Energy & Fuels, Vol.33, No.7, 6302-6312, 2019
Adsorption and Agglomeration Characteristics of Fly Ash Particles in Low Low-Temperature Flue Gas Treatment Systems
In China, low-low-temperature flue gas treatment systems (LLTSs) have been widely applied in power plants because of their high efficiency and low cost. However, the improper parameter design for this system has caused the insufficient adsorption of H2SO4 mist and the excessive agglomeration of particles, which eventually lead to corrosion and ash deposition problems. This paper tried to study the adsorption and agglomeration characteristics of ash particles to optimize the parameter design of LLTSs and solve the above problems. The results showed that the adsorption process could be divided into a rapid adsorption stage and a saturation stage. The high adsorption rate in the first stage resulted from the interaction of physical and chemical adsorption. The adsorption limit and the ultimate adsorption ratio of particles (D-P/S-p) were proposed as characterization parameters to evaluate the adsorption capacity. For example, the adsorption limit and D-p/S-p were 10.6 mg g(-1) and 94.3, respectively, for sample particles <68 mu m. Temperature is the crucial factor for the adsorption. When the temperature was decreased from 120 to 90 degrees C, the adsorption rate increased from 0.261 to 0.413 mg g(-1) min(-1) for particles <68 mu m and from 0.364 to 0.528 mg g(-1) min(-1) for particles >68-75 mu m. The particle size distribution had a greater impact on chemical adsorption than physical adsorption and could change the adsorption rate and limit considerably. The agglomeration of particles occurred in stages. In the initial stage, agglomeration mainly occurred among particles <= 75 mu m. Both the particle surface morphology and the agglomeration form can be categorized into four types. With increasing particle size, the agglomeration degree decreased significantly. The adsorption and agglomeration characteristics obtained by analyzing the element content and the combustion method of coal may help improve parameter selection and solve corrosion and ash deposition problems.