Mass transfer in vertical cloth layers impregnated with calcium chloride for recovery of water from air

This paper presents an investigation on the absorption/regeneration mass transfer through parallel plates of cloth layers. Cloth layers impregnated with calcium chloride solution are subjected to absorption of water vapour from a flowing air stream with subsequent regeneration by a hot stream. Concentration range of desiccant from 0.2 to 0.5 is applied in this study. Experimental measurements are used to evaluate the mass transfer coefficient and Sherwood number. An attempt to fit the Sherwood number as a function of the Reynolds number, for the operating range of the Schmidt number, has been made. Scatter of the experimental values of the Sherwood number is observed and discussed in this work.     

Sequential injection titration of chloride in milk with potentiometric detection

In this work, a sequential injection system for the pseudo-titration of chloride in milk is described. Milk was directly aspirated into the system and sandwiched between two silver nitrate plugs (titrant). The aspirated zones were then propelled to the detector (Ag₂S/Ag tubular electrode), where the depletion in the titrant silver concentration (due to the formation of a AgCl precipitate) was monitored. The results obtained by the developed sequential injection titration method were not statistically different from those provided by the potentiometric reference procedure with relative standard deviations better than 3.4%. The sampling rates achieved were 17 samples per hour.     

CHEMICAL ABSORPTION OF CO2 AND SO2 INTO Ca(OH) 2 SLURRY

Chemical absorption of CO₂ and SO₂2 as single gases and as a mixture into slurries of Ca(OH) ₂ was studied in a stirred vessel with a flat gas-liquid interface. In the case of CO₂, the reaction product interrupted the subsequent gas absorption in the absence of a surface active agent. With single gases, the enhancement factor for SO₂ was much larger than that for CO₂, though both were larger than that into saturated solution. With the mixed gases, the enhancement factor for S02 was almost equal to that for the single gas absorption, but for CO₂ it was only slightly larger than that into the saturated solution     

麦饭石对溶液中碘、钙、dCTP的吸附行为的研究

一、前言随着分子生物学的发展,核酸、蛋白质等生物大分子的研究工作十分活跃。放射性同位素标记。示踪是分子生物学研究中不可缺少的方法。如用[α-~(32)P」dCTP通过缺口转移标记DNA,研究调钙蛋白时用~(45)Ca示踪,研究蛋白质、多肽、激素时用~(125)I标记。这样在     

含有结构水的多孔材料导热系数研究及预测

本文介绍了预测多孔材料导热系数的主要计算方程,通过岩棉保温材料和微孔硅酸钙保温材料导热系数的预测,指出这些方法在预测含有结构水的微孔硅酸钙保温材料导热系数时,与实测值会有较大的偏差,进而利用岩棉和微孔硅酸钙保温材料热重(TG)和差热(DTA)曲线,研究了材料结构水对其导热系数的影响,提出了预测含有结构水的多孔材料导热系数的修正方法,其结果与实测值相当吻合。     

A direct method for determining chloride diffusion coefficient by using migration test

Calculation of the effective diffusion coefficient is proposed using an analytical model based on Nernst-Planck equation, on electroneutrality and on measurements of current intensity. To validate this approach, migration tests were carried out on different w/c mortar samples. In steady state, the resulting effective diffusion coefficients are larger than those usually obtained with models based on Nernst-Planck equation without electroneutrality. An explanation of these differences and the importance of electroneutrality are discussed in the present work.     

Significance and influence of the ambient temperature as a rate factor of steel reinforcement corrosion

The rate of corrosion of reinforcement being an electrochemical process, undoubtedly is dependent even on the level of the ambient temperature. Therefore, the ambient temperature seems to be an important factor of the corrosion rate and the durability of the reinforced concrete structures in aggressive environment. The present data on the influence and significance of the ambient temperature in the process of corrosion of reinforcement of the reinforced structures are surprisingly limited and poor. It seems that it is supposed to be a simple increase of corrosion rate when the ambient temperature is increased. The lack of information was a motivation for the present study. It was aimed at the experimental research of the influence of the increase of the ambient temperature on the rate of chloride induced corrosion of steel reinforcement. The results obtained show that the influence of the studied factor is more complex showing an acceleration effect till a temperature of 40°C diversified by the inhibition effects with further increase of the ambient temperature.     

Corrosion by chlorides in reinforced concrete: Determination of chloride concentration threshold by impedance spectroscopy

Chloride penetration in reinforced concrete induces depassivation of the steel rebars and initiation of the corrosion process leading to degradation of the structure. The coupling of “low-frequency” impedance response with SEM observations and multielementary analyses emphasized that the strong decrease of the capacitive part is related to the corrosion initiation. This experimentally determined incubation period is used in an electrodiffusion model based on Fick's second law to quantify the chloride concentration threshold responsible for corrosion initiation on the reinforcing steel surface. This work thus allowed quantifying the incubation period and the critical chloride concentration, referred to in Tuutti's diagram [K. Tuutti, Corrosion of steel in concrete, CBI Research Report no. 4.82, Swedish Cement and Concrete Research Institute, Stockholm, Sweden, 1982].     

Selecting an adequate procedure for the electrochemical chloride removal

This paper concerns the proper selection of the electrochemical chloride removal (ECR) current and the ECR duration. Four constant ECR current densities, 100, 200, 400 and 800 μA/cm², were applied to concretes for 1 to 6 weeks. The remaining chloride contents nearby the reinforcement were measured to understand how fast the ECR process can remove chloride ions out of concrete. The open circuit potential and corrosion rate measurements were performed to examine the corrosion status after ECR. In addition, the pH value nearby the reinforcement and the apparent electrical resistivity of concretes after ECR were measured. The results showed that the remaining chloride ions decreased, the open circuit potential became nobler, the corrosion rate decreased, the pH value increased and the apparent electrical resistivity increased as the ECR parameter, defined as the product of the ECR current density and the ECR duration, increased. The ECR parameter can provide a direction in designing the ECR process.     

拜尔法——铝酸钙水泥联合新工艺研究

提出了拜尔法-铝酸钙水泥新工艺。用石灰将拜尔法种分母液中的Al2O3沉下来,经分离洗涤,得到沉铝渣,其主要物相为3CaO·Al2O3·6H2O,粒度细,比表面积大,受热脱水后变成12CaO·7Al2O3和CaO。将沉铝渣配一定的氧化铝或氢氧化铝,可以烧制Al2O3含量为70％和80％的铝酸钙水泥,降低原料成本约30％。沉铝后的种分母液(αk40-100)返回拜尔溶出,可提高循环效率95％以上。种分母液沉铝时还可以得到较高的碳碱苛化率(25％-60％)和较好的溶液净化效果(SiO2含量降低80％以上,Ns含量降低20％以上)。