor costs will also put forward higher productivity requirements for soy sauce manufacturers. It is better to achieve the goal of simple and reliable process, continuous production, lower production costs and higher yield.

Based on the understanding and grasp of the development trend of the above industries, as a new separation technology, disc separator is proposed in soy sauce production. Disc separator is suitable for the treatment of low solid content and small size of particles and droplets. It is suitable for liquid-liquid and liquid-solid separation. The most difficult separation task usually involves three phases. For example, soy sauce brewed by soybeans contains three phases of water, oil and residue. The density of liquid phase is almost the same, and the particle size is very small. In this case, there is no separation technology comparable to disc separation technology. The main characteristics of disc separation technology are: continuous production for a long time, complete physical separation process, no need for the use of consumable, clean working environment, CIP cleaning, low labor intensity.

The disc separator uses a very high centrifugal force in a continuous working process to separate the solid phase from one or two liquid phases. Under the action of this force, the thicker solid material is pressed to the inner wall of the drum, while the thinner liquid phase is closer to the inner part of the rotating center, thus to form a concentric layer. The contact area of two different liquid phases becomes the interface position. This position can be changed to ensure optimal separation efficiency. The insertion of a special disc (disc pack) can provide a larger surface settling area, which greatly speeds up the separation process. The special configuration, shape and design of these discs enable the separator to continuously separate various solids from one or two liquid phases.

The disc separator is usually composed of four main parts: feeding zone, disc group zone, liquid separation zone and solid slag discharging zone.

Feeding zone: the speed of the treatment fluid can be increased to the speed required by the drum. The unique design of the feeding zone ensures that solids and liquids are fed without degradation or any other impact. The inlet design also can reduce foam, reduce the shearing force in the products, reduce temperature rising and avoid the interference in the drum separation process.

Disc group zone: the efficiency of disc group determines the separation performance, so the design of disc group is very important. Special corrosion resistant materials with high temperature and high chloride ion content can provide specific disc group configuration to ensure that the fluid is evenly distributed among discs according to the optimal flow mode of disc group itself.

Liquid separation zone: after the liquid is separated, it must be delivered out of the separator, the more accurate, the better. In the process of soy sauce production, it is very important to minimize the oxygen entering and avoid the temperature rise of soy sauce.

Solid slag discharging zone: there are three basic ways to remove solid from disc separator, namely: continuous, intermittent and manual. The most suitable way is to combine many factors together, and the most important factors are the solid content in the liquid and the solid dryness after separation.

One of the main challenges faced by disc separator in soy sauce production is that they usually work in a highly corrosive environment and under an abnormal pressure combination of more than 10000 gravitational accelerations. Only a few materials can cope with this situation. High strength stainless steel such as duplex stainless steel and super duplex stainless steel are used in the disc separator. All drum components are forged to ensure maximum reliability. In this way, the drum does not need to use welding technology to ensure that each components has a uniform full phase particle structure, without cracks and defects. At present, the disc separator has provided high-quality two-phase and three-phase separation technology for important soy sauce production enterprises in Southeast Asia, China and Japan, for developing and improving the soy sauce production technology.