生物质洁净能源研究中的流化床动力学模型

分别对最小流化床、鼓泡流化床和腾涌流化床及相应的全混模型、鼓泡模型、气泡汇集模型等加以综述 ,分析其优缺点 ,并在此基础上提出动力学模拟研究的新思路 .根据流化床内在的本质———流化态的不同 ,将流化床分为最小流化床、鼓泡流化床和腾涌流化床三种 .总结了前人针对各种流化床提出的全混模型、鼓泡模型、气泡汇集模型等思想 ,建议今后可以在以下几个方面进行深入研究 :⑴使得模型更有普适性 .⑵由于气泡有效直径尚不能在理论上求得 ,可以在理想气泡直径变化公式的基础上 ,加入非线性化学的计算 .⑶确定不同情况下的参数 ,使得工作更有延续性 ,也使得模型更加具有生命力 .⑷从高压的角度去进行模型的计算 ,并得到相应的试验数据支持 .     

Rail vs truck transport of biomass

This study analyzes the economics of transshipping biomass from truck to train in a North American setting. Transshipment will only be economic when the cost per unit distance of a second transportation mode is less than the original mode. There is an optimum number of transshipment terminals which is related to biomass yield. Transshipment incurs incremental fixed costs, and hence there is a minimum shipping distance for rail transport above which lower costs/km offset the incremental fixed costs. For transport by dedicated unit train with an optimum number of terminals, the minimum economic rail shipping distance for straw is 170 km, and for boreal forest harvest residue wood chips is 145 km. The minimum economic shipping distance for straw exceeds the biomass draw distance for economically sized centrally located power plants, and hence the prospects for rail transport are limited to cases in which traffic congestion from truck transport would otherwise preclude project development. Ideally, wood chip transport costs would be lowered by rail transshipment for an economically sized centrally located power plant, but in a specific case in Alberta, Canada, the layout of existing rail lines precludes a centrally located plant supplied by rail, whereas a more versatile road system enables it by truck. Hence for wood chips as well as straw the economic incentive for rail transport to centrally located processing plants is limited. Rail transshipment may still be preferred in cases in which road congestion precludes truck delivery, for example as result of community objections.     

Comparison of yellow poplar pretreatment between NREL digester and sunds hydrolyzer

Single-stage cocurrent dilute acid pretreatments were carried out on yellow poplar (Liriodendron tulipifera) sawdust using an as-installed and short residence time modified pilot-scale Sunds hydrolyzer and a 4-L bench-scale NREL digester (steam explosion reactor). Pretreatment conditions for the Sunds hydrolyzer, installed in the NREL process development unit (PDU), which operates at 1 t/d (bone-dry t) feed rate, spanned the temperature range of 160 – 210°C, 0.1 – 1.0% (w/w) sulfuric acid, and 4-10-min residence times. The batch pretreatments of yellow poplar sawdust in the bench-scale digester were carried out at 210 and 230°C, 0.26% (w/w) sulfuric acid, and 1-, 3-, and 4-min residence times. The dilute acid prehydrolysis solubilized more than 90% of the hemicellulose, and increased the enzymatic digestibility of the cellulose that remained in the solids. Compositional analysis of the pretreated solids and liquors and mass balance data show that the two pretreatment devices had similar pretreatment performance.     

Coordinating California’s efforts to promote waste to alcohol production

Alcohol fuels produced from biomass can improve air quality, enhance energy security, create employment opportunities, and reduce waste disposal problems. Opportunities in California exist to produce alcohols from waste streams from various sectors of the economy. Government agencies have promoted waste-to-alcohol activities, but efforts have been inconsistent and intermittent. Often these efforts have been hindered by contradictory but mandate-driven policies. A prudent approach to coordinate statewide efforts includes the development of an integrated statewide policy to examine barriers that impede private sector business efforts to produce alcohols from biomass. A multi-agency task force to promote research, development, commercialization, and marketing efforts for biomass-produced alcohols is desirable. The views and opinions contained in this document do not necessarily reflect those of the California Energy Commission, its staff, management, or the State of California.     

Overwhelming electrochemical oxygen reduction reaction of zinc-nitrogen-carbon from biomass resource chitosan via a facile carbon bath method

Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction (ORR), which is the fundamental for the development and commercialization of renewable energy conversion technology. Herein, zinc-nitrogen-carbon (Zn-N-C) was prepared by using biomass resource chitosan via a facile carbon bath method. The obtained Zn-N-C delivered a high specific surface area (794.7 cm²/g) together with pore volume (0.49 cm³/g). During the electrochemical evaluation of oxygen reduction reaction (ORR), Zn-N-C displayed high activity for ORR with an onset potential E₀ = 0.96 V_RHE and a half wave potential E_1/2 = 0.86 V_RHE, which were more positive than those of the commercial 20 wt% Pt/C benchmark catalyst (E₀ = 0.96 V_RHE and E_1/2 = 0.81 V_RHE). In addition, the Zn-N-C catalyst also had a better stability and methanol tolerance than those of the Pt/C catalyst.     

生物质裂解产物的制备及HPLC检测其成分的虚拟仿真实验开发

In order to improve university laboratory teaching and practical education under the background of information technology, as well as overcome the difficulty for practical training, develop a virtual simulation experiment platform for rapid pyrolysis of natal materials and high-performance liquid chromatographic (HPLC) detection of its components. The experiment integrates the actual operation process of the plant to produce cleaved products by rapid pyrolysis of biomass with HPLC detection. The virtual experiment is divided into biomass sample pretreatment, rapid biomass pyrolysis, bio-oil extraction, and HPLC determination of complex components, making the biomass cleavage workshop "real" through simulation. This virtual simulation experiment fully integrates the utilization of biomass resources and basic chemistry courses (such as organic chemistry, instrumental analysis, chemical engineering principles, etc.), which are widely involved in agricultural and forestry majors with advantageous characteristics value.     

基于差示扫描量热技术的生物质热解两步连续反应模型研究

采用差示扫描量热分析仪对我国的一种生物质试样在空气气氛中进行了实验, 发现试样从常温到923 K高温的低速升温过程中, 经历了两步明显的放热过程. 对放热机理的分析表明, 第一步主要是由半纤维素和纤维素的有氧热解过程控制, 第二步放热过程则受木质素热解和炭的氧化反应的共同作用. 采用等转化率方法和优化计算方法, 对热解过程的动力学模型进行了研究, 结果表明, 两步连续反应机理可用于描述生物质在空气气氛中热解的放热动力学.     

Thermogravimetric study of the pyrolysis of waste wood

A thermogravimetric study of the pyrolysis of three different types of waste wood (forest wood, old furniture and used pallets) is carried out in a TGA equipment using dynamic and isothermal techniques. Isothermal runs were carried out at two temperature levels, one between 225° and 325°C (low range) and the other, between 700° and 900°C (high range). Results show a good agreement between the kinetic parameters obtained from either dynamic or isothermal techniques. It must be remarked that the own chemical composition of each type of wood together with the compounds added to the wood for each application, play a fundamental role in the kinetic behavior of their thermal decomposition.     

Assessment of various carbon sources and nutrient feeding strategies for Panax ginseng cell culture

Ginseng (root of Panax ginseng C. A. Meyer) cells were cultivated on medium supplemented with various carbohydrates including sucrose, glucose, and fructose, at initial concentrations ranging from 10 to 110 g/L. Sucrose was shown to be the superior carbon source to the monosaccharides for ginseng cell growth and the optimal concentration was between 30 and 50 g/L. An increase in the initial concentration within this range increased the maximum cell density and growth index significantly, whereas much higher concentrations inhibited cell growth. Feeding of sucrose and some other medium components during the growth (fed-batch mode) was more effective in enhancing the cell growth and biomass productivity, increasing the growth index by more than 60–70% and biomass productivity by more than 50%.     

Application of flow-injection analysis in the on-line monitoring of sugars,lactic acid,protein and biomass during lactic acid fermentations

A laboratory system for the on-line monitoring of important lactic acid fermentation variables is described. The system contains flow-injection analysers for glucose, lactose, galactose, lactate and protein and a continuous-flow analyser for the biomass concentration. The sugar and lactate analysers are based on enzymatic reactions involving oxidases followed by chemiluminescence detection of the hydrogen peroxide formed. The protein analyser is based on the biuret reaction. The system has been used to monitor many fermentation experiments, and some results are presented as examples.