生物质与煤（共）热解/气化过程中挥发分-半焦交互作用研究与进展

生物质和煤协同热化学转化是实现非化石能源和化石能源耦合高效利用的技术手段,对实现“双碳”目标具有重要现实意义。基于生物质等含碳燃料高挥发分组成和富氧特性,热化学转化过程不可避免地发生挥发分-半焦交互作用并影响原料性质和设备过程参数。综述了生物质与煤（共）热解/气化过程中挥发分-半焦交互作用的研究进展,总结了交互作用对挥发分的催化裂解规律、对半焦结构与性质的影响及生物质和煤协同热化学转化下的解耦研究思路三方面具体内容。针对目前挥发分-半焦交互作用机制解析过程所采用的研究方法及思路,提出了新的见解并对未来交互作用的重点研究方向进行了展望,以期为进一步认识交互作用的物理化学本质提供理论指导。     

固定床煤炭压力气化的数学模型

燃料的压力气化是固体燃料重要的热化学过程,藉助于完善的掌握这些过程的方法能够提高其总效能,改善气化过程的结构能够降低原料和动力消耗。煤炭气化和氧化转化方法当能与产生电能相结合时是有利的。Knizia根据气化和发电相结合的方法,其最终产品为煤气和电能提出     

固定床生物质热解气化过程N迁移实验研究

利用管式炉反应器对麦秆(MG)、砂光粉(SGF)、松木(SM)3种生物质进行热解/气化实验,研究了温度(550~950℃)、气氛(Ar、CO_2、CO_2+H_2O)对3种生物质热解/气化过程中N气体(HCN和NH_3)及半焦N生成比例的影响。实验结果表明,3种生物质在Ar下热解气相N产物(HCN+NH_3)生成比例随温度增加而上升且以NH_3为主;550~950℃下HCN的转化率一直增加,NH3的转化率在900℃达最大值;改变气氛对SGF含N气体的转化率影响不明显,H_2O的加入在850~950℃下可促进NH3生成;SGF的燃料N较MG和SM更容易释放,SGF半焦N的质量分数明显低于原料N,MG半焦N与原料N的质量分数基本相等,SM半焦N质量分数比原料显著增加;3种生物质热解气化过程半焦N逐渐减少,气相N逐渐增加,900℃时3种生物质燃料N转化为挥发分N的质量分数大于75.5%,挥发分N中气相N占_26.7%~76.6%。     

挥发分-半焦交互反应对生物质热解半焦特性的影响

挥发分-半焦交互作用是生物质热化学利用过程普遍存在的现象。为了解析交互反应对生物质热解半焦特性的影响,利用一阶固定床/流化床反应器及快速热裂解仪进行实验。针对挥发分-半焦交互反应,对碱金属和碱土金属(AAEM)元素的析出特性展开了研究,同时分析了交互反应对生物质热解半焦反应活性的影响。结果表明在700~900℃范围内,交互反应的存在使得热解成焦率较无交互反应下有所提高。热解过程中交互反应导致了单价K元素析出量增加,对二价Ca/Mg元素的析出影响较小。挥发分-半焦交互反应的存在使得半焦反应活性对温度的敏感度降低,随温度的升高其反应速率的下降幅度变缓。     

不同气氛下褐煤气化特性实验研究进展——新型反应器

丝网、一段或二段式固定床-流化床、燃烧-气化双床及套管反应器等是为褐煤气化过程中某些气化特性(如负压快速热解等)而开发的新型反应器。针对这些新型反应器及其对褐煤气化的研究结果进行总结,分析和讨论了负压快速热解(10000℃/s)特点、半焦与挥发分相互作用、碱金属和碱土金属(AAEMs)的催化作用及粒径对气化影响的双面性(促进/抑制作用)等方面的研究进展。分析认为:挥发分与半焦相互作用对气化过程具有抑制作用,主要由于挥发分重整产生的自由基促使半焦结构缩合,芳香度增大,反应性降低;如何将该抑制作用最小化,是开发新型流化床反应器的切入点;只有吸附在焦炭颗粒表面的高活性的AAEMs可以与半焦官能团等发生离子交换,改变碳颗粒表面的电荷分布,形成活性位,才具有催化作用;然而,煤灰中AAEMs在气化过程中演变复杂,如何将其分解开来,在接近真实气化条件下研究AAEMs的催化作用值得关注;粒径对褐煤气化的影响具有双面性,可以从反应速控步、颗粒孔隙特征及表面化学结构(如官能团等)等方面进行深入研究。     

挥发分-半焦交互反应对生物质热解半焦特性的影响

挥发分-半焦交互作用是生物质热化学利用过程普遍存在的现象。为了解析交互反应对生物质热解半焦特性的影响,利用一阶固定床/流化床反应器及快速热裂解仪进行实验。针对挥发分-半焦交互反应,对碱金属和碱土金属（AAEM）元素的析出特性展开了研究,同时分析了交互反应对生物质热解半焦反应活性的影响。结果表明在700~900℃范围内,交互反应的存在使得热解成焦率较无交互反应下有所提高。热解过程中交互反应导致了单价K元素析出量增加,对二价Ca/Mg元素的析出影响较小。挥发分-半焦交互反应的存在使得半焦反应活性对温度的敏感度降低,随温度的升高其反应速率的下降幅度变缓。     

浅析固定层间歇制气过程中降低燃料消耗的有效途径

在固定层间歇制气过程中，燃料中含有的有效物质(碳)，主要是通过以下几种形式被消耗掉的：吹风过程所燃烧的碳、灰渣中未燃尽的碳、随气体带走尘埃中的碳、转化到半水煤气组成中的碳。其中转化到半水煤气组成中的碳量可称之为有效消耗，但这仅是气化过程中所消耗碳量的一部分，其比值即为碳的有效利用率。     

100t/d气化飞灰预热燃烧锅炉设计与运行

煤气化技术是煤炭梯级利用的主要方式之一,近年来发展迅速、使用广泛。但煤气化过程无法将煤中的碳全部转化利用,煤经过气化后仍有部分可燃物残留在气化飞灰中。其中循环流化床煤气化产生的气化飞灰碳含量相对较高,低位发热量达12~25 MJ/kg,若能加以利用会显著提高碳的利用率。气化飞灰的挥发分极低,传统燃烧技术很难处理。为了实现气化飞灰的高效燃烧,并同时控制燃烧的NO_x排放水平,提出并发展了预热燃烧技术。该技术将气化飞灰在流化床预热燃烧器中进行预热,在缺氧条件下通过化学反应产生热量将燃料自身预热至850~950℃并脱除部分燃料氮,再将预热后的燃料通入煤粉炉炉膛,在炉内通过分级配风实现高效低NO_x燃烧。针对一台采用预热燃烧技术的气化飞灰预热燃烧锅炉,开展调试和工程试验,通过考察预热燃烧器和炉膛内的温度分布和变化规律、气化飞灰的燃烧效率以及NO_x原始排放,研究气化飞灰的预热特性、预热后的高温气固混合燃料的燃烧特性和NO_x排放特性。结果表明,预热燃烧锅炉可以燃用挥发分3%的气化飞灰,锅炉运行稳定,气化飞灰燃烧效率可达98%以上,NO_x原始排放浓度最低可达261.94 mg/m~3,经脱硝处理能达到超低排放。预热燃烧锅炉实现了气化飞灰的高效低氮燃烧,证明了预热燃烧技术在超低挥发分燃料处理方面的可行性和技术先进性。     

德士古和高温温克勒固体燃料气化工艺发展新动向

<正> 1 对先进的固体燃料气化法的几点要求固体燃料气化工艺可转化多种原料,除了煤之外,诸如年青的矿物燃料像泥炭、生物质以及有机废物和重质残渣等均可用作气化原料。煤的固定床、流化床和气流床气化工艺工业化已经几十年了。传统的气化方法有鲁奇加压气化法(固定床)、温克勒法(流化床)和 K-T 法(气流床)等。但是传统的气化法已不能满足在经济和环保方面日益严格的要求,因而到了80年代中期,人们集中精力开发新的气化技术。一个先进的、能满足当前需要的气化技术必须具备下述条件:(1)较高的气化压力;(2)碳转化率高;(3)回收废热生产高压蒸汽;(4)污染物排放量少;(5)运行时间长;(6)操作弹性大(原料性质、负荷变化等)。     

褐煤气化特性的影响因素分析

褐煤是优良的气化原料,开发适合褐煤的新型气化工艺受到各国学者的重视。文章综述了国内外关于褐煤气化的实验研究成果,对各种影响因素进行了分析。褐煤中碱金属和碱土金属的赋存状态,挥发分-焦的相互作用等影响气化反应的各个方面,这些基础研究成果,为开发新型褐煤气化工艺提供参考和理论指导。     

Torrefaction of reed canary grass, wheat straw and willow to enhance solid fuel qualities and combustion properties

Torrefaction is a treatment which serves to improve the properties of biomass in relation to thermochemical processing techniques for energy generation; for example, combustion, co-combustion with coal or gasification. The topic has gathered interest in the past two decades but further understanding is required for optimisation of the process thus enhancing economic efficiency, which is crucial to the success of the treatment commercially and within industry. In particular there is a noticeable gap in current literature regarding the combustion properties of torrefied biomass. This study examines torrefaction in nitrogen of two energy crops, reed canary grass and short rotation willow coppice (SRC), and a residue, wheat straw. Product evolution and mass and energy losses during torrefaction are measured using a range of laboratory scale methods. Experiments at different torrefaction conditions were undertaken to examine optimization of the process for the three fuels. Progress of torrefaction was also followed by chemical analysis (C, H, N, O, ash), and it was seen that the characters of the biomass fuels begin to resemble those of low rank coals in terms of the van Krevelen coal rank parameter. In addition, the results indicate that the volatile component of biomass is both reduced and altered producing a more thermally stable product, but also one that produces greater heats of reaction during combustion. The difference between the mass and energy yield was shown to improve for the higher torrefaction temperatures investigated. The combustion behaviour of raw and torrefied fuels was studied further by differential thermal analysis (DTA) and also, for willow, by suspending individual particles in a methane-air flame and following the progress of combustion by high-speed video. It is shown that both volatile and char combustion of the torrefied sample become more exothermic compared to the raw fuels, and that depending on the severity of the torrefaction conditions, the torrefied fuel can contain up to 96% of the original energy content on a mass basis. Upon exposure to a methane-air flame, torrefied willow ignites more quickly, presumably because its low moisture content means that it heats faster. Torrefied particles also begin char combustion quicker than the raw SRC particles, although char combustion is slower for the torrefied fuel.     

低阶煤热解-气化-燃烧TBCFB系统模拟及优化

三塔式循环流化床（TBCFB）是基于低阶煤分质转化利用理念开发的新型工艺系统,包含热解、气化及燃烧三个主反应器。提出了采用半焦颗粒代替石英砂作为循环热载体的新工艺,并使用Aspen Plus建立了基于半焦颗粒的TBCFB系统模拟流程,寻求系统内物料转化和能量利用的适宜操作条件。结果表明,只需燃烧40%的热解半焦,即可满足低阶煤在600℃热解和60%的热解半焦在800.9℃进行水蒸气气化所需热量;与石英砂或高温灰相比,利用热容较高的半焦颗粒作为循环介质可以显著降低热载体循环量,与原煤质量比仅为5.5。综合气化产物组成、低热值和冷煤气效率等指标,适宜的水蒸气与反应半焦质量比为1.5。上述模拟结果对半焦循环TBCFB新技术的工业应用具有一定指导意义。     

The application of thermal processes to valorise waste tyre

Scrap tyres are a growing environmental problem because they are not biodegradable and their components cannot readily be recovered. In this investigation, the thermochemical recycling of rubber from old tyres by pyrolysis and the value of the products obtained have been studied. First, thermobalance experiments were carried out, studying the influence of the following variables: heating rate, flow rate, particle size and temperature. These thermobalance results were extended by performing experiments in a fixed bed reactor, studying the effect of the main process variables on yields of derived products: oils, gases and solid residue. The oils have been characterized using a combination of analytical techniques (TLC–FID, GC–MS and simulated distillation). No relationship between functional group composition of the oils determined by TLC–FID and process variables was found. The carbonaceous material obtained was characterized by N₂ and CO₂ adsorption. The possible uses of this char have been analyzed taking into account and calculating the emissions that would be produced if the char were burnt.     

煤直接转化制高品质液体燃料和化学品

介绍了国家重点研发计划项目“低变质煤直接转化制高品质液体燃料和化学品的基础研究”的背景、研究现状以及研究任务与目标。研究工作可望在深入认识低变质煤中矿物特性和弱键合结构以及分子水平反应规律、直接转化过程反应途径、产物调控机制及定向催化转化原理;构建高品质和高产率油气的煤热解新反应器、煤加氢液化富产芳烃新工艺、高性能喷气燃料及化学品制备的高效催化剂以及新技术等方面取得突破,从而完善低变质煤直接转化制取高品质液体燃料及化学品的工艺技术体系。     

Thermochemical conversion of fuels into hydrogen-containing gas using recuperative heat of internal combustion engines

The problem of the thermochemical recuperation of heat from the exhaust gases of internal combustion engines (ICEs) as a method of increasing of the efficiency of fuels has been considered. The thermodynamic analysis of thermochemical recuperation conditions was performed, and maximum efficiency conditions were determined. Catalysts for the steam conversion of oxygen-containing fuels into syngas were developed, and the Co-Mn/Al₂O₃ catalyst was shown to be the most promising. The model of a thermochemical heat recuperation system was developed and manufactured, and its bench tests in the conversion of alcohols were performed using the simulated exhaust gases from a heating device. Mathematical models for calculating units of the heat recuperation system were developed. A recuperation system was manufactured and tested in the ICE-free and ICE-integrated variants. Based on the test results, the equivalent fuel consumption characteristics of a recuperative ICE was revealed to decrease by 11–22% depending on its load with a decrease in the concentration of hazardous emissions by 8–12 times for CO, 2–3.5 times for CH, and 18–25 times for NO _x .     

Coproduction of liquid transportation fuels and C6_C8 aromatics from biomass and natural gas

The coproduction of liquid transportation fuels and C₆?C₈ aromatics from the thermochemical conversion of biomass and natural gas (BGTL+C₆_C₈) is investigated in this article. An optimization‐based process synthesis framework incorporating multiple synthesis gas conversion technologies, such as Fischer–Tropsch synthesis or methanol conversion, is described. Production of aromatics can proceed through several technologies, such as naphtha reforming and aromatization of hydrocarbons via a metal‐promoted H‐ZSM‐5 catalyst. This is the first article in the literature to incorporate an aromatics complex for the coproduction of liquid fuels and C₆?C₈ petrochemicals within a rigorous process synthesis and deterministic global optimization framework. The optimal process topologies across several case studies are discussed and the results indicate that the coproduction of aromatics with liquid fuels can significantly increase the profitability of these refineries. © 2015 American Institute of Chemical Engineers AIChE J, 2015 2014 American Institute of Chemical Engineers AIChE J, 61: 831–856, 2015     

A novel hybrid feedstock to liquids and electricity process: Process modeling and exergoeconomic life cycle optimization

This article proposes a novel hybrid low‐rank coal (LRC)/biomass/natural gas process for producing liquid fuels and electricity. The hybrid process highlights coexistence of indirect and direct liquefaction technologies, cogasification of char and biomass, and corefinery of LRC syncrude and Fischer–Tropsch syncrude. A process simulation based on detailed chemical kinetics is present to illustrate its feasibility. In addition, we propose an exergoeconomic life cycle optimization framework that seeks to maximize the primary exergy saving ratio, primary total overnight cost saving ratio, life cycle waste emissions avoidance ratio, and primary levelized cost saving ratio by comparing the proposed hybrid process to its reference stand‐alone subsystems. From the results, we can determine four optimal designs which yield competitive breakeven oil prices ranging from $1.87/GGE to $2.13/GGE. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3739–3753, 2014     

Gasification performance of torrefied Timothy hay and spruce wood chars in a CO2 environment

Timothy hay abundantly available in New Brunswick, Canada, is mostly used for animal feed and bedding. Upgrading biomass using Torrefaction method can offer benefits in its waste management, energy density and energy conversion efficiency. Temperature and residence time play an important role in the torrefaction process. Meanwhile, CO₂ gasification is also a promising thermochemical conversion process due to its potential to reduce net GHG emissions and tune syngas composition. This study investigates the impact of torrefaction parameters on isothermal and non-isothermal CO₂ gasification of Timothy hay and spruce chars. Timothy hay chars exhibited higher CO₂ gasification reactivity than chars from spruce. The physicochemical properties analysis indicated that higher reactivity of Timothy hay char was mainly attributed to the high amount of alkali and alkaline earth metal (AAEM) content, relatively large BET surface area, a high number ofactive sites, and a low crystalline index. Moreover, in both experimental cases, char derived through a high heating rate and high residence time conditions exhibited improved gasification performance, which was attributed to the generation of large amounts of AAEM (Ca and K) and high specific surface area. Co-gasification results during non-isothermal processes under CO₂ showed the presence of larger interactions in coal char/Timothy hay char blends than that of coal char/spruce char blends. For both experimental conditions, interactions were enhanced once the char prepared from high heating rate and high residence time was gasified with coal char. Thus, the proposed approach is a sustainable way of conversion of Timothy hay under CO₂ environment.     

Recent Developments in the Conversion of Biomass to Renewable Fuels and Chemicals

The rapid and ongoing increase in consumption of petroleum for transportation fuels, chemicals and energy is not sustainable. Therefore, development of technology that uses agricultural, animal, forestry and municipal solid waste as renewable feedstock is critical to the US economy and national security, and presents a significant opportunity for new catalysis, chemistry and process research. This paper will outline recent developments on the conversion of biomass to renewable fuels and chemicals with emphasis on new opportunities for thermochemical catalysis.