The recovery screens are designed with a rotating tubular screw holding a nylon mesh screen of 50 to 75 microns that filters the effluent water and retains the meat particles lost in the effluent water of the rotary screens in the surimi process.
The liquid slurry containing the solid particles is transferred by positive displacement pump into the rotating drum covered with the nylon mesh screen in a screw shape that carries the recovery meat from one side of the rotating screen to the other while filtering the effluent water.
The recovery screen is equipped with a water shower and a single or double water spray carried back and forth from one side to the other by a chain conveyor to clean out the solids that gradually clogs the filtration material. The technology developed by Surimi Tech includes both washing capabilities (shower and by chain spray). The rotation speed is controlled by inverter to let the surimi processor adapt the washing system and the speed to the effluent characteristics and maximize the filtration capacity while minimizing the water consumption in the process.
Removing fat from the waste water before filtration is of primary importance since even a small amount of fat will quickly plug the nylon mesh and prevent filtration. Special defatting tanks are designed for this purpose. The efficiency of the filtration and required frequency and intensity of the cleaning of the filtration screen depends on the kind of fish processed and primarily on the presence of residual fat in the waste water.
When a spray system with chain conveyor is used, the speed of the conveyor should be synchronized with the rotation of the screen so that the solids and fat removed from the filtration screen moves forward from the entry to the exit side of the machine and is finally being expulsed out when the spray reaches the end of the rotary screen. Otherwise the fat will immediately clog the material again after one rotation of the screen.
The recovery system system should include at least 2 nylon mesh recovery screens: the first one will collect the meat particles from the waste water of first rotary screen which is usually of darker color and contains a high concentration of protease that would affect the quality of the recovery meat. The meat recovered by the first nylon mesh is then mixed with the second and third waste water and the screw press water to clean out the enzymes and the dirty water carried with the first recovery meat. The recovery fish meat is finally transferred to a small screw press for final dewatering.