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Studies On Kinetics Of Coal Gasification For High Ash Fusion Temperature Coal

Posted on:2014-02-20Degree:MasterType:Thesis
Country:ChinaCandidate:S L HuFull Text:PDF
GTID:2231330392460679Subject:Thermal Engineering
Abstract/Summary:PDF Full Text Request
Large-scale entrained flow gasification is the core issue of the cleancoal technology. Research on the char gasification kinetics for the highfusion temperature coal can offer the basic experimental data for the designof new non-slagging gasification While, related study of char characteristicwith elevated temperature and pressure is lack. In this dissertation, severaltypical high ash fusion temperature coal were investigated on theTGA/PTGA in order to analysis the impact of coal rank, temperature,pressure, gas concentrations and ash melting characteristics for thegasification rate, expecting to get accurate gasification kinetic parameters.Using TGA,in the range of11001400℃the gasification reactionof char with CO2and H2O at elevated temperature were studied underisothermal conditions. The conversion and rate curves show thegasification reactivity promotes with the increasing of temperature.Apparent activation energy appeared to decrease firstly and then increasein the gasification process, specially the apparent activation energy is onlyhalf of the initial reaction when conversion reaches90%, which is unlikethe traditional view of apparent activation energy unchanged at lowtemperature. The result of SEM display that the partial pore of char closedat high temperature, hindering the mass transfer process, the diffusionresistance is beginning to affect and control the reaction. Reactivity ofchar-H2O is about1.11.2times of char-CO2for high ash fusiontemperature coal. Based on the Random Pore Model, Thiele modulus wasintroduced to consider the pore diffusion to development the new kineticmodel to predict the gasification. Char-H2O reaction rates were measured in PTGA at0.12.0MPa withvariable H2O composition. The experimental results appear reaction rateincreases with temperature, when temperature above900℃,diffusionbegin to effect. Raising the vapor concentration under given total pressurewill contribute to the gasification process, but the vapor concentrationwithin the range of from15to50%, the reaction rate is trendnon-proportionally increase. The effect of total pressure is complicated.The system pressure makes the relative concentration rise, improve thecollision probability of water vapor with char and then encourage thereaction. On other hand, the total pressure will decrease the gasificationbecause of volume effect. On the basis of the random pore model, nthorderequation is used to quantitative to investigation impact of pressure, finallya rate equation of char-H2O for high ash fusion temperature coal isobtained.
Keywords/Search Tags:Coal gasification, High ash fusion coal, Kinetic
PDF Full Text Request
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