生物质热解煤气中焦油含量的影响因素

采用稻杆、稻壳和木屑作为原料，对生物质材料热解产生的煤气中的焦油含量进行了系统研究。采用冷态捕集方法进行焦油取样；焦油样品用重度分析方法确定煤气中焦油含量。结果表明，由于各种生物质原料的组成及结构不同，热解煤气中，焦油含量存在较大差异，热解温度由550℃升高到900℃以上，热解煤气中焦油含量迅速下降，下降幅度甚至达到70％，随生物质原料在热解反应器内滞留时间的延长，焦油含量也下降，同时给出并分析了焦油含量随热解温度和滞留时间变化的情况。     

快速外热式热解工艺对生物质热解产物的影响

焦油一直是生物质热解技术发展的瓶颈。文中研究了快速外热式热解工艺对生物质热解产物的影响。研究表明:快速外热式热解工艺可以有效地避免常规热解过程中出现的原料夹生问题,缩短从加料到开始热解的时间,减少温度上升期间焦油的产生;由于热解温度高,速度快,大分子芳香族化合物发生二次热解,支链断裂生成小分子的烷、氢等物质,提高了热解气的产率和热值;焦油中CmHn等较大分子通过热解和重整的方式变成生物质气,降低了热解产物中焦油含量;热解过程中,由于生物质炭中的芳香族化合物分解成小分子的烷烃、烯烃等进入生物质燃气中,剩余的主要是固定碳,所以生物质炭的产率较低,其它物相与灰烬的相同。     

裂解温度对生物质热解焦油成分的影响

以锯末粉体为生物质热解焦油研究对象,研究了热解温度对焦油产量和焦油化学成分的影响规律,结果表明,热解温度为500℃时,生物质热解产生的焦油量最大,温度过高或过低都有利于焦油的减少。不同热解温度下,焦油中碳氢化合物的成分主要是芳香烃和少量的脂肪烃,含氧化合物主要是苯酚及其烷基衍生物,含氮化合物主要是吡啶、吡咯及其烷基衍生物等杂环化合物。     

生物质回转窑水蒸气气化制富氢气体试验研究

为充分回收高温炉渣颗粒的余热,设计了回转窑热解反应装置。为验证此装置的可行性,对生物质气化制氢进行了试验研究,并对影响气化性能的主要因素,如气化温度(650~950℃)和水蒸气/生物质当量比S/B(0~3.0)进行了研究。结果表明:温度是影响生物质气化反应的主要因素,高温可以降低焦油和焦炭产率,提高气体产量,增加燃气中氢气含量;水蒸气的加入,有利于焦油和低分子碳氢化合物的气化重整以及焦炭的反应,降低焦油产量,提高气体产量,增加燃气中氢气含量,但是过量的水蒸气会导致反应器内温度下降,不利于反应进行。当S/B为2.20时,气化燃气中氢气含量达到最大值53.6%。     

玉米秸秆低温热解特性实验研究

生物质在实验室环境与实际生产环境下的热解特性存在较大差别。以30mm长玉米秸秆为对象,在管式炉中模拟移动床热解炉中实际传热环境,研究热解温度、热解时间对热解进程的影响规律,同时研究了生物质在实验室环境下的热解特性。研究结果表明,实验室环境下生物质热解温度超过580℃后,提高热解温度对生物质挥发分残留率的影响可以忽略,但在实际生产环境下,由于传热传质条件的变化,在合理的经济时间内,生物质热解温度超过580℃后生物质的挥发分仍有较高的析出速率,移动床热解炉的工艺参数确定应该以实际生产环境下的热解特性为理论基础。     

焦油对生物质气化再燃还原NO的影响

采用配制含焦油模型化合物的生物质气的方法,实验研究了焦油的加入对生物质气化再燃还原NO的影响.模拟的生物质气化气由H2、CH4、CO、CO2、N2构成,并选择了苯、甲苯、苯酚和苯乙烯作为焦油模型化合物.实验在电加热的刚玉管流反应器中进行,实验温度在900～1,400,℃之间.研究了反应器入口焦油含量、氧气浓度、NO初始浓度、反应停留时间及反应温度等因素对还原NO的影响,分析了含焦油的生物质气化再燃特性.证实了焦油有助于提高生物质气化气还原NO的效率;含焦油的生物质气化再燃的最佳当量比在1.20～1.65之间,并且随着NO初始浓度的增加及停留时间的延长,NO还原效率逐渐增加;高温下,焦油含量较高时,有炭黑生成.     

大颗粒生物质高温热解模型的建立及数值模拟

通过对生物质理化特性和热解机理的深入分析,建立了高温条件下生物质热解模型.耦合生物质热解化学反应动力学方程和传热方程,用四阶龙格库塔法和三角追赶法求解,并将计算结果与文献中的实验数据进行对比.模拟结果表明:在径向位置颗粒中心温度的增加速率比表面的增加速率高;随着颗粒粒径的增加,生物质热解完成所需的时间加长;大分子焦油在1273K以上才开始快速裂解,温度越高裂解速率越快,当温度达到1673K时,大分子焦油几乎裂解完全.     

考虑达西流的颗粒状生物质热解模拟

建立生物质热解及液体产物高温热裂解的化学反应动力学模型,该热解模型根据液体产物的特点将可凝挥发分分为生物质油和焦油。将化学反应动力学方程和能量方程耦合,通过数值模拟,分析温度、停留时间、粒径和压力等参数对生物质热解及焦油高温热裂解的影响,并将计算结果与文献中的实验数据进行对比。模拟结果表明:热解反应的吸热效应对温度场和反应进程有较大影响,大颗粒在靠近中心的几层在热解反应区出现一段温度近似维持恒定的水平段,在该阶段前后则是纯物质受热升温物理过程中常见的指数温升曲线,生物质油和焦油的质量析出规律不同。     

热解焦对生物质焦油催化裂解的影响

在小型固定床反应器上,以甲苯为模型化合物对生物质焦油在热解焦上的催化裂解反应进行了研究。重点考察了裂解温度、热解焦粒径尺寸、气相停留时间和水蒸气的流量对焦油的转化率和裂解气成分的影响。结果表明,高温条件下,热解焦对甲苯的裂解具有明显的催化作用。850℃时,所用的两种热解焦对甲苯的转化率分别达到了92.7%和97.0%,同时发现,较小粒径的热解焦和较长的气相停留时间更有利于甲苯的深度裂解。另外,随着水蒸气流量的增加,甲苯的转化率和气体中CO的产率均增大,但当蒸汽甲苯比(S/T)超过6.1时,继续增加水蒸气的流量,甲苯转化率并无明显地提高。     

生物质二次裂解制取氢气的研究

采用生物质热解及二次裂解的方法制取富氢气体.通过对生物质热解产生的气液体成份进行二次裂解,实现热解组分中焦油等含氢化合物的深度转化,提高产品气体中氢气的含量,同时解决了热解产品气中焦油不易去除的难题,得到洁净的富氢气体.实验选用稻壳为原料,分析了热解温度和物料滞留时间等因素对热解气体成份的影响,比较了热解气体和二次裂解气体成份的变化,同时分析了水蒸汽、催化剂等因素对裂解气体成份的影响.实验结果表明,热解温度和物料滞留时间的增加提高了热解气体中氢气的含量,二次裂解、水蒸汽和催化剂的引入都能在一定程度上提高产品气中H2的含量.实验最终表明,氢气体积含量可达到60%以上.     

生物质气化气中焦油非催化裂解实验研究

生物质气化是一种环境友好的新能源利用技术,焦油作为生物质气化的副产物,是限制气化技术发展的主要因素.试验针对生物质气化产出气中焦油在700～1 000℃裂解温度区间的裂解特性进行了分析,并提出了焦油裂解产气率的概念.试验表明,焦油裂解气可以成为生物质气化气的有效的能量补充,而且随着裂解温度的升高,焦油裂解产气率增加,焦...     

Gas cleaning for IC engine applications from fixed bed biomass gasification

Gas cleaning for tar and particle removal is necessary for internal combustion (IC) engine applications of producer gas from fixed bed biomass gasifiers which are usually in the capacity range from 100 kW up to 5000 kW. In the present investigation, tar and particle collection efficiencies have been determined in a sand bed filter, a wash tower, two different fabric filters, and a rotational particle separator (RPS) in different test runs with fixed bed gasifiers. Tar adsorption on coke has been investigated in a fixed bed batch reactor. Furthermore data from literature for catalytic tar crackers, venturi scrubbers, a rotational atomizer, and a wet electrostatic precipitator (ESP) are given. Based on the presented gas cleaning efficiencies and the investment cost, an assessment of gas cleaning systems is made for IC engine applications from cocurrent gasifiers. The results show that the postulated gas quality requirements for IC engines cannot be safely achieved with state-of-the-art gas cleaning techniques and that 90% particle removal is easier to achieve than 90% tar removal. Except for the catalytic tar crackers which are considered as an option for applications above several MW and for gases with a high tar level, none of the investigated gas cleaning systems can securely meet a tar reduction exceeding 90%. Therefore one of the key issues for a successful application of biomass derived producer gas from small scale gasifiers is the tar removal, where further development is needed.     

A study on a multi-stage hybrid gasifier-engine system

This paper presents the results of a study on a multi-stage hybrid biomass–charcoal gasification to produce low tar content gas for engine application using coconut shell as a fuel. The performance of a gasifier-engine system consisting of the hybrid biomass–charcoal gasifier, a gas cleaning/cooling system and a diesel engine is also discussed.

The lowest tar content found in hybrid coconut shell-charcoal gasification was 28 mgNm⁻³. Using a spray tower, producer gas could be cooled down to 40°C; almost tar-free gas was obtained after cooling the producer gas from the hybrid gasifier system. A three-cylinder Perkins diesel engine was tested at a constant speed of 1500 rpm on diesel alone and dual fuel modes of operation. A maximum of 81% of the total heat energy input was replaced by the producer gas at an electricity generation of 11.44 kWe.     

Tar property,analysis, reforming mechanism and model for biomass gasification—An overview

Biomass becomes an important primary energy source as well as renewable energy source. As the most promising biomass utilization method, biomass gasification is gaining attention as a route for biomass energy production, but producer gas from this process usually contains unacceptable levels of tar. The tar control and convert is a key issue for a successful application of biomass-derived producer gas. A detail overview on tar chemical and physical properties, reforming mechanism and reaction kinetic model are summarized in this paper.     

基于主成分分析法的筛板式喷淋塔阻力特性影响因素研究

喷淋塔是石灰石-石膏湿法烟气脱硫装置的主要设备之一,对喷淋塔内部结构的优化研究一直是研究者们感兴趣的课题。为了探索筛板式喷淋塔内部的气液两相接触状态,采用空气-水作为介质,对孔径为6～30mm,开孔率为16%～48%的筛板进行了气液两相流动特性测试实验。利用SPSS软件,通过主成分分析法对筛板式喷淋塔的脱硫特性进行研究。主要针对筛板式喷淋塔的烟气流速、喷淋量、筛板孔径、开孔率等对阻力特性的影响进行研究。依据主成分分析法得出烟气流速、喷淋量和筛板孔径是影响筛板式喷淋塔阻力特性的最主要因素。     

蛋白粉尾气余热回收喷淋塔的热工特性研究

大豆蛋白粉干燥工艺过程产生的高温尾气中蕴含着大量显热和潜热,而无填料、垂直逆流喷淋塔可以深度回收尾气中的余热。对此建立了喷淋塔的数值模型,并通过实验验证其准确性;应用所建模型,分析喷淋高度、入口水温、喷淋密度、尾气流速和尾气入口湿球温度对喷淋塔热回收性能的影响规律,进而获得了喷淋塔在实验工况范围内的换热效率曲线及经验关联式,为尾气喷淋热回收塔的优化设计与工程应用提供了分析工具。     

Full-scale simulation of flow field in ammonia-based wet flue gas desulfurization double tower

With the increasingly strict environmental requirements, sintering flue gas desulfurization in double tower had been applied to improve desulfurization efficiency and reduce the “ammonia escape” and “aerosol” phenomena. In this work, the operating conditions of a sintering plant were simulated by ANSYS CFX and the flow fields without and with fluid spray of a full-scale ammonia-based wet flue gas desulfurization (WFGD) double tower were investigated. According to the results, the evaporating tower had a profound cooling effect on flue gas with spray. The gas flow distribution was non-uniform in evaporating tower, which needed further optimizations. The flow with spray was more uniform in both towers. The pressure drop mainly took place in absorption areas of desulfurization tower. The velocity of inlet region with spray was lower than that without spray in desulfurization tower. The temperature decreased along with the forward direction of gas flow due to the heat transfer with spray in desulfurization tower. The study provided useful data for further optimization in order to achieve high desulfurization efficiency.     

First and second law thermodynamic analysis of a single and dual-stage ignition biomass downdraft gasifier

The dual-stage ignition biomass downdraft gasifier is an enormous tar reduction technology as against a single-stage ignition biomass gasification. Exergetic analysis of the system guides toward a possible performance enhancement. In dual-stage gasification, around 67.76% of input exergy is destructed in the several components, while 9.16% is obtained as a useful exergy output and 24.34% is found to be as a useful energy output there. The entire unit was assessed with a progressively rising electric load from 15.24 kW to 38.86 kW. The enhanced producer gas quality comes from 57% combustible gas with a higher heating value of 6.524 MJ/Nm³ and tar content of 7 mg/Nm³ after the paper filter, whereas the biomass consumption rate is 58 kg/h at the greatest load with the grate temperature of 1310–1370 °C. The samples of exhaust gas emissions are obtained environmentally favorable. The results even described that the dual-stage ignition biomass downdraft gasifier has significantly greater energetic and exergetic efficiency as compared to the single-stage gasifier.     

温度对生物质热解产物有机结构的影响

在管式炉上研究了生物质在不同温度下的热解过程,采用傅立叶红外光谱仪研究了热解温度对稻草热解固体产物半焦和液体产物焦油的有机结构变化的影响,用色质联用仪(GC/MS)分析了焦油的主要成分随温度的变化。研究表明,生物质的热解主要集中在200～600℃,高温有利于气体产物的析出,半焦的量及其所含的有机官能团(C=O,C=C,C-H,C-O和OH等)随热解温度的升高快速减少;焦油的量随温度的升高先增大后减小,在500℃时达到最大值,焦油中官能团的种类较稳定,但是吸收峰强度随温度的升高呈减弱的趋势。