6.3　Arrangement of Coal Bunker Bay

6.3.1　The elevation of coal feeder floor in the coal bunker bay shall be determined according to the following requirements:

1　For pulverized coal firing boilers,the elevation of coal feeder floor shall be determined based on the space required for accommodating coal mills（except for fan mills）,pulverized coal feeding pipes and the associated maintenance and lifting facilities.If the conditions permit,the elevation of coal feeder floor should be the same as that of boiler operating floor.If fan mills are adopted,the elevation of coal feeder floor shall meet the requirements for arranging the drying section.

2　For CFB boilers,the elevation of coal feeder floor shall be determined based on the elevation of coal feeding port（including coal spreading devices）,the required number of stages of coal feeder,the coal feeding distance,the arrangement of outlet valves of coal feeder,and other relevant factors.

6.3.2　The arrangement of the coal conveying belt floor in coal bunker bay shall meet the requirements below:

1　The elevation of coal conveying belt floor shall be determined based on the design requirements of raw coal banker and pulverized coal bin.

2　Necessary operation access shall be provided on both sides of the belt conveyor.

3　On the coal conveying belt floor,there shall be provided necessary ventilation and dedusting equipment,and floor cleaning and water drainage facilities.

4　At the head end of belt conveyor,maintenance and lifting devices shall be provided.

6.3.3　The arrangement of side coal bunker bay should be designed in combination with that of boiler house.

6.3.4　The coal storage capacity of raw coal bunker and pulverized coal bin shall comply with the following requirements:

1　For medium speed direct fired pulverizing system,the raw coal bunkers（except for those serving the standby mills）should have a total effective storage capacity sufficient to serve the boilers operating on design coal under the maximum continuous evaporation rating（BMCR in short）for more than 8 hours.For double-inlet-and-double-outlet tube mill pulverizing system,the raw coal bunker should have a total effective storage capacity sufficient to serve the boilers operating on design coal under BMCR condition for more than 8 hours.

2　For bin storage type pulverizing system,the pulverized coal bunker should have an effective storage capacity sufficient to serve the boilers operating on design coal under BMCR condition for more than two hours.The raw coal bunkers and pulverized coal bunkers should have a total effective coal storage capacity sufficient to serve the boilers operating on design coal under BMCR condition for more than 8 hours.

3　For CFB boiler burning low calorific value coal,the raw coal bunkers should have a total effective coal storage capacity sufficient to serve the boilers operating on design coal under BMCR condition for more than six hours.

4　For boilers burning pulverized lignite,the raw coal bunkers（except for those serving the standby mills）should have a total effective storage capacity sufficient to serve the boilers operating on design coal under BMCR condition for more than six hours.

5　For power plants where the coal handling system operates in two-shift system,the total effective coal storage capacity of raw coal bunkers for direct fired pulverizing system,or that of raw coal bunkers and pulverized coal bins for storage pulverizing system may be designed to serve the boilers operating on design coal under BMCR condition for more than 10 hours.

6.3.5　The design of raw coal bunkers shall comply with the following requirements:

1　The raw coal bunker should be designed into columniform cylinder of steel structure；when it is designed to be biconvex cylinder,the reduction rate of cross section at the outlet section shall not be less than 0.7 and the inside diameter of the outlet shall not be less than 600 mm；when it is designed to be conical cylinder,the included angle between its outlet wall surface and the horizontal plane shall be no less than 60°for pulverized coal boilers,or no less than 70°for CFB boilers.

2　If pulverized coal boiler is provided with rectangular raw coal bunkers,the included angle between the line where any two adjacent walls meet and the horizontal plane shall be no less than 55°and the included angle between the wall surface and horizontal plane shall not be less than 60°；if burning bituminous coal and lignite that are highly viscous and volatile or are flammable,the included angle between the line where any two adjacent walls meet and the horizontal plane shall be no less than 65°,and the included angle between the wall surface and the horizontal plane shall be no less than 70°.

3　If CFB（Circulating Fluidized Bed Boiler）is provided with rectangular raw coal bunkers,the included angle between the line where any two adjacent walls meet and the horizontal plane shall be no less than 70°.

4　The inner side of the intersection angle of two adjacent walls of rectangular raw coal bunkers shall be of circular arc shape with the arc radius being no less than 200 mm.

5　The inner walls of raw coal bunkers shall be smooth and abrasion-proof.When burning coal that is prone to result in clogging,the outlet section of raw coal bunker should be made of stainless steel clad plates lined with stainless steel plates or other smooth,flame-retardant and abrasion resistant materials；the outer walls of raw coal bunker should be provided with devices against clogging.

6　In severely cold regions,anti-freezing insulation measures shall be taken on walls of the raw coal bunker of steel structures and reinforced concrete raw coal bunker close to the external wall of the main power houses as well as on walls exposed to the atmosphere.

6.3.6　The fire protection and explosion prevention design of pulverized coal bins shall comply with the national standards currently in force,GB 50229 Fire Prevention for the Design of Thermal Power Plant and Substation and DL/T 5203 Technical Code for Explosion Prevention Design of Coal and Pulverized Coal Preparation System of Fossil-fueled Power Plants.