生物质催化热解研究进展

介绍了生物质种类、生物油性质、热解反应条件对生物油产率和油品质的作用以及催化剂对催化热解反应的影响。生物质催化热解技术能够实现资源、能源、环境的高效统一,符舍社会的可持续发展原则,具有很大的开发前景。     

生物质热解液化技术经济分析

我国生物质资源十分丰富，但主要以各类农业残余废弃物为主，其特点是能量密度低、分布不集中，如果采用热解液化技术在产地将其先分散转化成生物油，然后再对生物油进行应用或再加工，则就避免了大规模收集和长距离运输生物质所带来的巨大困难。研究分析表明：热解液化设备的规模以每小时可处理2t农业残余废弃物较为适宜，且这种技术在我国具有良好的市场应用前景。     

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。     

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.     

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.     

Pyrolysis of Xanthium strumarium in a fixed bed reactor: Effects of boron catalysts and pyrolysis parameters on product yields and character

Pyrolysis of Xanthium strumarium has been performed in a fixed-bed tubular reactor with boron minerals (ulexite, colemanite, and borax) and without catalyst at three different temperatures ranging from 350°C to 550°C with heating rate of 50°C/min. The amounts of bio-oil, bio-char, and gas generated, also the compositions of the resulting bio-oils were identified by GC-MS and FT-IR. The influences of pyrolysis parameters, such as temperature and catalyst on product yields were investigated. Temperature and catalyst were found to be the main factors affecting the conversion of Xanthium strumarium into solid, liquid, and gaseous products. The highest liquid yield (27.97%) including water was obtained with 10% colemanite (Ca₂B₆O₁₁.5H₂O) catalyst at 550°C temperature at a heating rate of 50°C/min when 0.224 > D_p > 0.150 mm particle size raw material and 100 cm³/min of sweeping gas flow rate were used.     

Fast and catalytic pyrolysis of xylan: Effects of temperature and M/HZSM-5 (M= Fe,Zn) catalysts on pyrolytic products

Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was employed to achieve fast pyrolysis of xylan and on-line analysis of pyrolysis vapors. Tests were conducted to investigate the effects of temperature on pyrolytic products, and to reveal the effect of HZSM-5 and M/HZSM-5 (M= Fe, Zn) zeolites on pyrolysis vapors. The results showed that the total yield of pyrolytic products first increased and then decreased with the increase of temperature from 350°C to 900°C. The pyrolytic products were complex, and the most abundant products included hydroxyacetaldehyde, acetic acid, 1-hydroxy-2-propanone, 1-hydroxy-2-butanone and furfural. Catalytic cracking of pyrolysis vapors with HZSM-5 and M/HZSM-5 (M= Fe, Zn) catalysts significantly altered the product distribution. Oxygen-containing compounds were reduced considerably, and meanwhile, a lot of hydrocarbons, mainly toluene and xylenes, were formed. M/HZSM-5 catalysts were more effective than HZSM-5 in reducing the oxygen-containing compounds, and therefore, they helped to produce higher contents of hydrocarbons than HZSM-5.     

Influence of metal (Fe/Zn) modified ZSM-5 catalysts on product characteristics based on the bench-scale pyrolysis and Py-GC/MS of biomass

In this study, sawdust was selected as the raw material for biomass pyrolysis to obtain organic products. The catalyst was modified with two elements (Fe and Zn). Through analysis of the catalytic products, we attempted to identify a pyrolysis catalyst that can improve the yield of aromatic hydrocarbon products. ZSM-5, modified with Fe and Zn, was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and Brunauer–Emmett–Teller (BET) measurements. Tube furnace and flash pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) were used to comprehensively investigate the characteristics of the products of biomass pyrolysis. The highest yield of phenols was obtained using the Fe-modified ZSM-5 catalyst, which was 18.30% higher than the yield obtained by the pure ZSM-5 catalyst. The lowest yield of acid products was obtained by single-metal-supported catalytic pyrolysis with Fe or Zn, which was 50.66% lower than the yield obtained by direct pyrolysis. During the pyrolysis of biomass using metal-modified catalysts, the production of aromatic hydrocarbons was greatly improved. Among them, compared with direct pyrolysis, the Fe-Zn co-modified ZSM-5 catalyst exhibited the weakest promotion of aromatic hydrocarbon formation, but there was still a 68.50% improvement. Although the co-modified catalyst did not show absolute advantages under the conditions used for this experiment, the improvements in the production of aromatics and phenolic products also showed its potential for improving bio-oil products. Under the action of Fe-modified catalysts, the most abundant components in the gas product were CO and CO₂, which reached levels as high as 53.45% and 15.34%, respectively, showing strong deoxidation capabilities. Therefore, Fe-modified ZSM-5 catalysts were found to better promote the formation of aromatic hydrocarbon products of biomass pyrolysis.     

Correlation for estimation of the chemical availability (exergy) from ultimate analysis of pyrolytic oils obtained from fast pyrolysis of biomass

The purpose of this study is to evaluate the chemical exergy (E^CH) of liquid products obtained from fast pyrolysis of biomass. I have calculated the chemical exergy values from a formula in literature and have developed a formula for estimating the chemical exergy of biomass from the higher heating value and their ultimate analysis values. The mean differences between these values range from –0.391% to 0.460%. The formula developed for estimating the chemical exergy of biomass from the higher heating value and their ultimate analyses had a correlation coefficient (R² = 0.9999), and the prediction of this formula is good. The goal is to identify desirable attributes that may serve as the basis for decision-making for future biofuel options. Studies on the pyrolytic oils showed that the oils obtained from chestnut cupulae and maple fruit can be used as a renewable fuel and chemical feedstock.     

稻壳热解气化特性的试验研究

以稻壳为试验原料,DHC-32为催化剂.高纯N2为载气,在管式炉中研究了热解温度和DHC-32催化剂对稻壳热解气化特性的影响.试验结果表明:稻壳热解气中H2,CO含量随热解温度升高而增加,CH4CO2含量随热解温度升高而呈下降趋势;添加DHC-32催化剂后,未改变H2,CO,CH4,CO2含量随热解温度的变化趋势,但对4种气体的相对含量有一定的影响;在试验温度范围内,添加10%DHC-32催化剂比3%DHC-32催化剂对稻壳热解气影响更大一些.     

裂解温度对生物质热解焦油成分的影响

以锯末粉体为生物质热解焦油研究对象,研究了热解温度对焦油产量和焦油化学成分的影响规律,结果表明,热解温度为500℃时,生物质热解产生的焦油量最大,温度过高或过低都有利于焦油的减少。不同热解温度下,焦油中碳氢化合物的成分主要是芳香烃和少量的脂肪烃,含氧化合物主要是苯酚及其烷基衍生物,含氮化合物主要是吡啶、吡咯及其烷基衍生物等杂环化合物。     

Low‐temperature pyrolysis of municipal solid waste: influence of pyrolysis temperature on the characteristics of solid fuel

This paper presents the results of pyrolysis experiments of the mixtures of nine different combustibles municipal solid wastes (MSW's main composition: rice 24.33% and fruits 14.60%). The experiments were carried out in a laboratory‐scale reactor under nitrogen atmosphere at temperature of 300–700°C. The study concentrates on low‐temperature pyrolysis of MSWs and the effect of the pyrolysis temperature on the characteristics of the products (solid fuels) including proximate analysis, volatile content, heating value, ignition temperature and density of the solid fuel. The results indicate that the pyrolysis temperature plays an important role on the characteristics of the solid fuels. The volatile content of the solid fuels decreases with the pyrolysis temperature so that the low‐pyrolysis MSW treating process has advantage for higher heating value of the solid fuel for energy recovery purpose. The heating value is in the range of 23–27 MJ kg^?1, equivalent to the heating value of low‐rank coals. Copyright © 2005 John Wiley & Sons, Ltd.     

Effect of pyridine extraction on the pyrolysis of a perhydrous coal based on in-situ FTIR analysis

Pyridine extraction of coal can separate the small molecules from macromolecule skeleton and subsequently impacts the thermal behavior of coal. A perhydrous bituminous coal with a high content of volatile matters was extracted by pyridine under microwave irradiation with an extraction yield of 24.6% on the dry, ash free basis (daf). The thermal behavior of the raw coal, its extract and residue was investigated by thermogravimetric analysis and in-situ Fourier Transform Infrared Spectroscopy (FTIR) based on the evolution of weight loss and functional groups, respectively. Though pyridine extraction had only slight effect on TG curve of the perhydrous coal, it greatly influenced the evolution of functional groups during pyrolysis. Aromatic CH and CO was the most susceptible to pyridine extraction because the absence of extractable moieties reduced the production of radicals and the reactions between small molecules and macromolecules during pyrolysis. The interactions between extractable small molecules and non-extractable macromolecules could retard the decomposition of aromatic CC and hydroxyls. The evolution of aliphatic groups and CO was slightly impacted due to the occurrence of the abundant aliphatic side groups and bridge bonds in macromolecule structures.     

玉米秸秆热解规律的试验研究

用热重分析法对玉米秸秆的热解规律进行了研究，分析了玉米秸秆样品在不同升温速率（5，10，20，30℃／min）、不同温度（250，300，350℃）恒温加热2h条件下热解的试验结果，发现样品的非等温失重过程由脱水、保持、剧烈失重和缓慢失重4个阶段组成，并且在相同条件下，样品的质量对玉米秸秆热解有一定的影响。在恒温热解过程中，在不同的恒温温度条件下，秸秆失重曲线形态基本相似，但在300℃条件下，恒温热解的热重曲线与250，350℃条件下恒温热解的热重曲线相比较为平缓。     

The influence of harvest and storage on the properties of and fast pyrolysis products from Miscanthus x giganteus

The research investigates the fuel property variations associated with the time of harvest and the duration of storage of Miscanthus x giganteus over a one year period. The crop has been harvested at three different times: early (September 2009), conventional (April 2010) and late (June 2010). Once harvested the crop was baled and stored. Biomass properties of samples taken from different storage zones were compared. The thermochemical properties have been investigated using a range of analytical equipment including thermogravimetric analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). In addition, bio-oil has been produced from the early, conventional and late harvest using a laboratory scale (300 g h⁻¹) fast pyrolysis unit. The potential organic liquid yield (on dry basis, also excluding the reaction water generated) based on the laboratory fast pyrolysis processing undertaken in this study, was found to vary between 2.82 and 3.18 dry t ha⁻¹ for the early and the late harvest respectively. The bio-oil organic yield was reduced by approximately 11% (0.36 t ha⁻¹) between the early and the late harvest. Char yield was also reduced by approximately 18% (0.61 t ha⁻¹). The highest gas yield (18.03%-1.60 t ha⁻¹) was observed for the conventional harvest. Gas chromatography-mass spectrometry (GC-MS) analysis of the bio-oil shows that levoglucosan, methylbenzaldehyde and 1,2-benzenediol all increase as a consequence of delayed harvest. It was also observed that by delaying the harvest time the O:C atomic ratio is reduced and a more carbonaceous feedstock is produced.     

Experimental investigation on the influence of the pyrolysis operating parameters upon the char reaction activity in supercritical water gasification

Supercritical water gasification of coal is a clean and efficient method for coal utilization which can convert coal into H₂ and CO₂. In order to further reduce costs, a novel two-step cascade utilization method was proposed in this study: conducting traditional pyrolysis first and then gasifying the pyrolysis char in supercritical water. The influences of different pyrolysis operating parameters on gaseous products and char gasification in supercritical water were investigated. Quartz tube reactors were used to ensure the complete collection of gaseous products in pyrolysis process. The experimental results showed that both carbon and hydrogen conversion efficiency increased with temperature, and the increasing trend became not obvious after reaction for 5 min. The thermo-gravimetric curves showed that volatilization removal process was completed at the pyrolysis time of 5 min and higher pyrolysis temperatures were beneficial to the subsequent gasification process. The result also showed that residual weight was 15%–20% of the initial weight. Hydroxyl radicals kept stable during pyrolysis process with the absorption peak intensity increasing first and then decreasing, and mineral substance disintegrated gradually as time increased. As pyrolysis temperature increased, the peak of CC double bonds decreased, turning into stable functional groups and carbonyl group increased. Dispersive pores occurred at the surface of coal as residence time increased with particle size decreasing, specific surface area and reactivity increasing. The results might be used for the design of a cascade utilization system based on coal gasification in supercritical water.     

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.     

Studies on catalytic pyrolysis of empty fruit bunch (EFB) using Taguchi's L9 Orthogonal Array

This paper investigates the effects of four reaction parameters that include type of catalyst, catalyst loading, reaction temperature and nitrogen gas flowrate on the liquid (bio-oil) yield from the catalytic pyrolysis of Empty Fruit Bunch (EFB). The experimental design is based on Taguchi's L9 Orthogonal Array in which the reaction parameters are varied at three levels. The maximum liquid yield is predicted based on systematic experimental runs, and is found to be at 5 wt-% of H-Y catalyst, 500 °C and at nitrogen flowrate of 100 ml min⁻¹. The predicted maximum liquid yield is validated with an experimental run at the corresponding predicted conditions. The bio-oil produced at the optimum reaction condition is characterized and compared with known bio-oil standards in the literature.     

SCR烟气脱硝效率及催化剂活性的影响因素分析

分析了影响选择性催化还原法烟气脱硝性能的主要因素,重点分析了脱硝效率及催化剂活性随反应温度、NH3/NOx摩尔比、入口NOx浓度等参数的变化规律.     

Influences of sodium species with different occurrence modes on the thermal behaviors and gas evolution during pyrolysis of a sodium-rich Zhundong subbituminous coal

The Zhundong coal (ZDC) with a huge proven reserve is featured by high abundance of sodium species which behaves actively in the thermal conversion of it. In this work, to better understand the multiple roles of sodium species in coal pyrolysis, influences of sodium species with different occurrence modes on the thermal behaviors and gas evolution during pyrolysis of a sodium-rich ZDC were investigated. Raw coal was initially demineralized by dilute hydrochloric acid. Subsequently, sodium species was reloaded into the demineralized sample by ion-exchanged or immersed method. For quantitative analyses, a thermo-gravimetric analyzer coupled with a mass spectrometer was used to record the weight loss of different samples and the ever-changing amount of gaseous products in pyrolysis. The results show that the structural change induced by demineralized and ion-exchanged treatment is mainly reflected in the band intensity of carboxyl groups. In pyrolysis of ZDC, total volatile matters yield has a close relation with the occurrence modes of sodium species. It is proved that water-soluble sodium species has catalytic effects on the thermal-cracking reactions, whereas exchangeable sodium species tends to facilitate char-formed reactions. Compared with exchangeable ones, water-soluble sodium species can be also volatilized more easily in pyrolysis. As for gas evolution, exchangeable sodium species can obviously affect formation of CO through char gasification and it is also favorable to formation of hydrogen radicals. Moreover, due to the low sulfur content in ZDC, the intensity of H₂S released from all samples is extremely weak, which suggests that ZDC is a suitable feedstock for clean coal utilization.