What are the characteristics of double-drum water tube boiler?

According to its structural characteristics, double-drum water-tube boiler can be divided into D-shaped and KB-shaped. Here, ZOZEN Boiler will explain the structural principles and characteristics of two kinds of double longitudinal boiler tubes.

D-shaped double longitudinal drum water tube boiler structure

D-shaped double-longitudinal-drum water-tube boiler structure has a furnace on the right side and a convection tube bundle on the left side; The movable supports in the middle and both ends of the lower drum are fixed on the chassis of the main body, and the whole boiler is guaranteed to expand to both ends. The furnace is surrounded by membrane wall, which improves the air tightness and enhances the heat transfer effect. The main furnace types are SZS series oil-fired gas boilers, with evaporation capacity of 2-130t/h and working pressure of 1-5.3MPa.

The structural advantage of D-shaped double longitudinal boiler is that the furnace is arranged on one side of the double longitudinal boiler, and the other side is a convection flue. And the upper and lower longitudinal drums have large water capacity and good adaptability to load changes; Convection tube bundles are all bent water pipes with elastic structures; The furnace is long and narrow, which is suitable for mechanized grate with high thermal efficiency. Disadvantages: Dust is easy to accumulate between convection tube bundles, which will reduce the thermal efficiency if it is not removed in time; The quality of water supply is strict, otherwise the scale will not be easily removed.

KB-shaped double longitudinal drum water tube boiler

The structure of KB double longitudinal drum water tube boiler is mainly composed of upper and lower longitudinal drums, convection tube bundle, water wall tube, header and downcomer. The length of the lower drum is about half shorter than that of the upper drum, and the vacated space is provided with a furnace, a bent water pipe is arranged between the two drums, and water wall pipes are arranged around the furnace. The combustion equipment adopts coal thrower or coal thrower plus inverted chain grate, and the tail flue has economizer. High-temperature flue gas enters the rear convection flue from the outlet on the right side of the furnace, flows in an S-shape along two smoke separation walls, horizontally washes the convection tube bundle, then flows through the economizer from the left side of the furnace wall, and is discharged by the induced draft fan and chimney.

The water circulation of KB-shaped double-longitudinal boiler is divided into two parts: one part is that the water in the upper drum drops from the convection tube bundle with weak heat at the back to the lower drum, then rises from the convection tube bundle with strong heat at the front of the lower drum, and returns to the upper drum to form a circulation; The other part is that the water in the water wall tubes around the furnace is heated up to the upper drum, and the downcomer led out from the lower drum supplies water to the water wall tubes through various headers, thus forming a water cycle.

The main boiler type of KB double longitudinal boiler is SZL series chain grate boiler, the evaporation capacity is generally less than 35 tons/hour (t/h) and the working pressure is less than 2.5 megapascals (MPa). KB-shaped double longitudinal boiler with water tubes has the characteristics of wide adaptability to coal types, small floor space, convenient installation and high thermal efficiency.