Recovery of waste lubricants requires much less energy consumption than the extraction of lubricants from crude oil. Recycling waste lubricants also protects the environment. Nowadays, there are several ways to recover waste lubricating oil by solvent refining machine.
1. Furfural Solvent-based Compound Solvent Technology
Furfural refining technology, as a traditional and mature solvent refining technology, has been widely used in the field of waste oil recycling. The furfural solvent has good adaptability to oil products。 It has the advantages of low price and easy to obtain raw materials. However, the disadvantages of furfural refining are that the solubility of furfural solvent is small, the ratio of agent to oil is large, and the energy consumption for solvent recycling is increased. Furfural is easily cracked and condensed at a temperature higher than 230 ° C, and has poor thermal stability. Therefore, the use of light hydrocarbons and furfural solvents can not only increase the selectivity of the solvent, but also reduce the energy consumption of the production, so as to improve the entire process of waste lubricating oil regeneration.
In addition, the use of surfactant sodium dodecylbenzenesulfonate or polyether as a co-solvent can prevent the formation of water-in-oil molecular films caused by emulsifiers in waste lubricating oil, thereby improving the yield of refined oil. The results show that the effect of refining solvents is better than that of the furfural single solvent by adjusting the reaction temperature and the ratio of agent to oil. The selected compound solvent should have the following characteristics:
① The boiling point and heat capacity of the solvent are lower than those of furfural, which can reduce the recovery temperature of the solvent and reduce energy consumption.
② The density of the solvent is less than furfural, which facilitates phase separation and reverses the flow of the furfural refining process.
③ The solvent has a strong ability to selectively dissolve the non-ideal components of the lubricating oil and reduces the refining temperature.
NMP refining technology plays an important role in the field of solvent refining. NMP has good selectivity and solubility for unsaturated hydrocarbons, aromatic hydrocarbons and sulfides. Compared with furfural and phenol, the N-methyl pyrrolidone solvent has good chemical stability and thermal stability. Its advantages are low volatility and low toxicity. However, the solvent easily corrodes the solvent recycling equipment and is expensive. Not only that but the shortcomings such as large energy consumption and long time required for the distillation and refining process also limit its use.
In order to improve the selectivity of N-methyl pyrrolidone solvent refining, NMP and related auxiliary agents are usually used as a compound solvent. The added auxiliaries are mainly water and ethanolamine. The results show that the determination of process parameters and the chemical composition of the refined oil affect the electrical and oxidation properties of the refined oil. The best process parameters are suitable extraction temperature, 1% water, and the ratio of NMP to low solvent oil is 0.5.
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