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Winter dewax and Fractionation
The wax in plant oil mainly exists in the shell of oilseed, followed by the cell wall. Wax can be dissolved in oil above 40 ºC, so the crude oil prepared by pressing or leaching generally contains a certain amount of wax.
There are great differences in wax content of all kinds of crude oils. The wax content of most crude oils is very small, but the wax content of some crude oils is higher. For example, the wax content of corn germ oil is 0.01% ~ 0.4%, the wax content of sunflower seed oil is 0.06% - 0.2%, and the wax content of rice furfuri oil is 1 - 5%.
The wax content in general oil increases with the increase of shell content in embryo. If there is a small amount of wax
in the oil, the cloud point can be increased, the transparency and digestibility of the oil can be decreased, and the taste and palatability of the oil will become worse, thus reducing the edible quality, nutritional value and industrial use value of the oil. On the other hand, wax is an important industrial raw material, which can be used in wax paper, waterproof agent, gloss agent and so on. Therefore, the removal or extraction of wax from oil can improve the quality of edible oil and make comprehensive utilization of vegetable oil wax source.
Wintering dewaxing is the process of crystallization and precipitation of higher freezing point in oil by cooling oil. Sunflower seed oil, corn germ oil, rice furfuri oil and other high waxy oil after degumming, deacification, decolorization, deodorization and other refining processes, there will still be a small amount of solid grease precipitation in winter, affecting the appearance and use of oil products, in order to put an end to this phenomenon, these oils need to increase the wintering dewaxing processing process. Under the condition of slow stirring, the oil was cooled to about 4 - 6 ºC in a certain time, so that the wax formed a large crystallization, separated and precipitated, and then filtered to separate the liquid oil from the solid fat. After wintering dewaxing, the oil is not turbid at 0 ºC for 5.5 hours, and the transparency and liquidity of the oil can still be maintained in the refrigerator.
Our company's winter dewaxing complete equipment production line technology is advanced, the equipment is simple and reliable, can meet the requirements of different oil products of winter dewaxing refining.
Winter dewaxing of common oils and fat
1. The sunflower seed oil is cooled to 8ºC in 1 min by quench cooling. The wax crystallization is flake. After filtration, the wax content is less than or equal to 80mg/kg. Small crystals contain less oil and are dispersed well in water, which is favorable for separation. Rapid cooling is favorable for the formation of small crystals.
Process flow.
sunflower oil→preheat→heat exchange→cool→crystal→curing crystal→Filter→oil
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wax
The process
The sunflower seed oil is generally stored in a large tank before dewaxing, and the oil temperature is basically less than 30 ºC, while the melting point of the wax in sunflower seed oil is 79 °81 ºC, so some of the wax in the oil has been precipitated. If the oil is directly used for crystallization and crystallization, the precipitation and crystallization effect of wax in the whole process will be affected, so the oil that has precipitated wax must be heated at the beginning so that the wax is all dissolved in the oil.
The heated oil is first exchanged with dewaxing oil by plate heat exchanger, and then cooled to a certain Temperature into the crystallization tank with frozen brine.
The oil cooled to a certain temperature is further cooled at a certain cooling rate in the crystallization tank. In order to ensure the collision between the precipitated wax molecules and to cool the waxy oil evenly, it is necessary to stir properly. However, the speed should not be too fast, otherwise it will break the particles that have already been crystallization, and it is not conducive to crystallization.
After continuous cooling and crystallization to a certain temperature, the waxy sunflower seed oil stops stirring and maintains for a long time, so that the uncrystalline wax will continue to crystallization and precipitate, and the small grains will continue to grow. The crystallization of waxy oil is self-flowing or pumped into a heat-unloading wintering filter for filtration. In the process of crystallization and crystallization of sunflower oil, with the precipitation of most wax and more solid fat precipitation, in general, the precipitates account for 1-2% of the oil content. Taking this characteristic into account, two large hot unloading winter filters and one wax remover are selected to keep the production continuous.
The filtered oil pump is driven into the plate heat exchanger and stored after heat exchange with the undewaxed oil.
2.Ricebran oil
(1)No. 1 grade Rice bran oil
The solid fat content of rice bran oil was high, including stearic acid 1%-3.8%, palmitic acid 12% -18%, solid fat precipitation at low temperature, muddy oil, solid-liquid stratification and defatting arrangement after acid removal, otherwise fatty acid was solidified before lipid crystallization at low temperature and defatting filtration could not be carried out.
Dewaxing process:
After physical refining, the acid value koh was cooled to 30 ºC at 1 - 3 mg/g, pumped into the skim crystallization tank, slowly and uniformly cooled to 0 ºC for 2 ºC after 24 hours, and kept for 48 hours. Slow stirring was used in the process of crystal culture. In the process of grain culture, the allowable temperature increases slightly by 2 ºC and 5 ºC, and then the filter is pre-coated with diatomite. The filter pressure of the pre-coating is about 0.06mpa, and the filtration temperature is set at 25 ºC. The oil level differential gravity difference is used to filter naturally to avoid the pressure filtration of the oil pump with strong shear agitation, so it is easy to break the lipid crystal. After dewaxing and defatting, the liquid oil is about 90% and the solid fat is 5% - 10% (containing a small amount of liquid oil).
Or the deodorized rice furfuri oil was cooled to about 30 ºC, the crystallization time was cooled for 24 hours, the filter pressure was less than or equal to 0.35 MPA, and the filter oil entered the second crystallization tank. When the oil temperature was less than or equal to 25 ºC and the crystal culture was 24 hours, the secondary filtration was carried out, and the filtration pressure was less than or equal to 0.35mpa. the filter pressure was less than or equal to 0.35mpa. the filtration pressure was less than or equal to 0.35mpa.
(2)No.3-4 grade Rice bran oil
Before decolorization, the content of free fatty acids in rice furfuri oil was high, the acid value koh was about 30mg/g, and the melting point of fatty acids was high. With the decrease of temperature, the fatty acids solidified first, resulting in a sharp increase in the viscosity of rice furfur. at 20 ºC, the rice furfuri oil was very thick and it was difficult to dewaxing and filtering. Therefore, the filtration temperature should be greater than or equal to 20 ºC.
Basic process: after dehydrating rice furfuri oil, pump it into crystallization tank, stir slowly, cool oil temperature to about 25 ºC within 24 hours at 70 ºC, continue to stir slowly (10-15r/min), maintain oil temperature and keep crystal for 48 h, then pump into vane filter to filter diatomite before oil intake. Increasing the filtration temperature can speed up the filtration speed, reduce the oil content of wax paste, but the transparency of oil becomes worse, the filtration temperature decreases, the filtration speed decreases, the wax content in oil is reduced, the cloud point is reduced, and the transparency of oil is improved. The liquid oil is about 90% and the solid fat is 5% - 10%.
Rice furfuri oil dewaxing has a certain decolorization effect. The production shows that the color of y70, r20 rice husk oil decreases to y70 and r12 after dewaxing, which is due to the crystallization and precipitation of brown trivalent iron ion and fatty acid chelate and some pigments with high melting point at low temperature, which are intercepted in wax during dewaxing filtration.
3,Cottonseed oil
Cottonseed oil contains 21.6% palmitic acid, 1.9% stearic acid and 2.4% stearic acid.
The basic process: first heat the oil to 30 ºC 40 ºC, then send it to the crystallization tank, cool the oil to 15 ºC- 20 ºC with cooling water, cool the oil to 6 ºC 8 ºC with frozen water, culture the crystal in the crystallization tank for 12-24 h, stirring speed 10 ≤ 15 r ·min, form the β 'crystal with large particles and high hardness and easy separation, which is a stable crystallization.
In the dewaxing filtration of cottonseed oil, the diaphragm filter should be selected, the membrane of 0.7 mpa should be selected, the filtration pressure is 0.2 -0.4 MPA, and the maximum pressure resistance is 0.5 MPA. 75% liquid oil and 25% solid grease can be obtained by dry dewaxing and defatting.
4,Corn germ oil
Generally contains wax at about 500 mg/ kg, alkali refining acid value koh is controlled at 0.2 ≤ 0.25 mg ·g, 0.2% filter aid is added to decolorizing oil, rapid cooling to 5 ≤ 10 ºC, stirring speed 10 ≤ 13 r / min, crystallization time 8 ≤ 12 h.
It is best to dewaxing and then deodorize, so that the acid value of the filter aid can be avoided and the acid value of the oil can be increased, which exceeds the acid value index of the small packaging oil. The oil temperature in the deodorizer is controlled at 230 ºC.
5,Sesame oil, peanut oil, rapeseed oil
These oils generally do not dewaxing, winter filtration is to meet the needs of the high-end market.
Take rapeseed oil as an example: rapeseed oil contains 20 × 400 mg/kg waxy compounds, of which 60% ≤ 80% is waxy, and the crystallization characteristics are difficult to detect, sometimes a few days and months before precipitation occurs. The decolorized oil was cooled to 5 ºC, the crystallization time was 24 h, 0.1% filter aid was added into the filter, and the wax and solid fat of long chain fatty acids with high melting point were removed.
Fractionation process
According to the difference of melting point between different and fatty acid TG in oil, the high melting point components are crystallization by cooling, and the different melting point components are obtained by filtration or centrifugation. Split extraction is a completely reversible physical modification method based on thermodynamics. A certain oil is extracted into two or more components, each of which has different uses.
At present, dry extraction process has been widely used in the separation of a variety of oils and oils, and can produce a variety of oil products, such as glycerol oleate, super stearid, special oil and fat for food.
In the aspect of controlled cooling technology, according to the characteristics of raw materials and product requirements, plc controls the cooling rate by selecting crystallization conditions and separation temperature. Usually, the oil is cooled according to the predetermined cooling water temperature curve, or according to the temperature difference curve between the oil and the cooling circulating water, in order to form a suitable seed and control its growth, which provides a good condition for filtration.
Adopt the fractionation process developed by our company, the oil can be extracted into multi-purpose extraction products in order to meet the different needs. At present, our company installed a number of sub-extraction oil plant work is very good.
Main equipment:crystallization tank, filter aid tank, filter press, refrigeration unit, water pump, oil pump, cooling tower, etc.
For example:Palm oil fractionation process
CPO (RBD)
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preheat→heat exchange→cool→crystal→curing crystal→Filter→olein oil{24 /33/44degree}
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Stearin
Capacity :1-1000tons/day
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