Studies On Physico-chemical Properties Of Resultant Carbons From Different Pyrolysis Processes And Catalytic Gasification Reaction Characteristics Of Petroleum Coke

Due to their different formation processes, carbons from different pyrolysis processes possess of different pysyco-chemical properties, which results in some differences of their gasification characteristics. Therefore, It's imperative for us to investigate physico-chemical properties and gasification reactivity of carbons produced in different pyrolysis processes, thus it can not only strengthen our understanding of their essential properties and the gasification mechanism of carbons, but also enrich the theory of carbon science.Furthermore, due to the increasing output of petroleum coke in our country, it is very imperative to utilize it in an efficient and reasonable way. Therefore, investigating the catalytic steam gasification of petroleum coke not only can enrich the understandings of catalytic steam gasification characteristics of petroleum coke, but also provide basic data and theoretic references for petroleum coke when it is used as the raw material of gasifiers. The main contents and achievements of this study were summarized as follows.(1) Three different carbons were separately prepared from gas-phase, liquid-phase and solid-phase carbonaceous materials at the corresponding pyrolysis temperatures of 1000～1200℃(gas-phase pyrolysis),350～500℃(liquid-phase pyrolysis) and 1000～1600℃(solid-phase pyrolysis). Physico-chemical properties of the three carbons were investigated by SEM, XRD, FTIR, GC/MS, a surface area and porosity analyzer, etc. and their CO2 gasification reactivity was also investigated by an isothermal thermo-gravimetry. Some new cognitions were obtained as follows.①Gas-phase and liquid-phase carbons contained a certain amount of solvent-soluble organic matters. The solvent-soluble organic matters in liquid-phase carbons were of great aboundance, which mainly resulted in a low gasification acitivity of liquid-phase carbons.②The ordered degree of carbon crystalline structure of gas-phase, liquid-phase and solid-phase carbons were low, and the ordering of carbon crystalline structure among the three carbons was as follows:liquid-phase carbon> gas-phase carbon> solid-phase carbon.③The ordering of gasification acitivities of the three carbons was as follows:gas-phase carbon> liquid-phase carbon> solid-phase carbon.(2) Various slow and rapid pyrolysis chars were prepared separately from industrial delayed cokes (petroleum coke and pitch coke) and coals (Shenhua and Yanzhou coals) at the corresponding pyrolysis conditions of high temperatures (950～1400℃) and high pressures (0.1～3 MP), respectively using a high-temperature muffle and a pressurized pyrolysis set-up. Physico-chemical properties of various resultant chars were investigated using SEM, XRD and a surface area and porosity analyzer so on, and their CO2 gasification reactivity was also investigated by an isothermal thermo-gravimetry. The following results were obtained.①Effects of pyrolysis condition on BET surface areas of coal chars are opposite to those on BET surface areas of industrial delayed cokes.②High pyrolysis temperatures, as a whole, were favorable to elevate the gasification acitivity of industrial delayed cokes.③Increasing pyrolysis pressures resulted in the increase of the gasification acitivity of coal chars and the decrease of that of industrial delayed cokes.④The gasification acitivity of industrial delayed cokes was far lower than that of coals and even lower than that of natural graphite.(3) Physico-chemical properties of the ashes from three typical crop straws (rice straw, wheat straw and cotton straw) were investigated by XRF, XRD and SEM/EDS, etc. and the catalytic steam gasification characteristics of petroleum coke, which were catalyzed by various K salts and the three ashes, was investigated using a fixed-bed gasification set-up. The following results were obtained.①At high temperatures, various minerals reacted each other to form amorphous compounds, resulting in the deactivity of metals from straw ashes.②A proposed method for calculating the selectivity towards CO and CO2 could be used to understand the steam gasification behaviours of carbons.③Among various K salts and straw ashes, K2CO3 and the ash from cotton straws respectively had the highest catalytic activity. There were no effects of their contents on the distribution of gas products and the selectivity towars CO and CO2.