Direct solvent extraction and pre-pressing solvent extraction are two common technological methods in the process of oil extraction in oil mill plant, and they are different in operation flow, application scope and final output. The following will be a brief analysis of the two respectively.

Direct solvent extraction 

Direct solvent extraction refers to the process of directly soaking or spraying oil raw materials with solvents (such as n-hexane) after pretreatment such as crushing, so as to extract oil. This method is suitable for raw materials with low oil content. Because there is no need to press, the operation process of direct solvent extraction is relatively simple, the equipment investment is less, and the oil extraction rate is higher. However, because the raw materials have not been pressed, the cake obtained by direct solvent extraction may contain high solvent residue, which needs further treatment to ensure safety. In addition, direct solvent extraction requires high on the crushing degree of raw materials, and usually needs to achieve finer granularity to increase the contact area with solvents and improve the efficiency of oil extraction.

Pre-pressing solvent extraction

Pre-pressing solvent extraction is to extract some oil from raw materials with high oil content by mechanical pressing to obtain virgin crude oil and cake with low oil content, and then extract the remaining oil from the cake by solvent extraction. This method combines the advantages of mechanical pressing and solvent xtraction, and is suitable for treating raw materials with high oil content. The advantage of pre-pressing solvent extraction is that mechanical pressing can reduce solvent residue in cake and improve production efficiency at the same time. Compared with direct solvent extraction, the process of pre-pressing solvent extraction is more complicated, but the final oil and cake quality is higher.

The main differences between direct solvent extraction and pre-pressing solvent extraction

1. Suitable raw materials: direct solvent extraction is suitable for raw materials with low oil content, while pre-pressing solvent extraction is more suitable for raw materials with high oil content.

2. Technological process: direct solvent extraction eliminates the pressing step, while pre-pressing solvent extraction includes two steps: pressing and solvent extraction.

3. Equipment requirements: direct solvent extraction requires more efficient crushing equipment, while pre-pressing solvent extraction requires press and solvent extraction equipment.

4. Product quality: the quality of cake and oil extracted by pre-pressing is usually better than that by direct solvent extraction.

Generally speaking, direct solvent extraction and pre-pressing solvent extraction are two common process methods in oil mill plant, each of which has its own advantages. The specific choice of which method needs to be decided according to the characteristics of raw materials, production demand and economic benefits.