Prediction of Water Vapor Movement through Waste Rock

Evaporative losses from the surface of barren waste rock piles in arid environments occur as a result of water vapor diffusion. Water vapor diffusion is accompanied by adsorption of water vapor. A review of the literature found that adsorption of water vapor is commonly described as a sigmoidal function of suction with a predominant linear portion when plotted against the log of suction. Laboratory column tests were conducted with glass beads and waste rock to study water vapor diffusion. A monitoring system was developed for measuring relative humidity and temperature through the column. Water vapor fluxes and relative humidity profiles through the column were measured under steady-state conditions to establish the method of estimating the water vapor diffusion coefficient. Transient water vapor fluxes and relative humidity profiles were measured and a numerical model was developed to simulate the laboratory observations. The numerical model demonstrated the importance of water sorption in controlling the transient water vapor flux. Sorption described as a log–linear function of suction gave reasonable results for the numerical modeling of the glass beads and waste rock.     

Pervaporation of Water/Ethanol Mixtures by an Aromatic Polyetherimide Membrane

Abstract

The pervaporation of water/ethanol mixtures through an aromatic polyetherimide membrane was attempted. The membrane was laboratory prepared using the solution casting technique. The sorption characteristics in relation to pervaporation were also studied. It was found that the preferential sorption was altered when the liquid composition was changed, whereas the water component permeated through the membrane preferentially over the whole range of feed mixture compositions. The experimental results were analyzed in terms of sorption ratio and permeation ratio to characterize nonideality of sorption and pervaporation. The effects of some operating parameters, including temperature, feed concentration, and permeate pressure, on the pervaporation performance were also investigated.     

Moisture Sorption Isotherms and Storage Stability of Spray-Dried Yogurt Powder

Moisture adsorption isotherms of spray-dried yogurt powder were determined at 10, 25, and 40°C using the standard, static-gravimetric method. Experimental data were fitted to five mathematical models (Guggenheim-Anderson-de Boer [GAB], Brunauer-Emmett-Teller [BET], Halsey, modified Oswin, and modified Henderson). A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. The shelf-life of yogurt powder was predicted based on the relationship between permeability coefficient of the packaging material and moisture adsorbed by the powder determined by the GAB equation. Furthermore, the storage stability of spray-dried yogurt powder in terms of quality parameters including moisture content, water activity, color change, and thiobarbituric acid (TBA) value was studied in aluminum laminated polyethylene (ALPE) pouches under storage conditions of 25°C and 50% relative humidity (RH).     

A rapid and novel approach for predicting water sorption isotherms and isosteric heats of different meat types

A rapid and novel approach for predicting sorption isotherms based on the Polanyi theory is proposed. This approach allows the prediction of the sorption isotherms at different temperatures from one experimental isotherm. The theoretical predictions of isotherms and isosteric heats were validated successfully using data from the literature for different meat types. This method allows total experimental time and operation costs to be reduced.     

钨湿法冶炼氨的回用

钨湿法冶炼过程中产生的含氨废气是主要的气性污染源， 根据氨在水中溶解度， 将含水蒸汽和氨气的废气进行冷凝和加热处理， 氨水蒸汽分离， 分离率为９４ ％ ～９５ ％ ，氨进行冷却吸收，回收的氨水全部回用于生产，有效高的经济和社会效益。     

Investigation of Consolidation-Induced Solute Transport. I: Effect of Consolidation on Transport Parameters

This paper presents an experimental investigation of the effect of clay consolidation on parameters that govern the advective-dispersive transport of an inorganic solute. Batch, diffusion, dispersion, and solute transport tests were conducted using kaolinite clay and dilute solutions of potassium bromide (KBr). Batch tests produced the highest levels of K+ sorption and indicated that equilibrium sorption was achieved in approximately 10–30 min. The increase in sorption observed in the batch tests, as compared to the dispersion or solute transport tests, reflects the significantly lower solids-to-solution ratio and more efficient mixing process. By comparison, kaolinite consolidation had little effect on sorption due to the relatively small change in porosity. Values of hydrodynamic dispersion coefficient (Dh), effective diffusion coefficient (D?), and apparent tortuosity factor decreased with decreasing porosity. Values of D? obtained for Br? were generally larger than for K+, whereas Dh values for Br? were significantly smaller than for K+. Values of longitudinal dispersivity (α) were larger for K+ than Br? and showed no clear trend with decreasing void ratio. In general, the experimental results suggest that changes in D? and Dh should be taken into account during clay consolidation whereas the sorption isotherm and α may be considered as unchanged during the consolidation process.     

Internal energy flow analysis within a single effect sorption heat pump

The knowledge of the characteristics of unused, excess and untapped exergy allows a thorough analysis of internal energy flows distribution within a sorption heat pump. It can be applied to any system based on gas–liquid absorption, adsorption or solid–gas reaction as well as to any process based on the internal recycling of the energy flux. It can also be applied for the case of a simple effect ideal machine, in particular in the definition of processes where the COP is larger than 2: the levels at which the initial exergy is downgraded on the one hand, as well as, the upgraded excess exergy produced on the other allows the designer to make a judicious choice of a system.     

~(85)Sr、~(134)Cs和~(60)Co在黄土中吸附和迁移的研究

本文通过静态实验和动态实验 ,研究了85Sr、13 4Cs和60 Co在黄土中的吸附和迁移行为以及核素浓度、p H和温度对分配系数的影响。静态实验结果表明 ,16个样品测定的85Sr、13 4Cs和60 Co的分配系数的均值分别为 82、7.4× 10 3 和 5.4× 10 3 m L/g;p H值的变化对三种核素的分配系数有较大影响。动态实验结果表明 ,三种核素的绝大部分滞留在土柱中 ,只有少部分从土柱中流出来 ;三种核素在土柱中的迁移速度从快到慢的顺序为85Sr>13 4Cs≈60 Co     

Method for simultaneous determination of sorption isotherms and diffusivity of cement-based materials

A method for simultaneous determination of the diffusion and sorption properties of cement-based materials is presented. It is a gravimetric method where one small specimen is exposed to stepwise changes in relative humidity while its mass is being measured. As sorption in cement-based materials is slow, the change in relative humidity to the next level is made before final equilibrium has been reached on the previous level. Approximate final (equilibrium) levels are found by extrapolation using an exponential equation, and a factor is applied to correct for the fact that the sorption step does not start at equilibrium conditions. A correction for external mass transfer resistance is also included. The method can be used in desorption as well as absorption mode. Measurements of two materials are presented and compared with the results obtained using conventional methods.