秸秆锅炉应用研究探讨

通过对生物质能技术发电机理的概述,结合我国生物质能原料的现状,分析生物质能原料在城市供热区域锅炉应用技术上存在问题,提出通过供热锅炉局部技术改造应用生物质能的可行性和必要性。     

秸秆气化技术及集中供气系统

秸秆气化技术及集中供气系统山东省科学院能源研究所我国秸秆资源大量浪费和农村商品能源紧张的局面，已引起政府和社会的关注。这个问题又与农民生活质量的提高及农村生态环境的改善紧密相连。寻求秸秆利用的新模式，改变农村燃料结构，改进农民炊事方式，已成为广大科技...     

浅谈秸秆发电技术

介绍可再生能源在国内、省内的概况．对生物质发电的几点思考与建议。     

60kW两段式秸秆气化炉运行特性

研究了上海交通大学热能研究所研制的60kW两段式秸秆气化炉的运行特性.以秸秆为原料在该气化炉上实验,考察原料量、空气过量系数对气化炉生产能力和碳转化率以及气化效率的影响,并分析了气化气成分及热值.数据表明该气化炉各项参数均优于一般固定床气化炉:原料消耗量为100kg/h,ER=0.35时,秸秆气化气平均热值为6599.6010/m~3,产气率为1.88m~3/kg,碳转化率为91.3%,气化效率为84.6%.     

高效催化剂催化裂解玉米秸秆

农作物秸秆裂解液化是一种很有发展前景的生物质利用方式。介绍了一种高效裂解催化剂,能有效地、选择性地断裂纤维素、半纤维素和木质素中的C-O醚氧键,结合自动化设计原理所制造出的特制反应炉,能使玉米秸秆有效裂解形成有机单体化合物,液体产物的量可达57.7%,固体残渣的量不超过25.0%。而且只有不到20种的有机单体化合物,这些有机化合物能方便地采用精馏的方法分离出来,可为实现大规模工业化生产打下基础。     

生物质焦油裂解的技术关键

生物质焦油是生物质气化过程中有害的副产物，它会降低气化效率，影响设备运行，所以必须加以有效利用和处理。本文介绍了国内外焦油催化裂解的研究现状，详细地分析了讨论了催化裂解的关键过程和工艺件，总结出了焦油催化裂解的最佳条件和比较有前景的工艺路线。     

在氮气氛围下木薯渣热裂解的试验研究

试验研究了木薯渣在不同升温速率下热裂解产物的组成随温度变化的情况,对木薯渣在N2氛围下的TG和DTG曲线进行了分析.试验结果表明.当温度为290～430℃时,木薯渣热裂解速率最快,焦炭产量随着温度的升高而降低,焦油及气体产量随着温度的升高而增加;木薯渣在600℃以下快速热解有利于焦油和焦炭的生成,在600 ℃以上快速热解有利于气体产物的生成.通过GC-MS分析发现,焦油中的主要组分是苯酚类化合物.     

热重分析法研究水稻秸秆热裂解特性

在氮气氛围下,利用热重分析法研究了水稻秸秆的热裂解过程,考察了升温速率、熔盐种类和盐质比对热裂解特性的影响,计算了热裂解动力学参数。结果表明:随着升温速率的增加,水稻秸秆热裂解的初始温度、最大失重温度和裂解终止温度升高,热滞后现象严重,残炭产率略呈下降趋势,高升温速率对炭的生成有一定的抑制作用;熔盐使热裂解主失重区间变窄,降低了热裂解的终止温度,显著影响最大失重温度;盐质比对热裂解最大失重温度影响显著,盐质比为1∶1时,最大失重温度降为280.7℃,随着盐质比的增大,最大失重温度向右侧偏移。采用积分法分段处理水稻秸秆的热裂解过程。     

Effect of cellulose and lignin content on pyrolysis and combustion characteristics for several types of biomass

Fundamental pyrolysis and combustion behaviors for several types of biomass are tested by a thermo-gravimetric analyzer. The main compositions of cellulose and lignin contents for several types of biomass are analyzed chemically. Based on the main composition results obtained, the experimental results for the actual biomass samples are compared with those for the simulated biomass, which is made of the mixture of the cellulose with lignin chemical. The morphological changes before and after the reactions are also observed by a scanning electron microscope. The main compositions in the biomass consisted of cellulose and lignin. The cellulose content was more than lignin for the biomass samples selected in this study. The reaction for the actual biomass samples proceeded with the two stages. The first and second stage corresponded to devolatilization and char combustion during combustion, respectively. The first stage showed rapid mass decrease caused by cellulose decomposition. At the second stage, lignin decomposed for pyrolysis and its char burned for combustion. For the biomass with higher cellulose content, the pyrolysis rate became faster. While, the biomass with higher lignin content gave slower pyrolysis rate. The cellulose and lignin content in the biomasses was one of the important parameters to evaluate the pyrolysis characteristics. The combustion characteristics for the actual biomass depends on the char morphology produced.     

Solar thermochemical gasification of wood biomass for syngas production in a high-temperature continuously-fed tubular reactor

Biomass gasification is an attractive process to produce high-value syngas. Utilization of concentrated solar energy as the heat source for driving reactions increases the energy conversion efficiency, saves biomass resource, and eliminates the needs for gas cleaning and separation. A high-temperature tubular solar reactor combining drop tube and packed bed concepts was used for continuous solar-driven gasification of biomass. This 1 kW reactor was experimentally tested with biomass feeding under real solar irradiation conditions at the focus of a 2 m-diameter parabolic solar concentrator. Experiments were conducted at temperatures ranging from 1000 °C to 1400 °C using wood composed of a mix of pine and spruce (bark included) as biomass feedstock. This biomass was used under its non-altered pristine form but also dried or torrefied. The aim of this study was to demonstrate the feasibility of syngas production in this reactor concept and to prove the reliability of continuous biomass gasification processing using solar energy. The study first consisted of a parametric study of the gasification conditions to obtain an optimal gas yield. The influence of temperature, oxidizing agent (H₂O or CO₂) or type of biomass feedstock on the product gas composition was investigated. The study then focused on solar gasification during continuous biomass particle injection for demonstrating the feasibility of a continuous process. Regarding the energy conversion efficiency of the lab scale reactor, energy upgrade factor of 1.21 and solar-to-fuel thermochemical efficiency up to 28% were achieved using wood heated up to 1400 °C.     

Biomass pyrolysis-gasification over Zr promoted CaO-HZSM-5 catalysts for hydrogen and bio-oil co-production with CO2 capture

In order to enhance biomass conversion technology, a three-stage conversion process for biomass pyrolysis-gasification with applied Zr modified CaO-HZSM-5 catalysts is proposed for hydrogen and bio-oil co-production with CO₂ capture. The process is divided into three parts: biomass pyrolysis, steam biochar gasification, and catalyst regeneration with CO₂ capture. The Zr modified CaO-HZSM-5 catalysts are prepared using ion exchange and incipient wetness impregnation methods. The bifunctional catalysts were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), energy dispersive X-ray fluorescence (EDXRF), and transmission electron microscopy (TEM). The cycled CaO-Zr-ZSM-5 catalysts were also characterized by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). Results indicate that CaO-HZSM-5 catalyst shows the best bio-oil selectivity (56% of phenols and 73% of aromatic compounds determined by GC/MS). Furthermore, higher hydrogen yields and concentration can be obtained using the modified CaO-Zr/H-ZSM-5 catalysts.     

Biomass-based hydrogen production: A review and analysis

In this study, various processes for conversion of biomass into hydrogen gas are comprehensively reviewed in terms of two main groups, namely (i) thermo-chemical processes (pyrolysis, conventional gasification, supercritical water gasification (SCWG)), and (ii) biological conversions (fermentative hydrogen production, photosynthesis, biological water gas shift reactions (BWGS)). Biomass-based hydrogen production systems are discussed in terms of their energetic and exergetic aspects. Literature studies and potential methods are then summarized for comparison purposes. In addition, a biomass gasification process via oxygen and steam in a downdraft gasifier is exergetically studied for performance assessment as a case study. The operating conditions and strategies are really important for better performance of the system for hydrogen production. A distinct range of temperatures and pressures is used, such as that the temperatures may vary from 480 to 1400 °C, while the pressures are in the range of 0.1–50 MPa in various thermo-chemical processes reviewed. For the operating conditions considered the data for steam biomass ratio (SBR) and equivalence ratio (ER) range from 0.6 to 10 and 0.1 to 0.4, respectively. In the study considered, steam is used as the gasifying agent with a product gas heating value of about 10–15 MJ/Nm³, compared to an air gasification of biomass process with 3–6 MJ/Nm³. The exergy efficiency value for the case study system is calculated to be 56.8%, while irreversibility and improvement potential rates are found to be 670.43 and 288.28 kW, respectively. Also, exergetic fuel and product rates of the downdraft gasifier are calculated as 1572.08 and 901.64 kW, while fuel depletion and productivity lack ratios are 43% and 74.3%, respectively.     

Biorefineries: Current activities and future developments

This paper reviews the current refuel valorization facilities as well as the future importance of biorefineries. A biorefinery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, and chemicals from biomass. Biorefineries combine the necessary technologies of the biorenewable raw materials with those of chemical intermediates and final products. Char production by pyrolysis, bio-oil production by pyrolysis, gaseous fuels from biomass, Fischer–Tropsch liquids from biomass, hydrothermal liquefaction of biomass, supercritical liquefaction, and biochemical processes of biomass are studied and concluded in this review. Upgraded bio-oil from biomass pyrolysis can be used in vehicle engines as fuel.     

Hydrogen production from biomass and plastic mixtures by pyrolysis-gasification

The addition of plastics to the steam pyrolysis/gasification of wood sawdust with and without a Ni/Al₂O₃ catalyst was investigated in order to increase the production of hydrogen in the gaseous stream. To study the influence of the biomass/plastic ratio in the initial feedstock, 5, 10 and 20 wt.% of polypropylene was introduced with the wood in the pyrolysis reactor. To investigate the effect of plastic type, a blend of 80 wt.% of biomass and 20 wt.% of either polypropylene, high density polyethylene, polystyrene or a mixture of real world plastics was fed into the reactor. The results showed that a higher gas yield (56.9 wt.%) and a higher hydrogen concentration and production (36.1 vol.% and 10.98 mmol H₂ g⁻¹ sample, respectively) were obtained in the gaseous fraction when 20 wt.% of polypropylene was mixed with the biomass. This significant improvement in gas and hydrogen yield was attributed to synergetic effects between intermediate species generated via co-pyrolysis. The Ni/Al₂O₃ catalyst dramatically improved the gas yield as well as the hydrogen concentration and production due to the enhancement of water gas shift and steam reforming reactions. Very low amounts of coke (less than 1 wt.% in all cases) were formed on the catalyst during reaction, with the deposited carbonaceous material being of the filamentous type. The Ni/Al₂O₃ catalyst was shown to be effective for hydrogen production in the co-pyrolysis/gasification process of wood sawdust and plastics.     

Thermo chemical conversion of biomass - Eco friendly energy routes

Biomass is indirect source of solar energy and it is renewable in nature. It is one of the most important energy source in near future because of its extensive spread availability and promising potential to reduce global warming. Thermo chemical conversion of biomass yield variety of solid, liquid and gaseous fuels and have equal importance both at industrial and ecological point of views. Present review gives holistic view of various thermo-chemical conversion route of biomass. Gasification technology, pyrolysis options and scope of potential by product from there routes like hydrogen and charcoal production comprehensively reviewed with present context.     

Efficiency assessment of an integrated gasifier/boiler system for hydrogen production with different biomass types

In this study, we utilize some experimental data taken from the literature, especially on the air-blown gasification characteristics of six different biomass fuels, namely almond shell (ASF), walnut pruning (WPF), rice straw (RSF), whole tree wood chips (WWF), sludge (SLF) and non-recyclable waste paper (NPF) in order to study the thermodynamic performance of an integrated gasifier–boiler power system for its hydrogen production. In this regard, both energy and exergy efficiencies of the system are investigated. The exergy contents of different biomass fuels are calculated to be ranging from 15.89 to 22.07 MJ/kg, respectively. The hydrogen concentrations based on the stack gases at the cyclone exit are determined to be between 7 and 18 (%v/v) for NPF and ASF. Also, percentages of combustible vary from 30% to 46%. The stack gas has physical and chemical exergies. The total specific exergy rates are calculated and illustrated. These values change from 3.54 to 6.41 MJ/kg. Then, two types of exergy efficiencies are calculated, such as that exergy efficiency 1 is examined via all system powers, exergy and efficiency 2 is calculated according to specific exergy rates of biomass fuels and product gases. While the exergy efficiencies 1 change between 4.33% and 11.89%, exergy efficiencies 2 vary from 18.33% to 39.64%. Also, irreversibilities range from 9.76 to 18.02 MJ/kg. Finally, we investigate how nitrogen contents of biomass fuels affect on energy and exergy efficiencies. The SLF has the highest amount of nitrogen content as 5.64% db while the NPF has the lowest one as 0.14% db. The minimum and maximum exergetic efficiencies belong to the same fuels. Obviously, the higher the nitrogen content the lower the efficiency based on an inverse ratio between exergy efficiency and nitrogen content.     

Existing large steam power plant upgraded for hydrogen production

This paper presents and discusses the results of a complete thermoeconomic analysis of an integrated power plant for co-production of electricity and hydrogen via pyrolysis and gasification processes fed by various coals and mixture of coal and biomass, applied to an existing large steam power plant (ENEL Brindisi power plant – 660 MW_e). Two different technologies for the syngas production section are considered: pyrolysis process and direct pressurized gasification. Moreover, the proximity of a hydrogen production and purification plants to an existing steam power plant favors the inter-exchange of energy streams, mainly in the form of hot water and steam, which reduces the costs of auxiliary equipment. The high quality of the hydrogen would guarantee its usability for distributed generation and for public transport. The results were obtained using WTEMP thermoeconomic software, developed by the Thermochemical Power Group of the University of Genoa, and this project has been carried out within the framework of the FISR National project “Integrated systems for hydrogen production and utilization in distributed power generation”.