Fractional Crystallization System for Fish Oil Winterization

Winterization is a specialized method of crystalline separation, strategically designed to segregate various components within oils and fats based on their freezing points. Specifically, it facilitates the precipitation of higher-melting-point constituents such as glycerides through controlled cooling mechanisms.

Regarded as a specialized form of dry fractionation, winterization is typically implemented subsequent to other refinement procedures including degumming, deacidification, decolorization, and deodorization. Utilizing meticulous control over cooling rates, the fully liquefied oil undergoes low-speed agitation while its temperature is systematically lowered to a range of 0-10°C over an approximate duration of 24-72 hours. This intricate process leads to the formation of sizeable stearin crystals, which can be effectively separated via press filtration units.

The practical applications of winterization are multifaceted. For instance, cottonseed oil undergoes winterization to produce salad oil, while fish oil requires winterization post-refinement to extract stearin. Paint oils are winterized to enhance film resilience at lower temperatures, edible oils are treated to sustain transparency and fluidity under refrigeration, and cod liver oil is winterized to preserve clarity in cold weather conditions.

The efficacy of the winterization process can be validated through a freezing test, wherein the winterized oil must remain free from cloudiness for a minimum duration of 5.5 hours at 0°C.

Dry fractionation is a method of filtering the heated liquid oil after slow cooling and crystallization for a certain period of time without adding other ingredients, depending on the melting point of different fatty acid glycerides.
Dry fractionation is suitable for the separation of fatty acid triglycerides with similar solubility in organic solvents. The components to be separated are highly crystallized and can be separated by filtration or centrifugation. Dry fractionation includes winterization, dewaxing, hydraulic pressure and grading.
This technology has no solvent and catalyst pollution, and is now widely used in the processing of many kinds of fats and oils.

However, there are also problems such as not being able to produce continuously with small volume, the membrane press filter used for filtration is easily contaminated and has a short service life.

Basically, the fish oil winterization and crystallization process is in accordance with the following steps: loading preheating, cooling and stirring, cooling and crystallization, filtration and de-crystallization procedures.

The batch/continuous winterization (fractionation) production line, which processes 3-300 tons of fish oil per day, can be designed and equipped to meet the requirements for the production of high-quality EPA-rich and DHA-rich fish oil of users. According to the crystallization characteristics of fish oil winterization fractionation, the crystallization tank adopts a unique mixing form, using ZCX variable cross-section axial flow paddles, high efficiency and low power distribution.

The continuous production line can be designed scalable according to the processing capacity, the equipment is smaller and the product quality is better. The disadvantage is that the machine generally runs 24 hours a day, at least a few days can not be stopped, of course, stopping is fine, but need to adjust the parameters from the new, such as qualified oil and then out of the oil.

As different varieties of fish oil freezing point difference is very great, the final product of the freezing point requirements are not consistent, determines the different varieties of fish oil or different uses, so that crystallization process in the winterization  should be flexible!

Fish oil winterization and separation process will be designed with key point and key location automated production, which can realize the automated operation of oil inlet and outlet, oil metering, temperature control, pressure control, flow control, liquid level control, frequency conversion control, crystallization, and crystal preservation process.

In order to reduce the oxidation rate of fish oil, we have designed a nitrogen sealing automatic device in the process, all the crystallization tanks, oil tanks and oil pipes can be filled with nitrogen sealing, self-control of air intake and exhaust, so that the fish oil is not easy to oxidize and rancidity.

If you complete with Thermal Melt Type Filtration Equipment, Liquid oil and crystallized wax are separated by filter cloth, in which liquid oil penetrates the filter cloth and enters the filter plate to flow into the oil tank and then transported to the oil tank by the pump.
Wax or grease can not penetrate the filter cloth because of crystallization into a solid state, and can only stay in the frame of the wax filter plate.
After filtering for a certain period of time, the amount of liquid oil filtered out will become smaller gradually, at this time, stop feeding oil, close all the oil and wax release valves, and then supply heat through the circulating coil in the plate frame.
Then the heat source will be heated to the wax or hard grease inside the wax filtering plate and frame through the circulating coil so that the hard ester will be melted into liquid, and then the wax valve will be opened, and the liquid wax or hard grease will be gathered together, and then transported to the grease tank by the pump to be reused in the industry. In this way, the filtering process is carried out in a cyclic manner.

If you complete with A Membrane Filter Press, Upon filling the filter chambers with well-crystallized fish oil, the material input is halted. Initially, low-pressure compressed air (with 0.2 MPa) passes through the membrane filter plate to pre-compress the wax cake, thereby equalizing its pore channels and enhancing its ventilation properties. Subsequently, the compressed air pressure is increased to 0.6 MPa. This higher pressure, executed through a high-pressure airbag, is effective in thoroughly expelling the oil from the wax cake, resulting in a low oil content and well-formed stearin cake, which will be falling on the belt or tank and transfered for storage.

The purpose of filtration is achieved by this cycle of operation. 

Normally it takes 2 people to operate a winterization process as one person is not safe, but additional manpower is needed to dismantle and repair the equipment if necessary.

Generally, automatic control retains the site’s manual operation. For example, motor start and stop, valve switch, etc.