How is the heating surface of a boiler positioned?

The screen superheater is composed of steel tubes with an outer diameter of 32–42 mm and header tanks; it is generally suspended above the furnace chamber or at the furnace outlet, where it absorbs both convective heat and radiant heat. The proportion of convective or radiant heat absorbed, relative to the total heat absorbed, depends on the location of the screen superheater. The pitch S1 between the tubes is generally 500–1000 mm, and the number of tubes per screen is usually 15–30, as determined by the required steam flow rate. The ratio of the pitch S2 between adjacent tubes to the tube diameter, S2/d, ranges from 1.1 to 1.25. A convective superheater consists of serpentine tubes made from seamless steel pipes, along with two or more header tanks. The outer diameter of the serpentine tubes ranges from 32 to 42 mm; they are generally arranged in a sequential pattern. The ratio of the transverse pitch to the tube’s outer diameter, S1/d, is between 2 and 3. The longitudinal pitch depends on the radius of the bends, and the ratio of this pitch to the tube’s outer diameter, S2/d, is typically between 1.6 and 2.5. Welding is used for connecting the superheater tubes to the header. Convective superheaters can be divided into vertical and horizontal types based on the arrangement of the coiled tubes ； Based on the relative flow direction of flue gas and steam, they can be classified into four types: co-current, counter-current, double counter-current, and mixed flow. The reheater consists of serpentine tubes and headers; its structure is similar to that of the superheater. However, the steam pressure in the reheater is lower, at about one-fifth of the steam pressure in the superheater. The heat release coefficient of the reheated steam is low, resulting in poor cooling capacity for the tube walls. The reheater is generally installed in areas where the flue gas temperature is lower. The arrangement of the reheater serpentines can be divided into vertical and horizontal types. Vertical reheaters are generally installed in the boiler’s horizontal flue, and their structure is similar to that of vertical convective superheaters ； The horizontal reheater is generally installed in the boiler’s rear shaft, and its structure is similar to that of the horizontal convective superheater. The heating surfaces of the economizer are located in the rear flue of the boiler, and can be divided into cast-iron economizers and steel-tube economizers. Cast iron economizers can only be used as non-boiling economizers at a pressure of 2.5 MPa. Cast iron is corrosion-resistant, and its tubes have thick walls; therefore it can be utilized in industrial boilers where the feed water has not been deoxygenated, as well as in areas where there is severe external corrosion of the flue gases ； The structure of the tubular economizer is similar to that of the horizontal reheater or horizontal convective superheater; it consists of a series of coiled tubes and headers. The tubes are generally arranged in rows, with an outer diameter of 25–42 mm. They are installed horizontally, with a transverse spacing to outer diameter ratio of 2.0–3.0, and a longitudinal spacing to outer diameter ratio of 1.5–2.0. The economizer headers are usually placed outside the furnace wall, and they are welded to the tubes outside the wall.

The section above introduced various heating surfaces, but it didn’t explain how to locate them. . . Such as the positioning between the screen-type superheating tubes, the positioning between tube screens, and so on. .