Research On Corrosion Mechanism Of Low Temperature Heat Exchanger And New Type Corrosion Resistance Materials For Utility Boilers

In the actual operation process, because of the design, operation, coal and other reasons, the actual exhaust gas temperature will be 10-40℃ higher than the design value in many coal-fired power plants, reducing the efficiency of the boiler. It is no delay to effectively recovery flue gas waste heat so as to improve boiler efficiency. There is a certain amount of sulfur in the coal. In the process of flue gas waste heat utilization, when the steam and sulfuric acid vapor in the flue gas flows through low temperature heating surface, they will condense in the metal wall with a low temperature. The corrosion will affect the safe operation and service life of the equipment. In order to absorb the boiler exhaust gas waste heat, it is necessary to break the limitations of the corrosion. The corrosion resistance of material in water heat exchanger has become one of the important factors which affect the deep utilization of waste heat in power station.In summary, research will be carried out on the mechanism of low temperature sulfuric acid dew point corrosion, and all kinds of domestic and foreign acid dew point calculation formulas were compared; then a series of new materials will be prepared, the corrosion behaviors of materials were evaluated by corrosion weight-loss method, electrochemical tests and simulated flue gas corrosion tests. The results show that amorphous alloy and fluorine plastic showed excellent corrosion resistance in every test compared with 20G steel, ND steel and 316 stainless steel, and the corrosion resistance of these materials as follows:fluorine plastic> amorphous alloy> 316 stainless steel> ND steel> 20G steel; finally, the new materials were tested by coupon test, spraying experiment and real flue gas corrosion test, to prove that the new materials have excellent anti fouling and corrosion resistance in power plants.In this paper, the methods and results concluded can be important theoretical basis for the optimization of corrosion-resistant materials in low-temperature boiler flue gas, and will popularizes the waste heat utilization system to a large extent.