Method for preparing water mist fire extinguishing agent by washing fly ash with composite potassium salt

Abstract

The invention relates to a method for preparing a water mist fire extinguishing agent by washing fly ash with composite potassium salt. The method comprises the following steps: 1) a fly ash pretreatment module: carrying out vacuum pyrolysis on fly ash to obtain pyrolyzed fly ash; mixing the pyrolytic fly ash with hydrochloric acid, and carrying out solid-liquid separation to obtain fly ash washing liquid; adding a chelating agent into the fly ash washing liquid to obtain a first solution; adding a sodium carbonate solution into the first solution, and separating after heating reaction to obtain a second solution; 2) a potassium bicarbonate and sodium bicarbonate composite dry powder purification module: mixing the second solution, ammonia water and an organic alcohol solution, introducing carbon dioxide, stirring and reacting, filtering, cleaning and drying to obtain a sodium bicarbonate and potassium bicarbonate mixed solid; and 3) a potassium acetate and sodium acetate composite fire extinguishing agent preparation module: mixing the mixed solid of sodium bicarbonate and potassium bicarbonate with acetic acid.According to the invention, a novel low-cost water mist additive is prepared by compounding a plurality of alkali metal salts contained in the fly ash washing liquid and a plurality of salts in a fly ash system.

Description

Technical Field

[0001] The invention relates to the field of fire extinguishing agents, and in particular to a method for preparing a fine water mist fire extinguishing agent by washing composite potassium salt with fly ash. Background Art

[0002] Fine water mist has the characteristics of high heat capacity, easy evaporation and cleanliness, high efficiency and low cost. Its protection places include high-risk warehouse scenes such as urban underground integrated pipe corridors, coal mine tunnels, computer rooms, alcohol-based fuel depots, and lithium battery energy storage. Fine water mist will reduce the chemical reaction rate and propagation rate of the flame during the fire extinguishing process, which is conducive to controlling the development of the fire until the fire is extinguished. However, fine water mist fire extinguishing is still a physical fire extinguishing, and its application also has certain limitations. In order to further improve the fire extinguishing efficiency of fine water mist and break through the limitations of its physical effect. Fine water mist fire extinguishing containing additives has both physical and chemical effects, which improves the fire extinguishing efficiency of pure fine water mist. Substances with high fire extinguishing efficiency can be roughly divided into three categories: organic phosphorus compounds, alkali metal compounds, and transition metal salts. Although organic phosphorus compounds (such as pentahydroxy iron, ferrocene, etc.) have good fire extinguishing effects, the substance itself is flammable and highly toxic, and there are many risks and limitations in its use. Ultrafine water mist containing sodium hydroxide and sodium bicarbonate can inhibit the combustion rate of H2 / CH4 / O2 / N2 premixed flames. The fire extinguishing efficiency of water mist containing sodium chloride shows a W-shaped relationship with the concentration of sodium chloride. Studies have found that potassium bromide, potassium acetate, sodium bromide, calcium chloride, potassium lactate, potassium hydroxide, ferrous chloride, etc. can exert better fire extinguishing efficiency within a suitable concentration range. The mechanism of fine water mist fire extinguishing can be summarized as follows: (1) cooling of flames and liquid fuels by droplets; (2) inhibition of combustion reactions by solid particles. For example, potassium chloride reacts with water vapor at high temperature to generate gaseous potassium hydroxide, which can interact with flame free radicals to generate potassium oxides and block the flame chain reaction. The melting point and volatility of potassium salt additives have an important influence on the generation of gaseous KOH, a key component of fire extinguishing. The lower the melting point of potassium salt additives and the stronger the volatility, the greater the possibility of generating gaseous KOH in a water vapor environment. The treatment of fly ash water washing liquid is mainly to remove heavy metals and then recover the inorganic salts therein. The purity of sodium chloride, potassium chloride and calcium chloride industrial salts extracted from fly ash is difficult to meet the standards due to the complex composition of the aqueous solution. At present, there is an urgent need to provide a new type of fly ash water washing secondary salt for the preparation of fine water mist fire extinguishing composite potassium salt additives. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for preparing a fine water mist fire extinguishing agent from a fly ash water-washed composite potassium salt. The present invention utilizes a variety of alkali metal salts contained in the fly ash water-washing liquid, and through the synergistic effect of a variety of salts in the fly ash system, a new low-cost fine water mist additive is prepared, which provides a new idea for the resource utilization of fly ash water-washing salt.

[0004] In a first aspect, the present invention provides a method for preparing a fly ash water-washed composite potassium salt additive, comprising: 1) Fly ash pretreatment module: Pyrolysis: The fly ash is subjected to vacuum pyrolysis to obtain pyrolysis fly ash.

[0005] Acid washing: the pyrolysis fly ash is mixed with hydrochloric acid, and the solid and liquid are separated to obtain a fly ash water washing liquid.

[0006] Stirring and filtering: adding a chelating agent to the fly ash water washing liquid to obtain a first solution; adding a sodium carbonate solution to the first solution, heating for reaction and separating to obtain a second solution.

[0007] 2) Potassium bicarbonate and sodium bicarbonate composite dry powder purification module: the second solution, ammonia water and organic alcohol solution are mixed, carbon dioxide is introduced and stirred for reaction, and the mixture is filtered, washed and dried to obtain a mixed solid of sodium bicarbonate and potassium bicarbonate.

[0008] 3) Preparation module of additive for potassium acetate and sodium acetate composite fire extinguishing agent: the mixed solid of sodium bicarbonate and potassium bicarbonate is mixed with acetic acid, and when the pH value of the solution is 9.2-9.5, a fly ash water-washed composite potassium salt additive is obtained.

[0009] The present invention processes fly ash through specific process steps to obtain a fly ash water-washed composite potassium salt additive with excellent performance. The fly ash is subjected to vacuum pyrolysis to effectively degrade dioxins therein. The fly ash after pyrolysis is subjected to acid washing and solid-liquid separation to extract soluble salts. Then, a chelating agent is added to remove heavy metal impurities in the water washing liquid. By adding a sodium carbonate solution and heating the reaction, calcium and magnesium ions are precipitated to obtain a purified solution. Further, by mixing the solution, ammonia water and an organic alcohol solution and introducing carbon dioxide to stir the reaction, a mixture of sodium bicarbonate and potassium bicarbonate is separated, and by mixing and reacting with a certain concentration of acetic acid, a high-purity fly ash water-washed composite potassium salt additive for fine water mist fire extinguishing agent is obtained.

[0010] Preferably, in step 1), the fly ash is subjected to vacuum pyrolysis at 400-600° C. for 30-60 min, the oxygen concentration is maintained at ≤1%, and the degradation rate of dioxins is not less than 99%.

[0011] Preferably, in step 1), the liquid-to-solid ratio of the pyrolysis fly ash to water is (1.2-1.8) mL:1 g, and the mixture is shaken and mixed for 10-40 min and then vacuum filtered.

[0012] Further preferably, in step 1), the chelating agent is dithiocarbamate and tetramethylthiuram dithiodide, and the mass ratio of the dithiocarbamate and tetramethylthiuram dithiodide is (2-3):(1-2); the ratio of the chelating agent to the fly ash suspension is (1.4-2.0) g:100 mL.

[0013] Further preferably, in step 1), the volume ratio of the first solution to the sodium carbonate solution is (8.5-10):1; and / or the mass concentration of the sodium carbonate solution is 10-15%; and / or, the reaction is stirred at 65-70° C. for 30-40 min, and then centrifuged and filtered.

[0014] Further preferably, in step 2), the volume ratio of the second solution to aqueous ammonia is (10-20):1; the volume ratio of the second solution to the organic alcohol solution is (10-20):(0.25-0.4); the volume concentration of aqueous ammonia is 25-30%; the organic alcohol solution is a 45-55% sec-butanol solution; the flow rate of the carbon dioxide is 70-90 L / min, the reaction temperature is 18-20°C, and the stirring reaction is 50-70 min; and the drying temperature is 60-65°C.

[0015] Further preferably, in step 3), the concentration of the acetic acid is 1.5-3%; and / or the volume mass ratio of the acetic acid to the mixed solid of sodium bicarbonate and potassium bicarbonate is (5-7) mL:1 g.

[0016] The present invention can significantly improve the processing effect of each step and the quality of the final product by optimizing the above parameters, thereby improving environmental benefits and economic benefits.

[0017] In a second aspect, the present invention provides a fly ash water-washed composite potassium salt additive obtained by the above-mentioned preparation method.

[0018] In a third aspect, the present invention provides a fly ash water-washed composite potassium salt additive obtained by the above-mentioned preparation method or the use of the above-mentioned fly ash water-washed composite potassium salt additive in the preparation of a fine water mist fire extinguishing agent. The fine water mist fire extinguishing agent prepared using the fly ash water-washed composite potassium salt additive exhibits excellent fire extinguishing performance, reflecting the innovative idea of ​​resource utilization.

[0019] In a fourth aspect, the present invention provides a method for preparing a fine water mist fire extinguishing agent, using the fly ash water-washed composite potassium salt additive obtained by the above-mentioned preparation method to prepare a fine water mist fire extinguishing agent, including the preparation of a potassium acetate and sodium acetate composite fire extinguishing agent and a fine water mist fire extinguishing agent; preferably, comprising: mixing the fly ash water-washed composite potassium salt additive with an anionic surfactant to obtain a potassium acetate and sodium acetate composite fire extinguishing agent; the mass ratio of the fly ash water-washed composite potassium salt additive to the anionic surfactant is (1-9):(0.2-0.6), preferably (3-6):(0.4-0.6), and the potassium acetate and sodium acetate composite fire extinguishing agent is diluted with water and then pumped into a fine water mist generator to obtain a fine water mist fire extinguishing agent.

[0020] Preferably, the volume ratio of the potassium acetate and sodium acetate composite fire extinguishing agent to water is 1:(2-5), preferably 1:(3-4); the fine water mist fire extinguishing agent prepared by this method has a significant fire extinguishing effect. By mixing the fly ash water-washed composite potassium salt additive with an anionic surfactant (potassium succinate sulfonate), the fire extinguishing efficiency of the fine water mist fire extinguishing agent is effectively improved, the liquid surface tension is reduced, the atomization effect of the fine water mist in the flame is enhanced, and the decomposition of potassium salt at high temperature is promoted to release active potassium hydroxide, thereby quickly inhibiting the free radical reaction in the flame and significantly improving the fire extinguishing speed.

[0021] Preferably, the anionic surfactant is potassium succinate sulfonate, and the concentration of potassium succinate sulfonate in the potassium acetate and sodium acetate composite fire extinguishing agent is 0.4-0.6%wt. Potassium succinate sulfonate can achieve the best fire extinguishing effect of the fine water mist fire extinguishing agent provided by the present invention at the preferred concentration, and the proportion of water is controlled within a reasonable range, which can ensure that the water mist particles generated by the fine water mist generator are small enough to effectively cover the flame surface, and provide a wider fire extinguishing coverage and higher fire extinguishing efficiency.

[0022] In a fifth aspect, the present invention provides a fine water mist fire extinguishing agent obtained by the above preparation method.

[0023] The present invention provides a method for preparing a fine water mist fire extinguishing agent from potassium-sodium complex salt produced as a by-product of fly ash washing. The method utilizes a variety of alkali metal salts contained in the fly ash washing liquid to prepare a novel low-cost fine water mist additive through the synergistic effect of the various salts in the fly ash system, thereby providing a new idea for the resource utilization of fly ash washing salt, having low cost and being suitable for a variety of fire extinguishing application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of a module flow for preparing a fine water mist fire extinguishing agent from potassium-sodium double salt produced as a by-product of fly ash washing provided in an embodiment of the present invention.

[0026] Figure 2 A schematic diagram of the process flow for preparing a fine water mist fire extinguishing agent from potassium-sodium double salt produced as a by-product of fly ash washing provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods. If no specific techniques or conditions are specified in the examples, they are all conventional methods or the techniques or conditions described in the literature in this field, or according to the product instructions. If the manufacturers of the reagents and instruments are not specified, they are all conventional products that can be purchased through regular channels.

[0029] In the present invention, the specific source of fly ash is not limited. In the embodiment of the present invention, the mainstream flue gas treatment process of the waste incineration plant is SNCR+semi-dry method+dry method+activated carbon+bag filter, and the fly ash comes from the bottom ash of the semi-dry spray tower and the powder collected by the bag filter, and the main components include CaSO3, Ca(OH)2, CaCO3, CaClOH, NaCl, KCl, CaSO4 and SiO2.

[0030] The present invention will be further described below with reference to the embodiments.

[0031] Example 1 This embodiment provides a fly ash water-washed composite potassium salt additive and a fine water mist fire extinguishing agent prepared therefrom, the process is as follows: Figure 1 and Figure 2 As shown, the specific preparation steps are as follows: 1) Degradation of dioxins The fly ash is sent into the dioxin vacuum pyrolysis furnace, the temperature is 500±25℃, the pyrolysis residence time is 45±5min, the oxygen volume concentration in the furnace is not higher than 1%, and the dioxin degradation rate is not lower than 99%. When the dioxin residue content is lower than 50ng-TEQ / kg, proceed to the next step.

[0032] 2) Pickling Step (1) The fly ash after pyrolysis and hydrochloric acid (0.4 mol / L) were placed in a screw-cap container and mixed at a liquid-to-solid ratio of 1.5 mL / g. After sufficient shaking and mixing for 15 minutes, the water washing liquid was vacuum filtered to obtain a fly ash water washing liquid after solid-liquid separation. The main components of the fly ash water washing liquid are shown in the following table.

[0033] Table 1 Main components and contents of fly ash washing liquid

[0034] 3) Heavy metal removal A chelating agent (dithiocarbamate and tetramethylthiuram disulfide, mass ratio of 2:1) was added to the fly ash water wash obtained in step (2) to remove heavy metals, and the ratio of chelating agent to fly ash water wash was 1.7:100 g / mL. The heavy metal concentration was measured, and the removal rates of five heavy metals, Cd, Cu, Mn, Pb, and Zn, reached 99%, 92%, 92%, 99%, and 95%, respectively. Solution 3 was obtained by centrifugal filtration.

[0035] 4) Precipitation of calcium and magnesium Sodium carbonate solution (mass concentration 12.5%, sodium carbonate grade ≥ 99.5%) was added to the solution 3 obtained in step (3) to precipitate calcium and magnesium. The volume ratio of solution 3 to sodium carbonate solution was 9:1. The reaction was carried out at a constant temperature (temperature 68±1°C). The reaction was fully stirred for 35 minutes and centrifuged to obtain a sodium-potassium mixed solution 4. The Ca removal rate was ≥ 99.98%, and n(Na) / n(K) = 1.35±0.05.

[0036] 5) Separate the sodium bicarbonate and potassium bicarbonate mixture Ammonia water (volume concentration 30%, volume ratio of ammonia water to sodium potassium mixed solution 4 is 1:15) and organic alcohol solution (sec-butyl alcohol, concentration 50%, volume ratio of ammonia water to sodium potassium mixed solution 4 is 0.35:15) are added to the sodium potassium mixed solution 4 obtained in step (4), carbon dioxide gas is introduced (flow rate 80 L / min, continuously introduced), and the reaction is stirred (stirring time 60 min, reaction temperature controlled at 19° C.). When the crystal product is no longer produced, stirring is stopped, and the solid-liquid mixture is filtered to obtain a filter cake S5 mixture: a mixed solid of sodium bicarbonate and potassium bicarbonate (n(NaHCO3) / n(KHCO3)=(0.98)), the S5 mixture is washed with deionized water, and dried at 65° C. to constant weight to obtain a sodium bicarbonate and potassium bicarbonate mixture S5-2.

[0037] 6) Preparation of composite potassium salt additives and water mist fire extinguishing agents Dilute 20% acetic acid (purity 95%) 10 times, add it to the sodium bicarbonate and potassium bicarbonate mixture S5-2 according to the volume mass ratio of 6mL:1g, stop when the pH value of the solution is 9.5, then obtain the composite sodium potassium additive (composite sodium potassium salt concentration is 3%), add the anionic surfactant potassium succinate sulfonate (the concentration of the anionic surfactant in the mixture is 0.4%wt), and the mass ratio of the composite sodium potassium additive to the anionic surfactant is 4.5:0.5. Use a high-speed stirrer to mix well to obtain a potassium acetate and sodium acetate composite fire extinguishing agent. When used, dilute it with water (the volume ratio of the potassium acetate and sodium acetate composite fire extinguishing agent to water is 1:3.5) and pump it into the fine water mist generator. The fine water mist fire extinguishing agent obtained after atomization extinguishes the flame (fire source power 15KW).

[0038] Embodiment 2-4 This embodiment provides a fly ash water-washed composite potassium salt additive and a fine water mist fire extinguishing agent prepared therefrom. The specific preparation steps are the same as those in Example 1, except that the concentration of the composite sodium potassium salt and the concentration of the surfactant in step 6) and the flame power are different, as shown in Table 1.

[0039] Comparative Examples 1-11 The method of Example 1 is the same as that of Example 1, except that the surfactant and additive (composite sodium potassium additive, potassium acetate or sodium acetate) used in step 6) are different, as shown in Table 2.

[0040] Table 2

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a fly ash water-washed composite potassium salt additive, characterized in that: include: 1) Fly ash pretreatment module: Pyrolysis: The fly ash is subjected to vacuum pyrolysis to obtain pyrolysis fly ash; Acid washing: mixing the pyrolysis fly ash with hydrochloric acid, separating the solid and the liquid, and obtaining a fly ash water washing liquid; Stirring and filtering: adding a chelating agent to the fly ash water washing liquid to obtain a first solution; adding sodium carbonate solution to the first solution, heating for reaction and then separating to obtain a second solution; 2) Potassium bicarbonate and sodium bicarbonate composite dry powder purification module: the second solution, ammonia water and organic alcohol solution are mixed, carbon dioxide is introduced and stirred for reaction, and the mixture is filtered, washed and dried to obtain a mixed solid of sodium bicarbonate and potassium bicarbonate; 3) Preparation module of additive for potassium acetate and sodium acetate composite fire extinguishing agent: the mixed solid of sodium bicarbonate and potassium bicarbonate is mixed with acetic acid, and when the pH value of the solution is 9.2-9.5, a fly ash water-washed composite potassium salt additive is obtained.

2. The preparation method according to claim 1, characterized in that: In step 1), the fly ash is subjected to vacuum pyrolysis at 400-600°C for 30-60min, the oxygen concentration is maintained at ≤1%, and the degradation rate of dioxins is not less than 99%.

3. The preparation method according to claim 1 or 2, characterized in that: In step 1), the liquid-to-solid ratio of the pyrolysis fly ash to hydrochloric acid is (1.2-1.8) mL:1 g, the concentration of hydrochloric acid is 0.4±0.1 mol / L, and the mixture is shaken and mixed for 10-40 min and then vacuum filtered.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step 1), the chelating agent is dithiocarbamate and tetramethylthiuram dithiodide, and the mass ratio of the dithiocarbamate and tetramethylthiuram dithiodide is (2-3):(1-2); the ratio of the chelating agent to the fly ash suspension is (1.4-2.0) g:100 mL.

5. The preparation method according to any one of claims 1 to 4, characterized in that: In step 1), the volume ratio of the first solution to the sodium carbonate solution is (8.5-10):1; and / or the mass concentration of the sodium carbonate solution is 10-15%; and / or, the reaction is stirred at 65-70° C. for 30-40 minutes, and then centrifuged and filtered.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In step 2), the volume ratio of the second solution to aqueous ammonia is (10-20):1; the volume ratio of the second solution to the organic alcohol solution is (10-20):(0.25-0.4); the volume concentration of aqueous ammonia is 25-30%; the organic alcohol solution is a 45-55% sec-butyl alcohol solution; the flow rate of the carbon dioxide is 70-90 L / min, the reaction temperature is 18-20°C, and the stirring reaction is 50-70 minutes; the drying temperature is 60-65°C; And / or, in step 3), the concentration of the acetic acid is 1.5-3%; and / or, the volume mass ratio of the acetic acid to the mixed solid of sodium bicarbonate and potassium bicarbonate is (5-7) mL:1 g.

7. The fly ash water-washed composite potassium salt additive obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the fly ash water-washed composite potassium salt additive obtained by the preparation method according to any one of claims 1 to 6 or the fly ash water-washed composite potassium salt additive according to claim 7 in the preparation of a fine water mist fire extinguishing agent.

9. A method for preparing a fine water mist fire extinguishing agent, characterized in that: The fly ash water-washed composite potassium salt additive obtained by the preparation method according to any one of claims 1 to 6 is used to prepare a fine water mist fire extinguishing agent, including the preparation of a potassium acetate and sodium acetate composite fire extinguishing agent and a fine water mist fire extinguishing agent; preferably, it includes: mixing the fly ash water-washed composite potassium salt additive with an anionic surfactant to obtain a potassium acetate and sodium acetate composite fire extinguishing agent, and optionally diluting the potassium acetate and sodium acetate composite fire extinguishing agent with water and pumping it into a fine water mist generator to obtain a fine water mist fire extinguishing agent; preferably, the volume ratio of the potassium acetate and sodium acetate composite fire extinguishing agent to water is 1:(2-5); the mass ratio of the composite sodium potassium additive to the anionic surfactant is (1-9):(0.2-0.6); the anionic surfactant is potassium succinate sulfonate, and in the potassium acetate and sodium acetate composite fire extinguishing agent, the concentration of the potassium succinate sulfonate is 0.4-0.6%wt.

10. The fine water mist fire extinguishing agent obtained by the preparation method according to claim 9.

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