等速升温流态化下CaO/生物质焦的SO2/NO联合脱除特性

燃煤锅炉污染物超低排放标准对电厂脱硫和脱硝系统提出了更高的要求。CaO作为脱硫剂可以实现循环流化床锅炉烟气中SO₂的高效脱除,焦炭作为还原剂直接还原NO,同时CaO的存在对焦炭还原NO起催化作用,可以实现燃煤烟气中SO₂/NO的联合脱除。为了探究连续温度变化对CaO/生物质焦联合脱硫脱硝性能的影响,在钙循环捕集CO₂技术背景下,研究了等速升温流态化下CaO/生物质焦的SO₂/NO联合脱除特性。探究了烟气中O₂和CO₂对CaO/椰壳焦脱除SO₂/NO的影响。结果表明,O₂通过对椰壳焦表面碳原子的活化作用降低了异相还原NO温度,在300~950℃等速升温过程中CaO/椰壳焦的NO脱除效率逐渐增加,780℃以上能实现100%脱硝。O₂也提高了CaO/椰壳焦的脱硫效率。CO₂与CaO的碳酸化反应以及与椰壳焦的气化反应对同时脱除SO₂/NO有明显抑制作用。O₂和CO₂共同作用下,在500~800℃内CaO/椰壳焦的脱硝效率随温度升高而增加,脱硫效率先降低后升高。NO促进了CaO/椰壳焦脱除SO₂,而SO₂对脱硝有抑制作用。800℃时CaO/椰壳焦同时脱除SO₂和NO的效率分别为97.7%和93.9%。

Characteristics of simultaneous SO2/NO removal by CaO/bio-char under fluidization at constant heating rate

The desulfurization and denitrification systems face sever challenges due to the ultra-low emission rules of coal-fired boilers.CaO-based sorbents can effectively remove SO₂ from flue gas of circulating fluidized bed boilers.Char can be used as a reducing agent to reduce NO directly,and CaO plays a catalytic role in the reduction reaction of NO by char.which can realize the simultaneous SO₂ and NO removal in flue gas.Based on calcium looping technology for CO₂ capture,the simultaneous SO₂/NO removal performance of CaO/bio-char was investigated under fluidization at constant heating rate in this study to explain the effect of continuous temperature change on the simul?taneous SO₂ and NO removal by CaO/bio-char.The influences of O₂ and CO₂ in flue gas on the simultaneous SO₂/NO removal perform?ance of CaO/coconut shell char were discussed.The results indicate that O₂ can reduce the temperature of heterogeneous reduction of NO by activating carbon atoms on the surface of coconut shell char.The NO removal efficiency increases gradually with constant rate heating from 300℃to 950℃,reaching 100%at above 780℃.The SO₂ removal efficiency of CaO/coconut shell char is also promoted by O₂.The simultaneous SO₂/NO removal is inhibited by the carbonation reaction between CaO and CO₂ as well as CO₂ gasification of coconut shell char.In the presence of both O₂ and CO₂,the NO removal efficiency increases as temperature increases from 500℃to 800℃,while the SO₂ removal efficiency firstly decreases and then increases.SO₂ inhibits the NO removal of CaO/coconut shell char,while NO can pro?mote the SO₂ removal performance.The simultaneous SO₂and NO removal efficiencies of CaO/coconut shell char at 800℃are 97.7%and 94%,respectively.