The analysis of water-chemical mode of heat and power objects
Students Name: Kushnir Orest Yaroslavovych
Qualification Level: magister
Speciality: Heat and Power Engineering
Institute: Institute of Power Engineering and Control Systems
Mode of Study: full
Academic Year: 2020-2021 н.р.
Language of Defence: ukrainian
Abstract: Kushnir O.Ya., Galyanchuk I.R. (supervisor). The analysis of water-chemical mode of heat and power objects. Master’s thesis. - Lviv Polytechnic National University, Lviv, 2020. The composition, structure and physical properties of deposits in boilers depend mainly on the chemical composition and temperature of the boiler water. In turn, the chemical composition of boiler water is largely determined by the feed water and means of corrective treatment. The formation of phosphorite is observed in the feed tract and economizer at relatively low pH values compared to boiler water, and the formation of hydroxylapatite occurs in an alkaline environment of boiler water. This circumstance determines the optimal conditions for the introduction of phosphate solution not in the feed, but directly in the boiler water. The organization of the water regime of the steam generator with the use of a step evaporation scheme makes it possible to significantly increase the concentration of impurities in the purge water without compromising the quality of steam. Thus, it is possible to reduce the required purge of the steam generator to an economically acceptable value, as well as to reduce the requirements for salt and silica of the feed water. Experimental and operational data indicate that steam washing devices reduce the silicon content of steam by an average of 2-3 times. Deposition of impurities in the flowing part of the turbines reduces the cross-sections and increases the resistance along its path due to the increase in steam velocities and surface roughness of the turbine elements. This leads to a decrease in the relative efficiency of the turbine and a decrease in the power produced by it. For UPC turbines with 300 MW units, the accumulation of deposits, which corresponds to an increase in pressure in the control stage by 5%, leads to a decrease in capacity to 290-295 MW at a constant steam flow rate. With twice the pressure in the control stage (up to 10%), the turbine capacity is reduced to 270 MW. The main reason for the accumulation of iron oxides in heating systems is the corrosion of downtime of connected mains, in which the wet surface of the pipes corrodes under the action of atmospheric oxygen. Estimation of the downtime corrosion rate shows that at 20 °C it is 1.5-2.0 g/(m2·h), ie downtime corrosion is more intense than the corrosion that occurs during operation, 15-20 times. The object of research is the water-chemical regime of thermal power facilities. The subject of research – the technology of water treatment and water-chemical regimes at boilers and thermal power plants. The purpose and objectives of research. The purpose of the work is to analyze the water-chemical regime of thermal power facilities. To achieve this goal it was necessary to perform the following tasks: - to investigate the mode of reduced phosphating for drum boilers; - to analyze the organization of the water regime of the steam generator using the scheme of step evaporation; - to study the influence of impurity deposits in the flowing part of the turbines on its operating characteristics; - to establish the reason of accumulation of iron oxides in heating systems; - to calculate the equipment of the technological scheme of water treatment type M - Np - A1 - H2 - D - B - A2 (the given abbreviation corresponds to the name of stages of processing and the scheme of chemical desalination of water) with preliminary liming and coagulation with a productivity of 400 m3/h with parallel inclusion of filters; - to carry out technical and economic calculation of the desalination plant. In this master’s qualification work the analysis of a water-chemical mode of thermal power objects is carried out. The equipment of the technological scheme of water treatment type M - Np - A1 - H2 - D - B - A2 (the given abbreviation corresponds to the name of stages of processing and the scheme of chemical desalination of water) with preliminary liming and coagulation with a productivity of 400 m3/h with parallel inclusion of filters is carried out. The calculation of water treatment plants and condensate treatment plants for various purposes begins with determining their performance and the choice of the scheme on the basis of data, taking into account the characteristics of the main and auxiliary power equipment and water supply source. The technical and economic calculation of the desalination plant was carried out. The desalination plant is designed to produce demineralized water using TPP as a heating coolant. To determine the payback period, it is necessary to establish the cost of all costs for the construction of the installation, operating costs that will occur, and find the savings that will provide the project. The use of automated control systems ensures reliable and economical operation of power plants with a small number of maintenance personnel. The deaerator at the TPP is a mixing heater of feed water, in which its thermal deaeration is carried out at the same time, ie the removal of dissolved oxygen. As an object of regulation, the deaerator can be represented as two independent sections: pressure and level. Keywords: water-chemical regime, heat-energy objects, water treatment, corrosion, impurity deposition.