造纸废渣水蒸气气化制取富氢燃气实验研究

目前造纸废渣的主要处理方式为焚烧,虽然该工艺简单有效,但会产生二噁英等有害物质,因此部分地区环保部门开始限制新建焚烧项目。针对造纸废渣处理难的问题,结合废物特性,探索使用气化工艺对其进行处理。在700～900℃利用水蒸气与造纸废渣共同反应制取富氢燃气,并进一步研究了CaO、MgO作为催化剂对气化反应的影响。结果显示：气化温度为900℃,产气中H₂的比例超过50%;两种催化剂均可催化大分子有机物分解为气体小分子,导致燃气热值及气化效率提高。     

林产废弃物高温水蒸气气化制取清洁燃气

基于下吸式固定床气化炉,自建了生物质蒸汽气化实验平台,使用松木屑预处理后的成型颗粒进行富氢气化实验,研究分析了不同温度下的燃气组分、产氢率、燃气产率、燃气热值和冷煤气效率等指标.结果表明:高温水蒸气能有效促进水蒸气重整反应正向进行;随着温度的升高(700℃升高至900℃),H_2体积分数增大了50%,产氢率升高了2.5倍,燃气产率升高了近70%,冷煤气效率提高了37%;参与气化反应的高温水蒸气拥有较高的比焓,能够有效促进水蒸气重整反应向生成H_2的方向进行;气化温度的升高可以促进反应向正向进行,提高气体产物产量;以松木屑为例的林产废弃物高温水蒸气气化产气优良,在实验过程中稳定燃烧,理论上可应用于工业生产.     

生物质回转窑水蒸气气化制富氢气体试验研究

为充分回收高温炉渣颗粒的余热,设计了回转窑热解反应装置。为验证此装置的可行性,对生物质气化制氢进行了试验研究,并对影响气化性能的主要因素,如气化温度(650~950℃)和水蒸气/生物质当量比S/B(0~3.0)进行了研究。结果表明:温度是影响生物质气化反应的主要因素,高温可以降低焦油和焦炭产率,提高气体产量,增加燃气中氢气含量;水蒸气的加入,有利于焦油和低分子碳氢化合物的气化重整以及焦炭的反应,降低焦油产量,提高气体产量,增加燃气中氢气含量,但是过量的水蒸气会导致反应器内温度下降,不利于反应进行。当S/B为2.20时,气化燃气中氢气含量达到最大值53.6%。     

生物质二级固定床催化热解制取富氢燃气

针对二级固定床反应器(第一级是热解反应器,第二级是催化反应器),以制取富氢燃气为目标,分别采用稻壳、秸秆、锯末为原料,重点考察了固定床催化反应器在不同反应条件下对产气量、产氢率和焦油含量的影响.与一级热解反应相比,在催化反应器温度为750℃时,稻壳热解的产气量提高了22%,氢气的体积含量提高了50.3%;通过使用煅烧白云石和镍基催化剂,稻壳热解的产气量提高了36.6%,氢气的体积含量提高了76.2%.催化反应器温度为815℃时,秸秆和锯末的热解实验结果与温度为750℃时具有相同的趋势,且催化固定床能够有效降低燃气中焦油的含量,可降至原来含量的1%.催化剂负载量和燃气空速对产气量和氢气浓度都有影响.催化剂负载量为生物质送料量的30%、燃气空速为0.9×104h-1时,实验结果相当满意.     

生物质富氧——水蒸气气化制氢特性研究

以一个鼓泡流化床为反应器,对生物质富氧—水蒸气气化制取富氢燃气的特性进行了一系列的实验研究。通过对试验数据的分析,探讨了主要参数温度、水蒸气/生物质(S/B)和氧浓度对气体成分、氢产率和潜在产氢量的影响。结果表明:在3个主要参数的变化范围内,氢产率和潜在氢产量受温度的影响最大:当温度从700~900℃时,每千克生物质氢产量从18g增加到了53g,每千克生物质潜在氢产量从71.6g增加到了115.6g。     

水蒸气气氛下生物质热解制取富氢气体试验研究

以水蒸气为流化气在鼓泡流化床中进行木屑的热解特性研究,考察一些主要参数[如热解温度、生物质颗粒粒径、水蒸气/生物质(S/B)]对产气率和目标气体(H2,CO)产率的影响.试验结果表明,提高热解温度和降低生物质颗粒粒径有利于气体的产生;在热解过程中加入水蒸气,能提高气体产率,但是水蒸气的引入量有一个最佳值.本试验中产气率和H2,CO的产率都随着S/B的增加先上升后降低,适宜的S/B为2～2.5.     

生物质流化床催化气化制取富氢燃气

以流化床和固定床为反应器，以制取富氢燃气为目标，对生物质催化气化进行了研究。实验所用催化剂为白云石和镍基催化剂。白云石作为流态化催化剂在流化床内使用；镍基催化剂在流化床出口的固定床反应器内使用。重点研究了不同固定床反应条件对气体和氢产率的影响。固定床反应条件为：温度，650～850℃，催化剂质量空速，2．68～10．72h^-1。在催化反应器出口，H2体积平均含量超过50％，CH4含量降低50％左右，C2组分降低到1％以下。在实验条件范围内，最高气体产率可以达到3．31Nm^3／kg biomass，最高氢产率可达到130．28g H2／kg biomass，对镍基催化剂350min的寿命测试表明，该系统具有较稳定的操作性能。     

梨木炭蒸汽气化制取富氢燃气的试验研究

生物质气化技术已得到广泛的应用,但气化过程产生的焦油会影响设备稳定运行。为了大幅减少焦油的干扰,以梨木的热解炭为原料,在管式炉中进行水蒸气气化制取富氢燃气试验研究,探究了反应温度、K₂CO₃添加量及利用次数对气化特性的影响。结果表明：900℃时H₂的产气量为2.19 L/g,合成气中H₂含量超过58%;K₂CO₃添加量为10%时产气效果最佳,此时合成气中H₂+CO含量达到了88.5%。当K₂CO₃催化剂在第三次利用时,仍有较好的催化效果。     

生物质流化床气化制取富氢燃气的研究

以流化床为反应器，对生物质空气-水蒸汽气化制取富氢燃气的特性进行了一系列实验研究。在本实验中，气化介质(空气)从流化床底部进人反应器，水蒸汽从进料点上方通人反应器。在对实验数据进行分析的基础上，探讨了一些主要参数如：反应器温度，水蒸汽／生物质比率S／B(Steam／Biomass Ratio)，当量比ER(Equivalence Ratio)以及生物质粒度对气体成分和氢产率的影响。结果表明：较高的反应器温度，适当的ER和S／B(在本实验研究中分别为0．23，2．02)，以及较小的生物质颗粒比较有利于氢的产出。最高的氢产率：71gH2／kgbiomass是在反应器温度为900℃，ER为0．22，S／B为2．70的条件下取得的。     

生物质水蒸气气化制氢模拟研究

利用ASPEN PLUS软件建立了生物质水蒸气气化制氢模型,对各种影响因素进行了深入分析。结果表明:随着碳转化率的增加,H2浓度略有降低,H2产量大幅增加,在碳转化率为1时达到最大值142.54 g/kg;随着水蒸气/生物质质量比的增加,H2浓度和产量大幅增加,而后趋于稳定,水蒸气/生物质质量比取2比较适宜。适当的升温和低压对制备H2有利,在加压条件下,H2浓度与产量达到最大值的温度升高。     

Comparison of thermochemical conversion processes of biomass to hydrogen-rich gas mixtures

Hydrogen can be produced from biomass materials via thermochemical conversion processes such as pyrolysis, gasification, steam gasification, steam-reforming, and supercritical water gasification (SCWG) of biomass. In general, the total hydrogen-rich gaseous products increased with increasing pyrolysis temperature for the biomass sample. The aim of gasification is to obtain a synthesis gas (bio-syngas) including mainly H₂ and CO. Steam reforming is a method of producing hydrogen-rich gas from biomass. Hydrothermal gasification in supercritical water medium has become a promising technique to produce hydrogen from biomass with high efficiency. Hydrogen production by biomass gasification in the supercritical water (SCW) is a promising technology for utilizing wet biomass. The effect of initial moisture content of biomass on the yields of hydrogen is good.     

Hydrogen and syngas production from sewage sludge via steam gasification

High temperature steam gasification is an attractive alternative technology which can allow one to obtain high percentage of hydrogen in the syngas from low-grade fuels. Gasification is considered a clean technology for energy conversion without environmental impact using biomass and solid wastes as feedstock. Sewage sludge is considered a renewable fuel because it is sustainable and has good potential for energy recovery. In this investigation, sewage sludge samples were gasified at various temperatures to determine the evolutionary behavior of syngas characteristics and other properties of the syngas produced. The syngas characteristics were evaluated in terms of syngas yield, hydrogen production, syngas chemical analysis, and efficiency of energy conversion. In addition to gasification experiments, pyrolysis experiments were conducted for evaluating the performance of gasification over pyrolysis. The increase in reactor temperature resulted in increased generation of hydrogen. Hydrogen yield at 1000 °C was found to be 0.076 g_gas g_sample⁻¹. Steam as the gasifying agent increased the hydrogen yield three times as compared to air gasification. Sewage sludge gasification results were compared with other samples, such as, paper, food wastes and plastics. The time duration for sewage sludge gasification was longer as compared to other samples. On the other hand sewage sludge yielded more hydrogen than that from paper and food wastes.     

水蒸气氛围下甘蔗渣热解气化条件的研究

在试验条件下，考察反应温度、升温速率、物料颗粒大小等因素对蔗渣在水蒸气中的热解气化特性的影响。试验结果表明，热解终温越高，物料粒径越小，越有利于产生高质量的热解气。热解终温是热解气化过程主要的决定因素，在先到达热解终温，再通入水蒸气的操作条件下，升温速率的改变对气化效果的影响并不突出。试验在最佳条件(采用粉末物料，在1000℃下进行热解)下，可以得到高热值(10MJ／m^3)合成气和较高的产气率(1．7m^3／kg)。     

Catalytic steam gasification of Mengdong coal in the presence of iron ore for hydrogen-rich gas production

Hydrogen-rich gas production from catalytic steam gasification of coal was investigated in the presence of iron ore in a vertical fixed bed reactor. The addition of iron ore significantly promoted the H₂ yields. The effects of operation parameters (upper zone temperature, lower zone temperature, steam concentration, and iron to coal ratio) on the yield of selected gaseous products (H₂ and CO) during catalytic steam gasification, were studied using Taguchi method. The results of signal-to-noise ratio indicated that steam concentration and iron to coal ratio were the most important parameters in determining the yield of H₂ and CO, respectively. Semi-quantification X-ray diffraction analysis of iron ores indicated that increase in steam concentration intensified the oxidization of low valence iron compounds to Fe₃O₄. In addition, formation of Fe₃O₄ was also favored with increasing reaction temperatures (600 °C–900 °C). However, the formation of Fe₃O₄ was inhibited at higher reaction temperature (1000 °C) due to the destruction of porous structures of the iron ore.     

Pyrolysis and steam gasification of methane fermentation residue produced from food waste

Pyrolysis and steam gasification of methane fermentation residue (MFR) produced from food waste (FW) were performed at two different heating rates. Moreover, unfermented FW and active sludge (AS) were tested. The results of slow heating experiments showed that although MFR contains biologically refractory organic matter, its overall thermal decomposition and gas evolution behaviors were similar to those of AS and, especially, FW. Furthermore, rapid heating experiments demonstrated that total gas yield and gas composition were similar for all three samples at 700°C. However, the effect of an increase in gasification temperature was more significant for MFR.     

Experimental study on biomass steam gasification for hydrogen-rich gas in double-bed reactor

Based on Response Surface Methodology, the experiments of biomass catalytic gasification designed by Design-Expert software were carried out in steam atmosphere and double-bed reactor. The response surface was set up with three parameters (gasification temperature, the content of K-based catalyst in gasification bed and the content of Ni-based catalyst in reforming bed) for biomass gasification performance of carbon conversion efficiency and hydrogen yield to make analysis and optimization about the reaction characteristics and gasification conditions. Results showed that gasification temperature and the content of K-based catalyst in gasification bed had significant influence on carbon conversion efficiency and hydrogen yield, whilst the content of Ni-based catalyst in reforming bed affected the gasification reactions to a large extent. Furthermore, appropriate conditions of biomass steam gasification were 800 °C for gasification temperature, 82% for the content of K-based catalyst in gasification bed and 74% for the content of Ni-based catalyst in reforming bed by the optimization model. In these conditions, the steam gasification experiments using wheat straw showed that carbon conversion efficiency was 96.9% while hydrogen yield reached 64.5 mol/kg, which was in good agreement with the model prediction. The role of the reforming bed was also analyzed and evaluated, which provided important insight that the employment of reforming bed made carbon conversion efficiency raised by 4.8%, while hydrogen yield achieved a relative growth of 50.5%.     

Thermodynamic analysis of hydrogen-rich gas generation from coal/steam gasification using blast furnace slag as heat carrier

Thermodynamic analysis with Gibbs free energy minimization through Lagrange multiplier method was performed for coal gasification with steam using blast furnace (BF) slag as heat carrier and recycling its waste heat to produce hydrogen-rich gas (HRG). Simulations were carried out to study the operation temperature, pressure, S/C and BF slag basicity based on chemical equilibrium calculations. The optimal thermodynamic conditions were determined to improve hydrogen concentration and total syngas production as high as possible. The results suggested that the preferential conditions for HRG from Datong coal were achieved at 775 °C, atmospheric pressure and S/C of 2.0–3.0. Under these conditions, hydrogen concentration reached to 62.36% and the total gas production was 2.45 mol per mole of carbon in the coal. What's more, not only was the quality of HRG improved significantly, but also the BF slag waste heat was recycled effectively when using BF slag as heat carrier. The effect of BF slag basicity upon the gasification characteristics was also investigated, and the production of hydrogen increased significantly when basicity was 1.3.     

High temperature steam gasification of wastewater sludge

High temperature steam gasification is one of the most promising, viable, effective and efficient technology for clean conversion of wastes to energy with minimal or negligible environmental impact. Gasification can add value by transforming the waste to low or medium heating value fuel which can be used as a source of clean energy or co-fired with other fuels in current power systems. Wastewater sludge is a good source of sustainable fuel after fuel reforming with steam gasification. The use of steam is shown to provide value added characteristics to the sewage sludge with increased hydrogen content as well total energy. Results obtained on the syngas properties from sewage sludge are presented here at various steam to carbon ratios at a reactor temperature of 1173 K. Effect of steam to carbon ratio on syngas properties are evaluated with specific focus on the amounts of syngas yield, syngas composition, hydrogen yield, energy yield, and apparent thermal efficiency. The apparent thermal efficiency is similar to cold gas efficiency used in industry and was determined from the ratio of energy in syngas to energy in the solid sewage sludge feedstock. A laboratory scale semi-batch type gasifier was used to determine the evolutionary behavior of the syngas properties using calibrated experiments and diagnostic facilities. Results showed an optimum steam to carbon ratio of 5.62 for the range of conditions examined here for syngas yield, hydrogen yield, energy yield and energy ratio of syngas to sewage sludge fuel. The results show that steam gasification provided 25% increase in energy yield as compared to pyrolysis at the same temperature.     

Production of hydrogen-rich gas from plant biomass by catalytic pyrolysis at low temperature

The catalytic pyrolysis of plant biomass was investigated in a dual-particle powder fluidized-bed (PPFB), where the primary decompositions and secondary reactions occurred simultaneously under ambient pressure. The yields and distributions of the pyrolysis products were studied under various operating conditions. In the absence of catalyst, the amount of volatile released from woody biomass depended on the pyrolysis temperature, and only 13.8 g H₂/kg biomass (def: dry ash-free basis) was produced at 1173 K. NiMo/Al₂O₃ catalyst promoted the decomposition of tar and light aromatic hydrocarbon compounds from the primary decomposition reaction, and significantly reduced the temperature required for the secondary phase reaction. With NiMo/Al₂O₃ catalyst at 723 K, clean combustion gas accounted for 91.25 vol% of the total gas products, which was composed of 49.73 vol% of H₂, 34.50 vol% of CO, and 7.03 vol% of low molecular weight hydrocarbon gases. The contents of H₂ and CO were 33.6 g H₂/kg biomass (def) and 326.3 g CO/kg biomass (def), respectively. Therefore, it is critical to control the secondary phase reaction conditions during the catalytic pyrolysis in order to produce hydrogen-rich gas.     

Hydrogen-rich gas from catalytic steam gasification of biomass in a fixed bed reactor: Influence of temperature and steam on gasification performance

The catalytic steam gasification of biomass was carried out in a lab-scale fixed bed reactor in order to evaluate the effects of temperatures and the ratio of steam to biomass (S/B) on the gasification performance. The bed temperature was varied from 600 to 900 and the S/B from 0 to 2.80. The results show that higher temperature contributes to more hydrogen production.