The inhibiting effect of AI（OH）3 and Mg（OH）2 dust on explosion of methane-air mixtures was investigated by means of explosion parameter tests in a 20-liter closed vessel. The influences of varying methane concentr...The inhibiting effect of AI（OH）3 and Mg（OH）2 dust on explosion of methane-air mixtures was investigated by means of explosion parameter tests in a 20-liter closed vessel. The influences of varying methane concentration and dust concentration on explosion parameters were characterized based on the experimental data to determine the maximum explosion pressure, maximum rate of pressure rise, lower explosion limits and upper explosion limits. The inhibiting mechanisms of these kinds of dust were analyzed as well. The investigations indicate that AI（OH）3 and Mg（OH）2 dust can be used as inhibitors to prevent meth- ane explosion, however, their inhibiting effects are less than those of inert gas such as N2 and CO2 in that their dust can weaken the methane explosion but cannot totally eliminate it. The tests show that all of the explosion parameters with dust additives are strongly dependent on methane/air ratio and dust concentration, and AI（OH）3 dust has better performance than Mg（OH）2 dust in inhibiting methane explosion. The average percentage decreases of maximum explosion pressure and maximum rate of pressure rise with AI（OH）3 dust are 11.08% and 66.15%, respectively. Experiments also showed that there is a special phe- nomenon when methane explosion is inhibited by AI（OH）3 and Mg（OH）2 dust, in which is that during the process of explosion the maximum explosion pressure value first decreases then increases as dust concentration increases. The best dust concentrations to inhibit the explosion are 250 g/m3 with methane/air ratio at 9.5%, and 200 g/m3 with methane/air ratio at 7%. It is suggested that water vapor produced by the thermal decomposition of metal hydroxides makes the particles of descending dust combine, resulting in a decrease of the real dust concentration in the vessel. Water vapor also is the major cause of another phenomenon that the LEL curve and the UEL curve never meet with the increase of gas concentration.展开更多
In order to identify potential wood substitutes for the production of energy by gasification, binary blends （wood/miscanthus, miscanthus/straw and wood/straw） and ternary blends （wood, miscanthus and organic residu...In order to identify potential wood substitutes for the production of energy by gasification, binary blends （wood/miscanthus, miscanthus/straw and wood/straw） and ternary blends （wood, miscanthus and organic residue） were systematic tested in a laboratory bubbling fluidized bed gasification system. The results of experiments were compared with results of wood gasification. Of the binary blends, wood and miscanthus exhibited great potential as a wood substitute in fluidized bed gasification in terms of process stability and product gas quality. Adding 10 wt. % of organic residues to form ternary blends further improved the product gas quality. Gasification of fuels blended with straw tended to agglomerate in the fluidized bed because of straw＇s low ash melting temperature. This can be counteracted by adding Ca（OH）2 to fuels. Nonetheless, fuels blended with straw with higher percentages of Ca（OH）2 need further study to establish the optimal additive ratio.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50704025)
文摘The inhibiting effect of AI（OH）3 and Mg（OH）2 dust on explosion of methane-air mixtures was investigated by means of explosion parameter tests in a 20-liter closed vessel. The influences of varying methane concentration and dust concentration on explosion parameters were characterized based on the experimental data to determine the maximum explosion pressure, maximum rate of pressure rise, lower explosion limits and upper explosion limits. The inhibiting mechanisms of these kinds of dust were analyzed as well. The investigations indicate that AI（OH）3 and Mg（OH）2 dust can be used as inhibitors to prevent meth- ane explosion, however, their inhibiting effects are less than those of inert gas such as N2 and CO2 in that their dust can weaken the methane explosion but cannot totally eliminate it. The tests show that all of the explosion parameters with dust additives are strongly dependent on methane/air ratio and dust concentration, and AI（OH）3 dust has better performance than Mg（OH）2 dust in inhibiting methane explosion. The average percentage decreases of maximum explosion pressure and maximum rate of pressure rise with AI（OH）3 dust are 11.08% and 66.15%, respectively. Experiments also showed that there is a special phe- nomenon when methane explosion is inhibited by AI（OH）3 and Mg（OH）2 dust, in which is that during the process of explosion the maximum explosion pressure value first decreases then increases as dust concentration increases. The best dust concentrations to inhibit the explosion are 250 g/m3 with methane/air ratio at 9.5%, and 200 g/m3 with methane/air ratio at 7%. It is suggested that water vapor produced by the thermal decomposition of metal hydroxides makes the particles of descending dust combine, resulting in a decrease of the real dust concentration in the vessel. Water vapor also is the major cause of another phenomenon that the LEL curve and the UEL curve never meet with the increase of gas concentration.
文摘In order to identify potential wood substitutes for the production of energy by gasification, binary blends （wood/miscanthus, miscanthus/straw and wood/straw） and ternary blends （wood, miscanthus and organic residue） were systematic tested in a laboratory bubbling fluidized bed gasification system. The results of experiments were compared with results of wood gasification. Of the binary blends, wood and miscanthus exhibited great potential as a wood substitute in fluidized bed gasification in terms of process stability and product gas quality. Adding 10 wt. % of organic residues to form ternary blends further improved the product gas quality. Gasification of fuels blended with straw tended to agglomerate in the fluidized bed because of straw＇s low ash melting temperature. This can be counteracted by adding Ca（OH）2 to fuels. Nonetheless, fuels blended with straw with higher percentages of Ca（OH）2 need further study to establish the optimal additive ratio.
