生物质与煤共气化特性研究

在热天平装置中研究了生物质焦、煤焦以及生物质焦与煤焦混合物的水蒸气气化特性.采用程序升温热重法对生物质焦(稻秆焦、高粱秆焦和玉米秆焦)、神木煤焦以及生物质焦与煤焦混合物进行了水蒸气气化实验.结果表明,生物质焦和煤焦在一定温度下的气化速率为:高粱焦＞稻秆焦＞玉米焦＞神木煤焦.并对三种生物质焦、煤焦、生物焦和煤焦混合物的水蒸气气化反应进行了动力学分析,分析认为,连续反应模型可以在一定程度上反应焦样的水蒸气气化反应动力学.     

基于CoFe_2O_4载氧体的生物质化学链气化反应特性

在热重分析仪和固定床反应器上对基于CoFe_2O_4载氧体的生物质化学链气化反应特性进行了研究,考察了载氧体与生物质质量比、水蒸气、反应温度对生物质化学链气化反应特性的影响,同时也对载氧体的循环反应性能进行了研究。通过XRD及SEM对新制备的和反应后的载氧体进行了表征。热重结果表明:CoFe_2O_4能够提供晶格氧,有效促进生物质气化。当CoFe_2O_4与生物质质量比为0.8,水蒸气体积分数为50%,温度为900℃时,气化反应效果最好。5次循环反应后,仍能获得较高品质的合成气,载氧体能够循环再生且未出现明显烧结团聚。     

高温水蒸气生物质催化气化的研究进展

在粮食加工副产物资源化利用的背景下,生物质气化技术成为生物质利用研究的重点内容。生物质气化技术的发展和应用,对推动生物质利用的节能化、环保化发展有着重要的意义。主要论述了高温水蒸气生物质催化气化的相关内容。     

生物质型煤气化行为实验研究

以被称为"十大害草"之一的水葫芦为生物质资源,与福建低活性无烟煤混合制备成生物质型煤.在内径为28 mm小型固定床气化反应器中对生物质型煤气化行为进行了实验测定.通过对3组不同生物质配比的型煤分别进行不同时间的气化,考察了生物质型煤气化行为演变过程行为.结果显示,型煤在气化过程中形成较为明显的灰层与未反应的芯层界面,且随着生物质配比的增加,灰层迁移速度较快,气化时间缩短,表明添加生物质有利于提高福建生物质型煤的气化活性.     

基于CoFe2O4载氧体的生物质化学链气化反应特性

在热重分析仪和固定床反应器上对基于CoFe₂O₄载氧体的生物质化学链气化反应特性进行了研究，考察了载氧体与生物质质量比、水蒸气、反应温度对生物质化学链气化反应特性的影响，同时也对载氧体的循环反应性能进行了研究。通过XRD及SEM对新制备的和反应后的载氧体进行了表征。热重结果表明：CoFe₂O₄能够提供晶格氧，有效促进生物质气化。当CoFe₂O₄与生物质质量比为0.8，水蒸气体积分数为50%，温度为900 ℃时，气化反应效果最好。5次循环反应后，仍能获得较高品质的合成气，载氧体能够循环再生且未出现明显烧结团聚。     

生物质下吸式气化炉气化制备富氢燃气实验研究

以制取富氢燃气为目标,在自热式下吸式气化炉反应器内,进行了生物质下吸式气化炉富氧/水蒸气及空气气化的制氢特性研究。实验结果表明,与空气气化相比,富氧/水蒸气气化可显著提高氢产率和产气热值。在实验条件范围内,最大氢产率达到45.16 g/kg;最大低位热值达到11.11 MJ/m3。在富氧/水蒸气气化条件下,燃气中H2+CO体积分数达到63.27%—72.56%,高于空气气化条件下的52.19%—63.31%。富氧/水蒸气气化条件下的H2/CO体积比比值为0.70—0.90,低于空气气化条件下的1.06—1.27。实验结果证实:生物质下吸式气化炉富氧/水蒸气气化是一种有效的制取可再生氢源的工艺路线。     

生物质气化制取合成气的模拟

阐述了利用串行流化床制取生物质合成气的技术,该技术将生物质气化过程与燃烧过程分开,气化反应器和燃烧反应器之间通过床料进行热量传递,并通过生物质补燃实现自供热。利用ASPEN PLUS软件建立了串行流化床制取合成气的模型,通过将模拟数值与实验结果相比较,验证了模拟研究的可行性。重点研究了气化温度、水蒸汽与生物质的质量配比(S/B)对制取生物质合成气的影响。结果表明,为获取较高品质的生物质合成气并得到较高的碳转化率、气化份额和合成气产率,气化温度以650～800℃为宜,S/B应在0.2～1.0之间。     

固体热载体外循环逆流移动床生物质气化工艺

基于实验室外循环逆流移动床(ECCMB)催化气化反应体系进行了生物质气化实验研究。该反应系统由移动床热解反应器、气固逆流移动床气化反应器和提升管燃烧反应器组成。以白松木屑为生物质原料、煅烧橄榄石为热载体(催化剂)进行气化实验,考察了热解器温度、水蒸气质量/生物质质量(S/B)、原料粒度以及气化器床层高度对气化结果的影响。实验结果表明:反应器温度和S/B是影响气化产品分布的重要因素;随热解温度的升高,气体产率和化学效率显著提高,氢气含量也有所增加;水蒸气的加入不仅提高了产气率,焦油含量明显降低;原料颗粒粒度和气化器床层高度均对产品分布和化学效率产生不同程度的影响。     

典型生物质的水蒸气气化特性研究

设计了生物质气化工艺流程,探究生物质气化的最佳工艺条件。以贵州核桃壳、玉米秸秆、稻壳为原料,N2为保护气,水蒸气为气化剂,探究气化时间、水蒸气流量、反应物质量和气化温度对气化率的影响,得出玉米秸秆、核桃壳、稻壳的最佳质量分别为5 g、4 g、2 g;最佳气化温度分别为700℃、650℃、600℃;最佳反应时间分别为240 s、420 s、240 s;最佳水蒸气流量分别为132.8 mL/h、177.15 mL/h、88.5 mL/h。玉米秸秆、核桃壳、稻壳都是气化时间越长,气化率越高。核桃壳、玉米秸秆、稻壳的CO含量最高分别为28.82%、39%、16.8%;核桃壳、稻壳、玉米秸秆的H2含量最高分别为42.71%、30.8%、7.81%,核桃壳中含有大量的CO和H₂。     

生物质水蒸气气化制取富氢合成气及其应用的研究进展

生物质水蒸气气化是有效的热化学转化手段,可将原材料转化为富氢合成气,气体应用更加广泛,有替代化石能源制氢的潜在价值。不同的生物质资源气化和产氢能力存在差异,物料的选择对气化制取富氢合成气至关重要,而调整气化操作参数包括反应温度、水蒸气加入量、催化剂和吸收剂等可进一步优化合成气质量,提升氢气含量。本文首先综述了不同操作条件对生物质水蒸气气化制取富氢合成气的影响。其次,介绍了生物质炭气化制取富氢合成气的研究现状,炭气化可制得高品质的富氢合成气,但过程受动力学限制,需要加入催化剂以提升炭气化速率。文中还简述了以钾盐为催化剂时的催化机理,并展望了富氢合成气的应用,包括制备高纯氢应用于燃料电池和制备合成天然气。     

气化剂参数对流化床生物质气化指标影响的模型研究

以典型生物质资源麦秆为原料,采用流化床气化方法,通过建立热力学平衡模型,计算并分析气化剂参数对气化指标的影响,理论优化了以蒸汽+空气为气化剂时的气化指标,得出了空气中氧气浓度的增加能够显著提高气化指标,降低消耗;气化剂预热温度的增加可以增加气化炉操作温度,降低气化过程无用的热负荷,降低消耗;空气中氧气浓度和蒸汽/空气质量比与气化反应温度近似成线性关系,即氧气浓度增加,气化炉温度增加,蒸汽/空气质量比增加,气化炉温度降低;蒸汽/空气质量比能够调节气化炉反应温度和气体组成,当该值在0.05时,气化温度为1 270 K,合成气中CO+H2+CH4体积分数为25.7%,气化指标较好。     

Biomass Gasification Integrated with Chemical Looping System for Hydrogen and Power. Coproduction Process – Thermodynamic and Techno‐Economic Assessment

Three biomass gasification‐based hydrogen and power coproduction processes are modeled with Aspen Plus. Case 1 is the conventional biomass gasification coupled with a shift reactor, cases 2 and 3 involve integration of biomass gasification with iron‐based and calcium‐based chemical looping systems. The effects of important process parameters on the performance indicators such as hydrogen yield and efficiencies are evaluated by sensitivity analyses. These parameters include gasification temperature, molar ratios of steam to biomass in the gasifier, Fe₂O₃ to syngas in the fuel reactor, Fe/FeO to steam in the steam reactor, CaO to CO, and steam to CO in the carbonator. The energy and exergy balance distributions for the above three cases are comprehensively discussed and compared. Furthermore, techno‐economic assessments are performed to evaluate the three cases in terms of capital cost, operating cost, and leveled cost of energy.     

An Experimental Investigation of Hydrogen Production from Biomass

In gaseous products of biomass steam gasification, there exist a lot of CO, CH4 and other hydrocarbons that can be converted to hydrogen through steam reforming reactions. There exists potential hydrogen production from the raw gas of biomass steam gasification. In the present work, the characteristics of hydrogen production from biomass steam gasification were investigated in a small-scale fluidized bed. In these experiments, the gasifying agent (air) was supplied into the reactor from the bottom of the reactor and the steam was added into the reactor above biomass feeding location. The effects of reaction temperature, steam to biomass ratio, equivalence ratio (ER) and biomass particle size on hydrogen yield and hydrogen yield potential were investigated. The experimental results showed that higher reactor temperature, proper ER, proper steam to biomass ratio and smaller biomass particle size will contribute to more hydrogen and potential hydrogen yield.     

浅谈尿素装置闪蒸蒸汽的节能利用

在水溶液全循环法尿素工艺中,闪蒸槽产生的0.36 MPa(绝)蒸汽用于保温伴热,多余的蒸汽外供造气。由于这部分蒸汽在使用过程中热能损失巨大,笔者探讨性地提出了将1级闪蒸得到的0.63 MPa(绝)蒸汽用于吸解系统,2级闪蒸得到的0.36 MPa(绝)蒸汽用于保温伴热和外供造气的节能改造方案;进行了1级闪蒸和2级闪蒸的模拟分析计算和解吸塔热平衡计算;分析论证了2级闪蒸槽蒸汽用气的经济性;结果表明,1级闪蒸蒸汽用于解吸系统不仅可行且经济效益显著,2级闪蒸蒸汽可以满足造气系统的使用条件。     

Flowsheet Modeling and Simulation of Biomass Steam Gasification for Hydrogen Production

Hydrogen production from biomass steam gasification is systematically reviewed. Equilibrium modeling and simulation studies using various techniques for effective hydrogen production are presented. Heat integration, economic analysis of the hydrogen production, and systematic design algorithms research publications are overviewed and discussed for energy-efficient and economic hydrogen production from various biomass feedstocks. Comparison and analysis of the results strongly suggest the viable potential of biomass steam gasification for hydrogen production from small to large scales with applications for thermal heat, power generation, and many other industrial fields.     

The study of reactions influencing the biomass steam gasification process☆

Steam gasification studies were carried out in an atmospheric fluidised bed. The gasifier was operated over a temperature range of 700-900 °C whilst varying a steam/biomass ratio from 0.4 to 0.85 w/w. Three types of forestry biomass were studied: Pinus pinaster (softwood), Eucalyptus globulus and holm-oak (hardwood). The energy conversion, gas composition, higher heating value and gas yields were determined and correlated with temperature, steam/biomass ratio, and species of biomass used. The results obtained seemed to suggest that the operating conditions were optimised for a gasification temperature around 830 °C and a steam/biomass ratio of 0.6-0.7 w/w, because a gas richer in hydrogen and poorer in hydrocarbons and tars was produced. These conditions also favoured greater energy and carbon conversions, as well the gas yield. The main objective of the present work was to determine what reactions were dominant within the operation limits of experimental parameters studied and what was the effect of biomass type on the gasification process. As biomass wastes usually have a problem of availability because of seasonal variations, this work analysed the possibility of replacing one biomass species by another, without altering the gas quality obtained.     

Comparison of dual fluidized bed steam gasification of biomass with and without selective transport of CO2

A comparison of dual fluidized bed gasification of biomass with and without selective transport of CO₂ from the gasification to the combustion reactor is presented. The dual fluidized bed technology provides the necessary heat for steam gasification by circulating hot bed material that is heated in a separate fluidized bed reactor by combustion of residual biomass char. The hydrogen content in producer gas of gasifiers based on this concept is about 40 vol% (dry basis). Addition of carbonates to the bed material and adequate adjustment of operation temperatures in the reactors allow selective transport of CO₂ (absorption enhanced reforming—AER concept). Thus, hydrogen contents of up to 75 vol% (dry basis) can be achieved. Experimental data from a 120 kW_{Fuel input} pilot plant as well as thermodynamic data are used to determine the mass- and energy-balances. Carbon, hydrogen, oxygen, and energy balances for both concepts are presented and discussed.     

Process modeling for parametric study on oil palm empty fruit bunch steam gasification for hydrogen production

Biomass steam gasification with in-situ carbon dioxide capture using CaO exhibits good prospects for the production of hydrogen rich gas. The present work focuses on the process modeling for hydrogen production from oil palm empty fruit bunch (EFB) using MATLAB for parametric study. The model incorporates the reaction kinetics calculations of the steam gasification of EFB (C_3.4H_4.1O_3.3) with in-situ CO₂ capture, as well as mass and energy balances calculations. The developed model is used to investigate the effect of temperature and steam/biomass ratio on the hydrogen purity, yield and efficiency. Based on the results, hydrogen purity of more than 76.1 vol.% can be achieved. The maximum hydrogen yield predicted at the outlet of the gasifier is 102.6 g/kg of EFB. It is found that increment in temperature and steam/biomass ratio promotes hydrogen production. However, it is also predicted that the efficiency decreases when using more steam. Due to the still on-going empirical work, the results are compared with published literatures on different systems. The comparison shows that the results are in agreement to some extent due to the different basis.