RU2582473C1 - Method for total flooding of burning oil inside furnace for heating thereof with fire extinguishing agent and apparatus therefor - Google Patents

Abstract

FIELD: salvage operations.

SUBSTANCE: invention relates to firefighting equipment. Method of total burning oil inside furnace for heating includes consecutive steps of fire extinguishing, first stage to stop of burning oil and second stage to prevent repeated ignition of oil. At first stage of dilution mixture of steam and gas is introduced. Mixture is obtained from fuel combustion products, oxidizer, water is added, which is heated by these combustion products and overheated. At that, superheated water flow is mixed with supersonic flow of combustion products and fuel and oxidiser, thereby obtaining high-temperature gas. At second stage only water supply is continued for cooling furnace down to preset non-hypergolic oil temperature in it. For implementation of method used plant for total flooding of burning oil which contains storage container of fire-extinguishing substance 5, 6, 7, connected by pipelines 16 with furnace for oil heating, fire-extinguishing substance feed system 11, 12, 14, 15, 16, 17, control cabinet, shutoff valves 8, 9, 10, heat supply station for preparation of fire-extinguishing substance. Heat point of preparing fire-extinguishing substance is made in form of steam and gas generator 13, which is made in form of nozzle head 19. Inner cavity of head 19 is communicated with oxidizer feed system 14, 15 and fuel 1, 12, combustion chamber 18 with outer and inner jackets, between which is formed by heated channel cavity is connected to water supply system 16, 17 and cavity of steam and gas generator output device 13 made in form of de Laval nozzle. Nozzle outlet section is interconnected with inner cavity of furnace via mixer 25, at the output of which there is collector and which is equipped with nozzle device in form of annular slot for superheated water supply.

EFFECT: higher optimal protection of an object-consists in dissolving capacity of reacting substances concentration to limits at which combustion becomes impossible.

5 cl, 2 dwg

Description

The invention relates to fire fighting equipment and can be used to extinguish flammable oil products in confined spaces, or in particularly critical units, in particular for extinguishing burning oil inside a furnace to heat it.

The technological regulation provides for crude oil to be heated to a temperature of 200-250 ° C in furnaces for its heating before being launched into a distillation column for distillation, i.e. in aggregates of limited space.

Under operating conditions, leaked oil may leak inside the furnace due to burnout and the formation of cracks or fistulas on the surface of the heat exchanger tubes. The most dangerous accident may be a complete depressurization of the heat exchanger tubes, as a result of which a significant amount of oil can enter the interior of the furnace. The danger of explosion, cotton, and depressurization of the pipeline and oil spill is associated with the presence inside the furnace of the surface of the heat exchanger tubes and internal surfaces of the furnace structure heated above the temperature of auto-ignition of oil vapor.

In accordance with regulatory documents and technological regulations, the process of extinguishing burning oil inside the furnace to be heated with a fire extinguishing agent should be provided. Due to the fact that regulatory documents only determine the need to protect the facility with a fire extinguishing system, and the choice of equipment is carried out by the design organization taking into account the wishes of the customer, as a rule, the technical solution does not include equipment that provides optimal protection of the facility, but the equipment that has the lowest cost and appropriate quality. The optimal price / quality ratio of equipment.

By design, furnaces of this type are narrow-chamber furnaces with an upper flue gas outlet, a central horizontal screen and radiating walls from flameless panel burners. A heat exchanger is placed in the furnace, into which oil is supplied for heating. Fuel gas enters the panel burners, assembled in two walls located opposite each other, which provides two-sided irradiation of the heat exchanger, eliminating its overheating. The furnace includes a fire extinguishing agent supply device.

A known method of extinguishing a fire of flammable liquids, including the supply and atomization of a liquid freon, i.e. substances inhibiting chemical reactions of the combustion process and creating a non-combustible medium in a protected volume, preventing the re-ignition of flammable liquids [Baratov AN etc. Fire fighting at the enterprises of the chemical, petrochemical and oil refining industries. - M .: Chemistry, 1971, p. 363].

The known method is inferior in effectiveness to other methods with extinguishing agents, because About 5% of the mass of freon supplied to extinguish a fire undergoes thermal decomposition. Efficiency is determined by the design and technical operation of the installation in time, as well as the expended resources to extinguish the fire. The disadvantage of this method is that at high temperatures, the freons can decompose with the release of toxic substances, which is unsafe in the presence of people.

A known method of volumetric fire extinguishing of flammable liquids by introducing a fire extinguishing substance into the fire, including two stages of extinguishing a fire at the same time - dilution and cooling; soda water is used as a fire extinguishing agent. The decomposition of sparkling water in the fire leads to the release of CO ₂ from the water, while CO ₂ exhibits fire extinguishing properties, and H ₂ O enhances the cooling effect of heated surfaces [Auth. St. USSR No. 1806795, IPC A62C 3/06, publ. 04/07/1993].

The effectiveness of this method is inferior to another method with a fire extinguishing agent, because requires the creation of the necessary supply of CO ₂ and means of delivery to the extinguishing site of the required amount of CO ₂ , taking into account the expected standard water consumption. However, when using the known method for volumetric extinguishing of burning oil inside the furnace for its heating, it is necessary to take into account the complexity and high cost of servicing the equipment.

The closest in technical essence to the claimed technical solution and taken as a prototype is a known method of volumetric extinguishing of burning oil inside the furnace for heating it with a fire extinguishing agent, which is used liquid carbon dioxide, it is fed into the furnace for heating oil in stages, first at first stage - dilution stage - served until the oil is stopped burning, then with a time delay in the second stage - cooling stage - serves a second portion of liquid carbon dioxide to a reduced the temperature in the furnace for heating below the flash point of oil (Russian Patent No. 2225731, IPC A62C 3/06, publ. March 20, 2004).

A disadvantage of the known technical solution is the low fire extinguishing efficiency, which does not provide optimal protection of the object, because the cessation of combustion mechanism lies in its ability to dilute the concentration of reacting substances to the extent that combustion becomes impossible. The limit at which the fire extinguishing effect is realized is achieved if the concentration of carbon dioxide is at least 30% by volume, which leads to significant operational and fuel and energy resources, taking into account the complexity of equipment maintenance, which reduces the reliability of the method and overall efficiency.

The closest in technical essence and taken as a prototype to the claimed installation is an installation for implementing the method of volume quenching of burning oil inside the furnace for heating it with a fire extinguishing substance, containing storage tanks for fire extinguishing substance, pipelines for supplying a fire extinguishing substance to the furnace for heating oil, a heat point preparation of a fire extinguishing agent, which is made in the form of a stationary boiler room, a fire extinguishing agent supply system, a control cabinet, shutoff valves (Project Guide steam protection of technological furnaces at the enterprises of the oil refining and petrochemical industries. The instruction was approved by the Ministry of the oil refining and petrochemical industry and agreed with the Main Directorate of the State Fire Service of the USSR Ministry of Internal Affairs, 1976).

A disadvantage of the known installation of volumetric extinguishing of burning oil inside the furnace for its heating is the high energy costs and high cost of maintenance of the boiler room for fire fighting, associated with the need to keep the boiler in constant year-round availability, which reduces reliability and efficiency in general.

The object of the invention is the creation of an effective method and installation for extinguishing burning oil inside a furnace for heating oil while reducing operating costs and fuel and energy resources.

The technical result, the proposed solution is aimed at, is to create a highly effective, simple and reliable method of volumetric fire extinguishing with a fire extinguishing agent in the form of a mixture of steam and gas and a unit for its implementation with a small mixing interval of gas and steam.

The technical result is achieved by the fact that in the method of volume quenching of burning oil inside the furnace for heating it with a fire extinguishing agent, including successive stages of extinguishing - the first stage of dilution, stopping the burning of oil and the second stage of cooling, preventing re-ignition of oil, the preparation of extinguishing agent is carried out at the first stage of dilution and steam gas is introduced as a fire extinguishing agent - a mixture of steam and gas, which is obtained from the products of combustion of a fuel, an oxidizing agent, water is introduced, which I heat t with these products of combustion and overheat it, while the stream of superheated water is mixed with the supersonic stream of products of combustion of fuel and oxidizer, thus obtaining a high-temperature gas, and then in the second stage they continue to supply only water to cool the furnace to a predetermined temperature of non-self-ignition of oil in it.

Associated petroleum gas is used as fuel, and air is used as an oxidizing agent in amounts of at least a stoichiometric ratio.

Water is fed into the furnace in the form of fog to increase the rate of heat dissipation.

The technical result is achieved by the fact that in the installation for volumetric extinguishing of burning oil inside the furnace for heating it with a fire extinguishing agent, containing storage tanks for the fire extinguishing agent, connected by pipelines to the furnace for heating the oil, the fire extinguisher supply system, a control cabinet, shutoff valves, a fire extinguisher preparation center substances, the heat extinguishing agent preparation point, consisting of a mixture of steam and gas, is made in the form of a gas generator connected to the oxidizer supply system, combustible water and steam, while the steam and gas generator is made in the form of a nozzle head, the internal cavity of which is in communication with the oxidizer and fuel supply system, a combustion chamber with external and internal jackets, between which a heated channel is formed, the cavity of which is in communication with the water supply system and with the cavity of the output device a steam-gas generator made in the form of a Laval nozzle, the outlet cross section of which is communicated with the internal cavity of the furnace for heating oil, through a mixing device at the outlet of which a collector is located which is equipped with a nozzle device in the form of an annular gap for supplying superheated water and is located in the expanding part of the Laval nozzle, in its smallest section, behind it, for supplying high-temperature gas from the combustion chamber in the form of oxidant combustion products, fuel and mixing of superheated water flows with a supersonic flow high-temperature gas with the possibility of obtaining a fire extinguishing agent.

The installation is equipped with an additional circuit with a cold water supply system, which is made on the outer jacket of the expanding section of the Laval nozzle, the inner cavity of which is connected to the water supply system through a pipeline with shut-off valves, while at the outlet of the collector there are tangential openings by which it communicates with the internal cavity of the nozzle ring type devices for mechanical spraying.

The cooling ability is characterized by the specific heat of liquid carbon dioxide, which is C = 846 J / kg · K. 509 liters of gas are obtained from 1 liter of liquid carbon dioxide. Liquid carbon dioxide is inferior in terms of physical and technical characteristics to a fire extinguishing agent, in which water vapor can be used, in which the specific heat of water is C = 4187 J / kg · K, and when 1 l of water is evaporated, 1700 l of steam is formed , which also increases the efficiency of the method of volume quenching of burning oil inside the furnace for heating it.

To clarify the technical nature, consider the drawings.

In FIG. 1 shows a plant for implementing the method of volume quenching of burning oil inside the furnace for heating it with a fire extinguishing agent, which prepares in the first stage of dilution as a fire extinguishing agent a high-temperature vapor-gas stream for feeding into the furnace.

In FIG. 2 shows the installation for implementing the method of volume quenching of burning oil inside the furnace for heating it with a fire extinguishing agent, which completes the quenching by the second stage - the cooling stage, where:

1 - oven; 2 - heat exchanger; 3 - flameless burners; 4 - exhaust chimney; 5 - fuel capacity; 6 - oxidizer capacity; 7 - water capacity; 8, 9, 10 - shutoff valves; 11 - fuel supply pipe; 12 - compressor of the fuel supply system; 13 - heat point in the form of a steam and gas generator; 14 - oxidizer supply pipe; 15 - oxidizer feed system compressor; 16 - water supply pipeline; 17 - pump water supply system; 18 - combustion chamber; 19 - nozzle head; 20 - output nozzle in the form of a Laval nozzle; 21 - inner shirt; 22 - outer shirt; 23 - ignition device; 24 - shut-off valve; 25 - mixing device, 26 - automation elements; 27 - an additional circuit; 28 - pipeline additional circuit; 29 - shutoff valves of the additional circuit; 30 - collector; 31 - tangential holes; 32 - regulatory authority.

A heat exchanger 2 is installed inside the furnace 1, through which oil is pumped. To heat the oil in the heat exchanger 2, flameless burners 3 are installed, which are located in the side walls of the furnace 1 to irradiate the largest surface of the heat exchanger 2. The products of combustion of flameless burners 3 are released into the atmosphere through an exhaust chimney 4. The drawing shows a fragment of furnace 1. In the event of an emergency the installed thermal fire detector is triggered, which gives a fire signal depending on the change in electrical resistance with increasing temperature. The controls are located in the control cabinet, which is not shown in the drawing. The extinguishing agent consists of fuel, oxidizing agent and water, which are placed in containers 5, 6, 7 for fuel, oxidizing agent and water, respectively. Tanks 5, 6, 7 respectively contain shutoff valves 8, 9, 10, which are placed on the pipelines. The fuel supply pipe 11 connects the fuel tank 5 to the furnace 1 through the fuel supply system in the form of a compressor 12 and the heat point 13. The heat point 13 is fixed to the furnace body 1. The oxidizer supply pipe 14 connects the oxidizer tank 6 to the furnace 1 through the oxidizer supply system in the form a compressor 15 and a heat point 13. A water supply pipe 16 to a heat point 13 connects a water tank 7 to the furnace 1 through a water supply system in the form of a pump 17 and a heat point 13.

Thermal point 13 is designed to prepare a fire extinguishing agent to receive a signal from a fire detector. It is made in the form of a steam and gas generator, which consists of a combustion chamber 18, a nozzle head 19 and an output nozzle 20 in the form of a Laval nozzle. The combustion chamber 18 is made of an inner jacket 21 and an outer jacket 22, between which a heated channel is formed, the cavity of which is in communication with the water supply system in the form of a pump 17.

The nozzle head 19, the inner cavity of which is connected to the fuel supply system in the form of a compressor 12, the oxidizer supply system in the form of a compressor 15 and a combustion chamber with the outer 22 and the inner jacket 21, between which a heated channel is formed, the cavity of which is in communication with the water supply system and cavity of the output device, made in the form of a Laval nozzle 20, the output cross section of which is communicated with the internal cavity of the furnace 1 for heating oil, through a mixing device 25, at the outlet of which a collector 30 is located and The second one is equipped with a nozzle device in the form of an annular gap for supplying superheated water and is located in the expanding part of the Laval nozzle, in its smallest section, behind it, for supplying high-temperature gas from the combustion chamber 18 in the form of oxidant combustion products, fuel and mixing of superheated water flows with supersonic a stream of high temperature gas with the possibility of obtaining a fire extinguishing agent. An ignition device 23 is installed in the combustion chamber 18 for igniting the components of the oxidizer and fuel. A shut-off valve 24 is installed in the fuel supply system. In an emergency, the automation elements 26 cut off the oil supply to the furnace 1 through the heat exchanger 2.

The installation is equipped with an additional cold water supply circuit 27 (Fig. 2) to the expanding part of the channel of the Laval nozzle of the steam and gas generator 13. The additional circuit contains a pipe 28 and shutoff valves 29 connecting the water supply system to the collector 30, on the inner surface of which tangential openings 31 are made for mechanical spraying using centrifugal effect. The additional circuit 27 contains a regulatory body 32.

Installation works as follows. The technological procedure provides for crude oil to be heated to a temperature of 200-250 ° C in the furnace 1 before being introduced into the distillation column for distillation by heat transfer when pumping it through a heat exchanger 2. Heating is carried out by flameless burners 3. The products of combustion of flameless burners 3 from furnace 1 are removed through a flue exhaust pipe 4 to the atmosphere. The technological regulation provides for fire prevention measures. In the initial state, containers with extinguishing agent, which consists of components, are filled. The composition of the extinguishing agent includes fuel, an oxidizing agent and water. They are placed in the right amount in containers 5, 6, 7, respectively. Associated petroleum gas, for example, can be used as fuel, and air as an oxidizing agent. In the initial position, the locking device 5, 6, 7, respectively, of fuel, oxidizer and water are closed. Furnace 1 is operating, and the installation for volumetric extinguishing of burning oil inside the furnace for its heating does not work, is in standby mode.

As a result of long-term operation of the furnace 1, depressurization of the heat exchanger 2 occurs and ignition of light oil fractions occurs. There is a fire in a confined space, i.e. in furnace 1, accompanied by an increase in temperature to a temperature of 1000-1300 ° C. The elements of automation 26, as a result of an increase in temperature, are triggered and a thermal fire detector gives a fire signal.

Automation elements 26 (operator) signal the opening of shut-off devices 8, 9, 10. Fuel supply systems 12, 15, 17 of fuel, oxidizer and water respectively provide access of these components to the combustion chamber 18 of the steam and gas generator 13. The ignition device 23 provides ignition of the oxidizer and fuel in the combustion chamber 18. The combustion products contain, at a stoichiometric ratio of oxidizing agent and fuel, approximately, H ₂ O - 15.2%, N ₂ - 73.8%, CO ₂ - 8.4%, H ₂ - 0.24%, O ₂ - 0.34%, OH - 0.21%, CO - 0.73%, NO - 0.17% and practically traces of other components. The labile particles in the composition of the combustion products in the combustion chamber 18 are the result of the dissociation process due to the high temperature of ~ 2230 K at a pressure of 0.6 MPa. With the expansion of the high-temperature gas in the Laval nozzle 20, in the flow of combustion products, in the smallest section, its temperature decreases to ~ 1850 K, reaching a gas flow velocity equal to a = 890 m / s, while the composition of the combustion products changes as a result of the recombination process, only stable particles of H ₂ O, N ₂ , CO ₂ remain in the composition.

Water through a pipe 16 is supplied under pressure by a pump 17 of the water supply system to the heating channel and heated. The pressure of the water supply varies depending on the fire conditions from 0.2-1.2 MPa. Water is heated in the combustion chamber to a temperature exceeding the boiling point at normal atmospheric pressure equal to ~ 120-180 ° C. The amount of water heating is selected depending on the required size of the droplets during spraying. The diameter of the droplets is obtained from 100 μm to 25 μm or less by changing the heating temperature. The evaporation rate of a drop depends on its size. In the tapering part of the Laval nozzle, the cooling surface of the inner wall decreases, when the passage section of the channel decreases, the flow of heated water increases the speed, while the pressure of the water in the stream decreases, receiving water in an overheated state. In the smallest section of the Laval nozzle 20, in the zone of supercritical pressure difference, the high-temperature gas flow of the products of combustion of fuel and oxidizer reaches the speed of sound, isolating the operation of the combustion chamber from external factors. A high-temperature gas stream of combustion products at a speed higher than the speed of sound mixes with water in an overheated state, while the water instantly goes into an overheated state, boils throughout the volume and the resulting vapor breaks the stream, reducing the mixing interval.

Thus, a fire extinguishing agent formed from steam gas, i.e. a mixture of steam and gas, consisting of products of combustion of fuel and oxidizer and water, enters the furnace 1.

Depending on the nature of the fire in the furnace (emergency), it is possible to supply cold water through an additional circuit 27 in the form of a collector in the active phase of extinguishing burning oil with the possibility of redistributing the amount of supply of heated and cold water.

An extinguishing agent flame containing steam and a high-temperature gas containing components of stable particles (neutral particles) of H ₂ O, Ν ₂ , CO ₂ , enters furnace 1 from the Laval nozzle 20. The extinguishing effect of steam gas, which is an ideal heat carrier, provides not only air displacement the furnace 1 (for interrupting the combustion process in the furnace), but also neutral components of the extinguishing action of H ₂ O, N _2, CO ₂ dilutes the combustion products of the burning oil stable neutral particles, performing the role of the third particle in the chain mechanism x nomic transformations burning oil, preventing the chain branching reactions. The standard for extinguishing a furnace with a volume of 500 m ³ by steam alone is 3 minutes. The rate of extinguishing with steam gas such volumes will be less.

Upon completion of the first stage of dilution of the products of oil combustion with a fire extinguishing agent, oil combustion ceases, but surfaces of technological apparatuses heated to a high temperature in the furnace remain a potential source of reignition of oil in the furnace.

To implement the second stage of quenching cooling, the flow of oxidant and fuel to the steam and gas generator 13 is turned off by closing the shut-off devices 8, 9.

The process is carried out by cooling, including the incoming extinguishing agent in the form of steam and gas, by supplying cold water in the form of fog, i.e. fine water flow. A finely dispersed water stream is formed by mechanical spraying as a result of a water pressure difference in the flow channel of the steam and gas generator channel downstream in the zone of the smallest section of the Laval nozzle 20. A finely dispersed water stream forms in furnace 1 a large-scale turbulent flow of the extinguishing agent and combustion products of burning oil by shifting the flow relative to the axis furnaces for cooling structural elements. When the temperature in the furnace reaches T = 500-800 ° C, the condensation process begins to occur in the volume of the vapor-gas mixture due to contact with a cold finely dispersed medium, the smaller the diameter of the droplets in the misty mode of water inlet, the greater the absorbency of the droplets, the higher the cooling effect with a droplet diameter of 1-5 mm, the more intense the process of moisture condensation in the volume introduced into the furnace during the active phase of extinguishing the fire. The process of moisture condensation in the volume introduced into the furnace is carried out during the active phase of extinguishing the fire. To implement drip irrigation and cooling to a temperature below the flash point of the oil, reducing mainly the thermal capacity of the structural elements of the furnace itself, by evaporating moisture droplets on its surface, using the high heat capacity of water C = 4187 J / kg · K, preventing the reignition process , completing the general process of extinguishing burning oil with a minimum amount of water supply.

The installation can be used to extinguish a fire in several furnaces for heating oil. In this case, the installation is supplemented by distribution devices for the number of furnaces installed between the oil heating furnaces and the locking and starting devices.

Thus, the proposed method and installation for volumetric extinguishing of burning oil inside the furnace for heating it in comparison with known analogues allows to obtain a highly efficient, simple and reliable method of volumetric extinguishing of burning oil inside the furnace for heating it with a fire extinguishing agent and installation for its implementation due to dilution at the first stages, preparing the extinguishing agent in the form of a gas mixture, which are obtained from the products of combustion of fuel, an oxidizing agent and introduce water, heating it with these products and overheating it, thus obtaining a high-temperature gas, at a speed higher than the speed of sound, while the water instantly passes into an overheated state, boils throughout the volume and the resulting vapor breaks the stream, forming a torch of extinguishing agent, consisting of steam and high-temperature gas, containing components of stable particles by diluting the concentration of the reacting substances to the extent that combustion becomes impossible, and from the Laval nozzle enters the furnace, and in the second stage only ode for cooling the furnace to a predetermined temperature Nonincendive oil therein.

Claims (5)

1. The method of volume quenching of burning oil inside the furnace for heating it with a fire extinguishing agent, comprising successive stages of extinguishing - the first stage of dilution, stopping the burning of oil and the second stage of cooling, preventing re-ignition of oil, characterized in that the preparation of extinguishing agent is carried out at the first stage of dilution and steam gas is introduced as an extinguishing agent - a mixture of steam and gas, which is obtained from the products of combustion of a fuel, an oxidizing agent, water is introduced, which is heated by these products anija and superheated it is mixed with the superheated water flow from the supersonic flow of combustion products of fuel and oxidant, while receiving a high-temperature gas, and then in the second stage only continue feeding water for cooling the furnace to a predetermined temperature nesamovosplameneniya oil therein. 2. The method according to p. 1, characterized in that the associated petroleum gas is used as the fuel, and air is used as the oxidizing agent in quantities of at least a stoichiometric ratio. 3. The method according to p. 1, characterized in that the water is supplied to the furnace in the form of fog to increase the rate of heat dissipation. 4. Installation for volumetric extinguishing of burning oil inside the furnace for heating it with a fire extinguishing agent, containing storage tanks for fire extinguishing agent, connected by pipelines to the furnace for heating oil, a fire extinguishing agent supply system, a control cabinet, shut-off valves, a fire extinguishing agent preparation point, characterized in that the heat treatment point for the preparation of the extinguishing agent, consisting of a mixture of steam and gas, is made in the form of a steam and gas generator connected to an oxidizer, fuel and water supply system, while the gas generator is made in the form of a nozzle head, the internal cavity of which is in communication with the oxidizer and fuel supply system, the combustion chamber with the external and internal jackets, between which a heated channel is formed, the cavity of which is in communication with the water supply system and with the cavity of the gas and gas generator output device, made in the form of a nozzle Laval, the outlet cross section of which is connected with the internal cavity of the furnace for heating oil, through a mixing device at the outlet of which a collector is located and which is equipped with with a bed device in the form of an annular gap for supplying superheated water and located in the expanding part of the Laval nozzle, in its smallest section, behind it, for supplying high-temperature gas from the combustion chamber in the form of oxidant combustion products, fuel and mixing of superheated water flows with a supersonic flow of high-temperature gas with the possibility of obtaining a fire extinguishing agent. 5. Installation according to claim 4, characterized in that it is provided with an additional circuit with a cold water supply system, which is made on the outer shirt of the expanding section of the Laval nozzle, the inner cavity of which is connected to the water supply system through a pipeline with shutoff valves, while at the outlet the collector has tangential openings by which it communicates with the inner cavity of the annular nozzle device for mechanical spraying.

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