D-type boiler has a large steam drum at the top, vertically connected to a small water drum at the bottom. D-type water tube boiler is to reduce overall project cycle time. Two sets 180t/h boilers adopt modular design, module delivery, and on-site assembly. We provide technical guidance for on-site installation and commissioning.

1. Structural Characteristics of D-type Boiler

The convection tube bundle and drum are expanded connection. First convection tube bundle is left membrane wall and partition wall; second bundle is right membrane wall and partition wall. First convection tube bundle is evaporating heating surface, and second convection tube bundle is down-comer of upper drum.

D-type boiler has no frame, and it is a self-supporting structure. The structure is compact, occupation is small, weight is light, on-site installation workload is small and installation speed is fast. Thus, it is suitable for overseas projects with tight delivery period.

2. Main parameters of D-type Boiler

It mainly includes two 180t/h boiler (indoor layout), two FD fan, one 10,000m³ water tank, and one 90m steel chimney. One 450t/h deaerated water facility (deaerator, deaerator pump, deoxidant dosing device, etc.). Each gas boiler has six sets steam soot blowers with automatic control system. Four sets fully retractable soot blowers are for boiler body, and two sets semi-retractable soot blowers are for economizer. Each boiler has one FD fan, and two gas boilers share one chimney (height 90m, outlet diameter 3.3m). Continuous blowdown expansion tank, intermittent blowdown expansion tank and cooler are available. The continuous drainage after cooling is for the make-up water of circulating water.

3. Combustion Characteristics of D-type boiler

Each gas steam boiler has 4 burners (single rated power 48.7 MW). When using fuel gas, production load is 25%-110% of rated capacity; using fuel oil, load is 35%-110% of rated capacity.

3.1 Steam-water system

The demineralized water capacity is 420t/h, and oxygen content is 7μg/g. The process condensate is recovered and treated as boiler feed water, and pH value is 8.5-9.5. It has a unique top feed water preheater.

3.2 Flue gas and air system

Each gas steam boiler has one FD fan with a design air volume of 4026 m3/min. The air pressure at FD fan outlet is 3.16 kPa, and flue gas pressure before economizer is 0.34 kPa.

3.3 Automatic control system

It includes automatic adjustment of water supply, combustion process and superheated steam temperature, and automatic ignition, soot blowing and blowdown. BMS system collects the furnace pressure, fuel properties, drum water level, flue gas oxygen content, and adjusts the burner accordingly.