Study On Co-pyrolysis Characteristics Of One-component Biomass And Oil-based Drill Cuttings In Shale Gas Development

Oil-based drill cuttings as a kind of hazardous solid waste,must be discharged after reaching the standard.Due to its high oil content,which can be recycled,oil-based drill cuttings have great research significance.As a renewable energy source,biomass has always been the focus of energy researchers.Both pyrolysis oil and small molecule non-condensable gas can be obtained by pyrolysis.However,pyrolysis of oil-based drill cuttings has the problems of low pyrolysis oil yield and high harmful gas content.Biomass pyrolysis oil alone contains high levels of oxygen-containing harmful substances such as aldehydes and phenols.At present,no studies have been reported on the co-pyrolysis of oil-based drill cuttings and biomass.Therefore,whether co-pyrolysis can produce synergy to reduce the generation of harmful substances and increase pyrolysis oil yield is a field worth investigating.In this paper,the pyrolysis oil was prepared by a fixed-bed reactor.The residual oil content and the change of the yield of each phase before and after pyrolysis were analyzed.The TG,SEM,XRD,GC-MS,and TG-MS tests were performed to analyze the pyrolysis kinetics,solid-liquid vapor product composition,and to investigate the interaction mechanism.This study has the following results:（1）Co-pyrolysis has a synergistic effect through activation energy study:Thermogravimetric analysis was used to pyrolyze them at different heating rates and different mixing ratios.By comparing the deviation of their theoretical curves and actual curves in different temperature zones,it was preliminarily determined that their co-pyrolysis had a synergistic effect at 200-450°C and higher than 750°C.The Coats-Redfern integral method was used to analyze the thermogravimetry results from 320 to420°C.Comparing the calculated value of activation energy with the actual value,it was found that co-pyrolysis can reduce the activation energy of the reaction,confirming that co-pyrolysis with the appropriate ratio can promote each other.（2）Research found that co-pyrolysis can improve the yield of pyrolysis oil in shale gas development oil-based drill cuttings:They are individually and co-pyrolyzed under different conditions by a fixed bed reactor.It was found that co-pyrolysis can increase pyrolysis oil yields for oil-based drill cuttings.Combining the effects of four single factors on the oil content of the residue and the liquid yield,the optimum pyrolysis conditions were pyrolysis temperature（350°C）,final temperature holding time（60min）,heating rate（10°C/min）,and nitrogen flow rate（0.15L/min）.Under these conditions,the contents of co-pyrolysis ash total oil,petroleum,animal and vegetable oils were 1717.0590,717.3206,and 999.7384 mg/kg,respectively.Continuing to increase the temperature,extend the time,slow down the temperature increase,and increase the nitrogen flow rate can’t significantly increase the liquid phase yield and reduce the oil content,but only increase the energy consumption.（3）Preliminary discovery of the co-pyrolysis target product regulation mechanism:By analyzing the oil content of pyrolysis residues under different mixing ratios,the total oil and petroleum content showed a downward trend as a whole,and the content of animal and vegetable oils as a whole showed an upward trend.Comparing the weighted average residual total oil calculated with the actual value,combined with elemental analysis of the H/C ratio and XRF,ICP-MS analysis of the alkali metal content,it was found that the co-pyrolysis can produce favorable synergies.The promotion effect increases first and then decreases,and the promotion effect is the smallest when the content is 5:5.Continue to increase the biomass content,and the promotion effect increases first and then decreases.（4）Research found that co-pyrolysis can reduce harmful components in pyrolysis oil and tail gas:Combined with the SEM and XRD results,it was found that biomass and mixed samples was pyrolyzed to form a square crystal,which is a potassium salt.By GC-MS analysis,as the biomass content increased,the hydrocarbon content in the co-pyrolysis liquid phase product gradually decreased,and the content of oxygenates such as aldehydes and ketones increased.For biomass,co-pyrolysis with oil-based cuttings at an appropriate mixing ratio can effectively reduce harmful components in the pyrolysis oil.When the content of oil-based drill cuttings is 70%and 80%,the harmful components can be reduced from the initial 74.92%to 22.74%and 17.57%,respectively.By TG-MS analysis,they found that the main products of their individual and co-pyrolysis include CH₄,NH₃,H₂O,CO,C₂H₆（CH₂O）,CH₂OH,CO₂.Separate pyrolysis of oil-based drill cuttings produces SO and SO₂,indicating that co-pyrolysis can reduce harmful gas emissions.In summary,the co-pyrolysis characteristics and products were studied to show that the co-pyrolysis can produce a synergistic effect,reduce the generation of harmful substances,and increase the pyrolysis oil yield,which has a good application prospect.