An apparatus for producing fire fighting water and a method for preparing fire fighting water using the same

Abstract

This invention belongs to the field of fire protection technology, specifically relating to an apparatus for producing fire-fighting water and a method for preparing fire-fighting water using the same apparatus. The apparatus provided by this invention includes a urea-containing wastewater treatment unit, an agricultural wastewater treatment unit, and a seawater treatment unit. The apparatus provided by this invention integrates multiple functions, not only reducing the pressure of pollutant discharge but also alleviating the problem of insufficient fresh water for fire fighting and reducing the corrosive hazards of directly using seawater for fire extinguishing. Furthermore, this invention successfully expands wastewater treatment into the production of fire-fighting water, pioneering a circular economy-style fire-fighting water supply model.

Description

Technical Field

[0001] This invention belongs to the field of fire protection technology, specifically relating to an apparatus for producing fire-fighting water and a method for preparing fire-fighting water using the apparatus. Background Technology

[0002] In island and coastal regions like the Middle East where freshwater resources are scarce, the development of alternative water sources to meet specific needs is becoming increasingly urgent as the concept of sustainable environmental development deepens and water resource utilization efficiency continues to improve. Seawater, as an abundant and readily available resource, is gaining attention for its application in firefighting. However, the high salinity of seawater poses a series of technical challenges when directly applied to firefighting, such as corrosion of firefighting equipment, potential damage to the soil environment, and reduced firefighting efficiency. Therefore, how to achieve efficient utilization of seawater in firefighting while effectively controlling its high salinity has become a critical technical problem that urgently needs to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide an apparatus for producing fire-fighting water and a method for preparing fire-fighting water using the apparatus. The apparatus for producing fire-fighting water provided by this invention can convert seawater into fire-fighting water, thereby improving the effectiveness of seawater fire suppression.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] The present invention provides an apparatus for producing fire-fighting water, comprising a urea-containing wastewater treatment unit, an agricultural wastewater treatment unit, and a seawater treatment unit;

[0006] The urea-containing waste liquid treatment unit includes a heating tank and an ammonium sulfate synthesis tower connected to the heating tank;

[0007] The agricultural wastewater treatment unit includes a first mixing tank, a second mixing tank, a sedimentation tank, an ultrafiltration device, and a first water storage tank connected in sequence; the outlet of the ammonium sulfate synthesis tower is connected to the inlet of the second mixing tank;

[0008] The seawater treatment unit includes a first module, a second module, a second water storage tank, and a third mixing tank;

[0009] The first module includes a reverse osmosis system, an energy recovery device connected to the reverse osmosis system, a forward osmosis device connected to the energy recovery device, and a high-pressure pump connected to the forward osmosis device; the high-pressure pump is connected to the reverse osmosis system; and the high-pressure pump and the energy recovery device are connected in series.

[0010] The second module includes a low-pressure pump; the low-pressure pump is connected to the reverse osmosis system of the first module to form a loop;

[0011] The third mixing tank is connected to the forward osmosis equipment of the first module through the second water storage tank;

[0012] The outlet of the reverse osmosis system is connected to the inlet of the third mixing tank.

[0013] Preferably, the ultrafiltration device is provided with an ultrafiltration membrane; the pore size of the ultrafiltration membrane is 0.01 to 0.1 μm; the molecular weight cutoff of the ultrafiltration membrane is 1,000 to 500,000 Da;

[0014] The forward osmosis device is equipped with a forward osmosis membrane; the pore size of the forward osmosis membrane is <1 nm; the membrane flux of the forward osmosis membrane is 5–20 L / (m²). 2 *h).

[0015] Preferably, the reverse osmosis system includes multiple reverse osmosis pressure vessels connected in parallel; each reverse osmosis pressure vessel is provided with multiple membrane elements; the number of reverse osmosis pressure vessels is ≥4; and the number of membrane elements is ≥3.

[0016] Preferably, the reverse osmosis system is provided with a reverse osmosis membrane; the reverse osmosis membrane is a polyamide composite membrane; the pore size of the reverse osmosis membrane is <0.1nm.

[0017] Preferably, the reverse osmosis system is connected to the low-pressure pump and the energy recovery device respectively through the first valve; the forward osmosis equipment is connected to the drain pipe and the high-pressure pump respectively through the second valve.

[0018] The present invention also provides a method for preparing fire-fighting water using the apparatus described above, comprising the following steps:

[0019] Urea-containing waste liquid and alkaline reagents are mixed in a heating tank to obtain ammonia and carbon dioxide.

[0020] Ammonia gas is introduced into the ammonium sulfate synthesis tower and mixed with the first sulfuric acid solution to carry out the synthesis reaction and obtain ammonium sulfate.

[0021] Agricultural phosphorus-containing wastewater and a second sulfuric acid solution are mixed in a first mixing tank to carry out a first metathesis reaction, yielding phosphoric acid and calcium sulfate; the agricultural phosphorus-containing wastewater contains Ca(H2PO4)2.

[0022] Phosphoric acid, ammonium sulfate and ammonia are introduced into a second mixing tank to carry out a combination reaction and a second metathesis reaction to obtain an ammonium dihydrogen phosphate system.

[0023] After the ammonium dihydrogen phosphate system is precipitated in a sedimentation tank, it is then ultrafiltered through an ultrafiltration device to obtain ultrafiltered water, which is placed in the first water storage tank.

[0024] Seawater is fed into a reverse osmosis system for initial reverse osmosis treatment to obtain initial reverse osmosis concentrate and initial reverse osmosis desalination.

[0025] The initial reverse osmosis concentrate is returned to the reverse osmosis system for the first reverse osmosis treatment, resulting in reflux reverse osmosis concentrate and reflux reverse osmosis desalination.

[0026] When the recovery rate of the first reverse osmosis treatment reaches 50-60%, the first valve is opened, and the reflux reverse osmosis concentrate is depressurized through the energy recovery device to obtain the first depressurized brine. Using the first depressurized brine as the draw solution and ultrafiltration water as the diluent, the first forward osmosis treatment is performed to obtain the first diluted depressurized brine and the first concentrated ultrafiltration water. The first diluted depressurized brine is returned to the reverse osmosis system for the second reverse osmosis treatment to obtain the circulating reverse osmosis concentrate and the circulating reverse osmosis desalination water. The first concentrated ultrafiltration water is stored in the second storage tank.

[0027] When the operating pressure of the reverse osmosis equipment reaches 77-78 bar, the circulating reverse osmosis concentrate is depressurized through the energy recovery device to obtain the second depressurized brine and the second concentrated ultrafiltration water. The second depressurized brine is used as the draw solution and the ultrafiltration water is used as the diluent for the second forward osmosis treatment to obtain the second diluted depressurized brine and the second concentrated ultrafiltration water. The second diluted depressurized brine is discharged through the drain pipe and the second concentrated ultrafiltration water is stored in the second water storage tank.

[0028] Reverse osmosis desalinated water and concentrated ultrafiltration water are fed into the third mixing tank to obtain fire-fighting water;

[0029] The reverse osmosis freshwater includes initial reverse osmosis freshwater, reflux reverse osmosis freshwater, and circulating reverse osmosis freshwater;

[0030] The concentrated ultrafiltration water includes first concentrated ultrafiltration water and second concentrated ultrafiltration water.

[0031] Preferably, the alkaline reagent includes NaOH; the temperature of the catalytic decomposition reaction is 50–70°C, the catalytic decomposition time is 1–2 h, and the pH value of the reaction system of the catalytic decomposition reaction is >9.

[0032] Preferably, the temperature of the first metathesis reaction is 60–80°C, and the time of the first metathesis reaction is 1.5–2 hours.

[0033] Preferably, the temperature of the combination reaction and the second metathesis reaction is 25-40°C, and the time is 0.5-1h.

[0034] Preferably, the content of ammonium dihydrogen phosphate in the fire-fighting water is 10-20 wt.%.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The device provided by this invention integrates multiple functions (waste resource utilization + seawater desalination + fire extinguishing agent synthesis), which not only reduces the pressure of pollutant discharge (such as direct discharge of urine and agricultural wastewater), but also alleviates the problem of insufficient freshwater for fire fighting and reduces the corrosive hazards of directly using seawater for fire extinguishing. Furthermore, this invention successfully expands wastewater treatment to produce fire-fighting water, pioneering a circular economy-style fire-fighting water supply model. Moreover, the final fire-fighting water contains a certain amount of salts such as ammonium dihydrogen phosphate, exhibiting superior fire extinguishing performance compared to pure water, and is relatively friendly to soil and vegetation (it can be used as fertilizer after fire extinguishing, avoiding secondary hazards caused by residual seawater salt). In summary, this device simultaneously realizes three functions: waste utilization, seawater desalination, and fire extinguishing agent preparation, and has high application potential. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 A flowchart illustrating a method for preparing fire-fighting water using the apparatus provided by this invention;

[0039] Figure 2 This is a diagram showing the operating pressure of reverse osmosis during the three concentration processes in Example 1;

[0040] Figure 3 This is a diagram showing the seawater salinity during the three concentration processes in Example 1;

[0041] Figure 4 This is a diagram showing the operating pressure of reverse osmosis during the five concentration cycles in Example 1;

[0042] Figure 5 This is a diagram showing the seawater salinity during the three concentrations in Example 1. Detailed Implementation

[0043] The present invention provides an apparatus for producing fire-fighting water, comprising a urea-containing wastewater treatment unit, an agricultural wastewater treatment unit, and a seawater treatment unit;

[0044] The urea-containing waste liquid treatment unit includes a heating tank and an ammonium sulfate synthesis tower connected to the heating tank;

[0045] The agricultural wastewater treatment unit includes a first mixing tank, a second mixing tank, a sedimentation tank, an ultrafiltration device, and a first water storage tank connected in sequence; the outlet of the ammonium sulfate synthesis tower is connected to the inlet of the second mixing tank;

[0046] The seawater treatment unit includes a first module, a second module, a second water storage tank, and a third mixing tank;

[0047] The first module includes a reverse osmosis system, an energy recovery device connected to the reverse osmosis system, a forward osmosis device connected to the energy recovery device, and a high-pressure pump connected to the forward osmosis device; the high-pressure pump is connected to the reverse osmosis system; and the high-pressure pump and the energy recovery device are connected in series.

[0048] The second module includes a low-pressure pump; the low-pressure pump is connected to the reverse osmosis system of the first module to form a loop;

[0049] The third mixing tank is connected to the forward osmosis equipment of the first module through the second water storage tank;

[0050] The outlet of the reverse osmosis system is connected to the inlet of the third mixing tank.

[0051] like Figure 1 As shown, the device for producing fire-fighting water provided by the present invention includes a urea-containing wastewater treatment unit, an agricultural wastewater treatment unit, and a seawater treatment unit; the urea-containing wastewater treatment unit includes a heating tank and an ammonium sulfate synthesis tower connected to the heating tank; the agricultural wastewater treatment unit includes a first mixing tank, a second mixing tank, a sedimentation tank, an ultrafiltration device, and a first water storage tank connected in sequence; the outlet of the ammonium sulfate synthesis tower is connected to the inlet of the second mixing tank.

[0052] In one embodiment of the present invention, the sedimentation tank and the ultrafiltration equipment are preferably connected by a low-pressure pump;

[0053] In one embodiment of the present invention, the pore size of the ultrafiltration membrane of the ultrafiltration device can be 0.01 to 0.1 μm, specifically 0.02 to 0.1 μm; the molecular weight cutoff of the ultrafiltration membrane can be 1,000 to 500,000 Da, specifically 10,000 to 100,000 Da; and the material of the ultrafiltration membrane can be polyethersulfone or polyvinylidene fluoride.

[0054] The present invention provides an apparatus for producing fire-fighting water, wherein the seawater treatment unit includes a first module, a second module, a second water storage tank, and a third mixing tank; the first module includes a reverse osmosis system, an energy recovery device connected to the reverse osmosis system, a forward osmosis device connected to the energy recovery device, and a high-pressure pump connected to the forward osmosis device; the high-pressure pump is connected to the reverse osmosis system; and the high-pressure pump and the energy recovery device are connected in series.

[0055] In one embodiment of the present invention, the pore size of the forward osmosis membrane in the forward osmosis device can be <1 nm, and the membrane flux of the forward osmosis membrane can be 5–20 L / (m²). 2 *h).

[0056] In one embodiment of the present invention, the reverse osmosis system includes multiple reverse osmosis pressure vessels connected in parallel; multiple membrane elements are disposed in each reverse osmosis pressure vessel; the number of reverse osmosis pressure vessels is ≥4; and the number of membrane elements is ≥3.

[0057] In one embodiment of the present invention, the reverse osmosis membrane in the reverse osmosis system can be made of polyamide composite membrane (TFC); the water flux of the reverse osmosis membrane can be 1.65 L / (m²). 2 *h*bar), the salt flux can be 0.113 L / (m 2 *h).

[0058] In one embodiment of the present invention, the reverse osmosis system is connected to a low-pressure pump and an energy recovery device via a first valve; the forward osmosis device is connected to a drain pipe and a high-pressure pump via a second valve. In another embodiment, the high-pressure pump can provide the operating pressure required for reverse osmosis; the low-pressure pump can compensate for the pressure difference during reverse osmosis operation. In yet another embodiment, the energy recovery device is preferably a flow-generating motor.

[0059] In one embodiment of the present invention, the forward osmosis device is connected to a drain pipe and a high-pressure pump respectively through a second valve.

[0060] The present invention also provides a method for preparing fire-fighting water using the apparatus for producing fire-fighting water described above, comprising the following steps:

[0061] Urea-containing waste liquid and alkaline reagents are mixed in a heating tank to obtain ammonia and carbon dioxide.

[0062] Ammonia gas is introduced into the ammonium sulfate synthesis tower and mixed with the first sulfuric acid solution to carry out the synthesis reaction and obtain ammonium sulfate.

[0063] Agricultural phosphorus-containing wastewater and a second sulfuric acid solution are mixed in a first mixing tank to carry out a first metathesis reaction, yielding phosphoric acid and calcium sulfate; the agricultural phosphorus-containing wastewater contains Ca(H2PO4)2.

[0064] Phosphoric acid, ammonium sulfate and ammonia are introduced into a second mixing tank to carry out a combination reaction and a second metathesis reaction to obtain an ammonium dihydrogen phosphate system.

[0065] After the ammonium dihydrogen phosphate system is precipitated in a sedimentation tank, it is then ultrafiltered through an ultrafiltration device to obtain ultrafiltered water, which is placed in the first water storage tank.

[0066] Seawater is fed into a reverse osmosis system for initial reverse osmosis treatment to obtain initial reverse osmosis concentrate and initial reverse osmosis desalination.

[0067] The initial reverse osmosis concentrate is returned to the reverse osmosis system for the first reverse osmosis treatment, resulting in reflux reverse osmosis concentrate and reflux reverse osmosis desalination.

[0068] When the recovery rate of the first reverse osmosis treatment reaches 50-60%, the first valve is opened, and the reflux reverse osmosis concentrate is depressurized through the energy recovery device to obtain the first depressurized brine. Using the first depressurized brine as the draw solution and ultrafiltration water as the diluent, the first forward osmosis treatment is performed to obtain the first diluted depressurized brine and the first concentrated ultrafiltration water. The first diluted depressurized brine is returned to the reverse osmosis system for the second reverse osmosis treatment to obtain the circulating reverse osmosis concentrate and the circulating reverse osmosis desalination water. The first concentrated ultrafiltration water is stored in the second storage tank.

[0069] When the operating pressure of the reverse osmosis equipment reaches 77-78 bar, the circulating reverse osmosis concentrate is depressurized through the energy recovery device to obtain the second depressurized brine and the second concentrated ultrafiltration water. The second depressurized brine is used as the draw solution and the ultrafiltration water is used as the diluent for the second forward osmosis treatment to obtain the second diluted depressurized brine and the second concentrated ultrafiltration water. The second diluted depressurized brine is discharged through the drain pipe and the second concentrated ultrafiltration water is stored in the second water storage tank.

[0070] Reverse osmosis desalinated water and concentrated ultrafiltration water are fed into the third mixing tank to obtain fire-fighting water;

[0071] The reverse osmosis freshwater includes initial reverse osmosis freshwater, reflux reverse osmosis freshwater, and circulating reverse osmosis freshwater;

[0072] The concentrated ultrafiltration water includes first concentrated ultrafiltration water and second concentrated ultrafiltration water.

[0073] This invention involves mixing urea-containing waste liquid and alkaline reagents in a heating tank to obtain ammonia and carbon dioxide.

[0074] In one embodiment of the present invention, the alkaline reagent includes NaOH. In this invention, the urea-containing waste liquid may include nitrogenous waste collected from toilets, such as human waste urine. In one embodiment of the present invention, the molar ratio of NaOH to urea can be 1:1 to 1.1; the NaOH is preferably used in the form of a NaOH solution; the concentration of the NaOH solution can be 10 wt.%. In one embodiment of the present invention, the mixing method can be stirring, and the stirring speed can be 200 to 300 rpm.

[0075] In one embodiment of the present invention, the temperature of the catalytic decomposition can be 50–70°C, specifically 60°C, and the catalytic decomposition time can be 1–2 hours, specifically 1 hour, 1.5 hours, or 2 hours. In this invention, setting the catalytic decomposition temperature to the above-mentioned temperatures ensures the release of ammonia while avoiding ammonia loss due to excessively high temperatures. Setting the catalytic decomposition reaction time to 1–2 hours ensures complete decomposition of urea. Furthermore, the present invention uses a heating tank to control the reaction temperature, which improves overall energy utilization efficiency and avoids energy waste.

[0076] In one embodiment of the present invention, the pH value of the reaction system for the catalytic decomposition reaction can be >9, specifically 11.5 to 14. In this invention, maintaining the pH value of the reaction system above 9 promotes the release of ammonia. Furthermore, during the catalytic decomposition process, the pH value of the system is monitored in real time using a pH sensor; if the pH falls below 10.5, NaOH solution is added.

[0077] In this invention, the equation for the catalytic decomposition reaction is as follows:

[0078] CO(NH2)2 + H2O → 2NH3 + CO2

[0079] After obtaining ammonia, the present invention introduces ammonia into an ammonium sulfate synthesis tower, mixes it with a first sulfuric acid solution, and carries out a synthesis reaction to obtain ammonium sulfate.

[0080] In one embodiment of the present invention, in the synthesis reaction, the concentration of the first sulfuric acid solution can be 10-20 wt.%, specifically 15 wt.%; the molar ratio of NH3 to H2SO4 in the sulfuric acid aqueous solution can be 3-5:1. In another embodiment of the present invention, the ammonia gas preferably enters the ammonium sulfate synthesis tower from bottom to top, and the sulfuric acid aqueous solution preferably is sprayed from top to bottom to react with the ammonia gas.

[0081] In this invention, the equation for the synthetic reaction is as follows:

[0082] 2NH3 + H2SO4 → (NH4)2SO4

[0083] In this invention, agricultural phosphorus-containing wastewater and a second sulfuric acid solution are mixed in a first mixing tank to carry out a first metathesis reaction, yielding phosphoric acid and calcium sulfate; the agricultural phosphorus-containing wastewater contains Ca(H2PO4)2.

[0084] In one embodiment of the present invention, in the first metathesis reaction, the concentration of the second sulfuric acid solution can be 10-20 wt.%, specifically 15 wt.%; in another embodiment of the present invention, the molar ratio of Ca(H2PO4)2 to H2SO4 in the sulfuric acid aqueous solution can be 1:2.

[0085] In one embodiment of the present invention, the temperature of the first metathesis reaction can be 60–80°C, specifically 70°C; the time of the first metathesis reaction can be 1.5–2 hours, specifically 1.5 hours, 1.8 hours, or 2 hours; in the present invention, the first metathesis reaction is preferably carried out under continuous stirring to mix the reactants and prevent precipitation. In the present invention, setting the temperature of the first metathesis reaction to the above-mentioned range can increase the reaction rate; setting the time of the first metathesis reaction to 1.5–2 hours can ensure complete reaction.

[0086] In this invention, the equation for the first metathesis reaction is as follows:

[0087] Ca(H2PO4)2+2H2SO4→2H3PO4+CaSO 4↓

[0088] In this invention, phosphoric acid, ammonium sulfate and ammonia are introduced into a second mixing tank to carry out a combination reaction and a second metathesis reaction to obtain an ammonium dihydrogen phosphate system.

[0089] In one embodiment of the present invention, the ammonia gas is ammonia gas that has not reacted with the first sulfuric acid solution.

[0090] In one embodiment of the present invention, the molar ratio of H3PO4 to NH3 can be 1:1 to 1.1; the molar ratio of H3PO4 to (NH4)2SO4 can be 1:1 to 1.1. By setting the molar ratio of phosphoric acid, ammonium sulfate, and ammonia within the above range, the present invention ensures that the pH value of the materials in the second mixing tank tends to neutralize, preventing damage to subsequent machinery.

[0091] In one embodiment of the present invention, the temperature of the combination reaction and the second metathesis reaction are independently set to 25–40°C, and the time is 0.5–1 h. In this invention, setting the temperature of the combination reaction and the second metathesis reaction to 25–40°C avoids the formation of byproducts due to high temperatures. Setting the reaction time within the above range ensures complete reaction. In this invention, the combination reaction and the second metathesis reaction are preferably carried out under stirring conditions, and the stirring speed can be 300–500 rpm. Setting the stirring speed within the above range avoids the generation of foam from vigorous stirring.

[0092] In this invention, the reaction in the second mixing tank is mainly as follows:

[0093] NH3 + H3PO4 → NH4H2PO4

[0094] (NH4)2SO4+H3PO4→NH4H2PO4+(NH4)HSO4;

[0095] In this invention, ammonium dihydrogen phosphate (NH4H2PO4) is a highly efficient fire extinguishing material that can react rapidly in a fire to form chemical reaction products (ammonia, water vapor, etc.) that help extinguish the fire.

[0096] The ammonium dihydrogen phosphate system described in this invention is precipitated in a sedimentation tank and then subjected to ultrafiltration by an ultrafiltration device to obtain ultrafiltered water, which is placed in the first water storage tank.

[0097] In one embodiment of the present invention, the ultrafiltration is preferably operated at a pressure of <3 bar, specifically 2 bar. Setting the operating pressure to the above parameters effectively removes solid particles (such as calcium sulfate precipitate) and colloids, while ensuring the filtration of NH4H2PO4 and small molecule dissolved substances. In this invention, the salt in the ultrafiltered water is mainly NH4H2PO4.

[0098] This invention introduces seawater into a reverse osmosis system for initial reverse osmosis treatment, yielding initial reverse osmosis concentrate and initial reverse osmosis desalination. In one embodiment of this invention, the initial reverse osmosis concentrate includes high concentrations of dissolved salts, residual microorganisms, organic matter, and ions retained by the reverse osmosis membrane.

[0099] After obtaining the initial reverse osmosis concentrate, the present invention recirculates the initial reverse osmosis concentrate back to the reverse osmosis system for the first reverse osmosis treatment, resulting in recirculated reverse osmosis concentrate and recirculated reverse osmosis desalination (referred to as recirculation operation mode).

[0100] In this invention, recirculating the initial reverse osmosis concentrate back to the reverse osmosis system for a first reverse osmosis treatment can optimize the recovery rate of the reverse osmosis membrane equipment and increase freshwater production. In this invention, the first reverse osmosis treatment involves multiple cycles of concentration within the reverse osmosis system.

[0101] In one embodiment of the present invention, when the recovery rate of the first reverse osmosis treatment is 50-60%, the first valve automatically opens, and the reflux reverse osmosis concentrate is depressurized through the energy recovery device to obtain the first depressurized brine; the first depressurized brine is used as the draw liquid and ultrafiltration water is used as the diluent for the first forward osmosis treatment to obtain the first diluted depressurized brine and the first concentrated ultrafiltration water; the first diluted depressurized brine is returned to the reverse osmosis system for the second reverse osmosis treatment to obtain the circulating reverse osmosis concentrate and the circulating reverse osmosis desalination water; the first concentrated ultrafiltration water is stored in the second water storage tank (referred to as the circulating operation mode).

[0102] In this invention, the second reverse osmosis process involves multiple cycles of concentration via a reverse osmosis system.

[0103] In this invention, after the reflux reverse osmosis concentrate is depressurized by the energy recovery device, the depressurized brine reaches the forward osmosis membrane at a pressure close to 0 bar. It is then diluted with ultrafiltration water as the forward osmosis draw solution. The resulting first diluted depressurized brine is refluxed back to the reverse osmosis system feed water side and mixed with seawater for reverse osmosis.

[0104] In one embodiment of the present invention, the forward osmosis device uses a composite membrane with a pore size of <1 nm; the membrane flux of the forward osmosis membrane can be 5–20 L / (m²). 2 *h), specifically 5L / (m 2 *h), 10L / (m 2 *h), 15L / (m 2 *h) or 20L / (m 2 *h). In this invention, the ultrafiltration water is used as the feed liquid and introduced into the feed side of the forward osmosis equipment. At the same time, depressurized brine is used as the driving liquid. Under the action of osmotic pressure difference, water molecules in the feed liquid migrate to the driving liquid side to obtain concentrated ultrafiltration water (the concentration of ammonium dihydrogen phosphate is increased).

[0105] When the operating pressure of the reverse osmosis equipment reaches 77-78 bar, the circulating reverse osmosis concentrate is depressurized through the energy recovery device to obtain the second depressurized brine and the second concentrated ultrafiltration water. The second depressurized brine is used as the draw solution and the ultrafiltration water is used as the diluent for the second forward osmosis treatment to obtain the second diluted depressurized brine and the second concentrated ultrafiltration water. The second diluted depressurized brine is discharged through the drain pipe and the second concentrated ultrafiltration water is stored in the second water storage tank (referred to as direct discharge operation mode).

[0106] In one embodiment of the present invention, after the circulating reverse osmosis concentrate is depressurized through the energy recovery device, the pressure of the depressurized brine that reaches the forward osmosis equipment is >0 bar, specifically 4 bar. It can be used as a flushing fluid to flush out scale and fouling on the forward osmosis membrane before being discharged.

[0107] This invention introduces reverse osmosis freshwater and concentrated ultrafiltration water into a third mixing tank to obtain fire-fighting water; the reverse osmosis freshwater includes initial reverse osmosis freshwater, reflux reverse osmosis freshwater, and circulating reverse osmosis freshwater; the concentrated ultrafiltration water includes first concentrated ultrafiltration water and second concentrated ultrafiltration water.

[0108] In one embodiment of the present invention, the mass concentration of ammonium dihydrogen phosphate (NH4H2PO4) in the fire-fighting water can be 5-10%. In another embodiment of the present invention, the fire-fighting water in the third mixing tank can be used directly for extinguishing wildfires, or it can be stored in a water storage tank for later use.

[0109] In terms of chemical synthesis, this invention utilizes a multi-step reaction process to prepare effective fire-extinguishing components such as ammonium phosphate. For example, ammonia in urine is converted into ammonium sulfate, which then undergoes a metathesis reaction with phosphoric acid and ammonia to produce ammonium dihydrogen phosphate, which is used for fire extinguishing. This in-situ preparation method of fire-extinguishing chemicals organically combines wastewater treatment and fire-extinguishing agents.

[0110] In addition, this invention utilizes a combined forward and reverse osmosis desalination process. Compared with existing technologies, this solution does not simply add fire extinguishing agents after RO seawater desalination. Instead, it uses the FO process to exchange water between seawater and ultrafiltered water (containing fire extinguishing agents). This reduces the salinity of the seawater and concentrates the effective fire extinguishing agents in the ultrafiltered water. This process breaks through the limitations of traditional seawater desalination or wastewater concentration operating independently, achieving integrated treatment.

[0111] The device provided by this invention can integrate multiple functions (waste resource utilization + seawater desalination + fire extinguishing agent synthesis), which not only reduces the pressure of pollutant discharge (such as direct discharge of urine and agricultural wastewater), but also alleviates the problem of insufficient fresh water for fire fighting and reduces the corrosive hazards of direct seawater fire extinguishing.

[0112] This invention expands the goal of wastewater treatment from "meeting discharge standards" to producing functional products (firefighting water), pioneering a circular economy-style firefighting water supply model. Furthermore, the resulting firefighting water contains a certain amount of salts such as ammonium dihydrogen phosphate (which can inhibit reignition and cool the fire scene), making it not only superior to pure water in firefighting performance but also relatively friendly to soil and vegetation (it can be used as fertilizer after firefighting, avoiding secondary hazards caused by residual seawater salt).

[0113] In summary, this device simultaneously realizes three functions: waste utilization, seawater desalination, and fire extinguishing agent preparation, making fire-fighting water production more sustainable. Furthermore, through process combination, it achieves multi-objective synergy and has high application potential.

[0114] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.

[0115] Example 1

[0116] Waste urine and 10 wt.% NaOH solution were mixed in a heating tank. The molar ratio of urea to NaOH in the waste urine was 1:1.1. Catalytic decomposition was carried out in the heating tank at 60°C for 2 hours to obtain NH3 and CO2.

[0117] The obtained ammonia gas is introduced from the bottom of the ammonium sulfate synthesis tower, and a sulfuric acid solution with a concentration of 15 wt.% is sprayed downward from the top of the ammonium sulfate synthesis tower. The ammonia gas and the sulfuric acid solution (molar ratio of NH3 to H2SO4 is 3:1) undergo a synthesis reaction to obtain ammonium sulfate.

[0118] Agricultural waste liquid (containing Ca(H2PO4)2) is passed into a first mixing tank, and a sulfuric acid solution with a concentration of 15 wt.% is added to the first mixing tank; the molar ratio of Ca(H2PO4)2 to H2SO4 is 1:2; in the first mixing tank, Ca(H2PO4)2 and H2SO4 undergo a first metathesis reaction at a temperature of 60°C for 2 hours, yielding H3PO4 and CaSO4;

[0119] Phosphoric acid, ammonium sulfate, and ammonia (the molar ratio of phosphoric acid, ammonium sulfate, and ammonia was 1:1:1, and the ammonia was unreacted with the sulfuric acid solution) were introduced into a second mixing tank, and a combination reaction and a second metathesis reaction were carried out at 25°C for 1 hour to obtain an ammonium dihydrogen phosphate system.

[0120] The ammonium phosphate system was passed into an ultrafiltration device for ultrafiltration. The ultrafiltration membrane was a polyamide membrane with an average pore size of 0.05 μm. The operating pressure of the ultrafiltration device was 2 bar, and ultrafiltered water was obtained.

[0121] At 25℃, 0.4m of water with a salinity of 30,000 mg / L was... 3 Seawater is introduced into four parallel reverse osmosis pressure vessels (each pressure vessel is equipped with three reverse osmosis membrane elements, and the effective membrane area (material is polyamide composite membrane) of each membrane element is 7.43 m²). 2 The total membrane area of ​​the system is 89.16 m². 2 The water flux is 1.65 L / (m²). 2 *h*bar), salt flux is 0.113 L / (m 2 *h), the total influent flow rate is 2m³. 3 / h, circulating concentrate flow rate is 4m³ / h 3 The concentration is carried out three times per hour (see operating pressure for example). Figure 2 Salinity see Figure 3 After the first concentration (operating pressure of 35.8 bar), the initial reverse osmosis is completed (one concentration is recorded by passing through 4 reverse osmosis pressure vessels, the 4 reverse osmosis pressure vessels are in parallel, and the operating pressure of the membrane element and the salinity of the influent and effluent are the same in each reverse osmosis pressure vessel), resulting in initial reverse osmosis concentrate (salinity of 42,860 mg / L) and initial reverse osmosis desalination (passed into the third mixing tank);

[0122] The initial reverse osmosis concentrate is further concentrated twice to obtain reflux reverse osmosis concentrate and reflux reverse osmosis permeate (introduced into the third mixing tank) with a salinity of 75,605 mg / L. When the reflux reverse osmosis permeate accounts for 60% of the feed water mass (i.e., the reverse osmosis recovery rate reaches 60%), the first valve automatically opens. The reflux reverse osmosis concentrate is depressurized through the energy recovery device, and the resulting depressurized brine is used as the draw solution. Ultrafiltration water is used as the diluent for forward osmosis treatment (membrane flux is 10 L / (m²)). 2 *h), the reflux reverse osmosis concentrate is diluted by 10%, while the ultrafiltration water is concentrated to obtain diluted depressurized brine and concentrated ultrafiltration water (stored in the second storage tank). The mixture of diluted depressurized brine and seawater (salinity 39,872 mg / L) enters the reverse osmosis system for reverse osmosis treatment with a target recovery rate of 70% (percentage of circulating reverse osmosis freshwater to the mixture) (concentration 5 times, the concentration operating pressure is shown in [reference]). Figure 4 Salinity see Figure 5 After the first concentration (operating pressure 56.1 bar), the salinity increases to 58,383 mg / L. Subsequently, it undergoes four more concentrations (operating pressure 77.5 bar) to obtain circulating reverse osmosis concentrate and circulating reverse osmosis desalination (which is then fed into the third mixing tank). At this point, the circulating reverse osmosis concentrate is depressurized through an energy recovery device and then diluted by 10% using ultrafiltration water through a forward osmosis system to obtain depressurized diluted brine with a salinity of 86,207 mg / L and concentrated ultrafiltration water. The depressurized diluted brine with a salinity of 86,207 mg / L is discharged through a drain pipe, while the concentrated ultrafiltration water is stored in the second storage tank.

[0123] The initial reverse osmosis freshwater, the reflux reverse osmosis freshwater, the circulating reverse osmosis freshwater, and the concentrated ultrafiltration water in the second storage tank are mixed in a third mixing tank to obtain fire-fighting water.

[0124] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. An apparatus for producing fire-fighting water, comprising a urea-containing wastewater treatment unit, an agricultural wastewater treatment unit, and a seawater treatment unit; The urea-containing waste liquid treatment unit includes a heating tank and an ammonium sulfate synthesis tower connected to the heating tank; The agricultural wastewater treatment unit includes a first mixing tank, a second mixing tank, a sedimentation tank, an ultrafiltration device, and a first water storage tank connected in sequence; the outlet of the ammonium sulfate synthesis tower is connected to the inlet of the second mixing tank; the first mixing tank is used to mix agricultural phosphorus-containing wastewater and a second sulfuric acid solution to cause a first metathesis reaction to obtain phosphoric acid and calcium sulfate; The second mixing tank is used to mix phosphoric acid, ammonium sulfate and ammonia to cause a combination reaction and a second metathesis reaction to obtain an ammonium dihydrogen phosphate system. The seawater treatment unit includes a first module, a second module, a second water storage tank, and a third mixing tank; The first module includes a reverse osmosis system, an energy recovery device connected to the reverse osmosis system, a forward osmosis device connected to the energy recovery device, and a high-pressure pump connected to the forward osmosis device; the high-pressure pump is connected to the reverse osmosis system; and the high-pressure pump and the energy recovery device are connected in series. The second module includes a low-pressure pump; the low-pressure pump is connected to the reverse osmosis system of the first module to form a loop; the reverse osmosis system is connected to the low-pressure pump and the energy recovery device respectively through a first valve; The third mixing tank is connected to the forward osmosis equipment of the first module through the second water storage tank; The outlet of the reverse osmosis system is connected to the inlet of the third mixing tank.

2. The apparatus of claim 1, wherein, The ultrafiltration device is equipped with an ultrafiltration membrane; the pore size of the ultrafiltration membrane is 0.01~0.1 μm; the molecular weight cutoff of the ultrafiltration membrane is 1000~500000 Da; The forward osmosis device is provided with a forward osmosis membrane; the pore size of the forward osmosis membrane is <1nm; the membrane flux of the forward osmosis membrane is 5~20 L / (m 2 h).

3. The apparatus of claim 1, wherein, The reverse osmosis system includes multiple reverse osmosis pressure vessels connected in parallel; each reverse osmosis pressure vessel is equipped with multiple membrane elements; the number of reverse osmosis pressure vessels is ≥4; and the number of membrane elements is ≥3.

4. The apparatus of claim 1, wherein, The reverse osmosis system is equipped with a reverse osmosis membrane; the reverse osmosis membrane is a polyamide composite membrane; the pore size of the reverse osmosis membrane is <0.1nm.

5. The apparatus of claim 1, wherein, The forward osmosis equipment is connected to the drain pipe and the high-pressure pump via a second valve.

6. A method for preparing fire-fighting water using the apparatus according to any one of claims 1 to 5, comprising the following steps: Urea-containing waste liquid and alkaline reagent are mixed in a heating tank to carry out a catalytic decomposition reaction, yielding ammonia and carbon dioxide; Ammonia gas is introduced into the ammonium sulfate synthesis tower and mixed with the first sulfuric acid solution to carry out the synthesis reaction and obtain ammonium sulfate. Agricultural phosphorus-containing wastewater and a second sulfuric acid solution are mixed in a first mixing tank to carry out a first metathesis reaction, yielding phosphoric acid and calcium sulfate; the agricultural phosphorus-containing wastewater contains Ca(H2PO4)2. Phosphoric acid, ammonium sulfate and ammonia are introduced into a second mixing tank to carry out a combination reaction and a second metathesis reaction to obtain an ammonium dihydrogen phosphate system. After the ammonium dihydrogen phosphate system is precipitated in a sedimentation tank, it is then ultrafiltered through an ultrafiltration device to obtain ultrafiltered water, which is placed in the first water storage tank. Seawater is fed into a reverse osmosis system for initial reverse osmosis treatment to obtain initial reverse osmosis concentrate and initial reverse osmosis desalination. The initial reverse osmosis concentrate is returned to the reverse osmosis system for the first reverse osmosis treatment, resulting in reflux reverse osmosis concentrate and reflux reverse osmosis desalination. When the recovery rate of the first reverse osmosis treatment is 50-60%, the first valve is opened, and the reflux reverse osmosis concentrate is depressurized through the energy recovery device to obtain the first depressurized brine; the first depressurized brine is used as the draw solution and ultrafiltration water is used as the diluent to perform the first forward osmosis treatment to obtain the first diluted depressurized brine and the first concentrated ultrafiltration water. The first diluted depressurized brine is returned to the reverse osmosis system for a second reverse osmosis treatment to obtain circulating reverse osmosis concentrate and circulating reverse osmosis desalination; the first concentrated ultrafiltration water is stored in the second water storage tank. When the operating pressure of the reverse osmosis equipment reaches 77~78 bar, the circulating reverse osmosis concentrate is depressurized for the second time through the energy recovery device to obtain the second depressurized brine and the second concentrated ultrafiltration water; the second depressurized brine is used as the draw liquid and the ultrafiltration water is used as the diluent to perform the second forward osmosis treatment to obtain the second diluted depressurized brine and the second concentrated ultrafiltration water. The second diluted depressurized brine is discharged through the drain pipe, and the second concentrated ultrafiltration water is stored in the second storage tank; Reverse osmosis desalinated water and concentrated ultrafiltration water are fed into the third mixing tank to obtain fire-fighting water; The reverse osmosis freshwater includes initial reverse osmosis freshwater, reflux reverse osmosis freshwater, and circulating reverse osmosis freshwater; The concentrated ultrafiltration water includes first concentrated ultrafiltration water and second concentrated ultrafiltration water.

7. The preparation method according to claim 6, characterized in that, The alkaline reagent includes NaOH; the temperature of the catalytic decomposition reaction is 50~70 ℃, and the catalytic decomposition time is 1~2 h; the pH value of the reaction system of the catalytic decomposition reaction is >9.

8. The production method according to claim 6, wherein The temperature of the first metathesis reaction is 60~80℃; the time of the first metathesis reaction is 1.5~2 h.

9. The preparation method according to claim 6, characterized in that, The combination reaction and the second metathesis reaction are carried out at a temperature of 25~40 °C for a time of 0.5~1 h.

10. The production method according to claim 6, wherein The content of ammonium dihydrogen phosphate in the fire-fighting water is 10~20 wt.%.

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