The starch milk is fed into liquefaction PH adjustment tank measurably , PH is continuously adjusted with adding of Na2CO3 solution by metering pump according to starch milk flow rate, part of the α-starch enzyme is adding to the tank at the same time.
Adjusted starch milk is pumped to 1st.jet cooker to have the 1st. liquefaction done with steam ,the gelatized starch solution is sent to 1st. hold tank and then pumped to 2nd. jet cooker to have the 2nd. Liquefaction done with steam, the hydrolysate is sent to 2nd. hold tank. The other part of liquefaction enzyme is added to the discharge line of the tank.After the solution is pumped to continuous plug flow reactor to complete the liquefaction . The temperature is been cooling to 60℃ before goes to the Saccharification unit.
Adding Hcl continuously to adjust the PH value according to the hydrolysate flow rate ,and has the saccharification with the help of enzyme,during the process
stir it to make the saccharification goes evenly ,after achieve the required DE value ,the material is sent to the next unit.
4.Vacuum rotary drum filtration
The saccharified material contains lots of protein-based insoluble impurities that difficult for filtration. It adopts diatomite precoating vacuum drum filter to do the filtration ,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.
Adding 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 filtered.
6.Ion Exchange refining
After the filtration of soluble and insoluble impurities, there still exist 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 exchange resin, while the anion is exchanged with the OH- of anion exchange resin, then the exchanged H+ and OH- inside the saccharified material is combined to water ,the inorganic impurities came to corresponding water for filtration.
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.
In the Evaporation section the dextrose syrup will be concentrated to 77% dry solids by means of a four stage falling film evaporator with thermal recompression.
The raw material dextrose syrup is going to a buffer tank, then the product is pumped through the preheaters and into the first stage , then is pumped into the second stage, the third stage and the forth stage. After the forth stage the product is pumped to the next process section (Crystallization)
From the evaporator the product is led to a buffer tank, in which sodium hydrogen sulphite is added, in order to avoid fermentation during crystallization.
In the crystallizers, the crystals increase in size in the saturated solution. For the initial start-up, seed material has to be added.
Each crystallizer has a cooling jacket and a cooling coil running around agitator. Cooling water is pumped through the jacket and the coil in the crystallizer, which is important for two reasons:
a To remove the heat of crystallization.
b To cool down the dextrose massecuite in such a way that the uncrystallized solution can be kept super saturated and further crystallization can take place.
The product coming from crystallizers consists of dextrose monohydrate crystals and hydrol. To separate the hydrol from the dextrose crystals several basket centrifuges are provided.
The centrifugation process consists of a number of different steps all controlled by a PLC unit.
10.Drying and Bagging-off：
The product coming from the centrifuges has a moisture content of approximately 13-15%. In the drying section the water is removed so that the moisture out of the dryers is approximately 9.1%.
The dextrose monohydrate is transferred from the centrifuges by means of a conveyor system to the air flow dryer. Then the product is discharged by a rotary valve to the back-mix cooler. In the first section the partly dried product from the air flow dryer is dried with hot air(temperature≈70℃) to its final moisture content of 9.1%. In the second section the product is cooled with cold air(temperature≈25℃) to 30℃.
The product from the back-mix cooler is by a rotary valve transferred to the silo. From the silo the final product is transported by a conveyor to the bagging-off system