木质纤维素生产乙醇的大型试验

乙醇是以木质纤维素为原料,通过蒸气预处理、纤维素酶的牛产、酶水解、酒精发酵等工艺而制成的.该文主要阐述用木质纤维素生产乙醇的方法和工艺流程.     

饮酒后乙醇在人体内的动态

酒在口内,自然有一部分气化,即以乙醇蒸气的形式进入呼吸道。遂即直接入肺,随着大循环而进入心脏,又进入大脑。其数量极微,但对乙醇过敏的人来说,闻酒也闻     

乳糖在乙醇-水混合溶液中介稳区的测定

测定了20～70℃温度区间内乳糖晶体在乙醇一水混合溶剂中的溶解度和过饱和度曲线,确定了晶体生长介稳区范围.拟合出了各乙醇浓度下溶解度随温度变化的经验方程式,同时获得了各乙醇浓度下介稳区宽度与温度的经验公式,并且初步考察了乙醇一水混合溶液中自发结晶生成微晶的可行性.研究结果表明,以混合溶剂代替纯水作溶剂,使溶液的介稳区变窄,过饱和度提高,有望通过改变溶剂体系组成结构一步法制备微晶乳糖.     

乳糖在乙醇-水混合溶液中介稳区的测定

测定了20～70℃温度区间内乳糖晶体在乙醇-水混合溶剂中的溶解度和过饱和度曲线,确定了晶体生长介稳区范围,拟合出了各乙醇浓度下溶解度随温度变化的经验方程式,同时获得了各乙醇浓度下介稳区宽度与温度的经验公式,并且初步考察了乙醇-水混合溶液中自发结晶生成微晶的可行性。研究结果表明,以混合溶剂代替纯水作溶剂,使溶液的介稳区变窄,过饱和度提高,有望通过改变溶剂体系组成结构一步法制备微晶乳糖。      

光电比色法测定啤酒中的酒精度

布·勃·卡弗格教授等研究了光电比色法测定糖果中的酒精含量,酒精含量不大时其结果很好。我们研究了用这个方法测定啤酒中酒精度的可能性。此方法的原理是从溶液馏出的乙醇被硝酸介质中的重铬酸钾氧化生成醋酸,其反应方程式如下:     

白酒大生产过程中乙醇稳定碳同位素变化特征研究

为了研究白酒大生产过程中乙醇稳定碳同位素的变化特征及其在掺假检测领域的应用可行性,该文利用稳定同位素比值质谱仪(isotope ratio mass spectrometry, IRMS)对蒸酒过程、酒醅与基础酒和发酵过程中的乙醇δ¹³C的变化规律进行了研究,并分析了基础酒和成品白酒的稳定性特征,结果表明,蒸酒过程中出现了反蒸气压分馏效应,会影响不同摘酒段的乙醇δ¹³C,而酒醅与基础酒之间不存在显著差异,基础酒和成品白酒存在一定波动范围,但无显著性差异。该研究对下一步应用碳同位素技术进行白酒真实性保障和掺假检测提供数据支持。     

基于CFD的蒸气箱分区结构流场数值模拟

针对蒸气箱在开发改进过程中,缺少对内部蒸气流动特性的理论分析和有效开发手段而过于依赖设计经验的问题,建立了基于计算流体动力学(CFD)的蒸气可压缩流动模型,采用了FLUENT的SSTκ-ω模型对蒸气箱内部分区结构进行蒸气流动数值模拟;改变不同的输入条件,探索了蒸气箱内部的缓冲区、阻流区、主流区和扩散板等结构对蒸气喷射稳定性、均匀性和热量损失的影响。研究表明:缓冲区与阻流区阶梯连接会产生较强的蒸气湍流,迅速降低喷射速度;阻流板在降低流速,分散蒸气流动的同时,加剧蒸气湍流,影响蒸气输出速度和流量分布;扩散孔的形状分布直接影响了蒸气喷射速度、流量和加热区域均匀蒸气层的形成。     

谷氨酸晶体在乙醇——水混合溶剂中介稳区的测定

本文研究探讨了谷氨酸晶体在乙醇-水混合溶剂中,温度区间为5～50℃的溶解度和过饱和度曲线,确定了其生长介稳区范围,拟合出了溶解度随温度、乙醇浓度变化的经验方程式为S=(0.844-0.306mm)×2.831×10-28T11.108-0.489m-9.73×10-2,并讨论了溶液的稳定性.研究结果表明以混合溶剂代替纯水作溶剂使溶液的介稳区变宽,因此有望改善晶体生长条件,缩短生长周期一     

过热蒸气在造纸过程中的合理应用

文章以过热蒸气为对象,通过比较减温减压点不同,分析管径、壁厚、法兰、流速的变化,过热蒸气和饱和蒸气在运输过程中的能耗及运输管道成本.结果表明在输送过程中输送过热蒸气是最合理的,也是经济的.分析过热蒸气对钢材的强度、热膨胀、过度热应力的影响,说明过热蒸气影响设备安全性和寿命.     

酿酒文摘

吊酒罐常压工艺和联锁方法王兰江劳动保护 1978年3期30页根据有些酒厂的吊酒罐因承受高压发生爆炸以及轻工业部和国家劳动总局的通知,本文介绍了两种吊酒罐常压工艺和单手柄联联方法。图4使用振荡式 U 形管密度计测定蒸馏酒的标准酒度 D.H.Strunk 等著科技译文1980年2期125页本文介绍了一种密度计测定乙醇溶液中的乙醇浓度,方法简单、快速而准确。本文提出了校正乙醇比重对校准酒度标绘的非线性的方程式,而所得结果即百分数乙醇而非比重。用此密度计就标准酒度1～90°的乙醇—水溶液、伏特加、威士忌、白兰地和利口     

Evaporation rates and vapor pressures of individual aerosol species formed in the atmospheric oxidation of alpha- and beta-pinene

The semivolatile oxidation products (trans-norpinic acid, pinic acid, cis-pinonic acid, etc.) of the biogenic monoterpenes (alpha-pinene, beta-pinene, etc.) contribute to the atmospheric burden of particulate matter. Using the tandem differential mobility analysis (TDMA) technique evaporation rates of glutaric acid, trans-norpinic acid, and pinic acid particles were measured in a laminar flow reactor. The vapor pressure of glutaric acid was found to be log(p0 glutaric/Pa) = - 3,510 K/T + 8.647 over the temperature range 290-300 K in good agreement with the values previously reported by Tao and McMurry (1989). The measured vapor pressure of trans-norpinic acid over the temperature range 290-312 K is log(p0 norpinic/Pa) = - 2,196.9 K/T + 3.522, and the vapor pressure of pinic acid is log(p0 pinic/ Pa) = - 5,691.7 K/T + 14.73 over the temperature range 290-323 K. The uncertainty on the reported vapor pressures is estimated to be approximately +/- 50%. The vapor pressure of cis-pinonic acid is estimated to be of the order of 7 x 10(-5) Pa at 296 K.     

Vapor Analysis of the Production by Banana Fruit of Certain Volatile Constituents

SUMMARY: Direct gas chromatographic vapor analyses were utilized to determine whether banana slices at different stages of ripeness in an in vitro system produced iso-amyl acetate and iso-amyl alcohol, known banana aroma constituents; and whether a precursor-product relationship could be observed between these compounds and L-leucine. Production of iso-amyl acetate by unripe slices was demonstrated based on experiments with metabolic inhibitors. The behavior of ripe and overripe slices was inconclusive since the vapor concentration of the acetate remained constant. The vapor concentration of iso-amyl alcohol was essentially unchanged at all ripeness stages. Investigations with L-leucine-U-¹⁴C showed conclusively that leucine was a precursor and that both compounds were continually produced at all ripeness stages. The interpretation of direct vapor analyses over respiring fruit is considered.     

Adsorption of trichloroethene at the vapor/water interface

Aqueous solution surface tension (pressure) as a function of vapor-phase trichloroethene (TCE) pressure isotherms were measured at atmospheric pressure at 287.2, 291.2, 297.2, 303.2, and 315.2 K using a flow-through vapor adsorption method. Solute (i.e., TCE)-induced surface tension variations were quantified using Axisymmetric Drop Shape Analysis-Profile (ADSA-P); vapor-phase TCE pressures were measured using automated gas chromatograph analysis. Surface tension reductions of 5-10% from neat water at saturated TCE vapor pressure were noted. Measured surface tension (pressure) isotherms were used to estimate vapor/water interface adsorption as a function of vapor-phase TCE pressure using the Gibbs relative interface excess (i.e., adsorption) equation and a nonideal two-dimensional equation of state. Complete isothermal adsorption profiles were nonlinear, with accelerated adsorption at increasing vapor-phase TCE pressures. Comparison to other studies of adsorption at infinite dilution (i.e., linear partitioning) and corresponding to thermodynamics (i.e., ideal equilibrium standard molar free energy, enthalpy, and entropy change) indicate good agreement. Estimates of TCE planar surface area were used to calculate the fraction of monolayer coverage at the vapor/water interface as a function of vapor-phase TCE pressure, which approached a maximum of 0.6-0.75 at saturated vapor pressure.     

低度酒蒸馏方程的推导

根据蒸馏酒理论采用微积分方法，以酒精质量分数与相对密度的对照表以及蒸馏时原酒液质量分数与蒸馏液质量分数对照表两组基础数据为依据，推导了原酒液酒度随蒸馏体积分数变化的关系方程式，进一步推导了以低度酒为原料进行蒸馏的蒸馏液酒度随蒸馏液体积变化的方程式，该方程可用于蒸馏过程酒度控制。     

MATHEMATICAL MODELING of TRANSIENT HEAT and MASS TRANSPORT IN A BAKING BISCUIT

Drying behavior of a single baking biscuit was modeled using unsteady state, anisotropic, two dimensional, simultaneous heat and mass balances. Solutions of these equations agreed well with the experimentally determined temperature and the moisture data. Modeling revealed that in the outer sections of the baking biscuit conduction and diffusion were the dominant heat and mass transfer mechanisms, respectively. In the central section of the biscuit the gas cells cracked with the increased vapor pressure and the upward volume expansion, then air/vapor enclaves were formed among the horizontal dough layers in the radial direction. the dominant heat and mass transfer mechanisms in the central section of the biscuit were convection. Presence of two different regime zones in a baking biscuit may have important consequences concerning the strength of the commercial products against crumbling during marketing and consumption.     

Beef Shank Fat Solubility in Supercritical Carbon Dioxide-Propane Mixtures and in Liquid Propane

For propane, conditions were 298K and 308K at the liquid vapor pressure. For supercritical mixtures, conditions were 308K at pressures from 8.9 to 15.7 MPa. The solubility of fat in CO₂-propane increased with increasing pressure, up to 0.66wt% at 15.7 MPa. The average solubility of the fat in propane at 298K was 16.7wt% and at 308K it was 21.4wt%. The extracted fat was solid with a melting range of 295–314K. There was no apparent degradation of collagen during extractions. Beef shank fat extraction with propane is feasible and advantageous over use of supercritical CO₂-propane.     

冷冻干燥和热风烘干对菠菜中农药残留的影响

食品安全的控制贯穿从农场到餐桌的全过程,涉及源头生产、流通、加工和销售等阶段。冷冻干燥和热风干燥是常用的干制菠菜方法,文中研究了真空冷冻干燥和热风干燥对菠菜中有机磷和拟除虫菊酯类农药的影响。实验结果表明:不同农药种类在冷冻干燥和热风干燥中的损失不同,有机磷农药比拟除虫菊酯类农药的损失大,与有机磷农药的蒸汽压较高、稳定性差相关。冻干过程对农药造成的损失与农药的溶解度有关,而烘干过程对农药造成的损失与农药的蒸汽压和热稳定性有关。试验农药中溶解度最大的乐果在冻干过程中损失最小,而蒸汽压最大的马拉硫磷在烘干过程中损失最大。     

真空法降低油炸制品含油量

以圆柱形土豆条为研究对象,对油炸和冷却过程中样品表面和内部温度、水蒸气压力以及不同阶段吸油量变化规律进行测量与分析,发现油炸过程中由于水蒸气持续从多孔壳层逸出,阻碍了油进入食品中,土豆样品中70%左右油是在冷却阶段进入食品壳层中的,而且导致吸油的动力--蒸汽冷凝形成的壳层内外压差对环境气压很敏感。在油炸样品冷却阶段,将油炸土豆条置于不同真空环境进行冷却,发现绝对压力80kPa的条件下冷却时,总吸油率从40%降至13.6%,说明冷却过程的真空条件能降低壳层内、外压差驱动力,有效促进表面附着油滴落,阻碍其被吸入食品结构中,从而降低油含量。     

Thermodynamic properties of multifunctional oxygenates in atmospheric aerosols from quantum mechanics and molecular dynamics: dicarboxylic acids

Ambient particulate matter contains polar multifunctional oxygenates that partition between the vapor and aerosol phases. Vapor pressure predictions are required to determine the gas-particle partitioning of such organic compounds. We present here a method based on atomistic simulations combined with the Clausius-Clapeyron equation to predict the liquid vapor pressure, enthalpies of vaporization, and heats of sublimation of atmospheric organic compounds. The resulting temperature-dependent vapor pressure equation is a function of the heat of vaporization at the normal boiling point [deltaHvap(Tb)], normal boiling point (Tb), and the change in heat capacity (liquid to gas) of the compound upon phase change [deltaCp(Tb)]. We show that heats of vaporization can be estimated from calculated cohesive energy densities (CED) of the pure compound obtained from multiple sampling molecular dynamics. The simulation method (CED) uses a generic force field (Dreiding) and molecular models with atomic charges determined from quantum mechanics. The heats of vaporization of five dicarboxylic acids [malonic (C3), succinic (C4), glutaric (C5), adipic (C6), and pimelic (C7)] are calculated at 500 K. Results are in agreement with experimental values with an averaged error of about 4%. The corresponding heats of sublimation at 298 K are also predicted using molecular simulations. Vapor pressures of the five dicarboxylic acids are also predicted using the derived Clausius-Clapeyron equation. Predicted liquid vapor pressures agree well with available literature data with an averaged error of 29%, while the predicted solid vapor pressures at ambient temperature differ considerably from a recent study by Bilde et al. (Environ. Sci. Technol. 2003, 37, 1371-1378) (an average of 70%). The difference is attributed to the linear dependence assumption thatwe used in the derived Clausius-Clapeyron equation.     

A new method for separating HFC-134a from gas mixtures using clathrate hydrate formation

A new separation method using gas hydrate formation is proposed for separating HFC-134a from gas mixtures containing N2 and HFC-134a. The feasibility of this separation method was investigated from various points of view. First, to determine the mixed hydrate stability region, three-phase equilibria of hydrate (H), liquid water (Lw), and vapor (V) for HFC-134a + N2 + water mixtures with various HFC-134a vapor compositions were closely examined in the temperature and pressure ranges of 275-285 K and 0.1-2.7 MPa, respectively. Second, the compositions of the hydrate and vapor phases at a three-phase equilibrium state were analyzed for identical mixtures at 278.15 and 282.15 K to confirm the actual separation efficiency. Third, kinetic experiments were performed to monitor the composition change behavior of the vapor phase and to determine the time required for an equilibrium state to be reached. Furthermore, X-ray diffraction confirmed that the mixed HFC-134a + N2 hydrates were structure II. Through an overall investigation of the experimental results, it was verified that more than 99 mol % HFC-134a could be obtained from gas mixtures after hydrate formation and subsequent dissociation processes. Separation of HFC-134a using hydrate formation can be carried out at mild temperature and low-pressure ranges. No additive is needed to lower the hydrate formation pressure.