Oxy-combustion technology is under development for CO2 capture. H2O could influence the Hg0 removal by sorbent traps in an oxy-combustion atmosphere. A study of the effects of H2O on Hg0 removal by biomass char under oxy-combustion conditions is presented in this paper. The kinetic model analysis was conducted to study the adsorption process of Hg0, which included a pseudo-first-order kinetic model, a pseudo-second-order kinetic model, and intraparticle diffusion kinetic model. Experimental results showed that a low-level of H2O had a promoting effect on the adsorption of Hg0, and high-level of H2O had an inhibiting effect. A high concentration of H2O would form a water film on the surface of sorbent traps to hinder the removal of external mass transfer on Hg0. Although the adsorption rate of Hg0 depended both on external mass transfer and intraparticle diffusion, external mass transfer was a more important controlling factor. It was found that physical adsorption was one of the main forms of Hg0 removal on the surface of sorbent traps, owing to the large specific surface area and good pore structure of the modified corn straw char. The removal of Hg0 was mainly attributed to capture by physical adsorption and the formation of HgO by chemisorption.

The H 2 O concentration in an oxyfuel-combustion atmosphere is higher than that in a traditional combustion atmosphere, which will affect the mercury removal process. Therefore, it is necessary to carry out a research on the interference effect of H 2 O on mercury removal under an oxyfuelcombustion atmosphere. In this paper, corn straw char was modified by NH 4 Cl, and related experiments were carried out using a fixed-bed reaction system. The characterization results of the sorbent showed that the modification enhanced its physical and chemical adsorption capacities. The addition of H 2 O in a NO atmosphere was not conducive to mercury removal but could alleviate the toxicity of SO 2 on the adsorbent in a SO 2 atmosphere. The coexistence of H 2 O and NO significantly inhibited the mercury removal, but some nitrate ions were generated during the process, which slightly weakened the negative effects of H 2 O. The coexistence of low-concentration H 2 O and SO 2 would weaken the poisoning effect of SO 2 on the mercury sorbent, and high-content H 2 O would react to generate excess H 2 SO 4 to block the surface pores. SO 3 could assist Hg 0 oxidation, while H 2 O would hinder the transformation of SO 2 into SO 3 . In a HCl atmosphere, highconcentration H 2 O (20%) inhibited mercury removal, while lower-concentration H 2 O (5−15%) showed an opposite behavior. The low concentration of H 2 O did not affect the oxidation of Hg 0 by HCl, and it was accompanied by the formation of substances conducive to mercury removal. The increase of the H 2 O concentration would hinder the oxidation reaction of HCl and Hg 0 .

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It is necessary to find a better method to remove mercury from coal-fired flue gas. This work proposes the use of corn stalk coke to remove mercury from coal-fired flue gas and through elemental sulfur (CSC-S), water vapor activation (CSC-H 2 O), and sulfur modification combined with water vapor activation (CSC-H 2 O-S) to prepare three different adsorbents. The mercury removal performance of the adsorbents prepared by different methods was evaluated on a small fixed-bed mercury removal experimental platform. The experimental results showed that the order of mercury removal efficiency of the four adsorbents was: CSC-H 2 O-S > CSC-S > CSC-H 2 O > CSC. Brunauer−Emmett−Teller (BET), Fourier transform infrared (FTIR) spectroscopy, and Xray photoelectron spectroscopy (XPS) were adopted to study the physical and chemical properties of the adsorbent surface and the mechanism of mercury removal. The results showed that water vapor activation can improve the pore structure of the adsorbent, increase its specific surface area, and generate new oxygen-containing functional groups on the surface of the adsorbent. The adsorption kinetic model further demonstrated that the water vapor activation process can improve the physical adsorption performance of corn stalk char, and the sulfur modification process can improve the chemical adsorption performance of corn stalk char. Quantum chemical studies have shown that the surface structure doped with S and O atoms is conducive to enhancing the adsorption of Hg 0 .

The development of effective sorbents using biomass is important to achieve mercury removal in coal combustion flue gas. In this work, a biomass sorbent was prepared by using rice husk as a raw material and CuCl2 solution as a modifier. The experiment explored the mercury removal ability of rice husk with different modification solution concentrations. The sorbent showed the best mercury removal capacity with 0.15 mol/L CuCl2 solution modified rice husk coke at an inlet mercury concentration of 54.4 μg/m3 at 150 °C. It was found that the modification made CuCl2 adhere to the surface of the coke sample successfully and chlorine-containing functional groups and copper-containing functional groups in the coke sample both promoted the adsorption of mercury. The increase in chemisorbed oxygen due to the modification also promoted the sorbent removal of mercury. The increase of adsorption temperature and inlet mercury concentration was beneficial to mercury removal, but too high temperature had a negative effect on its mercury removal. The purpose of this work is to explore a novel approach for the efficient use of this agricultural waste, apply it to mercury removal in oxyfuel coal-fired power plants, and provide technical support and theoretical guidance for its application in industry.