Unmanned aerial vehicle spraying fireproof magnesium phosphate cement-based material and fire extinguishing method thereof

Abstract

The application discloses an unmanned aerial vehicle spraying fireproof magnesium phosphate cement-based material and a fire extinguishing method thereof, and belongs to the technical field of intelligent construction, and aims to solve the core pain points of difficult fire extinguishing, high rekindling rate and inability of personnel to operate in close proximity in high-risk complex scenes such as extreme emergency, high-rise buildings and chemical industry parks. The material is a two-component composite system, and based on heavy-burning magnesium oxide, the A component powder comprises heavy-burning magnesium oxide, fly ash, borax, expanded graphite and aluminum hydroxide; and the B component comprises ammonium dihydrogen phosphate and water. The fire extinguishing unmanned aerial vehicle hovers at a distance of 2-3 m from the fire source, temperature data based on infrared thermal imaging detection is used to divide 1-5 level regions, precise spraying is realized, when the remaining amount of the material box is less than or equal to 10%, the supply unmanned aerial vehicle completes electromagnetic adsorption aerial box changing in a safe airspace of greater than or equal to 50 m in the fire field, and the limitation of traditional fire extinguishing technology that is low in material efficiency and has a short supply chain is broken, and the material can be efficiently adapted to high-risk scenes such as high-rise buildings and chemical industry parks.

Description

Technical Field

[0001] This invention belongs to the field of intelligent construction technology, specifically relating to a method for spraying fire-resistant magnesium phosphate cement-based material (MPC) by drone and its construction. It is suitable for fire fighting in high-risk and complex scenarios such as high-rise buildings, chemical industrial parks, and remote mountainous areas. It achieves efficient fire extinguishing through a closed-loop process of "intelligent path planning - reconnaissance - targeted spraying - aerial resupply - continuous fire extinguishing". Background Technology

[0002] With the acceleration of urbanization, fire accidents in high-rise buildings, chemical industrial parks and other scenarios occur frequently, and traditional fire extinguishing technologies face many limitations: fire ladders are limited by height and cannot cover the upper areas of high-rise buildings; fires in chemical industrial parks pose risks of explosion and poisoning, and personnel cannot work at close range; traditional fire extinguishing agents (water, dry powder) are prone to reignition after extinguishing and may cause secondary pollution.

[0003] The development of drone technology has provided new solutions for the firefighting field, but existing drone firefighting systems still have shortcomings: on the one hand, the extinguishing agents are mostly traditional types, with limited firefighting efficiency; on the other hand, the drone's payload capacity and endurance are limited, resulting in a small amount of work per operation. Resupply methods are inefficient, requiring frequent landings at ground resupply stations, which seriously affects firefighting efficiency.

[0004] Therefore, it is necessary to provide a two-component magnesium phosphate cement (MPC) with characteristics such as rapid setting, high temperature resistance, strong adhesion, and environmental friendliness and non-corrosiveness, as well as an air-assisted fire suppression and resupply process adapted to it, in order to achieve full and efficient fire suppression. Summary of the Invention

[0005] The purpose of this invention is to provide an efficient, continuous, and safe method for drone-launched fire-retardant magnesium phosphate cement-based material and its fire extinguishing method. Through precise formulation, intelligent path planning, and collaborative container switching, the invention enables the efficient aerial application of two-component MPC, solving the fire extinguishing challenges in high-risk scenarios.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A fire-retardant magnesium phosphate cement-based material for drone spraying, the material being a two-component composite system, with recalcined magnesium oxide as the base. In component A powder, fly ash, borax, expanded graphite, and aluminum hydroxide account for 5%~10%, 3%~6%, 3%~6%, and 1%~4% of the mass of recalcined magnesium oxide, respectively, and the recalcined magnesium oxide is contained in component A; in component B, ammonium dihydrogen phosphate and water account for 35%~55% and 20%~35% of the mass of recalcined magnesium oxide, respectively.

[0007] Furthermore, expanded graphite and aluminum hydroxide need to be dried to remove free moisture and prevent the powder of component A from clumping; the particle size of aluminum hydroxide is 200-300 mesh and the purity is ≥95%; aluminum hydroxide and expanded graphite form a filler that ensures the cooling effect without affecting the setting speed and strength of the magnesium phosphate cement and the covering layer; aluminum hydroxide, expanded graphite, fly ash and borax are pre-mixed evenly and then added to the recalcined magnesium oxide to form component A. After component A is mixed with component B, it can initially set in 5-8 minutes, achieving rapid setting and forming a dense covering layer, thus achieving the dual fire extinguishing functions of cooling and oxygen isolation.

[0008] Furthermore, component A consists of 600g of recalcined magnesium oxide, 50g of fly ash, 30g of borax, 30g of expanded graphite, and 20g of aluminum hydroxide; component B contains 300g of ammonium dihydrogen phosphate and 170g of water.

[0009] This invention also protects a fire extinguishing method based on drone-launched fire-retardant magnesium phosphate cement-based material, the method comprising the following steps: (1) Configure the UAV to spray fireproof magnesium phosphate cement-based material MPC. The UAV-sprayed fireproof magnesium phosphate cement-based material MPC is a two-component composite system. Based on reburned magnesium oxide, the fly ash, borax, expanded graphite and aluminum hydroxide in component A account for 5%~10%, 3%~6%, 3%~6% and 1%~4% of the mass of reburned magnesium oxide, respectively. Reburned magnesium oxide is set in component A. In component B, ammonium dihydrogen phosphate and water account for 35%~55% and 20%~35% of the mass of reburned magnesium oxide, respectively. Components A and B are respectively loaded into a standardized material box. The standardized material box is set in the mounting structure of the fire-fighting UAV. The two standardized material boxes are connected to the pumping unit. The pumping unit speed is calibrated to ensure that components A and B are pumped at a volume ratio of 1:1. (2) At the same time, import the three-dimensional model of the work area, set the basic mode of the fire-fighting drone to "spiral circling + straight sweeping", and the overlap rate of adjacent spraying strips ≤10%; (3) The fire-fighting drone takes off and uses GPS and Beidou dual-mode positioning to locate the operation position. It identifies the fire situation through infrared thermal imaging and high-definition video. The fire situation includes the fire source location, burning area, risk level areas and spread trend. The data is transmitted back to the ground control terminal in real time and the spray path is dynamically updated. The risk level areas are divided into the following categories based on the temperature data detected by infrared thermal imaging: Level 1 extremely high risk area: temperature ≥ 600℃, Level 2 high risk area: temperature is [300℃, 600℃), Level 3 medium risk area: temperature is [100℃, 300℃), Level 4 low risk area: temperature is [50℃, 100℃), Level 5 no open flame easy reignition area and protection area: temperature is less than 50℃. Combined with the dynamic obstacle avoidance algorithm, the intelligent spray path is planned according to the priority of "Level 1 extremely high risk area → Level 2 high risk area → Level 3 medium risk area → Level 4 low risk area → Level 5 no open flame easy reignition area and protection area". (4) After identifying the location of the fire source, the fire-fighting drone hovers 2-3m away from the fire source according to the intelligent spray path, starts the pumping unit, and delivers components A and B to the mixer for uniform mixing and then sends them to the spray gun for spraying onto the burning surface. Fire is extinguished by oxygen isolation and heat absorption. (5) A sensor is installed at the bottom of the standardized material box to monitor the remaining amount of the material box. When the remaining amount of any material box is ≤10%, the fire-fighting drone sends a resupply request. The ground control terminal plans the fire-fighting drone to reach a safe resupply airspace ≥50m away from the fire site. When the remaining amount of the two material boxes of the fire-fighting drone is ≤10%, it is recorded as an empty box. (6) The supply drone carries a spare full container to the supply airspace. The fire-fighting drone grabs the full container with its robotic arm, and the supply drone grabs the empty container with its robotic arm to complete the container replacement and data synchronization. When not in use, the robotic arm is stored inside the drone and extended when in use. (7) The fire-fighting drone returns to the fire scene and repeats step (3), while the supply drone returns with an empty box for resupply, and the cycle continues until the fire is extinguished; (8) After the firefighting drone returns to base, the material bins are disassembled, cleaned and dried, and the equipment is stored after maintenance.

[0010] Furthermore, in step (1), the material box adopts a double sealing structure, with a fluororubber sealing ring in the inner layer and a silicone anti-leakage pad in the outer layer. A pressure sensor is added to the B component material box to prevent solution leakage. Anti-backflow valves are added to the A and B component material boxes respectively to prevent the two components from mixing prematurely due to changes in flight attitude. The A and B component material boxes have built-in micro stirrers, which are linked with the UAV flight status. The entire preparation time before operation is ≤10 minutes, and the ground control terminal synchronously monitors the UAV position, battery power, material box liquid level, and pumping pressure.

[0011] Furthermore, in step (3), the spray gun is an electrically adjustable spray gun: it integrates an electric angle adjustment mechanism and an automatic nozzle switching device. The electric angle adjustment mechanism is adjustable from 30° to 60° with a response time of ≤5 seconds. The automatic nozzle switching device has built-in nozzles with three apertures: 1.0 / 1.5 / 2.0mm. Based on the risk level zone type fed back by infrared thermal imaging, the parameters are automatically matched. 1) Level 1-2 zone: 1.0mm nozzle, 30° fan spray, 40-50mL / s flow rate. Under these conditions, the droplets are concentrated and the coverage thickness is 3mm. 2) Level 3 zone: 1.5mm nozzle, 45° fan-shaped spray, 20-30mL / s flow rate, uniform droplets, and a coverage thickness of 2mm; 3) Level 4 zone: 1.5mm nozzle, 45° fan-shaped spray, 5-10mL / s flow rate, uniform droplets, and a coverage thickness of 1mm; 4) Level 5 no open flame easily reignited area and protected area: 2.0mm nozzle, 60° fan spray, 5-10mL / s flow rate, droplet diffusion, coverage thickness 1mm; The intelligent spraying path planning includes a dynamic adjustment mechanism: when the fire situation is updated, the updated spraying task is automatically inserted into the corresponding path according to priority; when the coating layer is damaged, a local recoating path is triggered; when encountering airflow or obstacles, the path is corrected in real time based on ultrasonic obstacle avoidance data.

[0012] Furthermore, during the container swapping process, the two drones docked via electromagnetic adsorption, with the electromagnetic adsorption docking time being ≤30 seconds, and the entire aerial container swapping process taking ≤180 seconds. The firefighting drone is a quadcopter multi-rotor heavy-duty model with a hovering error of ≤±0.3m; the supply drone is also a quadcopter multi-rotor model equipped with a cooperative positioning unit to counteract the effects of airflow.

[0013] Furthermore, component A consists of 600g of recalcined magnesium oxide, 50g of fly ash, 30g of borax, 30g of expanded graphite, and 20g of aluminum hydroxide; component B contains 300g of ammonium dihydrogen phosphate and 170g of water.

[0014] Furthermore, the pumping unit includes two miniature screw pumps with a flow rate range of 5-50 mL / s and a pressure output of 0.8-1.2 MPa. The speed of the miniature screw pumps is controlled by a stepper motor. The conveying pipeline is made of PEEK material and has a 15 cm expansion allowance. The outlet of the mixer is connected to the inlet of the spray gun through a universal joint. The end of the spray gun is equipped with an automatic nozzle switching device for switching the active nozzle on the spray gun. The inlet of the mixer is connected to the pumping unit.

[0015] Furthermore, the criteria for judging the fire extinguishing in step (7) are: the temperature of the fire scene detected by infrared thermal imaging is ≤50℃, there are no obvious high temperature points, and the covering layer is not peeling or cracked.

[0016] Compared with the prior art, the beneficial effects of the present invention are: High fire extinguishing efficiency: Intelligent path planning reduces ineffective spraying, MPC coating is not easy to fall off, and the reignition rate is low; Strong continuous operation capability: The aerial container changing process does not require landing, solving the "short endurance" problem of traditional drone firefighting processes; Safe and environmentally friendly: MPC formula contains no heavy metals, the process does not cause secondary pollution, and the coating can be mechanically removed after operation; Wide adaptability: By adjusting the spraying parameters (flow rate, angle, thickness), it can be adapted to different scenarios such as high-rise buildings and chemical storage tanks.

[0017] Collaborative Innovation: Breaking through the limitations of single fillers that "either cool down or isolate oxygen", we solve the technical problems of "not lasting cooling, easy detachment of cover, and high reignition rate" in high-risk fire scenarios through three-dimensional synergy of "aluminum hydroxide cooling + expanded graphite oxygen isolation + alumina bonding reinforcement" (traditional fire extinguishing agents generally have a reignition rate of >20%).

[0018] Expanded graphite and aluminum hydroxide form a synergistic system of "heat absorption and cooling - expansion and oxygen isolation". The rapid decomposition and heat absorption of aluminum hydroxide increases the cooling rate of the Level 1 risk zone by 40%, while the high-temperature expansion of expanded graphite seals the combustion surface. The synergy of the two ensures a reignition rate of ≤5% without affecting the initial setting characteristic of MPC in 5-8 minutes. The fire-fighting drone hovers 2-3m above the fire source and divides the area into Level 1-5 zones based on temperature data detected by infrared thermal imaging. It achieves precise spraying with a spray angle of 30°~60° and a targeted flow rate of 5-50mL / s. When the tank volume is ≤10%, the resupply drone completes the electromagnetic adsorption aerial tank replacement within 180 seconds in a safe airspace of ≥50m in the fire area. This invention overcomes the limitations of traditional fire-fighting technologies such as "inefficient materials and short resupply", and has the advantages of high fire-fighting efficiency, good safety, and no secondary pollution. It can be efficiently adapted to high-risk scenarios such as high-rise buildings and chemical industrial parks. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process of using drones for firefighting in this invention.

[0020] Figure 2 This is a diagram illustrating drone firefighting. After a fire is detected, ground control terminal 1 sets the drone parameters and initial flight path, then places materials into a hopper and connects it to the drone, subsequently launching drone 2 (…). Figure 2 (The drone on the left is a firefighting drone, and the drone on the right is a supply drone.) The drones arrived at fire scene 3 and used high-definition cameras and infrared thermal imaging to detect the fire and determine the order of firefighting.

[0021] Figure 3 Detailed diagrams of the firefighting drone and the supply drone are shown. The left image shows the firefighting drone in firefighting mode, where 6 is the component A feed tank (magnesium oxide, fly ash, borax, expanded graphite, aluminum hydroxide), and 7 is the component B feed tank (ammonium dihydrogen phosphate, water). The mixture is then pumped by pumping unit 8 into mixer 4, stirred, and then delivered to spray gun 5 for application. The right image shows the firefighting drone in tank-changing mode, with the front fence open for easy tank changing.

[0022] Figure 4 To resupply the drones, there are 6 component A containers (magnesium oxide, fly ash, borax, expanded graphite, aluminum hydroxide) and 2 component B containers (ammonium dihydrogen phosphate, water).

[0023] In the diagram, 1 is the ground control terminal, 2 is the drone, 3 is the fire site, 4 is the mixer, 5 is the spray gun, 6 is the A component material box, 7 is the B component material box, and 8 is the pumping unit. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but this is not intended to limit the scope of protection of this application.

[0025] This invention relates to a fire-retardant magnesium phosphate cement-based material for drone spraying. It is a two-component formula based on reburned magnesium oxide. Component A contains 5% to 10% fly ash, 3% to 6% borax, 3% to 6% expanded graphite, and 1% to 4% aluminum hydroxide by mass of reburned magnesium oxide. Component B contains 40% to 55% ammonium dihydrogen phosphate and 20% to 35% water by mass of magnesium oxide.

[0026] As one example, component A consists of 600g of recalcined magnesium oxide, 50g of fly ash, 30g of borax, 30g of expanded graphite, and 20g of aluminum hydroxide. Component B contains 300g of ammonium dihydrogen phosphate and 170g of water. The expanded graphite and aluminum hydroxide need to be dried for 2 hours to remove free moisture and prevent clumping of component A. The dosage, particle size (200-300 mesh), and purity (≥95%) of aluminum hydroxide are precisely controlled to achieve an optimal filling ratio of 5.5% with the expanded graphite (30g), ensuring both cooling effect and without affecting the setting speed and strength of the magnesium phosphate cement coating. Aluminum hydroxide, expanded graphite, fly ash, and borax are pre-mixed evenly before being added to the recalcined magnesium oxide to form component A. After mixing with component B, component A can initially set within 5-8 minutes, achieving rapid setting and forming a dense coating layer, thus achieving a dual fire extinguishing function of cooling and oxygen isolation.

[0027] Intelligent spray path planning: Based on temperature data detected by infrared thermal imaging, risk level zones are divided, and priority is designed according to risk level (Level 1 > Level 2 > Level 3 > Level 4 > Level 5). A basic path of "spiral circling + straight sweeping" is planned, and dynamic adjustments are made in conjunction with real-time fire conditions to avoid omissions and repeated spraying. The risk level quantification standards are as follows: Level 1 (extremely high risk) temperature ≥ 600℃, Level 2 (high risk) temperature [300℃, 600℃), Level 3 (medium risk) temperature [100℃, 300℃), Level 4 (low risk) temperature [50℃, 100℃), Level 5 (areas with no open flame and easy reignition, as well as protected areas) temperature less than 50℃. The dynamic adjustment response time of the UAV transmitting signals to the ground control terminal is ≤30 seconds, and the path obstacle avoidance accuracy is ≤0.5m.

[0028] Targeted spraying: Select different spray angles (30°~60°), nozzle orifice diameters (1.0 / 1.5 / 2.0mm), and pump flow rates (5-50mL / s) according to the fire zone. Control the spraying distance (2-3m) and thickness (1-3mm) according to the intelligent spraying path to ensure stable adhesion of the coating layer. At the same time, through dual-machine positioning compensation (the two machines achieve precise alignment through GPS / Beidou dual-mode positioning + airflow disturbance compensation algorithm) and robotic arm grasping, realize rapid box changing without landing (≤180 seconds) to ensure process continuity.

[0029] As a preferred example, in this invention, the firefighting drone and the supply drone first perform electromagnetic adsorption docking before changing containers. An electromagnetic docking structure is set on opposite sides of the firefighting drone and the supply drone, and the two drones are connected in the air through the electromagnetic docking structure. The setting of the electromagnetic docking structure does not interfere with the opening and closing of the opening and closing fence in the mounting structure, and does not affect the operation of the wings during docking. After docking, the opening and closing fences of the mounting structures of the two aircraft can be opened, and there is room for opening.

[0030] Regarding drone settings: (1) The mounting structure is "hollowed out" to reduce heat conduction and ensure that the MPC temperature inside the pipeline is ≤50℃. The right / rear / left sides of the material box mounting area are fixed fences (retaining the original protective function, and the material is lightweight aviation aluminum); the front side is the box changing operation side, which is equipped with an electric opening and closing fence (the side that docks with the supply UAV). The opening and closing fence is a single-leaf rotating type, with the rotating shaft located on both sides of the fence. After opening, it rotates to both sides to completely clear the box changing passage. Among them, the electric control end of the electric opening and closing fence is connected to the ground control end by telecommunications; after the box changing is completed, the electric opening and closing fence is closed to restrict the spatial position of the material box to prevent movement and effectively prevent it from falling off.

[0031] (2) An electric angle adjustment mechanism and an automatic nozzle switching device are set up, which can quickly change the nozzle diameter and adjust the spray angle according to different fire conditions, thereby saving the waiting time for magnesium phosphate cement to be sprayed. (3) The standardized material box is equipped with a double-sealed material box and a built-in micro agitator. During transportation, the double-sealed material box can prevent the leakage of magnesium phosphate cement, and the micro agitator can prevent the powder from agglomerating. (4) The standardized material bin outlet is connected to the spray gun 5 via the pumping unit 8 and the mixer 4. The outlet of the mixer is connected to the inlet of the spray gun via a universal joint. An automatic nozzle switching device is installed at the end of the spray gun to switch the active nozzle on the spray gun. The inlet of the mixer is connected to the pumping unit. The material is sprayed onto the burning surface through the spray gun, and fire is extinguished by oxygen isolation and heat absorption. The conveying pipeline is made of PEEK material, which reduces the impact of external factors on the magnesium phosphate cement during the spraying process, thus ensuring the efficiency of the spraying. All of these accessories are highly compatible with the magnesium phosphate cement system.

[0032] (5) Monitoring equipment: GPS / BeiDou dual-mode positioning, infrared thermal imaging, high-definition camera, ultrasonic sensor.

[0033] (6) Mechanical gripper, used to exchange standardized feed bins for supply drones and firefighting drones.

[0034] In this invention, expanded graphite and aluminum hydroxide need to be dried for 2 hours to remove free moisture and avoid clumping of component A powder; after the two are pre-mixed evenly with borax, they are added to magnesium oxide to ensure uniform dispersion.

[0035] Example 1: Fire on the exterior wall of a high-rise building Process preparation: Configure 4 sets of two-component MPC (4 boxes each of components A and B), with one box of each component fixed in the mounting structure of the fire-fighting drone. Calibrate the pumping unit at speed 8 (ensuring a volume ratio of 1:1). In component A, expanded graphite (30g, particle size 100-200 mesh, expansion ratio ≥200 times) and aluminum hydroxide (20g, particle size 200-300 mesh, purity ≥95%) have been pre-dried for 2 hours to remove free moisture. After premixing with borax, magnesium oxide is added to avoid clumping and ensure uniform dispersion.

[0036] Import the 3D model of the building's exterior wall. The system plans the initial intelligent spraying path according to the following: "Level 1 core area of ​​the window (≥600℃) → Level 2 spread channel of the exterior wall around the window (300-600℃) → Level 3 diffusion area around the floor (100-300℃) → Level 4 of the adjacent floor → Level 5 protection area of ​​the more distant floor". The system improves the hovering accuracy (error ≤ ±0.3m) by using the load-bearing structure as a reference point and reserves 0.3m / s speed compensation to cope with high-rise winds. The system completes preparation within 10 minutes. The firefighting drone took off and flew to a distance of 10 meters from the fire site. Using GPS and BeiDou dual-mode positioning (hovering error ≤ ±0.3m), an infrared thermal imager, and a high-definition camera, it identified the fire and detected a Class 1 core fire zone (6m) with a temperature ≥600℃ at a high-rise window.2 ) and the surrounding 300~600℃ level 2 spread zone (6m) 2 Fire data is transmitted back to the ground control terminal in real time.

[0037] The ground control unit replans the intelligent spraying path by combining fire information and a multi-sensor fusion dynamic obstacle avoidance algorithm. This algorithm integrates an ultrasonic obstacle avoidance sensor (response time ≤ 0.1 seconds) and PID flight control attitude adjustment, achieving obstacle avoidance accuracy ≤ 0.5m. It can automatically avoid fixed obstacles such as air conditioning units on building exteriors, window frames, and vertical pipelines. Furthermore, it achieves real-time drone position compensation under high-rise gust wind disturbances, ensuring the spraying path remains 2-3m away from the fire source. The multi-sensor fusion dynamic obstacle avoidance algorithm can be implemented using existing technologies.

[0038] Hover the intelligent spray path 2m above the fire source: (1) For the core areas of level 1 and 2: apply a high flow rate of 40-50 mL / s and a 30° fan-shaped spray (thickness 3 mm) - at this time, aluminum hydroxide quickly comes into contact with the high temperature surface, decomposes and absorbs heat instantly, and quickly reduces the core temperature of the flame (the cooling rate within 3 minutes is 40% higher than that of the traditional formula). At the same time, it releases crystal water and evaporates to form a temporary oxygen barrier. The expanded graphite sprayed at the same time expands after being heated and forms a "worm-like" graphite layer to seal the combustion surface. The amorphous alumina powder generated by the decomposition of aluminum hydroxide just binds the graphite layer to prevent it from falling off due to high-altitude wind or flame impact. The two work together to form a dense covering layer to quickly suppress the open flame. (2) For the third-level diffusion zone (100-300℃): switch to a 1.5mm nozzle, spray in a 45° fan shape, and apply a topcoat at a flow rate of 20-30mL / s, with a coverage thickness of 2mm. Although there is no open flame in this area, the temperature is high. The aluminum hydroxide continues to decompose slowly to maintain the cooling. The oxygen barrier layer formed by the expanded graphite blocks air contact and prevents reignition (final reignition rate ≤5%). (3) For Level 4 protection zones (adjacent floor windowsills): Apply a coating at a flow rate of 5-10 mL / s (1 mm thick) to utilize the low-temperature stability of aluminum hydroxide and the physical isolation of expanded graphite to build a protective layer in advance and suppress the spread of fire to adjacent floors. When the initial material bin balance is ≤10%, a resupply request is triggered, and the bin is exchanged in the air 50m away from the fire scene. After three rounds of container changes and 40 minutes of continuous operation, the fire temperature dropped below 80°C, there was no reignition, and the spraying was completed. After the drone returns to base, it blows through the pipes, cleans and dries the material bins, and performs equipment maintenance and storage.

[0039] To verify the specific compatibility of the expanded graphite + aluminum hydroxide dual filler combination in this invention with magnesium phosphate cement-based fireproof materials, three comparative examples were set up below. All examples used magnesium oxide as a base (component A consisted of 600g of reburned magnesium oxide, 50g of fly ash, and 30g of borax; component B consisted of 300g of ammonium dihydrogen phosphate and 170g of water) (this ratio conforms to the formulation range). Only the filler in component A was replaced, with the filler percentage (all powders) being 5.5% (50g). Simulating the conditions of a Class 1 fire risk zone (≥600℃), the same UAV spraying process as this invention was used to test the initial setting time, reignition rate, and the density of the protective layer, comparing it with the core embodiment of this invention. The dual filler and MPC matrix synergistically form a "heat absorption and cooling - expansion and oxygen isolation" composite system, increasing the cooling rate of the Class 1 risk zone by 40% and reducing the reignition rate to ≤5%, adapting to the core fire extinguishing needs of high-rise buildings, chemical industrial parks, and other scenarios.

[0040] Remove the expanded graphite and aluminum hydroxide of the present invention and replace them with 30g of expanded vermiculite (particle size 100-200 mesh) and 20g of magnesium hydroxide (particle size 200-300 mesh, purity ≥95%) of equal mass. The remaining components and proportions remain unchanged. Under the same conditions, the material box is filled and the pumping is calibrated. The intelligent spraying path is then planned by importing the three-dimensional model of the exterior wall of the high-rise building.

[0041] Test results: The initial setting time was 18 minutes, far exceeding the 5-8 minute initial setting range of this invention. Local initial setting occurred in the pipeline during the spraying process. The decomposition and heat absorption rate of magnesium hydroxide in the spray gun was slow. The high water absorption rate of expanded vermiculite led to insufficient hydration reaction of MPC and reduced cooling effect. Two blockages occurred, making it impossible to quickly form an effective covering layer in the fire. The covering layer formed by expanded vermiculite had high porosity, poor oxygen barrier effect, and weak adhesion to the MPC matrix. Due to the influence of high-altitude winds, the area of ​​detachment reached about 40%.

[0042] Remove the expanded graphite and aluminum hydroxide of the present invention and replace them with 30g of expanded perlite (particle size 100-200 mesh) and 20g of ordinary talc powder (particle size 200-300 mesh) of equal mass, while keeping the other components and proportions unchanged; under the same conditions, fix the material box, calibrate the pumping unit speed, import the three-dimensional model of the high-rise building exterior wall to plan the intelligent spraying path, and complete the preparations before operation.

[0043] Test results: The initial setting time is close to that of the present invention, but the covering layer shows the phenomenon of "local rapid setting and local non-setting", which cannot form a dense protective layer. The expanded perlite is lightweight and porous, and has extremely poor adhesion to the MPC matrix. Affected by the thermal shock of the flame and the slight airflow at high altitude, the covering layer falls off instantly. There is no effective oxygen barrier on the surface of the curtain wall. After reignition, the flame spreads rapidly to both sides, and the reignition rate is 20% higher than that of the present invention.

[0044] The expanded graphite of this invention is replaced with 30g of ordinary microcrystalline graphite powder (particle size 100-200 mesh) of equal mass, and 20g of aluminum hydroxide (particle size 200-300 mesh, purity ≥95%) is retained, while the other components and proportions remain unchanged. Under the same conditions, the material box is fixed and the pumping is calibrated. After drying the ordinary microcrystalline graphite powder and aluminum hydroxide for 2 hours, they are premixed with borax and then added to magnesium oxide. The intelligent spraying path is planned by importing the three-dimensional model of the exterior wall of a high-rise building.

[0045] Test results: The initial setting time was similar. Ordinary microcrystalline graphite powder has no high-temperature expansion characteristics and can only achieve physical coverage. It cannot seal the hollow structure of the balcony and the gaps on the burning surface. Outdoor airflow continuously replenishes oxygen through the gaps. Multiple reignition points appeared within minutes after the open flame was extinguished. The reignition rate was significantly improved compared to the system of this invention. The cover layer had poor density and small gaps. Its oxygen barrier capacity was insufficient and it could not form a sealed oxygen barrier.

[0046] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A fire-retardant magnesium phosphate cement-based material for drone spraying, characterized in that, The material is a two-component composite system. Based on calcined magnesium oxide, the fly ash, borax, expanded graphite, and aluminum hydroxide in component A account for 5%~10%, 3%~6%, 3%~6%, and 1%~4% of the mass of calcined magnesium oxide, respectively, and the calcined magnesium oxide is contained in component A. In component B, ammonium dihydrogen phosphate and water account for 35%~55% and 20%~35% of the mass of calcined magnesium oxide, respectively.

2. The drone-sprayed fire-retardant magnesium phosphate cement-based material according to claim 1, characterized in that, Expanded graphite and aluminum hydroxide need to be dried to remove free moisture and prevent the powder of component A from clumping. The particle size of aluminum hydroxide is 200-300 mesh and the purity is ≥95%. Aluminum hydroxide and expanded graphite form a filler that ensures the cooling effect without affecting the setting speed and strength of the magnesium phosphate cement and the covering layer. After aluminum hydroxide, expanded graphite, fly ash and borax are pre-mixed evenly, they are added to the recalcined magnesium oxide to form component A. After component A is mixed with component B, it can initially set in 5-8 minutes, achieving rapid setting and forming a dense covering layer, thus achieving the dual fire extinguishing functions of cooling and oxygen isolation.

3. The drone-sprayed fire-retardant magnesium phosphate cement-based material according to claim 1, characterized in that, Component A powder: 600g of recalcined magnesium oxide, 50g of fly ash, 30g of borax, 30g of expanded graphite, and 20g of aluminum hydroxide; Component B contains 300g of ammonium dihydrogen phosphate and 170g of water.

4. A fire extinguishing method based on unmanned aerial vehicle (UAV) spraying fire-retardant magnesium phosphate cement-based material, characterized in that, The method includes the following steps: (1) Configure the UAV to spray fireproof magnesium phosphate cement-based material MPC. The UAV-sprayed fireproof magnesium phosphate cement-based material MPC is a two-component composite system. Based on reburned magnesium oxide, the fly ash, borax, expanded graphite and aluminum hydroxide in component A account for 5%~10%, 3%~6%, 3%~6% and 1%~4% of the mass of reburned magnesium oxide, respectively. Reburned magnesium oxide is set in component A. In component B, ammonium dihydrogen phosphate and water account for 35%~55% and 20%~35% of the mass of reburned magnesium oxide, respectively. Components A and B are respectively loaded into a standardized material box. The standardized material box is set in the mounting structure of the fire-fighting UAV. The two standardized material boxes are connected to the pumping unit. The pumping unit speed is calibrated to ensure that components A and B are pumped in a volume ratio of 1:

1. (2) At the same time, import the three-dimensional model of the work area, set the basic mode of the fire-fighting drone to "spiral circling + straight sweeping", and the overlap rate of adjacent spraying strips ≤10%; (3) The fire-fighting drone takes off and uses GPS and Beidou dual-mode positioning to locate the operation position. It identifies the fire situation through infrared thermal imaging and high-definition video. The fire situation includes the fire source location, burning area, risk level areas and spread trend. The data is transmitted back to the ground control terminal in real time and the spray path is dynamically updated. The risk level areas are divided into the following categories based on the temperature data detected by infrared thermal imaging: Level 1 extremely high risk area: temperature ≥ 600℃, Level 2 high risk area: temperature is [300℃, 600℃), Level 3 medium risk area: temperature is [100℃, 300℃), Level 4 low risk area: temperature is [50℃, 100℃), Level 5 no open flame easy reignition area and protection area: temperature is less than 50℃. Combined with the dynamic obstacle avoidance algorithm, the intelligent spray path is planned according to the priority of "Level 1 extremely high risk area → Level 2 high risk area → Level 3 medium risk area → Level 4 low risk area → Level 5 no open flame easy reignition area and protection area". (4) After identifying the location of the fire source, the fire-fighting drone hovers 2-3m away from the fire source according to the intelligent spray path, starts the pumping unit, and delivers components A and B to the mixer for uniform mixing and then sends them to the spray gun for spraying onto the burning surface. Fire is extinguished by oxygen isolation and heat absorption. (5) A sensor is installed at the bottom of the standardized material box to monitor the remaining amount of the material box. When the remaining amount of any material box is ≤10%, the fire-fighting drone sends a resupply request. The ground control terminal plans the fire-fighting drone to reach a safe resupply airspace ≥50m away from the fire site. When the remaining amount of the two material boxes of the fire-fighting drone is ≤10%, it is recorded as an empty box. (6) The supply drone carries a spare full container to the supply airspace. The fire-fighting drone grabs the full container with its robotic arm, and the supply drone grabs the empty container with its robotic arm to complete the container replacement and data synchronization. When not in use, the robotic arm is stored inside the drone and extended when in use. (7) The fire-fighting drone returns to the fire scene and repeats step (3). The supply drone returns with an empty box for resupply. This cycle continues until the fire is extinguished. (8) After the firefighting drone returns to base, the material bins are disassembled, cleaned and dried, and the equipment is stored after maintenance.

5. The fire extinguishing method according to claim 4, characterized in that, In step (1), the material box adopts a double sealing structure. The inner layer uses a fluororubber sealing ring, and the outer layer uses a silicone anti-leakage pad. A pressure sensor is added to the B component material box to avoid solution leakage. Anti-backflow valves are added to the A and B component material boxes to prevent the two components from mixing prematurely due to changes in flight attitude. The A and B component material boxes have built-in micro stirrers, which are linked to the UAV's flight status. The entire preparation before operation takes ≤10 minutes. The ground control terminal synchronously monitors the UAV's position, battery power, material box liquid level, and pumping pressure.

6. The fire extinguishing method according to claim 4, characterized in that, In step (3), the spray gun is an electrically adjustable spray gun: it integrates an electric angle adjustment mechanism and an automatic nozzle switching device. The electric angle adjustment mechanism is adjustable from 30° to 60° with a response time of ≤5 seconds. The automatic nozzle switching device has built-in nozzles with three apertures: 1.0 / 1.5 / 2.0mm. Based on the risk level zone type fed back by infrared thermal imaging, the parameters are automatically matched. 1) Level 1-2 zone: 1.0mm nozzle, 30° fan spray, 40-50mL / s flow rate. Under these conditions, the droplets are concentrated and the coverage thickness is 3mm. 2) Level 3 zone: 1.5mm nozzle, 45° fan-shaped spray, 20-30mL / s flow rate, uniform droplets, and a coverage thickness of 2mm; 3) Level 4 zone: 1.5mm nozzle, 45° fan-shaped spray, 5-10mL / s flow rate, uniform droplets, and a coverage thickness of 1mm; 4) Level 5 no open flame easily reignited area and protected area: 2.0mm nozzle, 60° fan spray, 5-10mL / s flow rate, droplet diffusion, coverage thickness 1mm; The intelligent spraying path planning includes a dynamic adjustment mechanism: when the fire situation is updated, the updated spraying task is automatically inserted into the corresponding path according to priority; when the coating layer is damaged, a local recoating path is triggered; when encountering airflow or obstacles, the path is corrected in real time based on ultrasonic obstacle avoidance data.

7. The fire extinguishing method according to claim 4, characterized in that, During the container swapping process, the two drones docked via electromagnetic adsorption. The electromagnetic adsorption docking time was ≤30 seconds, and the entire aerial container swapping process took ≤180 seconds. The firefighting drone is a quadcopter multi-rotor heavy-duty model with a hovering error of ≤±0.3m; the supply drone is also a quadcopter multi-rotor model equipped with a cooperative positioning unit to counteract the effects of airflow.

8. The fire extinguishing method according to claim 4, characterized in that, Component A powder: 600g of recalcined magnesium oxide, 50g of fly ash, 30g of borax, 30g of expanded graphite and 20g of aluminum hydroxide; Component B contains 300g of ammonium dihydrogen phosphate and 170g of water.

9. The fire extinguishing method according to claim 4, characterized in that, The pumping unit includes two miniature screw pumps with a flow rate range of 5-50 mL / s and a pressure output of 0.8-1.2 MPa. The speed of the miniature screw pumps is controlled by a stepper motor. The conveying pipeline is made of PEEK material and has a 15 cm expansion allowance. The outlet of the mixer is connected to the inlet of the spray gun through a universal joint. The end of the spray gun is equipped with an automatic nozzle switching device to switch the effective nozzle on the spray gun. The inlet of the mixer is connected to the pumping unit.

10. The fire extinguishing method according to claim 4, characterized in that, The criteria for judging the fire extinguishing in step (7) are: the temperature of the fire scene detected by infrared thermal imaging is ≤50℃, there are no obvious high temperature points, and the covering layer is not peeling or cracked.

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