8.6　Ignition and Combustion Supporting Fuel System

8.6.1　The ignition and combustion supporting fuel system shall be determined through techno-economic analysis taking into consideration the coal type,ignition mode,oil（gas）source,fuel oil（gas）price and fuel transportation conditions and shall comply with the following requirements:

1　Light oil should be adopted for ignition and combustion supporting under low load condition.

2　Heavy oil may be adopted for ignition and combustion supporting under low load condition if it is readily available and has satisfactory quality.

3　Combustible gas may be used instead if the engineering conditions permit.

8.6.2　The type of ignition and combustion supporting system of boilers shall be determined according to the type of coal,boiler,coal pulverizing system,and ignition and combustion supporting fuel.When burning suitable types of coal,the oil-saving ignition systems such as plasma ignition,micro-oil ignition and small gasified oil guns should be adopted.

The design of oil-saving ignition system should be incorporated into the overall design of boiler.

8.6.3　The design output of the ignition and combustion supporting system in the plant shall meet the following requirements:

1　The capacity of the fuel oil（gas）system should not be less than the sum of fuel oil（gas）amount required by one of the largest boiler to ignite and the fuel oil（gas）amount required for supporting combustion during start-up of another boiler having the maximum capacity.If the boilers burn such types of coal that require combustion supporting oil（gas）under low load operation,the capacity of the fuel oil（gas）system should not be less than the sum of fuel oil（gas）amount required for supporting combustion of one boiler during start-up and fuel oil（gas）amount required for supporting combustion of one boiler under low load operation.

2　The return oil flow of the system shall be determined according to the characteristics of fuel oil spray nozzles,combustion safety protection requirements and fuel oil parameters and shall be no less than 10%of the design output of the system.

3　The design output of the system is the sum of fuel oil（gas）flow and the minimum return oil flow,with a margin being no less than 10%.

4　When the boilers adopt oil-saving ignition devices,the design output of the system maybe reduced accordingly based on the relevant requirements in item 1,2 and 3 of this clause,and the output of ignition oil guns should be reduced through consultation with the boiler manufacturer.

8.6.4　The number and capacity of oil tanks should be determined by comprehensively considering the capacity of a single boiler,coal type,ignition mode,oil type,oil consumption and mode and period of oil delivery,and shall comply with the following requirements:

1　For light oil,two oil tanks should be provided；while for heavy oil,three oil tanks should be provided.

2　For newly-built power plants equipped with oil-saving ignition system,the capacity of oil tank should comply with the following requirements:

1）For units rated 200MW and below,2×200m3；

2）For units rated at 300MW,2×（200m3-300m3）；

3）For units rated at 600MW,2×（300m3-500m3）；

4）For units rated at 1000MW,2×（500m3-800m3）.

3　For newly-built power plants equipped with conventional ignition system,the capacity of oil tank should comply with the following requirements:

1）For units rated at 125MW,2×500m3or 3×200m3；

2）For units rated at 200MW,2×1000m3or 3×500m3；

3）For units rated at 300MW,2×（1000m3-1500m3）or 3×1000m3；

4）For units rated at 600MW,2×（1500m3-2000m3）or 3×（1000m3-1500m3）；

5）For units rated above 1000MW,2×2000m3or 3×1500m3.

4　For circulating fluidized bed（CFB）boilers,the capacity of oil tank should comply with the following requirements:

1）For units rated at 300MW,2×800m3；

2）For units rated at 200MW and below,2×500m3.

5　For extended power plants,the existing fuel oil facilities shall be fully used,and the number and capacity of additional oil tanks shall be determined according to the specific engineering conditions.

6　If the boilers burn such types of coal that require combustion supporting oil under low load operation,the capacity of a single oil tank should not be less than the monthly average oil consumption of the entire plant.

7　If the oil tank area is far away from the main power houses or there are many boilers installed,supporting oil tanks may be provided nearby the main power houses.One supporting oil tank may be provided for each boiler and should be sized with a capacity below:

1）For units rated at 200MW and below,100m3；

2）For units rated at 300MW,200m3；

3）For units rated at 600MW,300m3；

4）For units rated at 1000MW,500m3；

5）When multiple boilers share one supporting oil tank,it should have a capacity sufficient to accommodate the total oil consumption by the oil system of the connected boilers for no less than three hours.

8.6.5　Railway,highway,waterway or pipe transportation may be adopted for delivering fuel oil for ignition,startup and combustion supporting of boilers,and shall meet the following requirements:

1　When railway transportation is adopted for fuel oil transportation,the length of the unloading station should be considered for accommodating 4-10 oil wagons to unload oil simultaneously.The elapse of time from the entering of the fuel oil wagons into the power plant to completion of unloading shall be 6-12hours.

2　When oil tanker trucks are used for fuel oil transportation,platforms for oil unloading shall be provided and the site shall allow the drivers to move in reverse.

3　When fuel oil delivery is through waterway transportation,the construction of the wharf for fuel oil unloading should be carried out in combination with the construction of the wharf for handling the ash,the wharf for handling large components,or coal wharf.

4　When the fuel oil source is nearby and the conditions permit,fuel oil may be delivered through piping.

8.6.6　The mode of fuel oil unloading shall be determined through techno-economic analysis taking into account the fuel oil characteristics,mode of transportation and oil tank conditions.The type,number,flow and head of unloading pumps shall comply with the following requirements:

1　The type of unloading pumps shall be selected according to the oil viscosity,unloading mode and fire protection rules.

2　The number of unloading pumps should be no less than 2.When the largest pump is out of service,the rest pumps shall be able to unload the oil carried by vehicles or ships within the specified time.

3　The head of unloading pumps and the capacity of the associated electric motors shall be calculated considering the maximum viscosity of fuel oil delivered.The margin of the head should not be less than 30%.

8.6.7　The type,number,flow and head of oil delivery and supply pumps shall comply with the following requirements:

1　The type of oil delivery and supply pump shall be determined in accordance with the oil quality and oil supply parameters.Centrifugal pumps or screw pumps should be used.

2　The number of oil delivery and supply pumps should be three,each of which should have a capacity of 50%or 35%.

3　The flow margin of oil delivery and supply pumps should not be less than 10%,and the head margin should not be less than 5%.When calculating the head,the margin of total resistance of the fuel oil piping system（without regard to the atomizing oil pressure of oil guns and height difference）should not be less than 30%.

8.6.8　Fast cut-off valves and flow measuring devices shall be installed on the oil supply and return piping of each boiler.

8.6.9　In case of fuel oil that is highly viscous and has a solidifying point higher than the minimum daily average atmospheric temperature in winter,the oil unloading,storage and supply systems shall be provided with heating,heat tracing and purging facilities.Provisions shall be made for the steam purging system to prevent backflow of fuel oil.When oil temperature is higher than the specified value,cooling measures shall be taken on oil tanks or oil return piping.

8.6.10　The fuel oil pump house and fuel oil heaters shall be arranged in accordance with the following requirements:

1　The fuel oil pump house should be arranged in the vicinity of the oil storage area.The pump house for supporting oil tanks should be arranged nearby the boiler house.

2　Ventilation,hoisting facilities,necessary repair yard and duty room shall be appropriately arranged in the fuel oil pump house.If the automatic control and fire fighting facilities allows unattended operation,the duty room may be eliminated.

3　The electrical equipment provided in the fuel oil pump house shall be of anti-explosion type.

4　The fuel oil heaters located outside the tanks should be arranged outdoors,and,alternatively,may be arranged nearby the boiler house if the condition permit.

8.6.11　Waste oil and wastewater collection facilities and associated oil-containing wastewater treatment facilities shall be provided in the fuel oil system.

8.6.12　The design of anti-explosion prevention,fire resistance,anti-static and anti-lightning facilities of the fuel oil system shall comply with the relevant requirements in the current national standards GB 50074 Code for Design of Oil Depot,GB 50058 Specifications for Design of Electric Systems in Places with Explosion and Fire and GB 50229 Code for Design of Electrical Installation for Explosive and Fire Hazardous Atmospheres.