| As a new recycling approach, the regeneration of waste lubricating oil gains extensive domestic and international attentions. However, the existing domestic regeneration technology is relatively backward. Therefore, it is difficult to process the regenerated by-products. Furthermore, it also lacks a comprehensive assessment of qualities of waste and recycled oil. The purpose of this thesis was to experimentally investigate regeneration characteristics and blending process of waste gear lubricating oil. It is expected to provide the theoretical basis and technical support for the industrial application of waste lubricating oil regeneration. A combining regeneration process of extraction-flocculation and solvent refining was proposed. High quality blend lubricating oil was obtained by mixing the recycled and new oil. The proposed approach has both economic and environmental advantages comparing to the traditional waste oil regeneration method.The physical, chemical characters and composition of new and waste oil were systematically analyzed. The results suggested that waste oil was a complex compound that had high viscosity, strongly acidic and corrosivity, low viscosity-temperature characteristic and poor safety performance with high content of impurities. According to TG analysis, it showed that the poor oxidation stability of the waste lubricating oil was caused by the low boiling point substance and colloid, asphaltene and other polymers, which were produced by hydrocarbon cracking and polymerization reactions. FTIR analysis indicated that the waste oil contained several organic compounds that did not exist in the original lubricating oil, i.e., acids, aldehydes, ketones, ethers, alcohols, phenols, nitrogen compounds, aromatic compounds, etc. Nevertheless, the waste oil had an abundance of hydrocarbons, which suggested the waste oil was recyclable.In order to improve the quality of waste lubricating oil, experiment system was established to study the characteristics of waste oil regeneration using the extraction-flocculation method. The composite extraction agent was composed of butanone and isopropanol, butanone/isopropanol at a weight ratio of 3:1 was proved to be the best proportion of composite extraction agent. The influences of solvent oil ratio, extraction temperature, extraction time and the content of KOH on the productivity and quality of pretreatment oil were investigated. According to the range and variance analysis of orthogonal experiment,5:1 of solvent oil ratio, 20℃ of extraction temperature,15min of extraction time and 4g of KOH were obtained as the optimum extraction-flocculation condition. The productivity and acid value of recycled oil obtained in this condition were 81.6% and 0.28mg KOH/g, respectively.The comparative experiments were conducted to study the difference between the solvent and adsorption refining. NMP and activated clay were selected as the solvent and adsorbent, respectively. The influences of key parameters on the productivity and acid value of different refining process of recycled oil were analyzed. Comprehensive evaluation was conducted to prove the NMP solvent refining process was the optimal process.4:1 of solvent oil ratio,60℃ of refining temperature,20min of refining time and 12h of settling time yielded the best result. The color of the recycled oil has markedly improved, and the kinematic viscosity, viscosity index, acid value, moisture content indicators were also enhanced under this condition.Finally, the influence of blending ratio of recycled and new oil on physical and chemical properties and lubrication performance of blend oil was studied. The main physical and chemical characteristic index of blend oil were analyzed, including kinematic viscosity, acid value, flash point, mechanical impurity, pour point, and moisture content. The numerical models of physical and chemical properties by blending the prepared new and recycled oil were summarized. The lubrication performance of blend oil as comprehensively analyzed on a four-ball friction tester by extreme pressure, antifriction and wear resistance test. It was found that the recycled-to-new-oil volume ratio as 37.5:62.5 gave the best performance. In light of engineering economic analysis, and designed a set of portable, waste oil regeneration device for subsequent engineering test preparation. |
