第37卷第2期煤炭轉(zhuǎn)化 Vol.37 No.22014年4月 COAL CONVERSION Apr. 201煤與生物質(zhì)共氣化制甲烷實驗研究劉園春1)李克忠2)熊志建3張榮3畢繼誠甘中學(xué)5摘要以煙煤和高粱秸稈為研究對象,在小型加壓固定床反應(yīng)器上考察了壓力3.5Ma及溫度700℃條件下制焦方式、煤/生物質(zhì)混合比和氣固接觸時間對煤與生物質(zhì)共氣化制取富甲烷氣體過程中水蒸氣氣化反應(yīng)和甲烷化反應(yīng)的影響結(jié)果表明,對于水蒸氣氣化反應(yīng),煤焦和生物質(zhì)焦共氣化時不能觀察到明顯的協(xié)同作用;對于甲烷化反應(yīng),高粱秸稈焦的甲烷化反應(yīng)活性高于煤焦的甲烷化反應(yīng)活性,當(dāng)對高粱秸稈水洗后,高粱秸稈焦的甲烷化反應(yīng)活性降低至與煤焦的甲烷化反應(yīng)活性相當(dāng),分析表明,水洗后高粱秸稈焦堿金屬鉀的含量顯著降低,說明高粱秸稈焦中堿金屬鉀的存在是高粱秸稈焦甲烷化反應(yīng)活性較高的主要原因增加氣固接觸時間,有利于提高甲烷產(chǎn)率關(guān)鍵詞生物質(zhì),共氣化,甲烷化,堿金屬中圖分類號TQ546.2能耗,若利用堿金屬含量相對較高的生物質(zhì)與煤進0引言行共氣化,不僅可避免催化劑回收或降低催化劑回我國是一個富煤、貧油、少氣的國家,在一次能收成本,而且可為生物質(zhì)規(guī)模高效利用提供一條有源結(jié)構(gòu)中,煤炭約占70%,石油約占23%,而天然氣效途徑,具有較好的經(jīng)濟效益和環(huán)境效益國內(nèi)外學(xué)僅占2%近年來,我國天然氣消費量以近1%的速者對煤和生物質(zhì)共氣化進行了較多的研究,重點是度增長,預(yù)計2020年缺口將達到2000億m3,對外從煤和生物質(zhì)混合顆粒的流化特性3、反應(yīng)過程依存度也將達到50%,嚴重影響了我國的能源安的協(xié)同效應(yīng)5和共氣化的工藝條件優(yōu)化[012等方全,并將制約我國經(jīng)濟和社會的發(fā)展.同時,我國煤面進行較為系統(tǒng)的研究,主要是以合成氣為目標(biāo)產(chǎn)炭傳統(tǒng)利用模式以燃燒利用為主,存在能量利用率物,研究的溫度范圍在800℃~1000℃,壓力一般低和污染重等諸多問題.利用我國豐富的煤炭資源,小于0.6MPa,而以甲烷為目標(biāo)產(chǎn)物時,要求反應(yīng)在將煤轉(zhuǎn)化為天然氣,不僅可以填補傳統(tǒng)天然氣市場低溫(小于800℃)、高壓(大于3.0Mpa)及催化劑的供求缺口,更好地滿足城鎮(zhèn)化擴大的需求,而且可存在下進行,以甲烷為目標(biāo)產(chǎn)物的煤和生物質(zhì)共氣以較好地改善我國能源消費結(jié)構(gòu).煤制合成天然氣化研究未見文獻報道.本研究使用固定床反應(yīng)器,考過程主要有煤經(jīng)“氣化后再催化合成”的兩步法和煤察了在低溫高壓及不同操作條件下,生物質(zhì)中堿金“原位直接轉(zhuǎn)化”的一步法.兩步法的主要特點是先屬對水蒸氣氣化反應(yīng)和甲烷化反應(yīng)活性的影響,為流在高溫氣化爐中氣化得到H2和CO,然后在甲烷化化床共氣化反應(yīng)器的設(shè)計和操作提供理論依據(jù).反應(yīng)器中把H2和CO合成為甲烷,過程的計算熱1實驗部分效率約60%;煤催化氣化屬于“原位直接轉(zhuǎn)化”的一步法,主要特點是煤在較低溫度(650℃~750℃)和1.1原料較高壓力(3.0MPa~4.0MPa)下,通過催化劑的選用內(nèi)蒙古不連溝煙煤(YM)和山西太原郊區(qū)催化作用,將煤在氣化爐內(nèi)直接轉(zhuǎn)化為富含CH4的的高粱秸稈(GL)為原料,將煤和生物質(zhì)在壓力合成氣,此過程的計算熱效率比兩步法的計算熱效3.5MPa,溫度700℃的氮氣氣氛固定床內(nèi)熱解率約高10%.2煤催化氣化產(chǎn)業(yè)化的難點之一是催60min后得到不連溝煤焦(MJ)和高粱秸稈焦化劑的回收獲取較高的催化劑回收率需要較高的(GLJ),粉碎至60目~80目(180m~250m)備國際科技合作計劃資助項目(2011DFA60610)和煤轉(zhuǎn)化國家重點實驗室自主研究課題(2011BWZ002)1)碩生中國科學(xué)院山西煤炭化學(xué)研究所煤轉(zhuǎn)化國家重點實驗0301太原中國科學(xué)院大100049北京2助理研究員3)副研究員;4)研究員,中國科學(xué)院山西煤炭化學(xué)研究所煤轉(zhuǎn)化國家重點實驗室,030001太原;5)博士、教授新奧科技發(fā)展有限公司煤基低碳能源國家重點實驗室,65001河北廊坊收稿日期:2013-04-04;修回日期:2013-05-0670煤炭轉(zhuǎn)化2014年用,原料的工業(yè)分析和元素分析結(jié)果見表1表1原料的工業(yè)分析和元素分析(%1.2實驗裝置 Table Proximate and ultimate analysis of samples(%)P固定床反應(yīng)器由內(nèi)徑D20mm不銹鋼反應(yīng)管 Proximate analysis,ad Ultimate analysis,d Sample M V A CH NS制成,長度900mm,其中溫度均勻段250mm,采用y10.6526.2214.1967.424.0510.861.140.65三段電加熱;設(shè)計溫度800℃,設(shè)計壓力4MPa.固G7.2470.5512.44.85.3635.650.990.21定床反應(yīng)器裝置見圖1,去離子水和反應(yīng)氣體分別mj0.13.57.227.01.390.491.040.82glJ0.3811.8233.7662.721.150.910.800.53由雙柱塞泵和質(zhì)量流量計控制,經(jīng)過預(yù)熱器和氣化10%K2CO3MJ5.279.5426.8966.120.822.811.030.84器輸入反應(yīng)器系統(tǒng)水蒸氣和少量的焦油經(jīng)過氣液分 Mass fraction.離罐冷凝,氣相產(chǎn)物經(jīng)濕式流量計計量后收集分析. Hopper Fitter4① Fitter3①H Fitter Collect H. Liquid/gas Filter Wet gas meter separator Water pump5圖1固定床反應(yīng)器裝置 Fig. Schematic diagram of the fixed-bed reactor apparatus 1-Relief valve; 2-Globe valve; 3-Stop valve: 4-Check valve; 5-Needle valve; 6-Back pressure regulator1.3實驗步驟積分數(shù),%;m生物質(zhì)焦和m煤焦為每次實驗所用焦樣中取適量原料裝入反應(yīng)管中,氮氣置換充壓至C的質(zhì)量,g3.5mpa,開啟加熱爐,升溫至700℃時,開始通入2結(jié)果與討論水蒸氣(1g/min),進行水蒸氣氣化實驗,在反應(yīng)器2.1水蒸氣氣化實驗出口,每隔20min對產(chǎn)出的氣體進行計量取樣,每2.1.1外擴散的消除個條件實驗反應(yīng)3h,氣體產(chǎn)量通過濕式流量計計以不連溝煤焦和高粱秸稈焦為原料考察了不同量,氣體組成通過安捷倫氣相色譜7820A分析;甲水流量和碳轉(zhuǎn)化率的關(guān)系,結(jié)果見圖2.由圖2可烷化實驗進行時直接用氫氣和一氧化碳充壓,氫氣知,當(dāng)水流量大于1g/min,反應(yīng)3h后,煤焦和生物和一氧化碳的流量比為3:1,從升溫開始收集產(chǎn)物質(zhì)焦水蒸氣氣化的碳轉(zhuǎn)化率不再隨水流量的增加而氣體.根據(jù)產(chǎn)氣量和氣體組成可計算得到水蒸氣氣化實驗的碳轉(zhuǎn)化率1.4碳轉(zhuǎn)化率的計算方法 -H2: 150 mL/min, H,: 0.5 g/min 40.-N2: 300 mL/min.: g/min水蒸氣作氣化劑時碳轉(zhuǎn)化率的計算式為: -N2: 600 mL/min. H,: 2 g/min12×v(co2+pco+c MJx=22.4×(m生物質(zhì)焦m煤焦(1)20100120140160180式中:V為從氣化開始到某反應(yīng)時間t出口干基氣 Time/min體產(chǎn)物的總產(chǎn)量,Lco,o2和cH分別為CO,圖2消除外擴散的影響實驗CO2和CH4從氣化開始到某反應(yīng)時間t的平均體 Fig. 2 Elimination of external diffusion experiment第2期劉園春等煤與生物質(zhì)共氣化制甲烷實驗研究71變化,表明已消除外擴散的影響.13條件下非常穩(wěn)定,熱解過程幾乎沒有析出本實驗在2.1.2生物質(zhì)焦和煤焦水蒸氣共氣化加壓和700℃條件下共氣化的結(jié)果表明:生物質(zhì)與生物質(zhì)與煤共氣化反應(yīng)過程首先經(jīng)歷快速熱煤共熱解過程中生物質(zhì)釋放的堿金屬沒有或極少被解,氣化主要是熱解后的半焦與水蒸氣進行反應(yīng).因煤焦吸附因此,生物質(zhì)與煤共氣化反應(yīng)中,生物質(zhì)而本實驗使用生物質(zhì)焦和煤焦進行氣化反應(yīng)的考催化煤焦水蒸氣氣化反應(yīng)的作用并不明顯.堿金屬察,單獨生物質(zhì)在熱解過程中部分堿金屬會揮發(fā)到揮發(fā)不是吸附到煤焦表面的主要途徑,而有可能水氣相,生物質(zhì)與煤共熱解過程中煤焦能否吸附生蒸氣是攜帶堿金屬到煤焦表面的途徑.18在原煤與物質(zhì)中揮發(fā)的這部分堿金屬進而促進共氣化反應(yīng)是生物質(zhì)共氣化中堿金屬的遷移途徑與壓力和溫度的本研究首先考察的內(nèi)容因此,分別在煤和生物質(zhì)先關(guān)系有待于在今后實驗中進一步驗證混合后制焦和先制焦后混合兩種情況下考察了煤焦2.1.3煤和生物質(zhì)共氣化反應(yīng)匹配特性和生物質(zhì)焦共氣化過程中熱解焦對氣化反應(yīng)的影煤焦、生物質(zhì)焦、負載不同碳酸鉀催化劑的煤焦響.煤焦在混合物中的質(zhì)量比分別為20%,40%以及生物質(zhì)與煤混合焦的水蒸氣氣化碳轉(zhuǎn)化率的對60%,80%,共氣化結(jié)果見圖3.圖3中Mc表示高粱比見圖4.圖4表明,在相同反應(yīng)條件下,生物質(zhì)焦的mme700 Mme700040608020406080% Coal char content /M圖3煤焦和高粱秸稈焦水蒸氣共氣化計算值和實驗值對比 Fig. Comparison of calculate value and experimental圖4相同碳含量不同原料水蒸氣氣化的碳轉(zhuǎn)化率比較 value of co-gasification coal char and Fig. 4 Comparison of the carbon conversion sorghum straw char of different samples -Calculate value; -Experimental value水蒸氣氣化反應(yīng)的碳轉(zhuǎn)化率(61.5%)遠大于煤焦的秸稈和煤先制焦后混合;Mmc表示高粱秸稈與煤先碳轉(zhuǎn)化率(25%)和原煤負載5%催化劑的煤焦的碳混合后制焦; Calculate value為單獨煤焦和生物質(zhì)轉(zhuǎn)化率(44.1%),與原煤負載7%催化劑的煤焦的焦氣化實驗所得碳轉(zhuǎn)化率的加權(quán)計算值, Experi-碳轉(zhuǎn)化率(64%)相當(dāng) mental value為每次共氣化實驗中得到的碳轉(zhuǎn)化氣化過程包含熱解和氣化反應(yīng),根據(jù)煤和生物率結(jié)果表明原煤與高粱秸稈以不同比例先制焦后質(zhì)熱解、氣化過程的固定床實驗,計算了先熱解進而混合和先混合后制焦兩種方式,經(jīng)3h共氣化后的氣化3h后煤和生物質(zhì)的總碳轉(zhuǎn)化率,結(jié)果見圖5碳轉(zhuǎn)化率相差均小于2%,說明先混合后制焦和先由圖5可知,負載10%碳酸鉀催化劑煤的總碳轉(zhuǎn)化制焦后混合對氣化反應(yīng)的影響較小.兩種混合條件率(84.86%)與高粱秸稈的總碳轉(zhuǎn)化率(83.59%)相100下不同混合比例碳轉(zhuǎn)化率的實驗值和單獨氣化加權(quán)計算值相差不大,說明在3.5MPa和700℃實驗條件下,煤和生物質(zhì)在共熱解過程中煤焦沒有或極少吸附生物質(zhì)揮發(fā)出的堿金屬,在共氣化反應(yīng)中沒有表現(xiàn)出明顯的催化作用.有學(xué)者研究表明5,79原煤40和生物質(zhì)在常壓和大于850℃條件下共氣化時比原20煤單獨氣化有較高的氣化效率,碳轉(zhuǎn)化率高于兩者 10%K,CO,YM GL單獨氣化的加和,原因是共氣化時生物質(zhì)中的堿金屬吸附到煤焦上并對煤焦氣化起催化作用生物質(zhì)圖5原料熱解和氣化過程總碳轉(zhuǎn)化率 Fig.5 Total carbon conversion of raw material中的鉀分為有機鉀和無機鉀.[15有機鉀占總鉀的比例較小,為10%~30%16,在200℃~400℃制焦 pyrolysis and gasification -Gasification; -Pyrolysis溫度下基本全部析出,無機鉀在400℃~700℃1772煤炭轉(zhuǎn)化2014年當(dāng)表明在煤催化和生物質(zhì)共氣化制甲烷工藝中,生化先增加后減小,最終趨于穩(wěn)定.隨著溫度的升高,物質(zhì)與負載10%碳酸鉀煤可以在時間上實現(xiàn)很好甲烷化反應(yīng)加快,所以甲烷含量隨著溫度升高不斷的氣化反應(yīng)匹配,為流化床氣化爐設(shè)計提供基礎(chǔ)數(shù)增加,溫度達到700℃后,甲烷濃度達到最大值,恒據(jù);另外,在700℃氣化時,煤中催化劑和生物質(zhì)中溫過程中,甲烷含量出現(xiàn)降低趨勢,原因可能是:隨的無機堿金屬鉀基本沒有揮發(fā),減少了堿金屬鉀著停留時間的延長,原料中的殘?zhí)坎粩喟l(fā)生縮聚,碳的損失,可以最大限度地發(fā)揮煤中催化劑和生物質(zhì)化程度進一步提高,活性位降低;另外,隨著反應(yīng)的中堿金屬在水蒸氣氣化反應(yīng)和甲烷化反應(yīng)中的作進行,氫氣的吸附也會占據(jù)一定的活性位,導(dǎo)致甲烷用,同時較少的堿金屬揮發(fā)也降低了對氣化過程后化速率降低1】 Tsutao等20在773K~923K,壓系統(tǒng)的腐蝕,易于實現(xiàn)工業(yè)放大力3.4MPa條件下,研究負載K2CO3催化劑煤焦2.2甲烷化反應(yīng)活性實驗的甲烷化反應(yīng)時,觀察到相同的趨勢,認為甲烷化反應(yīng)活性下降主要是反應(yīng)過程中發(fā)生積碳反應(yīng)引起的2.2.1煤焦和生物質(zhì)焦的甲烷化反應(yīng)活性表2原料中堿金屬與堿土金屬的含量(%)分別以煤焦、高粱秸稈焦和水洗高粱秸稈焦為 Table 2 Alkali metal and alkaline earth metal原料,考察了其對CO和H2的甲烷化反應(yīng)活性的 content of samples(%)影響,并與空管實驗進行了對比(反應(yīng)管對甲烷化反 SampleNa+k+mg2+Ca2+1應(yīng)有一定的催化作用),結(jié)果見圖6.由圖6可知,空y0.05980.15540.13150.2749800GL0.10882.24400.29920.503216600yMJ0.08140.18210.18700.386412GLJ0.30426.25000.96901.56934008▲-MJ Washed GL0.01460.16460.17480.488 -Washed GLJ200 Washed GLJ0.03140.50180.55561.3526 Mass fraction. Bla nk o0501001502002.2.2氣體停留時間對甲烷化反應(yīng)的影響 Time/min由 Aspen Plus軟件計算在700℃,3.5Ma圖6高粱秸稈焦與煤焦甲烷化作用對比H2和CO的流量比為3:1條件下,CH4的平衡體Fig.6 Comparison of sorghum straw char and coal char積分數(shù)為46%.在700℃下,以煤焦和生物質(zhì)焦為 on methanation reactions催化劑時,合成氣生成甲烷的反應(yīng)在動力學(xué)控制的管實驗中CH4在出口氣體中的體積分數(shù)(cH)小范圍內(nèi),研究氣體停留時間對甲烷濃度的影響對于于1%,說明反應(yīng)器本身對甲烷化的催化作用可以流化床反應(yīng)器的設(shè)計有重要意義通過改變反應(yīng)氣忽略;高粱秸稈焦與煤焦相比具有較好的甲烷化反體流量來改變氣體停留時間,停留時間和甲烷濃度應(yīng)活性,但水洗后的高粱秸稈焦甲烷化反應(yīng)活性顯的關(guān)系見圖7.由圖7可知,隨著停留時間的延長,著降低,煤焦甲烷出口體積分數(shù)為4.5%,高粱秸稈60焦甲烷出口體積分數(shù)為10.5%,而水洗高粱秸稈焦50甲烷出口濃度降低至與煤焦相當(dāng)?shù)乃?采用離子401-M30色譜對煤、高粱秸稈和水洗高粱秸稈進行礦物質(zhì)成 3-Equilil20分分析,結(jié)果見表2.由表2可知,高粱中的堿金屬10鉀的含量明顯高于原煤中鉀的含量.通過對比水洗1020304050高粱秸稈和原高粱秸稈中K,Na,Ca,Mg的含量,僅 Residence time/s有堿金屬鉀的含量水洗前后變化比較明顯,水洗后圖7氣體停留時間對高粱秸稈焦和煤焦甲烷化活性的影響的鉀含量大幅降低,與煤焦鉀含量基本相當(dāng),高粱秸Fig.7 Effect of residence time on methanation activity稈中堿金屬鉀含量增減與高粱秸稈焦催化甲烷化作 of sorghum straw char and coal char用強弱相一致.礦物質(zhì)鉀含量和甲烷化反應(yīng)活性之甲烷濃度也逐漸提高,對于流化床反應(yīng)器來說,提高間的對應(yīng)關(guān)系說明鉀是高粱秸稈焦具有較高甲烷活氣體在固體的停留時間有利于提高甲烷濃度.20世性的主要原因紀70年代,美國 EXXON公司在開發(fā)煤催化氣化制由圖6可知,隨著反應(yīng)進行,甲烷含量隨時間變合成天然氣過程中,采用了深床(大的高徑比)操作第2期劉園春等煤與生物質(zhì)共氣化制甲烷實驗研究73的氣化爐,主要目的就是提高煤氣在床層中的停留明顯;從熱解和氣化的耦合結(jié)果來看,高粱秸稈與負時間,以提高甲烷產(chǎn)率,深床流化床氣化爐內(nèi)的流載10%碳酸鉀不連溝煤可以實現(xiàn)水蒸氣氣化反應(yīng)動返混傳熱、傳質(zhì)和反應(yīng)匹配性對含碳固體原料的較好匹配催化氣化制甲烷的影響仍需系統(tǒng)的研究2)高粱秸稈焦的甲烷化活性高于不連溝煤焦3結(jié)論的甲烷化活性,但水洗后高粱秸稈焦的甲烷化活性降低至與煤焦的甲烷化活性相當(dāng),分析表明:水洗后1)在3.5MPa,700℃條件下,高粱秸稈焦的高粱秸稈中的堿金屬鉀的含量顯著降低,表明水溶水蒸氣氣化活性與負載7%碳酸鉀不連溝煤焦的水性鉀是高粱秸稈焦甲烷化活性高的主要原因蒸氣氣化活性相當(dāng);高粱秸稈和煤先混合后制焦與3)以生物質(zhì)為甲烷化催化劑時,隨著停留時間先制焦后混合對水蒸氣氣化反應(yīng)影響較小,這主要的延長,甲烷含量提高,合成氣合成甲烷的反應(yīng)在動是因為生物質(zhì)與煤共熱解過程中生物質(zhì)釋放的堿金力學(xué)控制區(qū),所以對于流化床操作來說,應(yīng)當(dāng)盡量提屬沒有或極少被煤焦吸附,因此,生物質(zhì)與煤共氣化高氣化爐的床層高度,以提高氣固接觸時間,增加甲反應(yīng)中,生物質(zhì)催化煤焦水蒸氣氣化反應(yīng)的作用不烷收率參考文獻1]王明華,李政,麻林巍,等坑口煤制代用天然氣的技術(shù)經(jīng)濟性分析及發(fā)展路線構(gòu)思現(xiàn)代化工2008,28(:13-16[2] Steinberg Process for Conversion of Coal to Natural Gas(snghcei-o-orr. 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State Key Laboratory of Coal-based Low Carbon Energy, ENN, 065001 Langfang, Hebei) ABSTRACT The Inner Mongolia coal and sorghum straw around Taiyuan, Shanxi Province were selected as the samples in this study. The effect of char preparation method, coal/biomass blend ratio and gas residence time were tested on steam gasification reactions and methanation re- actions in a fixed bed reactor under the pressure of 3. 5 MPa and the temperature of 700 C.The results showed that no synergistic effects were observed on steam gasification reaction when co- sification of coal char and sorghum straw char blend. The catalytic activity of sorghum straw gasif char on methanation reaction is higher than that of the coal char, however, the catalysis of sor- ghum straw char is equivalent to coal char after wash with water. Analysis showed that the alkali metal potassium ed a y decreased after water wash. The relation between the methanation activity and potassium amount in biomass showed that the potassium in biomas played the key catalytic effect during methanation reactions. The increase of residence time of gas in the dense zone of the gasifier has significance on the increase of methane yield. KEY WORDS biomass, co-gasification, methanation, alkali metal(上接第68頁) FORECAST MODEL OF GAS-STEAM RATIO BASED ON NEURAL NETWORK IN POWER PLANT OF IRON AND STEEL WORKS Meng Hua Wang Jianjun Wang Hua and Li Hongjuan (Engineering Research Center of Metallurgical Energy Conservation and Emission Reduction Ministry of Education, Kunming University of Science and Technology, 650093 Kunming) ABSTRACT With the gas-steam ratio of self-provided power plant in an iron and steel works taken as an object, flue gas temperature hot air temperature, feed water temperature, air fuel ratio and oxygen content in flue gas are the major factors influencing gas-steam ratio, which is analyzed by grey relation analysis. prediction model of gas-steam ration of self-provided pow- er plant is established on the basis of BP neural network, which is a 5-12-1 network structure, the hidden layer and outp put layer is transferred by tansig and purelin function respectively, mo- mentum gradient descent op tion algorithm, traingdm is also used to train network. The re sults show that the model can effectively predict the gas-steam ratio of boiler, the correlation co- efficient of actual values and training ones is 0. 993 7, and the correlation coefficient of actual values and prediction ones is 0. 976 2, the mean absolute error is also controlled within the scope. Showing a good generalization ability and outreach capacity we can provide a theoretical basis and guide for the real production. KEY WORDS grey relation degree, BP neural network, gas-steam ratio, self-provided power plant, momentum gradient descent algorithm