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Subcritical technology
Subcritical technology


Extraction method on 1855 by E.Deiss ( France) initiative, has formed the scale of industrial production in 1870. Application of oil extraction method so as to improve the utilization rate of plant oil. So far, oil extraction used solvent at least 12: carbon disulfide; Crude hydrocarbon gasoline; ethanol; Water extraction method; Petroleum hydrocarbons; Benzene; halogenated hydrocarbons; Isopropyl alcohol; Aldehyde, furfural and acetone, butanone; Ketone, etc.; Supercritical carbon dioxide; Mixed solvent.
At present, the domestic edible vegetable oil extraction using 6 solvent, foreign oil leaching by industrial n-hexane, but also the use of pentane, octane etc.
No. 4 solvent (mainly liquefied propane, butane ) both subcritical extraction technology of oil extraction technology, is a new kind of oil production technology, compared with the widely used 6 solvent oil extraction technology, it has remarkable economic benefit and social benefit. The advantages of its first " cold leaching, low temperature desolventizing ", can extract oil without destroying the active substance, plant protein in the oil situation, create conditions for the development and utilization of plant protein extraction and the precious oil. Secondly, less steam consumption, coal consumption is decreased by more than 80% oil production process, thereby reducing the cost, reduce the " three wastes" emissions. At the same time compared with supercritical fluid extraction, with low cost, the advantages of scale can be large, is now fully replace supercritical technology.
2.Subcritical both No. 4 solvent extraction oil principle of [1]
No. 4 solvent is purified from liquefied petroleum gas, its main components for propane, butane, boiling point was below 0 ℃. The leaching process is under a certain pressure ( 0.1 ~ 0.7Mpa state of liquid ) and room temperature to achieve temperature, leaching of oil. The leaching dregs and in crude oil at low temperature, solvent was removed under vacuum, recycled solvent after liquefaction. The production flow chart and the brief description of the process ( see chart 1).
Figure 1: schematic diagram of extraction process
The E201 condenser P201 solvent pump P202 finished pump vacuum pump P203 P204 compressor V201 leaching tank mixed liquor storage tank V202 V203 evaporation tank V204 solvent tank buffer tank V205
The process is: 
(1) The oil into the leaching tank V201; 
(2) The solvent pump P201 will be No. 4 solvent into the leaching tank immersion oil; 
(3) The solvent pump P201 out of mixed oils from leaching tank into the evaporator V203; 
(4) Unicom leaching tank and the compressor suction port to P204, meal residual solvent gasification, into the compressor, after compression, condensing and liquefying solvent refluxing condenser E201, solvent turnover tank V204, recycling use. Meal exhaust extraction system;
(5) Mixed oil into the evaporation system, the No. 4 after evaporation of the solvent separation and crude oil. Solvent vapor compressed liquefied recycling. Hair oil discharge leaching system.
35 ℃ extraction temperature, extraction pressure 0.4 ~ 0.7Mpa, 3 ~ 5 times leaching times ( depending on how much oil content set ); mixed oil concentration of 15 ~25%, temperature 30~ 35 ℃, mixed oil evaporation temperature 45~ 60 ℃, mixed oil dissolving vacuum -0.095 Mpa; desolventizing temperature 45 C, dissolving pressure -0.085 Mpa; hair oil residue solvent <30ppm, meal residual solvent <50ppm.
3.Comparison of 3 product quality
No. 4 solvent with low boiling point components, pure, leaching of residual solvent leaching process are low, low temperature, good selectivity, leaching amount of pigment, phospholipids and other impurities less, therefore, the high quality of the products. The following and No. 6 solvent oil quality comparison:
3.1 Leaching dregs of good quality
Table 1: Comparison of quality of meal leaching


No. 4 solvent to meal

No. 6 solvent evaporation meal

colour and lustre


Light yellow

Liquid asphalt(%)



Residual solvent(mg/kg)



The soluble protein content(%)

90—93 Stabilize

74—85 Instability

3.2 Extraction of oil with good quality
Table 2: Comparison of oil leaching

Item index         

No. 4 solvent extracted crude oil

No. 6 solvent extracted crude oil

colour and lustre

Yellow 70    red 3

Yellow 70, red 5.5

Acid value



The content of lecithin(%)



Residual solvent(mg/kg)



4.Analysis of 4 economic, social benefits
Subcritical extraction is No. 4 solvent oil extraction technology, is an innovation of oil extraction method, and has great economic benefit and profound social significance, it can not only greatly reduce oil processing costs, but also for the extraction of valuable oil and plant protein, development and create conditions. In the aspect of environmental protection, will make fundamental changes occurred in the oil industry development. Is mainly reflected in the following aspects:

4.1 Meal low temperature desolventizing

No. 6 solvent extraction production at present, due to the solvent boiling range of 60~ 90 ℃, removal of meal and oil solvent shall make its temperature up to 100℃, resulting in the degeneration of plant protein meal. However, the introduction of low temperature desolventizing complicated operation, high consumption, resulting in low temperature desolventizing meal cost is too high, the development and utilization of still greatly hindering the plant protein resource. No. 4 solvent oil extraction process with a simple method to realize the low temperature desolventizing, avoid the degeneration of plant protein, opened up a vast range of plant protein resource, will have a certain impact on people's diet structure, far-reaching social significance. At the same time, meal utilization value improvement will also bring economic benefits.

4.2 Implementation of the pharmaceutical, chemical aspects of quality extraction

Because the production of the technology of low temperature ( <40 ℃), little effect on the thermal material oil and meal such as vitamin, bioactive substance, pigment, can achieve quality leaching valuable oil, such as the microbial oil peanut four acid, Ganoderma lucidum spore oil, amaranth seeds of Hippophae rhamnoides, month, wheat germ, black currant seed etc. At present, the technology built in Wuhan ALKING, WuHan FuXing microbial oil extraction plant running well, the indicators are in line with the requirements of.

4.3 Solution of low energy consumption, steam consumption

No. four solvent oil, due to the design of the novel " process system internal heat exchange technology " and the solvent evaporation, easy recovery, thus saving a lot of solvent and steam, general situation: the consumption of solvent£ 5kg/t£ 60kg/t, steam consumption. The No. six solvent flash Desolventing solvent consumption of 35 ~ 45kg/ is about t, the steam consumption of about 300kg/t.

4.4 Reduce the pollution of the environment

Because the steam the process system using very little, so to reduce boiler coal, electricity and manpower consumption at the same time, reduced because of dust, waste residue, waste burning coal emissions, thereby reducing the pollution of the environment.

 Table3 : No. four solvent toxicity





Toxicity level

Tiny poison

Tiny poison

Low mammalian toxicity

4.5 Solvent with high safety factor

Table 4 : Comparison of safety coefficient of different solvent


Propane ( No. four 

main ingredients )

Butane ( No. four main

 ingredients )

Hexane ( six main ingredients )

Low explosion limit





 The explosion limit





The dangerous degree




Natural point




Explosion proof grade

The 1 level a group

The 1 level b group

The 1 level c group

 5 The application field and range

The technology has been successfully applied in marigold yellow pigment, extraction of capsanthin; seabuckthorn seed oil, evening primrose oil, the extraction of grape seed oil and other precious oil; Ganoderma lucidum spore, peanut four acid ( AA ), permethrin, polyester amide pharmaceutical, chemical extraction, purification, good protection of the effective components and active substances are not destroyed.

 Telphone:18637200951      Jinshun Wang

Reference documentation:
1, Qi Kun, Wang Xuede : a study of liquefied petroleum gas of oil extraction oil. China, 1995.2
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