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P.S. Chowdhury*

Presently in NTPC, most soot blowing schemes are based on a fixed time schedule. In many instances, certain boiler stages are blown unnecessarily, resulting in heat rate penalty. Excessive soot blowing also results in erosion of the tube surfaces, which leads to premature tube failure and subsequent forced outages. Proper soot blowing schemes are critical in achieving target steam exit temperatures. Soot blowing affects Furnace Exit Gas Temperature, which in turn affects boiler efficiency and heat rate. It can also affect the flue gas pressure drop, velocity through the individual boiler stages and generation.

Blowing soot from boiler stages in a particular order is important since soot removed from one stage can deposit on a following stage and thus reduce its heat transfer. Therefore, an expert system to indicate individual section cleanliness is invaluable to determine correct soot blowing scheme. Practical soot blowing optimization improves boiler performance, reduces NOx emissions and minimizes disturbances caused by soot blower activation.

In this project, direct method of measuring heat fluxes in different zones of the furnace is studied. Such heat flux meters are installed in Raichur Thermal Power Station, Karnataka and their logic is analyzed. An attempt is made to develop an indirect boiler soot-blowing model based on the real time data collected from Dadri, 210 MW unit of NTPC. It then calculates the heat absorbed and the degree of individual stage fouling in the form of cleanliness factor, which is the ratio of the actual and ideal stage heat transfer coefficient. Optimization of soot blowers in the furnace water wall being most important, available data is used in developing a Fuzzy Rule-Based (knowledge base) Expert System to estimate the Cleanliness Factor of the furnace followed by firing of a group of blowers where soot blowing is actually needed.

Keywords: Cleanliness Factor; Furnace Exit Gas Temperature; heat flux; Fuzzy Logic; MATLAB tool box; Expert System

* Mr. P.S. Chowdhury is presently working as DCDE (P&S - Engg.), in Engineering Office Complex of NTPC at Noida. His communication address is - Engineering Office Complex, NTPC, Sector-24, Noida (U.P.) - 201301.

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