Investigation Of Physicochemical Characteristic And Catalytic Mechanism During Gasification Process Of Petroleum Coke

Petroleum coke（petcoke）is the by-product from the oil refining process.Globally,a huge amount of petcoke is produced annually,which brings a heavy load on the environment and enegy consumption.The gasification technology is regarded as a key technology to recover energy and solve the problem of petcoke disposal.However,the poor gasification reactivity of petcoke limits its large-scale industrial application.The physicochemical behaviors of petcoke during gasification determine its reactivity.An in-depth study of physicochemical properties of the products of petcoke gasification can be beneficial for developing strategies for the enhancement of petcoke gasification reactivity.Currently,the study of petcoke gasification reactivity are mainly based on thermogravimetric analyzers and fixed beds.There are few comprehensive studies on the evolution of physicochemical properties during the rapid heating gasification process.The quantitative description of the differential evolution of pore structure and surface morphology is still insufficient.Particularly,the qualitative illustration of the mechanism of carbon structure and micro groups during petcoke gasification is lacking.Firstly,the experiment of petcoke gasification was performed based on a drop tube furnace,which comprehensively investigated the evolutions of solid products and their properties.The devolatilization reaction of petcoke basically completes below 1100°C,which is conducive for the development of the pore structure.The index R,indicating the relative reduction of H/C,can be used to judge the ability of petcoke gasification.The surface morphology of petcoke and its char has fractal characteristics.The petcoke gasification reactivity is mainly affected by temperature and ash.Secondly,an in-depth research on the micro chemical properties of chars was presented.The mechanism of micro groups transformation during petcoke gasification was established.Petcoke with high ash content promotes the decomposition of functional groups to form active radicals,particularly the conversion from oxygen-containing functional groups to hydroxyl radicals,which is beneficial for the formation of amorphous carbon and active sites resulting in the high gasification reactivity.The value of I_D1/I_G,indicating the disorder degree of carbon structure,can also be an indication to understand the gasification reactivity of petcoke.Thirdly,the effect of ash composition on the ash thermal behavior and petcoke gasification reactivity was performed on the fixed bed and thermogravimetric analyzer.The key factors influencing the petcoke gasification were identified.The low ratio of V/Ni,the high ratio of Si/Al,and the ratio of Fe/Ca at 0.5 are beneficial for the ash fusibility and petcoke gasification reactivity because of the melting ash.The catalytic index（R_C）of petcoke gasification reactivity is a function of ash content,active metal elements index（A）and ash fusibility index（C）.The mathematical expression is R_C=M_ASH×A×C.Finally,the catalytic mechanism of petcoke gasification was explored by the co-gasification of solid waste ash and petcoke.The gasification reactivity of petcoke is nearly doubled on the catalytic role of municipal solid waste（MSW）ash at 1000°C where the best catalytic effect occurs at the ash ratio of 5%.The catalytic role of MSW ash enhances the conversion from oxygen-containing functional groups to hydroxyl groups of char.The catalytic role of MSW ash strengthens the decomposition of hydroxyl groups at 1300°C where the coke reactivity index reaches 90.2%at the ash ratio of 3%,but excessive ash has an inhibitory effect on petcoke gasification reactivity.When the temperature is higher than the flow temperature of solid waste ash,the promotion of petcoke gasification reactivity is evident.The ash fusion temperatures can be used as the basis for the selection of blended solid waste ash for the enhancement of petcoke gasification reactivity.