The Process Optimization Of Microwave Pyrolysis Technology In Oil-Based Drilling Cuttings Treatment

The shale gas reserves of China are at the leading position in the world.In the global development strategy,the exploitation of shale gas has become an important guarantee for the development of the national economy.The rapid economic development in our country has directly led to the increasing demand for energy and increased the exploitation of non-conventional energy such as shale gas.As a result,the oil-based drilling cuttings has rapidly increasing,causing serious environmental pollution.In this paper,microwave pyrolysis was used to pyrolysis oil-based drilling cuttings,which were analyzed by elemental analysis,particle size analysis,ICP-AES,XRD,FT-IR,TG,SEM,GC and GC-MS.The results showed that the volatile,ash and fixed carbon content of oil-based drilling cuttings were 13.02%,85.41%and 1.57%,respectively.In volatile matter,the content of water and oil was 4.59%and 3.34%.In the ash,the main minerals are quartz,calcite,iron sulfide,hematite,kaolinite,muscovite and lime,etc.,of which the highest content is quartz;the content of S,Ba and Si is high in the element.The results showed that the temperature characteristics and pyrolysis results of oil-based drilling cuttings was related to the microwave power,the quality of oil-based drilling cuttings,the mass fraction of water and the flow rate of N₂.The higher the microwave power and the greater the water mass fraction and quality create a higher heating rate and a better treatment effect.However,the N₂ flow rate has a little effect on the temperature characteristics and pyrolysis results.In addition,the final temperature and the pyrolysis time are also important factor in the pyrolysis effect of oil-based drilling cuttings by microwave,with the increase of the pyrolysis final temperature and the pyrolysis time,the oil mass fraction of residue gradually decreased.The oil mass fraction of oil-based drilling cuttings residue can reach<3‰after each experimental treatment,indicating that it can achieve harmless treatment.The microwave heating and electric heating have obviously different heat and mass transfer characteristic,microwave pyrolysis has obvious advantages in the treatment of oil-based drilling cuttings.When the temperature reached 500℃ by microwave pyrolysis,a large amount of H₂ generate,and C₂H₄ and C₂H₆ show a maximum in their yields.In the meantime,it contains a high content of aliphatic hydrocarbons and heteroatom compounds in recovered oil,while the content of PAHs was lower,so we can find the best oil quality.The higher the microwave power,the lower the solid-liquid yield and the higher the gas yield.As the microwave power decreases,the content of aliphatic hydrocarbons and heteroatom compounds in the recovered oil increases,generating a decrease of polycyclic aromatic hydrocarbons（PAHs）,resulting in the small toxicity and high benefit of recovery oil.When using activated carbon as a microwave-absorbing additive,it has a significant promotion effect on the heating rate.It is favorable for the generation of H₂ and CO₂ gases and the conversion of CH₄ to H₂.With the increase of the proportion of activated carbon,it is obvious that the PAHs decrease and the heteroatom compounds increase,greatly promoting the conversion reaction of the compounds in the pyrolysis oil.