STUDY OF EROSION AND ACCRETION FROM WATER AND STEAM OVER PIPE WALLS OF CONDENSER IN A THERMAL POWER PLANT

摘要

It is extremely important and required by thermal power plant to condense the exhaust steam from steam turbine outlets to obtain maximum efficiency on varying loads. Surface type condensers are often used to meet these demands. By condensing the exhaust steam at a pressure below atmospheric pressure, the pressure drop between inlet and outlet of turbine is increased which increases the amount of heat available for conversion to mechanical energy by the turbine. Increasing the heat transfer rate of condenser is an effective method to increase the overall efficiency of a thermal power plant. With condenser playing a vital role in overall plant efficiency, it is important to analyze the areas of fouling/erosion, which reduce the condensation rate. The condenser used in a company has been in operation for many years, so to study the effect of erosion on the condenser pipelines, a computational simulation of a section of the condenser in 210 MW thermal power plant with erosion modeling has been done using Fluent code. To help understand the steam cooling in the condenser, current study analyses a 3D section of the condenser used in a 210 MW thermal power plant using a commercial ANSYS/FLUENT code. A boundary layer coupled mesh is used to simulate the interaction of steam and water with the condenser tubes. Models to simulate the flow of water inside the tubes and low-pressure steam over the tubes are incorporated to show the heat transfer between the steam and water domain through the pipe walls along with incorporation of accretion and erosion model, specially the erosion. Analysis of erosion accretion due to Calcium salts are taken in consideration to interpret the location, where scaling happens and how the yearlong scaling affects the heat transfer ability of the heat transfer tubes. There is one build-in erosion and accretion model in FLUENT, which accounts of erosion/accretion on a surface from solid particle. Although the water is liquid, but the article that is responsible for erosion and accretion is solid, e.g. Calcium salt. The result shows that the heat transfer rate is not constant along the tube over a period due to erosion and untreated hard water used for cooling purpose. The Erosion model predicts the most prominent erosion/accretion sites inside the tubes and stresses on the importance of treatment of the recirculating hard water. A liquid particle erosion can also be modeled in future if needed.