Solvent De-asphalting Process Of Vacuum Residue Blending With Coal Tar

The soaring price of crude oil and the absence situation of crude oil in China are pushing the research and development of clean coal utilization technology. These technologies include coal oil, coal gas, coal methanol, coal ethylene glycol and etc. Coal tar being refined with vacuum residue is a new method to enlarge the refinery feedstock and enhance the quality of products, which has a high research value and industrial application prospects.In this study, the influences of basic physicochemical properties of vacuum residue blending with coal tar and surface tension of the extract were investigated. The results showed that vacuum residue blending with coal tar can reduce viscosity, metal content, average molecular weight and colloidal stability of the mix materials, that contribute to improve the effect of the solvent de-asphalting process (SDA); but also increased the residual carbon content of mix materials. The results of the surface tension of extract showed that the surface tension of extract decreased and then increases when the addition ratio of coal tar increased. So, blending with little coal tar can reduce the surface tension of raw materials, benefit to improve the properties of DAO. Based on that, a series of research was carried out for SDA of vacuum residue blending with coal tar in a self-designed small pilot plant for SDA with ethyl acetate at atmospheric pressure. The influences of operating conditions such as solvent ratio, extraction temperature and addition ratio of coal tar were optimized. In optimum conditions (extraction temperature is 30℃, solvent ratio is 6:1, addition ratio of coal tar is 10%), DAO yield is 65.01%, its content of carbon residue is 14.95%, content of metal (Ni, V) is 5.27μg/g and 18.75μg/g, content of sulfur and nitrogen is 3.19% and 0.27%. Comparing with SDA of vacuum residue under this condition, yield of DAO increased 3.02%, content of metal (Ni, V) decreased 0.39 ug/g and 0.89ug/g, content of sulfur and nitrogen reduced 0.10% and 0.01%, content of carbon residue increased 0.27%. Based on analyzing the properties of SDA products, we found that blending with small addition ratio of coal tar can increase the extraction efficiency of light component and improve the catalytic cracking performance of DAO. Finally, several advanced analysis methods such as FT-IR and 1H-NMR were employed to calculate the structural parameters of raw materials and establish their average molecular structures. And the solubility parameter of vacuum residue and coal tar were also calculated, they are 17.03 (MPa)1/2 and 17.63 (MPa). The solubility parameter of mix materials which is combined by vacuum residue and coal tar was greater than the solubility parameter of vacuum residue, closed to the solubility parameter of ethyl acetate, so that can increase its solubility in ethyl acetate and improve the effect of de-asphalting.