Low-NOx CFB Boiler is the latest generation of Coal CFB boiler.

1. Brief Description of Low-NOx CFB Boiler Structure

CFB steam boiler features capacity of 20-260t/h and steam pressure of 1.25-13.7MPa. CFB hot water boiler features capacity of 14-168MW and outlet pressure of 0.7-1.6MPa.

This passage will introduce the main design features by taking an 90t/h Low-NOx CFB Boiler as an example.

1.1 Main technical parameters

Rated capacity: 90t/h

Seam pressure: 3.82MPa

Steam temperature: 450℃

Cold air temperature: 20℃

Primary air temperature: 150℃

Secondary air temperature: 150℃

Flue gas temperature: 135℃

Design coal: lean coal

Design heat efficiency: 91.58%

Desulfurization efficiency in furnace (Ca/S ratio=1:8): ≥95%

Ratio of primary to secondary air: 6:4

Ratio of ash to slag: 6:4

Consumption of fuel: 16.41t/h

1.2 Low-NOx CFB Boiler Structure

It adopts CFB combustion mode, and realizes circulating combustion of materials through cyclone separator and material return system. Low temperature and low nitrogen combustion achieves high efficiency, energy saving and ultra-low emission. The CFB boiler adopts single drum, natural circulation, centralized downcomer, balanced ventilation and high-efficiency adiabatic cyclone separator. High-temperature superheater, low-temperature superheater, high-temperature economizer, low-temperature economizer and air preheater are in the tail shaft.

Before entering the drum, boiler feed water is preheated by two-stage low-temperature economizer and one-stage high-temperature economizer.

2. Low-NOx CFB Boiler Design Features and Key Technology

2.1 Optimized furnace combustion achieves low emission

It adopts large furnace volum, low furnace temperature (850℃) and low flue gas flow rate (≤5m/s). The residence time of materials in the furnace is ≥6s, thus improving the burnout rate.

2.1 Efficient separation and return system

Adopt offset central cylinder high-efficiency cyclone separator to improve the separation efficiency.

2.3 Optimized design of secondary air system

Determine reasonable ratio of primary to secondary air, adopt low-resistance design and enhance the spraying energy of secondary air.

2.4 Suitable material fluidization air distribution system

The air distribution system adopts water-cooling air distribution plate and equal pressure water-cooling air chamber to ensure uniform air distribution. The drop-proof bell type cap ensures uniform fluidized combustion, reduces the resistance, and realizes low bed pressure operation.

2.5 Sealed feeding and automatic slag removal system

The air cushion type coal spreader uniformly drops the coal particle on the bed surface, improving fluidization quality.

2.6 Reserved SNCR system

The denitration adopts SNCR+SCR technology, and independent fly ash separation and removal flue duct is in front of the SCR. SNCR position is reserved at the inlet flue duct of separator to meet the demand of low NOx emission.