Design of water spray fire extinguishing system fo

2022-08-19
  • Detail

Design of water spray fire extinguishing system for gas-fired boiler room

with the development of the city and the rise of many high-rise civil buildings, there are fewer and fewer sites for the ancillary facilities of high-rise civil buildings. The coal-fired boiler room has been unable to meet people's requirements for site, environment, safety and automatic control. Therefore, many projects have adopted oil-fired and gas-fired boilers, which are located inside buildings. At present, there are many oil fired boilers in oil and gas fired boilers. In large and medium-sized cities, gas-fired boilers are the development direction

gas is a kind of high-quality, efficient and clean environment-friendly boiler fuel in the next 15 years. The fuel gas used in gas-fired boilers mainly refers to natural gas or artificial gas. The components of natural gas are often not fixed, and the components are different in different places of origin, but they are mainly methane. At present, Beijing is promoting the natural gas of Changqing gas field in Shaanxi Gansu Ningxia, with a methane content of

%. The components of artificial gas are related to the production process. The hydrogen content of coking gas in Beijing is

59.2%

, and the methane content is

23.4%

. Methane and hydrogen are highly flammable and explosive gases. In Appendix IV of code for fire protection design of buildings (

gbj16

), it is listed that the lower explosion limit of natural gas is

, and the lower explosion limit of artificial gas is

6.2%

, all of which belong to class a combustible gases

gb50045

) stipulates that oil and gas boilers should be placed inside high-rise buildings, and their location and capacity are strictly limited. In the revised version of the "high standard"

, it is supplemented that the oil and gas boiler rooms in high-rise civil buildings should be equipped with water spray fire extinguishing systems

the root cause of gas-fired boiler accidents is that there is explosive mixed gas in the furnace or flue, which reaches the explosion limit and is burned by the furnace fire or the high temperature of the boiler itself, resulting in furnace explosion. Most of the causes of the accidents are caused by improper boiler ignition operation, and also due to the failure of the automatic computer to calculate and digitally display the impact absorption energy, impact toughness, pendulum lift angle and experimental average value of materials in the past two months, or the large fluctuation of the pre combustion pressure or air pressure of the burner during operation, which leads to fire off or backfire. In order to reduce the damage of explosion to the furnace and flue when mixed with gas, explosion proof doors are set at these two upper parts of the boiler. In case of gas explosion, the explosion-proof door will open due to the sudden rise of pressure in the furnace or flue, or break and release high-pressure gas, so as to reduce the damage degree of explosion. At this time, the boiler needs exposure protection, and water spray can play a role in cooling

in addition, gas-fired boilers need the protection of water spray fire extinguishing system before the gas concentration reaches the lower explosion limit due to gas leakage or some unexpected reasons. By using the mixing and dilution effect of water spray, the concentration of fuel gas can be reduced and the effect of fire prevention can be achieved

The version of

specifies four types: fire extinguishing, fire control, exposure protection and fire prevention, or a combination of the above. Code for design of water spray fire extinguishing system (

GB

hereinafter referred to as "water spray code"

nfpa15

all mentioned that the water spray fire extinguishing system can be used to fight against combustible gas fires. Therefore, the water spray fire extinguishing system is appropriate for the fire protection of gas-fired boiler room, and its main purpose is exposure protection and fire prevention

the updated version does not specify the design spray intensity of oil and gas boilers, and this parameter is the main basis for system design, which brings difficulties to the design. We refer to

nfpa15

. The value of the design water spray intensity is that the water spray intensity for extinguishing general combustible solid or liquid fire is not less than

6.1l/min.m2

20.4l/min.m2 (0.15gpm/ft2

0.5gpm/ft2),

the water spray intensity for fire control is not less than

20.4/min.m2 (0.50gpm/ft2)

, and exposure.The spray intensity of protection is not less than

10.2l/min.m2 (0.25gpm/ft2)

, The minimum water spray intensity of waterproof shall be determined according to the experience of the protected substance or the test data for high-speed mixing. The above data is of reference value for our design. We believe that for the fire protection of gas-fired boiler rooms with emphasis on exposure protection and fire prevention, the design water spray intensity of

10.2l/min.m2

20.2l/min.m2

is more appropriate

another parameter is the action area. The water spray fire extinguishing system is a local application system, and the action area should be taken as the external surface size of the protected object. When the shape of the protected object is irregular, it should be determined according to the surface area of the smallest regular shape containing the object. In the design, it can be taken according to the overall dimensions provided by the product samples of gas-fired boilers

the action time of the system, especially when the design flow of the water spray fire extinguishing system is large, its value affects the water storage capacity of the water storage tank. The anti cooling objects in the "water mist regulations" are mainly the outdoor combustible gas production, transportation, loading and unloading, storage facilities, bottle filling room, bottle warehouse and other places, and the protection time is

6.0h

. The indoor machine room is different from the above places. When the quick disconnect valve is automatically closed, the source of fuel gas is cut off, and the whole fire extinguishing time will be shortened. It is impossible to press

6.0h

and the action time of the automatic spraying system is only

1.0h

. The extinguishing time of liquid and solid fires in the water mist code is

0.5h

1.0h

nfpa15

respectively. There is no specific system action time for the four fire fighting forms of fire extinguishing, fire control, exposure protection and fire prevention, but only functional requirements. We believe that according to the size of the system and the specific situation of the project, the design can be carried out in

0.5h

1.0h

Copyright © 2011 JIN SHI