煤快速热解过程中氧化钙对焦油裂解的影响

第24卷第2期煤炭转化Vol.24 No. 22001年4月COAL CONVERSIONApr.2001煤快速热解过程中氧化钙对焦油裂解的影响”贾永斌)黄戒介2) 程中虎3王洋4>商要为降低煤在热解、气化过程中的焦油产量,在一快速热解固定床反应器中考察了氧化钙催化剂的加入对焦油裂解反应的影响,研究结果表明:在相同反应条件下，所选三种氧化钙催化剂中以CaO-3的焦油裂解活性为最大,它们的焦油裂解活性顺序为:CaO-3>CaO-2>CaO-1.并进-步考察了CaO-3在不同反应温度下对焦油裂解反应的影响.关键词焦油裂解,氧化钙,快速热解，固定床中图分类号TQ530. 2些低沸点纯组分的裂解研究表明:氧化钙对芳香烃0引言裂解的影响较大，而对脂肪烃的影响较小:甲基物均发生脱甲基反应,氧化钙促进了脱甲基析碳和环状煤在我国能源结构中占有绝对优势,其中低阶结构的破裂.有的学者认为碱土金属的氧化物能激煤占煤总储量的42%以上.低阶煤通常含有30%~发活化位的产生.[6.7]本研究将在固定床快速热解条40%的挥发分,适宜于通过热解气化制取较高热值件下考察三种不同来源的氧化钙对焦油的裂解活的气体,但在热解气化过程中会有少量的焦油产生，性,并对较优的催化剂作进-步较详细的考察.焦油的产生一方面会引起管道堵塞,影响操作系统的正常运行;另一方面在许多的工业应用中要求得1实验部分到洁净的煤气,例如在IGCC中要求得到热的和洁净的煤气,而焦油的产生增加了粗煤气的净化难度,1.1实验物料欧盟正致力于这一方面的研究.所以,如何能使焦油在热解气化过程中尽可能得到完全的裂解，使产生以彬县煤为原料,煤样粒径为0.180 mm~的气体不含焦油，对于洁净高效利用低阶煤具有重.0.700mm,-次反应煤样及所加催化剂分别为5g要的意义.和1 g,催化剂与煤样机械混合,原煤煤质分析见表关于氧化钙对于焦油裂解的活性,人们作了较1,所选催化剂组成见第54页表2.其中CaO-1是化多的研究,Frankin等口发现含钙的矿物质可以降低表1原煤工业分析和元素分析Table 1 The Proximate and ultimate analysis焦油的产量.Yoon等0]的实验表明石灰石可以增强of coal used焦油的裂解程度和速度,提高煤气中的氢气、甲烷以Proximate analysis/% " .adUltimate analysis/%* ,ad及二碳烃的含量. ChiuKin-53的研究表明氧化钙可MAvCHN以通过催化酮-烯醇异构化反应而促进酚类的裂解.5.7110.58 23. 5!67.48 3.97 10.86 1.04 0.36Khan[41的研究也表明:氧化钙的添加有利于焦油Percent of weight.(尤其是酚类化合物)的裂解.Eling[']在对焦油中某54煤炭转化2001年学分析纯氧化钙,CaO-2是由碳酸钙在900 C下煅加入无水硫酸钠,轻轻摇动至不结块为止,加盖,放烧得到的,CaO- 3是由氢氧化钙在700 C下煅烧得置约30min后,用预先以石油醚洗涤过的滤纸过到的.滤,收集滤液经65 C烘干,置于恒重的200mL烧表2所选催化剂的组成杯中，用石油醚洗涤锥形瓶、硫酸钠和滤纸,洗液并Table 2The composition of catalysts used”入烧杯中,将烧杯置于65 C水浴上蒸发至近干,然Ca(OH)2>99. 0%Ca0>99. 0%CaCO3>98. 0%后将烧杯外壁水珠擦干,置于烘箱中,在65 C下烘HCI- nonsoluble Ammonia precipitate HCI nonsoluble干1h,放入干燥器内冷却30min后称重.materials 0.01%0.2%materials 0. 05%1.3.2 气体分析Sulfate 0. 01%Alkaline metal and实验采用2305色谱仪分析二氧化碳,用2307Mg 0. 5%色谱仪分析其它常规气体.Na 0.2% .Sulfate 0.1%Sulfate 0.2%Acetic acidAmmonium hydroxideMg 0.05%; Nonsoluble materialsprecipitate 0. 25%2结果与讨论0. 05%K 0.01%Chloride 0. 5%￥Percen of weigh.2.1不同氧化钙催化剂对焦油裂解影响的考察1.2实验装置为了对不同来源的氧化钙催化剂的催化性能进实验在一固定床快速热解反应器中进行,系统行比较,分别在700 C和800 C反应条件下考察了压力为常压,实验装置见图1.它们对焦油裂解情况的影响.实验结果分别见表3和表4.|4表3700C时催化剂对焦油和气体产量的影响Table 3 Effects of catalysts on tar and gas yields (700 C)NKindsof Tar yield/Gas yields/10- 3/molcatalystcoH2CH49No catalyst2.7412.013.449. 457. 79AM 2], 8CaO-1 .2.345.364.4612.60 9.01CaO-21.964.01 5.7713.69 8. 31CaO-31.683.674.0414. 609.24，图1实验装置表4800C时催化剂对焦油和气体产量的影响Fig. 1 Experimental apparatusTable 4 Effects of catalysts on tar and gas yields (800 C )Reactor: 2Electric furnace; SPush rod;Kinds of Tar yield/Gas yields/10- /molHeating control apparatus; 5, 6. 7Tar trap;CO2H: Gas collector; 9-- Pressure meterNo catalyst 2. 2112.707.4520.2010.36首先设定反应温度,然后开始升温,同时通入氮1.9911.36 :11.89 24. 81.13. 771.61 .10.3411.26 27. 6713.24气,氮气流量为390mL/min;当氮气通入时间超过1.419. 6910.06 30. 1813.1330 min且达到设定温度后,快速推入样品到反应区，同时开始排水取气,热解煤气经石油醚吸收后进由表3和表4也可看出,在三种氧化钙催化剂入集气瓶中;当反应约8 min~10 min后,停止实中，催化活性的大小顺序为:CaO- 1CaO 2≈Al2O:>CaO-1≈Fe2O,其中氧化钙催化剂的物理性质极大地影响着它们的催化作用.2 6-(2)700C时在原煤中加入CaO催化剂后,从CaO-1到CaO-3,气体中的CO2含量逐渐减少,而H2含量逐渐增加,800C时这种现象不很明显.(3)相对原煤热解而言，加入CaO-3后,焦油产0550600650700750800率下降35%~40%,且焦油产率最大值所处的温度由650C下降到600C.图5不同温度下 CaO-3对CO产率的影响(4)相对原煤而言,加入CaO-3后，气体中的Fig.5 Effect of CaO-3 on CO yield at differentCO2含量明显降低,而CO,H2和CH。的含量则明显增加.第2期贾永斌等煤快速热解过程中氧化钙对焦油裂解的影响参考文献[1] FranklinH D, Peters W A. 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Energy and Fuels, 1988,2:405EFFECT OF CaO ON TAR CRACKING IN A RAPID-PYROLYSISFIXED BED REACTOR .Jia Yongbin Huang Jiejie Cheng Zhonghu and Wang Yang(Institute of Coal Chemistry, Chinese Academy of Sciences, 030001 Taiyuan)ABSTRACT The effect of CaO catalysts on tar cracking in a rapid- pyrolysis fixed bed reac-tor was studied in order to cut down the yield of tar in pyrolysis or gasification process. The re-sults show that minimum yield of tar was gained in the presence of CaO-3. The sequence ofcatalytic activities is:CaO- 3>CaO- 2>CaO-1. In the meantime, the effect of CaO-3 on tar crack- .ing reaction at different temperatures is also discussed.KEY WORDS tar cracking. CaO, rapid-pyrolysis, fixed bed reactor