Том 66, № 3 (2019)

Ash and slag waste (ASW) from coal-fired thermal power plants (TPPs), the amounts of which make several tens or even hundreds of millions of tons per annum, require allocation of large land areas for storing them. This waste is a source of pollution emitted into the atmosphere and it poisons the aqueous medium and soil. Ash and slag waste consists primarily of powderlike material containing a large quantity of unburned carbon (5–25%), magnetic materials (5–20%), and alumino-silicate components. All these components are a valuable raw material for industry, especially silicon and aluminum oxides, which can be used in the production of construction materials. For this purpose, ash must be preliminarily subjected to beneficiation using physical and physicochemical methods. The article presents an analysis of dry and wet ash beneficiation methods with a view to increase the volumes of using ASW produced from domestic power plants. For achieving higher strength of concretes, mechanical activation is carried out, which relates to dry ASW beneficiation methods. To obtain an alumino-silicate product containing 1.5–4.5% of carbon, such dry processing method as electrostatic separation is used. By subjecting dry ash to combined magnetic and electrostatic separation methods, it is possible to obtain an ash and a conducting product with a high concentration of carbon. For Russia, wet ASW beneficiation methods are of the greatest importance, because wet ash and slag removal is used at the majority of TPPs. Hydraulic classification of waste for obtaining products containing particles of different sizes is one of the wet beneficiation process stages. By using the froth flotation method, it is possible to obtain a concentrate containing 65–70% of carbon, a material that can serve as boiler fuel. The froth flotation is regarded as a necessary method for integrated utilization of ASW. Wet magnetic and electrostatic separation are the basic methods for producing magnetic concentrate containing 62–65% of iron. The article presents methods for separating hollow microspheres from AWS, which are a valuable product for aggregates used in the civil construction industry. The article also considers integrated ash beneficiation methods for obtaining four basic products (the figures in parentheses indicate the content of the relevant element): hollow microspheres, carbon product (64.5% of carbon), magnetic product (62% of iron), and alumino-silicate product (no more than 3% of carbon).

In the last 30 years, the phosphate ester fire resistant fluid, OMTI, has been used in the electrohydraulic control systems at Ramin power plant. Difficulties in obtaining supplies of the fluid led to efforts to extend its service life of the fluid by on-site conditioning and, eventually, to searching for a replacement. This paper surveys the operating experience obtained during the past ten years with the different forms of treatment and the replacement of OMTI by an alternative phosphate ester fluid. Different methods for conditioning of waste oil has been used from alkaline washing to ion exchange treatment. In alkaline washing process, an aqueous potassium hydroxide (KOH) solution was used to neutralise the acidity of the fluid. Any potassium soaps that are formed partition into the aqueous phase and can then be moved. Since it was done on a small-scale batch process, a static separation process was used. But in ion exchange treatment adsorption of acidic material of waste oil on ion exchange resins was used for reclamation of the oil. In view of concerns expressed over the conditioning of the used fluid and trade restrictions on purchasing the new fluid, the availability of a phosphate ester fire–resistant fluid from other sources was investigated and a different fluid, Turbex F46, was identified as potentially suitable.

An analysis of the results of investigation into the composition of the primary coolant of power units of nuclear-powered ice breakers Soviet Union and Arktika and the Sevmorput’ light carrier has revealed that an increase in the reactor power generation above 14 TW h leads to a sharp increase in the ammonia concentration in the coolant. An assumption was made that this effect was related with the radiation-chemical synthesis of ammonia from the nitrogen dissolved in the coolant and hydrogen resulting from enhancement of corrosion of the core structural members and fuel rod claddings made of zirconium alloys. To test the proposed hypothesis on the basis of the verified MORAVA H2 software package, a procedure was developed for calculating changes in the composition of the primary coolant in water-cooled water-moderated reactors (VVER) on exposure to reactor radiation with simultaneous metering of hydrogen at a controlled rate into the primary circuit (to simulate formation of corrosive hydrogen) during irradiation. This procedure was used to perform a computational experiment to find the qualitative regularities of the effect of “corrosive” hydrogen on the characteristics of water chemistry. The dependence of the calculated ratio of molar concentrations [NH₃]/[H₂] on the irradiation time has been demonstrated to linearly correlate with the measured dependencies of this ratio on the power output of similar reactor units on various nuclear-powered ships. This correlation allows for the statement on a reasonable basis that the [NH₃]/[H₂] ratio in the primary coolant of transport nuclear units is a fair indicator of the fact of general corrosion of zirconium alloys in the core having a structural member made of alloy E110.

The article discusses a method for early detection and prediction of abnormality in operation of power-unit process equipment taking as an example the PTN 1100-350-17-4 turbine driven feedwater pump of a 300 MW power unit. The importance of the problem of predicting possible process equipment malfunctions at an early state of their occurrence is determined, and the specific features of solving it in the power industry are explained. The range of process equipment defects that can be efficiently detected using the predictive analytics methods is outlined. The fundamental assertion stating that the scope of analog and discrete measurements available in the process control system’s set of computerized automation tools is sufficient for applying the predictive analytics methods is emphasized. Modern predictive analytics methods are briefly reviewed, and the specific features of model training algorithms are mentioned. Separate attention is paid to the problems of preparing initial data for training the model. The mathematical problem of modeling an abnormality indicator taking the values from 0 (normal operation) to 1 (abnormal operation) is formulated. In turn, this problem is formulated as the binary classification problem of attribute vectors characterizing the equipment state at the given moment of time. An original approach is suggested, which combines the multivariate state estimation technique (MSET), in which the degree of abnormality in a technical state is determined from the extent to which the Hotelling criterion exceeds a threshold level (which is automatically calculated in the algorithm), and machine learning methods, the use of which makes it possible to overcome a number of difficulties inherent in the MSET. For solving the problem of determining the composition of the most informative attributes from the values of which early development of an emergency can be detected, it is proposed to use an ensemble of regression models. A method for selecting the modeled variable and the set of regressors is substantiated. An abnormality indicator calculation method based on composing an ensemble of linear regression models is proposed, and the advantage of using an ensemble over a single classifier is shown. A method for producing an alarm in response to detected abnormality in the operation of power unit process equipment is suggested. It is shown that it became possible by using the proposed model to detect the onset of the emergency development process, whereas individual indicators failed to reveal pump operation singularities in the preemergency interval of time.

The article deals with the assessment of the performance and competitiveness of a nuclear power plant (NPP) combined with a hydrogen power plant compared with a gas-turbine power plant (GTPP) and a pumped-storage hydroelectric power station (PSPS) to satisfy the peak electrical demand in a power system in terms of the peak electric power prime costs. The structure of installed capacities of various interconnected power systems is shown considering the increase in the capacity levels in the immediate future. The necessity of curtailing the load of the power-generating units during the periods of the nighttime off-peak demand is justified. For this purpose, the efficiency of curtailing the load of the power-generating units of various types is analyzed under variable electric loads. As an example, the power-generating units of an NPP equipped with a VVER-1200 reactor, a 300-MW condensation electric power plant, and a PGU-450 combined-cycle gas turbine are considered. The increase in the electric power prime cost serves as the efficiency criterion. To provide the NPP with the base load, variants of combining the NPP with a hydrogen power plant with steam–hydrogen superheating of the live steam upstream from the high-pressure cylinder of the primary turbine and the high-pressure cylinder of the auxiliary steam turbine accompanied by ejection of the heating reheat steam are presented. The forecasted prices of fuel gas and nuclear fuels, as well as of the nighttime electric power for 2020 and in the long term until 2035, are taken into account. It is shown that the employment of GTPPs results in an additional increase in the expenditures caused by curtailing the load of the NPP at nighttime and appears to be inefficient in some cases. The expenditures on the substituted power are accounted for in comparison with the pumped-storage power station in the hydrogen power plant variant. It is shown that the pumped-storage power stations can compete in the foreseeable future with the hydrogen power plants in terms of peak electric power prime costs at minimum specific capital investments of approximately 660 $/kW. In the long term, due to a considerable increase in the nighttime electricity cost, the pumped-storage power stations will not be able to compete with the hydrogen power plants.

In recent years use of Zr-Nb alloys has increased in nuclear and chemical industry due to its corrosion resistance and enhanced strength compared to tin based ones. Welding of zirconium alloys is one of the most critical manufacturing processes for nuclear assembly production. To select suitable welding parameters to achieve quality weld, understanding of temperature and velocity fields during process in fusion zone and heat affected zone are essential. In the present study the Nd:YAG pulsed laser welding of zirconium alloy E110 was simulated using three-dimensional heat and fluid flow model. The convection mode of heat transfer and Marangoni stresses in fusion zone are two important mechanisms in controlling the heat transfer weld bead size. The calculated heating and cooling rates are of typical in laser welding and useful in microstructure study of fusion and heat affected zones. Experiments were carried with varying peak power, pulse frequency and duration using Nd:YAG pulsed laser on 0.5 mm thick sheets of E110 to form butt joints. The comparison of the results shows that the weld geometry is well matched with the numerical model.