外文题名 Study on the high temperature coal gas cleaning-removal of NH3,organic sulfur,HCl,tar component and alkali metal compounds
Coal is a complex and heterogeneous substance containing several impurities, including sulfur, chlor, nitrogen and metal compounds. The integrated coal gasification combined cycle (IGCC) produces electricity with a higher efficiency by converting coal to coal gas that can drive two turbine systems. The coal gas can also be used for Molten Carbonate Fuel Cells (MCFC) . In this case, the coal gas must be treated to remove impurities such as particulate, H〓S, NH〓, organic sulfur, HCl, tar, alkali metal compounds and so on. The amounts of NH〓, organic sulfur, HCl, tar, alkali metal compounds, being present in coal-derived gas are generally small, compared to those of particulate and sulfur compounds, but their harmfulness to the above mentioned power generation systems is quite severe.
In this paper, the experiments were first carried out to separately remove NH〓, organic sulfur, HCl, coal tar component and alkali metal compounds in high temperature coal gas. The test results show Ni-3 catalyst is an effective catalyst for NH〓 at 550～750℃, with a conversion of 93％～94％, and has a long operation life and better anti-sulfur behavior. Two commercial sulfurized catalysts, Ni-3 and GS-100, were chosen to convert organic sulfur in high temperature coal gas into H〓S. It is observed that the conversions of CS〓 and COS is respectively 20％～40％ by GS-100 catalyst and 60％～85％ by Ni-3 catalyst. The CNl sorbent self-made has the highest chlorine capacity. The experimental data obtained from chlorine removal were analyzed by a model based on fixed-bed reactor and shrinking core models. It is found that reaction between sorbent and HCl vapor is of first-order with respect to initial HCl concentration. This reaction is governed by combination of the chemical reaction and product layer diffusion. The distribution of chlorine in the sorbent bed was determined. It is found that sorbent in the upstream end of the bed is nearly saturated with the chlorine whereas sorbent in the downstream end only contains less than 2wt％ of chlorine. The tar decomposition activities of eight catalysts including Fe based catalyst, three Ni based catalyst, 5A molecular sieve, CaO, alumina and quartz, were compared in a fixed-bed catalytic reactor, using a simulate high temperature coal gas. Ni-3 catalyst was found to be a quite effective catalyst for tar component (1-methylnaphthalene and benzene) conversion. Studies on the kinetics of tar component cracking and carbon combustion of catalysts were also carried out under certain conditions. A study on alkali metal vapor removal from high temperature coal gas was conducted for the purpose of reducing the corrosion of alkali metal vapor on gas turbine blades in IGCC process. NaCl was used as an alkali metal model compound, seven sorbents were screened by their effectiveness in capturing NaCl vapor at 840℃, test shows the second grade alumina; bauxite; kaoline; acidic white clay and activated Al〓O〓 present higher adsorption efficiency. They remove respectively 85. 3％, 92. 5％, 88. 0％, 92. 7％ and 98. 2％ of the NaCl vapor in a simulated high temperature coal gas. It is found that activated Al〓O〓 has the highest adsorption efficiency and sodium content among seven sorbents tested. In capturing time of 3h, the sodium content absorbed by activated Al〓O〓 is up to 6. 2mg/g. In addition, tests indicate the removal of NaCl with activated Al〓O〓 is a physical adsorption process.
The experiments were then designed to simultaneously remove NH〓, coal tar component (1-methylnaphthalene) , organic sulphur (CS〓) , and HCl in high temperature coal gas by using a fixed-bed reactor. The results show Ni-3 catalyst is an effective catalyst for NH〓 and tar component decomposition, Ni-3 catalyst sulphurized is also effective for CS〓 conversion, and CNl sorbent self-prepared displays the highest adsorption capacity for HCl vapor. The gained maximum removal efficiencies are 79％, 100％, 88％, 100％ respectively for NH〓, tar component, organic sulphur and HCl. Finally, a group of experiments were carried out to simultaneously remove alkali metal compound vapor and HCl. The results indicate that the bauxite, activated Al〓O〓 and special grade alumina removed respectively 79. 5％, 74. 5％ and 36. 2％ of the NaCl vapor, and the removal conversion of HCl vapor is up to 100％.