Effect Of Atmosphere On In-situ Desulfurization And Operation Optimization Of An Integrated Desulfurization System With A CFB

The in-situ SO2 capture of circulating fluidized bed is an economic desulfurization technology. And the wet flue gas desulfurization is widely used with high desulfurization efficiency. It is efficient to integrate the CFB in-situ desulfurization and wet flue gas desulfurization to decrease the SO2 emission for the CFB power plant. The background of this paper is the development of ultra-low emission technology for the SO2 in circulating fluidized bed boiler. Sponsored by the National Key Technologies R&D Program of China, the theoretical study, experimental research and operation optimization for the circulating fluidized bed in-situ desulfurization and integrated desulfurization system are carried out.The objective of this paper is to study the effect of furnace atmosphere on the desulfurization process and achieve the efficient operation for the integrated desulfurization system. The main work include the effects of atmosphere on the coal combustion and sulfur containing pollutants releasing characteristic, effects of atmosphere on the calcium sorbent and the optimization of integrated desulfurization system. All the studies could be divided into 6 parts, including ①coal combustion and sulfur-containing pollutants releasing characters under low oxygen concentration condition, ②desulfurization performance and reaction kinetics analysis of calcium sorbents under oxidizing condition,③calcium sorbents sulfation process under conditions alternating between oxidizing and reducing,⑤experimental research on the integrated desulfurization system,⑤modeling of integrated desulfurization system for the SO2 capture process,⑥operation strategy and optimization of integrated desulfurization system.The results of coal combustion and sulfur-containing pollutants evolution under furnace atmosphere show that when O2 concentration decline, the apparent activation energy decrease on account of the compensating effect.The evolution of sulfur-containing pollutants decreases when the O2 concentration drops from 21%to 5%. Under the O2/CO2 condition, the SO2 and H2S trend to converse to the COS.The desulfurization performances of sorbents under the furnace atmosphere illustrate the calcium conversions of 4 calcium sorbents under oxidizing condition are different. Since the pore size and surface morphology after calcination contribute to increase the calcium conversion of egg shells. The desulfurization of sorbents could be described with the kinetic parameter and the activation energies for chemical reaction and product layer diffusion. Under the conditions alternating between oxidizing and reducing, the chemical compositions of products change with the increasing cycle. Through the analysis of fractal and surface morphology, a reaction mechanism of products variation is proposed.For the optimization of integrated desulfurization system, the availability of integrated desulfurization system is verified through experimental research firstly. The results show that the efficiency of wet flue gas desulfurization in the integrated desulfurization is lower than in a cold experiment. Secondly, a model considers the consumptions of materials and energy is presented. And the optimization calculation method based on the emission regulation and techno-economic evaluation is proposed. The calculation method is realized by a computer code in Matlab software. Finally, the calculation method is applied in optimization of integrated desulfurization. The corrected sulfur content and operation economic parameters are the main factors on affecting the strategy of one boiler with one tower mode. The field test verified the availability of the calculation method. Under the two boilers with one tower mode, it is better to increase the CFB in-situ desulfurization to fulfill the more stringent emission standard and realize the economic operation.