Formation of arsenic−copper-containing particles and their sulfation decomposition mechanism in copper smelting flue gas

The heat recovery steam generator(HRSG)of copper smelting generates a large number of arsenic−coppercontaining particles,and the in-situ separation of arsenic and copper is of importance for cutting off environmental risk and realizing resource recovery.The formation of arsenic−copper-containing particles was simulated,the method of in-situ decomposition of arsenic−copper-containing particles by pyrite was proposed,and the decomposition mechanism was confirmed.It was found that particles with high arsenic content were formed in the simulated HRSG,and copper arsenate was liable for the high arsenic content.Pyrite promoted the sulfation of copper,leading to the in-situ decomposition of copper arsenate.In this process,gaseous arsenic was released,and thus the separation of arsenic and copper was realized.

Enhanced simultaneous absorption of NO_(x) and SO_(2) in oxidation-reduction-absorption process with a compounded system based on Na_(2)SO_(3)

Oxidation of sulfite and competitive absorption existed in Na_(2)SO_(3) solution for simultaneous removal of NO_(x) and SO_(2),inhibited the long-term high-efficiency when used for practical applications.A matching strategy was developed to solve these problems.Antioxidants combination was used to retard the oxidation of antioxidant and enhance inhibition of S(IV)(tetravalent sulfur)oxidation.Hydroquinone(HQ)and sodium thiosulfate(ST)showed a positive synergistic effect on inhibition of S(IV)oxidation.When SO_(2) concentration was 500 and 2000 ppmV,the addition of 0.1 wt.%HQ and 1 wt.%ST decreased the percentage of S(IV)oxidized by oxygen by over 30%and 40%,respectively.Alkali(Na_(2)CO_(3))alleviated the competitive absorption between NO_(x) and SO_(2).Moreover,Na_(2)CO_(3) exhibited an enhancement effect on the absorption of NO_(x) and SO_(2) when coupled with anti-oxidants.While the increase of oxygen pressure accelerated the oxidation of S(IV),the anti-oxidants can retard the oxidation.The measurement of pH suggested the removal efficiency of NO_(x) highly depended on SO_(3)^(2-) concentration rather than pH.The further investigation of the mechanism suggested the match effect was related to the interaction between ST and the intermediate product of HQ.The match strategy holds a potential for application of SO_(3)^(2-) to denitration.

Absorption characteristics of elemental mercury in mercury chloride solutions

Elemental mercury （Hg^0） in flue gases can be efficiently captured by mercury chloride （HgCl2） solution. However, the absorption behaviors and the influencing effects are still poorly understood. The mechanism of Hg^0 absorption by HgCl2 and the factors that control the removal were studied in this paper. It was found that when the mole ratio of Cl^- to HgCl2 is 10：1, the Hg^0 removal efficiency is the highest. Among the main mercury chloride species, HgCl3^- is the most efficient ion for Hg^0 removal in the HgCl2 absorption system when moderate concentrations of chloride ions exist. The Hg^0 absorption reactions in the aqueous phase were investigated computationaIIy using Moller-Plesset perturbation theory. The calculated Gibbs free energies and energy barriers are in excellent agreement with the results obtained from experiments. In the presence of SO3^2- and SO2, Hg^2＋ reduction occurred and Hg^0 removal efficiency decreased. The reduced Hg^0 removal can be controlled through increased chloride concentration to some degree. Low pH value in HgCla solution enhanced the Hg^0 removal efficiency, and the effect was more significant in dilute HgCl2 solutions. The presence of SO4^2- and NO3^- did not affect Hg^0 removal by HgCl2.