生物质超临界水部分氧化气化的能量过程分析(英文)

Partial oxidation gasification in supercritical water could produce fuel gases (such as H2, CO and CH4) and signif-icantly reduce the energy consumption. In this work, an energetic model was developed to analyze the partial oxidative gasification of biomass (glucose and lignin) in supercritical water and the related key factors on which gasification under autothermal condition depended upon. The results indicated that the oxidant equiva-lent ratio (ER) should be over 0.3 as the concern about energy balance but less than 0.6 as the concern about fuel gas production. Feedstocks such as glucose and lignin also had different energy recovery efficiency. For ma-terials which can be efficiently gasified, the partial oxidation might be a way for energy based on the combustion of fuel gases. Aromatic materials such as lignin and coal are more potential since partial oxidation could produce similar amount of fuel gases as direct gasification and offer additional energy. Energy recovered pays a key role to achieve an autothermal process. Keeping heat exchanger efficiency above 80%and heat transfer coefficient below 15 kJ·s?1 is necessary to maintain the autothermal status. The results also indicated that the biomass loading should be above 15%but under 20%for an autothermal gasification, since the increase of biomass loading could improve the energy supplied but decrease the efficiency of gasification and gaseous yields. In general, some specific conditions exist among different materials.     

Thermoneutral tri-reforming of flue gases from coal- and gas-fired power stations

The treatment of flue gases from fossil fuel fired power stations by tri-reforming with natural gas or by coal gasification could become an attractive approach for converting the CO₂, H₂O, O₂, and N₂ contained in these flue gases via syngas processing into useful products, such as methanol, hydrogen, ammonia, or urea. The present study determines the constraints for achieving such thermochemical reactions under conditions of thermoneutrality, by reacting the flue gases with water, air, and natural gas or coal at 1000–1200 K. The implications of such reactions are examined in terms of CO₂ emission avoidance, fuel saving, economic viability, and exergy efficiency.     

Investigation of Catalytic Pathways and Separations for Lignin Breakdown into Monomers and Fuels

Lignin is primarily burned for heat and power in industrial processes, but its aromaticity and high energy content make it a promising source for liquid fuels, fuel additives, and chemical feedstocks. Conversion of lignin to monomers and smaller molecules can be done thermochemically through gasification; however, this process does not produce the desired fraction of liquid products, mainly yielding gases and char. In addition, such processing of lignin on a larger scale may encounter barriers, namely difficulty achieving selectivity of the conversion reactions and extensive requirements for separations, both before and after treatment of the material. A low temperature conversion of lignin may achieve better thermodynamic efficiency, provided a target catalyst can be used to generate a significant conversion of product. This project includes discussion of

? the experimental evaluation of a number of different low temperature (20–30°C) catalytic pathways for the decompo sition of lignin into small molecules, and

? the evaluation of flowsheets for lignin conversion in terms of thermodynamic efficiency, separation requirements, and technical feasibility.     

Treatment of biomass tar by CO2 plasma

The tar produced in the process of biomass gasification would not only corrode the pipelines and equipment, but also reduce the efficiency of biomass gasification. Traditional methods, such as physical treatment and thermal cracking, have deficiencies which severely restrict their application. This article achieved efficient transformation (carbon yield >90%) from benzene and naphthalene, regarded as model compounds of biomass tar, to syngas using CO₂ plasma on self-designed rotating arc plasma torch, proving the feasibility of CO₂ plasma treatment of biomass tar. Further analysis on the composition of practical biomass tar and the investigation of biomass tar gasification were carried out. Water content in biomass tar could be used as gasification agent and control the H₂/CO scale (0.3—1). The above results provide new ideas for the development of biomass tar harmlessness and resource utilization technology.     

二氧化碳等离子体处理生物质焦油

生物质气化过程中副产的焦油不仅有腐蚀设备、堵塞管道等危害,而且会降低生物质气化效率,传统的物理处理与热裂解处理方法存在诸多不足。本文基于旋转弧热等离子体反应装置,以二氧化碳作为等离子介质,选取苯及苯萘混合物作为生物质焦油的模型化合物进行了气化实验,实现了向合成气的高效转化（碳收率可达到90%以上）,初步显示了该路线的可行性。进一步分析了真实生物质焦油的物质组成,考察了二氧化碳等离子体对焦油的气化性能,焦油内的水分可作为气化剂,调节合成气中H₂/CO的比例（0.3~1）。上述结果为生物质焦油无害化、资源化利用技术的发展提供了新的思路。     

生物质两段式富氧气化-燃气轮机燃烧集成发电系统模拟研究

为实现生物质能量的高效清洁利用,本研究基于两段式富氧气化系统改进燃气品质,并将获得的洁净高热值可燃气用于燃气轮机燃烧.通过Aspen Plus模拟研究分析了氧体积分数、气化温度对气化特性、燃机运行特性的影响,研究结果证实了生物质气化燃气在燃气轮机应用的可行性,并发现氧体积分数提高对改善生物质气化燃气品质及系统发电效率具...     

High-efficiency and pollution-controlling in-situ gasification chemical looping combustion system by using CO2 instead of steam as gasification agent

Using CO₂ as gasification agent instead of steam in in-situ coal gasification chemical looping combustion (iG-CLC) power plant can eliminate energy consumption for steam generation, thus obtaining higher system efficiency. In this work, a comparative study of iG-CLC power plant using steam and CO₂ as gasification agent is concentrated on. The effects of steam to carbon ratio (S/C) and CO₂ to carbon ratio (CO₂/C) on the fuel reactor temperature, char conversion, syngas composition and CO₂ capture efficiency are separately investigated. An equilibrium carbon conversion of 88.9% is achieved in steam-based case as S/C ratio increases from 0.7 to 1.1, whereas a maximum conversion of 84.2% is obtained in CO₂-based case with CO₂/C ranging from 0.7 to 1.1. Furthermore the effects of oxygen carrier to fuel ratio (φ) on system performances are investigated. Increasing φ from 1.0 to 1.4 helps to achieve char conversion from 75.9% to 88.9% in steam-based case, by contrast the char conversion can achieve 66.3%-84.2% in CO₂-based case within the same φ range. In terms of iG-CLC power plant, recycling partial CO₂ to the fuel reactor improves the overall performance. Approximately 3.9% of net power efficiency are increased in CO₂-based plant, from steam-based plant. Higher CO₂ capture efficiency and lower CO₂ emission rate are observed in CO₂-gasified iG-CLC power plant, expecting to be 90.63% and 85.18 kg·MW^-1·h^-1, respectively.     

Performance analysis of integrated biomass gasification fuel cell (BGFC) and biomass gasification combined cycle (BGCC) systems

Biomass gasification processes are more commonly integrated to gas turbine based combined heat and power (CHP) generation systems. However, efficiency can be greatly enhanced by the use of more advanced power generation technology such as solid oxide fuel cells (SOFC). The key objective of this work is to develop systematic site-wide process integration strategies, based on detailed process simulation in Aspen Plus, in view to improve heat recovery including waste heat, energy efficiency and cleaner operation, of biomass gasification fuel cell (BGFC) systems. The BGFC system considers integration of the exhaust gas as a source of steam and unreacted fuel from the SOFC to the steam gasifier, utilising biomass volatilised gases and tars, which is separately carried out from the combustion of the remaining char of the biomass in the presence of depleted air from the SOFC. The high grade process heat is utilised into direct heating of the process streams, e.g. heating of the syngas feed to the SOFC after cooling, condensation and ultra-cleaning with the Rectisol^® process, using the hot product gas from the steam gasifier and heating of air to the SOFC using exhaust gas from the char combustor. The medium to low grade process heat is extracted into excess steam and hot water generation from the BGFC site. This study presents a comprehensive comparison of energetic and emission performances between BGFC and biomass gasification combined cycle (BGCC) systems, based on a 4th generation biomass waste resource, straws. The former integrated system provides as much as twice the power, than the latter. Furthermore, the performance of the integrated BGFC system is thoroughly analysed for a range of power generations, ～100–997 kW. Increasing power generation from a BGFC system decreases its power generation efficiency (69–63%), while increasing CHP generation efficiency (80–85%).     

直接利用生物质的化学燃料电池研究进展

近些年燃料电池技术有了长足的发展,利用燃料电池处理废弃生物质并产电是一种新型途径,可以达到废物处理、能源回收的目的。然而,受限于燃料种类、电池性能、产物分离等因素,传统的燃料电池难以直接用于处理废弃生物质。本文首先针对中低温燃料电池如碱性燃料电池、质子交换膜燃料电池的研究现状进行了综述,结果表明,碱性燃料电池在以小分子有机物作为燃料时性能良好,但是容易受到产物CO₂酸化影响;液相催化燃料电池在催化剂耐受性、生物质处理、电池功率密度等方面表现出优异的性能。然后介绍了电催化剂如过渡金属氧化物、多酸等研究现状,此类催化剂具有较强的氧化性、布朗斯特酸性和路易斯酸性等,具有很强的催化分解生物质的能力,针对液相催化剂不易分离的局限,介绍了催化剂固载化、纳米复合材料等研究进展。之后介绍了电极材料和膜材料的研究进展,碳极板因其综合性能和成本成为当前的主流选择,全氟磺酸膜性能优异,成为实验探究应用的理想材料,同时对一些复合材料的研究现状进行了简要介绍。最后,对化学燃料电池应用于生物质处理的方向进行了展望,液相催化燃料电池综合性能突出,在可处理生物质种类、催化剂循环等问题进一步优化之后,有望成为一种废弃生物质处理的新途径。     

制氢技术现状及展望

矿物燃料制氢是主要的制氢方法，其中以天然气蒸汽转化制氢的成本最低。重油部分氧化和煤气化曾经是制氢的重要方法，由于生产成本较高其发展有所减缓。这三种制氢过程制得合成气后还要经过变换完成进一步制氢，最后脱除CO2得到较纯的氢气，过程复杂。随着燃料电池的商业化进程的日益加快，低成本的、不含或少含CO的制氢技术受到广泛关注，其中铁蒸汽法和甲烷催化裂解法制得的氢气不含CO和CO2，过程得到简化。显然，矿物燃料制氢要向大气排放大量的温室气体，对环境不利。水电解制氢是较理想的制氢方法，不产生温室气体，但生产成本较高。因此水电解制氢适合电力资源如水电、风能、地热能、潮汐能以及核能比较丰富的地区。其他制氢技术如热化学制氢、太阳能制氢、生物质制氢以及等离子体制氢也在开发之中，相信是矿物燃料制氢与水电解制氢的有效补充。     

Effect of biomass particle size and air superficial velocity on the gasification process in a downdraft fixed bed gasifier. An experimental and modelling study

A one-dimensional stationary model of biomass gasification in a fixed bed downdraft gasifier is presented in this paper. The model is based on the mass and energy conservation equations and includes the energy exchange between solid and gaseous phases, and the heat transfer by radiation from the solid particles. Different gasification sub-processes are incorporated: biomass drying, pyrolysis, oxidation of char and volatile matter, chemical reduction of H₂, CO₂ and H₂O by char, and hydrocarbon reforming. The model was validated experimentally in a small-scale gasifier by comparing the experimental temperature fields, biomass burning rates and fuel/air equivalence ratios with predicted results. A good agreement between experimental and estimated results was achieved. The model can be used as a tool to study the influence of process parameters, such as biomass particle mean diameter, air flow velocity, gasifier geometry, composition and inlet temperature of the gasifying agent and biomass type, on the process propagation velocity (flame front velocity) and its efficiency. The maximum efficiency was obtained with the smaller particle size and lower air velocity. It was a consequence of the higher fuel/air ratio in the gasifier and so the production of a gas with a higher calorific value.     

A novel biomass air gasification process for producing tar-free higher heating value fuel gas

Biomass is a promising sustainable energy source. A tar-free fuel gas can be obtained in a properly designed biomass gasification process. In the current study, a tar-free biomass gasification process by air was proposed. This concept was demonstrated on a lab-scale fluidized bed using sawdust under autothermic conditions. This lab-scale model gasifier combined two individual regions of pyrolysis, gasification, and combustion of biomass in one reactor, in which the primary air stream and the biomass feedstock were introduced into the gasifier from the bottom and the top of the gasifier respectively to prevent the biomass pyrolysis product from burning out. The biomass was initially pyrolyzed and the produced char was partially gasified in the upper reduction region of the reactor, and further, char residue was combusted at the bottom region of the reactor in an oxidization atmosphere. An assisting fuel gas and second air were injected into the upper region of the reactor to maintain elevated temperature. The tar in the flue gas entered the upper region of the reactor and was decomposed under the elevated temperature and certain residence time. This study indicated that under the optimum operating conditions, a fuel gas could be produced with a production rate of about 3.0 Nm³/kg biomass and heating value of about 5000 kJ/Nm³. The concentration of hydrogen, carbon monoxide and methane in the fuel gas produced were 9.27%, 9.25% and 4.21%, respectively. The tar formation could be efficiently controlled below 10 mg/Nm³. The system carbon conversion and cold gasification efficiency reached above 87.1% and 56.9%, respectively. In addition, the investigation of energy balance for the scale-up of the proposed biomass gasification process showed that the heat loss could be recovered by approximately 23% of total energy input. Thus, partial fuel gas that was produced could be re-circulated and used to meet need of energy input to maintain the elevated temperature at the upper region of reactor for tar decomposition. It was predicted the heating value of product fuel gas would be 8000 kJ/Nm³ if the system was scaled up.     

基于3kW塔式串行流化床差异燃料的化学链燃烧解析

化学链燃烧反应器具有广泛的燃料适应性，可同时兼顾气、液、固多类型燃料的运行。本文依托耦合内构件的3kW塔式串行流化床反应器，分别开展异丙醇、污泥以及煤炭的化学链燃烧实验，探究燃料物化属性对化学链燃烧过程与反应器运行的影响，揭示面向目标燃料的反应器针对性设计、载氧体性能选择与流化操作策略，助力形成指向性强、碳捕集效率高与操作灵活的化学链燃烧技术。面对碳化程度低、有机质含量高的固体燃料，焦炭气化速率已非强化重点，如污泥在3kW塔式反应器910℃与150s停留时间内，可实现大于99%的CO₂捕集效率，化学链燃烧反应器应侧重改善可燃气体转化与旋风分离器对轻质焦炭颗粒的捕捉。当采用异丙醇等高CH₄含量的燃料时，Fe基矿石载氧体的反应性能不足，3kW反应器的额外耗氧率高达10%～19%，其中未燃尽CH₄对额外耗氧率的贡献占比超80%。化学链燃烧反应器需依据热解反应气的物化特性，选择或掺混功能性载氧体，以针对性改善气固转化。在煤等高碳化燃料的化学链燃烧过程中，焦炭气化是反应的限制性步骤，简化循环结构的3kW塔式反应器停留时间不足，仅可...     

Electrolytic cell engineering and device optimization for electrosynthesis of e-biofuels via co-valorisation of bio-feedstocks and captured CO2

Utilizing CO₂ in an electro-chemical process and synthesizing value-added chemicals are amongst the few viable and scalable pathways in carbon capture and utilization technologies.CO₂ electro-reduction is also counted as one of the main options entailing less fossil fuel consumption and as a future electrical energy storage strategy.The current study aims at developing a new electrochemical platform to produce low-carbon e-biofuel through multifunctional electrosynthesis and integrated co-valorisation of biomass feedstocks with captured CO₂.In this approach,CO₂ is reduced at the cathode to produce drop-in fuels(e.g.,methanol)while value-added chemicals(e.g.,selective oxidation of alcohols,aldehydes,carboxylic acids and amines/amides)are produced at the anode.In this work,a numerical model of a continuous-flow design considering various anodic and cathodic reactions was built to determine the most techno-economically feasible configurations from the aspects of energy efficiency,environment impact and economical values.The reactor design was then optimized via parametric analysis.     

循环流化床气化温度对稻壳气化固相产物特性的影响

为解决燃煤机组耦合生物质气化发电过程中固相产物的妥善利用问题,以稻壳为原料,在襄阳电厂6#燃煤机组耦合生物质循环流化床上,考察了稻壳气化发电时气化温度对燃气组分以及固相产物的含碳量、比表面积、微观形貌和吸附能力的影响.结果 表明:燃气主要可燃成分CO和H2随温度升高先增大后减小,当温度为775℃时达到最高值,分别为18...     

用于甲烷-氮气体系分离的膜技术研究进展

天然气作为一种高效、清洁的化石能源,在我国能源转型中扮演着重要角色。部分常规和非常规天然气含有较高浓度的氮气,会降低天然气的热值,无法满足管道输送的要求[氮气含量小于4%(体积分数)]。因此,天然气脱氮对实现化石能源的高效利用具有重要意义。相比于传统的气体分离技术,膜分离技术具有操作弹性大、投资少、能耗低等优点,在能源和环境领域均展现出广阔的应用前景。介绍了甲烷-氮气分离膜的传递机理,从甲烷优先渗透膜、氮气优先渗透膜两方面综述了甲烷-氮气膜分离技术的研究进展,同时针对不同的应用场合(常规天然气、页岩气和煤层气)进行了膜过程模拟研究,结合应用实例展望了膜技术在甲烷-氮气分离领域的发展及应用前景。     

松木屑在氧气-水蒸气-二氧化碳氛围下的气化模拟研究

以氧气-水蒸气-二氧化碳作为气化介质,松木屑为原料,采用Aspen Plus软件,结合自建模型,对生物质气化进行了模拟研究。首先,利用文献中的数据对模型进行了验证,模拟结果与文献中的数据基本吻合,证明了该模型的正确性。接着,考察了气化温度、氧气用量（c_ER）、水蒸气与生物质质量比（m_S/m_B）、二氧化碳与生物质质量比（m_CO2/m_B）对产气组成、气体热值、气体产率、气化效率和产气氢碳比（n_H2/n_CO）的影响。结果表明：在850℃、101.325kPa、c_ER=0.2、m_S/m_B=1、m_CO2/m_B=0.6的条件下,气化产物特性为气体热值7.45MJ/m³、气体产率1.78m³/kg、气化效率73.3%、氢碳比1.79。适当提高气化温度有利于气化。c_ER的增大使气体热值、产率和气化效率均迅速降低;但对产气中氢碳比的影响较小。此外,气化剂中水蒸气的适量增加有利于氢气的产生并能明显提高其体积分数,二氧化碳的适量增加有利于一氧化碳的产生并能在一定程度上提高其体积分数,二者均能有效调节产气的氢碳比。     

Development of a dual functional structured catalyst for partial oxidation of methane to syngas

Rh-LaCoO₃ structured catalysts for the oxidative production of syngas from methane were developed by deposition of the active components on La-γ-Al₂O₃ washcoated honeycomb monoliths. SEM/EDS analysis showed a good adhesion of the washcoat layer and a uniform distribution of La and Co, while Rh was favourably located on the outer shell. Catalytic partial oxidation of methane was tested under both isothermal and pseudo-adiabatic conditions showing that the process can be conducted with high yield and selectivity and stable performance at short contact times over the novel catalysts, characterised by a limited content of noble metal and no need for pre-reduction. Further experiments of CO₂ autothermal reforming indicated the possibility to enhance CO production and to reduce the H₂/CO ratio through secondary endothermic reactions consuming CO₂, which are autothermally self-sustained in a single catalytic reactor operated at short contact time by the heat generated through partial oxidation reactions.     

Biomass gasification in supercritical water: Part 1. Effect of the nature of biomass

In this study, biomass feedstocks, including lignocellulosic materials and the tannery wastes, were gasified in supercritical water. Gasification experiments were performed in a batch autoclave at 500 °C. The amount of gases, the gas compositions and the amount of water soluble compounds from gasification were determined. The hydrogen yields ranging between 4.05 and 4.65 mol H₂/kg biomass have been obtained. The results showed that the yields and composition of gases depend also on the organic materials other than cellulose and lignin in lignocellulosic material. In addition to this, it was concluded that the kind of lignin may also have an effect on gasification products. In the case of tannery wastes, the type of tannen agent used in leather production considerably effected the gasification results.