Abstract: In order to analyze the growth mechanism of product layer in SO₂ and NO_x removal by calcium-based sorbent, the single-crystal Ca(OH)₂(0001) surface was used to simulate the pore wall and external surface of the sorbent. The growth of product layer was analyzed under different reaction environments. The growth mechanism of product layer in SO₂ and NO_x simultaneous removal by calcium-based sorbent was proposed, combining crystal growth theory and discrepancy between SO₂ and NO_x single removal. SO₂ removal reaction firstly occurred in the local area of the single-crystal surface to result in expansion of surface and formation of convex structure. Subsequently, the reaction and expansion area gradually extended, which led to formation of the continuous dense product layer. Due to solubility and diffusion of NO₂ removal product in the water film, NO₂ reaction had an obvious etching effect on the sorbent surface. When SO₂ removal reaction coexisted with NO₂ removal reaction, the etching action of NO₂ removal reaction could inhibit formation of the continuous dense SO₂ removal product layer. Meanwhile, the presence of NO₂ removal product could change the growth habit of the SO₂ removal product. Therefore, the sorbent surface structure after simultaneously reacting with SO₂ and NO_x was loose.

Key words: calcium-based sorbent, SO₂ and NO_x removal, growth of product layer, coal fired pollutants

摘要： 为了分析钙基吸收剂硫氮协同脱除过程中产物层的生长机制,采用氢氧化钙单晶体表面(0001)模拟吸收剂孔隙的孔壁及外表面,针对脱硫、脱硝及硫氮协同脱除过程中产物层的生长规律进行了分析,结合晶体生长理论及脱硫和脱硝过程中产物层生长的差异,提出了硫氮协同脱除过程中产物层生长的机制。研究结果表明,脱硫反应首先发生在单晶表面局部区域,并使该区域膨胀形成颗粒状凸起结构;之后,随着反应区域不断扩大,表面膨胀趋于一致,从而形成连续致密产物层。由于脱硝产物易溶于水,且在液膜中扩散,因此脱硝反应对单晶表面表现出刻蚀作用。硫氮协同脱除过程中,脱硝反应的刻蚀作用抑制了脱硫连续致密产物层的形成,同时,液膜中脱硝产物的出现也改变了脱硫产物的生长习性,因此反应后产物层为疏松结构。

关键词: 钙基吸收剂, 同时脱硫脱硝, 产物层生长, 燃煤污染