基于粒径匹配复合剂的循环流化床锅炉脱硫试验

Experimental study on desulfurization with particlesize matched complex agent in CFB boiler

循环流化床锅炉采用炉内燃烧脱硫方式,受到脱硫剂石灰石煅烧特性、孔结构及氧化钙烧结的影响,通常难以实现环保超低排放要求,为解决循环流化床锅炉干法脱硫效率低的弊端,采用共沉淀法制备CeO_(2)-MnO_(2)-Fe_(2)O_(3)复合剂,以水玻璃或羧甲基纤维素钠为黏合剂进行黏合,并经高速混合机混合、旋转式颗粒机加工制粒以及球形抛丸机抛丸处理得到∅0.8~1.2 mm球状复合剂,该复合剂比表面积55~68 m^(2)/g,堆积密度1.80~2.10 g/cm^(3),抗压强度2.8~3.1 MPa。该复合剂与原煤、石灰石在循环流化床锅炉中进行燃烧深度脱硫中试试验,结果表明,添加CeO_(2)-MnO_(2)-Fe_(2)O_(3)复合剂后,烟气中SO_(2)浓度比传统使用石灰石脱硫剂时明显降低,钙硫比均为2.5工况下燃烧温度850、880、920℃时,烟气中SO_(2)浓度比原煤+石灰石工况分别减少22.1%、22.8%、19.0%,说明CeO_(2)-MnO_(2)-Fe_(2)O_(3)复合剂对循环流化床锅炉燃烧脱硫具有明显的催化促进作用。但受CaSO_(3)逆向分解、催化剂CeO_(2)比表面积下降以及脱硫产物CaSO_(4)堵塞孔隙等因素影响,脱硫效率在920℃时先增加后下降。添加复合剂CeO_(2)-MnO_(2)-Fe_(2)O_(3)后,对烟气中NO_(x)浓度影响不大,燃烧后灰渣微观形貌为块状、不规则状,灰渣中含O、Ca、Si、Al、Fe、S、Na、Te等元素,与未添加复合剂时类似。另外,CeO_(2)-MnO_(2)-Fe_(2)O_(3)复合剂粒径与固硫剂石灰石粉粒径相匹配,在燃烧过程中可随烟气经旋风分离器进气固分离后又返回炉膛,利于循环流化床锅炉燃烧时循环使用。

The Circulating Fluidized Bed boiler(CFB)adopts combustion desulfurization in the furnace,which is affected by the influence of calcination characteristics of desulfurizer limestone,pore structure and sintering of calcium oxide,so it is difficult to meet the requirements of environmental protection and ultra-low emission.In order to improve the desulfurization efficiency in the combustion of CFB,The CeO_(2)-MnO_(2)-Fe_(2)O_(3) complex was prepared by co-precipitation method,sodium silicate or carboxy methyl cellulose sodium was used as binder.After mixing with high-speed mixer,granulating by rotary granulator and shot blasting by spherical shot blasting machine,the spherical composite with a diameter of 0.8-1.2 mm was obtained.The specific surface area,bulk density and compressive strength of CeO_(2)-MnO_(2)-Fe_(2)O_(3) complex were 55-68 m^(2)/g,1.80-2.10 g/cm^(3) and 2.8-3.1 MPa,respectively.The deep desulfurization tests which was mixed with CeO_(2)-MnO_(2)-Fe_(2)O_(3) complex,coal,and desulfurizer limestone were proceeded in the combustion of CFB boiler for improving desulfurization efficiency by catalytic oxidation principle.The experimental results show that the concentration of SO_(2) in the flue gas is decreased obviously which are compared with the limestone desulfurizer mode after adding CeO_(2)-MnO_(2)-Fe_(2)O_(3) composite.The concentration of SO_(2) is decreased by 22.1%、22.8%and 19.0%in the combusting temperatures of 850,880,920℃and calcium sulfur ratio of 2.5,respectively compared with the coal and limestone desulfurization conditions,which shows CeO_(2)-MnO_(2)-Fe_(2)O_(3) complex has the obvious catalytic effect on the combustion of CFB boiler.The desulfurization efficiency is first increased and then decreased in 920℃because of the inverse decomposition of CaSO_(3),the decrease of specific surface area of CeO_(2) and pore plugging of desulphurization CaSO_(4).The concentration of NO_(x) in the flue gas is little change after the addition of CeO_(2)-MnO_(2)-Fe_(2)O_(3).The micro morphology of the combustion ash is massive and irregular,and the ash contains O,Ca,Si,Al,Fe,S,Na,Te and other elements,which is similar to that without composite agent.In addition,the particle size of CeO_(2)-MnO_(2)-Fe_(2)O_(3) composite agent is matched with that of limestone powder of sulfur fixing agent.During the combustion process,the CeO_(2)-MnO_(2)-Fe_(2)O_(3) complex can back to furnace after gas solid separating by cyclone separator.It is good for recycling of CeO_(2)-MnO_(2)-Fe_(2)O_(3) complex during CFB combustion.