7.8　Limestone Milling System for CFB Boilers

7.8.1　For fossil fired power plants installed with more than one CFB boilers,the limestone milling system should be arranged outside the main power house as a common facility.

7.8.2　The limestone unloading facilities shall be arranged in accordance with the following requirements:

1　When limestone is transported by railway,the limestone unloading facilities may be arranged on the limestone storage yard.

2　When limestone is transported by roadway,relevant unloading facilities shall be provided in the plant area based on annual tons transported by trucks and shall conform to the following requirements:

1）Dumping trucks should be adopted to transport limestone.

2）When the annual tons of limestone transported by trucks is 30×104t and below,an unloading station shall be provided.The unloading station may be arranged on the limestone storage yard,in particular,one or more areas on the storage yard may be adopted as the unloading station.Grab crane,loader and coal bulldozer may be adopted to remove the limestone at the unloading station.

3）When the annual tons of limestone transported by trucks is above 30×104,the unloading station may be arranged in form of multiple receiving hoppers in series.

7.8.3　The limestone storage facilities in the plant area may use the limestone storage yard or storage silo having a capacity sufficient to accommodate no less than seven days of limestone consumption by corresponding units.The limestone storage yards should all be built into dry stone sheds to ensure that the limestone delivered to the milling system has a water content of less than 1%.When limestone is to be stored in the storage silo,it shall have a particle size of no larger than 25mm and water content of less than 1%before entering the silo.

7.8.4　The design output of the limestone handling system shall not be less than 200%of limestone consumption of corresponding units when operating on design coal and check coal under MCR conditions,whichever is greater.The limestone handling system should be arranged in single line.

7.8.5　The limestone crushing（or grinding）system shall be designed according to the following requirements:

1　When the incoming limestone has a particle size larger than 30mm,two-stage crushing devices should be provided.

Stage 1 is a crushing device,and stage 2 is a crushing or grinding device.

2　When incoming limestone has a particle size not larger than 30mm,one-stage crushing or grinding device may be provided.