煤的富氧气化特性研究

根据煤不同组分和不同反应阶段的特点,实施煤的热解、气化、燃烧分级转化,可以使煤气化技术简化,并有效解决煤中污染物的脱除问题。基于分级转化的思想,在小型流化床实验台上,采用枣庄烟煤为主要原料,研究了氧气浓度和空煤比对气化过程的影响,并与空气气化的结果进行对比分析,可为研究煤部分气化及半焦燃烧集成提供理论依据。     

富氧气氛下水蒸气气化对煤焦燃烧的影响

采用自制的恒温高升温速率热重实验台,研究了富氧气氛下水蒸气气化对煤焦燃烧特性的影响,并使用低温氮吸附仪和环境扫描电子显微镜分析燃烧过程中煤焦孔隙结构。结果表明:在低氧浓度下,水蒸气气化作用对煤焦燃烧影响显著,可失重速率增大,燃尽时间提前,且随氧气浓度的增加而减弱;随着温度升高R0.5指数逐渐增加,当环境温度为1 000℃、水蒸气浓度为20%时,R0.5增长速度最大;煤焦燃烧过程中,加水后煤焦比表面积增大,孔隙结构丰富。     

生物质富氧气化产气特性的实验研究与灰色关联分析

在小型上吸式固定床气化炉内对典型生物质进行富氧气化试验，分析了试验物料、气化温度和氧气流量对气化产气特性的影响。实验研究表明，物料含可燃质多时，产气品位高；随着气化温度的升高，产气中可燃气含量增加；氧气流量增加后，产气热值出现最大值。通过灰色关联分析发现，物料性质和气化温度是影响产气特性的主要因素。     

生物质富氧气化特性的研究

富氧气化是先进的中热值气化方法之一，具有设备体积小，运行稳定等优点。从富氧气化的原理出发，分析氧气浓度，气化当量比等因素对气化结果的影响，并在实验的基础上，分析讨论提高了富氧气化经济性和实用性的途径，总结得到的循环流化床富氧气化的最佳运行条件：氧气浓度，气化当量比约０．１５。     

生物质富氧——水蒸气气化制氢特性研究

以一个鼓泡流化床为反应器,对生物质富氧—水蒸气气化制取富氢燃气的特性进行了一系列的实验研究。通过对试验数据的分析,探讨了主要参数温度、水蒸气/生物质(S/B)和氧浓度对气体成分、氢产率和潜在产氢量的影响。结果表明:在3个主要参数的变化范围内,氢产率和潜在氢产量受温度的影响最大:当温度从700~900℃时,每千克生物质氢产量从18g增加到了53g,每千克生物质潜在氢产量从71.6g增加到了115.6g。     

串行流化床生物质气化制取富氢气体模拟研究

利用串行流化床技术将生物质热解气化和燃烧过程分开,气化反应器和燃烧反应器之间通过灰渣进行热量传递,实现了自供热下生物质气化制氢.利用Aapen Plus软件模拟制氢过程,通过比较单反应器生物质气化的模拟结果和实验结果,验证了模拟研究的可行性.重点研究串行流化床中非催化气化与CaCO3作用下的气化过程,探讨了气化温度、蒸汽与生物质的质量配比(S/B)对制氢的影响,为今后开展生物质气化制氢试验提供了理论参考.结果表明:对应不同气化温度,S/B都存在一个最佳值,且随着温度升高其值减小.当气化温度低于750℃时,添加CaCO3可大幅提高氢产率,气化温度为700℃且在S/B约为0.9时氢产率最大,达43.7 mol·(kg生物质)-1(干燥无灰基),比同温度下非催化气化提高了20.3%.随着气化温度升高,CaCO3促进作用减弱.     

生物质富氧气化气作为机动车燃料的初步试验

试验研究了生物质气化产出气作为机动车燃料的可行性.在实际运行的生物质气化系统中进行了富氧试验,并将生物质富氧气化产出气作为机动车燃料,进行了行驶试验.分析了富氧气化剂对于气化产出气成分的影响,对生物质气化产出气作为机动车燃料的经济可行性进行了简单分析.结果表明,采用富氧气化剂可以明显提高产出气的热值,增加气体的能量密度,同时,产出气作为燃料能够满足机动车的动力性要求;在生物质原料成本控制在一定范围内的情况下,生物质气化产出气作为汽车燃料能够体现一定的经济性.     

造纸废渣水蒸气气化制取富氢燃气实验研究

目前造纸废渣的主要处理方式为焚烧,虽然该工艺简单有效,但会产生二噁英等有害物质,因此部分地区环保部门开始限制新建焚烧项目。针对造纸废渣处理难的问题,结合废物特性,探索使用气化工艺对其进行处理。在700～900℃利用水蒸气与造纸废渣共同反应制取富氢燃气,并进一步研究了CaO、MgO作为催化剂对气化反应的影响。结果显示：气化温度为900℃,产气中H₂的比例超过50%;两种催化剂均可催化大分子有机物分解为气体小分子,导致燃气热值及气化效率提高。     

污泥热解残渣水蒸气气化制取富氢燃气

采用固定床反应器,进行了污泥热解残渣水蒸气气化制取富氢燃气的研究。考察了反应温度、固相停留时间、水蒸气流量及催化剂对气化效果及气体产物组成的影响。结果表明:随着反应温度的升高,气体产率由0.096 7 m3/kg逐渐增加到0.460 0 m3/kg,燃气中H2含量由17.87%逐渐增加到52.44%;在最佳固相停留时间为15min时,气体产率达到0.540 m3/kg;最佳水蒸气流量为1.19 g/min,此时产气量达到最大值0.61 m3/kg,H2含量为64.7%;添加催化剂有利于气体中H2含量的提高。     

富氧气氛下循环流化床煤燃烧试验研究

在O2／CO2气氛和O2／N2气氛下,对氧浓度为21％～35％的循环流化床进行了煤燃烧的试验研究,比较了不同气氛下的煤燃烧特性和炉内温度分布以及NOx、NO2的排放规律和脱硫效率．试验显示富氧气氛下煤能够稳定燃烧,循环回路通畅;给煤量一定,随着试验气氛中氧含量的增加,燃烧效率逐渐增高．O2／CO2气氛下的燃烧效率略低于相同氧含量的O2／N2气氛下的燃烧效率;随着试验气氛中氧含量的增加,NOx排放量增加,SO2排放量略有减小,石灰石脱硫效率略有提高．     

喷动流化床煤气化技术研究的发展

本文论述了喷动化床煤气化技术的原理、优点以及国内外的主要技术进展，并结合当前国内外的研究情况从气化特性试验研究、机理模型研究、工业应用研究三个方面进行了分析，指出了喷动流化床煤气化技术的发展前景以及今后研究方向。     

流化床生物质气化发电过程动力学建模与验证

为更好地描述生物质气化过程的反应机理,文章从模型采用的反映速率形式出发,对已建立的动力学模型[1]做了进一步修正,并拟和了以松木屑为生物质原料的气化反应动力学参数,建立了包括质量平衡方程、反应动力学方程以及能量平衡方程在内的整体生物质气化动力学模型。最后以MATLB为平台,通过模型仿真,从反应进程以及最终气体组分两个方面验证了模型的可靠性。为进一步应用该模型评价和优化流化床生物质气化过程气化方案和气化参数打下了基础。     

基于Gibbs自由能最小化原理模拟生物质流化床气化

基于能质平衡和吉布斯(Gibbs)自由能最小化原理,选择松木屑和麦秆两种生物质,利用化工商业化软件ASPEN PLUS模拟生物质流化床气化过程,并结合试验数据验证模拟结果的准确性。在此基础上考察了高温、原料含水率大范围变化等试验中较难实现的操作对气化的影响。模拟结果表明,搭建的气化模型能较好地模拟生物质气化过程,对生物质气化试验与工程放大具有一定的参考价值。     

Experimental research for biomass steam gasification in a fluidized bed

A fluidized bed gasification system was built to investigate the biomass steam gasification performance in different conditions. Medium heating value syngas with 34% H₂ content and no more than 20 g/Nm³ tar content could be obtained under 800°C with a S/B (steam vs. biomass ratio) of 0.9 by using olivine as bed material. The results indicated that syngas quality (including H₂ content, gasification efficiency, tar reduction, etc.) is in a positive correlation with temperature and S/B, but has a negative correlation with fluidization number (FN). Compared with quartz sand and dolomite, olivine is more suitable for fluidized bed because of its catalytic ability and good abrasion performance for fluidized bed gasifier. As a result, a set of optimum parameters is recommended with S/B of 0.9~1.0, FN of 1.4, and temperature of 800°C in this study.

Tar is a by-product from the gasification process, which will cause the pipeline congestion, reduce the gasification efficiency, and deteriorate the working condition. According to this experiment, the temperature and S/B both have a negative effect on tar content, while tar content increased with increase in the FN. Dolomite and olivine both have an inhibition function on tar, and the olivine is considered the best choice of bed material because of its good anti-wear properties.     

生物质流化床气化技术应用研究现状

按所得产品不同,可将生物质气化技术分为制氢、发电和合成液体燃料3大类。文章介绍了生物质流化床水蒸气气化制氢、催化气化制氢和超临界水气化制氢的工艺特点;分析了生物质流化床气化发电的技术、经济可行性;简述了生物质流化床气化合成液体燃料的研究现状;指出气化产出气化学当量比调变、焦油去除问题和合成气净化是生物质流化床气化技术应用的主要瓶颈,认为定向气化是今后研究的主要方向。     

Biomass steam gasification in bubbling fluidized bed for higher-H2 syngas: CFD simulation with coarse grain model

A comprehensive coarse grain model (CGM) is applied to simulation of biomass steam gasification in bubbling fluidized bed reactor. The CGM was evaluated by comparing the hydrodynamic behavior and heat transfer prediction with the results predicted using the discrete element method (DEM) and experimental data in a lab-scale fluidized bed furnace. CGM shows good performance and the computational time is significantly shorter than the DEM approach. The CGM is used to study the effects of different operating temperature and steam/biomass (S/B) ratio on the gasification process and product gas composition. The results show that higher temperature enhances the production of CO, and higher S/B ratio improves the production of H₂, while it suppresses the production of CO. For the main product H₂, the minimum relative error of CGM in comparison with experiment is 1%, the maximum relative error is less than 4%. For the total gas yield and H₂ gas yield, the maximum relative errors are less than 7%. The predicted concentration of different product gases is in good agreement with experimental data. CGM is shown to provide reliable prediction of the gasification process in fluidized bed furnace with considerably reduced computational time.     

Physicochemical properties and gasification reactivity of the ultrafine semi-char derived from a bench-scale fluidized bed gasifier

Zhundong coalfield is the largest intact coalfield worldwide and fluidized bed gasification has been considered as a promising way to achieve its clean and efficient utilization.The purpose of this study is to investigate the physieochemical properties and gasification reactivity of the ultrafine semi-char,derived from a bench-scale fluidized bed gasifier,using Zhundong coal as fuel.The results obtained are as follows.In comparison to the raw coal,the carbon and ash content of the semi-char increase after partial gasification,but the ash fusion temperatures of them show no significant difference.Particularly,76.53％ of the sodium in the feed coal has released to the gas phase after fluidized bed gasification.The chemical compositions of the semi-char are closely related to its particle size,attributable to the distinctly different natures of diverse elements.The semi-char exhibits a higher graphitization degree,higher BET surface area,and richer meso-and macropores,which results in superior gasification reactivity than the coal char.The chemical reactivity of the semi-char is significantly improved by an increased gasification temperature,which suggests the necessity of regasification of the semi-char at a higher temperature.Consequently,it will be considered feasible that these carbons in the semi-char from fluidized bed gasifiers are reclaimed and reused for the gasification process.     

Supercritical water gasification of glucose in fluidized bed reactor: A numerical study

Supercritical water fluidized bed (SCWFB) is a new reactor concept for gasification of biomass and coal in supercritical water. In this paper, physical fields, residence time and gas yield in a SCWFB reactor were investigated numerically based on the Eulerian two-fluid method with the kinetic theory of granular flow. A three-step reaction model including steam reforming, water-gas shift and methanation was used to describe the supercritical water gasification of glucose. Distributions of velocity and temperature were obtained, and the results show that the mixing of preheated water and cold glucose solution at the bottom in the bed leads to a region with low solid volume fraction and local swirl flow. In the freeboard, most of reactants flow near the wall and with a velocity much higher than the superficial velocity. The reaction rates and conversion ratio of glucose at different regions in the reactor were also obtained. Distribution of residence time was found to be non-uniform, and its effect on glucose gasification was analyzed. In addition, the effects of operation condition and reactor structure on gas yield and residence time were studied to explore best operation rules for increasing gas yield. The results from this work may be of interest to operators attempting to obtain more information in the reactor and provide instruction for the design of SCWFB reactor.     

Research on the characteristics of biomass gasification in a fluidized bed

The depletion of fossil fuels and the increasing environmental problems, make biomass energy a serious alternative resource of energy. Biomass gasification is one of the major biomass utilization technologies to produce high quality gas. In this paper, biomass gasification was performed in a self-designed fluidized bed. The main factors (equivalence ratio, bed temperature, added catalyst, steam) influenced the gasification process were studied in detail. The results showed that the combustible gas content and the heating value increased with the increase of the temperature, while the CO₂ content decreased. The combustible gas content decreased with the increase of the equivalence ratio (ER), but CO₂ content increased. At the same temperature and at different ratios of CaO (from 0 to 20%), H₂ content was increased significantly, CO content was also increased, CH₄ content increased slightly, but CO₂ content was decreased. With the addition of steam at different temperature, the gas in combustible components increased, the content of H₂ increased obviously. The growth rate was 50% increased. As the bed temperature increased, gas reforming reaction increased, the CO and CH₄ content decreased, but CO₂ and H₂ content increased.     

A numerical model of a fluidized bed biomass gasifier

A one-dimensional, steady state, numerical model was developed for a fluidized bed biomass gasifier. The gasifier model consists of a fuel pyrolysis model, an oxidation model, a gasification model and a freeboard model. Given the bed temperature, ambient air flow rate and humidity ratio, fuel moisture content and reactor parameters, the model predicts the fuel feed rate for steady state operation, composition of the producer gas and fuel energy conversion. The gasifier model was validated with experimental results. The effects of major mechanisms (fuel pyrolysis and the chemical and the physical rate processes) were assessed in a sensitivity study of the gasification model. A parametric study was also conducted for the gasifier model. It is concluded that the model can be used for gasifier performance analysis.