1 Scope
This part of GB/T 16508 specifies the technical requirements for combustion systems of shell boiler.
This part is applicable to combustion systems of shell boiler defined in the range of GB/T 16508.1, including:
a)The fuel inlet pipeline, air supply system, smoke discharge system and combustion equipment of liquid-and gas-fuel fired boilers as well as all therelevant control and monitoring equipment;
b)The air supply system, smoke discharge system, combustion equipment and dust(slag) removal device of solid fuel fired grate firing boiler as well as all the relevant control and monitoring equipment.
2Normative References
The following documents for the application of this document are essential. Any dated reference, just dated edition applies to this document. For undated references, the latest edition (including any amendments) applies to this document.
GB 13271 Emission Standard of Air Pollutants for Boiler
GB/T 16508.5 Shell Boilers Part 5: Safety Appurtenances and Instruments
GB 17820 Natural Gas
GB/T 18342 Specifications of Coal for Chain and Travelling Grate Stoker Boiler
GB/T 21923 General Testing Rules for Solid Biofules
JB/T 3271 Specification for Travelling Grate Stokers
JB/T 3726 General Specification for Boiler Slag Removed Equipment
JB/T 9620 Specification for Reciprocating Grate
3Terminologies and Definitions
For the purposes of this document, the following terminologies and definitions apply.
3.1
Liquid fuel
Natural organic fuel that is in liquid form under normal temperature and the liquid fuel obtained by processing the above natural organic fuel, such as light fuel oil and heavy fuel oil.
3.2
Gaseous fuel
Natural organic fuel or artificial fuelin the solid form under normal temperature.They are divided into light gas and heavy gas according to the relative density.The gas withrelative density lower than 1.3 is classified as light gas, for example natural gas, coke oven gas and blast furnace gas; the gas withrelative density higher than 1.3 is classified as heavy gas, for example, liquefied petroleum gas.
3.3
Solid fuel
Solid fossil fuel and biomass fuel and the solid fuel obtained by processing them.For example, coals withvarious qualities (lignite, bituminous coal, meagre coal, anthracite, etc.), biological solid fuel and the like.
3.4
Flame detector
Equipment used to detect flame or flame lifting and send signals to the control device, which generally consists of sensing device (signal amplifier may be installed if necessary) and switching device.
3.5
Interlock
Action of cuttingoff fuel supply; manual intervention is required for its restoration.
3.6
Relative density
The ratio of gas density todry air density under the same pressure and temperature condition.
3.7
Auxiliary combustion system
Combustion system arranged to ensure safety ignition and stable combustion.
3.8
Ignition device
Auxiliary equipment used for ensure safety ignition of the fuels.
3.9
Rate of riddlings
The mass ratio of the average grate coal leakage (including ash leakage) per hour to the coal consumption during test duration, expressed in percentage.
3.10
Uneven air distribution coefficient along grate horizontal
Index for measuring the homogeneity of air distribution along grate of the air chamber, expressed in percentage.
4Combustion Systems of Liquid and Gaseous Fuels
4.1 Fuel
4.1.1Basic requirements
4.1.1.1Without impacting the safe operation of the combustor, the liquid fuel shall reach the viscosity as required for its normal combustion at the combustor inlet.
4.1.1.2The natural gas shall meet the requirements specified in GB 17820.
4.1.1.3As for other types of fuel, or in case different fuels are burning simultaneously, appropriate technical measures which has been verified shall be taken to achieve safe and high-efficient combustion, and the discharge of combustion product shall meet those specified in GB 13271.
4.1.2Fuel inlet pipeline
4.1.2.1The fuel oil pipeline shall meet the following requirements:
a)Rigid tube should be adopted for the connection between the combustor and the fixed fuel oil supply line; in case flexible hoses made of nonmetallic material are adopted, they shall be wrapped by metal materials and as short as possible, besides they possess sufficient bending radius during installation.
b)Strength test shall be carried out after the fuel oil pipeline has been installed, with the test pressure being 1.3 times of the maximum permissible pressure and at least 0.5MPa (gauge pressure);
c)Pressure relief valves shall be installed on the fuel oil pipeline to achieve overpressure protection;
d)Automatic temperature control device as well as high and low fuel oil temperature interlock protection device shall be provided for heavy fuel oil heater to ensure that the heavy fuel oil reaches the viscosity as required for the atomization of combustor nozzle.If steam heating is adopted for heavy-fuel oil heating, the pipe section introducing the steam shall be carried out with thermal insulation so as to avoid scald;
e)The fuel oil supply main shall be equipped with a manual rapid cut-off valve so as to cut off the fuel oil supply for the combustor quickly.Manual rapid cut-off valve shall be installed in the site that is safe and convenient for operation.
4.1.2.2The gas pipeline shall meet the following requirements:
a)The gas combustor and the gas pipeline should be connected with rigid tube; if the flexible hose made of non-metallic materials is adopted, it shall meet the requirements for pressure resistance of gas pipeline.
b)On completion of gas pipeline installation, tightness test and deformation test shall be carried out under the pressure 1.5 times larger than the maximum permissible pressure (but not less than 4 kPa) by adopting the air or inert gas.
c)The gas pipeline shall be implemented with necessary overpressure protection through a safety shut-off valve and a pressure release valve;
d)The outlet of gas control valve shall be installed with filter device, which may be integrated with the downstream gas control valve.The pore size of the filter shall not be larger than 1.5 mm; and the inlet and outlet of the filter shall be installed with permanent pressure measuring point;
e)As for boilers fuel for fuels with high carbon monoxide content such as blast furnace gas, coke oven gas and the like, the gas system shall be equipped with online monitoring device for carbon monoxide.
f)Manual rapid cut-off valve shall be arranged at the upstream of every automatic control valve in the main gas control valve system so as to cut off the air source of the combustor quickly.Manual rapid cut-off valve shall be installed in the site which is safe and convenient for operation.
4.1.3Measurement of fuel
Each boiler shall be installed with instruments for indicating, integrating and recording the fuel quantity.
4.2Air supply system
4.2.1 The pressure measuring device of air supply shall be arranged before every combustor on the air supply pipeline in case a fanis shared by several combustors.
4.2.2As for the combustion system with multiple combustors, in case the air required for combustion is provided by shared air supply equipment, a cut off device shall be arranged at the air pipe of every combustor.The requirements for cut off device are as follows:
a)The switching position of cut off device shall be clearly indicated.
b)In case the fuel supply of combustor is cut off, the air supply shall be cut off (if necessary, only the minimum opening is allowed) automatically at the same time.
4.3Smoke discharge system
4.3.1The smoke discharge system of boiler shall possess favorable sealing performance.
4.3.2The following operating parameters of the smoke discharge system shall be monitored to meet the requirements of safe and energy-saving operation.
a)Smoke discharge temperature;
b)As for steam boiler with its rated evaporation capacitygreater than 4 t/h or hot-water boiler with its rated thermal powergreater than 2.8 MW, the oxygen content of discharged smoke shall be monitored;
c)If the boiler is equipped with induced draft fan, the load current of the induced draft fan shall be monitored.In case the rated evaporation capacity of steam boiler is greater than 4 t/h or the rated thermal power of hot-water boiler is greater than 2.8 MW, the opening of the inlet damper of the induced draft fan or the rotation speed of the speed fan shall be monitored.
4.3.3On condition that flammable and explosive mixture will not be generated, the discharge flue of several boilers may be linked together and share one stack.Inside the branch flue of each boiler, there shall be arranged with a flue damper, which shall ensure reliable sealing.The damper shall be provided with reliable stop block so as to ensure it is in the fully opened position during the boiler operation, and it shall not be closed automatically.
4.4Combustion system
4.4.1Type selection of combustors
The type selection of combustor shall be in accordance with the following basic requirements;
a)The actual output of combustor shall not be less than the ratio of boiler thermal power to the boiler thermalefficiency.The actual output is the output power that shall be reached bythe combustor under the premise of overcoming the resistance of boiler flue gas;
b)The flame of the combustor shall not contact directly with the combustion chamber wall surface or the furnace tube.
4.4.2Safety and control requirements of combustion systems
4.4.2.1The combustors shall be equipped with ignition devices and able to ensure the safe ignition of ignition combustor and main combustor.
4.4.2.2The flame detector shall meet the following requirements:
a)The combustors shall be equipped with flame detector and able to verify whether the flame is established;
b)The installation site of flame detector shall prevent it from the interference of external signal.
c)On such occasion where the ignition flame and main flame are respectively arranged with independent flame detectors, the ignition flame shall not impact the detection of main flame.
4.4.2.3As for pressure atomized fuel oil combustor withrated fuel oilnot greater than 100 kg/h, safety shut-off valve shall be installed between the fuel oil pump and the nozzle; besides, an integrated structure may be adopted for safety shut-off valve and the fuel oil pump and it shall meet the following requirements:
a)The single-stage combustor shall be arranged with at least one set of safety shut-off valve;
b)As for two-stage or multi-stage control combustor, each nozzle shall be arranged with one set of safety shut-off valve;
c)As for the combustor equipped with return-fuel oil nozzle, both its fuel oil supply pipe and return fuel oil pipe shall respectively be arranged with one set of safety shut-off valves;
d)If the nozzle shut-off valve, through test, may serve as the safety shut-off device, then both the fuel oil supply pipe and the return fuel oil pipe may respectively be arranged with nozzle shut-off valves;
e)If the fuel oil atomizer adopts the return-fuel oil nozzle and the fuel oil quantity is greater than 30kg/h, then the fuel oil pressure monitoring device shall be arranged on the return fuel oil pipe to monitor the pressure within the fuel oil return pipe.
4.4.2.4As for pressure atomized fuel oil combustor with its rated fuel oil being greater than 100 kg/h, safety shut-off valve shall be installed between the fuel oil pump and the nozzle, and an integrated structure may be adopted for safety shut-off valve and the fuel oil pump,which shall meet the following requirements:
a)Two safety shut-off valves in seriesarrangement shall be arranged on the fuel oil supply pipe, of which one can be shut off quickly and the other canserves as the final control part of the heat input for combustion chamber and must be shut off within 5s;
b)As for the combustor equipped with return-fuel oil nozzles, two safety shut-off valves shall be arranged on the return fuel oil pipe and one pressure monitoring device shall be arranged between the output regulator and safety shut-off valve;
c)If the nozzle shut-off valve, through testing,may serve as the safety shut-off valve, then it may replace the safety shut-off valve to be respectively installed on the fuel oil supply pipe and return fuel oil pipe;
d)The safety shut-off valves shall be interlocked, and if the safety shut-off valve on the fuel oil supply pipe is opened, then that on the fuel oil return pipe shall not be closed (this requirements is not applicable to the occasion where the multi-stage control combustor is undergoing full load operation); the interlock device shall ensure that excessive pressurization shall not be generated between two safety shut-off valves.
4.4.2.5For the rotating-cup atomizing fuel oil combustor and medium atomizing fuel oil combustor, their safety shut-off valves shall be selected and arranged by referring to those requirements specified for pressure atomizing combustor.
4.4.2.6During the initiating processes of combustor equipped with preheating device, before reaching the minimum preheating temperature as required for the fuel oil, the automatic safety shut off equipment shall not cut off the fuel supply of the combustor.
4.4.2.7The main gas control valve system of gas combustor shall meet the following requirements:
a)The main gas control valve of the combustor shall be arranged with twoautomatic safety shut-off valves in seriesor combination valves;
b)The gas control valves with its specification less than or equal to 100mm shall be cut off safely within 1s, and those greater than 100mm shall be cut off safely within 3s.
c)As for the combustor with the rated output thermal power greater than 1.2 MW, its main gas control valve system shall be arranged with valve leakage detection device;
d)The main gas control valve system of the combustor shall be arranged with at least one pressure sensor at its upstream;
e)In case an independent ignition combustor is arranged, the main gas control valve may be opened and establish the main flame only after the flame has been ignited and verified by flame detector.
4.4.2.8The ignition safety time and extinction safety time of fuel oil and gas combustor shall be in accordance with the relevant requirements of GB/T 16508.5.
4.4.2.9Before the ignition of combustor, the combustion chamber and flue must be pre-purged.
Foreword i
1 Scope
2 Normative References
3 Terminologies and Definitions
4 Combustion Systems of Liquid and Gaseous Fuels
5 Layer Combustion System of Solid Fuel
