RU2320385C2 - Method and device for oil product tank protection against fire - Google Patents

Abstract

FIELD: fire-fighting, particularly to extinguish inflammable liquids, for instance oil or petroleum products in storage tanks.

SUBSTANCE: method involves delivering additional generators installed on floating platform from tank bottom after fire detection. Said method provides intensive homogenous-heterogeneous burning process inhibiting directly inside flame over burning liquid surface by delivering necessary amount of fire-extinguishing substance thereto. After additional generator operation termination the platform is thermally decomposed under the action of increased temperature in platform location area. To suppress small fire sites fire-extinguishing substance is supplied from generators fixed to tank bottom. Aerosol bubbles through liquid, cools down and accumulates inside flame over small burning liquid sites to suppress re-ignition thereof.

EFFECT: increased fire-extinguishing completeness and efficiency.

2 cl, 3 dwg

Description

The invention relates to methods for extinguishing flammable liquids, such as oil or gasoline, stored in tank farms.

It is known that fires in tanks with light oil products usually begin with the explosion of the vapor-air mixture in the gas space of the tank and the roof falling off or with the burning of the steam-air mixture in the gas space of the tank without breaking the roof, but with its integrity breaking in some of the weakest places.

The strength of the explosion affects the nature of the subsequent development of the fire. Depending on this, various destruction of tank structures is observed.

Light oil products burn (gasoline, naphtha, kerosene, benzene, etc.) more intensively on the free surface than dark oil products, and the height of the flame reaches 20-40 m, and when boiling pre-refined oil and dark products of its processing the flame reaches 70-80 m. Burning oil (when ejected) can soar to a height of 80 m and spray downwind to a distance of 150 m.

Fires in reservoirs with petroleum products are extinguished, as a rule, by the foam supplied to the combustion chamber by stationary foam chambers or mobile foam lifters (E.N. Ivanov. Fire protection of open technological installations. 2nd edition revised and supplemented. M., Chemistry, 1986, p. .195-196).

However, in the event of an abnormal development of the fire, complete extinguishing by the foam of flammable flammable liquids in tank farms occurs only after a few hours, and sometimes a day, since the fire extinguishing ability of the foam is lost when it is fed into the high temperature zone formed near the foam chamber (A.N. Baratov, E.N. Ivanov, Fire-fighting at the enterprises of the chemical and oil-refining industries, 2nd revised edition, M. Chemistry, 1979, p. 262). Therefore, the recommendations (Extinguishing fires of oil and oil products in tanks: Recommendations. - M .: VNIIPO, 1991) suggest stopping the flow of foam if the combustion is not eliminated within 30 minutes. As an example, we can point to a fire on the ground-mounted steel reservoir of the RVS with a fixed roof and a pontoon at the Moscow oil refinery, which could not be extinguished within 24 hours when more than 100 fire engines were concentrated (AN Baratov. Combustion - Fire - Explosion - Safety M., FGU VNIIPO EMERCOM of Russia, 2003, p.332).

The experience of extinguishing oil product fires in metal tanks shows that stationary foam chambers often fail as a result of an explosion or deformation of the tank’s upper belt before extinguishing and do not give the required effect during operation (E.N. Ivanov. Fire protection of open technological installations. Edition 2nd revised and supplemented. M., Chemistry, 1986, p.202).

A known method of fire protection of tanks with petroleum products, adopted as a prototype (patent of the Russian Federation No. 2090227, IPC A62C 2/00, publ. 09/20/97, Bull. No. 26), which consists in placing the generators on the bottom or on the pallet, or outside the tank. The aerosol formed during the operation of the generator sparges through the liquid, cools and then concentrates inside the torch above the surface of the burning liquid, as a result of which the main focus of the fire is extinguished.

However, as you know, in the combustion zone of oil products a temperature develops up to 1100-1200 ° C, and the amount of energy released during the combustion of oil products is such that the walls above the liquid level lose their strength and begin to deform (E. Ivanov. Fire protection of open technological installations . 2nd edition revised and supplemented. M., Chemistry, 1986, p.196).

All this suggests that the cooled aerosol, which is a gas extinguishing agent, will have practically no significant cooling effect on the surface of the burning liquid and on the combustion torch, since the agent itself has a low heat capacity.

In addition, the specified method of fire protection of reservoirs with oil products does not provide for the elimination, if necessary, of the observed small foci of burning (E.N. Ivanov. Fire protection of open process plants. 2nd edition revised and supplemented. M., Chemistry, 1986, p.207 )

It should also be noted that when igniting aerosol generators located directly in the oil product with the help of an electric pulse, some charges in the liquid medium can be extinguished at the initial moment of their ignition, and due to the high temperature of the aerosol, part of the oil product may deteriorate as a result of the pyrolysis of the latter (A. N. Baratov. Combustion - Fire - Explosion - Safety. M., FGU VNIIPO EMERCOM of Russia, 2003, p.333).

The proposed method of extinguishing the combustion of petroleum products in tanks can increase the efficiency of fire fighting.

To do this, in the method of fire protection of reservoirs with oil products, which consists in permanently placing fire extinguishing medium generators on the tank bottom, supplying, after detecting a fire, a fire extinguisher generated when the generators are activated and then concentrating it inside the torch above the surface of the burning liquid, on a floating platform fixed to the bottom of the tank place additional generators, while after detecting a fire, the platform is ascended and the extinguishing agent is supplied and additional generators, and feed means of extinguishing generators bottom of the tank is carried out after activation of additional generators.

The essence of the proposed device lies in the fact that in the device for the fire protection of reservoirs with oil products, containing fire extinguishing means generators located stationary at the bottom of the tank, the ignition detection and start-up systems, it contains a floating platform with additional generators placed on it, kept flooded by a flexible a bond fixed to the bottom of the tank, while the platform is made of thermally easily destructible substances, for example, foam.

Delivery after detection of ignition on a floating platform of additional generators makes it possible to carry out intensively combined homogeneous heterogeneous inhibition of the combustion process directly inside the flame above the surface of the burning liquid by delivering the required amount of extinguishing agent without preliminary cooling, which ultimately leads to the complete extinguishing of the main fire. Moreover, the platform, made of thermally easily destructible material, for example, foam, after the development of additional generators is thermally decomposed, since the temperature in the zone of location of this platform remains for some time quite high. This allows you to freely perform further extinguishing of small foci of combustion.

The supply of a fire extinguishing agent from stationary generators located at the bottom of the tank after the triggering of additional generators allows it to be directed only to extinguishing small foci of combustion, which improves the extinguishing reliability. As a result, it is possible to significantly reduce the amount of extinguishing agent supplied from the bottom of the tank, which will significantly reduce the negative effect of pyrolysis.

At the same time, as noted earlier, the effectiveness of the action of the cooled fire extinguishing agent is compensated by the intensification of the process of inhibition (inhibition) of the rate of chemical reactions in the flame when the uncooled fire extinguishing agent is supplied from additional generators to the high-temperature combustion zone.

The flooded placement of the floating platform at the bottom of the tank using a flexible connection allows you to not have a significant impact on the process of storing petroleum products in tanks.

Figure 1 shows a General view of a device that implements the inventive method (in standby mode), figure 2 - the same, in case of fire after surfacing the platform and at the time of supply of the extinguishing agent from additional generators, figure 3 - the same, after supply of extinguishing agent from additional generators at the time of extinguishing agent from the generators at the bottom of the tank when extinguishing small foci of combustion.

The device (Figure 1) consists of a pallet 1 located at the bottom of the tank 2, filled with petroleum products. On the pallet 1, generators 3 are installed uniformly in area, in which a fire extinguishing agent is enclosed.

Above the pallet 1, at a certain distance from it, there is a floating platform 4 made, for example, of foam and held in a flooded state by flexible coupling 5. On the platform 4, additional generators 6 are installed uniformly in its area, in which a fire extinguishing agent is enclosed. A fire detector 7 is mounted above the tank 2, which is connected to the control unit 8 of the launch system 9 of the generators 3 and 6.

The device operates as follows. In case of fire in the tank 2, intense combustion occurs on the surface of petroleum products (figure 2). After detecting a fire by a fire detector 7, the signal from the latter enters the control unit 8, which through the start system 9 gives the commands in the following sequence.

First, flexible connection 5 is released, then platform 4 is ascended. After the named platform is ascended, additional generators 6 are launched. As a result, directly inside the torch 10 above the surface of the burning liquid, an intensive combined homogeneous heterogeneous inhibition of the combustion process is carried out by delivering the required amount of extinguishing agent without prior cooling, which leads, ultimately, to completely extinguish the main focus of the fire.

After testing the generators 6, platform 4 thermally decomposes, since the temperature in the zone of location of this platform remains for some time quite high. At this time, it is possible, as noted earlier, the occurrence of small foci of combustion 11. To eliminate these foci of combustion, the generators 3 are launched at the bottom of the tank 2 and the required amount of extinguishing agent is supplied from them (Figure 3). In this case, the aerosol sparges through the liquid, cools, and then concentrates inside the torch above the surface of small foci of burning liquid. As a result, quenching of the reignition centers occurs.

Claims (2)

1. The method of fire protection of reservoirs with petroleum products, which consists in permanently placing fire extinguisher generators on the tank bottom, supplying, after detecting a fire, a fire extinguisher generated when the generators are activated and then concentrating it inside the torch above the surface of the burning liquid, characterized in that on a floating platform fixed additional generators are placed at the bottom of the tank, while after detecting a fire, the platform is floated and a fire extinguisher is supplied funds from additional generators, and the supply of extinguishing media from generators at the bottom of the tank is carried out after the operation of additional generators. 2. A device for the fire protection of reservoirs with petroleum products, containing fire extinguisher generators located stationary at the bottom of the tank, a system for detecting ignition and starting up generators, characterized in that the device comprises a floating platform with additional generators placed on it, held in a flooded state by a flexible connection, fixed at the bottom of the tank, while the platform is made of thermally easily destructible substances, for example, foam.

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