Coal Fired CFB Boiler has developed rapidly in China due to its superior fuel adaptability and good running performance. As national energy-saving indicator and environmental emission standard become more stringent, the thermal performance and environmental emission indicator of some current Coal CFB boiler failed to meet relevant requirement. This paper takes a 75t/h circulating fluidized bed boiler as an example to analyze the relevant transformation technology and effect.
I. Transformation Background
Original steam boiler technical parameter
- Model: TG-75/5.29-M
- Date of initial operation: Jan. 1995
- Main design parameters:
Capacity 75t/h
Rated steam temperature 450C
Rated steam pressure 5.29MPa
Flue gas temperature 150C
Feed water temperature 150C
Design fuel soft coal
Efficiency 87.2%
The coal fired CFB boiler was used for power generation in a tire factory. It has been running for about 140,000 hours since initial operation. Due to the change in production scale and process, the output parameter was reduced. Process steam pressure is 3.0-3.3 MPa and temperature is 400-420C; the load is only 50~60t/h.
II. Transformation Solution
In combination with the user status and process requirement, we decide to make some optimization over the Coal Fired CFB Boiler. After transformation, the CFB boiler is mainly composed of drum, suspended membrane wall furnace, cyclone separator, refeeder and shaft convection heating surface. The drum and cyclone separator are placed on the steel frame; furnace is suspended; high temperature superheater is suspended above the shaft flue duct; low temperature superheater and economizer are supported on the bearing beam; air preheater is supported on the steel frame. The furnace expands downward.
The coal fired CFB boiler parameter after transformation is as follows:
Model DHX60-3.5/450-M
Capacity 60t/h
Rated steam pressure 3.5MPa
Rated steam temperature 450C
Feed water temperature 105C
Flue gas temperature 135C
Primary air temperature 143C
Secondary air temperature 143C
Design efficiency 88.87%
Blow down efficiency ≤2%
Excess air coefficient at flue gas outlet 1.38
Safe and stable operating range 30%-100%
Structure: medium temperature and low pressure, single drum, natural circulation.
