The membrane type water wall welds finned tubes (or flat steel and smooth tubes) to each other to form a whole tube panel. It has the advantage of good air tightness; the outside of the tube screen only needs to be covered with a thinner insulation material, and the high-temperature flue gas of the furnace does not directly contact the furnace wall, which is beneficial to prevent slagging; the tube screen can be prefabricated in the factory for convenience Site installation. Large-capacity, high-temperature and high-pressure boilers mostly use membrane water walls
Pin type water wall is also called barbed tube water wall. It is welded with a certain length of round steel on the surface of the smooth tube according to the requirements, and the use of pins can firmly lay the refractory coating on the water wall to form the fire protection zone, the liquid slagging slag pool and the slag section, and the cyclone furnace Cyclone. The water-cooled wall of the internally threaded pipe is a pipe with single-end or multi-end spiral grooves on the inner wall of the pipe. The internally threaded tube is used in the high heat load area of the furnace of the once-through boiler, the subcritical parameter forced circulation boiler and the natural circulation boiler furnace or the water wall tube section with high vaporization rate. When the working fluid flows in the internally threaded pipe, it will be strongly disturbed, causing the water in the steam-water mixture to press against the pipe wall, and forcing the steam bubbles to leave the wall and be taken away by the water, thereby destroying the formation of the steam film, preventing the deterioration of boiling heat The wall temperature of the water wall decreases. The double-sided exposure water wall refers to a water wall arranged in the furnace space along the furnace height to absorb radiant heat on both sides. It is mostly used in large-capacity boilers. Carbon steel is generally used as water wall material. When the boiler pressure is above 14 MPa, some alloy steels are also used. Tube outer diameter: 51～83mm for natural circulation boilers; 22～60mm for multiple forced circulation boilers and once-through boilers. The water wall of the once-through boiler is not necessarily vertical like a natural circulation boiler, but can also be horizontally surrounded or in other forms. When the parameter is high, especially in once-through boilers, in order to prevent the deterioration of heat transfer in the high heat load area of the furnace, internally threaded tubes or spoilers are often installed in the tubes.
The advantages of membrane water wall
(1) Ensure the tightness of the furnace wall and reduce air leakage in the combustion chamber.
(2) Realize full water cooling of the combustion chamber, which helps prevent coking in the case of enhanced combustion.
(3) The heat storage capacity is small, the combustion chamber heats up quickly, and cools down quickly, which can shorten the boiler startup and shutdown cooling time.
(4) It is suitable to adopt tube-laying furnace wall, which greatly reduces the load of the boiler frame and is convenient for suspension.
(5) Compared with the light pipe, the heat absorption capacity of the pipe is improved.
(6) Improve the pre-assembly degree of boiler components, facilitate and reduce the installation workload.