上吸式气化炉的设计与运行

本文分析了上吸式气化炉的气固流动特性及气化过程。分析了气化过程中三个主要反应过程,即热分解过程、CO_2的还原过程及炭的燃烧过程的反应速率、质量及其影响因素。文中还介绍了常规上吸式气化炉的优缺点并据此提出了改进的炉型,归纳了最佳运行条件及上吸式气化炉的设计要素。     

生物质混流式固定床气化炉运行特性分析

以桉木为原料,对1.5 t/h生物质混流式固定床气化炉运行特性进行了测试分析与评价,与文献报导报道的相关炉型包括上吸式、下吸式、两段式等炉型运行结果进行了比较。实验以气化炉空气通入量作为主要控制变量,对有或无水蒸气条件下的气化炉温度及压力分布、燃气组成、焦油与飞灰含量、气体产率等参数进行了较长周期的测试,结果表明：气化炉运行效果符合设计要求,各项指标相当于或优于传统的下吸式气化炉;气化炉运行温度与压力比较稳定;以冷燃气计算的燃气热值一般约为4 900 ~ 5 500 kJ/Nm3;气化效率约为70% ~ 78%;燃气焦油含量约600 ~ 3 500 mg/Nm3,运行负荷在50%以上时,焦油含量一般低于1 500 mg/Nm3。研究结果有望为混流式气化炉的改进和操作提供优化建议,同时可为其他气化工艺设计提供参考依据。     

改进型固定床上吸式气化炉及其在蒸汽锅炉中的代油燃烧应用

在蒸汽锅炉进行生物质能源改造中,生物质气化燃气代替煤、油具有成本、环保、政策方面的优势,但必须解决焦油的二次污染问题。本文提出以改进型即中部出气固定床上吸式气化炉生产生物质可燃气,及焦油成分随燃气直接在锅炉炉膛燃烧的技术路线,并以2 T/h蒸汽锅炉为例对气化炉的主要结构参数进行设计计算。采用基于锅炉输出蒸汽压力的气化炉鼓风自适应控制方法实现系统的闭环控制。最后通过实际应用案例实测数据的热能计算证明生物质气化燃气在蒸汽锅炉中代替煤、油燃烧的可行性。     

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。     

中部出气的上吸式固定床气化炉及其自动控制的料斗供料系统设计

改进的固定床上吸式生物质气化炉,以锥形下料裙将气化炉分成气化室与储料室两部分,出气口设在下料裙死角处。输出的产出气温度在300℃以上、灰分少、热值高,气化效率高,兼具上吸式与下吸式气化炉的优点,有效解决了常规上吸式气化炉产出气中焦油含量高、热值低问题。自动控制的料斗供料方式保证了气化炉运行的可靠性与安全性,扩展了生物质木料的适用范围。实现产出燃气在蒸汽锅炉中代替煤、木材、油燃烧,可有效解决中小企业的用能问题,达到节能减排的目的。     

单个生物质炭颗粒气化过程的数值模拟

建立下吸式气化炉中单个生物质炭颗粒的一维、准稳态的气化模型,该模型耦合了传热、传质方程和炭颗粒气化化学反应动力学方程,利用Fredholm积分转换,将常微分方程变成非线性方程组,用Matlab进行求解。运用文献中的试验结果对模型进行对比验证,该模型能够较好地预测CO_2-H_2O-N_2还原环境下的炭颗粒转换速率。利用该模型对下吸式气化炉还原区的炭颗粒的气化过程进行模拟分析,计算出还原区的传热系数和传质系数,对炭颗粒内部的温度、浓度、炭转换速率及完全反应的时间进行分析,为整个下吸式气化炉还原区的数值模拟提供条件。     

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…     

750 kW生物质燃料下吸式气化炉的设计

目前推广的生物质气化集中供气系统的用户规模大都在100—200户左右．这种小型的供气系统只能满足单一的炊事用气需求，而且系统的单位建设成本高。下吸式气化炉是生物质气化集中供气系统中的核心设备，建设中等规模的生物质气化集中供气系统的关键技术是对下吸式气化炉进行设计，文中介绍了750kW生物质燃料下吸式气化炉的设计过程。     

固定床秸秆气化技术的探讨

1气化机组的特点及存在的问题　　固定床秸秆气化机组主要由两部分组成,一是气化炉(主要指下吸式气化炉),进行秸秆的气化反应;二是净化设备,即对秸秆煤气进行冷却,并脱除煤气中焦油、灰分、硫化氢等物质。　　由于下吸式气化炉气化煤气经过灰渣层,所以煤气灰分较多,但焦油含量较其它类型炉的低。灰分与焦油凝固在一起,常常堵塞输气管道和净化设备。由于下吸式气化炉采用固定炉排,所以气化炉气化能力低,限制了气化站的供气规模。　　另外,气化炉在开炉时,排放大量含有焦油、一氧化碳的气体,造成严重的环境污染;在停炉时,还会…     

10 MW生物质气化耦合超临界燃煤锅炉系统火用平衡分析

为有效评价生物质气化耦合燃煤锅炉系统能量转换过程,分析该系统的节能潜力,以某10 MW循环流化床生物质气化炉耦合大型超临界燃煤机组为例,建立了该耦合系统的火用分析控制体模型,利用Aspen plus平台对该系统实际运行过程进行火用平衡分析。结果表明：当前运行工况下,生物质气化过程火用损失是耦合系统最大的火用损失,达到42.28%,其次是可燃气体在燃煤锅炉内的燃烧及传热过程,为25.32%。因此系统运行过程中应采取优化运行措施,减小气化过程火用损失,同时气化炉应尽量与高参数的大型机组耦合运行,可燃气体选取在燃煤锅炉合适位置输入,以保证充分燃烧。     

Production of hydrogen energy through biomass (waste wood) gasification

Biomass gasification, conversion of solid carbonaceous fuel into combustible gas by partial combustion, is a prominent technology for the production of hydrogen from biomass. The concentration of hydrogen in the gas generated from gasification depends mainly upon moisture content, type and composition of biomass, operating conditions and configuration of the biomass gasifier. The potential of production of hydrogen from wood waste by applying downdraft gasification technology is investigated. An experimental study is carried out using an Imbert downdraft biomass gasifier covering a wide range of operating parameters. The producer gas generated in the downdraft gasifier is analyzed using a gas chromatograph (NUCON 5765) with thermal conductivity detector (TCD). The effects of air flow rate and moisture content on the quality of producer gas are studied by performing experiments. The performance of the biomass gasifier is evaluated in terms of equivalence ratio, composition of producer gas, and rate of hydrogen production.     

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.     

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.     

Numerical and experimental investigation of hydrogen-rich syngas production via biomass gasification

In this work, the relation between hydrogen-rich syngas production and the gasification parameters such as equivalence ratio (ER), gasification temperature and biomass moisture content were studied. Stoichiometric equilibrium model that developed during this study was used to investigate the optimum hydrogen output generated from woody biomass in a fixed bed downdraft gasifier by considering the thermodynamic equilibrium limit. The mathematical model, based on thermodynamic equilibrium is necessary to understand complicated gasification process that will contribute to obtain maximum attainable hydrogen production. The effects of different oxidizing agents on the hydrogen concentration in the product gas as well as the effect of various air-biomass, oxygen-biomass and steam-biomass ratios were investigated. For validation, the results obtained from the mathematical model were compared with the experimental data obtained from the gasifier that uses air as gasification medium. The validated mathematical model was used to represent the gasifier that uses both oxygen and air-steam mixture as the gasification medium and the theoretical results were obtained for both cases. The theoretical results clearly show that the gasification process specially ones that use the air-steam mixture as the gasification medium can be used for hydrogen production.     

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。     

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.     

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.     

50 kW生物质气化发电系统的设计

气化炉是生物质气化发电系统的核心设备。根据内燃式燃气发电机的性能参数和对燃气质量的要求,对下吸式生物质气化炉进行了设计。通过调整喉管区结构及配风喷嘴位置,可以提高气化炉的产气效率,提高产出气的品质。对系统的燃气净化部分和燃气发电机的选型做了简要介绍。     

Assessment of cow dung as a supplementary fuel in a downdraft biomass gasifier

A model of downdraft gasifier has been described considering thermodynamic equilibrium of species in the pyro-oxidation zone and kinetically controlled reduction reactions in the reduction zone. It is found that the sole use of cow dung as the gasifier fuel is not technically feasible. This is due to very low heating value of the producer gas with much carbon leaving the gasifier as char. However, cow dung can be used as a supplementary fuel blended with a conventional woody biomass, like sawdust. The increased fraction of cow dung in the fuel blend renders the gasification process less efficient, when the gasifier is operated at a particular equivalence ratio. Both the producer gas production rate and its heating value reduce with the increase in the cow dung content in the biomass fuel blend, leading to an overall reduction in the gasifier conversion efficiency. It is observed that an increase in the cow dung content from 0 to 90% in the blended fuel reduces the heating value by 46.8% and the conversion efficiency by 45%. The use of cow dung in between 40 and 50% by mass in the fuel mix would result in an overall fuel economy.