Chemical and membrane desalination of natural water with high content of iron-organic compounds

Under the conditions of modernization of Russian thermal power plants (TPP), water treatment plants based on imported membrane technologies are often put into operation without consideration of the quality of the source (natural) water and variable-performance operating modes. At the same time long-running water treatment plants and their capabilities are not considered. In this regard, the cost of additional water is three or more times higher, and the average output is respectively lower than at traditional water treatment plants. Often, one doesn’t take the advantages of reverse osmosis installations based on the rejection of the use of aggressive reagents such as sulfuric acid, etc. The aim of the study is to increase the efficiency of desalinated water production. It is especially important to conduct studies of natural waters with high content of iron-organic compounds characteristic of the regions of the center and north of Russia. The authors have carried out laboratory studies of various, primarily new filter materials, regents, and devices, both at the stages of pre-purification of water i.e., clarification, and at the stages of demineralization of clarified water. Water treatment plants of Ivanovo combined-cycle plant (CCP) and Cherepovets state district power station (GRES) are considered as the subject of the research. It is found out that if one applies ion-exchange and membrane water treatment technologies to treat water with high content of iron-organic compounds, high-quality desalinated water can be obtained. The properties of water are the following: specific electrical conductivity of no more than 0,2 mcm/cm and permanganate oxidizability of no more than 1 MgO/l. Results of studies at the Ivanovo CCP and Cherepovets GRES have shown practicability to coagulate water with aluminum sulfate using an anionactive flocculant, for example, during the flood period. Application of coagulation and ultrafiltration units before reverse osmosis installation ensures removing organic impurities from the water. Based on the obtained research results, recommendations are given for the implementation of the results at Ivanovo water treatment plants.

INDUCTIVE PARAMETRIC EDDY-CURRENT TRANSDUCER (IPEP) FOR MEASURING ELECTRICAL AND TEMPERATURE PARAMETERS OF WASTEWATER FROM BREWING PRODUCTION

The possibility of using the theory of operation of a differential inductive parametric eddy-current transducer (IPET) for measuring the electrical and temperature parameters of a sample of acidic and alkaline wastewater is investigated. The need for the development of new informative methods for measuring the physicochemical parameters of wastewater is proved, in the realization of which a promising method of purification is selected. On the basis of a differential scheme for switching on two parametric converters: with exemplary purified water and a converter in which a test tube with a sample of waste water from a brewing production is placed, a differential informative method for measuring the electrical and temperature parameters of the liquid under study is proposed, which is based on the analysis of the components of the difference signal of phase shift angles measured electrical components of the switching circuit signals. The basic relationships that describe the operation of the IPET with the sample of the controlled liquid are given. The scheme of switching on differential IPET with a liquid sample, which is placed in a glass test tube, is considered; the differential scheme provides for heating the sample during measurements to simulate the production conditions of brewing production. Universal transformation functions are given that relate the components of the IPET signals with the specific electrical conductivity χt.s. and the temperature t of the wastewater sample from brewing production, that is, the dependence of the phase difference signal Δj on the generalized parameter A and the dependence of the absolute increment in the specific electrical conductivity Δχ on the temperature t of the wastewater sample, in the investigated temperature range.

Kinetic instability of a chitosan – aspartic acid – water system as a method for obtaining nano- and microparticles

The specific electrical conductivity and dielectric constant of aqueous solutions of ionic aminopolysaccharide chitosan in L-aspartic acid were investigated. An increase of the mobility of charge carriers in these solutions was found in comparison with solutions of an individual acid. The evaluation of the kinetic stability revealed that the viscosity, electrical conductivity and dielectric constant of the chitosan – L-aspartic acid – water system decrease, while the pH value increases. It was shown that the time variation of physicochemical and electrochemical parameters is due to the effects of counterionic association with the transition of macromolecules to the ionomeric state and is accompanied by phase segregation of the polymer phase in the form of nano- and microparticles. The conducted studies carried out have shown the fundamental possibility of controlling the metastable state of this system in order to obtain nano- and microparticles.

Electric arc in plasma flow of gas discharge with a liquid electrolyte

The properties of an electric arc ignited in a gas discharge plasma flow with a liquid electrolyte cathode are experimentally investigated. Aqueous solutions of sodium chloride with a specific electrical conductivity of 10-15 mS/cm were used as a liquid electrolyte. The distance between the anode and the liquid electrolyte cathode was set in the range of 5-60 mm, and the distance between the anode and the metal cathode was varied in the range of 2-30 mm. The current of gas discharge with a liquid electrolyte cathode was set in the range of 5-10 A, and the arc current varied in the range of 1-10 A. The conditions under which the arc burns with the formation of a contracted channel are revealed.

Combined electric discharge “arc + discharge with liquid electrolyte cathode”

A combination of an electric arc and discharge with a liquid electrolyte cathode in a single discharge gap has been created. The plasma column of discharge with liquid electrolyte cathode formed a “hollow cylinder”. The electric arc was burned in a vapor-gas environment inside the “hollow cylinder”. The gas discharge current with liquid electrolyte cathode was set in the range of 5-10 A, and the arc current varied in the range of 1-10 A. Aqueous solutions of sodium chloride with a specific electrical conductivity of 10-15 mS/cm were used as a liquid electrolyte. Spectral studies have been carried out in the visible range of radiation. In the experiments, copper and duralumin metal cathodes were used.

Protective and Thermophysical Characteristics of Plasma-Electrolytic Coatings on the Ultra-Light Magnesium Alloy

Magnesium alloys are now widely used for various purposes due to their unique properties despite the significant disadvantage associated with low corrosion resistance. The plasma-electrolytic oxidation (PEO), which allows the formation of ceramic coatings on the surface of magnesium alloys, is the most advanced and effective method for their protection. But firstly, PEO process of magnesium alloys has some difficulties, and secondly, PEO coatings affect the thermophysical characteristics of the modified materials, in particular they reduce thermal diffusivity. The presented work is devoted to the development of the technological parameters for formation of protective coating on the ultra-light alloy Mg-8Li-1Al-0.6Ce-0.3Y by the PEO method. The results analyses of electrolytes acidity and specific electrical conductivity before and after PEO process and also investigation data of the coatings structure and surface morphology are presented. An integral assessment of the ability of thermal diffusivity and corrosion resistance of the modified alloy was made. Studying of protective and thermophysical characteristics of the obtained coating showed that it provides a sufficiently high corrosion protection, despite the relatively small thickness, and the presence of pores and slightly (not more than 5%) reduces the thermal diffusivity of the magnesium ultra-light alloy.

Modeling of quality indicators for water demineralization process at power reactors

Regression models of demineralizing filters for a nuclear power plant will increase the efficiency of the desalination process for turbine condensate. To identify the control object, experimental and statistical research methods were applied. To detect the presence and study the extent of relations between the process factors and output variables, the STATISTICA (StatSoft) analytical system was used. The impact of factors on the studied traits was assessed using a nonlinear estimation module. Upon the analysis of the desalination plant operation, the following initial parameters were identified. These parameters influence the control decisions in managing the object, can be predicted over time and are not random variables such as the values of specific conductivity and hydrogen index. For specific electrical conductivity: Xh is the specific electrical conductivity of the condensate after the desalination plant; Na is the concentration of sodium ions in the condensate behind the condensate electric pump of the first stage; CN2H4 is the concentration of hydrazine in the feedwater of the steam generator; CFe is the concentration of iron ions in the condensate on the condensate electric pump of the first stage; T is the temperature of the condensate sample on the condensate electric pump of the first stage; CCl is the concentration of chlorine ions in the purge water of the salt compartment of the steam generator; and CSO4 is the concentration of sulfate ions in the purge water of the salt compartment of the steam generator. For the hydrogen index: pH is the hydrogen index of the condensate after the desalination plant; CN2H4 is the concentration of hydrazine in the feedwater of the steam generator; T is the temperature of the condensate sample on the condensate electric pump of the first stage; and CFe is the concentration of iron ions in the condensate behind the condensate electric pump of the first stage. To detect the presence and study the extent of relations between the selected factors of relevant process and output variables, a correlation analysis was conducted and input factors were subsequently ranked. The correlation analysis allowed ranking all the variables and their possible interaction effects in a descending degree of impact on the outputs. In accordance with the selected system outputs, based on the ranking of input variables, regression analysis was performed and corresponding mathematical dependences were obtained with alternate inclusion of factors in a decreasing degree of their influence on the output variable to establish functional dependencies between the experimental data on desalination plant operation. The regression dependence for the experimental data of specific conductivity on the selected state parameters was obtained. The coefficient of determination is equal to 0.7245. The regression dependence describing the change of the hydrogen index has also been obtained. The coefficient of determination is equal to 0.7231. The proposed models explain 72% of the variation in the dependent variable. The correlation ratio is 0.82, which determines the close relationship between the values. Regression models adequately describe the operational data of the nuclear power plant and can be used as part of the control system of the filter unit.

Effect of water activated by non-equilibrium gas-discharge plasma on the germination and early growth of cucumbers

The article presents the results of plasma-chemical treatment of water and studies of its effect on the germination of cucumber seeds, as well as on the dynamics of the initial growth of plants. Tap water was treated with a pulsed underwater discharge formed in vapor-gas bubbles near the surface of a graphite electrode immersed in water. The discharge burned at peak voltage values of 800 V and a discharge current of 200 mA. Oscillograms of the current and voltage on the electrodes were obtained, the values of the specific electrical conductivity of water, the pH value, the concentrations of nitrite and nitrate ions, and also hydrogen peroxide in the treated water were measured. It is shown that the application of the plasma treated water ncreases the seed germination, accelerates the development of the root system, the growth of stem and leaves at the early stages of plant development

Influence of Sulphate Attack on Properties of Modified Cement Composites

Monitoring the condition of building structures based on composite materials in aggressive environments shows that the deterioration of basic properties occurs under the influence of various factors such as temperature and humidity changes,in addition to changes in the chemical composition of air environment. In addition, the composite materials during the operation must retain not only the mechanical properties laid down at the design stage, but also the electro-physical characteristics, regardless of the type of destructive effects. In the current study, the quantitative assessment of the result of the interaction of an aggressive sulphate-containing medium with composites modified with conductive and dielectric additives was carried out. The effect of sulphateattack on the specific electrical conductivity of cement composites was studied. The nature of the interaction was evaluated by changing the properties of the samples of the developed compositions under the influence of a single-normal solution of sodium sulphate. The analysis was carried out by means of potentiometric titration using the exchange interaction method by fixing the degree of absorption of sulphate ions and determining the concentration of calcium ions in the solution. The measurement of the solution potential allowed determination of the quantitative indicators of the rate of calcium hydroxide leaching from the sample structure,which is necessary to assess the intensity of the destruction process and determine the nature of the change in strength properties.Measurements of the electrical resistivity of samples under the constant influence of sulphate aggression were taken during 28 days of observation. A method for quantifying the effect of a sulphate medium on a cement matrix was proposed that enables the material durability to be predicted. The features of changes in the morphology of structural components after exposure to aggressive solution were determined by physical and chemical methods.