Calculation of BKZ boiler unit 420-140

Boiler unit BKZ-420-140, Barnaul Boiler Plant (BKZ) single-drum, with natural circulation, is designed to produce high-pressure steam when burning dry stone coal dust. Boiler layout is made according to U-shaped diagram. The furnace chamber is located in the first (ascending) gas duct. Steam superheater is located in rotary gas duct, water economizer and air heater - two-stage arrangement of tail heating surfaces are located in second descending gas duct. Boiler water volume - 116 m3, steam volume - 68 m3. The combustion chamber is prismatic in shape, completely shielded by pipes 60 × 6.0 mm with a pitch of 64 mm. Material - steel 20. Extent of shielding of a fire chamber χ=97.5%. The front and rear screens in the lower part form slopes of the "cold funnel." In the upper part of the furnace, the pipes of the rear screen form an "aerodynamic visor," which improves the aerodynamics of the furnace and partially shades the screens of the superheater from direct radiation of the flare. Screens are installed at the furnace outlet. The screen panels are suspended from the metal structures of the ceiling by the upper chambers and have the ability to freely expand down. To reduce the effect of uneven heating on circulation, all screens are divided into 18 circulation circuits (panels), which have independent upper and lower headers. Rear and front screens have 6 panels each, side screens - 3 panels. Two extreme panels of rear and front screens consist of 40 parallel connected pipes, four middle panels - of 33 pipes. The two outermost panels of the side screens consist of 37 parallel connected pipes, the middle panel - of 36 pipes. The coating on the boiler is multilayer of a lightweight type: a layer of refractory concrete is applied to the screen pipes on a bulk metal mesh, then there are layers of sovelite plates and an outer layer of sealing coating, also applied to the metal mesh. The coating is attached to the screens using studs welded to the screen pipes. The BKZ-420-140 boiler has one drum of welded construction, with an internal diameter of 1600 mm. The evaporation scheme is two-stage, with steam washing with feedwater. The first evaporation stage is included directly in the boiler drum, the second stage includes two groups of remote separation cyclones (426x36 mm, steel 20). Boiler superheater by the nature of thermal perception of semi-radiation - convective type. Semi-radiation part of superheater is composed of screens located in upper part of furnace (2nd stage of superheater). Convective part consists of third, fourth and first stages of superheater located in downhole gas duct, panels are also included, which form downhole gas duct of boiler (ceiling, rear and side walls of convective shaft). In the course of steam movement, the first stage of the superheater is counter-current, the third and fourth stages are direct-flow (relative to the movement of flue gases). To reduce temperature swings of steam, mixing and steam transfer from the left side of the boiler to the right and vice versa are used. Double-flow steam superheater (with independent control of steam temperature in each flow). Each control stage is made in the form of two chambers of steam coolers of injection type, with diameter - 325 mm. The water economizer is mounted on hollow beams cooled by air from the blast fan. To cool the water economizer during the start-up period, a RE recirculation line is provided - a drum connecting the input collectors of the economizer with the water space of the boiler drum. Drain line (emptying of economizer 2nd stage) is installed between output manifolds of the 1st stage and input manifolds of the 2nd stage. The water economizer is made of pipes with a diameter of 32x24, the material of the pipes is steel 20, the heating surface is 4979.7 m2. The air heater is tubular, two-stage, the material of the pipes is steel 3.In the course of gases, the second stage of the air heater is the first, the heating surface of which is 9180 m2 (live cross-section through gases 21.5 m2, through the air - 25.1 m2, the pitch of pipes 78 × 51 mm). The 2nd stage of the air heater is followed by the 1st stage of the water economizer, and then the 1st stage of the air heater with a heating surface of 19800 m2 (live cross-section by gases of 17.8 m2, by air - 25.1 m2, pipe pitch 62 × 40.5 mm).