Improving the yield of finished products is the most powerful tool for energy conservation and consumption reduction to achieve green production. The yield is increased, and the consumption of all raw and auxiliary materials will be reduced. Because it is necessary to discharge a part of the by-product glucose commodity mother liquor that cannot be further extracted by crystallization, although there is a chemical weight gain of about 10% of the molecule added with water in the process of starch hydrolysis to glucose, dextrose monohydrate also contains 9% crystal water. Under normal circumstances, the commercial to commercial yield of the finished DMH commodity to starch milk (converted to 14% of the water content of commercial starch) is only about 88% at most, and the dry to dry yield is only about 93%. In order to obtain a better yield level, the following aspects are very important:
The higher the content of impurities (protein, oil, fiber ash, etc.) in raw starch milk, the lower the content of starch, which directly affects the yield of finished glucose. Moreover, when the protein content is more than 0.5% (relative dry matter), it will significantly increase the difficulty of sugar production.
The quality defects of auxiliary materials will also affect the yield of finished products. The quality of enzyme preparation will affect the glucose content (DX) of saccharification solution. The lower the DX of saccharification solution, the lower the yield of finished products; The quality of sodium carbonate, diatomite, activated carbon and acid-base will not only affect the unit consumption in production, but also may increase the refining load of sugar solution, thus increasing the loss of dry sugar in each refining process and affecting the yield of finished glucose; The quality of steam and water also affects the yield. Unstable steam pressure will affect the liquefaction effect and thus affect the saccharified liquid DX. High or low steam PH (caused by poor boiler feed water quality) will also affect the liquefaction effect and increase the ion exchange refining load. The influence of water quality on the production line runs through the whole process. Poor water quality will increase the refining burden, affect the product quality, affect the liquefaction saccharification effect, affect the filtration speed, etc.
In the dry matter content of mother liquor, more than 99% are sugars, of which glucose accounts for about 78%, maltose and isomaltose account for about 20%, and other miscellaneous sugars are maltotriose and tetrasaccharide. The glucose mother liquor of most enterprises is sold directly in the form of commodity mother liquor at a low price. To increase the value of mother liquor by co production means to further process the mother liquor of glucose into other products with higher value. Although the yield of finished glucose cannot be directly increased, it can indirectly increase the yield of finished products by eliminating some of the consumption of raw and auxiliary materials.
At present, there are several directions for further processing of mother liquor in the glucose industry: small proportion of mother liquor of glucose is added to the processing of food grade maltose syrup; Glucose mother liquor is added to the production and processing of food grade F42 fructose syrup; The glucose mother liquor is further processed to produce caramel pigment; Glucose mother liquor is further processed to produce daily chemical grade sorbitol; Glucose mother liquor is further processed to produce feed yeast, etc. The glucose mother liquor can also be directly refined to produce relatively low-grade food grade starch syrup, and its more uses are still under constant research and development.
The glucose crystallization process is also a separation process, which conforms to the general separation theory. The medium purity sugar paste is separated into high purity crystalline sugar and low purity glucose mother liquor through the crystallization process,The following relationship is established:High purity crystal dry matter × Increase in purity=dry content of low purity mother liquor × Decreased purityIn the formula, the increase of purity means that the purity of high purity crystalline sugar subtracts the purity of medium purity sugar paste, and the decrease of purity means that the purity of medium purity sugar paste subtracts the purity of low purity mother liquor.
The yield of finished glucose can be increased by decreasing DX of mother liquor. By using the intermittent horizontal cooling crystallizer and finely controlling the crystallization process, lower injection DX can be used and higher crystallization rate can be obtained, even the mother liquor DX can be reduced to the limit low value of 76%. Even so, a large amount of glucose was taken away cheaply by the commercial mother liquor. The latest technology is to use membrane separation device or chromatographic separation device to separate most of the glucose contained in the mother liquor and return it to crystallization for extraction. The membrane separation device can reduce the final product mother liquor DX to less than 50%, and the chromatographic separation device can reduce the final product mother liquor DX to less than 30%.
Membrane separation is a new separation technology that rose rapidly after the 1960s. Membrane separation technology has been widely used in food, medicine, biology, environmental protection, chemical industry, water treatment, electronics, bionics and other fields due to its functions of separation, concentration, purification and refining as well as its characteristics of high efficiency, energy saving, environmental protection, simple and easy to control molecular filtration and filtration process. Membrane separation is a screening process related to the size of membrane pore diameter. Driven by the pressure difference on both sides of the membrane, and using the membrane as the filtering medium, under a certain pressure, when the stock solution flows over the membrane surface, many small pores densely distributed on the membrane surface only allow the screened small molecules to pass through and become the permeate, while the substances in the screened stock solution whose volume is larger than the micropore of the membrane surface are intercepted at the liquid inlet side of the membrane and become the concentrated solution, Therefore, the purpose of separating, concentrating and purifying the original solution is realized. In addition to glucose, glucose mother liquor also contains maltose, isomaltose and other miscellaneous sugars with a molecular weight of more than twice. Nanofiltration membrane with a molecular weight of 200 is selected to separate and purify the sugar in glucose mother liquor. The rejection rate of miscellaneous sugars can reach more than 86%. More than 60% of glucose can be separated, which is equivalent to an increase of 8% in the commercial yield of finished DMH products to starch milk (converted to 14% of water content of commercial starch), 95~96%.