8.4　Flue Gas Precipitator and Emission System

8.4.1　The type selection of precipitators shall comply with the following requirements:

1　The type of precipitator shall be determined taking into account the requirements on the flow and concentration of dust emission set forth in the environmental impact assessment report,boiler type,coal ash characteristics,process,site conditions,and the requirements on comprehensive utilization of ash.

2　If coal types are favorable,electrostatic precipitators should be used.

3　If the characteristics of fly ash produced by burning coal are not favorable for dedusting with electrostatic precipitators or cannot meet the environmental protection requirements,fabric filter or flue gas conditioning system plus electrostatic precipitators or other types of dedusting equipment may be adopted.

4　If the conditions permit,the use of low temperature electrostatic precipitator system may be considered.

8.4.2　The number and guaranteed dust collection efficiency of electrostatic precipitators shall comply with the following requirements.

1　For units rated 200MW and above,each boiler should be equipped with at least two electrostatic precipitators；for units rated below 200MW,each boiler may be equipped with only one electrostatic precipitator.

2　The selected electrostatic precipitators shall be able to achieve the guaranteed dust collection efficiency under any of the following cases:

1）The flue gas flow of precipitator is the flow of flue gas leaving air preheater when boiler operates on design coal under BMCR condition,plus a margin of 10%；the flue gas temperature is the temperature of flue gas leaving air preheater when boiler operates on design coal under BMCR condition,plus a margin of 10-15℃；and one of the power supply sections is out of service.

2）The flue gas flow of precipitator is the flow of flue gas leaving air preheater when boiler operates on check coal under BMCR condition；and the flue gas temperature is the temperature of flue gas leaving air preheater when boiler operates on check coal under BMCR condition.

8.4.3　The number and guaranteed dust collection efficiency of fabric filters shall comply with the following requirements:

1　Each boiler should be equipped with at least two fabric filters.

2　The selected fabric filters shall be able to achieve the guaranteed duct collection efficiency under any of following cases:

1）The flue gas flow of filters is the flow of flue gas leaving air preheater when boiler operates on design coal under BMCR condition,plus a margin of 10%；the flue gas temperature is the temperature of flue gas leaving air preheater when boiler operates on design coal under BMCR condition,plus a margin of 10-15℃；and one passage or fabric filters of one gas inlet chamber are out of service.

2）The flue gas flow of filters is the flow of flue gas leaving air preheater when boiler operates on check coal under BMCR condition；and the flue gas temperature is the temperature of flue gas leaving air preheater when boiler operates on check coal under BMCR condition.

8.4.4　The flue gas from boilers may also be emitted through chimneys or flue gas discharged cooling towers.When flue gas discharged cooling tower is adopted,its design requirements shall meet the provisions in 17.6.7 herein；when chimneys are used to emit flue gas,the type and number thereof shall comply with the following requirements:

1　The type,height of chimneys and velocity of flue gas leaving the chimneys shall be determined according to the environmental impact assessment results and anti-corrosion requirements of the chimneys,while taking into consideration the number of boilers installed synchronously,arrangement of chimneys and their structural economy.

2　The quantity of boilers sharing the same chimney should be selected as follows:

1）For units rated 600MW and below,2-4 boilers for each chimney；

2）For units rated above 600MW,2 boilers for each chimney.

8.4.5　The classification of corrosion levels of flue gas shall comply with the following requirements:

1　The flue gas emitted from circulating fluidized bed（CFB）boilers and the flue gas that has been treated with dry flue gas desulphurization shall be rated as weak corrosivity level.

2　The flue gas treated with semi-dry flue gas desulphurization shall be rated as medium corrosivity level.

3　The wet flue gas treated with wet flue gas desulphurization shall be rated as strong corrosivity level.