The water cooling wall tube is the only heating surface in the evaporation equipment. It is a radiation heat transfer plane composed of continuously arranged tubes. It is close to the furnace wall to form the four walls of the furnace. Some large-capacity boilers arrange part of the water-cooled wall in the middle of the furnace. The two sides absorb the radiant heat of the flue gas respectively, forming the so-called double-sided exposure water wall. The inlet of the water cooling wall pipe is connected by the header, and the outlet can be connected by the header and then connected to the steam drum through the air duct, or it can be directly connected to the steam drum. The inlet and outlet headers of the water wall on each side of the furnace are divided into several, the number of which is determined by the width and depth of the furnace, and each header is connected with the water wall pipes to form a water wall screen.