Effect of corn stover concentration on rheological characteristics

Corn stover, a well-known example of lignocellulosic biomass, is a potential renewable feed for bioethanol production. Dilute sulfuric acid pretreatment removes hemicellulose and makes the cellulose more susceptible to bacterial digestion. The rheologic properties of corn stover pretreated in such a manner were studied. The Power Law parameters were sensitive to corn stover suspension concentration becoming more non-Newtonian with slope n, ranging from 0.92 to 0.05 between 5 and 30% solids. The Casson and the Power Law models described the experimental data with correlation coefficients ranging from 0.90 to 0.99 and 0.85 to 0.99, respectively. The yield stress predicted by direct data extrapolation and by the Herschel-Bulkley model was similar for each concentration of corn stover tested.     

Effect of coal on the rheological and mechanical properties of epoxy matrix

An experimental study was conducted to investigate the effect of coal used as a new type of filler in epoxy networks. For this purpose two series of epoxy composites with different coal weight fraction were studied and their thermo-mechanical properties were characterized. The work demonstrated that coal-filled epoxy networks show a typical behavior of a particulate filled material and follows the theoretical models already used.     

Effect of pretreatment temperature of pine on bio-oil characteristics

通过螺旋反应器低温预处理除去松木中的半纤维素和水分,然后用预处理得到的固体残渣来快速热解制生物油.固体残渣的化学组成分析和红外光谱分析表明,由于木质素含量的增加和炭化反应的发生,生物油的产率降低、焦和不可冷凝气的产率增加.随着预处理温度的升高,生物油水分含量减少,高位热值增加,运动黏度增加,密度增加,pH值先升高后降低,固体颗粒物含量增加.核磁共振碳谱分析表明,生物油的脂肪碳含量减少,芳香碳含量增加,芳香度增加.     

松木预处理温度对生物油特性的影响

通过螺旋反应器低温预处理除去松木中的半纤维素和水分,然后用预处理得到的固体残渣来快速热解制生物油。固体残渣的化学组成分析和红外光谱分析表明,由于木质素含量的增加和炭化反应的发生,生物油的产率降低、焦和不可冷凝气的产率增加。随着预处理温度的升高,生物油水分含量减少,高位热值增加,运动黏度增加,密度增加,pH值先升高后降低,固体颗粒物含量增加。核磁共振碳谱分析表明,生物油的脂肪碳含量减少,芳香碳含量增加,芳香度增加。     

Effect of mixture components on the rheological characteristics of the composite

Rheological characteristics and properties of composites prepared from tanning industry wastes were studied in relation to the ratio and composition of components in the mixture.     

Fe~(3+)辅助煤浆氧化制氢研究

利用Fe~(3+)/Fe~(2+)电对的相互转化原理,在水热反应釜中用Fe~(3+)氧化煤浆得到Fe~(2+),将Fe~(2+)在电解槽中电解氧化,在阴极产生氢气,从而通过两步反应形成一个新的煤浆电氧化制氢工艺。进行了九次水热-电解循环实验,在恒电压(1V)条件下,测试了电解反应的电流密度和累积电量的数据,并对循环实验前期、中期、后期的三个阶段煤样品进行了扫描电镜(SEM)、比表面积(BET)、热重(TG)、红外光谱(FT-IR)等表征分析。研究表明,相对于通常煤浆电氧化制氢工艺,这种"两步法"煤浆制氢新工艺具有更高的反应速率,初始电流密度约为60 m A/cm2,而传统的"一步法"煤浆制氢工艺初始电流密度均不超过10 m A/cm~2。表征分析结果很好地反映了煤颗粒在这种制氢工艺过程中的形态、结构、成分的变化,从而解释了在新的煤浆氧化制氢工艺中的Fe~(3+)/Fe~(2+)转化的反应机理。     

The effect of particle size on hydrolysis reaction rates and rheological properties in cellulosic slurries

The effect of varying initial particle sizes on enzymatic hydrolysis rates and rheological properties of sawdust slurries is investigated. Slurries with four particle size ranges (33 microm < x < or = 75 microm, 150 microm < x < or = 180 microm, 295 microm < x < or = 425 microm, and 590 microm < x < or = 850 microm) were subjected to enzymatic hydrolysis using an enzyme dosage of 15 filter paper units per gram of cellulose at 50 degrees C and 250 rpm in shaker flasks. At lower initial particle sizes, higher enzymatic reaction rates and conversions of cellulose to glucose were observed. After 72 h 50 and 55% more glucose was produced from the smallest size particles than the largest size ones, for initial solids concentration of 10 and 13% (w/w), respectively. The effect of initial particle size on viscosity over a range of shear was also investigated. For equivalent initial solids concentration, smaller particle sizes result in lower viscosities such that at a concentration of 10% (w/w), the viscosity decreased from 3000 cP for 150 microm < x < or = 180 microm particle size slurries to 61.4 cP for 33 microm < x < or = 75 microm particle size slurries. Results indicate particle size reduction may provide a means for reducing the long residence time required for the enzymatic hydrolysis step in the conversion of biomass to ethanol. Furthermore, the corresponding reduction in viscosity may allow for higher solids loading and reduced reactor sizes during large-scale processing.     

Molecular origin for rheological characteristics of native gellan gum

The ¹H-nuclear magnetic resonance spectrum showed that the l-rhamnosyl residues of native gellan gum were coinvolved in both a small number of ⁴C₁-pyranose conformations and a large number of ¹C₄-pyranose conformations, whereas for deacylated polymer, almost of the residues were involved in ⁴C₁-pyranose conformation. The flow curves of native gellan gum showed plastic behavior above 0.2%. The elastic modulus stayed at a constant value with increase in temperature up to 40 °C, then decreased rapidly. The elastic modulus increased with addition of CaCl₂ (6.8 mM) and stayed constant value with increase in temperature up to 65 °C, then decreased rapidly. The stronger elastic modulus was observed in deacylated gellan gum with addition of CaCl₂. The elastic modulus of native gellan gum showed larger value than that in aqueous solution in the presence of urea (4.0 M). Intra- and intermolecular associations of native gellan gum molecules in the presence of Ca⁺² were proposed.     

煤中矿物质对灰熔融和燃烧特性的影响

采用化学分步萃取、XRD和SEM-EDS、煤灰灰成分分析等测试方法对五彩湾煤中矿物质的赋存形态进行了研究,并对逐级萃取前后煤样的燃烧特性和灰熔融特性进行了分析和比较.结果表明,五彩湾煤中原始矿物质主要有方解石、硫酸钙、高岭石、石英、黄铁矿等;煤中钠含量很高,主要以水合离子的形态溶于煤的内水中;有机形态的钠、镁和钙提高了煤的燃烧特性;五彩湾煤的煤灰熔融性主要受铁钙物质的量比(F₂O₃/CaO)影响,灰熔融特性温度随铁钙物质的量比(F₂O₃/CaO)的增大而降低.     

灰中焦对煤灰熔融特性的影响

采用连有电脑－摄像头的煤灰熔融特性测定装置，在Ar气氛下研究了灰中焦对煤灰熔融特性的影响。结果表明，灰中焦对灰熔融特征温度和灰熔融动态特征具有显著影响，影响程度与煤种以及煤焦的质量分数有关。掺焦的灰熔融温度高于不掺焦的熔融温度；掺焦量增加，其灰熔融温度升高。当掺焦量提高至20%时，在接近或高于煤灰熔融温度时由于焦与焦之间通过熔融煤灰的黏结作用形成了不熔骨架，使灰锥高度不再随温度的提高而发生变化，这也是灰锥很难出现或者根本不出现软化温度和流动温度的原因。     

Effect of organosolv ethanol pretreatment variables on physical characteristics of hybrid poplar substrates

Hybrid poplar (Populus nigra x P. maximowiczii) chips were pretreated using an organosolv ethanol process. The effect of pretreatment conditions (temperature, time, catalyst, and ethanol concentration) on the substrate characteristics, including fiber size, crystallinity, and degree of polymerization of cellulose, was investigated using an experimental matrix designed with response surface methodology. The conditions ranged 155-205 degrees C, 26-94 min, 0.83-1.67% catalyst (H(2)SO(4)) on oven-dry wood chip (w/w), and 25-75% ethanol concentration (v/v). The results indicated that the substrate characteristics are controllable and predictable. Desirable substrates can be prepared by fine-tuning the processing parameters. The regression models developed, allowed the quantitative prediction of the substrate characteristics from the pretreatment conditions used.     

不同的灰熔点调控方式对煤灰熔融特性的影响

对两种原始煤灰进行混合,并分别搭配不同的添加剂,得到3种元素组成相同的煤灰,灰熔点测试结果显示,三者的灰熔点存在较大差异。结合X射线衍射技术和SEM-EDX(扫描电子显微镜与能谱联用)分析了3种煤灰(>800 ℃)在高温时的矿物质转化过程。结果表明,不同的灰熔点调控手段对不同煤的影响是不同的。原因是高温时矿物质组成不仅与煤灰化学元素组成相关,更与元素在矿物质中的赋存状态有关。两者共同决定了煤灰的熔融特性。     

Effect of yeast pretreatment on the characteristics of yeast-modified electrodes as mediated amperometric biosensors for lactic acid

Carbon paste electrode modified with baker' and wine yeast Saccharomyces cerevisiae (a source of flavocytochrome b(2)) were investigated as amperometric biosensors for L-lactic acid. Before immobilization on the electrode surface, yeast cells were pretreated with various electrolytes, alcohols and weak organic acids. Electrode responses to L-lactic acid were tested in the presence of various mediators (potassium ferricyanide, phenazine methosulfate, 2,6-dichlorophenolindophenol sodium salt hydrate, 1,2-naphthoquinone-4-sulfonic acid sodium salt). The highest (144+/-7 nA per 0.2 mM L-lactic acid) and the most stable responses were obtained after yeast pretreatment with 30% ethanol using potassium ferricyanide as a mediator. Different electrode sensitivities with mediator phenazine methosulphate probably reflected diverse changes in yeast membrane (and/or cell wall).     

Effect of long-term heat exposure on rheological and intrinsic water characteristics of bone-derived beef stocks

Bone-derived protein stocks are used in food industry to enhance taste of soups, sauces, and a range of other products. Both during commercial manufacturing and when used for culinary purposes, the stocks may be exposed to high temperatures for an extended time period. The present study investigated the effect of retention at 90°C for 0, 3, 6, 9, 24, 48, 72, and 168 hr on the functional attributes of concentrated bone-derived beef stocks (57% Dry matter (DM)). Visual inspection and rheological analyses showed that during increasing heat exposure, the gel strength as well as viscosity of the concentrated stocks decreased incrementally and significantly (P > 0.001). Nuclear magnetic resonance (NMR) relaxation measurements conducted on the beef stocks also revealed strong effects of heat exposure on the transverse (T₂) relaxation time, which increased incrementally and significantly (P > 0.001) with longer heat exposure. Thus, the present study demonstrated that heat-induced changes in rheological properties of bone-derived beef stocks can be ascribed to changes in intrinsic water–protein interactions and water attributes as a result of heat-induced protein modifications. In conclusion, the study proves that NMR relaxometry is a valuable tool for monitoring changes in intrinsic water mobility that are manifested in modified functional attributes of concentrated beef stocks.     

不同预处理方法对准东高碱煤中碱金属含量测定的影响

以四种不同的准东高碱煤及气化飞灰为研究对象,对高碱煤及气化飞灰中碱金属(Na、K)的赋存形态,以及不同预处理方法(低温灰化法、直接消解法、中国国标法、萃取法及氧弹燃烧法)对准东高碱煤及气化飞灰中碱金属(Na、K)含量测定的影响进行了测试分析。结果表明,准东高碱煤中碱金属Na主要以水溶态形式存在,碱金属K主要以水不溶态形式存在;不同的预处理方法对准东高碱煤中碱金属(Na、K)含量的测定结果影响显著,对于准东高碱煤及气化飞灰中碱金属(Na、K)含量测定,建议采用氧弹燃烧法,萃取法也可以相对准确地反映煤中碱金属Na的含量。     

煤质特性对CeO_2催化煤粉燃烧的影响

利用酸洗法和燃烧法分别得到煤中的有机物(脱灰煤粉)和煤灰,研究了煤变质程度、显微组分、煤灰含量等煤质特性对CeO2催化煤粉燃烧的影响。研究发现,变质程度对CeO2催化煤粉燃烧具有明显的影响,变质程度越高的脱灰煤粉燃点降低越多,燃速提高越快。其催化燃烧顺序为褐煤烟煤无烟煤。同时研究发现,CeO2对神华烟煤两种主要显微组分的燃烧没有明显的催化作用。煤灰对脱灰煤粉燃烧也有催化作用,对人工煤而言,当煤灰含量低于18%时,煤灰与CeO2具有协同作用。煤灰的质量分数为6%时,煤灰与CeO2的协同作用最强,之后随着煤灰增加协同作用逐渐变弱;当煤灰的质量分数超过18%时,协同作用消失,CeO2的催化作用消失。说明煤灰含量超过18%时,CeO2的催化作用被抑制。     

煤及其拔头半焦的燃烧反应特性研究

采用热天平研究了贵州褐煤、三江原煤及其拔头半焦的燃烧行为,考察了粒径和升温速率对样品着火点和燃烧稳定性的影响。减小样品的粒径可显著降低样品的着火点,改善样品的燃烧性能,在粒径100～120目和升温速率25℃/min下,样品的燃烧稳定性最好。根据Coats-Redfern方法求解燃烧反应动力学参数。燃烧反应动力学分析表明,三种样品的热天平燃烧反应均为一级反应,并得到了实验样品的燃烧反应动力学参数,表观活化能E和指前因子A。贵州褐煤的活化能为100.0～163.6 kJ/mol,三江原煤的活化能为73.4～161.2 kJ/mol,三江煤焦的活化能为68.3～178.1 kJ/mol。     

Effect of thermo-lime and hot-water pretreatment on the thermal-decomposition characteristics and structure of Spartina alterniflora

The thermal-decomposition characteristics and kinetics of Spartina alterniflora (smooth cordgrass; SC) pretreated with thermo-lime and hot water were investigated by thermogravimetric analysis. Results showed that pretreatment changed the thermal-decomposition behavior of pretreated biomass, as shown in the change of the volatile-matter yield, the thermal-decomposition temperature for a given conversion and the mass-loss rate, because of the breakage of lignocellulosic structure. The activation energy of SC ranged from 40.8 to 55.8 kJ mol^?1 for conversion ratios between 0.15 and 0.8. Pretreatment increased the activation energy of thermal-decomposition reaction, indicating the increment of the thermal stability of biomass. Compared with thermo-lime pretreatment, hot-water pretreatment increased the volatile-matter yield, activation energy, and mass-loss rate of the sample. Structure changes were further investigated by X-ray and Fourier-transform infrared (FTIR) spectroscopy analysis to determine the effect of pretreatment on thermal decomposition. FTIR analyses revealed the depolymerization of lignocellulosic structure and the disruption of carboxyl carbons attached to the lignin side chain. X-ray and FTIR results also showed that thermo-lime and hot-water pretreatment broke the crystalline structure of cellulose by disrupting hydrogen bonding and removing amorphous matter. Compared with hot water, thermo-lime pretreatment resulted in many modifications of lignocellulosic structure and composition. Furthermore, structure breakage and composition removal changed thermal-decomposition characteristics of pretreated samples.