Real-time continuous preparation method of solid water fire extinguishing agent

Abstract

The invention discloses a real-time preparation method of a solid water fire extinguishing agent. According to the method, through a fluidized bed technology, compressed gas is used for driving hydrophobic nano silicon dioxide to be fluidized in a fluidized bed, meanwhile, an aqueous solution containing fire extinguishing active ingredients is atomized, a core-shell structure is formed through the gas-solid turbulence effect, and the solid water fire extinguishing agent is prepared after dehydration. The preparation method can realize on-site instant preparation, can avoid the problem of traditional storage failure, is suitable for fire fighting of lithium ion batteries and the like, and has the characteristics of high fire extinguishing efficiency and after-combustion prevention.

Description

Technical Field

[0001] The invention belongs to the technical field of fire protection products, and in particular relates to a real-time continuous preparation method of a solid water fire extinguishing agent. Background Art

[0002] With the widespread adoption of lithium-ion batteries in electric vehicles, energy storage power stations, and other fields, fires caused by thermal runaway have become increasingly frequent. Lithium-ion battery fires, involving the decomposition of electrode materials, electrolyte combustion, and internal exothermic chain reactions, present complex characteristics such as rapid fire spread, high combustion temperatures, and a significant risk of re-ignition. Residual heat within the battery cells can easily trigger secondary combustion after extinguishing a fire, posing a significant challenge to firefighting and rescue efforts. Therefore, cooling and controlling the internal reactions of lithium-ion batteries is crucial for effectively extinguishing lithium-ion battery fires. Currently, the fire extinguishing agents receiving widespread attention are primarily gas-water-based fire extinguishing agents. However, their inherent electrical conductivity can cause short circuits between the positive and negative electrodes of the battery, intensifying electrochemical reactions and releasing secondary energy. Solid-water fire extinguishing agents, as a stable system consisting of aqueous droplets encapsulated in a hydrophobic carrier, combine the efficient heat absorption of liquid water with the insulating properties of a solid carrier. However, existing solid-water fire extinguishing agent preparation technologies present challenges in firefighting scenarios, such as poor core-shell structure stability and high storage and transportation costs. Therefore, developing a method for real-time and stable preparation of solid water fire extinguishing agents has become the key to breaking through the bottleneck of efficient fire extinguishing and safety prevention and control technology for lithium-ion battery fires. Summary of the Invention

[0003] In order to solve the above problems, the object of the present invention is to provide a real-time continuous preparation method of solid water fire extinguishing agent.

[0004] In order to achieve the above object, the present invention provides a real-time continuous preparation method of a solid water fire extinguishing agent, comprising the following steps performed in sequence:

[0005] S1. Feeding hydrophobic nano-silica into a fluidized bed reactor through an airtight conveying system, and controlling the feeding rate through a high-pressure pneumatic valve to ensure that the hydrophobic nano-silica is evenly distributed in the bed;

[0006] S2, introducing compressed gas into the bottom of the fluidized bed reactor as a power source, forming a stable vertical gas column through the gas distributor, so that the hydrophobic nano-silica forms a high-intensity turbulent field in the fluidized bed reactor;

[0007] S3, injecting an aqueous solution containing a fire extinguishing active ingredient into an ultrasonic atomizer, atomizing it into micron-sized droplets through a resonant cavity, and spraying it into the reaction zone of a fluidized bed reactor through a nozzle;

[0008] S4. In the gas-solid turbulent flow field, the hydrophobic nano-silica collides with the droplets. Through the combined action of capillary adsorption and van der Waals forces, the hydrophobic nano-silica wraps the droplets to form a core-shell structure with a hydrophobic shell.

[0009] S5. After being output from the separator, the unwrapped free water is removed through the dehydration device simultaneously, and finally a solid water fire extinguishing agent is produced.

[0010] The aqueous solution containing the fire extinguishing active ingredient is selected from at least one of an aqueous solution of ammonium dihydrogen phosphate, an aqueous solution of ammonium polyphosphate and an aqueous solution of ammonium bromide.

[0011] The particle size of the hydrophobic nano-silicon dioxide is 7-40 nm, and the SiO2 content is ≥99.8%.

[0012] The fluidized bed reactor is a spouted fluidized bed reactor, and the flow rate of the compressed gas is 1.8-5 m / s.

[0013] The ultrasonic atomizer adopts a piezoelectric ultrasonic atomizer, the atomization frequency is 1.0-1.5 MHz, and the CV value of the droplet particle size is less than 15%.

[0014] The spraying speed of the nozzle is 20-50 m / s, and the spraying direction forms an angle of 30° with the central axis of the fluidized bed reactor.

[0015] The mass ratio of the aqueous solution containing the fire extinguishing active ingredient to the hydrophobic nano-silica is 1-60:1.

[0016] The free water content in the solid water fire extinguishing agent is ≤1%.

[0017] The compressed gas is nitrogen, and the pressure is controlled at 0.3-0.6 MPa.

[0018] The core principle of the real-time continuous preparation method of the solid water fire extinguishing agent provided by the present invention is: using compressed gas to drive hydrophobic nano-silicon dioxide to form a fluidized state, while atomizing the aqueous solution containing the fire extinguishing component into micron-sized droplets, and realizing the instantaneous wrapping of the droplets by the solid material in the violent gas-solid turbulence, forming solid water fire extinguishing agent particles in which the microscopic water core is completely covered by the hydrophobic material. The solid water fire extinguishing agent particles formed use silicon dioxide as a hydrophobic carrier, and its porous structure can wrap the water phase droplets, increase the specific surface area, make it more efficient in endothermic evaporation, and quickly cool down; the chemical properties of silicon dioxide itself are stable, and after the water phase evaporates, the insulation of silicon dioxide helps to continuously cool down and prevent short circuits; adding additives can synergistically inhibit the combustion chain reaction. The present invention realizes the immediate preparation and use of the fire extinguishing agent in a pneumatic manner, avoiding the problems of high energy consumption of mechanical stirring and the risk of clogging of static mixers.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention adopts on-site instant mixing technology. The aqueous solution and the hydrophobic material only come into contact and complete the powdering process when the fire extinguishing operation is started. This completely avoids the risk of demulsification and failure of traditional solid water fire extinguishing agents due to long-term storage, and ensures the effectiveness and reliability of the fire extinguishing agent.

[0021] (2) The present invention optimizes the mixing process to form a high-intensity gas-solid turbulent environment in the fluidized bed. The turbulence intensity can be more than three times that of the conventional static mixing method, which significantly improves the encapsulation efficiency and uniformity of the aqueous solution and effectively ensures the fire extinguishing performance.

[0022] (3) The entire preparation and spraying process of the present invention relies solely on compressed gas as a power source, completely eliminating the electric drive components required for traditional mechanical stirring. The system has a simple structure and safe and reliable operation. It is particularly suitable for special scenarios with extremely high electrical safety requirements, such as explosive gas or dust environments (such as battery energy storage systems).

[0023] (4) The present invention has excellent flow regulation capabilities. By flexibly adjusting the flow rate parameters of the compressed gas, the fire extinguishing agent preparation flow rate can be accurately adjusted within the range of 50 ml / s to 1000 ml / s, thereby being able to adapt to the diverse application requirements of various fire extinguishing systems. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below with reference to specific embodiments.

[0025] Example 1

[0026] First, prepare a 25% aqueous solution of ammonium dihydrogen phosphate and place it in a storage tank. 2 / g of hydrophobic nano-silica was pre-filled into a fluidized bed reactor. 0.5MPa compressed nitrogen was introduced into the bottom of the bed as the fluidizing medium, with the gas velocity controlled at 1.0m / s to ensure full fluidization. An aqueous solution of ammonium dihydrogen phosphate was atomized using an ultrasonic atomizer at a mass ratio of 12:1 and continuously sprayed into the bed. The finished product was discharged through a separator at a flow rate of 500mL / s to obtain a powdered solid water fire extinguishing agent.

[0027] Tests have shown that the D90 particle size of this solid water fire extinguishing agent is 27μm and the free water content is 0.6%. When extinguishing a 200Ah lithium-ion battery thermal runaway fire, the open flame was extinguished within 5 seconds and did not reignite. The cup burner measured its extinguishing concentration for methane fires to be 32g / m 3 It can also extinguish battery fires, including those involving nickel-metal hydride batteries, fuel cells, and zinc-air batteries.

[0028] Example 2

[0029] First, prepare an 18% aqueous solution of ammonium polyphosphate and place it in a liquid storage tank. 2 / g of hydrophobic nano-silica was loaded into a fluidized bed. 0.5MPa compressed nitrogen was introduced into the bed bottom, with the gas velocity controlled at 0.9m / s to fully fluidize the material. An aqueous ammonium polyphosphate solution was atomized using an ultrasonic atomizer at a mass ratio of 15:1 and continuously sprayed into the fluidized bed. The finished product was discharged through a separator at a flow rate of 500mL / s, resulting in a powdered solid water fire extinguishing agent.

[0030] Tests have shown that the D90 particle size of this solid water fire extinguishing agent is 23μm and the free water content is 0.4%. When used to extinguish a 200Ah lithium-ion battery fire, it completely extinguished the fire in 5 seconds without rekindling. Cup burner tests have shown that its extinguishing concentration for methane fires is 30g / m 3 .

[0031] Example 3

[0032] First, prepare a 30% aqueous solution of ammonium bromide and place it in a liquid storage tank. 2 / g of hydrophobic nano-silica was added to a fluidized bed reactor. 0.6MPa compressed nitrogen was introduced into the bed bottom at a controlled velocity of 0.8m / s to fully fluidize the material. An ultrasonic atomizer was used to introduce an aqueous ammonium bromide solution into the bed at a mass ratio of 10:1 (ultrasonic frequency 1.0MHz). The finished product was discharged through a separator at a flow rate of 500mL / s to obtain a powdered solid water fire extinguishing agent.

[0033] Tests have shown that the D90 particle size of this solid water fire extinguishing agent is 30μm and the free water content is 0.9%. Firefighting tests on a 200Ah lithium-ion battery fire showed that the flame was extinguished within 5 seconds and there was no re-ignition. The cup burner measured the extinguishing concentration of this agent on a methane fire to be 36g / m 3 .

[0034] Comparative Example 1

[0035] The specific surface area is 200m 2 / g of hydrophobic nano-silica was pre-filled into the fluidized bed reactor. A 30% aqueous solution of ammonium bromide was prepared and placed in a storage tank. 0.6MPa compressed nitrogen (at a velocity of 0.8m / s) was introduced to fully fluidize the material. Using a conventional spray device (not an ultrasonic atomizer), the aqueous ammonium bromide solution was injected directly into the bed at a mass ratio of 10:1. The finished product was discharged through a separator at a flow rate of 500mL / s.

[0036] The test results show that the D90 particle size of the finished product is 210μm and the residual free water content is 15.8%. The cup burner test shows that the extinguishing concentration of methane fire is greater than 100g / m 3 The comparative example shows that when the ultrasonic atomizer is missing, even if the same hydrophobic material carrier is used, the particle size of the finished product increases and the free water residue increases.

[0037] Comparative Example 2

[0038] The solid water fire extinguishing agent was prepared by conventional mechanical stirring method: 200m2 of the same specific surface area as in Example 1 was weighed. 2 / g hydrophobic nano-silica was placed in a high-speed blender. A 25% aqueous solution of ammonium dihydrogen phosphate was prepared and, with the blender running at 2000 rpm, the solution was poured into the blender at a mass ratio of 12:1. The mixture was stirred continuously for 10 minutes before being discharged. Test results showed that the finished product had a D90 particle size of 201 μm and a free water content of 7.2%. A comparative example demonstrated that even with the same hydrophobic carrier material, the lack of fluidized bed gas-solid turbulence resulted in a longer coagulation time for the solid-water fire extinguishing agent and an increased particle size.

Claims

1. A real-time continuous preparation method of a solid water fire extinguishing agent, characterized in that: The preparation method comprises the following steps performed in sequence: S1. Feeding hydrophobic nano-silica into a fluidized bed reactor through an airtight conveying system, and controlling the feeding rate through a high-pressure pneumatic valve to ensure that the hydrophobic nano-silica is evenly distributed in the bed; S2, introducing compressed gas into the bottom of the fluidized bed reactor as a power source, forming a stable vertical gas column through the gas distributor, so that the hydrophobic nano-silica forms a high-intensity turbulent field in the fluidized bed reactor; S3, injecting an aqueous solution containing a fire extinguishing active ingredient into an ultrasonic atomizer, atomizing it into micron-sized droplets through a resonant cavity, and spraying it into the reaction zone of a fluidized bed reactor through a nozzle; S4. In the gas-solid turbulent flow field, the hydrophobic nano-silica collides with the droplets. Through the combined action of capillary adsorption and van der Waals forces, the hydrophobic nano-silica wraps the droplets to form a core-shell structure with a hydrophobic shell. S5. After being output from the separator, the unwrapped free water is removed through the dehydration device simultaneously, and finally a solid water fire extinguishing agent is produced.

2. The real-time continuous preparation method according to claim 1, wherein: The aqueous solution containing the fire extinguishing active ingredient is selected from at least one of an aqueous solution of ammonium dihydrogen phosphate, an aqueous solution of ammonium polyphosphate and an aqueous solution of ammonium bromide.

3. The real-time continuous preparation method according to claim 1, characterized in that: The particle size of the hydrophobic nano-silicon dioxide is 7-40 nm, and the SiO2 content is ≥99.8%.

4. The real-time continuous preparation method according to claim 1, wherein: The fluidized bed reactor is a spouted fluidized bed reactor, and the flow rate of the compressed gas is 1.8-5 m / s.

5. The real-time continuous preparation method according to claim 1, characterized in that: The ultrasonic atomizer adopts a piezoelectric ultrasonic atomizer, the atomization frequency is 1.0-1.5 MHz, and the CV value of the droplet size is less than 15%.

6. The real-time continuous preparation method according to claim 1, characterized in that: The spraying speed of the nozzle is 20-50 m / s, and the spraying direction forms an angle of 30° with the central axis of the fluidized bed reactor.

7. The real-time continuous preparation method according to claim 1, characterized in that: The mass ratio of the aqueous solution containing the fire extinguishing active ingredient to the hydrophobic nano-silica is 1-60:

1.

8. The real-time continuous preparation method according to claim 1, characterized in that: The free water content in the solid water fire extinguishing agent is ≤1%.

9. The real-time continuous preparation method according to claim 1, wherein: The compressed gas is nitrogen, and the pressure is controlled at 0.3-0.6 MPa.