The starch milk is fed into liquefaction PH regulation tank measurably, add Na2CO3
solution continuously according to the starch milk flow rate to regulate the PH value and add a part of α-amylase at the same time.
Pump the regulated starch milk to 1st. jet cooker to have the first liquefaction done with steam, the gelatinized starch enters into the first hold tank and pumped into 2nd. Jet cooker to have the 2nd. Liquefaction done with steam, the hydrolysate enters into 2nd. hold tank, add another part of α-amylase to the discharge line of the tank, after the solution is pumped to the continuous plug flow reactor to finish the liquefaction, cooling it to be 60℃ for saccharification unit.
Add Hcl to regulate the PH value according the hydrolysate flow rate, and has the saccharification done with enzyme, during the process, stir it to make the saccharification goes evenly, after reach the required DE value, the solution is sent to the next unit
4.Vacuum Rotary Drum Filtration
The saccharified material contains lots of protein and insoluble impurities that difficult for filtration. It adopts diatomite precoating vacuum drum filter to remove the impurities ,since the filter cake on the surface of diatomite is being removed continuously to be always new which make the filtration fast and in depth.
5.1st. Decolorization and Filtration
Add activated carbon to the saccharified material to absorb the organic impurities
(mainly the soluble colored impurities),then filter the activated carbon together with the impurities by pressure filtration.
After the filtration of insoluble and organic impurities, there are still some soluble inorganic impurities in the saccharified material ,they exists in the form of cation and anion, the aim of ion exchange is to remove them, the cation inside the saccharified material is exchanged with the H+ of cation resin, while the anion is exchanged with the OH- of anion resin, then the exchanged H+ and OH- inside the saccharified material is combined to water ,the inorganic impurities came to corresponding waste water. Certainly, to keep the exchange ability of exchange resin ,it usually use acid and alkali to regenerate the cation and anion resin respectively when the exchange ability weakened.
The syrup after ion exchange go through multi - effect vacuum falling film evaporator to remove part of the water, then the concentration will be increased from about 31% to 50%
Add analytical grade solid NaOH (caustic soda flakes) to regulate the PH of glucose solution to be 7.5~7.8
Sent the glucose solution into autoclave ,it reacts with hydrogen under the effect of catalyst to get sorbitol. Hydrogen adding adopts intermittent low pressure( 4.5MPa) inter autoclave sedimentation mode
The hydrogenated solution contains color impurities since the high temperature during the hydrogenation, add activated carbon powder to the hydrogenated solution ,the colored impurities is absorbed by the surface of carbon and be get rid of by press filtration
Filter the activated carbon with the colored impurities absorbed inside the hydrogenated solution by plate-and-frame press filter, the hydrogenated solution become clear and transparent, a part of catalyst remaining inside the hydrogenated solution is also filtered
The hydrogenated solution after decolorization goes through cation exchange column, anion exchange column, mixed bed, cation and anion inside the solution is separated out ,and inorganic impurities(including the residue catalyst)is also basically removed out
The hydrogenated solution after ion exchange goes through the multi-effect vacuum falling film evaporator to remove a part of water, the concentration then increase from about 48% to 70%
Filling the sorbitol liquid after concentration to vessels which are easy for transportation and storage, seal and label well to get finished product liquid sorbitol