(0000) A PILOT-SCALE CONDENSING WASTE HEAT EXCHANGER IN A POWER UNIT

Paweł Rączka, Kazimierz Wójs

Abstract


This paper presents a calculation algorithm, design assumptions and results of studies concerning a flue gas/water heat exchanger with the condensation of water vapour contained in flue gas from the combustion of lignite. The algorithm was used for design calculations of a pilot-scale heat exchanger with a capacity of 380/312 kW. A cross-counter flow heat exchanger with a capacity of 312 kW and coils made of PFA was designed and installed. Waste heat is recovered from flue gas produced by a pulverized lignite-fired steam boiler operated in a power unit with a capacity of 370 MWe. The heat exchanger was divided into a non-condensing part (sensible heat recovery) and a part with the condensation of water vapour contained in flue gas (recovery of sensible and latent heat). The point of the division is the temperature of flue gas in the stream core (higher than near the pipe wall), at which the condensation of water vapour on the pipe surface occurs. The heat transfer in the non-condensing part was calculated using the same formulas as for the water heater (economizer) in a pulverized-fuel boiler, while the calculations of the heat and mass transfer in the condensing part were performed using the VDI algorithm. Results of the thermal calculations and the geometry of the heat exchanger together with the place of installation of the entire test rig were presented. The results of the calculation were then compared with the test results. A good correlation of the tests results with the assumptions and the results of the design calculations was achieved.

Keywords


condensing heat exchanger, waste heat, heat exchanger calculations, chimney heat loss

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References


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