整体式焦油裂解催化剂的制备及性能研究

以堇青石为载体,采用真空浸渍法制备整体式镍基催化剂,研究了不同干燥方法对整体式催化剂内表面活性组分轴向分布的影响及不同工艺条件下的催化性能。结果表明:微波干燥法所得催化剂内表面活性组分轴向分布最均匀;重时空速对焦油裂解率的影响较大,当重时空速为177kg/(h.m3)时,焦油裂解率高达92.62%,H2的体积分数为46.53%;在较低温度条件(700~800℃)下,催化温度对焦油裂解的影响较小,当催化温度上升到900℃时,焦油裂解率大幅上升,单位质量生物质气体产率高达1.22Nm3/kg。     

CaO催化裂解生物质气化焦油实验研究

以谷壳气化发电产生焦油为研究对象,考查了CaO作为焦油裂解催化剂对其催化裂解的影响。实验研究结果表明:CaO作为焦油裂解催化剂可使焦油裂解率明显提高,在800℃时,其裂解率可由热裂解的28.66%提高到65.60%,焦油催化裂解后可使燃气成份中的H2、CO、CH4以及CO2含量提高。但焦油裂解过程中,其积炭率可达30.51%;扫描电镜显示:因焦油裂解积炭包裹CaO催化剂,易使其催化活性失效,同时由于积炭,使床层压降增加,给焦油催化裂解运行带来困难。     

生物质气化焦油催化裂解特性

以白云石为载体制备的Ni基催化剂对松木粉在700℃下气化产生的焦油进行了催化裂解实验研究，并与重油裂解催化剂进行了对比。结果表明：石油化工重油裂解催化剂对生物质气化焦油具有一定的催化裂解作用；Ni的掺入方式和催化剂的煅烧温度对催化剂的性能具有显著的影响。以100～120目白云石粉为载体，900℃下煅烧的Ni基催化剂在700℃(2下焦油裂解对H2和CH4具有很好的选择性(H2为78．3％，H2 CO为92．3％，CH4为2．3％)；100h老化实验显示H2/CO随催化剂活性降低而逐渐减小。     

生物质炭催化裂解焦油的性能研究

采用管式反应器研究了生物质炭作为焦油裂解催化剂的性能,选用白云石和石英砂作对比试验。通过对焦油转换率、裂解产物、裂解气气体组分和动力学参数的分析对比可知:在所选用的3种材料中,生物质炭作为催化剂的焦油转化率最高,裂解产物中气体所占比重最大,且可燃气体的组分较高,反应动力学参数最小。生物质炭的催化性能显著高于石英砂,稍好于白云石,是一种高效的焦油裂解催化剂。     

凹凸棒石粘土催化裂解生物质气化炉焦油初探

研究了凹凸棒石粘土对稻壳气化焦油的催化裂解性能,分析了不同温度和不同凹凸棒石粘土/白云石比值下催化剂催化脱焦油活性.结果表明:随着催化裂解温度增加,各种催化剂对生物质气化炉焦油的去除率均有不同程度的提高,且随凹凸棒石粘土/白云石比值的增加,焦油的去除率有所增加.凹凸棒石粘土与白云石之间存在协同作用,这种协同作用提高了焦油催化裂解活性.与其他几种常用的矿物材料催化剂(氧化钙、橄榄石、辉沸石)相比,尽管凹凸棒石粘土催化裂解焦油后积炭量最大,但还是显示出对焦油裂解反应最好的催化活性.     

助剂改性Ru-Ni-CeO2/HZSM-5催化剂裂解秸秆气化焦油性能研究

用助剂Fe、Mn、Co以及Cu调变浸渍法制备Ru-Ni-CeO2/HZSM-5催化剂,并对催化裂解秸秆气化焦油的活性和选择性进行研究。结果表明,助剂影响焦油裂解的活性和选择性,Cu对提高Ni-Ru-CeO2/HZSM-5催化剂焦油裂解活性和燃气质量具有最佳效果。     

凹凸棒石黏土催化裂解生物质焦油

以凹凸棒石黏土作为天然催化剂催化裂解生物质气化焦油,在固定床反应器中,考察催化剂用量、粒径、煅烧温度、气相滞留时间以及反应温度等操作条件对凹凸棒石黏土催化焦油裂解活性的影响;通过XRD表征分析了催化剂的结构变化情况。与热裂解相比,凹凸棒石黏土对生物质焦油有显著的催化裂解作用。随着裂解温度的升高,焦油转化率、氢产率及氢选择性都显著增加。凹凸棒石黏土的煅烧处理能够改善催化活性,但过高的煅烧温度将破坏凹凸棒石黏土的特征结构,从而不利于其催化效率。     

催化剂粒径与质量对生物质热解焦油催化裂化反应的影响

针对催化裂化条件对生物质热解焦油处理的影响,以秸秆热解产生的焦油为原料,在固定床焦油催化裂化反应试验台上研究了催化剂作用下焦油催化裂化的过程,并对催化剂粒径和质量等参数对焦油转化效果和催化裂化产物的影响进行了分析．结果表明：减小催化剂的粒径或者增加催化剂质量能促进燃气中高热值大分子气体转化为低热值的小分子轻质气体,从而有效促进焦油裂化,提高燃气产率,降低燃气热值．     

焦炭对焦油模型化合物的催化裂解实验研究

研究焦炭对焦油模型化合物的催化裂解。考察焦炭对甲苯、甲苯与萘、甲苯与苯酚的催化裂解率及析炭率。结果表明:焦炭对甲苯的催化裂解率与同温度下的热裂解率相当,分别为61.68%与59.02%,析炭率有所降低,由8.54%变为4.16%;对萘的催化裂解率也与同温度下的热裂解率相当,分别为57.95%与56.20%,析炭率也有所降低,由20.72%变为11.89%;而焦炭对苯酚的裂解率与同温度下热裂解率相比有明显增加,由38.25%增加到97.41%,析炭率同样有所降低,由10.96%变为7.03%;说明焦炭对焦油中的组分有选择催化裂解作用。对上述反应前后焦炭样的XRD分析,发现反应后析出的炭与作为催化剂的炭是同一晶型的炭,对末裂解冷凝液的GC-MS分析,发现焦油模型化合物通过裂解后有少部分向芳香化程度增加的方向进行转化。     

1MW木粉气化发电系统的运行特性分析

通过对海南三亚木粉发电系统的运行状况分析，结果发现：气化过程中所夹带的飞灰以及所生成的焦油是影响发电系统正常运行的主要因素，显热损失和飞灰中没有完全气化的碳损失是导致气化发电系统效率下降的主要原因。同时考查了气化过程中污染物排放情况及添加焦油裂解催化剂对气体成份和焦油裂解的影响，对改进今后生物质气化发电系统的大型化设计具有一定的指导意义。     

生物质焦油的特性及其净化研究现状

通过分析生物质热解气化过程中焦油的特性和生成机制,以及净化方法研究现状,了解焦油的主要组成和基本特性参数,发现焦油随着反应温度的升高,逐步经过裂解、聚合、缩合反应生成多环芳香烃。而焦油的脱除应当根据不同的生物质气化反应特性,多种方法结合,以减少催化剂损失、提高焦油脱除率和转化率。     

生物质气化气中焦油非催化裂解实验研究

生物质气化是一种环境友好的新能源利用技术,焦油作为生物质气化的副产物,是限制气化技术发展的主要因素.试验针对生物质气化产出气中焦油在700～1 000℃裂解温度区间的裂解特性进行了分析,并提出了焦油裂解产气率的概念.试验表明,焦油裂解气可以成为生物质气化气的有效的能量补充,而且随着裂解温度的升高,焦油裂解产气率增加,焦...     

Catalytic steam reforming of tar for enhancing hydrogen production from biomass gasification: a review

Presently, the global search for alternative renewable energy sources is rising due to the depletion of fossil fuel and rising greenhouse gas (GHG) emissions. Among alternatives, hydrogen (H₂) produced from biomass gasification is considered a green energy sector, due to its environmentally friendly, sustainable, and renewable characteristics. However, tar formation along with syngas is a severe impediment to biomass conversion efficiency, which results in process-related problems. Typically, tar consists of various hydrocarbons (HCs), which are also sources for syngas. Hence, catalytic steam reforming is an effective technique to address tar formation and improve H₂ production from biomass gasification. Of the various classes in existence, supported metal catalysts are considered the most promising. This paper focuses on the current researching status, prospects, and challenges of steam reforming of gasified biomass tar. Besides, it includes recent developments in tar compositional analysis, supported metal catalysts, along with the reactions and process conditions for catalytic steam reforming. Moreover, it discusses alternatives such as dry and autothermal reforming of tar.     

Numerical simulation on biomass-pyrolysis and thermal cracking of condensable volatile component

We studied the physical and chemical properties of the condensable volatiles of biomass pyrolysis products. We redefine the liquid product and divide the condensable volatiles into two categories, biomass oil and tar, the latter of which comes from the secondary pyrolysis or cracking reaction of the former. We further establish a kinetic model of biomass pyrolysis and secondary cracking. The chemical reaction kinetics equation and heat transfer equation are coupled to simulate the biomass pyrolysis process. For biomass solid particles, the model not only considers the initial reaction of biomass and secondary cleavage reaction of condensable gas, but also introduces a reaction mode in which biomass oil is converted into tar. When the pyrolysis temperature is below 500 °C, the pyrolysis products are essentially biomass oil. However, when the pyrolysis temperature exceeds 500 °C, the biomass oil gradually converts into tar. The model also considers characteristics of the reaction medium (porosity, intrinsic permeability, thermal conductivity) and the unsteady gas phase process based on Darcy's law of velocity and pressure, heat convection, diffusion, and radiation transfer. We analyze the relationships among the internal temperature of the particles, particle size and position, mass fraction of the reactants and products, the gas mixture, the production share of tar and biomass oil, and the relationship between gas pressure and time. The results show that the effects of the secondary cracking reaction and internal convective flow in the biomass pyrolysis process are coupled because the flow field in the porous medium determines the volatile residence time and thus species that affect the secondary cracking reaction. The rate of volatile formation in the initial and secondary cracking reactions affects the pressure gradient and gas diffusion. Additionally, the endothermic effect influences the temperature field of the pyrolysis reaction but has no apparent effect on small particles whose chemical reaction is the control mechanism. For large particles, heat transfer inside the particles is the diffusion control mechanism and the chemical reaction on the particle surface is the speed control mechanism. Two peaks are observed in the pyrolysis gas mass proportion curve, which result from the consumption of biomass oil and tar as they flow toward hot surfaces. The first peak is the decomposition of biomass oil into non-condensable volatile matter and tar, and the second peak is the further cracking of tar into gas and coke at high temperature.     

One-step synthesis of biochar-supported potassium-iron catalyst for catalytic cracking of biomass pyrolysis tar

In this work, K–Fe bimetallic catalyst supported on porous biomass char was synthesized via a one-step synthesis method by pyrolysis of biomass (peanut shells) after impregnation of a small amount of potassium ferrate (PSC–K₂FeO₄), and was evaluated for the cracking of biomass pyrolysis tar. Control experiments using the pure char (PSC) and char-supported catalysts after impregnation of KOH (PSC–KOH) and FeCl₃ (PSC–FeCl₃) were also performed for comparison. The as-prepared PSC-K₂FeO₄ possessed a porous structure with the dispersion of particles/clusters of Fe metal, K₂CO₃ and KFeO₂ on the char support. Tar cracking experiments showed that the PSC-K₂FeO₄ exhibited excellent catalytic activity on the cracking of biomass pyrolysis tar in the temperature range of 600–800 °C, and the obtained tar conversion efficiencies were obviously higher than that in the control experiments, particularly at relatively lower temperatures (600 and 700 °C). The yields of combustible gas compounds including CO, H₂ and CH₄ increased significantly using PSC-K₂FeO₄ as the catalyst due to the enhanced tar cracking and reforming reactions. The porous structure and the active crystal structures of the spent catalyst were well retained, indicating the potential for efficient and long-term utilization of the catalyst in tar cracking. PSC-K₂FeO₄ exhibited excellent reusability during the five times reuse under the same conditions without regeneration, which showed almost no obvious decrease in the tar conversion efficiency and gas yields.     

生物质气化发电燃气焦油脱除方法的探讨

生物质气化发电技术的最大难点之一就是如何除去燃气中含有的焦油等污染物,这些成分会对燃气轮机或内燃机等设备造成一定的影响.因此生物质气化发电过程中燃气焦油的脱除是目前国内外重点研究和解决的课题之一.文章在研究国内外大量有关文献资料的基础上,深入阐述了气化过程中焦油产生的机理、影响焦油生成的因素以及焦油的脱除方法,重点探讨了目前较为有效的焦油热化学脱除方法,即焦油的热裂解和催化裂解方法,以期为生物质气化发电燃气焦油的脱除提供一些思路和参考.     

Biomass thermochemical conversion: A review on tar elimination from biomass catalytic gasification

Biomass is promising renewable energy because of the possibility of value-added fuels production from biomass thermochemical conversion. Among the thermochemical conversion technology, gasification could produce the H₂-rich syngas then into value-added chemicals via F-T (Fischer-Tropsch) synthesis. However, a variety of difficulties, such as tar formation, reactors impediment, complex tar cracked mechanism, etc. make it difficult to develop for further application. This paper sheds light on the developments of biomass thermochemical conversion, tar classifications, tar formation, and elimination methods. Secondly, we provide a comprehensive the state-of-the-art technologies for tar elimination, and we introduce some advanced high activity catalysts. Furthermore, many represent tar models were employed for explanation of the tar-cracked pathway, and real tar-cracked mechanism was proposed. Following this, some operational conditions and effective gasified models were concluded to give an instruction for biomass catalytic gasification.     

Preparation of high-activity coal char-based catalysts from high metals containing coal gangue and lignite for catalytic decomposition of biomass tar

The potential of using high metals containing coal gangue and lignite to prepare high-activity coal char-based catalysts is investigated for effective biomass tar decomposition. Loose structure and rough surface are formed for these char-based catalysts with heterogeneous distribution of a large number of inorganic particles. In the biomass tar decomposition, the performance of the coal char-based catalysts is significantly influenced by the content of the metals in the raw materials and coal gangue char (GC) with the ash content as high as 50.80% exhibits the highest activity in this work. A high biomass tar conversion efficiency of 93.5% is achieved at 800 °C along with a significant increase in the fuel gas product. During the five-time consecutive tests, the catalytic performance of GC increases a little at the second or third times reuse and remains relatively stable, showing the remarkable stability of the catalyst in biomass tar decomposition applications.     

The steam reforming of naphthalene over a nickel–dolomite cracking catalyst

With naphthalene as a model compound, catalytic cracking experiments on biomass tar were made on Ni–dolomite catalysts. The performance of catalyst preparation, activity, coke formation and regeneration were analysed. The results showed that the ratio of the one-step conversion of naphthalene was 95% at space velocity 0.81 h⁻¹ and 700 °C; with saturated wet air as regeneration gas, the regeneration time was within 0.5 h; compared with thermal cracking at the same reaction temperature, the catalytic cracking was propitious to deep cracking of naphthalene.     

流光电晕放电净化粗燃气焦油及粉尘研究进展

研究焦油及粉尘的高效净化方法对推动生物质气化技术的发展具有重要意义。流光电晕放电过程产生的O、H、OH等活性自由基可有效裂解燃气中的焦油类有机物分子,在直流基压上叠加窄脉冲电压则可实现粉尘的荷电及高效气-固分离,是一种较有应用前景的粗燃气净化方法。笔者对流光电晕放电净化粗燃气焦油及粉尘的技术进展进行了综述,分析了该过程的裂解焦油/除尘机理、研究现状及关键科学问题,并提出了一种基于电旋风等离子体反应器的焦油及粉尘同时净化方法。最后针对生物质气化粗燃气净化过程中的瓶颈问题,简要归纳了其研究重点。