下吸式生物质气化炉气化性能研究

生物质固定床气化技术具有运行稳定、可提供清洁能源等优点,但也存在气化效率差,燃气热值低的问题.以采用炉膛集中供风技术和还原区热量包裹技术的下吸式气化炉为研究对象,研究护膛温度、空气当量比(ER)对燃气成分、燃气热值、气化效率等气化性能的影响,并与以往研究结果进行对比分析.实验表明,该气化炉能保证在较低ER内(0.1～0...     

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。     

两段气化对降低生物质气化过程焦油生成量的影响

在分析焦油生成和裂解的有关机理的基础上，研究开发了两段气化装置，对一段供风和两段供风气化过程进行了大量的对比试验，探讨了温度分布和气化强度等因素对气化中焦油含量的影响。研究结果表明，在同样的试验条件下，两段供风显著提高了气化炉内的最高温度和还原区的温度，气体中焦油的含量仅为常规供风方式的1／10左右，改善了气化机组的性能。     

固定床移动层下吸式生物质气化炉的研究

1前言我国生物质资源丰富，如能有效地利用，将会大大缓解农村常规能源的紧张状态。针对浙江省农村电力不足，同时又有大量谷壳用作燃料，且燃烧效率很低（约10％左右）的情况，浙江省能源研究所与中国水稻研究所进行了小型移动式生物质气化发电系统的研究。本文就该系统固定床移动层下吸式生物质气化炉的设计及试验情况作一介绍。2气化炉的主要结构小型移动式生物质气化发电系统主要由气化炉、净化冷却装置和发动机组成，其中气化炉为固定床移动反应层下吸式气化炉，其结构具有如下特点：（1）气化炉主要由内外两个简体组成。内筒从炉栅网…     

下吸式生物质气化炉的设计

介绍了下吸式生物质气化炉的工作原理、特点,以及主要结构尺寸的设计要点.     

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。     

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。     

生物质气化过程燃气净化技术研究进展

生物质燃气必须经过净化后才能进行使用。文章针对生物质气化过程中燃气净化效率低、焦油脱除困难等问题,对不同种类燃气净化设备(机械式、过滤式、洗涤式和静电式)的优缺点进行了对比研究,并对利用多级设备联合净化燃气的技术措施和方法进行了分析,深入探讨了生物质燃气在净化过程中面临的问题。同时,基于我国农村小型生物质气化站低成本、低能耗、高效率的要求进行考虑,指出开发高效低廉的适用于农村小型生物质气化站的多级燃气净化系统是促进生物质气化集中供气推广的关键技术。     

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.     

Modeling of air gasification of dark fermentation digestate in a downdraft gasifier

The paper presents the results of numerical simulation of the gasification process in a downdraft gasifier to produce syngas with high hydrogen content. For the first time, the possibility of using dark fermentation digestate as a feedstock for thermochemical conversion using air as an oxidizer at equivalence ratio (ER) of 0.45, 0.55 and 0.65 was investigated. Modeling of the gasification process was carried out in the software package Comsol Multiphysics. As a result of numerical studies, the concentrations of the main components of the syngas were obtained. The syngas yield at air gasification was 1.8 m³/kg. At the same time, the combustion heat of the generated gas varied from 3.1 to 3.9 MJ/m³ with the molar ratio (MR) being in the range from 3.1 to 3.9. The maximum content of hydrogen (26.94%) in syngas was achieved at an ER of 0.45. The hydrogen production efficiency HPE ranged from 23.8 to 27.3%. The thermal power that can be obtained from the syngas ranges from 47 to 59 kW. Carbon conversion efficiency coefficient (CCE) was 23.6–28.8%. Based on the design calculation, the main geometric parameters of a downdraft gasifier for the production of syngas from anaerobic digestates were obtained.     

Hydrogen-rich gas production from biomass air and oxygen/steam gasification in a downdraft gasifier

Biomass gasification is an important method to obtain renewable hydrogen. However, this technology still stagnates in a laboratory scale because of its high-energy consumption. In order to get maximum hydrogen yield and decrease energy consumption, this study applies a self-heated downdraft gasifier as the reactor and uses char as the catalyst to study the characteristics of hydrogen production from biomass gasification. Air and oxygen/steam are utilized as the gasifying agents. The experimental results indicate that compared to biomass air gasification, biomass oxygen/steam gasification improves hydrogen yield depending on the volume of downdraft gasifier, and also nearly doubles the heating value of fuel gas. The maximum lower heating value of fuel gas reaches 11.11 MJ/N m³ for biomass oxygen/steam gasification. Over the ranges of operating conditions examined, the maximum hydrogen yield reaches 45.16 g H₂/kg biomass. For biomass oxygen/steam gasification, the content of H₂ and CO reaches 63.27–72.56%, while the content of H₂ and CO gets to 52.19–63.31% for biomass air gasification. The ratio of H₂/CO for biomass oxygen/steam gasification reaches 0.70–0.90, which is lower than that of biomass air gasification, 1.06–1.27. The experimental and comparison results prove that biomass oxygen/steam gasification in a downdraft gasifier is an effective, relatively low energy consumption technology for hydrogen-rich gas production.     

Experimental evaluation of a 35 kVA downdraft gasifier

Energy conversion systems based on biomass are particularly interesting because biomass utilization effectively closes the carbon cycle besides achieving self-sustainability. Biomass is particularly useful for highly populated and agriculture dependent economic nations like China and India. A compact and cost effective downdraft gasification system was developed. The present paper describes an experimental investigation on a biomass based gasifier engine system with a capacity of 35 kVA for power generation application. The problem of cooling and cleaning the hot and dirty gas from the gasifier has been satisfactorily solved by the effective cooling and filtration system. The gasifier developed is observed to be operation friendly. The quality of gas was evaluated in terms of its composition, conversion efficiency and total particulate matter. The maximum output of the power plant was obtained at the combustion zone temperature of 850oC. The experimental investigations showed that the percentage reduction in total particulate matter is 89.32%. The conversion efficiency of the biomass gasifier is found to be dependent on the operation conditions and fuel properties of the gasifier. The optimum value of equivalence ratio was observed to be 0.3134 for achieving the maximum gas conversion efficiency of the present gasifier configuration.     

Gasification of hazelnut shells in a downdraft gasifier

The potential offered by biomass to reduce greenhouse gas production is now being more widely recognised. The energy in biomass may be realised either by direct combustion use, or by upgrading into more valuable and useable products such as gas, fuel oil and higher value products for utilisation in the chemical industry or for clean power generation. Up till now, gasification work has concentrated on woody biomass but recently sources of other biomass with large energy production potential have been identified, namely hazelnut shells. Therefore, a pilot scale downdraft gasifier is used to investigate gasification potential of hazelnut shells. A full mass balance is reported including the tar production rate as well as the composition of the produced gas as a function of feed rate. Additionally, the effect of feed rate on the CV/composition of the product gas and the associated variations of gasifier zone temperatures are determined with temperatures recorded throughout the main zones of the gasifier and also at the gasifier outlet and gas cleaning zones. Pressure drops are also measured across the gasifier and gas cleaning system because the produced gas may be used in conjunction with a power production engine when it is important to have low pressure drop in the system. The quality of the product gas is found to be dependent on the smooth flow of the fuel and the uniformity of the pyrolysis, and so the difficulties, encountered during the experiments are detailed. The optimum operation of the gasifier is found to be between 1.44 and 1.47 N m³/kg of air fuel ratios at the values of 4.06 and 4.48 kg/h of wet feed rate which produces the producer gas with a good GCV of about 5 MJ/m³ at a volumetric flow of 8–9 N m³/h product gas. It was concluded that hazelnut shells could be easily gasified in a downdraft gasifier to produce good quality gas with minimum polluting by-products. It is suggested that, in view of ease of operation, small-scale gasifiers can make an important contribution to the economy of rural areas where the residues of nuts are abundant. It is also suggested that gasification of shell waste products is a clean alternative to fossil fuels and the product gas can be directly used in internal gas combustion engines, thus warranting further investment/encouragement by authorities to exploit this valuable resource.     

下吸式固定床气化炉的加料装置

目前生物质气化机组普遍使用的有螺旋叶片式加料装置、刮板式加料装置和提斗式加料装置.文章介绍了3种加料装置的结构、特点以及对物料的适应性.螺旋叶片式加料装置和刮板式加料装置适应较细的物料;提斗式加料装置对碎板皮、枝权、刨花、玉米芯等尺寸较大、又不均匀的气化原料有较好的适应性.     

Experimental study on hydrogen-rich syngas production via gasification of pine cone particles and wood pellets in a fixed bed downdraft gasifier

The main objective of this research is to investigate gasification of pine cones particles and wood pellets in a pilot scale 10 kWth downdraft fixed bed gasifier using air as an oxidizing agent. In this work, it was found that syngas produced by gasification of pinecones particles is rich in environmentally friendly hydrogen and that would be a clean alternative energy carrier for the production of clean energy. In addition, the effect of gasification temperature and equivalence ratio on the composition of syngas and gasification performance for pine cones and wood pellet were analysed comparatively. During the experimental works gasification took place with air, in a temperature range of 701–1046 °C, for various air equivalence ratios (0.14–0.37) and under atmospheric pressure. It is found that H₂ and CO production increased by increasing reactor temperature. Another finding is that the mean cold gas efficiency was 65% for pinecone particles and 80% for wood pellet gasification.     

Modelling and simulation of a downdraft rice husk gasifier

The behaviour of a downdraft rice husk gasifier of diameter 200 mm and a height 940 mm has been studied. The gasification rate was varied in the range 1.8–4.3 × 10^?2 kg/m²s. The air velocity was varied in the range 0.032–0.099 m/s. The producer gas obtained from the gasifier has a calorific value in the range 3240–4382 kJ/m³. A set of theoretical kinetic equations on the assumption of nonequilibrium conditions has been developed and solved numerically. The simulated temperature profile and outlet gas composition have been compared with those obtained from experimental runs. The model developed from a mechanistic approach is found to explain the behaviour of the present system appreciably within the range of variables studied.     

Investigation of municipal sludge gasification potential: Gasification characteristics of dried sludge in a pilot-scale downdraft fixed bed gasifier

This study presents the research results acquired from conducting municipal sludge gasification in a downdraft type gasifier at pilot scale. The assessment of the results was not only focused on syngas characteristics, but also on the gasification residues: char ash and glassy material. The gasification temperature was varied from 1000 to 1150 °C during the gasification trials. The produced high quality syngas was transferred to the engine to generate the electricity. About 1 kWh electrical power was achieved for approximately 1.2 kg municipal sludge gasified. Most of the heavy metals available in the sludge was found as fixed form in the glassy material. The gasification residues evaluated as valuable materials regarding their characteristics have reuse potential for different beneficial usage alternatives. Based on the costs for the investment and operation and incomes, the return on the investment for this pilot scale system was roughly found as 3.3 years. This study showed that the municipal sludge had an important fuel merit and the energy recovery from the sludge was possible via the gasification application. In this paper, the research results were discussed in detail to make better insight to full-scale applications as a promising alternative for sludge disposal.     

汽化剂对气流床煤汽化炉性能的影响

为研究不同的汽化剂组合对气流床煤汽化炉性能的影响,针对我国具有自主知识产权的两段式干煤粉汽化炉进行了数值模拟研究.利用所建立的数学模型,分析了典型工况下炉膛内部温度及组分的变化规律,并详细讨论不同汽化剂对汽化过程、煤气成分及汽化效率的影响规律.结果表明:炉膛温度随着高度的增加逐渐降低,这与化学反应过程有关;在所讨论的四种汽化剂组合中,汽化剂为O 2/H 2O或O 2/CO 2时汽化效率较高,汽化剂为空气时汽化效率最低,且煤气品质较差.