Complex cleaning system for heat exchanger

Abstract

The purpose of the present disclosure is to solve the problems of a difficult operation or occurrence of corrosion damage to equipment caused by the attachment of ammonium sulfate salt, which is generated when unreacted ammonia (NH 3 slip) and sulfur trioxide (SO 3 ) in exhaust gas are bonded with each other when a selective catalytic reduction (SCR) is used to eliminate nitrogen oxides that are contained in the exhaust gas generated during the combustion of a boiler or the like, to a heat exchanger of an air preheater (APH) or the like installed at the rear of an SCR device and blocks a passage of the exhaust gas such that the pressure inside the boiler is increased. To this end, a dry ice cleaning device is installed at the front of an exhaust gas inlet in an air preheater such that the blocking of a heat exchanger caused by ammonium sulfate salt or the like is removed by spraying dry ice pellets, and at the same time, high-temperature steam spraying device is installed at a cold end of the air preheater so as to spray the steam in the same direction as that of air supplied to a boiler, thereby removing contaminants more effectively. Furthermore, in order to effectively prevent blocking which occurs in a cold end of the air preheater, dry ice is sprayed to the front of an exhaust gas inlet of the air preheater and also, to the front of a supply air inlet of the air preheater which is an opposite direction thereof, such that a cleaning effect is increased.

1 . A method of complex cleaning for a heat exchanger comprising:
 spraying high-temperature steam to the heat exchanger at a temperature of 90° C. to 500° C. and a pressure of 10 kg/cm 2  g to 30 kg/cm 2  g;   spraying dry ice pellets to an inlet of the heat exchanger in parallel with a surface of a thermal element at a pressure of 0.5 kg/cm 2  g to 20 kg/cm 2  g and a speed of 200 m/sec to 400 m/sec, each dry ice pellet having a diameter of 0.1 mm to 3 mm; and   eliminating contaminants formed on the surface of the thermal element,   wherein,   in spraying the high-temperature steam, the high-temperature steam is sprayed to an exhaust gas inlet of the heat exchanger or to a supply air inlet of the heat exchanger opposite to the exhaust gas inlet; and   in spraying the dry ice pellets, the dry ice pellets are sprayed to the exhaust gas inlet of the heat exchanger or to the supply air inlet of the heat exchanger opposite to the exhaust gas inlet.   
     
     
         2 . The method according to  claim 1 , wherein spraying the high-temperature steam and spraying the dry ice pellets are performed simultaneously or sequentially. 
     
     
         3 . The method according to  claim 1 , wherein spraying the dry ice pellets comprises:
 rapidly freezing a layer of ammonium bisulfate covered on the surface of the thermal element of the heat exchanger at 0° C. to −78.5° C. using dry ice pellet particles shattered by hitting the thermal element to have cracks in the layer of ammonium bisulfate;   infiltrating the shattered dry ice pellet particles into the cracks of the layer of ammonium bisulfate; and   separating and removing ammonium bisulfate from the surface of the thermal element by sublimation of the dry ice particles.   
     
     
         4 . The method according to  claim 1 , wherein the heat exchanger is an air preheater.