Gas distribution between main gas inlet and three auxiliary inlets at 0.25 m, 0.5 m and 0.75 m was also simulated to study
possible improvement in heat recovery. Making use of results of previous sections, gas distribution ratios between the four inlets were varied in the range of 1:1:1:7 to 1:1:7:1. Results are shown in Fig. 6 and it is evident that the optimum gas distribution ratio is 1:1:1:7. Maximum solid temperature obtained with optimum four gas inlet system is 2 °C greater than that achieved with three gas inlet system. For a gas to solid mass flow ratio of 5, the optimum gas distribution ratio is found to be 1:1:0.5:2.5, which gives a solid temperature at 1 m, around 1 °C greater than that achieved with three inlet system, as evident from Fig. 7. Changes in gas distribution affect the final solid temperature very little for a gas to solid mass flow ratio of 5, since the various ratios simulated are not much different. Gas supply through the main gas inlet and the auxiliary inlet at 0.25 m were maintained same during the simulation based on the results of three-inlet scheme, while changing its flow through the auxiliary inlets at 0.50 m and at 0.75 m. Hence, the solid temperature profiles for different distribution schemes overlap till 0.5 m from the bottom and are same as that of the optimum threeinlet scheme; hence, temperature profiles till 0.5 m are not shown in Figs. 6 and 7. A comparison of solid temperature profiles at optimum gas distribution ratios for two, three and four inlet schemes for gas to solid mass flow ratio of 10 and 5 is shown in Fig. 8. It is clear from the above discussions that maximum solid temperature is achieved with four gas inlet system for both the gas to solid mass flow ratios. Hence, under the conditions simulated, four gas inlet scheme with lower gas supply at the inlets, preceding the final inlet would lead to maximum solid temperature, was compared to two and three inlet schemes. All the above simulations were carried out for 2 mm particles as well and the results are qualitatively similar. To make the paper concise, results of those simulations are not presented.
Gas distribution between main gas inlet and three auxiliary inlets at 0.25 m, 0.5 m and 0.75 m was also simulated to study
possible improvement in heat recovery. Making use of results of previous sections, gas distribution ratios between the four inlets were varied in the range of 1:1:1:7 to 1:1:7:1. Results are shown in Fig. 6 and it is evident that the optimum gas distribution ratio is 1:1:1:7. Maximum solid temperature obtained with optimum four gas inlet system is 2 °C greater than that achieved with three gas inlet system. For a gas to solid mass flow ratio of 5, the optimum gas distribution ratio is found to be 1:1:0.5:2.5, which gives a solid temperature at 1 m, around 1 °C greater than that achieved with three inlet system, as evident from Fig. 7. Changes in gas distribution affect the final solid temperature very little for a gas to solid mass flow ratio of 5, since the various ratios simulated are not much different. Gas supply through the main gas inlet and the auxiliary inlet at 0.25 m were maintained same during the simulation based on the results of three-inlet scheme, while changing its flow through the auxiliary inlets at 0.50 m and at 0.75 m. Hence, the solid temperature profiles for different distribution schemes overlap till 0.5 m from the bottom and are same as that of the optimum threeinlet scheme; hence, temperature profiles till 0.5 m are not shown in Figs. 6 and 7. A comparison of solid temperature profiles at optimum gas distribution ratios for two, three and four inlet schemes for gas to solid mass flow ratio of 10 and 5 is shown in Fig. 8. It is clear from the above discussions that maximum solid temperature is achieved with four gas inlet system for both the gas to solid mass flow ratios. Hence, under the conditions simulated, four gas inlet scheme with lower gas supply at the inlets, preceding the final inlet would lead to maximum solid temperature, was compared to two and three inlet schemes. All the above simulations were carried out for 2 mm particles as well and the results are qualitatively similar. To make the paper concise, results of those simulations are not presented.
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