Waste gas treatment method in sodium hypophosphite production process

Abstract

The invention discloses a waste gas treatment method in a sodium hypophosphite production process, and belongs to the technical field of hydrogen phosphide adsorption. The waste gas treatment method in the sodium hypophosphite production process is used for solving the technical problems that in the prior art, a hydrogen phosphide solid adsorbent is low in specific surface area and few in hydrogen phosphide adsorption sites, and the cyclic adsorption performance of the solid adsorbent on hydrogen phosphide needs to be further improved. Comprising the following steps: adding loaded modified carbon powder, modified diatomite, red mud, a foam stabilizer, sodium silicate and purified water into a reaction kettle, stirring at room temperature for 30-50 minutes, adding a foaming agent into the reaction kettle, and stirring for 30-60 seconds to obtain mixed slurry. According to the invention, the composite materials such as the loaded modified carbon powder, the modified diatomite and the red mud are mixed, and the dosage proportion of each component is optimized, so that the specific surface area of the adsorbent microsphere is effectively increased, and the adsorbent microsphere has excellent adsorption capacity and cyclic regeneration performance on hydrogen phosphide in waste gas.

Description

Technical Field

[0001] The invention relates to the technical field of phosphine adsorption, and in particular to a method for treating waste gas in a sodium hypophosphite production process. Background Art

[0002] As an important chemical raw material, sodium hypophosphite is widely used in chemical synthesis, electroplating, food preservation and pesticide manufacturing. In its production process, especially in the production process with yellow phosphorus, calcium oxide and sodium carbonate as raw materials, a large amount of toxic and harmful phosphine waste gas will be produced. Phosphine is a colorless, highly toxic, flammable and explosive gas, which poses a serious threat to the environment and human health. The traditional method of treating phosphine waste gas is mainly to mix it with air in a combustion furnace, burn it to generate phosphoric acid mist, and then absorb it with water in an absorption tower to produce dilute phosphoric acid.

[0003] Prior art, a Chinese invention patent with publication number CN101224378A, discloses a method for treating waste gas in the production process of sodium hypophosphite, the process steps are as follows: collecting and storing phosphine; preparing an aqueous solution with formaldehyde, sulfuric acid or hydrochloric acid in a molar ratio of 8.1-8.2:1; the aqueous solution is pumped into an absorption tower by a corrosion-resistant pump, sprayed downward from the top of the tower, and the phosphine gas in the gas tank is sent into the absorption tower by an air pump, and reacted and synthesized at a temperature of 40-50°C to obtain a tetrakis(hydroxymethyl)phosphonium sulfate or tetrakis(hydroxymethyl)phosphonium chloride aqueous solution. The obtained tetrakis(hydroxymethyl)phosphonium chloride (THPC) product reacts with urea to generate tetrakis(hydroxymethyl)phosphonium chloride-urea primary condensate (THPC-Urea), which can be used as a permanent flame retardant for pure cotton or polyester-cotton and other fabrics, and the phosphine is thoroughly absorbed by formaldehyde, sulfuric acid or hydrochloric acid. Zero emission of toxic gases is achieved.

[0004] However, the existing phosphine waste gas treatment method consumes a large amount of water and produces a large amount of waste liquid when treating the phosphine waste gas. When the phosphine waste gas is recovered, it is affected by the change of the phosphine concentration in the gas. When the phosphine concentration in the waste gas is high, the aqueous solution will not completely adsorb the phosphine in the waste gas, and part of the phosphine will overflow. When the phosphine concentration in the waste gas is low, the aqueous solution cannot adsorb the unsaturated phosphine, resulting in a waste of resources.

[0005] Solid adsorbent adsorption is an emerging adsorption method. Adsorption materials such as activated carbon are often used for adsorption treatment of phosphine due to their good adsorption properties. However, when existing solid adsorbents adsorb phosphine in exhaust gas, they have low specific surface area and few adsorption sites for phosphine. Especially after multiple desorption and recycling cycles, the adsorption capacity of phosphine decreases rapidly. The cyclic adsorption performance of solid adsorbents for phosphine needs to be further improved.

[0006] In view of the technical defects in this aspect, a solution is now proposed. Summary of the invention

[0007] The object of the present invention is to provide a method for treating waste gas in a sodium hypophosphite production process, so as to solve the technical problems in the prior art that the specific surface area of ​​a solid adsorbent for phosphine is low, the number of adsorption sites for phosphine is small, and the cyclic adsorption performance of the solid adsorbent for phosphine needs to be further improved.

[0008] The purpose of the present invention can be achieved through the following technical solutions:

[0009] The method for treating waste gas in the production process of sodium hypophosphite comprises the following steps:

[0010] S1. Add the loaded modified carbon powder, modified diatomaceous earth, red mud, foam stabilizer, sodium silicate and purified water into a reactor, set the stirring speed to 300-400 r / min, stir for 30-50 min at room temperature, increase the stirring speed to 600-700 r / min, add a foaming agent into the reactor, stir for 30-60 s, and obtain a mixed slurry;

[0011] S2, injecting the mixed slurry into a mold, maintaining it at a constant temperature of 55-60°C for 30-40 hours, demolding it, and obtaining adsorbent microspheres with a size of 5-8 mm;

[0012] S3, the adsorbent microspheres are filled into the purification box layer by layer to form several layers of adsorbent beds in the purification box, the temperature of the purification box is raised to 80-90°C, the exhaust gas enters the purification box from the top, is adsorbed by multiple adsorbent beds downward, and is discharged from the outlet pipe at the bottom of the purification box;

[0013] S4. When the phosphine content of the gas in the outlet branch pipe is higher than 1 ppm, the adsorbent bed is replaced and the adsorbent microspheres are recycled to obtain regenerated adsorbent microspheres, and the regenerated adsorbent microspheres are refilled into the purification box, and step S3 is repeated to treat the exhaust gas.

[0014] Furthermore, in step S1, the amount ratio of the loaded modified carbon powder, modified diatomaceous earth, red mud, foam stabilizer, purified water, sodium silicate and foaming agent is 5-7g:2-3g:3-4g:0.1g:6-7g:30-35mL:4-6mL, the foam stabilizer is composed of polyvinyl alcohol and sodium dodecyl sulfate in a weight ratio of 3:1, and the foaming agent is 15-20wt% hydrogen peroxide.

[0015] Furthermore, the cyclic regeneration method in step S4 is: adding the waste adsorbent microspheres and purified water in a dosage ratio of 1g:7mL into the reactor, raising the temperature of the reactor to 60-70°C, stirring for 40-60min, filtering, washing the filter cake with purified water at a temperature of 60-70°C for 3 times, and then drying with nitrogen to obtain regenerated adsorbent microspheres.

[0016] Further, the loaded modified carbon powder is processed by the following steps:

[0017] A1. Add the modified liquid and activated carbon powder into a reactor, perform ultrasonic dispersion for 40-60 min at room temperature, and perform post-treatment to obtain a loaded modified carbon powder precursor;

[0018] A2. Place the loaded modified carbon powder precursor in a nitrogen-protected tubular furnace, increase the temperature of the tubular furnace to 480-520°C at a heating rate of 2°C / min, keep the temperature and calcine for 2-3h, cool down and discharge the material to obtain the loaded modified carbon powder.

[0019] The synthetic reaction mechanism of loaded modified carbon powder is:

[0020] Copper nitrate, iron nitrate, zinc nitrate, lanthanum nitrate and deionized water are mixed in a specific proportion to form a modified liquid containing multiple metal ions. Ultrasonic dispersion is used to promote the uniform distribution and penetration of metal ions in the modified liquid on the surface of activated carbon powder. The metal ions are firmly adsorbed on the surface of the carbon powder through physical adsorption and chemical adsorption. Under high temperature, metal nitrates decompose to produce metal oxides and release gases such as nitrogen oxides, forming a uniform coating or nanoparticles on the surface of the carbon powder, thereby realizing the surface modification of the carbon powder. The metal oxides form a stable chemical bond with the surface of the activated carbon powder to obtain loaded modified carbon powder.

[0021] Furthermore, in step A1, the modified liquid is composed of copper nitrate, iron nitrate, zinc nitrate, lanthanum nitrate and deionized water in a dosage ratio of 1.5-2g:1-1.4g:2-2.6g:1.8-2.4g:100mL, and the dosage ratio of the modified liquid to the activated carbon powder is 5mL:2g. The post-treatment includes: after the reaction is completed, the temperature of the reactor is increased to 70-80°C, and the solvent is evaporated under reduced pressure to obtain a loaded modified carbon powder precursor.

[0022] Further, the activated carbon powder is processed by the following steps:

[0023] B1, washing the walnut shells with water and drying them, and crushing them using a grinder to obtain walnut shell powder with a particle size of 0.3-0.5 cm;

[0024] B2. Place the walnut shell powder in a nitrogen-protected quartz tube, carbonize and roast for 80-100 minutes, and cool naturally to room temperature to obtain walnut shell carbonized powder;

[0025] B3. Add walnut shell carbonized powder and urea into a ball mill, and ball mill for 30-50 minutes to obtain a mixture. Place the mixture into a muffle furnace, increase the temperature of the muffle furnace to 300-350° C., and heat-preserve and roast for 3-4 hours. Post-process to obtain activated carbon powder.

[0026] The synthetic reaction mechanism of activated carbon powder is:

[0027] In a high-temperature environment protected by nitrogen, the organic components in the walnut shell (such as cellulose, hemicellulose, lignin, etc.) are pyrolyzed at high temperature to generate small molecular gases and solid residues - carbon. Ball milling is used to promote the refinement of urea particles and evenly distribute them on the surface of the carbonized powder, thereby improving the interaction between the urea molecules and the surface of the carbonized powder. In a high-temperature environment, urea decomposes to release ammonia or other nitrogen-containing gases. These nitrogen-containing gases react with carbon atoms on the surface of the carbonized powder to form CN bonds, thereby achieving nitride doping. In addition, the roasting process also promotes further activation of the carbonized powder, promotes the formation and expansion of the pore structure, increases the specific surface area of ​​the carbon material, and prepares nitrogen-doped activated carbon powder with a high specific surface area.

[0028] Furthermore, in step B2, the carbonization roasting temperature is 750-850°C; in step B3, the weight ratio of the walnut shell carbonized powder to urea is 3:1-2, and the post-treatment includes: after the roasting is completed, the temperature of the muffle furnace is lowered to room temperature, the solid matter is washed with anhydrous ethanol for 3 times and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and dried to constant weight to obtain activated carbon powder.

[0029] Further, the modified diatomite is processed by the following steps:

[0030] C1. Add diatomaceous earth and activation solution into a reaction kettle and stir. Raise the temperature of the reaction kettle to 70-80°C, keep the temperature for 70-90 minutes, and perform post-treatment to obtain activated diatomaceous earth.

[0031] C2, adding activated diatomite and modified liquid into a reactor and stirring, raising the temperature of the reactor to 90-98°C, keeping the temperature at 65-75°C, and post-treating to obtain a modified diatomite precursor;

[0032] C3. Place the modified diatomite precursor in a tube furnace at a temperature of 500-600° C., calcine for 6-8 hours, and cool naturally to room temperature to obtain modified diatomite.

[0033] The synthetic reaction mechanism of modified diatomite is:

[0034] The nitric acid solution and hydrogen peroxide are mixed to form an activation liquid with strong oxidizing property, which promotes the activation of the diatomite surface under high temperature environment, improves the surface activity of the diatomite, removes some impurities on the diatomite surface, increases its surface roughness and specific surface area, and provides favorable conditions for subsequent surface modification. After the activated diatomite is mixed with the modification liquid, it is hydrolyzed and polycondensed under the catalysis of tetrapropylammonium hydroxide of ethyl orthosilicate to generate a siloxane network structure deposited on the diatomite surface to form a dense silicon dioxide coating. As a strong base, tetrapropylammonium hydroxide can slightly etch the diatomite surface, remove impurities and defects on the surface, make the surface smoother, reduce its surface energy, and improve the stability and corrosion resistance of the material. Through high temperature treatment, the silicon dioxide coating is further solidified to form a stable chemical structure to obtain modified diatomite.

[0035] Further, in step C1, the amount ratio of the diatomite and the activation solution is 1g:7mL, the activation solution is composed of 4-6mol / L nitric acid solution and 10-12wt% hydrogen peroxide in a volume ratio of 5:1, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is reduced to room temperature, suction filtration, the filter cake is washed with purified water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and dried to constant weight to obtain activated diatomite; in step C2, the amount ratio of the activated diatomite and the modifying solution is 1g:4mL, the modifying solution is composed of tetraethyl orthosilicate and 20wt% tetrapropylammonium hydroxide aqueous solution in a weight ratio of 2:3.5, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is reduced to room temperature, suction filtration, the filter cake is washed with purified water 6-8 times and then dried, the filter cake is transferred to a drying oven at a temperature of 75-85°C, and dried to constant weight to obtain a modified diatomite precursor.

[0036] The present invention has the following beneficial effects:

[0037] 1. The waste gas treatment method in the production process of sodium hypophosphite provided by the present invention uses walnut shell as raw material, and prepares nitride-doped porous activated carbon powder through high-temperature carbonization and urea activation. The carbon powder is loaded and modified by a metal nitrate solution to increase the surface activity and adsorption sites of the carbon powder. These metal ions can chemically adsorb phosphine to enhance the adsorption capacity. Diatomaceous earth itself has a porous structure. After being activated by nitric acid and hydrogen peroxide, its pore structure is more developed and its specific surface area is increased. It is compounded with the loaded modified carbon powder to further increase the specific surface area of ​​the adsorbent microspheres. The surface performance and stability of the adsorbent microspheres are further enhanced by modification with tetraethyl orthosilicate and tetrapropylammonium hydroxide, which is beneficial to the improvement of the adsorption performance. The loaded modified carbon powder, modified diatomaceous earth and red mud and other composite materials are mixed to form adsorbent microspheres with multi-level pore structures and multiple adsorption sites. By optimizing the treatment process of waste gas, the adsorption capacity and recycling regeneration performance of the adsorbent microspheres for phosphine in the waste gas are improved. In addition, the present invention provides The provided method for treating waste gas in the production process of sodium hypophosphite is as follows: by selecting walnut shells which are porous in themselves as raw materials, after high-temperature carbonization treatment and urea nitridation treatment, the pore structure is more developed, the specific surface area of ​​the material is increased, the decomposition products of urea react with the surface of carbon powder at high temperature, polar functional groups are introduced on the carbon powder, and the affinity of the activated carbon powder for polar molecules such as phosphine is increased; after the metal ions are loaded on the activated carbon powder, the surface will have a certain charge and coordination ability; as a polar molecule, the lone pair of electrons on the phosphorus atom of the phosphine molecule can form a coordination bond with the metal ion, thereby chemical adsorption occurs, which is beneficial to the stable capture of phosphine; a variety of metal ions occupy different adsorption sites on the surface of the activated carbon powder, thereby optimizing the adsorption path and efficiency of phosphine; and copper and iron in the loaded metals have good catalytic activity, which can catalyze the oxidation reaction of phosphine; when a variety of metals coexist, the metal ions promote the catalytic effect between each other, thereby improving the conversion rate and removal efficiency of phosphine. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only 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.

[0039] Figure 1 It is a schematic diagram of the process flow of waste gas treatment in the present invention;

[0040] Figure 2 It is the XRD diagram of the modified diatomite in the present invention.

[0041] In the figure: 100, purification box; 200, air inlet pipe; 300, air outlet pipe. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than 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.

[0043] The average degree of polymerization of polyvinyl alcohol in the present application is 2400-2500 and the viscosity is 40.0-65.0.

[0044] Example 1

[0045] This embodiment provides a method for preparing adsorbent microspheres for waste gas treatment in a sodium hypophosphite production process, comprising the following steps:

[0046] S1. Preparation of activated carbon powder

[0047] The walnut shells were washed with water and dried, and then crushed using a grinder to obtain walnut shell powder with a particle size of 0.3-0.5 cm;

[0048] The walnut shell powder was placed in a nitrogen-protected quartz tube, the temperature of the quartz tube was raised to 750°C, carbonized and roasted for 80 minutes, and then naturally cooled to room temperature to obtain walnut shell carbonized powder;

[0049] The carbonized walnut shell powder and urea were added into a ball mill in a weight ratio of 3:1 and ball-milled for 30 minutes to obtain a mixture;

[0050] The mixture was placed in a muffle furnace, the temperature of the muffle furnace was increased to 300°C, and the mixture was kept warm for 3 hours. After the calcination was completed, the temperature of the muffle furnace was lowered to room temperature. The solid was washed three times with anhydrous ethanol and then dried. The filter cake was transferred to a drying oven at a temperature of 70°C and dried to constant weight to obtain activated carbon powder.

[0051] S2. Preparation of loaded modified carbon powder

[0052] Copper nitrate, iron nitrate, zinc nitrate, lanthanum nitrate and deionized water were mixed uniformly in a dosage ratio of 1.5 g: 1 g: 2 g: 1.8 g: 100 mL to obtain a modified solution for later use;

[0053] The modified liquid and activated carbon powder were added into the reactor at a ratio of 5 mL:2 g, and ultrasonically dispersed for 40 min at room temperature. The temperature of the reactor was raised to 70° C., and the solvent was evaporated under reduced pressure to obtain a loaded modified carbon powder precursor.

[0054] The loaded modified carbon powder precursor was placed in a nitrogen-protected tubular furnace, the temperature of the tubular furnace was increased to 480°C at a heating rate of 2°C / min, and the precursor was kept warm and calcined for 2h, then cooled and discharged to obtain the loaded modified carbon powder.

[0055] S3. Preparation of modified diatomite

[0056] 4 mol / L nitric acid solution and 10 wt % hydrogen peroxide were mixed uniformly in a volume ratio of 5:1 to obtain an activation solution for later use;

[0057] Add diatomite and activation solution in a ratio of 1 g:7 mL into a reactor and stir, raise the temperature of the reactor to 70°C, keep the reaction for 70 minutes, lower the temperature of the reactor to room temperature, filter, wash the filter cake with purified water until it is neutral, and then drain, transfer the filter cake to a drying oven at 70°C, and dry to constant weight to obtain activated diatomite;

[0058] Ethyl orthosilicate and 20 wt % tetrapropylammonium hydroxide aqueous solution are mixed uniformly in a weight ratio of 2:3.5 to obtain a modified solution for later use;

[0059] Activated diatomite and modified liquid were added into the reactor in a ratio of 1 g: 4 mL and stirred. The temperature of the reactor was raised to 90°C and kept at 65°C for reaction. The temperature of the reactor was lowered to room temperature and filtered. The filter cake was washed with purified water for 6 times and then dried. The filter cake was transferred to a drying oven at 75°C and dried to constant weight to obtain a modified diatomite precursor.

[0060] The modified diatomite precursor was placed in a tubular furnace at a temperature of 500° C., calcined for 6 hours, and naturally cooled to room temperature to obtain modified diatomite.

[0061] S4. Preparation of mixed slurry

[0062] Mix polyvinyl alcohol and sodium lauryl sulfate in a weight ratio of 3:1 to obtain a foam stabilizer for later use;

[0063] Weigh: 50 g of loaded modified carbon powder, 20 g of modified diatomaceous earth, 30 g of red mud, 1 g of foam stabilizer, 60 g of sodium silicate and 300 mL of purified water and add them into a reactor, set the stirring speed to 300 r / min, stir at room temperature for 30 min, increase the stirring speed to 600 r / min, add 40 mL of 15 wt% hydrogen peroxide to the reactor, stir for 30 s, and obtain a mixed slurry.

[0064] S5. Preparation of adsorbent microspheres

[0065] The mixed slurry was injected into a mold, maintained at a constant temperature of 55°C for 30 hours, and demolded to obtain adsorbent microspheres with a size of 5-8 mm.

[0066] Example 2

[0067] This embodiment provides a method for preparing adsorbent microspheres for waste gas treatment in a sodium hypophosphite production process, comprising the following steps:

[0068] S1. Preparation of activated carbon powder

[0069] The walnut shells were washed with water and dried, and then crushed using a grinder to obtain walnut shell powder with a particle size of 0.3-0.5 cm;

[0070] The walnut shell powder was placed in a nitrogen-protected quartz tube, the temperature of the quartz tube was raised to 800°C, carbonized and roasted for 90 minutes, and then naturally cooled to room temperature to obtain walnut shell carbonized powder;

[0071] The carbonized walnut shell powder and urea were added into a ball mill in a weight ratio of 2:1 and ball-milled for 40 minutes to obtain a mixture;

[0072] The mixture was placed in a muffle furnace, the temperature of the muffle furnace was increased to 325°C, and the mixture was kept warm for 3.5 hours. After the calcination was completed, the temperature of the muffle furnace was lowered to room temperature. The solid was washed three times with anhydrous ethanol and then dried. The filter cake was transferred to a drying oven at a temperature of 75°C and dried to constant weight to obtain activated carbon powder.

[0073] S2. Preparation of loaded modified carbon powder

[0074] Copper nitrate, iron nitrate, zinc nitrate, lanthanum nitrate and deionized water were mixed uniformly in a dosage ratio of 1.7 g: 1.2 g: 2.3 g: 2.1 g: 100 mL to obtain a modified solution for later use;

[0075] The modified liquid and activated carbon powder were added into the reactor at a ratio of 5 mL:2 g, and ultrasonically dispersed for 50 min at room temperature. The temperature of the reactor was raised to 75°C, and the solvent was evaporated under reduced pressure to obtain a loaded modified carbon powder precursor.

[0076] The loaded modified carbon powder precursor was placed in a nitrogen-protected tubular furnace, the temperature of the tubular furnace was increased to 500°C at a heating rate of 2°C / min, and the precursor was kept warm and calcined for 2.5 hours, then cooled and discharged to obtain the loaded modified carbon powder.

[0077] S3. Preparation of modified diatomite

[0078] 5 mol / L nitric acid solution and 11 wt % hydrogen peroxide were mixed uniformly in a volume ratio of 5:1 to obtain an activation solution for later use;

[0079] Add diatomite and activation solution in a ratio of 1 g:7 mL into a reactor and stir, raise the temperature of the reactor to 75°C, keep the reaction for 80 minutes, lower the temperature of the reactor to room temperature, filter, wash the filter cake with purified water until it is neutral, and then drain, transfer the filter cake to a drying oven at 75°C, and dry to constant weight to obtain activated diatomite;

[0080] Ethyl orthosilicate and 20 wt % tetrapropylammonium hydroxide aqueous solution are mixed uniformly in a weight ratio of 2:3.5 to obtain a modified solution for later use;

[0081] Add activated diatomite and modified liquid into the reactor in a ratio of 1 g: 4 mL and stir, raise the temperature of the reactor to 94°C, keep the reaction at 70°C, lower the temperature of the reactor to room temperature, filter, wash the filter cake with purified water 7 times and then drain, transfer the filter cake to a drying oven at 80°C, and dry to constant weight to obtain a modified diatomite precursor;

[0082] The modified diatomite precursor was placed in a tubular furnace at a temperature of 550° C., calcined for 7 hours, and naturally cooled to room temperature to obtain modified diatomite.

[0083] S4. Preparation of mixed slurry

[0084] Mix polyvinyl alcohol and sodium lauryl sulfate in a weight ratio of 3:1 to obtain a foam stabilizer for later use;

[0085] Weigh: 60 g of loaded modified carbon powder, 25 g of modified diatomaceous earth, 35 g of red mud, 1 g of foam stabilizer, 65 g of sodium silicate and 325 mL of purified water and add them into a reactor, set the stirring speed to 350 r / min, stir at room temperature for 40 min, increase the stirring speed to 650 r / min, add 50 mL of 18 wt% hydrogen peroxide to the reactor, stir for 45 s, and obtain a mixed slurry.

[0086] S5. Preparation of adsorbent microspheres

[0087] The mixed slurry was injected into a mold, maintained at a constant temperature of 58°C for 35 hours, and demolded to obtain adsorbent microspheres with a size of 5-8 mm.

[0088] Example 3

[0089] This embodiment provides a method for preparing adsorbent microspheres for waste gas treatment in a sodium hypophosphite production process, comprising the following steps:

[0090] S1. Preparation of activated carbon powder

[0091] The walnut shells were washed with water and dried, and then crushed using a grinder to obtain walnut shell powder with a particle size of 0.3-0.5 cm;

[0092] The walnut shell powder was placed in a quartz tube protected by nitrogen, the temperature of the quartz tube was raised to 850°C, carbonized and roasted for 100 minutes, and then naturally cooled to room temperature to obtain walnut shell carbonized powder;

[0093] The carbonized walnut shell powder and urea were added into a ball mill in a weight ratio of 3:2 and ball-milled for 50 minutes to obtain a mixture;

[0094] The mixture was placed in a muffle furnace, the temperature of the muffle furnace was increased to 350°C, and the mixture was kept warm for 4 hours. After the calcination was completed, the temperature of the muffle furnace was lowered to room temperature. The solid was washed three times with anhydrous ethanol and then dried. The filter cake was transferred to a drying oven at 80°C and dried to constant weight to obtain activated carbon powder.

[0095] S2. Preparation of loaded modified carbon powder

[0096] Copper nitrate, iron nitrate, zinc nitrate, lanthanum nitrate and deionized water were mixed uniformly in a dosage ratio of 2g:1.4g:2.6g:2.4g:100mL to obtain a modified solution for later use;

[0097] The modified liquid and activated carbon powder were added into the reactor at a ratio of 5 mL:2 g, and ultrasonically dispersed for 60 min at room temperature. The temperature of the reactor was raised to 80° C., and the solvent was evaporated under reduced pressure to obtain a loaded modified carbon powder precursor.

[0098] The loaded modified carbon powder precursor was placed in a nitrogen-protected tubular furnace, the temperature of the tubular furnace was increased to 520° C. at a heating rate of 2° C. / min, and the precursor was kept warm and calcined for 3 hours, then cooled and discharged to obtain the loaded modified carbon powder.

[0099] S3. Preparation of modified diatomite

[0100] 6 mol / L nitric acid solution and 12 wt % hydrogen peroxide were mixed uniformly in a volume ratio of 5:1 to obtain an activation solution for later use;

[0101] Add diatomite and activation solution in a ratio of 1 g:7 mL into a reactor and stir, raise the temperature of the reactor to 80°C, keep the reaction for 90 minutes, lower the temperature of the reactor to room temperature, filter, wash the filter cake with purified water until it is neutral, and then drain, transfer the filter cake to a drying oven at 80°C, and dry to constant weight to obtain activated diatomite;

[0102] Ethyl orthosilicate and 20 wt % tetrapropylammonium hydroxide aqueous solution are mixed uniformly in a weight ratio of 2:3.5 to obtain a modified solution for later use;

[0103] Activated diatomite and modified liquid were added into the reactor in a ratio of 1 g: 4 mL and stirred. The temperature of the reactor was raised to 98°C and kept at 75°C for reaction. The temperature of the reactor was lowered to room temperature and filtered. The filter cake was washed with purified water for 8 times and then dried. The filter cake was transferred to a drying oven at 85°C and dried to constant weight to obtain a modified diatomite precursor.

[0104] The modified diatomite precursor was placed in a tubular furnace at a temperature of 600° C., calcined for 8 hours, and naturally cooled to room temperature to obtain modified diatomite.

[0105] S4. Preparation of mixed slurry

[0106] Mix polyvinyl alcohol and sodium lauryl sulfate in a weight ratio of 3:1 to obtain a foam stabilizer for later use;

[0107] Weigh: 70 g of loaded modified carbon powder, 30 g of modified diatomaceous earth, 40 g of red mud, 1 g of foam stabilizer, 70 g of sodium silicate and 350 mL of purified water and add them into a reactor, set the stirring speed to 400 r / min, stir at room temperature for 50 min, increase the stirring speed to 700 r / min, add 60 mL of 20 wt% hydrogen peroxide to the reactor, stir for 60 s, and obtain a mixed slurry.

[0108] S5. Preparation of adsorbent microspheres

[0109] The mixed slurry was injected into a mold, maintained at a constant temperature of 60°C for 40 hours, and demolded to obtain adsorbent microspheres with a size of 5-8 mm.

[0110] Example 4

[0111] This embodiment provides a method for treating waste gas in a sodium hypophosphite production process, comprising the following steps:

[0112] Step 1: Fill the adsorbent microspheres prepared in Example 1 into the purification box 100 layer by layer to form a plurality of adsorbent beds stacked one on top of the other in the purification box 100. The thickness of each adsorbent bed is 10 cm, and the distance between two adjacent adsorbent beds is 8 cm.

[0113] Step 2: An air inlet pipe 200 is provided at the top of the purification box 100, and an air outlet pipe 300 is provided at the bottom of the purification box 100. A high-precision phosphine sensor of model PH3 / C-1000 is installed on the air outlet pipe 300.

[0114] Step 3: During operation, the temperature of the purification box 100 rises to 80° C. The exhaust gas enters the purification box 100 from the top thereof, is adsorbed downward by multiple adsorbent beds, and is discharged from the exhaust pipe 300 at the bottom of the purification box 100 .

[0115] Step 4: The high-precision phosphine sensor installed on the outlet pipe 300 monitors the phosphine content of the gas in the outlet pipe 300 in real time. When the high-precision phosphine sensor detects that the phosphine content in the gas discharged from the outlet pipe 301 is higher than 1 ppm, the PLC controller sends an alarm signal according to the feedback signal of the high-precision phosphine sensor.

[0116] Step 5. Open the purification box 100, take out the adsorbent microspheres that adsorb phosphine to obtain waste adsorbent microspheres, add the waste adsorbent microspheres and purified water into the reactor at a ratio of 1 g: 7 mL, raise the temperature of the reactor to 60°C, stir for 40 minutes, filter, wash the filter cake 3 times and then drain, wash the filter cake 3 times with purified water at a temperature of 60°C, and then blow dry with nitrogen to obtain regenerated adsorbent microspheres, refill the regenerated adsorbent microspheres into the purification box 100, repeat steps 3 and 4 to treat the exhaust gas.

[0117] Example 5

[0118] This embodiment provides a method for treating waste gas in a sodium hypophosphite production process, comprising the following steps:

[0119] Step 1: Fill the adsorbent microspheres prepared in Example 2 into the purification box 100 layer by layer to form a plurality of adsorbent beds stacked one on top of the other in the purification box 100. The thickness of each adsorbent bed is 11 cm, and the distance between two adjacent adsorbent beds is 9 cm.

[0120] Step 2: An air inlet pipe 200 is provided at the top of the purification box 100, and an air outlet pipe 300 is provided at the bottom of the purification box 100. A high-precision phosphine sensor of model PH3 / C-1000 is installed on the air outlet pipe 300.

[0121] Step 3: During operation, the temperature of the purification box 100 rises to 85° C. The exhaust gas enters the purification box 100 from the top thereof, is adsorbed downward by multiple adsorbent beds, and is discharged from the exhaust pipe 300 at the bottom of the purification box 100 .

[0122] Step 4: The high-precision phosphine sensor installed on the outlet pipe 300 monitors the phosphine content of the gas in the outlet pipe 300 in real time. When the high-precision phosphine sensor detects that the phosphine content in the gas discharged from the outlet pipe 301 is higher than 1 ppm, the PLC controller sends an alarm signal according to the feedback signal of the high-precision phosphine sensor.

[0123] Step 5. Open the purification box 100, take out the adsorbent microspheres that adsorb phosphine to obtain waste adsorbent microspheres, add the waste adsorbent microspheres and purified water into the reactor at a ratio of 1 g: 7 mL, raise the temperature of the reactor to 65°C, stir for 50 minutes, filter, wash the filter cake 3 times and then drain, wash the filter cake 3 times with purified water at a temperature of 65°C, and then blow dry with nitrogen to obtain regenerated adsorbent microspheres, refill the regenerated adsorbent microspheres into the purification box 100, repeat steps 3 and 4 to treat the exhaust gas.

[0124] Example 6

[0125] This embodiment provides a method for treating waste gas in a sodium hypophosphite production process, comprising the following steps:

[0126] Step 1: Fill the adsorbent microspheres prepared in Example 3 into the purification box 100 layer by layer to form a plurality of adsorbent beds stacked one on top of the other in the purification box 100. The thickness of each adsorbent bed is 12 cm, and the distance between two adjacent adsorbent beds is 10 cm.

[0127] Step 2: An air inlet pipe 200 is provided at the top of the purification box 100, and an air outlet pipe 300 is provided at the bottom of the purification box 100. A high-precision phosphine sensor of model PH3 / C-1000 is installed on the air outlet pipe 300.

[0128] Step 3: During operation, the temperature of the purification box 100 rises to 90° C., and the exhaust gas enters the purification box 100 from the top thereof, is adsorbed downward by multiple adsorbent beds, and is discharged from the exhaust pipe 300 at the bottom of the purification box 100 .

[0129] Step 4: The high-precision phosphine sensor installed on the outlet pipe 300 monitors the phosphine content of the gas in the outlet pipe 300 in real time. When the high-precision phosphine sensor detects that the phosphine content in the gas discharged from the outlet pipe 301 is higher than 1 ppm, the PLC controller sends an alarm signal according to the feedback signal of the high-precision phosphine sensor.

[0130] Step 5. Open the purification box 100, take out the adsorbent microspheres that adsorb phosphine to obtain waste adsorbent microspheres, add the waste adsorbent microspheres and purified water into the reactor at a ratio of 1 g: 7 mL, raise the temperature of the reactor to 70°C, stir for 60 minutes, filter, wash the filter cake 3 times and then drain, wash the filter cake 3 times with purified water at a temperature of 70°C, and then blow dry with nitrogen to obtain regenerated adsorbent microspheres, refill the regenerated adsorbent microspheres into the purification box 100, repeat steps 3 and 4 to treat the exhaust gas.

[0131] Comparative Example 1

[0132] The difference between this comparative example and Example 6 is that, when preparing the adsorbent microspheres, the activated carbon powder in step S2 is replaced by the carbonized walnut shell powder in step S1.

[0133] Comparative Example 2

[0134] The difference between this comparative example and Example 6 is that, when preparing the adsorbent microspheres used, step S2 is omitted, and the loaded modified carbon powder in step S4 is replaced by the activated carbon powder in step S1.

[0135] Comparative Example 3

[0136] The difference between this comparative example and Example 6 is that, when preparing the adsorbent microspheres used, step S3 is omitted, and the modified diatomaceous earth in step S4 is replaced by the diatomaceous earth in step S3.

[0137] Comparative Example 4

[0138] The difference between this comparative example and Example 6 is that the temperature of the purification box in step 3 is room temperature.

[0139] Performance Testing:

[0140] The specific surface areas of the adsorbent microspheres used in Examples 4-6 and Comparative Examples 1-4 were determined with reference to the standard GB / T 21650.3-2011 “Mercury intrusion and gas adsorption method for pore size distribution and porosity of solid materials Part 3: Micropore analysis by gas adsorption method”;

[0141] The adsorption saturation of the adsorbent bed is 1ppm when the phosphine content in the exhaust gas is 1ppm. Determine the first time, 5 times of recycling and 20 times of recycling in Examples 4-6 and Comparative Examples 1-4

[0142] The adsorption capacity of the adsorbent microspheres used, where C0 is the concentration of phosphine in the exhaust gas entering the intake pipe (mg / L), C1 is the concentration of phosphine in the exhaust gas discharged from the exhaust pipe (mg / L), V is the volume of exhaust gas entering the purification box (L), and madsorbent is the mass of the adsorbent microspheres made in the purification box (g);

[0143] The specific test results are shown in Table 1 below.

[0144] Table 1. Performance test data of samples

[0145]

[0146] Data Analysis:

[0147] Comparing and analyzing the data in Table 1 above, the present invention optimizes the preparation method of the adsorbent and the adsorption process of the adsorbent microspheres for waste gas, so that the specific surface area of ​​the adsorbent microspheres reaches 489.2m 2 / g, the initial adsorption capacity of the adsorbent microspheres for phosphine in the exhaust gas reaches 187.3 mg / g, the adsorption capacity reaches 179.6 mg / g after 5 cycles of regeneration, and the cycle retention rate reaches 95.89%. After 20 cycles of regeneration, the adsorption capacity reaches 172.9 mg / g, and the cycle retention rate reaches 92.31%. All performance test data are better than those of the comparative example, indicating that the present invention optimizes the dosage ratio of each component by mixing composite materials such as loaded modified carbon powder, modified diatomaceous earth and red mud, which not only effectively improves the specific surface area of ​​the adsorbent microspheres, but also makes the adsorbent microspheres have excellent adsorption capacity and cycle regeneration performance for phosphine in the exhaust gas.

[0148] The above contents are merely examples and explanations of the structure of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

[0149] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0150] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. Waste gas treatment method in the production process of sodium hypophosphite, It is characterized in that The following steps are involved: S1. Add the loaded modified carbon powder, modified diatomaceous earth, red mud, foam stabilizer, sodium silicate and purified water into a reactor, stir for 30-50 min at room temperature, add a foaming agent into the reactor, stir for 30-60 s, and obtain a mixed slurry; S2, injecting the mixed slurry into a mold, maintaining it at a constant temperature of 55-60°C for 30-40 hours, demolding it, and obtaining adsorbent microspheres with a size of 5-8 mm; S3, filling the adsorbent microspheres layer by layer into the purification box (100), forming a plurality of adsorbent beds stacked one on top of another in the purification box (100), raising the temperature of the purification box (100) to 80-90° C., and allowing the waste gas to enter the purification box (100) from the top, and then be adsorbed by the plurality of adsorbent beds downwards, and then be discharged from the outlet pipe (300) at the bottom of the purification box (100); S4. When the phosphine content of the gas in the outlet branch pipe (301) is higher than 1 ppm, the adsorbent bed is replaced and the adsorbent microspheres are recycled to obtain regenerated adsorbent microspheres, and the regenerated adsorbent microspheres are refilled into the purification box (100), and step S3 is repeated to treat the exhaust gas.

2. The method for treating waste gas in the sodium hypophosphite production process according to claim 1, It is characterized in that In step S1, the amount ratio of the loaded modified carbon powder, modified diatomaceous earth, red mud, foam stabilizer, purified water, sodium silicate and foaming agent is 5-7g:2-3g:3-4g:0.1g:6-7g:30-35mL:4-6mL, the foam stabilizer is composed of polyvinyl alcohol and sodium dodecyl sulfate in a weight ratio of 3:1, and the foaming agent is 15-20wt% hydrogen peroxide.

3. The method for treating waste gas in the sodium hypophosphite production process according to claim 1, It is characterized in that The cyclic regeneration method in step S4 is: adding the waste adsorbent microspheres and purified water in a dosage ratio of 1g:7mL into the reactor, raising the temperature of the reactor to 60-70°C, stirring for 40-60min, filtering, washing the filter cake with purified water at a temperature of 60-70°C for 3 times, and then drying with nitrogen to obtain regenerated adsorbent microspheres.

4. The method for treating waste gas in the sodium hypophosphite production process according to claim 1, It is characterized in that The loaded modified carbon powder is processed by the following steps: A1. Add the modified liquid and activated carbon powder into a reactor, perform ultrasonic dispersion for 40-60 min at room temperature, and perform post-treatment to obtain a loaded modified carbon powder precursor; A2. Place the loaded modified carbon powder precursor in a nitrogen-protected tubular furnace, increase the temperature of the tubular furnace to 480-520°C at a heating rate of 2°C / min, keep the temperature and calcine for 2-3h, cool down and discharge the material to obtain the loaded modified carbon powder.

5. The method for treating waste gas in the sodium hypophosphite production process according to claim 4, It is characterized in that In step A1, the modified liquid is composed of copper nitrate, iron nitrate, zinc nitrate, lanthanum nitrate and deionized water in a dosage ratio of 1.5-2g:1-1.4g:2-2.6g:1.8-2.4g:100mL, and the dosage ratio of the modified liquid to the activated carbon powder is 5mL:2g. The post-treatment includes: after the reaction is completed, the temperature of the reactor is increased to 70-80°C, and the solvent is evaporated under reduced pressure to obtain a loaded modified carbon powder precursor.

6. The method for treating waste gas in the sodium hypophosphite production process according to claim 4, It is characterized in that Activated carbon powder is processed by the following steps: B1, washing the walnut shells with water and drying them, and crushing them using a grinder to obtain walnut shell powder with a particle size of 0.3-0.5 cm; B2. Place the walnut shell powder in a nitrogen-protected quartz tube, carbonize and roast for 80-100 minutes, and cool naturally to room temperature to obtain walnut shell carbonized powder; B3. Add walnut shell carbonized powder and urea into a ball mill, and ball mill for 30-50 minutes to obtain a mixture. Place the mixture into a muffle furnace, increase the temperature of the muffle furnace to 300-350° C., and heat-preserve and roast for 3-4 hours. Post-process to obtain activated carbon powder.

7. The method for treating waste gas in the production process of sodium hypophosphite according to claim 6, It is characterized in that In step B2, the carbonization calcination temperature is 750-850°C; In step B3, the weight ratio of the walnut shell carbonized powder to urea is 3:1-2, and the post-treatment includes: after the roasting is completed, the temperature of the muffle furnace is reduced to room temperature, the solid matter is washed with anhydrous ethanol for 3 times and then dried, and the filter cake is transferred to a drying oven at a temperature of 70-80°C and dried to constant weight to obtain activated carbon powder.

8. The method for treating waste gas in the sodium hypophosphite production process according to claim 1, It is characterized in that Modified diatomaceous earth is processed by the following steps: C1. Add diatomaceous earth and activation solution into a reaction kettle and stir. Raise the temperature of the reaction kettle to 70-80°C, keep the temperature for 70-90 minutes, and perform post-treatment to obtain activated diatomaceous earth. C2, adding activated diatomite and modified liquid into a reactor and stirring, raising the temperature of the reactor to 90-98°C, keeping the temperature at 65-75°C, and post-treating to obtain a modified diatomite precursor; C3. Place the modified diatomite precursor in a tube furnace at a temperature of 500-600° C., calcine for 6-8 hours, and cool naturally to room temperature to obtain modified diatomite.

9. The method for treating waste gas in the sodium hypophosphite production process according to claim 8, It is characterized in that In step C1, the amount ratio of the diatomite and the activation solution is 1g:7mL, the activation solution is composed of 4-6mol / L nitric acid solution and 10-12wt% hydrogen peroxide in a volume ratio of 5:1, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is reduced to room temperature, suction filtration, the filter cake is washed with purified water until neutral and then dried, the filter cake is transferred to a drying oven at a temperature of 70-80°C, and dried to constant weight to obtain activated diatomite; in step C2, the amount ratio of the activated diatomite and the modifying solution is 1g:4mL, the modifying solution is composed of tetraethyl orthosilicate and 20wt% tetrapropylammonium hydroxide aqueous solution in a weight ratio of 2:3.5, and the post-treatment includes: after the reaction is completed, the temperature of the reactor is reduced to room temperature, suction filtration, the filter cake is washed with purified water 6-8 times and then dried, the filter cake is transferred to a drying oven at a temperature of 75-85°C, and dried to constant weight to obtain a modified diatomite precursor.

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