| Coal gasification indexes are important for either ground gasification orunderground gasification. That’s because the most primary essential data can beobtained from Coal gasification indexes for the process design and engineering designof gasification and its follow-up processes.It is the first time to conduct the in-stiu coal pyrolysis experiment under warmpressure state which has a temprature of above600℃. An experimental method isestablished to simulate coal pyrolysis during the process of underground coalgasification. Then, the common law of pyrolysis coal gas production of Coal underwarm pressure state was obtained as list.1) Along with the increase of stress, gas production rate and semicoke (coke)production rate increase, but tar yield decreases.2) Along with the increase of stress, the content of CH4and CO2in pyrolysis gasincreases and that of H2and CO decreases.3) Both gas production rate, tar production rate and semicoke (coke) productionrate as well as the content of each gas under the stress change can be displayed onlywhen exceeding certain temperature.4) The content of C2H6involves peak temperature nearby800℃and sharplyreduces after exceeding this peak point. Before the peak point, the content of C2H6increases along with stress increase. After the peak point, that of C2H6decreases alongwith stress increase. The content of C2H4increases along with stress increase. Thecurve slowly grows between750℃and800℃. However, it increases rapidly after800℃. The content of C3H8decreases along with stress increase between600℃and1000℃.5) From the gas production rate, tar production rate and semicoke (coke)production rate caused by unit stress as well as the change value of each gas content,it can be concluded that the value of Coal which has higher volatile matter isrelatively higher than that of lower under each temperature.6) Under no-stress state, the main pyrolysis gas components including H2, CO,CH4and CO2tend to go steady at800℃or850℃. But hydro carbons including C2H6,C3H8and C2H4tend to go steady at900℃. The changing curve patterns of each gascomponent under various stress states are fundamentally similar with that underno-stress state. Yet, there are very remarkable changes in the contents of C2H6, C3H8and C2H4under various stress states when exceeding the high temperature of900℃, which shows the laws different from that under no-stress state.Based on the above, two-stage reaction equilibrium calculation method ofunderground coal gasification was established in this thesis. In addition, matlab wasemployed to compile the calculation procedures of air steam continuous method,oxygen-enriched continuous method and pure oxygen steam continuous method ofunderground gas gasification. Meanwhile, these calculation procedures were appliedto simulate the gas production process of field test..Computaion results have providedthe guidance for the design of field test. The matching degree of calculated results andactual field test data after stabilization is very high, which proves that the model andprocedures can make good simulation for underground coal gasification.The two-stage reaction equilibrium calculation method of underground coalgasification index of carbon dioxide remeltting was established to calculate theunderground coal gasification indexes with pure oxygen steam carbon dioxidecontinuous method and air steam carbon dioxide continuous method. Computaionresults suggest that carbon dioxide is a kind of gasification agent enabling to quicklyadjust gasifier temperature compared with water vapor and carbon dioxide partlyreplaces water vapor.In this thesis, two indexes of coal gasification index including comprehensivegasification efficiency and hot gas comprehensive gasification efficiency wereproposed as evaluation index of energy conversion efficiency in the process of coalgasification. Besides, relevant computing methods were given. In terms of pureoxygen steam carbon dioxide continuous method under living example, cold coal gasefficiency of underground coal gasification is higher than that of Texaco gasificationby6.48%, comprehensive gasification efficiency of underground coal gasification ishigher than that of Texaco gasification by10.56%, hot gas comprehensivegasification efficiency of underground coal gasification is higher than that of Texacogasification by11.28%. Under the premise of other fixed conditions, the ratio ofsteam(carbon dioxide) to oxygen in gasification agent directly determines the energyconversion efficiency of gasifier. There is optimal ratio of steam(carbon dioxide) tooxygen under various technological conditions. The calculation results indicate thatadding a certain amount of carbon dioxide is beneficial for improving comprehensivegasification efficiency and hot gas comprehensive gasification efficiency ofunderground coal gasification. However, adding a certain amount of pure oxygen isuseful for enhancing comprehensive gasification efficiency of underground coal gasification. However, it is irrelevant to reinforce hot gas comprehensive gasificationefficiency of underground coal gasification.There are115figures,56tables and210references. |
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