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Piperazine is an ideal desulfurizing agent but the heat-stable salts formed in desulfurization have caused secondary pollution and waste of resources. In the previous paper, a method was reported to regenerate piperazine by using BMED. To find the variety of that regeneration process, we performed experiments on the regeneration of piperazine by using ED. In comparison, ED has higher piperazine yield and current efficiency, and much lower voltage drop and energy consumption. However, its process cost is higher than that of BMED due to an extra expenditure for the base and its tank and pumps. The process cost is estimated to be 0.96 $/kg Pz for BMED and 1.14 $/kg Pz for ED. Notably, BMED has more environmental benefits and will be more economically attractive as the control on secondary pollution is strengthened and the bipolar membrane cost decreases. [ABSTRACT FROM AUTHOR]

A moderate temperature dry desulfurization process at 600–800 °C was studied in a pilot-scale circulating fluidized bed flue gas desulfurization (CFB-FGD) experimental facility. The desulfurization efficiency was investigated for various operating parameters, such as bed temperature, CO2 concentration, and solids concentration. In addition, structural improvements in key parts of the CFB-FGD system, i.e., the cyclone separator and the distributor, were made to improve the desulfurization efficiency and flow resistance. The experimental results show that the desulfurization efficiency increased rapidly with increasing temperature above 600 °C due to enhanced gas diffusion and the shift of the equilibrium for the carbonate reaction. The sorbent sulfated gradually after quick carbonation of the sorbent with a long particle residence time necessary to realize a high desulfurization ratio. A reduced solids concentration in the bed reduced the particle residence time and the desulfurization efficiency. A single-stage cyclone separator produced no improvement in the desulfurization efficiency compared with a two-stage cyclone separator. Compared with a wind cap distributor, a large hole distributor reduced the flow resistance which reduced the desulfurization efficiency due to the reduced bed pressure drop and worsened bed fluidization. The desulfurization efficiency can be improved by increasing the collection efficiency of fine particles to prolong their residence time and by improving the solids concentration distribution to increase the gas-solid contact surface area. [ABSTRACT FROM AUTHOR]

To develop a new process for removing high-concentration SO2 from industrial flue gases, the carbothermal reduction of SO2 by oil-sand fluid coke at 700 °C was investigated by varying the inlet concentration of either O2 or H2O. Concentrations of O2 and H2O ranged from 0 to 20% and from 0 to 30%, respectively, in a stream of SO2 (18%) with the balance helium. Addition of O2 and H2O was found to enhance SO2 reduction. The enhancement was attributed to the reducing gases, CO and H2, produced by solid–gas reactions between carbon and O2 or H2O. The effects of O2 and H2O on sulfur yield, however, were bifacial: adding O2 and/or H2O increased the sulfur yield when SO2 conversion was incomplete, otherwise, it decreased the sulfur yield through the formation of sulfides such as H2S. The results of a thermodynamic analysis were in a good agreement with the experimental results, suggesting that gas –solid reactions were slow enough to allow gas-phase equilibrium. This study indicates that carbon, such as oil-sand fluid coke, can be utilized to remove SO2 in flue gases containing O2/H2O and to convert it to elemental sulfur. [ABSTRACT FROM AUTHOR]