Design of fire fighting system for the hottest lar

2022-10-20
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Design of fire protection system for large paperboard machine

key words: paper machine fire protection; Fire compartment; Bearing; High temperature detector; Water spray system

Rizhao

Rizhao Senbo pulp and Paper Co., Ltd. is a large-scale enterprise that was pilot produced in April 2002. The total investment of the first phase of the project is 2.82 billion yuan, which is a key construction project of the ninth five year plan. The company uses wood chips as raw materials to produce high-end commodity bleached wood pulp and high-end packaging paper. The annual production capacity of the paperboard machine is 150000 tons. The structure of the drying cylinder is shown in Figure 1. The drying cylinder is divided into upper and lower layers, with a total of 94

1 design scheme

Figure 1 fire compartment and sprinkler installation diagram

the production environment of Rizhao cardboard workshop mainly has three characteristics: first, the working temperature is high, the inlet air temperature in the drying hood is higher than 100 ℃, the outlet air temperature is about 65 ℃, and the average temperature is stable at 85 ~ 90 ℃; Second, the air humidity is high, and the air humidity of the pre drying part almost reaches saturation; Third, the space volume is large, the horizontal distance from the inlet to the outlet of the paper web is 102m, and the total amount of up and down penetration is 15000m3

1.1 determination of the form of fire extinguishing system

due to the large space, large volume and ventilation and dispersion facilities in the cover, only the water spray fire extinguishing system with the appropriate fire extinguishing principle can be selected in this special environment. When the water mist contacts the surface of the combustor, it will be atomized into water vapor after being heated. During this transformation process, the heat energy on the surface of the combustor will be lost a lot, and its cooling effect is better than that of dense water flow; The second is its suffocation and fire extinguishing effect. The water mist and the water vapor transformed by it cover the surrounding of the combustion body, which can effectively prevent air replenishment, so that the combustion of combustibles is interrupted due to insufficient oxygen; Third, its electrical insulation performance is good

1.2 fire detection and alarm linkage control mode

the excessive humidity and hot gas convection in the sunshine drying hood will inevitably passivate or damage the detector. Due to the particularity of the environment, only the temperature sensing detection system can be selected, and the detector must have a standard temperature of about 200 ℃, and must also have the performance of automatic recovery and continuous use. The calibration temperature of wmx3111fs ultra-high temperature detector of German meilima company is 80 ~ 500 ℃, and the alarm temperature is not only adjustable, but also can set one temperature as the early warning temperature value (such as 115 ℃), and the other temperature as the fire alarm temperature (such as 135 ℃), that is, the detector itself has the ability of double threshold to confirm the fire. The probe rod installation form of the detector is very consistent with the working environment such as the drying hood, and there are a large number of successful examples in similar projects abroad

in order to ensure the continuity of production, the reliability and stability of the alarm linkage system is particularly important. In order to prevent misoperation, the temperature sensing detection and alarm linkage control system adopts the products of German meilima company; According to the existing fire prevention code requirements in China, the state display panel and pump control panel produced by the state-owned 262 factory are selected to jointly complete the signal acquisition, confirmation and linkage signal sending control functions

2 division of fire prevention zones

sunshine according to the specification for water spray, the water spray intensity of the water spray fire extinguishing system shall not be less than 15L/min · m2. According to years of practice and the performance of deluge equipment products, it is best to choose an alarm deluge valve not greater than DN150, which has reliable performance, and the partition protection area is best controlled within 200m2. The drying hood is limited to the requirements of the production process, which is a large space through, and it is not allowed to physically separate according to the fire-proof area. The drying hood and the lower layer of the paper machine can only be artificially divided into A1, A2, A3... A9 and B1, B2, B3... B9, a total of 18 virtual fire zones, each zone has an area of about 150m2, and the pipelines and alarm valves in each zone are covered independently. The advantages of this division of fire zones are:

sunshine (1) the area of the zone is small, which is conducive to accurate and effective linkage control, reducing misoperation and the impact on paper machine equipment in non fire areas

sunshine welder hammer (2) is flexible, and the design water required for each partition is small, reducing the cost of system pipelines and deluge equipment

such phenomenon as sunshine is called yielding (3) the paper machine drives faster (500 ~ 600m/min). If a fire occurs, the paper web will carry the fire to ignite the adjacent area of the next process, which will also realize the opening linkage of the deluge valve in this area through the alarm system. That is, the water output of the main fire pump increases in series, and the change process of flow from small to large makes the electric load of the main pump start small, the initial operation input power is low, the equipment is safe, and the start is reliable

3 installation and type selection of main fire-fighting equipment

3.1 spray nozzles

sunshine arranges medium speed water mist nozzles in the upper and lower areas according to the specifications (k=28, α= 180 ℃) to protect the paper machine and its foundation. It is far from the purpose of protecting the paper machine equipment to arrange nozzles only on the upper vertical plane of the protection area. Therefore, special water mist nozzles must be set at important parts of the paper machine equipment

the bearing of the sunshine dryer is an important rotating part of the paper machine. There is a precedent of fire caused by high temperature due to bearing damage. Therefore, when the corresponding difference between the upper and lower bearings is set outside the range of ± 2, the hardness tester must be revised and repaired or replaced with a special water spray nozzle (k=40) measured by other hardness testing methods, and the friction coefficient of the material can be measured α= 90 ℃), the bearing can be cooled in case of fire

3.2 deluge valve

there are 18 sunshine, which correspond to each partition and are set independently. It has stable performance and complete functions. It should have obvious opening and closing signs and corresponding monitoring signal output to prevent misoperation by non professionals

3.3 main fire pump

sunshine

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