The three-phase decanter process is a relatively new separation method of wheat starch and gluten developed in Germany. It is named after the unique patented technology used in the process - three-phase decanter.
The three-phase decanter process also uses flour as a raw material. Try to use flour with high flour extraction rate, high gluten content, low ash content, and low breakage rate that is close to the special second-grade flour.
After the raw flour is quantified, it enters the mixer and mixes with water to form a batter. The ratio of flour to water is about 1:(0.85-0.95). The mixer fully hydrates the flour particles to form a uniform batter, and there should be no uneven mixing of large particles and uneven small dough, so as to facilitate the subsequent homogenization process.
Homogenization is followed by mixing. The batter is put into the homogenizer, and the pressure of the homogenizer can be adjusted by changing the gap of the homogenizer valve, and the pressure can be as high as 100bar (1bar=105ba). When the batter passes through the homogenizing valve, the high pressure quickly returns to normal pressure. Due to the sudden change of pressure and the shearing effect of the homogenizing valve, the batter is matured and the protein network is rapidly aggregated. The equipment used for homogenization is a homogenizer commonly used in the common dairy industry.
The homogenized and aged batter is transported to a three-phase decanter centrifuge with an eccentric screw pump to separate the components. A certain amount of fresh water and process water can be added to dilute the batter before entering the machine. But the water added in this process is less than the Martin method, about 0.3-0.9t per ton of flour.
The decanter centrifuge is a horizontal centrifuge with a screw installed inside. The rotation speed of the screw is slightly different from that of the drum, and the speed difference is about 60r/min. The separation factor of this centrifuge is between 2000-4000. The three-phase horizontal screw adopts the technology of double motor and double reducer, so that the speed difference between the screw and the drum can be adjusted at any time. At the same time, there is a nozzle at the overflow outlet, which can separate the third phase - the middle phase, which is an important difference between the three-phase decanter and the ordinary decanter. The solid is the largest part of the feed, which is propelled by a screw propeller after being separated by a decanter and discharged as an underflow. The overflow is discharged by a built-in centripetal pump, which can force the foamy material formed in the process to be discharged quickly and save a transfer pump at the same time.
Because pentosan is relatively less dense, it is mainly distributed in the overflow. In this way, the viscous material is separated from the gluten at the front end of the process, so that the amount of fresh water required in the process is reduced, and the subsequent gluten separation and product quality are no longer affected by pentosans.
The gluten and water are sent to a continuous mixer in a certain proportion to mix and stir, so that the material is subjected to both axial extrusion force and a certain radial force in the machine. After sufficient kneading, it is the protein in the flour. Evenly contact with water, and produce water and effect, continuously output flour slurry similar to toothpaste. Then it is sent to the ripening pot for ripening. The purpose is to dilute the batter with a certain amount of water, and to free part of the starch after stirring; at the same time, the gluten protein aggregates into filamentous small gluten. At this time, the pump will be transported to a horizontal screw settler with a separation factor of 3000-4000 for separation. The mature batter is separated into two phases during the separation due to the different settling rates of starch and gluten. Starch has a higher density and is output from the underflow of the separator as a dense phase; while gluten has a lower density and is output from the overflow of the separator as a light phase. It is a mixture of gluten and small granular starch, and then washed through a round sieve to remove the starch to obtain wet gluten, which is sent to gluten to be dried and dried to obtain gluten.
The underflow separated by the three-phase decanter centrifuge is usually diluted with process water and sent to a centrifugal screen for treatment to remove residual fibers. Then enter the multi-stage cyclone for washing, usually a 12-stage starch washing cyclone is used. The underflow also contains some small B-starch, pentosan and fine fibers. In order to better separate them, this process uses a vertical high-speed three-phase disc nozzle centrifuge before the cyclone group. Used in conjunction with a cyclone to ensure efficient and thorough starch washing.
The underflow and overflow from the three-phase decanter centrifuge are screened separately to recover more gluten that can form agglomerates. The recovered gluten is processed together with the middle phase in the process, and the obtained wet gluten is further dehydrated and dried to make gluten.
The pentosan in the overflow can be directly used as feed in liquid state, or the solid part can be separated after adding enzymes;
The crude starch milk obtained from the bottom of the decanter is a mixture containing a small amount of fiber and protein, and the fiber can be screened out through a series of three-stage centrifugal sieves. Then it is sent to a drying system to be dried to obtain bran.
The graded and refined A starch milk is sent to the automatic scraper centrifuge for dehydration, and then dried by the air drying system to obtain relatively pure A-grade starch. The B-grade starch milk obtained from the classification system, which has a lower concentration, can use the concentration effect of the decanter to collect the B-starch from the highly dispersed suspension. The small gluten separated from the decanter is filtered and collected after filtering out the starch. After being squeezed and dehydrated, it is sent to the ring-type gluten drying system for drying to obtain gluten.
The three-phase decanter process uses a three-phase decanter centrifuge to divide the material into three phases, and the pentosan is separated and removed at the front end of the process, thus saving the amount of water and ensuring the quality of the finished product. The starch washing is processed by a combination of high-speed three-phase disc nozzle centrifuge and cyclone, so that the purity of starch is higher. Of course, this process mostly adopts imported equipment, the process is more complicated, the operation is more troublesome, and the cost is higher.