纤维素热裂解试验研究及分析

利用自行设计的固定床热裂解试验系统,在不同压力条件下,研究了纤维素的热解行为,在常压下分别考察热解温度、N2流量对热解产物的影响。研究结果表明,热解温度为450℃时,可得到较高收率的液体产物,并且液体产物的收率随着N2流量的增加而降低。当压力降低时,在450℃热解温度下液体产物的收率最高,为58.6%,比常压热解提高12.3%,生物油中水分含量随着热解温度的升高而升高。试验对在不同真空度下热解得到的液体产物进行了元素分析。     

生物质热解分级冷凝制备多品级生物油

为了分品级充分利用生物油,根据其组分之间物理化学性质的差异,通过控制冷凝温度,在不同冷凝段对沸点相近的物质进行收集,建立一套生物质热解分级冷凝中试装置。采用螺旋式热解反应器,冷凝器设计为4级,其中第1级冷凝器采用喷雾方式进行直接冷却,其余各级均采用列管式换热器进行间接冷却。试验结果表明:4级冷凝器的出口温度分别设置为220、105、70、20℃时,不同喷淋介质对1、2级冷凝器生物油收率的影响不大,使用甲醇喷淋时,第4级冷凝器生物油收率较高;而Bio-3喷淋时,第3级冷凝器生物油收率较高,且第2级生物油和第4级生物油的热值升高、粘度增大,同时N元素和S元素含量也会增大。GC/MS分析表明,第2级生物油的主要成分为苯酚、间甲酚、4-乙基苯酚、4-甲基愈创木酚等酚类产物,其作为化工原料价值较高;第3级生物油具有最高含量的水和乙酸,同时含有少量酚类,可能用作木醋液;第4级生物油的成分主要为苯、甲苯、苯酚、4-乙基苯酚等高热值组分,同时其热值较高、水分较低、粘度稍大,经过甲醇稀释等降粘处理后可用作液体燃料。     

内循环串行流化床生物质催化热解试验研究

在处理量为0.2 kg/h的新型内循环串行流化床(IIFB)上进行了生物质催化热解制油的试验研究.以木屑为原料、石英砂为热载体,研究了在没有催化剂条件下反应温度对热解产物分布的影响;以HZSM-5催化剂与石英砂混合物为床料进行了催化热解试验,并对热解产物和反应后的催化剂进行了表征分析.结果表明:反应温度为515℃时,液体产物的收率最高.HZSM-5催化剂的加入促进了气体以及焦炭的生成,使液体产物的收率降低,且催化剂体积分数越大,影响越显著.催化荆表面的积炭经燃烧反应后被除去,催化剂的稳定性得到改善.热解不可冷凝气体的主要成分为CO和CO2,随着热解温度的升高,CO2产量下降,CO和CH4的产量增加.经HZSM-5催化热解后,生物油中的酸、醛和酮类物质含量明显减少,而小分子的烃类与酚类物质含量明显增加,表明催化剂具有明显的脱氧效果.     

四氢萘预处理生物质快速热解制取酚类

文章提出一种以四氢萘(Tetralin,THN)为溶剂预处理生物质快速热解的方法,以实现生物质中羟基(氧)有效转移到酚类化合物中,降低热解油酸类含量。热解实验采用固定床反应器,考察了热解后气、液、固产率,采用气相色谱仪、气质联用仪及傅里叶红外光谱仪分别对热解气、液、固进行分析,结果表明,THN预处理能够有效提高核桃壳(Walnut Shell,WS)的液体产率。对热解后液体产物组分分析发现:THN预处理后液体产物中的酚类含量升高,酸类含量降低,且THN添加量越大,这种趋势越明显;当WS和THN质量比为1∶0.5时,液体产物中酚类含量为59.6%,较理论值(33.11%)增幅最大,且液体产物中几乎无酸类物质,对生物油品质提升效果最佳。     

稻草在离子液体([Emim]Br)中的热解研究

为研究离子液体对植物纤维素热解行为的影响,以稻草为原料,在离子液体溴化3-甲基-1-乙基咪唑([Emim]Br)中进行热解反应,考察了反应温度、离子液体与稻草的质量比及反应时间对生物油产率的影响,得到热解较佳工艺条件:热解反应温度为230℃,离子液体与稻草的质量比为2∶1,热解反应时间为45 min,生物油得率达到38.1%。对热解得到的生物油进行GC-MS分析,呋喃类和苯酚类物质的含量较高,分别占17.17%和21.98%。     

核桃壳热裂解产物有机结构演变规律

采用TG-FTIR、Py-GC/MS对核桃壳热裂解过程及产物进行研究,利用1H-NMR和13C-NMR对热解炭结构进行分析,探讨热裂解产物有机结构演变规律。结果表明:核桃壳热裂解分为干燥脱水,快速热裂解和残余物缓慢热裂解三个阶段,快速热裂解阶段是主反应阶段,失重可达总失重的89%。不同热解温度下的液态产物成分不同,且随着热裂解温度的升高,低温下形成的热解液会发生二次反应生成新的热解液成分,热解温度由400℃升至600℃,液态产物完成了由酚类、醇类、酸类向酯类、芳香类的转化。升温核桃壳热裂解过程中的气态产物为H_2O,CO_2,CH_4和CO,在357℃时达到最大产量。随着热解温度由300℃升高到800℃,核桃壳热解炭由以苯环、烷烃链、甲氧基、羟基、羰基为主要结构转化为90%以上的芳香结构。     

不同酸处理条件下生物质热解产物特性分析

采用固定床热解反应器系统与气相色谱和质谱分析仪以及等温吸附仪等,研究不同酸处理条件对农业废弃物棉秆热解的产物特性的影响。结果表明:用H3PO4处理时,液体产物产率在H3PO4(8%)时较大,用H2SO4处理时,液体产物产率在H2SO4(4%)时较大,而后随H2SO4添加量的增大有所减小,而固体产物产率逐渐增大;在酸处理条件下,气体产率均明显降低,酸处理对简化生物油组分以及提高生物油品质效果显著;与原生物质热解油相比,酸处理后产物中酚类物质含量明显降低,乙酸和糠醛的相对含量由23.70%和2.49%最高至43.29%和36.02%,而且热解固体焦的表面孔隙结构也得到明显改善。     

松木粉热解和生物油精制的实验研究

选用60~100目的松木粉在流化床上进行快速热解实验,在反应温度550℃及载气流量3 m3/h的条件下,热解产物中油相18.7%,水相15.9%,焦炭46.2%,气相19.2%(质量分数)。对生物油进行理化特性及元素分析,利用气相色谱-质谱联用仪对生物油成分进行定性分析。将收集的生物油进行催化裂化改质,改质生物油收率为42.81%,其中轻质芳香烃(苯、甲苯、二甲苯、萘)含量达61.13%。     

纤维素热解生物油特性研究

为深入了解生物质热解生物油的特性,对生物质的主要成分纤维素热解生物油的析出和演变特性进行研究。在固定床上研究纤维素在不同温度(280~550℃)下的快速与慢速热解以及不同气相停留时间对纤维素生物油特性与组成的影响。研究表明,纤维素快速热解生物油由左旋葡聚糖及大量脱水糖组成,还有少量呋喃衍生物(如糠醛、5-羟甲基糠醛等)。慢速热解时产生的脱水糖种类较少,但小分子化合物种类更多。随着气相停留时间的缩短,液体产物中左旋葡聚糖含量逐渐升高,酸、醛等小分子消失。     

烘焙预处理对秸秆热解产物品质及能量分布的影响

以玉米秸秆为原料,研究烘焙温度(220、250和280℃)对秸秆热解产物产率、品质和能量分布的影响。结果表明:秸秆经220、250和280℃烘焙后,热解生物油水分相比原样分别降低11.4%、28.3%和41.8%;与此同时,生物油中酸类产物逐渐减少,酚类产物逐渐增多,生物油热值明显增大。烘焙对热解气中CH_4和H_2有一定促进作用,可燃气的热值逐渐增大。烘焙对生物质炭的化学组分无明显影响,但随着生物质炭产率的增大,其能量产率逐渐增大。烘焙脱氧预处理可改善生物油的品质、提高可燃气的热值、增大生物质炭的能量产率。     

稻壳连续热解特性研究

在自行研制的生物质连续热解反应装置上进行稻壳连续热解和二次裂解实验研究。随着稻壳热解温度的提高,炭产率降低,气体产率增加,液体产率先增加后减少;随着滞留时间的减少,炭产率、液体产率增加,气体产率减少。稻壳热解气以CO2和CO为主,且二者为竞争关系,热解温度提高,CO2产量降低,CH4、H2、C2H4、C2H6产量增加,CO的产率变化不大;滞留时间对热解气组分影响不大。二次裂解温度提高,裂解气中的H2、CH4、C2H4含量明显增加,二次裂解温度为800℃时,H2产率达到12%。稻壳500℃热解挥发物600℃二次裂解木醋液中醋酸含量高达49.44%,焦油中检测到的物质主要为丙酮和异丙醇。     

沼渣热解动力学、热力学分析及热解产物特性研究

采用热重分析（TG）分析沼渣的热解特性,研究沼渣的热解动力学并计算指前因子A、焓变ΔH、吉布斯自由能ΔG、熵变ΔS等热力学参数。进一步考察温度对沼渣热解产物分布与性质的影响。其热解过程可分为3个失重阶段,其中第2阶段为主要失重阶段,采用Flynn-Wall-Ozawa（FWO）法、Friedman法和Kissinger-Akahira-Sunose（KAS）法计算的平均活化能分别为410.00、471.32和420.01 kJ/mol,热力学参数计算结果表明沼渣热解过程具有稳定的能量输出。沼渣热解油的产率随温度上升先增加后降低。气体产物的高位热值（HHV）从400 ℃时的6.82 MJ/Nm³增加到700 ℃时的8.54 MJ/Nm³。红外光谱（FTIR）、拉曼（Raman）光谱表明热解温度升高生物炭结构的有序性增加。     

Fixed-Bed Pyrolysis of Hazelnut (Corylus Avellana L.) Bagasse: Influence of Pyrolysis Parameters on Product Yields

Fixed-bed slow pyrolysis experiments have been conducted on a sample of hazelnut bagasse to determine particularly the effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rate on the pyrolysis product yields. The temperature of pyrolysis, heating rate, particle size and sweep gas flow rate were varied in the ranges 350–550° C, 10 and 50° C/min, 0.224–1.800 mm and 50–200 cm³/min, respectively. Under the various pyrolysis conditions applied in the experimental studies, the obtained char, liquid, and gas yield values ranged between 26 and 35 wt%, 23 and 34.40 wt%, and 25 and 32 wt%, respectively. The maximum biooil yield of 34.40% was obtained at the final pyrolysis temperature of 500°C, with a heating rate of 10° C/min, particle size range of 0.425–0.600 mm and a sweep gas flow rate of 150 cm³/min.     

Bio‐oil production from rapid pyrolysis of cottonseed cake: product yields and compositions

Fixed‐bed fast pyrolysis experiments have been conducted on a sample of cottonseed cake to determine the effects of pyrolysis temperature, heating rate and sweep gas flow rate on pyrolysis yields and chemical compositions of the product oil. The liquid products and the subfractions of pentane soluble part were characterized by elemental analysis, FT‐IR spectroscopy, ¹H‐NMR spectroscopy and pentane subfraction was analysed by gas chromatography. The maximum oil yield of 34.8% was obtained at final temperature of 550°C with a heating rate of 700°C min^?1 and nitrogen flow rate of 100 cm³ min^?1. Chromatographic and spectroscopic studies on bio‐oil have shown that the oils obtained from cottonseed cake can be used as a renewable fuel and chemical feedstock. Copyright © 2005 John Wiley & Sons, Ltd.     

Experimental analysis of pyrolysis of sewage sludge

Pyrolysis is a thermal process where organic materials such as biomass and oil are decomposed and lighter materials such as gas, vapor, liquid products, and char are produced. The aim of this study was to investigate the pyrolysis behavior of sewage sludge in different operating conditions. Using a fixed bed, the influence of some important parameters such as pyrolysis temperature, heating rate, particle size, and N₂ flow rate on product yields was studied. Results showed that with increase in temperature from 400 to 700°C, the char yield decreased from 30.1 to 7.50%, while the gas yield increased from 35.8 to 52.4%. The gas yield also increased from 46.9 to 49.1% as the heating rate increased from 20 to 60°C/s, while the oil yield increased from 45.2 to 46.8% as heating rate increased to 40°C/s and then the increase leveled off.     

Pyrolysis of giant mullein (Verbascum thapsus L.) in a fixed-bed reactor: Effects of pyrolysis parameters on product yields and character

Slow pyrolysis of giant mullein (Verbascum thapsus L.) stalks have been carried out in a fixed-bed tubular reactor with (Al₂O₃, ZnO) and without catalyst at four different temperatures between 400 to 550°C with a constant heating rate of 50°C/min and with a constant sweeping gas (N₂) flow rate of 100 cm³/min. The amounts of bio-char, bio-oil, and gas produced were calculated and the compositions of the obtained bio-oils were determined by gas chromatography-mass spectrometry. The effects of pyrolysis parameters, such as temperature and catalyst, on the product yields were investigated. The results show that both temperature and catalyst have significant effects on the conversion of Verbascum thapsus L. into solid, liquid, and gaseous products. The highest liquid yield of 40.43% by weight including the aqeous phase was obtained with 10% zinc oxide catalyst at 500°C temperature. Sixty-seven different products were identified by gas chromatography-mass spectrometry in the bio-oils obtained at 500°C temperature.     

Characterization of bio-oil obtained from fruit pulp pyrolysis

Apricot pulps was pyrolyzed in a fixed-bed reactor under different pyrolysis conditions to determine the role of final temperature, sweeping gas flow rate and steam velocity on the product yields and liquid product composition with a heating rate of 5 °C/min. Final temperature range studied was between 300 and 700 °C and the highest liquid product yield was obtained at 550 °C. Liquid product yield increased significantly under nitrogen and steam atmospheres. For the optimum conditions, pyrolysis of peach pulp was furthermore studied. Liquid products obtained under the most suitable conditions were characterized by FTIR and ¹H-NMR. In addition, gas chromatography/mass spectrophotometer was achieved on all pyrolysis oils. Characterization showed that bio-oil could be a potential source for synthetic fuels and chemical feedstock.     

Rapid and slow pyrolysis of pistachio shell: effect of pyrolysis conditions on the product yields and characterization of the liquid product

This study reports the experimental results for the pyrolysis of pistachio shell under different conditions in a tubular reactor under a nitrogen flow. For the different conditions of pyrolysis temperature, nitrogen flow rate and heating rate, pyrolysis temperature of 773 K gave the highest bio-oil yield with a value of 27.7% when the heating rate and carrier gas flow rate were chosen as 300 K min⁻¹ and 100 cm³ min⁻¹, respectively. Column chromatography was applied to this bio-oil and its subfractions were characterized by elemental analysis, FT-IR and ¹H-NMR. Aliphatic subfraction was conducted to gas chromatography–mass spectroscopy for further characterization. The results for the characterization show that using pistachio shell as a renewable source to produce valuable liquid products is applicable via pyrolysis. Copyright © 2006 John Wiley & Sons, Ltd.     

生物质快速热解气相成分析出规律

利用恒温沉降炉对秸秆、稻壳、木屑及一种烟煤煤粉在900、1000、1100℃ 3个温度进行了快速热解试验,对4种燃料在快速热解过程中气相成分析出的规律进行了研究.生物质成分中高的挥发分、氧、H/C决定了其快速热解会取得比煤粉高的气相产率,木屑的气相产物产量最多,秸秆次之,稻壳最低.4种燃料热解气相产物中的主要成分是CO、H_2、CO_2、CH_4,少量的G_2H_4、C_2H_6、NO、HCN、COS,生物质和煤粉在快速热解及短的停留时间内,其析出的氮前驱物为HCN.快速热解析出的气相成分产量及组分分布与燃料种类、热解温度、热解停留时间相关.几种物料共同的规律是随停留时间的延长,气相产物的量不断地增加,当气相产物的产量趋于平稳时,相应的气相产物的各组分趋于恒定,这一停留时间标志着热解过程的结束,相同温度条件下煤粉的热解速率要慢于3种生物质.     

纤维素催化热解定向调控制取不含氧烃类液体燃料

为了将生物质能高效转化为高品位不含氧的液体燃料,以纤维素为例,研究了以催化热解方式将热解产物转化为芳香烃类液体燃料的过程.实验发现,纤维素热解产生的含氧有机小分子,可以通过催化热解的形式高效转化为不含氧的芳香烃类液体.催化剂采用HZSM-5(23)、催化剂原料质量比例为5∶1、热解温度为650℃、升温速率为10000 K/s的工况为纤维素催化热解的最佳工况,单环芳烃、多环芳烃产率分别为9.90%和12.91%,总芳香烃类产率为22.81%.热解温度提升至650℃前,更高的热解温度能获得更高的芳香烃产率.继续提高热解温度,单环芳烃、多环芳烃分子间还可能进一步发生聚合反应,最终产生积碳.同时本文也提出了一种可行的纤维素催化热解中的反应途径,与本文实验结果较为匹配.