响应面法优化超临界CO2萃取北五味子藤茎油工艺

利用超临界CO2 萃取技术,在单因素试验的基础上,采用中心组合响应面法,建立北五味子藤茎挥发油超临界CO2 萃取的回归模型。研究结果表明,萃取压力、萃取温度、CO2 流速对萃取率的影响显著,萃取压力和CO2 流速以及萃取温度和CO2 流速的交互效应影响显著,解析矩阵可知,在萃取压力36.32MPa,萃取温度42.27℃、CO2 流速17.01L/h,预测最大萃取率为0.432%,验证实验证实该方程有很好的拟合度。该方法具有萃取率高、污染小、节约能源的特点。     

Water use at pulverized coal power plants with postcombustion carbon capture and storage

Coal-fired power plants account for nearly 50% of U.S. electricity supply and about a third of U.S. emissions of CO(2), the major greenhouse gas (GHG) associated with global climate change. Thermal power plants also account for 39% of all freshwater withdrawals in the U.S. To reduce GHG emissions from coal-fired plants, postcombustion carbon capture and storage (CCS) systems are receiving considerable attention. Current commercial amine-based capture systems require water for cooling and other operations that add to power plant water requirements. This paper characterizes and quantifies water use at coal-burning power plants with and without CCS and investigates key parameters that influence water consumption. Analytical models are presented to quantify water use for major unit operations. Case study results show that, for power plants with conventional wet cooling towers, approximately 80% of total plant water withdrawals and 86% of plant water consumption is for cooling. The addition of an amine-based CCS system would approximately double the consumptive water use of the plant. Replacing wet towers with air-cooled condensers for dry cooling would reduce plant water use by about 80% (without CCS) to about 40% (with CCS). However, the cooling system capital cost would approximately triple, although costs are highly dependent on site-specific characteristics. The potential for water use reductions with CCS is explored via sensitivity analyses of plant efficiency and other key design parameters that affect water resource management for the electric power industry.     

Assessment of potential carbon dioxide reductions due to biomass-coal cofiring in the United States

Cofiring biomass with coal in existing power plants offers a relatively inexpensive and efficient option for increasing near-term biomass energy utilization. Potential benefits include reduced emissions of carbon dioxide, sulfur, and nitrogen oxides and development of biomass energy markets. To understand the economics of this strategy, we develop a model to calculate electricity and pollutant mitigation costs with explicit characterization of uncertainty in fuel and technology costs and variability in fuel properties. The model is first used to evaluate the plant-level economics of cofiring as a function of biomass cost. It is then integrated with state-specific coal consumption and biomass supply estimates to develop national supply curves for cofire electricity and carbon mitigation. A delivered cost of biomass below 15 dollars per ton is required for cofire to be competitive with existing coal-based generation. Except at low biomass prices (less than 15 dollars per ton), cofiring is unlikely to be competitive for NOx or SOx control, but it can provide comparatively inexpensive control of CO2 emissions: we estimate that emissions reductions of 100 Mt-CO2/year (a 5% reduction in electric-sector emissions) can be achieved at 25 +/- 20 dollars/tC. The 2-3 year time horizon for deployment--compared with 10-20 years for other CO2 mitigation options--makes cofiring particularly attractive.     

片烟在线调控技术在细支卷烟生产中的应用研究

  目的  提升细支卷烟烟丝结构均匀性。  方法  设计开发了片烟在线调控单元,主要由大片筛分提取、叶片旋转分切和细梗分离净化等装置组成。  结果  在制丝线开展了对比试验,表明⑴在线调控模式对烟片结构有效调整,中、短丝率得以提高;⑵原料利用率降低0.29百分点,单箱原料消耗有所增加;⑶卷包机台的生产效率明显提高,总剔除率、残烟量明显下降;⑷卷烟物理指标和主流烟气指标批间的稳定性明显提高,其中单支质量标偏、开放吸阻标偏和总通风率标偏分别下降8.84%、12.70%和18.41%,焦油、烟碱和CO标准偏差分别下降89.92%、24.07%和32.09%;⑸配方烟丝结构和烟支烟丝密度分布的均匀性明显提高,卷烟感官质量保持稳定。  结论  说明采用片烟在线调控模式对于优化细支卷烟烟丝结构具有显著作用,有利于提升产品质量的稳定性。      

Geometrical model to calculate the consumption of sewing thread for 301 lockstitch

Sewing thread is one of the most basic yet important components of a garment. Thread consumption for the lockstitch (Class 301) can be calculated by using its geometrical shape. This paper aims to develop a geometrical model to calculate the thread consumption for lockstitch (Class 301). Based on the basic geometry of lockstitch, a model has been proposed. The model is derived mathematically taking into account different variables: stitch length, stitch density, material thickness, and interlacing. Finally, the model was verified for 19 samples by comparing actual thread consumption with predicted thread consumption. The proposed model predicts the thread consumption with 97% accuracy. Sensitivity analysis is also performed to determine the significant influencing factor affecting the thread consumption. The proposed model can predict the thread consumption precisely for 301 lockstitch. Therefore, this model is useful for the apparel industry.     

Compilation and application of Japanese inventories for energy consumption and air pollutant emissions using input-output tables

Preparing emission inventories is essential to the assessment and management of our environment. In this study, Japanese air pollutant emissions, energy consumption, and CO2 emissions categorized by approximately 400 sectors (as classified by Japanese input-output tables in 1995) were estimated, and the contributions of each sector to the total amounts were analyzed. The air pollutants examined were nitrogen oxides (NOx), sulfur oxides (SOx), and suspended particulate matter (SPM). Consumptions of about 20 fossil fuels and five other fuels were estimated according to sector. Air pollutant emission factors for stationary sources were calculated from the results of a survey on air pollution prevention in Japan. Pollutant emissions from mobile sources were estimated taking into consideration vehicle types, traveling speeds, and distances. This work also counted energy supply and emissions from seven nonfossil fuel sources, including nonthermal electric power, and CO2 emissions from limestone (for example, during cement production). The total energy consumption in 1995 was concluded to be 18.3 EJ, and the annual total emissions of CO2, NOx, SOx, and SPM were, respectively, 343 Mt-C, 3.51 Mt, 1.87 Mt, and 0.32 Mt. An input-output analysis of the emission inventories was used to calculate the amounts of energy consumption and emissions induced in each sector by the economic final demand.     

The right place for the right job in the photovoltaic life cycle

The potential for photovoltaic power generation (PV) to reduce primary energy consumption (PEC) and CO(2) emissions depends on the physical locations of each stage of its life cycle. When stages are optimally located, CO(2) emissions are reduced nearly ten times as much as when each stage is located in the country having the largest current market share. The usage stage contributes the most to reducing CO(2) emissions and PEC, and total CO(2) emissions actually increase when PV is installed in countries having small CO(2) emissions from electricity generation. Global maps of CO(2) reduction potential indicate that Botswana and Gobi in Mongolia are the optimal locations to install PV due to favorable conditions for PV power generation and high CO(2) emissions from current electricity generation. However, the small electricity demand in those countries limits the contribution to global CO(2) reduction. The type of PVs has a small but significant effect on life cycle PEC and CO(2) emissions.     

板栗微波真空干燥特性及干燥工艺研究

研究微波真空干燥方式下,微波强度、腔体压力等参数对板栗干燥过程中质热传递的影响规律。采用Box-Behnken中心组合试验设计,以水分含量和白度值为评价指标,确定板栗微波真空干燥过程中微波功率、压力、干燥时间的最适工艺参数。结果显示:板栗微波真空干燥过程主要为加速和降速阶段,恒速阶段持续时间较短。微波功率和真空度均对干燥时间有显著影响,功率越大,真空度越高,干燥速率越快,干基含水率和水分比都随着干燥时间的延长而逐渐下降。由回归模型得出板栗微波真空干燥的最佳工艺参数为时间12min,压力-56kPa,功率3kW。微波真空干燥的微波功率、腔体压力、干燥时间均对板栗品质有影响,以模型得出的干燥参数进行干燥,可保证板栗干燥后的品质,且干燥效率高、能耗低。     

Novel electromagnetic-black-hole-based high-efficiency single-mode microwave liquid-phase food heating system

Microwave heating exhibits a high potential for usage in liquid food processing. Current microwave heating systems are designed for a specific load. However, when the permittivity of the load changes dynamically, the heating efficiency of these systems fluctuates considerably. We proposed a novel high-efficiency microwave liquid heating system for dynamic dielectric loads to address this limitation. In this system, an electromagnetic black hole efficiently absorbs electromagnetic waves in all directions. First, an electromagnetic black hole was realized using metamaterials (which means artificially structured dielectric materials with extraordinary physical properties) with a radially continuous refractive index distribution. Next, an electromagnetic field simulation model was established to calculate the microwave absorption of various load permittivity. To discretize and simplify the parameters of the continuous distribution in an electromagnetic black hole, a concentric layered structure and a punched structure composed of uniform isotropic dielectric materials were designed. Finally, the experimental samples were processed based on the two discrete structures. The microwave system developed for experimental verification confirmed the high efficiency of the heating system; the system is simple and usable in numerous applications. Thus, the proposed method can realize high-efficiency heating of loads over large dielectric dynamic ranges. When the dielectric constant of the load changed dynamically from 10 to 80, the microwave energy utilization rate can increase by up to 90%.     

Fluidized bed combustion systems integrating CO2 capture with CaO

Capturing CO2 from large-scale power generation combustion systems such as fluidized bed combustors (FBCs) may become important in a CO2-constrained world. Using previous experience in capturing pollutants such as SO2 in these systems, we discuss a range of options that incorporate capture of CO2 with CaO in FBC systems. Natural limestones emerge from this study as suitable high-temperature sorbents for these systems because of their low price and availability. This is despite their limited performance as regenerable sorbents. We have found a range of process options that allow the sorbent utilization to maintain a given level of CO2 separation efficiency, appropriate operating conditions, and sufficiently high power generation efficiencies. A set of reference case examples has been chosen to discuss the critical scientific and technical issues of sorbent performance and reactor design for these novel CO2 capture concepts.     

Sensitivity analysis for high quantiles of ochratoxin A exposure distribution

Using available data from a consumption survey and contamination data on ochratoxin A (OA) in food, a sensitivity analysis (SA) for high quantiles (95th and 99th quantiles) of OA exposure distribution was carried out, obtained by a Monte Carlo simulation in French children. Exposure assessment for food contaminants is important to control the risk of foodborne diseases. Risk assessors are interested in high quantiles of contaminant exposure distributions. As these exposure distributions are generally very asymmetrical, it is difficult to obtain relevant and stable high quantiles in such a context. Determining OA exposure distribution is complex because it is based on the sum of elementary exposure distributions (eight foodstuffs are analysed here), and each one of these is the product of a consumption distribution and a contamination distribution. The SA enables us to quantify the influences of the parameter variability of the consumption and contamination probability density functions (pdf) which have been fitted to the data, our simulation model inputs, on the 95th and 99th quantiles of the output exposure distribution. After some preliminary trials, we have postulated a quadratic polynomial regression model for the quantiles of OA exposure distribution in view of undertaking this SA. This regression model comprises 32 main factors, their 496 two-factor interactions and their 32 quadratic terms. The 32 factors are the parameters of the fitted pdf: 16 parameters of Gamma distributions relative to the eight consumed foods and 16 parameters of Gamma distributions relative to the eight food OA contaminations. For an optimal parameter estimation of such a large model, we used an experimental design approach depending on a resolution-V fractional factorial design of 6561 experiments. The factor ranges are established by a preliminary study of bootstrap sampling. From the bootstrap samples, the factor ranges are obtained taking into account the correlation between the two parameters of the fitted Gamma pdf. A full exposure distribution is simulated for each of the 6561 experiments. The consumption dependencies are taken into account by the Iman and Conover method. On the basis of this analysis, validated and useful models for each desired quantile are obtained showing a major influence of the parameters of "Cereals" (consumption and contamination) and slightly less so for parameter of "Pork" consumption in the sensitivity of the quantiles.     

Costs of Solar and Wind Power Variability for Reducing CO(2) Emissions

We compare the power output from a year of electricity generation data from one solar thermal plant, two solar photovoltaic (PV) arrays, and twenty Electric Reliability Council of Texas (ERCOT) wind farms. The analysis shows that solar PV electricity generation is approximately one hundred times more variable at frequencies on the order of 10(-3) Hz than solar thermal electricity generation, and the variability of wind generation lies between that of solar PV and solar thermal. We calculate the cost of variability of the different solar power sources and wind by using the costs of ancillary services and the energy required to compensate for its variability and intermittency, and the cost of variability per unit of displaced CO(2) emissions. We show the costs of variability are highly dependent on both technology type and capacity factor. California emissions data were used to calculate the cost of variability per unit of displaced CO(2) emissions. Variability cost is greatest for solar PV generation at $8-11 per MWh. The cost of variability for solar thermal generation is $5 per MWh, while that of wind generation in ERCOT was found to be on average $4 per MWh. Variability adds ～$15/tonne CO(2) to the cost of abatement for solar thermal power, $25 for wind, and $33-$40 for PV.     

Energy and material balance of CO2 capture from ambient air

Current Carbon Capture and Storage (CCS) technologies focus on large, stationary sources that produce approximately 50% of global CO2 emissions. We propose an industrial technology that captures CO2 directly from ambient air to target the remaining emissions. First, a wet scrubbing technique absorbs CO2 into a sodium hydroxide solution. The resultant carbonate is transferred from sodium ions to calcium ions via causticization. The captured CO2 is released from the calcium carbonate through thermal calcination in a modified kiln. The energy consumption is calculated as 350 kJ/mol of CO2 captured. It is dominated by the thermal energy demand of the kiln and the mechanical power required for air movement. The low concentration of CO2 in air requires a throughput of 3 million cubic meters of air per ton of CO2 removed, which could result in significant water losses. Electricity consumption in the process results in CO2 emissions and the use of coal power would significantly reduce to net amount captured. The thermodynamic efficiency of this process is low but comparable to other "end of pipe" capture technologies. As another carbon mitigation technology, air capture could allow for the continued use of liquid hydrocarbon fuels in the transportation sector.     

High throughput screening of CO2 solubility in aqueous monoamine solutions

Post-combustion Carbon Capture and Storage technology (CCS) is viewed as an efficient solution to reduce CO(2) emissions of coal-fired power stations. In CCS, an aqueous amine solution is commonly used as a solvent to selectively capture CO(2) from the flue gas. However, this process generates additional costs, mostly from the reboiler heat duty required to release the carbon dioxide from the loaded solvent solution. In this work, we present thermodynamic results of CO(2) solubility in aqueous amine solutions from a 6-reactor High Throughput Screening (HTS) experimental device. This device is fully automated and designed to perform sequential injections of CO(2) within stirred-cell reactors containing the solvent solutions. The gas pressure within each reactor is monitored as a function of time, and the resulting transient pressure curves are transformed into CO(2) absorption isotherms. Solubility measurements are first performed on monoethanolamine, diethanolamine, and methyldiethanolamine aqueous solutions at T = 313.15 K. Experimental results are compared with existing data in the literature to validate the HTS device. In addition, a comprehensive thermodynamic model is used to represent CO(2) solubility variations in different classes of amine structures upon a wide range of thermodynamic conditions. This model is used to fit the experimental data and to calculate the cyclic capacity, which is a key parameter for CO(2) process design. Solubility measurements are then performed on a set of 50 monoamines and cyclic capacities are extracted using the thermodynamic model, to asses the potential of these molecules for CO(2) capture.     

猪肉的微波干燥与能耗分析

目的:探究猪肉微波干燥特性,优化肉类微波干燥过程.方法:采用微波频率为2 450 MHz,微波输出功率为70,140,210,280,350,420 W的微波干燥设备,对干燥质量为20,25,30 g的猪肉进行微波干燥处理;并选用5种经典薄层干燥模型对干燥数据进行非线性拟合,以均方根误差和决定系数为评价指标,筛选出最佳...     

State-level infrastructure and economic effects of switchgrass cofiring with coal in existing power plants for carbon mitigation

This paper presents a linear programming (LP) methodology for estimating the cost of reducing a state's coal-fired power plant carbon dioxide emissions by cofiring switchgrass and coal. LP modeling allows interplay between regionally specific switchgrass production forecasts, coal plant locations, and individual coal plant historic performance data to determine an allocation of switchgrass minimizing cost or maximizing carbon reduction. The LP methodology is applied to two states, Pennsylvania (PA) and Iowa (IA), and results are presented with a discussion of modeling assumptions, techniques, and carbon mitigation policy implications. The LP methodology estimates that, in PA, 4.9 million tons of CO2/year could be mitigated at an average cost of less than $34/ton of CO2 and that, in IA, 7 million tons of CO2/year could be mitigated at an average Cost of Mitigation of $27/ton of CO2. Because the factors determining the cofiring costs vary so much between the two states, results suggest that cofiring costs will also vary considerably between different U.S. regions. A national level analysis could suggest a lowest-cost cofiring region. This paper presents techniques and assumptions that can simplify biomass energy policy analysis with little effect on analysis conclusions.     

Influence of mobile air-conditioning on vehicle emissions and fuel consumption: a model approach for modern gasoline cars used in Europe

The influence of air-conditioning activity on the emissions and fuel consumption of passenger cars is an important issue, since fleet penetration and use of these systems have reached a high level. Apart from the MOBILE6 study in the United States, little data is available on the impact of air-conditioning devices (A/Cs). Since weather conditions and A/C technologies both differ from those in the U. S., a test series was designed for the European setting. A fleet of six modern gasoline passenger cars was tested in different weather conditions. Separate test series were carried out for the initial cooldown and for the stationary situation of keeping the interior of the vehicle cool. As assumed, CO2 emissions and fuel consumption rise with the thermal load. This also causes a notable rise in CO and hydrocarbons (HCs). Moreover, A/Cs do not stop automatically at low ambient temperatures; if necessary, they produce dry air to demist the windscreen. A model is proposed that shows a constant load for lower temperatures and a linear trend for higher temperatures. The initial cooldown tests highlight significant differences among cars but show that A/C operation for the initial cooling of an overheated passenger compartment does not result in any extra emissions for the fleet as a whole.     

Shelf life prediction of bread sticks using oxidation indices: a validation study

ABSTRACT:  The aim of this study was to apply the protocol for the shelf life prediction of bakery products proposed by Calligaris and others (2007a) on bread sticks. The methodology comprises 4 steps: (1) evaluation of the physical properties of fat; (2) performing the accelerated shelf life test; (3) evaluation of sensory acceptance limit and the relevant chemical index limit; (4) setting up the shelf life prediction model. The results allow validating the shelf life prediction methodology proposed. In fact, the peroxide number was found to be a representative index of the quality depletion of bread sticks during their shelf life. In addition, once again by accounting for the changes in the fat physical state, it is possible to set up a modified Arrhenius equation able to describe the temperature dependence of peroxide formation. Finally, a mathematical model to simply and quickly calculate the shelf life of bread sticks has been developed.     

燃煤锅炉烟气氨法脱硝实时监测系统

为监测火电厂锅炉烟气氨法脱硝过程中的氨气泄漏情况,利用GSM,Internet和ZigBee等多种技术,设计了一个集采集、报警、查询为一体的监测系统,实现了用无线传感器网络对氨法脱硝系统运行环境进行分布式液氨泄漏监测.该系统能有效提高氨法脱硝现场的安全性,具有低功耗、低单位成本和组网灵活等优点.     

Numerical computation of relaxation spectra from mechanical measurements in biopolymers

In the present investigation, a computational methodology to treat relaxation spectra from mechanical data is developed. To calculate the spectral function that represents the relaxation process of the material, three different regularization algorithms were tested using MATLAB. Two algorithms employ Tikhonov’s regularization whereas the third investigative tool is an implementation of the CONTIN algorithm. These efforts improved the ability to look at data hence allowing utilization of the L-curve criterion in order to locate the optimum regularization parameter for accurate data inversion. Algorithms were first evaluated with hypothetical data followed by experimental datasets of hydrated gluten as a model biopolymer system. Essentially, algorithms converge on a specific relaxation spectrum that unveils the molecular features of gluten structure. The methodology described is not limited to mechanical measurements but should be used with any type of exponential decay in studies of relaxation processes.