Relationship between refining cost and each process of oil preparation and processing
1. The relationship between crude oil preparation process and refining cost
1.1 effect of pretreatment and leaching process on phospholipid composition in crude oil
Whether physical refining or chemical refining is adopted, the content of non hydrated phospholipids in crude oil is one of the important factors that directly affect the refining cost. The content of non hydrated phospholipids in oil is not only related to oil varieties, growth conditions and storage conditions, but also related to processing and leaching conditions. The formation of non hydrated phospholipids is the result of the interaction of the following factors: (1) the higher the water content in oil and the green body after rolling, the higher the content of non hydrated phospholipids. (2) the activity of phospholipase D, The activity of phospholipase is enhanced, which will promote the transformation of hydrated phospholipids to non hydrated phospholipids. (3) the heat treatment of oil before or during leaching, 50 ℃ - 70 ℃ is the active temperature of phospholipase, which should be avoided as far as possible in the process. (4) the degree of damage of oil cells, appropriate temperature of material and sufficient air are conducive to the activities of various enzymes.
In the traditional oil processing technology, the moisture content of oil, the temperature of softening, steaming and frying, and the temperature of leaching are all favorable for the activity of phospholipase. Therefore, it is necessary to improve it. After rolling, the green billet is humidified and heated by direct steam, so that the billet temperature can quickly reach 98 ℃ - 102 ℃, the moisture content is 15% - 16%, the wet heat treatment is carried out for about 40 minutes, and then cooled to 55 ℃ for leaching, which can better inactivate the activity of phospholipase, or the extrusion process can be used under high temperature and high pressure for a short time (130 ℃ - 160 ℃), The content of non hydrated phospholipids in crude oil can also be reduced by sterilization.
1.2 influence of evaporation conditions of mixed oil on color of crude oil
It is necessary to remove the dregs in the mixed oil no matter the atmospheric pressure or negative pressure process is adopted. If the evaporation temperature is higher than 120 ℃, the color of crude oil will turn dark. If the evaporation temperature is higher than 120 ℃, the color of crude oil will be difficult to remove.
2. The relationship between each process of crude oil refining process and refining cost
In terms of production control, it requires the maximum removal of impurities, the minimum loss of oil products, the minimum amount of sewage discharge and the minimum amount of additives.
2.1 degumming process
Degumming process is the basis of the whole refining process, its efficiency will directly affect each subsequent process, and then affect the refining cost. For physical refining, the phosphorus content of degummed oil should be less than 20ppm, so that the phosphorus content can be controlled to less than 5ppm after decolorization, and the quality of product oil and deodorization equipment will not be adversely affected. At the same time, efforts should be made to control the content of neutral oil in oil foot. Therefore, different from the conventional hydration degumming process, acid degumming, special wet degumming, enzymatic degumming and other new processes have been developed.
Acid degumming is to heat the oil temperature to about 70 ℃, add 0.05% - 0.2% phosphoric acid or citric acid, adjust the pH value of the system to dissociate the non hydrated phospholipids, then lower the oil temperature to below 40 ℃, add water to make the phospholipids form stable liquid crystals in a slow state, and these crystals can effectively bind sugars and metal ions. The heavy phosphorus content of oil can be reduced to less than 30ppm by acid degumming.
Special wet degumming is heating the oil temperature to about 70 ℃, adding 0.05% - 0.2% phosphoric acid or citric acid for conditioning, then lowering the oil temperature to below 40 ℃, adding 2% - 3% NaOH solution with concentration of 2% 2.5% to make the liquid crystalline phospholipid hydrated and flocculated, heating the oil temperature to 70 ℃ after reaction, and entering the centrifuge for separation.
2.2 deacidification process
In deacidification process, the ratio of acid value to refining consumption is an important index to measure the level of production process and operation technology. The reasonable process route should be selected according to the variety and quality of crude oil. For the oil with high phosphorus content and high acid value, the long-term mixing process should be selected. On the contrary, the short-term mixing process should be selected. Reasonable adjustment of process parameters, such as stirring intensity, reaction temperature, reaction time, alkali dosage, alkali concentration, excess alkali dosage, etc. The amount of alkali can be calculated by acid value; The alkali concentration is determined according to the variety and acid value of the oil; Due to the uniformity of mixing and the existence of impurities, it is necessary to add a part of excess alkali to supplement the loss of alkali. The amount of excess alkali is very important to the alkali refining effect. The amount of excess alkali is less, the neutralization is not complete, the oil soap is not easy to separate, the amount of excess alkali is more, it is easy to separate, but the saponification part of neutral oil increases the loss of oil.
2.3 decolorization process
The cost of decolorization is mainly the cost of adsorbent and the additional loss cost of adsorbent oil. The adsorbent with large specific surface area, low activity, fast filtration speed, low residual oil and low free acid value should be selected. Large surface area, strong adsorption capacity and low activity can reduce the structural change of oil products after decolorization treatment, strong antioxidant capacity, fast filtration speed can improve the yield, low oil content can reduce oil loss, and low free acid value can reduce the hydrolysis and oxidation of oil products.
In order to reduce the amount of adsorbent, the content of soap and phosphorus in the oil to be decolorized should be reduced as much as possible. During the decolorization, vacuum and good stirring should be kept to avoid oil oxidation and improve the decolorization efficiency.
2.4 deodorization process
The loss of deodorization is mainly the distillation loss of odor components and the splash loss of oil. Therefore, under the condition of ensuring the stripping effect, it is necessary to reasonably control the amount of direct steam, reduce the gas velocity of fraction, increase baffles, reduce gas entrainment and splash loss. Control the reasonable vacuum degree and deodorization temperature, pay attention to the heat recovery of the product oil, and use the product to exchange heat with the deodorized oil, so as to minimize the energy consumption.
4、 Summary
Through the above analysis, through the innovation of oil production process, improving the quality of crude oil is the key; Through reasonable selection of advanced process and equipment, scientific adjustment of process parameters, summary of clear and detailed operation methods, coupled with strict management, the refining loss cost can be reduced, the product competitiveness of the enterprise can be improved, and the economic benefits of the enterprise can be increased.
