July 28, 2021
This process utilizes the difference in boiling point of different distillate oils during the distillation of waste lubricating oil, through vacuum distillation, cutting the distillate, and solvent refining the obtained distillate to remove non-ideal components such as colloids and acidic oxides to reach the standard of base oil , The solvent in the extract is recycled and reused. Commonly used solvents such as furfural, N-methylpyrrolidone (abbreviated as NMP) and so on.
1. Compound solvent technology based on furfural solvent
Furfural refining technology, as a traditional and mature solvent refining technology, is widely used in the field of waste oil regeneration. The solvent furfural has good adaptability to oil products, low price, and easy-to-obtain raw materials. The disadvantages of furfural refining are the low dissolving power of furfural solvent, the large ratio of agent to oil, and the increase of energy consumption for solvent recovery. Furfural is easy to crack and condense when it is higher than 230℃, and its thermal stability is poor. Therefore, the use of light hydrocarbon and furfural solvents can not only increase the selectivity of solvents, but also reduce production energy consumption, thereby improving the entire waste lubricating oil regeneration process.
Comparing the refining conditions of the epichlorohydrin-furfural compound solvent and the furfural single solvent for the lubricating oil fraction, the compound solvent composed of furfural and epichlorohydrin in a volume ratio of 1:1 is 25℃ lower than the refining temperature of the single solvent The viscosity index of the refined regenerated oil is increased by 4-6, and the yield is increased by 1%-3%.
Comparing the process effect of furfural single solvent refining and using furfural-fusel compound solvent refining waste oil, the color, yield and viscosity-temperature performance of the oil refined by compound solvent are higher than that of single furfural solvent.
Solvent refining of waste lubricating oil is carried out with furfural and different compound solvents. Including solvents: N,N-dimethylformamide (DMF), n-butanol, isopropanol, etc. Such as: using furfural and DMF as the compound solvent, temperature 80℃, agent-oil ratio 1.5:1, DMF mass fraction 15%, refining time 30 min, yield can reach 91.7%. Furfural and 15% n-butanol are used as a compound solvent under the conditions of a refining temperature of 85 ℃ and a ratio of solvent to oil of 2:1, and the product yield is 88.5%. Furfural and isopropanol are compound solvents, the refining temperature is 75 ℃, the volume ratio of isopropanol and furfural is 1:1, the volume ratio of agent to oil is 1.5:1, and the total oil yield is 72.5%.
In addition, the use of surfactant sodium dodecylbenzene sulfonate or polyether as a co-solvent can prevent the formation of water-in-oil molecular film caused by emulsifiers in waste lubricating oil, thereby increasing the yield of refined oil. The results show that the refining effect of the compound solvent is better than the refining effect of furfural single solvent by adjusting the reaction temperature and the ratio of solvent to oil. The selected compound solvent has the following characteristics: ①The boiling point and heat capacity of the solvent are lower than furfural, which can reduce the recovery temperature of the solvent and reduce energy consumption; ②The density of the solvent is less than furfural, which facilitates the phase separation and reverse flow in the furfural refining process; ③ The solvent has strong selective dissolving ability for the non-ideal components of lubricating oil and reduces the refining temperature.
2. Compound solvent technology based on N-methylpyrrolidone (NMP) solvent
NMP refining technology plays an important role in the field of waste oil regeneration. NMP has good selectivity and solubility for unsaturated hydrocarbons, aromatic hydrocarbons and sulfides. Compared with furfural and phenol, NMP has good chemical and thermal stability, low volatility and low toxicity. However, due to its corrosive solvent recovery equipment, it is expensive, and the distillation and refining process requires large energy consumption and long time, which restrict its use.
In order to improve the selectivity of NMP solvent refining, NMP and related additives are usually used to form a compound solvent. The main additives added are: water and ethanolamine. Jelena Lukic et al. used NMP and water as a co-solvent to refine waste oil. The results showed that the determination of process parameters and the chemical composition of the refined oil affect the electrical properties and oxidation properties of the re-refined oil. The best process parameters are mild extraction temperature, 1% water and NMP, and a low solvent-oil ratio of 0.5.
NMP plays an important role in improving the quality of waste oil and removing organic acids from waste oil.