煤快速熱解過(guò)程中氧化鈣對焦油裂解的影響

第24卷第2期煤炭轉化Vol.24 No. 22001年4月COAL CONVERSIONApr.2001煤快速熱解過(guò)程中氧化鈣對焦油裂解的影響”賈永斌)黃戒介2) 程中虎3王洋4>商要為降低煤在熱解、氣化過(guò)程中的焦油產(chǎn)量,在一快速熱解固定床反應器中考察了氧化鈣催化劑的加入對焦油裂解反應的影響,研究結果表明:在相同反應條件下，所選三種氧化鈣催化劑中以CaO-3的焦油裂解活性為最大,它們的焦油裂解活性順序為:CaO-3>CaO-2>CaO-1.并進(jìn)-步考察了CaO-3在不同反應溫度下對焦油裂解反應的影響.關(guān)鍵詞焦油裂解,氧化鈣,快速熱解，固定床中圖分類(lèi)號TQ530. 2些低沸點(diǎn)純組分的裂解研究表明:氧化鈣對芳香烴0引言裂解的影響較大，而對脂肪烴的影響較小:甲基物均發(fā)生脫甲基反應,氧化鈣促進(jìn)了脫甲基析碳和環(huán)狀煤在我國能源結構中占有絕對優(yōu)勢,其中低階結構的破裂.有的學(xué)者認為堿土金屬的氧化物能激煤占煤總儲量的42%以上.低階煤通常含有30%~發(fā)活化位的產(chǎn)生.[6.7]本研究將在固定床快速熱解條40%的揮發(fā)分,適宜于通過(guò)熱解氣化制取較高熱值件下考察三種不同來(lái)源的氧化鈣對焦油的裂解活的氣體,但在熱解氣化過(guò)程中會(huì )有少量的焦油產(chǎn)生，性,并對較優(yōu)的催化劑作進(jìn)-步較詳細的考察.焦油的產(chǎn)生一方面會(huì )引起管道堵塞,影響操作系統的正常運行;另一方面在許多的工業(yè)應用中要求得1實(shí)驗部分到潔凈的煤氣,例如在IGCC中要求得到熱的和潔凈的煤氣,而焦油的產(chǎn)生增加了粗煤氣的凈化難度,1.1實(shí)驗物料歐盟正致力于這一方面的研究.所以,如何能使焦油在熱解氣化過(guò)程中盡可能得到完全的裂解，使產(chǎn)生以彬縣煤為原料,煤樣粒徑為0.180 mm~的氣體不含焦油，對于潔凈高效利用低階煤具有重.0.700mm,-次反應煤樣及所加催化劑分別為5g要的意義.和1 g,催化劑與煤樣機械混合,原煤煤質(zhì)分析見(jiàn)表關(guān)于氧化鈣對于焦油裂解的活性,人們作了較1,所選催化劑組成見(jiàn)第54頁(yè)表2.其中CaO-1是化多的研究,Frankin等口發(fā)現含鈣的礦物質(zhì)可以降低表1原煤工業(yè)分析和元素分析Table 1 The Proximate and ultimate analysis焦油的產(chǎn)量.Yoon等0]的實(shí)驗表明石灰石可以增強of coal used焦油的裂解程度和速度,提高煤氣中的氫氣、甲烷以Proximate analysis/% " .adUltimate analysis/%* ,ad及二碳烴的含量. ChiuKin-53的研究表明氧化鈣可MAvCHN以通過(guò)催化酮-烯醇異構化反應而促進(jìn)酚類(lèi)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:氧化鈣的添加有利于焦油Percent of weight.(尤其是酚類(lèi)化合物)的裂解.Eling[']在對焦油中某54煤炭轉化2001年學(xué)分析純氧化鈣,CaO-2是由碳酸鈣在900 C下煅加入無(wú)水硫酸鈉,輕輕搖動(dòng)至不結塊為止,加蓋,放燒得到的,CaO- 3是由氫氧化鈣在700 C下煅燒得置約30min后,用預先以石油醚洗滌過(guò)的濾紙過(guò)到的.濾,收集濾液經(jīng)65 C烘干,置于恒重的200mL燒表2所選催化劑的組成杯中，用石油醚洗滌錐形瓶、硫酸鈉和濾紙,洗液并Table 2The composition of catalysts used”入燒杯中,將燒杯置于65 C水浴上蒸發(fā)至近干,然Ca(OH)2>99. 0%Ca0>99. 0%CaCO3>98. 0%后將燒杯外壁水珠擦干,置于烘箱中,在65 C下烘HCI- nonsoluble Ammonia precipitate HCI nonsoluble干1h,放入干燥器內冷卻30min后稱(chēng)重.materials 0.01%0.2%materials 0. 05%1.3.2 氣體分析Sulfate 0. 01%Alkaline metal and實(shí)驗采用2305色譜儀分析二氧化碳,用2307Mg 0. 5%色譜儀分析其它常規氣體.Na 0.2% .Sulfate 0.1%Sulfate 0.2%Acetic acidAmmonium hydroxideMg 0.05%; Nonsoluble materialsprecipitate 0. 25%2結果與討論0. 05%K 0.01%Chloride 0. 5%￥Percen of weigh.2.1不同氧化鈣催化劑對焦油裂解影響的考察1.2實(shí)驗裝置為了對不同來(lái)源的氧化鈣催化劑的催化性能進(jìn)實(shí)驗在一固定床快速熱解反應器中進(jìn)行,系統行比較,分別在700 C和800 C反應條件下考察了壓力為常壓,實(shí)驗裝置見(jiàn)圖1.它們對焦油裂解情況的影響.實(shí)驗結果分別見(jiàn)表3和表4.|4表3700C時(shí)催化劑對焦油和氣體產(chǎn)量的影響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，圖1實(shí)驗裝置表4800C時(shí)催化劑對焦油和氣體產(chǎn)量的影響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首先設定反應溫度,然后開(kāi)始升溫,同時(shí)通入氮1.9911.36 :11.89 24. 81.13. 771.61 .10.3411.26 27. 6713.24氣,氮氣流量為390mL/min;當氮氣通入時(shí)間超過(guò)1.419. 6910.06 30. 1813.1330 min且達到設定溫度后,快速推入樣品到反應區，同時(shí)開(kāi)始排水取氣,熱解煤氣經(jīng)石油醚吸收后進(jìn)由表3和表4也可看出,在三種氧化鈣催化劑入集氣瓶中;當反應約8 min~10 min后,停止實(shí)中，催化活性的大小順序為:CaO- 1CaO 2≈Al2O:>CaO-1≈Fe2O,其中氧化鈣催化劑的物理性質(zhì)極大地影響著(zhù)它們的催化作用.2 6-(2)700C時(shí)在原煤中加入CaO催化劑后,從CaO-1到CaO-3,氣體中的CO2含量逐漸減少,而H2含量逐漸增加,800C時(shí)這種現象不很明顯.(3)相對原煤熱解而言，加入CaO-3后,焦油產(chǎn)0550600650700750800率下降35%~40%,且焦油產(chǎn)率最大值所處的溫度由650C下降到600C.圖5不同溫度下 CaO-3對CO產(chǎn)率的影響(4)相對原煤而言,加入CaO-3后，氣體中的Fig.5 Effect of CaO-3 on CO yield at differentCO2含量明顯降低,而CO,H2和CH。的含量則明顯增加.第2期賈永斌等煤快速熱解過(guò)程中氧化鈣對焦油裂解的影響參考文獻[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