Methane-air diffusion filtration combustion in a radiative round-jet burner was numerically investigated in this work.The purpose of this study was focused on the effects of porous media porosity and gas velocity on t...Methane-air diffusion filtration combustion in a radiative round-jet burner was numerically investigated in this work.The purpose of this study was focused on the effects of porous media porosity and gas velocity on temperature distribution and CO and NO_(x)emissions.Reduced chemical kinetics was used where air and methane were assumed to be at their stoichiometric ratio,while thermo-physical properties were varied per the solid matrix porosity variation.Combustion characteristics were evaluated based on conduction and radiation as the two primary heat transfer modes within the solid matrix.Numerical simulations were carried out based on a packed bed with 3 mm alumina pellets.Results show that combustion temperature increases while the temperature gradient decreases with the increase in porosity,yielding higher NO_(x),and lower CO emissions.Furthermore,the combustion temperature is the lowest and most uniformly distributed with 1 m/s and 3 m/s gas velocities,wherewith 3 m/s gas velocity,combustion occurs outside of the porous zone.The corresponding NO_(x)and CO emissions are the lowest with 1 m/s gas velocity and increase with the increase in gas velocity from 1 m/s to 10m/s.展开更多
One of the most significant human-made methane emission sources is the MSW （municipal solid waste）, deposited on sanitary landfills and open dumps. Within this work, an alternative MSW treatment concept is presented...One of the most significant human-made methane emission sources is the MSW （municipal solid waste）, deposited on sanitary landfills and open dumps. Within this work, an alternative MSW treatment concept is presented, which could provide a relatively clean waste/biomass-to-energy transformation. The proposed procedure comprises of a combustion and a gasification （or pyrolysis） step, which are consecutively taking place in a two-stage hybrid porous reactor system. The core of the system is two packed bed reactors, in which solid fuel （waste or biomass） is mixed with inert ceramic particles of similar size. This paper overviews the initial experimental investigation of the combustion step of a hybrid mixture, composed of wood pellets （fuel） and alumina balls （inert ceramic particles） in a 250 ram-high batch reactor. The temperature profile along the reactor, the concentration of CO and the flame front propagation velocity were measured as a function of the ceramic particle size （11 and 20 mrn）, the inert-to-fuel mass ratio （0：1, 2：1, 3：1） and the airflow rate （30, 42, 60 1/min）. Experiments indicate that an increase of the mass ratio of inert-to-fuel material and a decrease of the inert ceramic particles size lead to a decrease of the maximum temperature of the packed hybrid bed. Measured CO concentrations showed strong dependence on the inert ceramic particle size, i.e. the particle size reduction from 20 to 11 mm resulted in a significant reduction of CO-emission peaks. The maximum flame front propagation velocity of 0.2 mm/sec was detected for the airflow of 42 1/min, the particle size of 20 mm and the mass ratio of 3：1.展开更多
文摘Methane-air diffusion filtration combustion in a radiative round-jet burner was numerically investigated in this work.The purpose of this study was focused on the effects of porous media porosity and gas velocity on temperature distribution and CO and NO_(x)emissions.Reduced chemical kinetics was used where air and methane were assumed to be at their stoichiometric ratio,while thermo-physical properties were varied per the solid matrix porosity variation.Combustion characteristics were evaluated based on conduction and radiation as the two primary heat transfer modes within the solid matrix.Numerical simulations were carried out based on a packed bed with 3 mm alumina pellets.Results show that combustion temperature increases while the temperature gradient decreases with the increase in porosity,yielding higher NO_(x),and lower CO emissions.Furthermore,the combustion temperature is the lowest and most uniformly distributed with 1 m/s and 3 m/s gas velocities,wherewith 3 m/s gas velocity,combustion occurs outside of the porous zone.The corresponding NO_(x)and CO emissions are the lowest with 1 m/s gas velocity and increase with the increase in gas velocity from 1 m/s to 10m/s.
文摘One of the most significant human-made methane emission sources is the MSW （municipal solid waste）, deposited on sanitary landfills and open dumps. Within this work, an alternative MSW treatment concept is presented, which could provide a relatively clean waste/biomass-to-energy transformation. The proposed procedure comprises of a combustion and a gasification （or pyrolysis） step, which are consecutively taking place in a two-stage hybrid porous reactor system. The core of the system is two packed bed reactors, in which solid fuel （waste or biomass） is mixed with inert ceramic particles of similar size. This paper overviews the initial experimental investigation of the combustion step of a hybrid mixture, composed of wood pellets （fuel） and alumina balls （inert ceramic particles） in a 250 ram-high batch reactor. The temperature profile along the reactor, the concentration of CO and the flame front propagation velocity were measured as a function of the ceramic particle size （11 and 20 mrn）, the inert-to-fuel mass ratio （0：1, 2：1, 3：1） and the airflow rate （30, 42, 60 1/min）. Experiments indicate that an increase of the mass ratio of inert-to-fuel material and a decrease of the inert ceramic particles size lead to a decrease of the maximum temperature of the packed hybrid bed. Measured CO concentrations showed strong dependence on the inert ceramic particle size, i.e. the particle size reduction from 20 to 11 mm resulted in a significant reduction of CO-emission peaks. The maximum flame front propagation velocity of 0.2 mm/sec was detected for the airflow of 42 1/min, the particle size of 20 mm and the mass ratio of 3：1.
