Analysis of the formation of feed oil loss
Crude oil (called crude oil in the new national standard) is produced by various methods without refining. The main component of crude oil is triglyceride, also known as neutral oil. In addition, the non glyceride components are collectively referred to as impurities. Oil refining is the process of separating impurities from neutral oil through different processes and equipment. It can be seen that oil refining will inevitably bring oil loss, which can be divided into inevitable loss and additional loss.
According to the existing state of impurities in oil, they are divided into suspended impurities, colloidal soluble impurities, fat soluble impurities, moisture and so on. Suspended impurities include sediment, cake, grass fiber, iron and so on; Colloidal impurities include phospholipids, proteins, sugars, etc; Fat soluble impurities include fatty acids, sterols, tocopherols, pigments, hydrocarbons, waxes, aldehydes, ketones, acids, peroxides, etc.
Although the quality of crude oil obtained by different raw materials and processes is different, according to the new national standard of edible vegetable oil, the quality of crude oil must meet the requirements of six indicators: moisture, volatile matter < 0.2%, no odor, insoluble impurities ≤ 0.2%, acid value ≤ 4mgkoh / g, peroxide value ≤ 7.5mmol/kg, solvent residue ≤ 100mg / kg.
The refining loss of oil is related to the impurity content of crude oil and the quality requirements of product oil. The following is an estimate of the loss in the process of refining crude oil that meets the requirements of the national standard into primary oil:
1. Remove the loss of suspended impurities in crude oil
The content of suspended impurities in crude oil is less than or equal to 0.2, and the content of suspended impurities in primary oil is less than or equal to 0.05%. Generally, the oil loss caused by removing suspended impurities is 1.3-1.5 times of that of crude oil, that is, the loss is about 0.2%.
2. Remove the loss of colloidal impurities in crude oil
The main colloidal impurity in crude oil is phospholipid. The content of phospholipid in different kinds of crude oil is also different. The content of phospholipid in soybean crude oil is about 1.1% - 3.5%, that in peanut crude oil is about 0.6% - 1.2%, that in cottonseed crude oil is about 1.5% - 1.8%, and that in rapeseed crude oil is about 1.5% - 2.5%. Although there is no clear requirement for the phospholipid content of the first grade oil, it is required that the phospholipid content should be less than 5mg / kg in order to meet other indexes of the first grade oil. The degumming loss of soybean oil is about 1.5 times of that of phospholipid. Taking soybean oil as an example, the degumming loss is 1.65% - 5.25%. Taking soybean oil containing phospholipid as 1.8%, the degumming loss is 2.7%.
3. Remove the loss of free fatty acids in crude oil
According to the national standard, the acid value of crude oil is less than 4mgkoh / g, and that of primary oil is less than 0.2mgkoh/g. Using chemical refining process, the loss is about 1.5-2.0 times of the free fatty acid content in crude oil, that is, the loss of oil is 3% - 4%. If physical refining process is adopted, the loss is about 1.05-1.2 times of free fatty acid, that is, the loss of oil is 2.1% - 2.4%. Generally, when the acid value of soybean oil is about 2mgkoh / g, the chemical refining loss is about 1.8%, and the physical refining loss is about 1.1%.
4. Remove the loss of pigment in crude oil
The main method of depigmentation in oil refining is adsorption decolorization process, and the loss of oil is mainly due to the formation of oil entrained by adsorbent. The dosage of adsorbent depends on the color of crude oil, which is generally 0.6% - 3%. The oil content of the filtered adsorbent is 25%, and the loss is about 0.15% - 0.75%. The loss is 0.375% when the dosage of adsorbent is 1.5%.
5. Remove the loss of odor components in oil
The odour components in oils and fats are low molecular aldehydes, ketones, acids, unsaturated hydrocarbons, as well as the burnt paste, solvent flavor, bleaching, flavour and odour produced during the processing of oils and fats. In addition, some oils have peculiar odors due to their special components. In addition to free fatty acids, the content of other odor components in the oil is very small, generally not more than 0.1%, but the actual deodorization loss is much greater than that. This is due to the fact that while removing the odor components, part of the oil is hydrolyzed to fatty acids and removed by distillation, and part of the oil is splashed with the stripping steam. The deodorization loss of oil is generally 0.2% - 0.4%. According to the calculation of oil after alkali refining, the deodorization loss is 0.2%.
Based on the above estimation, the loss of soybean oil is about 4.575% in physical refining and 5.275% in chemical refining.
