Newly designed superheated steam dryer bearing heat recovery unit: Analysis of energy efficiency and kinetics of Kelp drying

In this work, a newly designed superheated steam dryer (SSD) bearing exhaust heat recovery unit (RD) was fabricated. The dryer was designed for the superheated steam (SS) to be generated by foodstuff being dried, and the latent heat of the exhaust SS was recovered by microtube radiators and exploited to heat the RD unit. The system was then applied in Kelp drying, in which the drying kinetics was analyzed and fitted with mathematical models. The energy efficiency by the system was further evaluated and compared with hot air (HA)-drying. The results showed that the Kelp drying process in SSD could be described by two stages: heat-upstage (stage I) and superheated steam stage (stage II). While in stage I, different heat-up times of 10, 15, and 20?min were required to generate superheated steam at temperatures of 110–150°C, in stage II, the moisture content in Kelp was decreased to approximately 50?±?5% (wet basis) within 60, 50, and 30?min at 110, 130, and 150°C, respectively. Moreover, the Midilli and Kucuk model best described Kelp drying curve in both stages, whereas the logarithmic model best fitted with that in stage II. Finally, the energy efficiency for SSD-RD was in the range of 1.127–1.425?kWh/kg_water compared with 2.406–2.508?kWh/kg_water for HA operating under the same conditions, demonstrating that the SSD-RD was able to reduce the energy input by at least 46.14%.     

Moisture equilibrium of wood and bark chips in superheated steam

This study relating to the steam drying of biofuels suggests that the activities of water in air (defined as relative humidity) and of water in superheated steam (defined as the ratio of the saturated pressure and the saturated pressure at the superheated temperature) are identical. The dependence of the activity in superheated steam on the equilibrium moisture content was studied in various experiments for different wood materials at constant temperatures of 140 and 160°C. The equilibrium moisture content was found to depend on the following factors: the activity of the superheated steam, the temperature and the materials used, the first of these being the most important. The experimentally determined sorption isotherms were compared with different sorption theories. The Dent model gave a good correlation with the experimental data. The sorbed water can be divided into primary water with high binding energy and secondary water with low binding energy. If biofuels are to be dried with superheated steam, an equilibrium moisture fraction of 0.05 seems to be relevant. It will probably be possible to reach this with activities in the range 0.2–0.4 for all real materials.     

Sugarcane Bagasse Drying in a Cyclone: Influence of Device Geometry and Operational Parameters

Sugarcane bagasse is becoming more and more commonly used in generating electrical energy, steam, and bioethanol. Drying is important in sugarcane and other types of biomass because it can be used to improve the calorific value and overall energetic use. In this work, sugarcane bagasse was treated by drying in a cyclonic dryer. The influence of the geometry of the device (the conical part of the cyclone) and process parameters (bagasse mass flow rate and temperature) were tested. The modification on the conical part was related to two different angles and with two different inferior outlets (B). Experimental design was carried out for each geometry. The independent variables were the drying agent temperature (35 to 275°C) and the bagasse mass flow rate (0.1 × 10^?2 to 2.9 × 10^?2 kg s^?1). The air flow rate was kept constant at 7.5 × 10^?2 kg s^?1. The dependent variables were moisture reduction (MR) and average particle residence time (t_res) in the cyclonic dryer. For both cyclonic geometries, it was observed that MR was directly proportional to the temperature and inversely proportional to the bagasse mass flow rate. t_res was also inversely proportional to the bagasse mass flow rate. Decreasing B tended to increase tres and MR.     

软木干燥中湿空气和过热蒸汽的外部传热

In kiln drying of softwood timber, external heat and moisture mass transfer coefficients are important in defining boundary temperature and moisture content at the wood surface. In addition, superheated steam drying of wood is a promising technology but this has not been widely accepted commercially, partially due to the lack of understanding of the drying phenomena occurred during drying. In this work, experimental investigation was performed to quantify the heat transfer between wood surface and surrounding moist air or superheated steam. In the experiment, saturated radiata pine sapwood samples were dried using dry-bulb/wet-bulb temperatures of 60℃/50℃,90℃/60℃, 120℃/70℃, 140℃/90℃, 160℃/90℃, 140℃/100℃ and 160℃/100℃. The last two schedules were for superheated steam drying as the wet-bulb temperature was set at 100℃. The circulation velocity over the board surface was controlled at 4.2 m·s-1. Two additional runs (90℃/60℃) using air velocities of 2.4 m·s-1 and 4.8 m·s-1were performed to check the effect of the circulation velocity. During drying, sample weight and temperatures at wood surface and different depths were continuously measured. From these measurements, changes in wood temperature and moisture content were calculated and external heat-transfer coefficient was determined for both the moist air and the superheated steam drying.     

蒸气凝结水回收系统中常见问题的解决与探讨

指出蒸气凝结水回收的重要性的同时对炼油厂蒸气凝结水回收系统中存在的诸如水击、非凝结性气体不能排除、气阻及疏水阀的选型安装等问题的解决办法进行了探讨。从而达到余热利用,节约能源,保护环境,降低生产成本的目的。     

Influence of temperature and permeate recovery on energy consumption of a reverse osmosis system

A model permits analysis of the influence of temperature on permeate recovery and energy consumption. The proposed model is based on the following assumptions: (1) membrane morphology is temperature-independent; (2) membrane rejection and other transport characteristics of membranes are position-independent; (3) specific water permeability of membranes was based on exponential dependence of viscosity vs. temperature; (4) temperature-dependence depembrane rejection is assumed to be linear. This allows for analyzing the influence of channel geometry, feed concentration, flow rate and temperature on permeate recovery and energy consumption. Calculated data are included. The solutionpresented can be segmented andbuilt into systems for comprehensive techno-economic evaluation of the RO-based process where temperature-dependence of process characteristics has to be considered.     

基于梯级用水的工业水系统节水优化研究

水系统节水优化是一种从系统层面分析水系统节水潜力的方法,借助数学模型可实现节水的量化研究。阐述了一种基于外排水再利用的水系统节水优化模型,并利用Vogel方法实现模型的求解。以火电企业为典型用水案例进行研究,将案例企业用水系统划分为6个子系统(循环冷却水系统、灰渣水系统、化学除盐水系统、脱硫用水系统、生活消防用水系统、其他杂用水系统),在污水排放改造的基础上构建了基于成本最优的节水优化模型并进行了求解。经案例研究发现,优化带来的经济效益最为明显,其次是节水、生态效益。案例企业优化后综合发电耗水、总用水成本、新鲜水取用量降幅分别为10.3%、13.6%、11.2%,对缓解当地水环境污染以及地下水开采压力具有积极意义。     

循环冷却水系统节水试验及改造方案

介绍了大化集团合成氨厂循环冷却水系统的实际运行状态和大连城市供水及节水状况。拟利用电渗析器脱盐技术，高效表面膜过滤器脱浊技术和臭氧发生器杀菌技术，对合成氨厂循环冷却水系统进行改造，以达到提高经济效益，降低排污和节水的目的。     

蒸发系统循环水泵节电改造

介绍了一种专用节电集成系统在烧碱蒸发工序大功率电机的循环水泵上应用的试验情况,以及该系统在具体实施中的经验与方法。试验结果表明,节电效果明显。     

硫酸厂循环冷却水系统节水降耗措施

介绍四川省德铭投资有限公司硫酸厂120kt／a硫铁矿制酸装置循环冷却水系统在设计中的节水降耗措施。共设置4台逆流式机械通风玻璃钢冷却塔，各工段冷却水独立循环使用；增设了旁滤系统和加药系统，以满足循环水系统的水质要求；同时合理提高设计浓缩倍数，减少排污水量和补充水量，达到节水降耗目的。     

Experimental and theoretical analysis of the operation of a natural gas cogeneration system using a polymer exchange membrane fuel cell

This paper reports experimental and numerical results of an investigation of five identical cogeneration systems using PEM (Polymer Exchange Membrane) fuel cells and running on natural gas. The natural gas is reformed locally to produce hydrogen. The accuracy of numerical results is validated by comparison with experimental data and the system performances are analysed in terms of electrical, thermal and total efficiencies. It appears that the energetic performances are low, particularly at low current. Simple solutions for enhancing the system electrical performances by modifying control laws are proposed.     

工业循环冷却水系统节水节能措施分析

结合当前水资源缺乏的严峻形势,立足设计细节,阐述了工业循环冷却水系统节水、节能具有很大的潜力.从工程设计的角度,提出了提高换热设备冷却水供回水温差,调整冷却塔风机运行方式,采用单独的循环冷却水系统低压给水系统,收集、处理后回用循环冷却水排污水,以及综合考虑换热器和循环冷却水系统的安全系数等措施,可减少资源浪费、节约用水...     

东滩选煤厂节水型选煤系统的运转实施

介绍了节水型选煤系统在东滩煤矿选煤厂的成功应用, 为同类型矿区实现社会、经济、资源及环境的协调发展, 减缓煤矿区生态系统环境的恶化, 实现煤炭工业可持续发展的最终目标提供了宝贵经验。     

冷却循环水系统的稳压与节能改造

为解决供水压力波动大的问题，采用交流变频调速器，PLC和压力控制单元等主要部件对冷却循环水供水系统进行了自动控制改造。在改造后的控制系统中，解决了用水变化量较大，难以控制的问题，并使供水压力保持恒定，同时大大地节约了电能。     

低热值燃料电厂循环水系统节能与凉水塔防冰凌研究

介绍了华聚能源各电厂循环水冷却系统的运行情况;以兴隆庄矿热电厂为例,论述了冬季供暖期间循环冷却水系统的优化运行措施及效益,并提出了几种实用的防止凉水塔结冰的具体措施。     

制酸熔硫系统乏汽及其凝结水回收装置的优化设计

针对大型硫黄制酸熔硫系统乏汽及其凝结水温度、压力特点,开发一种可操作的乏汽及其凝结水回收方法。介绍需要的设备和工艺流程,对回收难点提出针对性的解决方法,最大限度实现余热的回收再利用。该方法可显著提高余热回收利用量,减少原始新蒸汽的用量,降低熔硫系统生产成本,年产生经济效益900万元以上。     

VCM回收系统生产工艺的优化与改造

介绍了陕西北元化工集团股份有限公司VCM回收系统的工艺流程,针对VCM回收系统回收能力不足的问题进行了优化和改造.优化与改造后,VCM回收系统运行平稳,负荷运行能力得到了大幅度提高.     

Influence of pre-soaking conditions on ultrasonic extraction of Spirulina platensis proteins and its recovery using aqueous biphasic system

Ultrasonic aqueous extraction of proteins from dry Spirulina platensis at acidic (ACSU), alkali (ALSU), and neutral (NSU) conditions and its recovery using aqueous biphasic system (ABS) was studied. S. platensis was soaked in the solvent for 12 h prior to extraction. Neutral condition showed a higher protein release of 18.6 mg/ml at optimum conditions (solid–liquid ratio 1:20, 80% ultrasound amplitude, 100% ultrasound duty cycle, and 4ºC). The Box–Behnken design (BBD) suggested optimum conditions for ABS (PEG 6000, pH 8, and 5% NaCl) and gave 84.1% recovery. Although microscopic observations indicated structural changes, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier-transform infrared spectroscopy (FTIR) analyses confirmed that the proteins are intact.     

Kinetics of cellobiose decomposition under subcritical and supercritical water in continuous flow system

The effects of reaction temperature, pressure and residence time were investigated with a flow apparatus. Cellobiose decomposition kinetics and products in suband supercritical water were examined at temperatures from 320 to 420 °C at pressures from 25 to 40 MPa, and at residence times within 3 sec. Cellobiose was found to decompose via hydrolysis and pyrolysis. The yield of desired hydrolysis product, glucose, was the maximum value of 36.8% at 320 °C, 35 MPa, but the amount of 5-(hydroxymethyl)furfural (HMF), fermentation inhibitor increased too because residence time increased in the subcritical region owing to decrease of reaction rate. Meanwhile, though the yield of glucose is low in the supercritical region, the yield of HMF decreased compared with the subcritical region; and at the minimum yield of HMF (380 °C, 25 MPa), the yield of glucose was 21.4%. The decomposition of cellobiose followed first-order kinetics and the activation energy for the decomposition of cellobiose was 51.05 kJ/mol at 40MPa.