Supercritical fluids technology for clean biofuel production

Biofuels are liquid or gaseous fuels that are predominantly produced from biomass for transport sector applications.As biofuels are renewable,sustainable,carbon neutral and environmentally benign,they have been proposed as promising alternative fuels for gasoline and diesel engines.This paper reviews state-of-the-art application of the supercritical fluid(SCF)technique in biofuels production that includes biodiesel from vegetable oils via the transesterification process,bio-hydrogen from the gasification and bio-oil from the lique-faction of biomass,with biodiesel production as the main focus. The global biofuel situation and biofuel economics are also reviewed.The SCF has been shown to be a promising technique for future large-scale biofuel production,especially for biodiesel production from waster oil and fat.Compared with conventional biofuel production methods,the SCF technology possesses a number of advantages that includes fast inetics,high fuel production rate,ease of continuous operation and elimination of the necessity of catalysts.The harsh operation environment,i.e. the high temperature and high pressure,and its request on the materials and associated cost are the main concerns for its wide application.     

合成气发酵的质量传递限制研究进展

合成气是木质纤维素等生物质部分氧化和高温分解后的混合气化,被生物催化剂厌氧发酵后可以转化为一些有价值的生物燃料.合成气发酵技术最大瓶颈是质量传递限制,其中主要的限制步骤是气液传质.本文对合成气发酵的质量传递限制研究进行综述,重点阐述合成气发酵生物反应器以及添加剂对质量传递的影响.     

Application and Development of Biomass Fuels for Transportation in China

Biomass fuels have become a big concern due to the large increase in green house gases and the rapid rise of petroleum prices around the world. This paper reviews recent developments in biomass fuels, such as ethanol and biodiesel, in China. Ethanol-gasoline mixture (E10) for vehicles is currently distributed in nine provinces while biodiesel is under development. One way to extend the application of ethanol is to burn it in diesel engines to lower soot emissions. The effects of the different methods blending ethanol with fossil diesel, and blending biodiesel with fossil diesel and ethanol-diesel on the combustion and emissions are investigated. The test results show that ethanol and biodiesel can be mixed with fossil diesel to greatly reduce particulate matter and soot emissions from diesel engines. But the application of ethanol blending with fossil diesel is more difficult than that of ethanol blending with gasoline, and biodiesel blending with fossil diesel. The dual-fuel injection of ethanol and diesel systems has the highest smoke reduction effect for a high ethanol fraction.     

Algal biomass as a global source of transport fuels: Overview and development perspectives

As a result of the global fuel crisis of the early 1970 s,coupled with concerns for the environment,the use of biofuel has been on the increase in many regions throughout the world.At present,a total of approximately 30 billion(30×109) liters of biofuel are utilized worldwide annually,although most countries rely hugely on the first generation biofuel.The limitations of the first and second generation biofuel gave rise to current interest in algae as a promising alternative to these conventional biofuel sources.Algal biomass could provide a lion’s share of the global transport fuel requirements in future.The present review highlights some important developments in,and potentials of algaculture as a major biomass resource of the future.However,the major constraint to commercial-scale algae farming for energy production is the cost factor,which must be addressed adequately before its potentials can be harnessed.     

Genomics of cellulosic biofuels

The development of alternatives to fossil fuels as an energy source is an urgent global priority. Cellulosic biomass has the potential to contribute to meeting the demand for liquid fuel, but land-use requirements and process inefficiencies represent hurdles for large-scale deployment of biomass-to-biofuel technologies. Genomic information gathered from across the biosphere, including potential energy crops and microorganisms able to break down biomass, will be vital for improving the prospects of significant cellulosic biofuel production.     

Insights on cellulose hydrolysis in the porous structure of biomass particles using the lattice Boltzmann method

Lignocellulose biomass has been recognized as one of the most promising sources of low-cost and renewable biofuels, and its conversion into alternative fuels and valuable platform molecules has attracted widespread attention. The porous solid residue from lignocellulose biomass, which was pretreated by steam-stripping, is catalyzed by dilute sulfuric acid to form levulinic acid (LA). The process includes porous media diffusion, multicomponent reactive transport, liquid-solid interface reaction, and cellulose dissolution. Understanding the interactions between these complex physicochemical processes is the basis for optimizing the performance of the hydrolysis reaction. In this study, a porous reaction transport model based on the lattice Boltzmann method (LBM) was established to simulate the conversion of cellulose to LA which was catalyzed by dilute acid. The simulation results were compared with the existing experimental results to verify the accuracy of the model. The simulation results showed that temperature has a significant effect on hydrolysis and the highest carbon yield was obtained at 180 °C. Without considering the lignin reaction, the higher the sulfuric acid concentration, the better is the hydrolysis efficiency in the range of 4% – 8%. The influence of cellulose content and steam-stripping the residue porosity on the dissolution rate of cellulose was also evaluated. The average dissolution rate of cellulose is the highest within 75 min, when the porosity is 0.7 and the cellulose content is 50%.     

生物质平模成型燃料设备及规模化运行系统研究

研究设计了一种具有适应物料范围广、成型燃料直径易变化、生产效率高、能耗低等特点的生物质燃料平模成型设备.为了实现生物质成型系统规模化运行,降低能耗,提高产率,对生物质成型设备进行了合理配置和整合,实现了一体化运行.根据进料量、粉碎量、供热量、出料量、物料含水率等条件变化,对生物质成型设备进行自动化设计,实现了生物质成型燃料系统自动连续稳定生产,提高了设备的集成化水平,减少了人工操作.另外,生物质原料干燥过程采用生物质热风炉提供热源,不消耗传统能源.生物质平模成型燃料设备及其规模化运行研究为生物质资源的能源化利用提供较为合理的途径.     

The impact of biofuel plantation on biodiversity: a review

Because plants convert solar energy into chemical energy stored in organisms, biomass production as an energy source can help to reduce the world＇s reliance on fossil energy and mitigate global warming. Biofuel production is a fast-growing industry that represents a new type of large-scale human disturbance on ecosystems. Thus, the benefits of biofuel production bring environmental risks that include its potential impact on biodiversity, which is still an open question. In this review, we start first with a brief overview of the evolution of biofuel concept; second, we review the state of biofuel production across the continents, with a major emphasis on the main species used and their major feedstock. For which, we found significant differences for land use and environmental cultural management of biofuel plantation between tropical and temperate regions. Third, we summarize the impacts of biofuel plantation on biodiversity at multiple scales, based on the case studied with respect to the corresponding issues. At the genetic level, introgression and contamination by aggressive genotypes are a primary risk. At the species level, habitat pollution, degradation, and disturbance caused by intensive management of biofuel plantation significantly raise the risk of habitat fragmentation, native extinction, and bio-invasion. At the ecosystem level, the large-scale homogeneous landscape of biofuel plantation results in simplified community and food web that severely damage ecosystem services, including ecosystem diversity. Finally, we compare the current and potential benefits and risks of biofuel plantations for the practical application of a biofuel industry of China. We emphasize the land use constraint from food security and biodiversity conservation, and the need for scientific research and systematic monitoring as a critical support for the sustainable development of biofuel production in China.     

生物柴油绿色生产工艺研究进展

重点介绍了生物柴油的绿色生产工艺，包括非均相催化、超临界和加氢脱氧等工艺，以及针对生物柴油精制过程开发的真空蒸馏、分子蒸馏、超临界萃取精馏、微滤膜分离和吸附精炼工艺，最后对生物柴油未来的发展趋势进行了展望。     

中国生物柴油原料供应前景研究

从全球能源形势与发展趋势来看,生物柴油是大力开发的一种重要绿色能源.阐述了生物柴油的本质及其较石化柴油在使用上的优良特性,综述了生物柴油主要在欧美国家中的发展现状及原料供应情况,特别是以大豆和油菜等油料作物为主的生物柴油原料生产状况.在分析了我国油料生产与食用消费现状、油料作物与粮食生产对耕地资源的激烈竞争矛盾的基础上,介绍了极具潜力的2种能源作物麻疯树(Jatropha curcas)、黄连木(Pistacia chinensisBge,)可以利用能源作物边际土地,即可用于种植能源作物的冬闲田和宜能荒地等,来开垦种植能源作物.在阐述了我国生物柴油原料供应情况后,粗略地匡算了生物柴油原料的供应量,分析了各种生物柴油原料供应的利弊,提出中国大规模发展生物柴油任重而道远.     

Non-fermentative pathways for synthesis of branched-chain higher alcohols as biofuels

Global energy and environmental problems have stimulated increased efforts towards synthesizing biofuels from renewable resources. Compared to the traditional biofuel, ethanol, higher alcohols offer advantages as gasoline substitutes because of their higher energy density and lower hygroscopicity. In addition, branched-chain alcohols have higher octane numbers compared with their straight-chain counterparts. However, these alcohols cannot be synthesized economically using native organisms. Here we present a metabolic engineering approach using Escherichia coli to produce higher alcohols including isobutanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-phenylethanol from glucose, a renewable carbon source. This strategy uses the host's highly active amino acid biosynthetic pathway and diverts its 2-keto acid intermediates for alcohol synthesis. In particular, we have achieved high-yield, high-specificity production of isobutanol from glucose. The strategy enables the exploration of biofuels beyond those naturally accumulated to high quantities in microbial fermentation.     

Microbial engineering for the production of advanced biofuels

Advanced biofuels produced by microorganisms have similar properties to petroleum-based fuels, and can 'drop in' to the existing transportation infrastructure. However, producing these biofuels in yields high enough to be useful requires the engineering of the microorganism's metabolism. Such engineering is not based on just one specific feedstock or host organism. Data-driven and synthetic-biology approaches can be used to optimize both the host and pathways to maximize fuel production. Despite some success, challenges still need to be met to move advanced biofuels towards commercialization, and to compete with more conventional fuels.     

Adelfa： a futuristic biodiesel fuel for DI diesel engines： a comparative experimental investigation

Biodiesel fuel is found to be a promising alter- native for the petroleum diesel based on the results published by the researchers for a decade. Biodiesel fuel is renewable and non degradable fuel. Many countries use biodiesel fuel for automotives to meet the crisis due to the depletion of the petroleum fuel and to meet the stringent emission norms. Various researches have been carried out with different bio- diesel fuels with vegetable oil as the source and appreciable results were reported. Few biodiesel fuels which have been already tested are Jatropha, Pongamia, Mahua, neem, cotton seed, etc. In this experimental work, Adelfa biodiesel blend is used as the test fuel. The emission and performance charac- teristics were compared with three other different biodiesel fuel blends. Appreciable results imply that Adelfa biodiesel （Nerium oil methyl ester） can be a futuristic biodiesel fuel, which has a good compatibility with the direct injection （DI） diesel engine without any major modification. Moreover, Adelfa can be cultivated in a non agricultural land with fewer sources of water. It is widely spread over all major countries of Asia. Experimental investigations have been carried out on a single cylinder DI diesel engine with standard engine speci- fications. In this experimental work, various Adelfa biodiesel blends is compared with reference fuel （diesel） to choose the best blend which gives a closer performance to diesel. The comparative analysis with other biodiesel fuels has also been done and results have been discussed.     

微藻生物柴油在国内外的研究

藻类生物柴油作为一种可再生能源具有不占地、用水少、油脂含量高等特点,与农作物相比,单位面积的产率可高出数十倍;介绍了国内外微藻生物柴油的研发概况,分析了目前微藻生物柴油研究及工业化应用中存在的主要困难和问题,指出了降低生产成本是当前微藻生物柴油研究中面临的主要挑战。     

生物质液体燃料生产系统技术经济建模及分析

利用生物质生产液体燃料是世界可再生能源发展的趋势之一。由于生物质液体燃料的原料来源及收集方式和生产工艺具有特殊性,其生产系统与现有化石液体燃料有较大区别。该文建立了包括多个通用模块的技术经济分析模型,以解决不同原料和工艺路线的生物质液体燃料生产系统的投资及成本分析和生产组织优化等问题。利用该模型对以玉米秸秆为原料的乙醇生产系统进行了案例分析。分析结果表明:目前1万t/a规模的玉米秸秆乙醇单位成本以加工费用为主,乙醇产出系数和生产操作费用系数变化对于成本影响最大。     

叔丁醇介质体系中R.oryzae细胞催化大豆油制备生物柴油的研究

利用产胞内脂肪酶的微生物全细胞代替脂肪酶用于生物柴油的制备是降低酶法制备生物柴油成本的一条可行途径,近年来成为酶法制备生物柴油领域的研究热点。本论文探讨在叔丁醇介质体系下,以固定化R.oryzae全细胞作为催化剂催化大豆油制备生物柴油的可行性;考察叔丁醇用量、甲醇用量、缓冲液pH、初始含水量、菌体干重以及反应温度等因素对生物柴油得率的影响。在优化反应条件下,以大豆油为原料,反应24h生物柴油得率可达70%左右。比较了固定化R.oryzae全细胞在叔丁醇介质体系与无溶剂体系两种体系下的稳定性。结果表明,叔丁醇介质体系下R.oryzae全细胞回用稳定性显著提高。     

广西木薯茎秆资源的能源利用

文章分析了广西木薯茎秆资源可获得性及燃料性状,进而讨论了开发木薯茎秆资源的可行性及商业价值,证明木薯茎秆是优秀的生物质原材料,具有开发固体成型燃料及热电联产的价值。     

脉冲激光沉积(PLD)机理分析及其应用

脉冲激光沉积薄膜是近年来发展起来的使用范围最广,最有希望的制膜技术．该文阐述了脉冲激光沉积技术的机理、特点,薄膜生长主要包括三个过程：1)激光与物质相互作用产生等离子体;2)等离子体向基片扩散;3)等离子体中粒子在基片上生长薄膜．文章还分析了脉冲沉积过程中各主要沉积参数,如激光能量密度、沉积气压和衬底情况等对薄膜质量的影响,并介绍了其在制备半导体、高温超导、类金刚石、生物陶瓷薄膜等方面的应用。     

喷动流化床在生物质快速热解技术中的应用

生物质快速热解技术是国内外生物质资源高效利用的重点研究课题.介绍了目前快速热解反应器的主要类型,并对生物质快速热解技术进行了归纳,重点总结了喷动流化床快速热解反应器的特点和在生物质快速热解方面的应用状况,指出喷动流化床快速热解反应器具有操作灵活、工作稳定、环隙区无死区、介质间传热效果好、易于工业放大等优点,在快速热解领域具有广阔的发展前景.     

汽化潜热和黏度对含氧燃料喷雾特性影响研究

通过配比柴油/生物柴油/正丁醇混合燃料、柴油/汽油/正庚烷混合燃料,分别和柴油/2,5-二甲基呋喃混合燃料的汽化潜热和黏度一致。基于高压定容装置,利用高速摄影技术对不同含氧燃料的宏观喷雾特性进行研究,分析汽化潜热和黏度的改变对燃料喷雾锥角和贯穿距离的影响。结果表明:含氧燃料的黏度增大,喷雾锥角和贯穿距离均变小;且对喷雾锥角影响显著。汽化潜热增大,会引起喷雾锥角的降低和喷雾贯穿距的增大。相比于其他两种含氧燃料,柴油/2,5-二甲基呋喃混合燃料在相同试验工况下的喷雾特性更好,有利于增强燃料雾化混合质量。