| Used for catalytic cracking,waste heat boiler is an important energy saving equipment for oil refinery.Economizer is a heat interchanger which uses the hot exhaust gas of the boiler to heat the water.The leakage of economizer will reduce the ability of flue gas waste heat recycling,and the frequent repair will lead to the waste of manpower,greatly reduce the efficiency of waste heat boiler,and even threaten the normal operation of the plant.In this paper,leakage problems of an economizer were studied,modification on the equipments and the techniques were made,and finally significant effect was achieved.The research indicates that the economizer inlet water temperature is lower than the dew point of exhaust gas,which leads to the anhydride of exhaust gas and water vapor condensation on the outer wall of pipeline and cause the corrosion of the outer wall.This is the main reason for the leakage of the economizer.The abnormal running of the deaerator causes the concentration of oxygen exceeds normal level,which leads to corrosion and thinning of the inner wall.This plays a auxiliary role for the leakage of the economizer.Replacing the tail heating surface and adding the heat exchanger module can increase the temperature difference of the exhaust gas which pass the high temperature economizer by 9.04 ?,increase the temperature difference of the exhaust gas which pass the low temperature economizer by 29.59 ?,and decrease the temperature of the grate smoke by 87.46 ?.The use of preheater can increase the temperature of the waster with oxygen which pass the economizer by 39.62 ? and reach 144 ?.The temperature is higher than the waste heat boiler dew point corrosion temperature.Using ND steel to replace the original 20 G steel can improve the corrosion resistant properties of waste heat boiler economizer.After these modifications,the economizer ran safely for more than 1 year without leakage.The methods used in this paper provide ideas and reference value to solve similar problems. |
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