Effect Mechanism Of Low Concentration O₂ On Coal Char-H₂O Gasification Reaction

There are rich coal resources in our country,a large amount of coal used has been caused serious pollution to the ecological environment.Thus,realized green and clean utilizatio has become important part in my country's energy structure adjustment.However,carbon materials such as coal will develop towards graphitization direction in the late perion of pyrolysis or gasification,which causes the deterioration of the reactivity of coal char.Previous study has pointed that O₂would promotion of reactivity of char-H₂O gasification.However,there also needs to be further research for coal char gasification mechanism.There will be discussed that the effect of mechanism of low concentration O₂ on coal char-H₂O gasification reaction and verified the competition mechanism of coal char-H₂O/O₂ gasification in this paper.This paper will from three aspects that coal char-H₂O/O₂ gasification reactivity,reaction kinetics,physical and chemical structure to be analized.Zhundong coal char with fluzied/fixed bed expermental reaction systerm prepared.Then there will be stuidied char-H₂O gasification in different O₂concentrations,different H₂O concentrations and different temperature with mircro fluzied bed expermental systerm.The result show that temperature and O₂concentration have obviously influence for char-H₂O gasification reactivity,which is enhanced with expermental temperature and O₂ concentration increasing,however H₂O concentration has little impaction for char gasification.Under the expermntal conditions in this paper,the conclusion that the formation of CO and H₂ in gas production are promoted with the increase of O₂ concentration.It's also believed that the competition and promotion mechanism between H₂O and O₂ are simultaneous in the char-H₂O/O₂ gasification process.Based on the expermental data,selected shrinking core model?SCM?,random pore model?RPM?and iso-conversional method to study kinetics of char-H₂O gasification.The activation energy calculated using SCM and RPM is very similar to the results of the isoconversion method and prove the correction that choosing two types of models.Adoped that Langmuir-Hinshelwood?L-H?meichanism model to verify partially competitive active sites in coal char with H₂O/O₂ gasification,which corresponding to experimental results.Finally,preparation of gasification activated coke at different O₂ concentrations and different processes of conversion using a micro fluzied bed experimental system.Using N₂ adsorption,scanning electron microscope?SEM?,Raman spectroscopy and Fourier transform infrared spectroscopy?FTIR?to analysis pore,surface morphology,coke structure and oxygen-containing functional groups of activated coke.The result show that the orderly structure of coal char increases and the degree of graphitization increases with the process of conversion,which is smaller impact for pore structure of coal char.The addition of O₂ will inhibit the graphitization process of coal char,promote the development of coal char pores obviously,increase the specific surface area and pore volume,and promote the generation cyclic hydroxyl groups and free OH in coal char,and promote the oscillation fracture of C-C,C=C and C-O-C structure,which changes to the C=O structure of the conjugated and C=O structure of the carboxylic acid,which increasing the number of surface active sites of coal char.The influence mechanism of O₂ on char-H₂O gasification reaction is further explained from the analysis of physical and chemical structure.