Composite Solvent Extraction-co-processing Of Oil-bearing Drill Cuttings In Cement Kilns

With the increase of shale gas exploitation in China,the production of oil-bearing drilling cuttings increases rapidly,which is accompanied by more and more serious pollution problems.At present,the pollution of oil drilling cuttings has become a complex environmental problem that attracts more and more attention.Therefore,the disposal of oil-bearing cuttings is indispensable.Aiming at the oil-based drilling cuttings produced by shale gas drilling operation,solvent extraction method was used to deoil and select compound extractant,and the experimental conditions were optimized.At the same time,the extraction process and extraction mechanism were analyzed from the thermodynamic point of view.Combining with the cooperative disposal method of cement kiln,The extraction solid residue was used as raw material to sinter cement clinker,and the effects of mixing method and proportion of raw material on the sintering process and sintering minerals of cement were investigated.Different solvents were used to extract oil-bearing drilling cuttings.The final selected compound extractant was composed of hydrocarbon extractant A,hydrocarbon extractant B and petroleum ether(volume ratio 6:4:1).At the same time,the deoiling rate is significantly affected by the ratio of agent to chip.Through the comprehensive analysis of the deoiling rate of different agent-chip ratio under 35 min extraction time,4:1 agent-chip ratio is an ideal choice for solvent extraction of oil-bearing cuttings.The optimum extraction conditions were as follows:extraction temperature 35?,extraction time 35 min.stirring rate 130 r/min,salt addition 1%.Under the optimum extraction conditions,the residual oil content was reduced to 0.57%.Under the optimum extraction conditions,the requirements of "Technical Requirements for Comprehensive Utilization of Oily Sludge Resources and Pollution Control in Land Petroleum and Natural Gas Exploitation"(SY/T7301-2016)were met.At the same time,the recovery rate of compound extractant reached 80%.The process of oil removal by solvent extraction was analyzed from the thermodynamic point of view.G<0 indicates that oil desorption is a spontaneous process;H>0 indicates that oil desorption is an endothermic process,and temperature is an important factor affecting oil desorption;S>0 indicates the intensity of reaction in oil desorption system;infrared spectroscopy analysis of drilling cuttings samples with different extraction time shows that oil molecules and oil molecules are in the process of oil desorption.The essence of the strong interaction between solid particles is the existence of O-H…O,which hinders oil desorption and reduces extraction efficiency.In order to dispose the solid waste safely,the muffle furnace was used to simulate the codisposal of cement kiln.The mixing mode and proportion of extraction residue have influence on cement products.Thermogravimetric analysis was used to analyze the influence of the addition of extraction residue solid waste on cement firing process.The results show that the decomposition temperature of calcium carbonate decreases by 13.2?.the solid phase temperature decreases from 1173? to 1151?,and the solid phase reaction temperature decreases by 22?.Therefore,the addition of extraction residue solid waste is more conducive to cement clinker.The content of f-CaO in cement clinker was determined by using ethylene glycol substitution method.The results showed that the content of f-CaO in clinker could be reduced by adding appropriate amount of residual solid waste(less than 20%).However,if the content of f-CaO was too large,the content of f-CaO would increase,which would be disadvantageous to clinker firing.Therefore,the maximum content of f-CaO in cement clinker was 20%.The X-ray diffraction pattern of cement clinker showed that the residual solid waste could be extracted.The main mineral composition of sintered cement clinker remains unchanged,but the addition of extractive solid still affects the formation of cement minerals.Therefore,the proportion of extractive solid waste should be less than 20%.At the same time,XRD spectra of cement hydration samples show that the addition of solid waste has an impact on the hydration rate,which will inhibit the hydration reaction rate of cement,which has become one of the main factors restricting the expansion of waste utilization ratio.At the same time,the leaching concentration of heavy metals in cement synergistic disposal products mixed with residual solid waste conforms to the safety limit of "Technical Specification for Cooperative Disposal of Solid Waste in Cement Kiln"(GB3 0760-2014),and there is no environmental safety risk of heavy metal leaching.