两级下吸式生物质气化炉气化性能的研究

在自行设计的两级下吸式生物质气化炉中,研究了空气当量比(ER)对气体组成、气体热值、气化效率以及焦油含量的影响。试验结果表明,该新型两级气化炉能够产生焦油含量较低的燃气;在空气预热的条件下,焦油含量更低,可达238 mg/m3。该新型两级气化炉的最佳ER为0.33~0.35,当ER=0.34时,气化气低位热值(LHV)最高为4 409 kJ/m3,气化效率为63.7%,焦油含量低于300 mg/m3。     

在流化床气化炉中生物质与煤共气化的研究(Ⅰ)以空气-水蒸汽为气化剂生产低热值燃气

在600kW流化床气化炉工业示范装置上以空气.水蒸汽为气化剂,将生物质/煤按不同比例进行了共气化的实验研究.在实验研究的运行条件下,得到了生物质/煤混合比例对气化炉工作温度、燃气热值、气体产率和气化效率等重要技术参数的影响.对玉米芯/煤的比例为81/19时的典型实验结果表明:气化炉工作温度869℃,空气当量比ER=0.21,S/B=0.20时,气体产率1.96m3/kg,燃气热值6.4MJ/m3,气化效率71.3%,燃气中焦油含量小于10mg/m3,该炉经过连续运行考核,运行平稳,工况稳定.     

生物质气化过程中焦油的生成

总结了生物质气化过程中焦油的生成和分类,以及气化炉炉型、温度与氧量对焦油生成量和组成的影响规律。初级、二级和三级焦油是应用最为广泛的一种分类方法;不同炉型气化炉产气中焦油质量浓度从大到小依次为:上吸式流化床下吸式,分别在100,10,1g/m~3的量级,两段式等改进炉型在焦油控制上更有优势;上吸式气化炉焦油多为初级组分,下吸式则以无取代基的多环芳香烃等三级焦油为主,而流化床的焦油涵盖了二、三级焦油组分;温度的升高使得焦油量下降,且趋向于转化为化学结构更稳定的三级组分;氧量的增多对焦油的生成具有抑制作用。     

在流化床气化炉中生物质与煤共气化研究(Ⅱ)——以水蒸汽为气化剂生产中热值燃气

以水蒸汽为气化剂,用玉米芯/煤以不同比例为原料,在600kW流化床气化炉上,按二步法制气工艺进行连续运行实验.实验研究了影响燃气热值、气体产率、燃气组成及气化效率的主要因素,确定出气化炉适宜的操作条件及较佳的原料配比范围.得出气化温度为950～1000℃,玉米芯/煤的比例为80/20,S/B在0.7～0.9范围内,燃气热值11～13MJ/m3,气体产率1.1～1.3m3/kg,气化效率75%～80%,燃气中焦油含量小于0.9mg/m3的结果.通过将本技术与国外现有生产中热值燃气的方法进行比较,发现本技术具有产生较高热值燃气和燃气中低焦油含量等优点.     

MW级生物质气化发电站运行特性分析

结合浙江省长兴市某大米加工厂800kW稻壳气化发电系统测试结果,对MW级生物质气化发电站的运行特性进行了详细分析,重点考察了气化温度、当量比和负荷对生物质流化床气化特性的影响,并对系统存在的问题进行了讨论。气化炉轴向温度分布表明:床内存在流化不充分现象;密相区温度与当量比和负荷(加料速率)变化密切相关(负荷不变,床温随当量比增加近似线性升高;当量比相同,较高负荷对应较低的床温)。燃气热值随气化温度升高而降低,负荷变化对其影响不大。当气化温度保持在700~800℃之间时,燃气热值基本稳定在5453~6407kJ/Nm3。原料水分对气化炉的运行也有重要影响:当原料水份低于15%,水分含量增加,有助于提高运行气化当量比,提高燃气品质和产气率;然而原料水分含量超过15%,气化炉温度将很难控制。     

户用型下吸式生物质气化炉性能研究

由于生物质能具有储量大、环境友好等特点,生物质气化技术尤其是户用型气化技术在我国农村应用值得研究。论文在建立下吸式户用型气化系统上,研究了不同生物质原料的气化性能,如对温度分布、气化效率、燃气热值、燃气产量等,并进行了焦油脱除效率的研究。结果表明,该炉型的气化效率可达70％,燃气热值达到6MJ／m3,燃气中焦油含量降低至20mg／m3。     

新型秸秆气化炉及净化工艺

固定床秸秆气化炉是国内目前推广的主要炉型，但这种炉型存在燃气热值低、焦油含量高、输气管路易堵塞等缺点。两段式气化炉设置干馏气和气化气2个出气口，虽然其结构和燃气净化工艺相对复杂，但其燃气热值得到较大提高，热效率较固定床下吸式气化炉高3％～5％。     

在流化床气化炉中生物质与煤共气化的研究（I）以空气-水蒸汽为气化剂生产低热值燃气

在600kW流化床气化炉工业示范装置上以空气-水蒸汽为气化剂,将生物质／煤按不同比例进行了共气化的实验研究。在实验研究的运行条件下,得到了生物质／煤混合比例对气化炉工作温度、燃气热值、气体产率和气化效率等重要技术参数的影响。对玉米芯／煤的比例为81／19时的典型实验结果表明：气化炉工作温度869℃,空气当量比ER=0．21,S／B=0．20时,气体产率1．96m^3／kg,燃气热值6．4MJ／m^3,气化效率71．3％,燃气中焦油含量小于l0mg／m^3,该炉经过连续运行考核,运行平稳,工况稳定。     

中药渣循环流化床热解气化试验

对含水率为20%的六味地黄丸药渣进行气化试验研究,采用空气预热装置将气化剂空气由常温加热为约200℃的热空气,研究了在两种不同温度的气化剂条件下,空气当量比ER对气化特性的影响,并讨论了水蒸气配比S/B对气化特性的影响。结果表明:随着空气当量比的增加,循环流化床炉内气化温度逐渐升高,燃气热值和燃气中焦油含量均逐渐降低,气化效率则先增大后减小。当气化剂为常温冷空气时,理想空气当量比为0.26~0.30,燃气热值为4 400~5 000 kJ/m3,气化效率为67%~70%;气化剂为200℃热空气时,理想空气当量比为0.24~0.29,燃气热值为4 700~5 700 kJ/m3,气化效率为73%~75%;随着水蒸气配比的增加,炉内温度逐渐降低,焦油含量逐渐升高,燃气热值先增加后减小,当S/B为0.4时,燃气热值可达6 100 kJ/m3。研究结果可为中药渣的资源化处理与利用提供参考。     

上吸式固定床生物质气化炉模拟优化

为了提高上吸式固定床生物质气化炉的燃气产物产量和品质,通过模拟试验对气化炉进行优化设计,使生物质气化炉装置的流场分布均匀,氧化层和还原层反应充分。通过热态试验分析生物质气化炉炉内床层温度分布、燃气产物成分、气化强度、产气率与入炉空气量的关系,得到该上吸式固定床生物质气化炉的最佳入炉空气量条件。结果显示：优化设计后的气化炉气化效率达到70%以上,有效提高了生物质炉的气化能力。     

Experimental study on non-woody biomass gasification in a downdraft gasifier

The current paper concerns the process of non-woody biomass gasification, particularly about releasing processes of detrimental elements. The gasification of corn straw was carried out in a downdraft fixed bed gasifier under atmospheric pressure, using air as an oxidizer. The effects of the operating conditions on gasification performance in terms of the temperature profiles of the gasifier, the composition distribution of the producer gas and the release of sulphur and chlorine compounds during gasification of corn straw were investigated. Besides, the gasification characteristics were evaluated in terms of low heating value (LHV), gas yield, gasification efficiency and tar concentration in the raw gas.     

Exergy analysis of updraft and downdraft fixed bed gasification of village-level solid waste

The most commonly used for gasification of village-level solid waste is the fixed-bed gasifier, but there is no reasonable method to evaluate the gasification process. This paper attempts to find a gasifier that is most suitable for gasification of village-level solid wastes through exergy analysis method. Based on experimental data from literature, the exergy efficiencies and LHV(Low Heat Value) of product gas from updraft and downdraft fixed bed gasifier are studied in this paper. The results show that the updraft fixed bed gasifier has higher exergy efficiency, and the gas produced by the downdraft fixed bed gasifier has a higher heating value. Air gasification has higher exergy efficiency than steam gasification and pure oxygen gasification. The highest exergy efficiency at a gasification temperature of about 1000 °C and ER (Equivalence Ratio) value in the range of 0.33–0.36. The volatile content of gasification raw materials is higher, and the gasification efficiency is higher. Through the research of this paper, a new path to reasonably evaluate the gasification process is obtained.     

气化炉中生物质——煤共同气化的模拟研究

在气化炉内采用煤粉和生物质共气化可解决生物质不易稳定流化和生成焦油两大难题,采用流程模拟软件PROⅡ对炉内的气化过程进行了模拟计算,得到了汽氧比和氧碳比和生物质／煤比对气化过程的影响。气化炉内优化的反应条件为：反应温度1350℃,[H2O]／[O2]=0．32,[O][C]=1．05,气化得到的合成气的高位热值Qgr=7150kJ／Nm3,有效气产率为1．59Nm3／kg。     

Gasification performance of olive pomace in updraft and downdraft fixed bed reactors

This study aims to investigate the gasification potential of olive pomace with using different fixed-bed gasifier systems. Olive pomace as a dried form was supplied from a chemical industry plant working on olive oil soap, located in Izmir, Türkiye. After a complete characterization of olive pomace, gasification experiments by using fixed bed reactor systems were done at three different gasifier temperatures as 700, 800 and 900 °C. As a gasification agent, dry air was used with four different flowrates (0.4, 0.2, 0.1, 0.05 L/min) while pure oxygen experiments were carried out with a flow rate of 0.01 L/min. Syngas with H₂ content of 48% and 45% (volumetric) were obtained in updraft and downdraft gasifiers, respectively, by using dried air as a gasifying agent. Heating value of syngas was around 12.4 MJ/Nm³. In the pure oxygen atmosphere, H₂ contents of the syngas were measured as 53% and 39%vol. In the updraft and downdraft gasifiers. This paper presents the research results on the olive pomace gasification study as a part of a large-scale research project and discuss them in the context of hydrogen production from the fixed bed reactors.     

Results with a bench scale downdraft biomass gasifier for agricultural and forestry residues

A small scale fixed bed downdraft gasifier system to be fed with agricultural and forestry residues has been designed and constructed. The downdraft gasifier has four consecutive reaction zones from the top to the bottom, namely drying, pyrolysis, oxidation and reduction zones. Both the biomass fuel and the gases move in the same direction. A throat has been incorporated into the design to achieve gasification with lower tar production. The experimental system consists of the downdraft gasifier and the gas cleaning unit made up by a cyclone, a scrubber and a filter box. A pilot burner is utilized for initial ignition of the biomass fuel. The product gases are combusted in the flare built up as part of the gasification system. The gasification medium is air. The air to fuel ratio is adjusted to produce a gas with acceptably high heating value and low pollutants. Within this frame, different types of biomass, namely wood chips, barks, olive pomace and hazelnut shells are to be processed. The developed downdraft gasifier appears to handle the investigated biomass sources in a technically and environmentally feasible manner. This paper summarizes selected design related issues along with the results obtained with wood chips and hazelnut shells.     

下吸式生物质气化炉热力学平衡模型研究

建立下吸式生物质气化炉热力学平衡模型,该模型包括焦炭、焦油和气体,并用已公布的实验数据对模型进行验证,均方根（RMS）在1.304~3.814之间,结果表明该模型的预测值与实验数据吻合较好,可认为模型可靠。然后模拟棉秆在下吸式生物质气化炉中以空气和富氧气体2种气化氛围下,不同操作参数(当量比、预热温度和气化炉反应温度)下对棉秆气化的气体组分、热值和产率的影响。模拟结果表明：富氧气体为气化剂时,当量比从0.20增至0.35时,气体中N₂含量比空气显著下降,达10%以上,同时发现能提高气体中H₂和CO的含量和热值,热值比空气提高约20%。预热温度对气化成分变化影响有限,随预热温度从30 ℃变化到130 ℃,气体的平均热值从空气的5.2 MJ/m³提高到富氧气体的7.0 MJ/m³。随气化炉内反应温度从750 ℃升至1250 ℃,空气和富氧气体2种气化剂下的H₂和CO分别从20.94%、26.84%和21.77%、28.67%下降到4.06%、9.12%和10.49%、21.60%,导致气体的热值降低。     

Experimental investigations on a 20 kWe, solid biomass gasification system

When the objective is to generate motive or electric power via I.C. engine, the overall pressure drop through the suction gasification system in addition to gas quality has become a sensitive issue. This work, therefore, presents an experimental study on a suction gasifier (downdraft) arrangement operating on kiker wood or Acacia nilotica (L). Studies were conducted to investigate the influence of fluid flow rate on pressure drop through the gasifier system for ambient isothermal airflow and ignited mode, pumping power, and air-fuel ratio, gas composition and gasification efficiency. Results of pressure drop, temperature profile, gas composition or calorific value are found to be sensitive with fluid flow rate. Ignited gasifier gives much higher pressure drop when compared against newly charged gasifier bed with isothermal ambient airflow. Higher reaction temperatures in gasifier tends to enhance gasifier performance, while, overall pressure drop and thus pumping power through the system increases. Both ash accumulated gasifier bed and sand bed filters with tar laden quartz particles also show much higher pressure drops.     

Hydrogen gas yield and trace pollutant emission evaluation in automotive shredder residue (ASR) gasification using prepared oyster shell catalyst

This work examines the hydrogen gas yield and trace pollutants partitioning in automobile shredder residue (ASR) catalytic gasification by fixed bed and fluidized bed gasifier with controlling at equilibrium ratio (ER) 0.2, temperature 900 °C, and 5%–15% prepared catalyst addition. Oyster shell (OS) is a valuable resource due to its higher calcium content that it could prepare as a catalyst for enhancing the hydrogen production in ASR gasification. In the case of the fixed bed gasifier experiments, the highest lower heating value (LHV) and syngas production were found at 900 °C and 10% OS catalyst addition. The maximum H₂ and CO composition were 6.57% and 5.97%, respectively. The LHV of syngas was approximately 4.43 MJ/Nm³. The fluidized bed gasifier could provide a good ASR decomposition and heat transfer behavior. The syngas yield results indicated the maximum H₂ and CO composition were 12.12% and 10.59%, respectively. It was obviously showed that the syngas production and energy conversion efficiency were enhanced by applying fluidized bed gasifier. The maximum produced gas LHV was 10.77 MJ/Nm³ as well as the cold gas efficiency (CGE) of produced gas was 71.62%. On the other hand, the volatile sulfur and chlorine speciation formed in ASR gasification were mainly partitioned in the solid and/or liquid phase. It implied that tested OS catalysts could inhibit the volatile sulfur and chlorine speciation emission in the produced gas as well as enhance the produced gas quality. In summary, this research could provide basic insight into enhanced syngas production and quality in ASR catalytic gasification using the prepared OS catalyst.     

A downdraft high temperature steam-only solar gasifier of biomass char: A modelling study

A numerical model of a solar downdraft gasifier of biomass char (biochar) with steam based on the systems kinetics is developed. The model calculates the dynamic and steady state profiles, predicting the temperature and concentration profiles of gas and solid phases, based on the mass and heat balances. The Rosseland equation is used to calculate the radiative transfer within the bed. The char reactivity factor (CFR) is taken into account with an exponential variation. The bed heating dynamics as well as the steam velocity effects are tested. The model results are compared with different experimental results from a solar packed bed gasifier, and the temperature profile is compared to an experimental downdraft gasifier. Hydrogen is the principal product followed by carbon monoxide, the carbon dioxide production is small and the methane production is negligible, indicating a high quality syngas production. By applying the temperature gradient theory in the steam-only gasification process for a solar gasifier design, a solar downdraft gasifier improves the energy conversion efficiency by over 20% when compared to a solar packed bed gasifier. The model predictions are in good agreement with the experimental results found in the literature.