With the objective of producing a full-scale tiny-oil ignition burner, identical to the burner used in an 800 MWe utility boiler, numerical simulations were performed using Fluent 6.3.26 to study the progress of ignit...With the objective of producing a full-scale tiny-oil ignition burner, identical to the burner used in an 800 MWe utility boiler, numerical simulations were performed using Fluent 6.3.26 to study the progress of ignition for four coal concentration settings covering sub- operation conditions prevailing during the experiments performed with the burner. The numerical simulations conformed to the experimental results, demonstrating the suitability of the model used in the calculations. Simula- tions for a coal concentration of 0.40 kg/kg corresponding to a single burner operating at its rated output were also conducted, which indicated that gas temperatures along the burner centerline were high. As gas flowed to the burner nozzle, the high-temperature region expanded, ensuring a successful pulverized-coal ignition. With increasing coal concentration （0.08-0.40 kg/kg）, the gas temperature along the burner centerline and at the first and second combustion chamber exits decreased at the equivalent radial points. At the center of the second combustion chamber exit, the O2 concentrations were almost depleted for the five coal concentrations, while the CO concentrations peaked.展开更多
The progression of ignition was numerically simulated with the aim of realizing a full-scale tiny-oil ignition burner that is identical to the burner used in an 800 MWe utility boiler. The numerical simulations were c...The progression of ignition was numerically simulated with the aim of realizing a full-scale tiny-oil ignition burner that is identical to the burner used in an 800 MWe utility boiler. The numerical simulations were conducted for four excess air ratios, 0.56, 0.75, 0.98 and 1.14 （corresponding to primary air velocities of 17, 23, 30 and 35 m/s, respectively）, which were chosen because they had been used previously in practical experiments. The numerical simulations agreed well with the experimental results, which demonstrate the suitability of the model used in the calculations. The gas temperatures were high along the center line of the burner for the four excess air ratios. The flame spread to the bumer wall and the high- temperature region was enlarged in the radial direction along the primary air flow direction. The O2 concentrations for the four excess air ratios were 0.5%, 1.1%, 0.9% and 3.0% at the exit of the second combustion chamber. The CO peak concentration was very high with values of 7.9%, 9.9%, 11.3% and 10.6% for the four excess air ratios at the exit of the second combustion chamber.展开更多
In order to achieve the target of reducing oil consumption to zero for pulverized coal(PC)boiler in power plant,the paper developed a novel coal pulverized ignition approach,called as Alternating-Current plasma(AC pla...In order to achieve the target of reducing oil consumption to zero for pulverized coal(PC)boiler in power plant,the paper developed a novel coal pulverized ignition approach,called as Alternating-Current plasma(AC plasma)ignition,with the advantages of excellent PC combustion behavior and longer electrode life-span.The scientific principle of how to generate the AC plasma arc was elaborated in detail.First,the experiments on life-span of electrodes inside AC plasma generator had been conducted,finding a workable way to extend its life-span beyond 530 hours.Second,a new AC plasma burner specifically designed for lean coal according to the principle of PC staged combustion had been illustrated with diagrams and then used to ignite the PC-air stream under four kinds of conditions with a varying AC plasma power from 150 kW to 300 kW,focusing on analyses of the influence of AC plasma power on combustion behaver,such as combustion temperature,carbon burnout rate as well as PC combustion regime.The following results showed that in the case of the power of the AC plasma was P=300 kW,a satisfied PC combustion process could achieved,with the average PC combustion temperature of about 940°C,combustion flame length of 6.3 m,and the total carbon burnout rate of up to 52.2%.In addition,about 80%of the nozzle outlet section was filled with bright flame,while 81%of the PC was in zone of the cylindrical flame regime.The PC combustion modes were changed repeatedly during the process of combustion,which went from homogeneous combustion mode at initial ignition stage to combined combustion mode and heterogeneous combustion mode at middle stage,finally to combined combustion mode at later stage.The research conclusion in this paper has proved that the AC plasma ignition approach is feasible and effective to ignite low-rank coal without the present of fuel oil.展开更多
基金sponsored by the Hi-Tech Research and Development Program of China （863 program） （Grant No. 2006AA05Z321） and supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China （Grant No. 51121004）.
文摘With the objective of producing a full-scale tiny-oil ignition burner, identical to the burner used in an 800 MWe utility boiler, numerical simulations were performed using Fluent 6.3.26 to study the progress of ignition for four coal concentration settings covering sub- operation conditions prevailing during the experiments performed with the burner. The numerical simulations conformed to the experimental results, demonstrating the suitability of the model used in the calculations. Simula- tions for a coal concentration of 0.40 kg/kg corresponding to a single burner operating at its rated output were also conducted, which indicated that gas temperatures along the burner centerline were high. As gas flowed to the burner nozzle, the high-temperature region expanded, ensuring a successful pulverized-coal ignition. With increasing coal concentration （0.08-0.40 kg/kg）, the gas temperature along the burner centerline and at the first and second combustion chamber exits decreased at the equivalent radial points. At the center of the second combustion chamber exit, the O2 concentrations were almost depleted for the five coal concentrations, while the CO concentrations peaked.
文摘The progression of ignition was numerically simulated with the aim of realizing a full-scale tiny-oil ignition burner that is identical to the burner used in an 800 MWe utility boiler. The numerical simulations were conducted for four excess air ratios, 0.56, 0.75, 0.98 and 1.14 （corresponding to primary air velocities of 17, 23, 30 and 35 m/s, respectively）, which were chosen because they had been used previously in practical experiments. The numerical simulations agreed well with the experimental results, which demonstrate the suitability of the model used in the calculations. The gas temperatures were high along the center line of the burner for the four excess air ratios. The flame spread to the bumer wall and the high- temperature region was enlarged in the radial direction along the primary air flow direction. The O2 concentrations for the four excess air ratios were 0.5%, 1.1%, 0.9% and 3.0% at the exit of the second combustion chamber. The CO peak concentration was very high with values of 7.9%, 9.9%, 11.3% and 10.6% for the four excess air ratios at the exit of the second combustion chamber.
基金supported by the national natural science foundation of china(Contract No.51806132)doctor start-up capital of Shanxi University(No.20174462)。
文摘In order to achieve the target of reducing oil consumption to zero for pulverized coal(PC)boiler in power plant,the paper developed a novel coal pulverized ignition approach,called as Alternating-Current plasma(AC plasma)ignition,with the advantages of excellent PC combustion behavior and longer electrode life-span.The scientific principle of how to generate the AC plasma arc was elaborated in detail.First,the experiments on life-span of electrodes inside AC plasma generator had been conducted,finding a workable way to extend its life-span beyond 530 hours.Second,a new AC plasma burner specifically designed for lean coal according to the principle of PC staged combustion had been illustrated with diagrams and then used to ignite the PC-air stream under four kinds of conditions with a varying AC plasma power from 150 kW to 300 kW,focusing on analyses of the influence of AC plasma power on combustion behaver,such as combustion temperature,carbon burnout rate as well as PC combustion regime.The following results showed that in the case of the power of the AC plasma was P=300 kW,a satisfied PC combustion process could achieved,with the average PC combustion temperature of about 940°C,combustion flame length of 6.3 m,and the total carbon burnout rate of up to 52.2%.In addition,about 80%of the nozzle outlet section was filled with bright flame,while 81%of the PC was in zone of the cylindrical flame regime.The PC combustion modes were changed repeatedly during the process of combustion,which went from homogeneous combustion mode at initial ignition stage to combined combustion mode and heterogeneous combustion mode at middle stage,finally to combined combustion mode at later stage.The research conclusion in this paper has proved that the AC plasma ignition approach is feasible and effective to ignite low-rank coal without the present of fuel oil.
