Insight into the ammonia torrefaction and pyrolysis system of cellulose:Unraveling the evolution of chemical structure and nitrogen migration mechanism

This study aimed to investigate the mechanism of nitrogen doping,migration,and conversion during ammonia torrefaction and also explore the evolution law of the chemical structure of cellulose.The results showed that the ammonia torrefaction pretreatment could significantly optimize the distribution of nitrogen and oxygen elements in cellulose.The carbon skeleton first captured the active nitrogenous radicals to form-NHn-N,and pyridine-N and pyrrole-N originated from the conversion of-NHn-N.The existence of C=O played a major role in the immobilization of nitrogen.The nitrogen in bio-oil exists mainly in the form of five-and six-membered heterocycles.The correlation analysis showed that the main precursors for the formation of nitrogenous heterocyclic compounds were five-membered Oheterocyclic compounds.Finally,the product distribution characteristics in the torrefaction-pyrolysis systems were summarized,and the nitrogen doping and conversion mechanisms were proposed.This study expanded the boundaries of cellulose pretreatment and the production of high-value chemicals.

Effects of Microwave Torrefaction with Mg（OH）2 on Characteristics of Bio-oil from Co-pyrolysis of Straw Stalk and Soapstock

This study investigated the effects of torrefaction with Mg(OH)2 on the properties of bio-oil formed from the microwave-assisted catalytic fast co-pyrolysis of straw stalk and soapstock.The effects of torrefaction temperature and residence time on the yield and composition of bio-oil were discussed.Results showed that the torrefaction temperature and residence time remarkably influenced the yield and composition of bio-oil.With the increase in temperature and time,the bio-oil yield and the proportion of oxygen-containing compounds decreased,while the proportion of aromatic compounds increased.When the feedstocks were subject to torrefaction reaction for 20 min at 260°C,the proportion of oxygen-containing compounds decreased from 29.89%to 16.49%.Meanwhile,Mg(OH)2 could render the deoxidization function of torrefaction process increasingly noticeable.The proportion of the oxygen-containing compounds reached a minimum(14.41%),when the biomass-to-Mg(OH)2 ratio was 1:1.

Upgraded Pellet Making by Torrefaction—Torrefaction of Japanese Wood Pellets

Upgraded wood pellets were produced and evaluated by torrefaction of wood pellets. In this study, conventional wood pellets were initially prepared and subsequently torrefied on a laboratory and then larger scale. During the laboratory scale production, pellets from wooden parts of Japanese cedar (sugi, Cryptomeria japonica) and Japanese oak (konara, Quercus serrata) trees were heat- treated in an inert gas oven under nitrogen atmosphere around 170°C - 320°C. For the Japanese cedar, the calorific values were improved by heat treatment up to 260°C. By heat treatment at 240°C, the upgrade ratio of higher heating value (HHV) was nearly 30% and the energy yield was 97%. For the Japanese oak, the calorific values were improved by heat treatment up to 320°C. By heat treatment at 280°C, the upgrade ratio of HHV exceeded 30% and the energy yield was 84%. On a larger scale, a conventional charcoal oven was modified for torrefied wood pellet production, meaning that torrefied wood pellet with 25 MJ/kg of calorific value was produced during heat treatment at 350°C. A mixture of conventional and torrefied pellets was applied to a commercial pellet stove, and torrefied wood pellets produced in this study might be usable as fuel for conventional pellet stoves.

Fundamental Study on the Production of ＂Hyper Wood Pellet＂——Effect of Torrefaction Condition on Grinding and Pelletizing Properties

In order to upgrade the conventional wood pellet, Japanese softwood and hardwood chips were torrefied at around 200-350℃, and pelletized. The characteristics of the torrefied material/pellets such as their calorific value, grinding energy, pelletizing energy and elemental composition, were also evaluated in this study. The calorific value rose with increasing torrefaction temperature and exceeded 25 MJ/kg （an increase of nearly 40% compared to the untreated state） for torrefaction at around 350℃. The grinding energy greatly decreased with increasing torrefaction temperature, and the reduction was larger for Japanese oak hardwood chips. The pelletization energy for the torrefied material tended to be slightly smaller than in the untreated case. People named such torrefied pellet as ＂hyper wood pellet＂.

Recent Advance on Torrefaction Valorization and Application of Biochar from Agricultural Waste for Soil Remediation

With the increase of global proportion of soil pollution and the number of areas at risk,researchers have sought to develop various pathways to repair or relieve the pollutants in soil.Among them,biochar represents one multi-dimensional soil amendment which has got great deal of attention on its physicochemical properties towards the removal or mitigation of contaminants in soil.A variety of agricultural wastes like straw and manure prepared from different torrefaction process have been employed as feedstock for the production of biochar,which can be applied to the contaminated soil to facilitate the growing environment for crops,and to improve soil fertility and microbial environment.In addition,the utilization of biochar for soil remediation is also considered as a pro-cess of carbon sequestration.The purpose of this review is to summarize the latest research progress in torrefac-tion processes and mechanism of agricultural waste,the effects of different torrefaction methods on the formation and properties of biochar were explained,coupled with the effects of process parameters.Especially,the conver-sion and mechanisms of biochar prepared from agricultural wastes composed mainly with lignocellulosic material were discussed,and the characteristics of biochar prepared for improving soil physical and chemical character-istics,microbial community characteristics,nutrients,and the stability and relief of soil pollutants,especially heavy metals,are compared.Finally,this work discussed the application and future technical challenges of soil remediation based on agricultural waste derived biochar.

Impacts of Torrefaction on PM_(10) Emissions from Biomass Combustion

Typical biomass torrefaction is a mild pyrolysis process under conditions of ordinary pressure,low temperature(200–300°C)and inert atmosphere.Torrefaction is considered to be a competitive technology for biomass pretreatment,but its impacts on the emissions of particulate matter from biomass combustion are worthy of further study.In this paper,three kinds of biomass,i.e.,bagasse,wheat straw and sawdust were selected for torrefaction pretreatment and the impacts of torrefaction on the emission characteristics of PM_(10) from biomass combustion were investigated.The combustion experiments were carried out on a drop tube furnace.The combustion-generated particulate and bulk ash samples were collected and subjected to analyses by various techniques.The results show that torrefaction tends to result in a reduction of PM_(1)(particulates with an aerodynamic diameter less than 1μm)emissions from combustion,but the extent of reduction is dependent on biomass type.The reduction of PM_(1) from the combustion of torrefied biomass is mainly because that the torrefaction process removes some Cl and S from the biomass,thereby suppressing the release of alkali metals and the emissions of PM_(1) during the combustion process.As for PM_(1–10)(particulates with an aerodynamic diameter within 1–10μm),its emissions from combustion of torrefied biomasses are consistently reduced,compared with their untreated counterparts.This observation is primarily accounted for the enhanced particle coalescence/agglomeration in combustion of torrefied biomasses,which reduces the emissions of PM_(1–10).

Design and Testing of a Solar Torrefaction Unit to Produce Charcoal

With increasing crude oil prices, fuels like kerosene and cooking gas have become unaffordable for many ordinary people in developing countries. For millions of Africans who need heat energy to cook their food, biomass like wood remains the easiest and cheapest source of fuel. Charcoal remains the most popular choice compared to wood since it can cook food much faster with very little smoke. Torrefaction of biomass is a mild form of pyrolysis at temperatures typically between 200℃ and 300℃ to produce charcoal. Torrefaction changes biomass properties to provide a much better fuel quality for combustion applications. A simple parabolic trough solar collector to produce charcoal by torrefaction process using solar energy has been designed from first principles. The device was fabricated and various locally available wood species were tested. The yield was found to be 21% to 35% with a production time of 90 minutes. The paper details the design procedure and the test results.

基于热重-质谱分析的榆木/低阶煤共热解特性研究

为了研究烘焙对共热解行为的影响,以榆木(E)、250℃烘焙后榆木(E_(T250))和低阶煤(L)为原料,利用热重-质谱联用分析仪(TG-MS)进行榆木/低阶煤不同质量比例下(1∶1、1∶3、3∶1)的共热解实验。TG分析结果表明,相比E和E_(T250),L热解需要更高的温度和更长的时间;但当将生物质与低阶煤共热解后,共热解所需的温度和时间都随着生物质质量比的增加而减小;在共热解过程中,E与L的失重特性曲线相互影响,而E_(T250)在热解过程中与L的失重特性基本一致,说明经250℃烘焙后榆木与低阶煤的品质相似。

生物质气压烘焙技术研究进展

气压烘焙技术具备反应条件温和、能耗低、脱氧效率高、能量回收率高、半焦燃料品质近似次烟煤等优势,是一种有希望替代传统烘焙的新型技术之一。本文介绍了气压烘焙的发展脉络,综述了气压烘焙工况优化(包括原料种类、温度、压力、时间)、产物组成与理化特性,阐述了气压烘焙宏观反应路径和微观反应机理,着重介绍了半焦的燃烧、热解、气化利用途径,回顾了气压烘焙的反应器设计及其在含氯固废、污泥等处置中的拓展。最后对气压烘焙技术可将生物质转化为高品质固体燃料,直接替代煤炭进行了总结和展望。

木质纤维生物质烘焙预处理研究进展

综述了烘焙过程的反应机制和烘焙动力学,分析了烘焙温度、停留时间、升温速率、烘焙气氛等因素对生物质理化特性的影响,探讨了烘焙对生物质后续热解、燃烧、气化的影响。烘焙温度是烘焙过程最主要的影响因素,不同烘焙气氛可以改变烘焙产物分布。烘焙气氛除惰性氮气外,其他气氛如O_(2)、CO_(2)、烟气和NH_(3)等也被应用。烘焙动力学研究有利于揭示烘焙生物质的热降解行为。将烘焙与热解、气化、燃烧等工艺相结合可以获得高品质的生物油和富含氢气的合成气,提高生物质能源的利用效率。对木质纤维生物质烘焙预处理技术从烘焙气氛、集成优化和规模化等方面进行了展望。

生物质干法烘焙技术开发及工业化应用现状

烘焙提质技术是一种轻度热解技术,可有效降低生物质的含水率和O/C比,提高能力密度和可磨性,延长储存时间,最为前置处理技术,对热解、气化、燃烧等工艺有很好的辅助作用。本文主要介绍了国内外生物质干烘焙技术开发及工业化进展,详细论述了技术类别,各自优缺点以及工业化应用情况。最后,展望了干烘焙技术未来发展方向。

有氧烘焙对生物质气化及碱金属迁移转化特性的影响

本工作研究了有氧烘焙对玉米秸秆组成成分、烘焙产率、化学结构及微观结构等理化特性及气化特性的影响,同时考察了玉米秸秆烘焙及气化过程中碱金属的迁移转化规律。结果表明,烘焙可有效提高玉米秸秆中固定碳含量,降低H/C、O/C。相较于惰性烘焙,有氧烘焙具有更好的提质效果,结合H/C、O/C、质量产率和能量产率发现,氧气体积分数为6%时较合适。烘焙玉米秸秆气化气中CO含量、气体产率及热值随烘焙气氛中氧气含量的增加呈先上升后下降的趋势,在氧气体积分数为6%时气化品质相对较好,此时气体组分中CO体积分数为14.73%、气体产率达到1.09 L/g、气体热值达到4.93 MJ/m3。烘焙过程中碱金属在玉米秸秆中富集,并促进部分水溶态钾向醋酸铵溶态钾转化,有助于气化过程中生成更多不溶态钾,且有氧烘焙促进作用更明显。研究结果可为生物质有氧烘焙提质及气化产气的技术推广提供基础数据及技术支持。

烘焙预处理对微藻化学链气化特性的影响研究

为了解决微藻含水率高、能量密度低等缺点,提高微藻化学链气化特性,该文以微藻为研究对象,对其在200℃、250℃和300℃下进行烘焙预处理。通过热重分析法进行以Al_(2)O_(3)、Fe_(2)O_(3)、Ca_(2)Fe_(2)O_(5)为载氧体的微藻化学链气化特性研究,探究了烘焙预处理和载氧体对微藻的气化特性和动力学参数的影响。结果表明,经过烘焙预处理后微藻的氧碳原子比和氢碳原子比均显著降低,分别从1.68和0.436降低到1.11和0.139,C含量和高位热值均显著提高。在微藻化学链气化过程中,烘焙预处理和载氧体(Fe_(2)O_(3)、Ca_(2)Fe_(2)O_(5))的添加均可提高微藻化学链气化反应速率。通过反应动力学分析可知,烘焙微藻的化学链气化反应活化能低于原始微藻的活化能。这表明,烘焙预处理有助于提高微藻的化学链气化特性。

烘焙棉秆的成型特性影响研究及工艺优化

文章以棉花秸秆为研究对象,对其进行烘焙预处理以提升燃烧特性与热值并降低粉碎能耗。采用单因素实验研究了成型压力、成型温度和原料含水率对烘焙棉秆成型燃料的松弛密度、吸湿性和抗压强度3个特性评价指标的影响。基于单因素实验开展了正交实验,探讨三者间的相互作用并对热压成型过程进行工艺优化。结果表明:烘焙预处理提高了棉秆的燃烧稳定性及粉碎效率,烘焙棉秆的粉碎能耗与棉秆原样相比降低了66.6%;在烘焙棉秆的热压成型过程中,成型燃料的特性评价指标在合适的压力范围内(3~23 kN)均随着成型压力的增大逐渐提升;而随着成型温度和原料含水率的增加,特性评价指标均呈现先上升后下降的趋势,并分别在成型温度为115℃和含水率为9%时出现拐点。根据正交实验得出烘焙棉秆热压成型的最佳工艺条件:压力为18 kN,温度为100℃,含水率为9%,此时制得的成型燃料的松弛密度、抗压强度和吸湿性分别达到1.220kg/m3,8.17 MPa和8.45%,完全符合我国生物质颗粒燃料的行业标准。

生物质烘焙提质技术与应用研究进展

生物质烘焙是一项重要的低温预处理技术,对于生物质气化等多种工艺均有较好的辅助作用,烘焙技术耦合现有生物质利用技术具有重要的节能和环保意义。本文主要总结生物质烘焙技术的类别特点和研究现状,分析烘焙技术在生物质成型燃料、生物质气化、垃圾焚烧发电等多种领域的应用前景,并展望烘焙技术未来的发展方向。

烘焙预处理对玉米秸秆气化产物特性的影响

我国生物质资源丰富,是一种清洁可再生的原料,通过生物质气化技术将其转化为可燃气,用于替代燃煤和天然气供热或发电,对我国实现“碳达峰”和“碳中和”的“双碳”目标具有重要意义。然而,生物质原料存在含水率高、含氧量高及热值低等缺点,导致气化可燃气存在热值低和焦油含量高的缺陷,使得利用农林废弃生物质“变废为宝”面临较大挑战。选取玉米秸秆为原料,首先采用程序控温管式炉对其进行烘焙预处理,并用元素分析、工业分析、X射线衍射仪、傅里叶红外光谱仪、热重分析仪等仪器对其基本物理化学特性进行分析;其次,采用自制的小型固定床气化炉装置,研究烘焙预处理温度对玉米秸秆气化可燃气、炭和焦油产物产率和特性的影响。研究结果表明,随着烘焙温度的升高,玉米秸秆的O质量分数及挥发分明显降低,C质量分数与固定碳显著增加,使得热值从17.26 MJ/kg增加至25.50 MJ/kg;烘焙温度对气化产物的质量产率和特性也有显著的影响。随着烘焙温度的升高,可燃气的质量产率逐渐下降,H2的体积分数从13.85%大幅增加到22.56%,可燃气的低位热值在烘焙温度为220℃时达到最高值,为9.36 MJ/Nm^(3)。较高的烘焙温度导致气化残炭的质量产率上升,并且气化残炭中的C元素与固定碳增加,而挥发分与灰分减少,热值从22.74 MJ/kg增加至24.52 MJ/kg。较高的烘焙温度使得焦油的质量产率从21.07%大幅下降至12.67%,焦油组分主要由芳烃类、酚类及脂肪烃类组分构成,其中芳烃类物质与酚类物质的质量分数较高,随烘焙温度升高,芳烃类物质的质量分数先增加后减少,而酚类物质质量分数先减少后增加,其他脂肪烃物质质量分数变化规律不明显。因此,烘焙预处理可显著改善玉米秸秆的品质,进而提升气化可燃气的热值,降低焦油含量。

低温烘焙提质对褐煤着火燃烧特性的影响

褐煤高水分和高挥发分不利于运输和储存,且会降低锅炉燃烧效率,低温烘焙提质作为一种褐煤提质常用技术,能有效降低燃料中水分并提升燃料品质,显著改变褐煤燃烧特性。为研究低温烘焙提质对褐煤着火特性的影响,利用平面火焰燃烧系统并结合CMOS相机研究了不同热协流温度(1 473、1 673和1 873 K)和O_(2)体积分数(5%、10%和20%)下低温烘焙预处理(200、250和300℃)对褐煤着火燃烧特性的影响,并分析低温烘焙提质对着火延迟距离和火焰亮度的影响。结果表明,经低温烘焙预处理的褐煤颗粒在相同热协流温度和O_(2)浓度条件下的着火延迟距离稍大于原始褐煤颗粒;O_(2)体积分数为5%时,200℃烘焙褐煤的着火延迟距离在热协流温度1 473、1 673和1 873 K时较原始褐煤颗粒分别增加了0.24、0.28和0.13 cm;此外,不同烘焙温度下煤粉颗粒的着火位置较褐煤均有所延迟,且升高烘焙温度会降低褐煤着火距离,在1 673 K、O_(2)体积分数5%下,烘焙温度200、250和300℃时对应的着火延迟距离较褐煤的增加值分别为0.28、0.16和0.11 cm。

烟气烘焙对玉米秆可磨性的影响规律研究

可磨性是生物质在现有燃煤机组规模化燃烧利用中必须考虑的问题之一。本文基于固定床反应器对玉米秆进行烘焙预处理,针对生物质单烧和与煤混烧两种技术路线,利用臼式研磨仪、全自动粒径筛分仪、纤维素分析仪和傅里叶红外光谱,研究了不同烘焙气氛、温度对燃料可磨性的影响。结果表明,相比于氮气,烟气能够在更低的烘焙温度下使玉米秆可磨性提升至接近于典型动力用煤,主要是由于烟气中的氧化性组分促进了纤维素、半纤维素的分解。当共磨时,煤颗粒表现出助磨的作用提升了玉米秆的可磨性,在较高温度或烟气烘焙条件下,混样的可磨性近似甚至优于煤。

杨木湿法烘焙预处理耦合金属改性多级孔分子筛催化热解制取轻质芳烃

轻质芳烃是化工领域重要的基础有机原料,生物质催化热解的技术路线可制取生物基的轻质芳烃化学品。首先,采用湿法烘焙预处理,对杨木进行协同脱氧和脱灰改性提质;其次,采用NaOH脱硅预处理和负载活性金属(Zn、Ga和Fe),对微孔HZSM-5进行修饰改性,构建金属改性多级孔HZSM-5催化剂,并将其用于湿法烘焙杨木催化热解,研究烘焙温度、催化剂改性、催化剂与原料质量比和热解温度等参数对轻质芳烃产率的影响。结果表明,随着湿法烘焙温度的升高,杨木的脱氧率和碱/碱土金属脱除率逐渐增加,其中,O、K、Mg、Ca和Na的最大脱除率分别为47.96%、90.99%、86.65%、66.09%和36.29%。与HZSM-5相比,采用NaOH脱硅后的多级孔HZSM-5(Hie-H)及金属改性的多级孔HZSM-5(Ga/Hie-H、Zn/Hie-H和Fe/Hie-H),均促进了轻质芳烃的形成,其中,Zn/Hie-H对杨木湿法烘焙后固体产物催化热解制取轻质芳烃产率最高;在湿法烘焙温度为220℃,Zn/Hie-H与烘焙杨木质量比为3∶1,热解温度为850℃时,轻质芳烃的产率达到最大值,为7.83×107p.a./mg。

不同含氧气氛下生物质烘焙预处理研究进展

通过文献综述,研究了不同含氧气氛下生物质烘焙预处理研究进展。介绍了二氧化碳、烟气、空气、一定比例氧气、蒸汽、氨气、真空环境、无外部气氛供应环境等含氧气氛中生物质烘焙预处理在质量产率、能量产率、元素和工业分析、热值、热反应特性、吸湿和研磨等方面的性能;对比分析了上述有氧气氛烘焙预处理与惰性气氛烘焙预处理的性能差异;提出了目前仍需进一步深化研究的科学问题,以期为后续科学研究和生产推广提供参考,为拓展生物质高质化利用提供途径。