Comprehensive Dewaxing Techniques in Edible Oil Refining from HUATAI

The dewaxing process for edible oils is based on the difference in melting points between wax and oil, as well as the characteristic that the solubility of wax in oil decreases with lowering temperature. By cooling and precipitating crystal wax, and then filtering, the separation of wax and oil is achieved.

Huatai Group employs various dewaxing methods: conventional method, solvent method, surfactant method, combined degumming and deacidification method, and others like coagulant method, urea method, electrostatic method, etc. Although the auxiliary means used in different methods vary, the basic principle falls under the category of freezing crystallization followed by separation. Based on the difference in melting points between wax and oil, and the characteristic that the solubility (or decomposition degree) of wax in oil decreases with lowering temperature, crystal wax (or a mixture of wax and crystallization aid) is precipitated through cooling, and then separated by filtration or centrifugation to achieve oil-wax separation.

The dewaxing process flow is as follows:

refined oil → pre-cooling → crystallization → maturing → filtration → finished oil.

Pre-cooling tank:

Since the temperature of refined oil wax is high, the pre-cooling tank is used to cool the oil temperature in advance, reducing the cooling time of the crystallization tank.

Crystallization tank:

The cooled oil is directly pumped into the crystallization tank for crystallization. During crystallization, the stirring speed is slow, generally 5-8 revolutions per minute, to ensure uniform cooling and achieve the desired crystallization effect.

Maturation tank:

After crystallization, the wax is matured to provide conditions for wax fat crystal growth. The temperature is generally controlled between 15-25°C.

Filtration:

The matured oil is first filtered by its own pressure, and when the filtration speed slows down, the variable frequency screw pump is started and adjusted to a certain speed for filtration, thereby achieving the separation of oil and wax.

The main components of the complete dewaxing equipment include maturation crystallization tanks, filters, dewaxing oil tanks, wax paste boxes, refrigeration units, frozen brine tanks, gear pumps, pipeline pumps, and various other equipment.

The principle of oil dewaxing is to utilize the different solubilities of oil and wax. Below 40°C, the wax will gradually crystallize and precipitate as the temperature decreases. During dewaxing, the temperature of the refining equipment must be kept within a reasonable range. Excessively high temperature will result in incomplete wax precipitation, while excessively low temperature will lead to increased loss, both of which are unacceptable. The dewaxing temperature and time have a significant impact on the quality of the treated oil, directly affecting the color and transparency of edible oil.