Study On The Release Law Of Phenol In Water And Rock During In-situ Pyrolysis Of Oil Shale

Shale oil,as a significant replacement for conventional sources of energy,has an increasingly prominent position in the global resource strategy due to its abundant resource reserves.In-situ mining of oil shale has obvious advantages over ex situ mining and is considered to be the most promising mining process.Pyrolysis of oil shale will produce alkanes,olefins,aromatics,as well as benzene series and phenolic substances,and high-temperature heating and strong water-rock interaction during pyrolysis will cause pollution risks to the geological environment and groundwater environment.Exploring the release law of pollutants during in-situ pyrolysis of oil shale is of great practical significance for the protection of groundwater environment during exploitation.At present,most of the relevant research focuses on the pollution process of polycyclic aromatic hydrocarbons and heavy metals,while there is little research on phenol,particularly with regard to its release and migration in water and rock media.Therefore,studying the release law of phenol in water and rock media during in-situ pyrolysis of oil shale is of great theoretical and practical significance for environmental protection and the research and development of in-situ pyrolysis processes during oil shale exploitation.The study titled "Mechanism of BTEX release and polluted aquifer during in-situ oil shale mining(42002260)" is supported by the National Natural Science Foundation of China.This paper takes oil shale in Huadian District of Jilin Province as its research object and conducts experiments on the release law of phenol through water-rock interaction,phenol vertical migration,and PHREEQC simulation.The study has achieved the following results:(1)The main mineral components of oil shale in Huadian District are quartz,pyrite,potassium feldspar,kaolinite,illite and montmorillonite.Through a series of water-rock interaction tests under different temperature and time conditions,it is found that(1)at different temperatures,As the reaction time increases,the concentration of TOC and TPH in the reaction solution increases first and then decreases.Under the reaction condition of 180°C,the TOC and TPH contents were the highest,and the TOC and TPH contents of 1h,2h,4h.(2)The concentration of phenol in the reaction solution increases as the temperature rises,reaching a maximum value of 7.548mg/L at 280 °C.(3)According to the concentration changes of TOC,TPH and phenol,the oil shale rough rock,180°C-2h,180°C-4h,200°C-2h,200°C-4h,280°C-2h,280°C-4h water-rock interaction oil shale samples were characterized by low-temperature nitrogen uptakedesorption isotherm,and it was found that temperature had a certain influence on the porosity and pore size distribution of oil shale,and high temperature would make the oil shale pore diameter larger,and single pores would change to porosity.It promotes the adsorption and release of certain pollutants.(2)Simulation using PHREEQC software,and the influence on water-rock interaction was explored by temperature,pressure,ionic strength and other different conditions,and the main results were as follows:(1)The influence of temperature on the amount of mineral dissolution in oil shale is obvious,especially for siderite,which has been precipitated in aqueous solution at240 °C.The content of quartz in aqueous solution also increases with increasing temperature,and high temperature also promotes the dissolution release of aluminum,silicon and iron.(2)Different salt solutions have different effects on the dissolution and precipitation of minerals.MgCl2 solution can promote the dissolution of kaolinite,siderite,inhibit the dissolution of potassium feldspar,and Na2SO4 solution can promote the dissolution of pyrite.The solubility of Na Cl and CaCl2 solutions for minerals is not much different from that of pure water,and its effect is not as good as that of Mg Cl2 and Na2SO4 solutions.(3)The effect of pressure on the reaction is less than that of temperature and ionic strength,especially on potassium feldspar and quartz minerals,but pressure will inhibit the dissolution of kaolinite.The concentration of Al ions and Fe ions increases with the increase of pressure,and the concentration of Mg ions and Si ions is not affected by pressure.(3)The results of phenol vertical migration experiments show that under the same temperature conditions,the TOC release in oil shale that has been fully pyrolyzed shows an overall increase trend with longer holding times,while the TOC release in oil shale that has not been fully pyrolyzed shows the opposite trend.Both partially and fully pyrolyzed oil shale exhibit a similar release pattern for phenol.The phenol release increases initially with temperature and then decreases,reaching a turning point after eight hours of heating.The release law of phenol differs from TOC,indicating that there is no correlation between the two.Indeed,the release patterns of both TOC and phenol suggest that temperature plays a crucial role in driving the upward migration of organic matter in the oil shale layer.As temperature increases,organic matter tends to migrate upwards.