CONCENTRATION OF SOLUBLE SALTS IN COOLING WATER OF POWER PLANTS WITH BLOW DOWN RECIRCULATION

The method for calculating the dynamics of concentration of soluble salts (tracers) using the assumption of their homogeneous distribution in the water volume of the circulated cooling system (CCS) under the conditions of recirculation of part of the purge water was proposed. The assumption of homogeneity of salt distribution is substantiated by the fact that the period of mixing of cold water (CW) in CCS is equal to several hours, and the period of setting the concentration limits is calculated in tens of days. In this approximation the law of change of concentration of tracers in time from the moment of their supply in CCS in modes without and with recirculation of a part of purge water and without any processing is received. It is shown that without recirculating treatment, recirculation of purge water increases the maximum salt concentration and the time to reach it. Attention is drawn to the fact that the flow rate consists of two parts: controlled and uncontrolled. When calculating the allowable amount of purge recirculation, it is necessary to use the value of the total purge flow. It is important to understand that the relative change in total purge is always less than the controlled one. To obtain the cost of full purge, it is necessary to calculate its uncontrolled part. The procedure for calculating the uncontrolled purge is given in the paper. Since there are restrictions for of maximum allowable concentration (MAC) on the concentrations of tracers in the CCS, the expressions obtained in this work are consistent with the requirements of the MAC and allow for a given degree of concentration of salts φ, to calculate the limit of recirculation flow. It is shown that the recirculation regime can be applied without additional measures for CCS with a low initial degree of salt concentration and low concentration in the feed water. The proposed algorithm is used to predict the results of recirculation in the case of a specific CСS for thermal power plants with an electrical capacity of 1200 MW and the ratio CMAC/C0 = 5. It is shown that in this case recirculation has significant economic and environmental effects. However, at high, concentrations of tracers C0, compared to MAC, feed water recirculation is meaningless. The calculation algorithm applies to tracers, i.e. salts that do not give deposits, but only limited by the MAC requirements and the risk of corrosion or environmental considerations. Therefore, the above technique cannot be directly used for sparingly soluble salts, such as calcium carbonate. In this case, it requires significant correction. Note the convenient use in calculations of the earlier introduced by us concept of regime (dynamic) factor φ, especially when comparing the real consumption of the main flows of ССS to calculated and in determining the evaporative capacity of cooling towers, or assessing the degree of salt concentration.

pH-metric method determining the solubility and solubility products of slightly soluble salts of arbitrary composition

The developed method of determining KS from pH metric data has a number of advantages compared to those used traditionally. First, in place of the residual concentrations of the salt components, only the pH value of the saturated solution is used in the derived expressions. Thus, the number of independent variables, which need to be measured experimentally, is reduced. Furthermore, the potentiometric method, used to determine the pH, is sufficiently accurate, simple and universal and does not necessitate the use of ion-selective electrodes. At the same time, the residual concentrations are usually measured by chemical methods, which are inferior in most cases, for several reasons, compared to the potentiometric method. Second, the KS value calculated by the developed method has a thermodynamic character. The organization of the experiment must be appropriate to the applied equations. Therefore, it is necessary to draw attention to the need for high accuracy in the process of preparing the initial solutions, because the initial concentrations of the precipitate components are included in the calculation formulas. The developed method for determining Ks can be applied for systems of any degree of complexity, which contain additional complexing agents.

Evaluating the Protective Effects of Calcium Carbonate Coating on Sandstone Cultural Heritage

The purpose of this work was to use different surfactants to deposit different crystalline calcium carbonate films on the surface of sandstone through a simple double displacement reaction. This was done to test the protective effects of calcium carbonate coatings based on water absorption, moisture permeability and weather resistance. Experimental results showed that the air permeability of the stone treated with vaterite calcium carbonate was reduced, but that this did not affect water vapor’s access into and out of the stone. Compared with untreated stone, the water absorption rate was reduced 0.5 times, and the weather resistance increased by 4 times due to small crystal grains, high solubility, and deep penetration hindering the erosion of water and soluble salts. These findings are expected to provide useful suggestions for the protection of stone cultural heritage.

Ecological state of alluvial soils of floodplain landscapes under conditions of local pollution by hydrocarbons (Western Siberia)

The paper presents an analysis of field and experimental studies of the main physicochemical parameters of oil-contaminated soils of floodplain ecosystems of the middle taiga subzone of Western Siberia. The features and main regularities of their change in different pollution zones (epicenter - impact zone) are revealed. The state of the physicochemical parameters of technogenically contaminated soils is compared with background analogs. The most important groups of chemical compounds and elements that pose an environmental hazard are considered - oil and oil products, technogenic readily soluble salts (including their toxic compounds), the ways of their migration, transformation and accumulation in contaminated soils. General recommendations are given on the use of the discovered regularities in the technical maps of reclamation measures and the system for monitoring contaminated soils.

New methods of cleaning soil from heavy metals

The purpose of the work was to study new methods of cleaning soil from heavy metals. In this work, it was proposed to extract heavy metals Cd, Zn, Fe, Cu, Mn, Pb from soils using the method of biological purification. For this, we recommended to carry out preliminary treatment of soils with complexones and to carry out additional introduction of biophilic elements into complex compounds. The possibility of using electromechanical treatment for removing heavy metals from soils after a preliminary increase in the mobility of ions by acidification and the use of complexation reactions is shown. The experiments were carried out on the plants of sowing oat Avena sativa L. variety Yakov when grown in laboratory conditions on sod-podzolic soil with the introduction of soluble salts of heavy metals into the soil. It was noted that the largest amount of heavy metals is concentrated in the root system of plants. When growing oats in the field, the concentration of metals in the grain was assessed: Mn - 30-35 ppm, Fe - 55-65 ppm, Cu - 4-5 ppm, Zn - 30-35 ppm, Cd, Pb < 3 ppm.

Optical Properties and Radiation Stability of Magnesium Silicate

A microwave (MW) method of hydrothermal synthesis of magnesium silicate is developed. At low temperature (240 0C), nuclei of crystalline phase of магний silicate are obtained. Some optical characteristics of the synthesized product are determined. Based on, X-ray and thermographic studies are revealed that the synthesis of magnesium silicate from water-soluble salts of initial components in microwave ovens promotes the formation of magnesium at lower temperatures. MW synthesis of magnesium silicate ensures obtaining of nanosized powder after heat treatment at 850 0C.

Archaeological and Chemical Investigation on the High Imperial Mosaic Floor Mortars of the Domus Integrated in the Museum of Archaeology D. Diogo de Sousa, Braga, Portugal

This paper intends to characterize the floor mortar layers (nucleus, rudus and statumen) of the high imperial mosaics of the domus integrated in the Museum of Archeology D. Diogo de Sousa, the oldest roman housing testimonies known in Braga, Portugal. It offers an important archaeological and historical contextualization and first chemical characterization attempt on the mortars. The study of 13 mortar samples was carried out at a chemical level through X-ray fluorescence spectroscopy (XRF). All samples presented low lime content when compared to similar studies. A high chemical similarity between nucleus mortars (opus signinum) and chemical composition differences between rudus and statumen mortars was determined, confirmed by statistical analyses. Their composition was distinctly related to the stratigraphic position of each floor mortar layer, following Vitruvius’ model, and to the external conditions and treatments (e.g., capillary rise with soluble salts and application of chemical treatments), to which they were submitted.