Gas-phase white carbon black tail gas dechlorination process

Abstract

The invention discloses a gas-phase white carbon black tail gas dechlorination process, which belongs to the technical field of tail gas treatment, and comprises tail gas pretreatment and particulate matter separation, germanium molecular sieve carrier preparation and modification, Fe-Cu bimetallic nano-cluster loading, dynamic pulsed electric field activation, dry-process dechlorination, wet-process reduction synergistic dechlorination and photo-thermal coupling regeneration. According to the method, the alkyl halide dehalogenase is introduced as a stabilizer, and the Fe3O4-CuO nano-cluster activated by the dynamic pulsed electric field is adopted, so that the reaction process is remarkably optimized, the alkyl halide dehalogenase and active components in the sodium thiosulfate solution form synergistic action sites, the selectivity and efficiency of sodium thiosulfate participating in the reaction are improved, and the reaction time is shortened. The consumption in a non-target reaction is avoided; according to the Fe3O4-CuO nano-cluster activated by the dynamic pulsed electric field, the chlorine removal efficiency is improved, and the usage amount of sodium thiosulfate is reduced, so that the consumption amount of sodium thiosulfate and the generation amount of waste liquid are synchronously reduced, and the high-cost investment of enterprises on waste liquid treatment and the risk of environmental protection compliance are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tail gas treatment, in particular to a gas phase white carbon black tail gas dechlorination process. BACKGROUND

[0002] In the production process of gas phase white carbon black, tail gas dechlorination usually adopts alkali absorption process, such as sodium hydroxide solution spraying method, but this process has significant defects in practical application.

[0003] When treating chlorine-containing tail gas, a large amount of salt-containing waste lye is generated by the reaction of lye with hydrogen chloride, chlorine and other components, which contains mixed salts such as sodium hypochlorite and sodium chloride. Such waste liquid is difficult to be directly resourceized due to its complex composition and low purity, and needs to be additionally invested in high cost for neutralization, separation or deep treatment, resulting in heavier burden on enterprise operation.

[0004] In addition, if the high concentration of salt in the waste liquid is not properly disposed and directly discharged, it is easy to cause water pollution, especially the strong corrosion and environmental toxicity of chlor-alkali wastewater, which puts strict requirements on the discharge standard, and the enterprise faces the risk of environmental compliance and potential ecological responsibility pressure. SUMMARY

[0005] In view of the above-mentioned shortcomings of the prior art, the present application provides a gas phase white carbon black tail gas dechlorination process.

[0006] To achieve the above purpose, the present application is realized by the following technical scheme:

[0007] A gas phase white carbon black tail gas dechlorination process, 1. A gas phase white carbon black tail gas dechlorination process, characterized in that it comprises the following steps:

[0008] S1: tail gas pretreatment and particulate matter separation;

[0009] The gas phase white carbon black tail gas is separated by three-stage cyclone separation to remove silica particles:

[0010] Filtered by a bag filter;

[0011] S2: preparation and modification of germanium molecular sieve carrier;

[0012] γ-Al2O3 carrier pretreatment: γ-Al2O3 is calcined to remove surface hydroxyl groups, then immersed in nitric acid solution after cooling, stirred, washed, and dried to obtain pretreated γ-Al2O3;

[0013] Germanium doping modification;

[0014] Dissolve sodium germanate in deionized water to obtain an impregnation solution;

[0015] Hydrothermal synthesis, mixing pretreated γ-Al2O3 with impregnation solution, hydrothermal reaction, forming Ge-Al2O3 molecular sieve framework;

[0016] Surface acid site regulation, ion exchange of Ge-Al2O3 molecular sieve framework in NH4NO3 solution, calcination to obtain Ge-AN-Al2O3 carrier;

[0017] S3: Fe-Cu bimetallic nanocluster loading;

[0018] Stepwise impregnation method:

[0019] Fe precursor loading, preparation of Fe(NO3)3 solution, impregnation of Ge-AN-Al2O3 carrier, ultrasonic dispersion and drying;

[0020] Cu precursor loading, preparation of Cu(NO3)2 solution, secondary impregnation of Ge-AN-Al2O3 carrier and drying;

[0021] Reduction-oxidation activation, after reduction of Ge-AN-Al2O3 carrier loaded with Fe-Cu precursor in H2 / N2 mixed atmosphere, switch to air atmosphere to form Fe3O4-CuO nanoclusters;

[0022] S4: Dynamic pulse electric field activation of Fe3O4-CuO nanoclusters;

[0023] S5: Dry dechlorination;

[0024] In the fixed bed reactor, fill the dry dechlorination agent, under the assistance of pulse electric field, promote the dry adsorption of gas phase white carbon black tail gas;

[0025] S6: Wet reduction and dechlorination;

[0026] Prepare sodium thiosulfate solution, add halogenated alkyl dehalogenase, adjust pH to obtain dechlorination liquid;

[0027] The gas phase white carbon black tail gas after dry adsorption is subjected to wet reduction by dechlorination liquid to obtain dechlorination tail gas;

[0028] Byproduct recovery, the dechlorination liquid is concentrated and crystallized by a multi-effect evaporator, and industrial-grade NaCl and Na2SO4 are obtained by centrifugal separation;

[0029] S7: Photothermal coupling regeneration;

[0030] Regeneration process: thermal regeneration, heating of saturated dry dechlorination agent, constant temperature decomposition of adsorbed Cl2 / HCl;

[0031] Photocatalytic assistance, synchronous application of ultraviolet light, excitation of ·OH free radicals on the surface of Fe-Cu nanoclusters, deep decomposition of organic chlorine pollutants to release Cl2;

[0032] The regenerated tail gas is treated, and the released Cl2 is introduced into the dechlorination solution for wet reduction to form a closed loop.

[0033] Further, S1 is specifically: tail gas pretreatment and particulate matter separation;

[0034] The gas-phase white carbon black tail gas is sequentially passed through three-stage cyclone separation to remove silica particles:

[0035] The first-stage cyclone has a temperature of 180-200°C, an inlet flow rate of 15-20 m / s, and removes >50 μm particles;

[0036] The second-stage cyclone has a temperature of 150-170°C, an inlet flow rate of 25-30 m / s, and removes 10-50 μm particles;

[0037] The third-stage cyclone has a temperature of 120-140°C, an inlet flow rate of 35-40 m / s, and removes 1-10 μm particles.

[0038] Further, S2 is specifically: γ-Al2O3 with a particle size of 50-100 μm is calcined at 500-600°C for 2-4 h to remove surface hydroxyl groups, and after cooling, is immersed in a nitric acid solution, stirred at 60-72°C for 30-50 min, washed to neutral, and dried at 90-110°C for standby, to obtain pretreated γ-Al2O3;

[0039] Sodium germanate is dissolved in deionized water to a concentration of 4-6 wt%, and the pH is adjusted by ammonia water to obtain an impregnation solution;

[0040] The pretreated γ-Al2O3 is mixed with the impregnation solution at a solid-liquid ratio of 1-1.5:5-7, and is subjected to hydrothermal reaction at 160-180°C for 4-6 h to form a Ge-Al2O3 molecular sieve framework;

[0041] The Ge-Al2O3 molecular sieve framework is immersed in a 0.1-0.2 mol / L NH4NO3 solution, and is subjected to ion exchange at 70-80°C for 1-2 h, and is calcined at 550-620°C for 2-3 h to form H-type acid sites, to obtain a Ge-AN-Al2O3 carrier.

[0042] Further, S3 is specifically: a 10-15 wt% Fe(NO3)3 solution is prepared, the Ge-AN-Al2O3 carrier is impregnated, and is ultrasonically dispersed for 20-30 min, and is dried at 100-120°C;

[0043] A 5-8 wt% Cu(NO3)2 solution is prepared, the Ge-AN-Al2O3 carrier is twice impregnated, and is dried at 100-120°C;

[0044] The Fe-Cu precursor loaded Ge-AN-Al2O3 carrier is placed in a tube furnace, reduced under H2 / N2 mixed atmosphere for 30-60 min at 300-400 DEG C, switched to air atmosphere, and oxidized for 1-2 h at 500-600 DEG C to form Fe3O4-CuO nanoclusters.

[0045] Further, S4 is specifically as follows: the Fe3O4-CuO nanoclusters are placed in a fixed bed reactor, a titanium alloy mesh electrode is embedded in the reactor, the distance between the electrode and the bed layer of the dechlorination agent is less than or equal to 2 mm, and the filling density of the bed layer is greater than or equal to 800 kg / m 3 ;

[0046] A continuous pulse electric field is applied to the reactor, the voltage is 2-3 V, the frequency is 100-500 Hz, and the temperature is 80-150 DEG C.

[0047] Further, S5 is specifically as follows: three-stage series adsorption beds are arranged in the fixed bed reactor, and dry dechlorination agents are filled, the density is 600-800 kg / m 3 ;

[0048] Under the conditions of a temperature of 120-180 DEG C, an airspeed of 1000-1500 h -1 , a pressure of -0.5 to -1 kPa, and a pulse electric field, the ionization dry adsorption of Cl2 in the gas phase carbon black tail gas is promoted.

[0049] Further, S6 is specifically as follows: a sodium thiosulfate solution with a concentration of 5-8 wt% is prepared, 0.4-0.6% of halogenated alkyl dehalogenase is added, and the pH is adjusted to 8-10 by NaOH to obtain a dechlorination liquid;

[0050] The gas phase carbon black tail gas after dry adsorption is subjected to wet reduction by the dechlorination liquid to obtain dechlorination tail gas;

[0051] The dechlorination liquid is concentrated and crystallized by a multi-effect evaporator, and industrial-grade NaCl and Na2SO4 are obtained by centrifugal separation.

[0052] Further, S7 is specifically as follows: the saturated dry dechlorination agent is first heated to 200 DEG C and then heated to 400 DEG C under N2 protection, and the adsorbed Cl2 / HCl is decomposed for 1.5-2 h at constant temperature;

[0053] Simultaneously, ultraviolet light is applied to excite ·OH free radicals on the surface of the Fe-Cu nanoclusters, deeply decompose organic chlorine pollutants to release Cl2, regenerate the released Cl2, and introduce the regenerated Cl2 into the dechlorination liquid for wet reduction to form a closed loop.

[0054] Compared with the prior art, the present application has the following beneficial effects:

[0055] 1. The present application introduces halogenated alkane dehalogenase as a stabilizer and uses Fe3O4-CuO nanoclusters activated by dynamic pulsed electric field, which significantly optimizes the reaction process. On the one hand, halogenated alkane dehalogenase forms a synergistic site with the active components in the sodium thiosulfate solution, improving the selectivity and efficiency of sodium thiosulfate in the reaction, and avoiding its consumption in non-target reactions. On the other hand, the Fe3O4-CuO nanoclusters activated by dynamic pulsed electric field enhance the removal efficiency of chlorine, reducing the amount of sodium thiosulfate used, thereby simultaneously reducing the consumption of sodium thiosulfate and the amount of waste liquid, reducing the high cost investment and environmental compliance risk of enterprises in waste liquid treatment.

[0056] 2. The present application uses dynamic pulsed electric field to activate Fe3O4-CuO nanoclusters, which can instantaneously polarize the electron distribution on the surface of the nanoclusters, activate the active crystal surface and active sites, and enhance the immobilization efficiency of the nanoclusters on Fe 3+ and other heavy metal ions. During the formation of by-products, the activated nanoclusters can effectively enrich and immobilize Fe elements on their surfaces, reducing the residual concentration of Fe elements in the by-products NaCl and Na2SO4, substantially improving the purification level of the by-products, making them more easily resourceful, avoiding the problem of additional high-cost treatment due to complex composition and low purity of waste liquid, and being conducive to the improvement of economic benefits of enterprises.

[0057] 3. The present application discloses that there is a significant synergistic effect between halogenated alkane dehalogenase and Fe3O4-CuO nanoclusters activated by dynamic pulsed electric field. The catalytic reaction of halogenated alkane dehalogenase optimizes the chemical microenvironment of the reaction system, making the active sites of Fe3O4-CuO nanoclusters more easily exposed to participate in the reaction. At the same time, the activated nanoclusters can immobilize halogenated alkane dehalogenase molecules to form enzyme-nanocluster complexes, which have both the efficient catalytic effect of enzymes and the adsorption enrichment effect of nanoclusters, significantly improving the synergistic catalytic efficiency of the entire reaction system, reducing the consumption of sodium thiosulfate, reducing the amount of waste liquid, and improving the purity of by-products, etc. It shows a synergistic effect beyond the sum of the individual effects, providing a more efficient, environmentally friendly and economic solution for tail gas dechlorination in the production process of fumed silica.

[0058] 4. The present application realizes the regeneration of the active sites of the dechlorination agent and avoids the collapse or sintering of the nanocluster structure through precise thermal regeneration temperature control and photocatalytic assistance. The closed-loop circulation system converts the chlorine resources originally discharged as waste into valuable chemicals, forming a closed loop of resource recycling, significantly improving the environmental friendliness and economic feasibility of the process. BRIEF DESCRIPTION OF DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only show some of the embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without any creative effort.

[0060] Figure 1 Process flow diagram of the present application. DETAILED DESCRIPTION

[0061] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without any creative effort are within the protection scope of the present application.

[0062] Embodiment 1: The present embodiment provides a gas phase white carbon black tail gas dechlorination process, comprising the following steps:

[0063] S1: Tail gas pretreatment and particulate separation;

[0064] Purpose: To remove the residual nanoscale silicon dioxide particles (particle size ≤100 nm) in the gas phase white carbon black tail gas, to avoid blocking the pores of the subsequent dechlorination agent.

[0065] The gas phase white carbon black tail gas is separated by three-stage cyclone separation to remove silicon dioxide particles:

[0066] First-stage cyclone (temperature 200℃), inlet flow rate 20m / s, remove >50μm particles;

[0067] Second-stage cyclone (temperature 170℃), inlet flow rate 30m / s, remove 10-50μm particles;

[0068] Third-stage cyclone (temperature 140℃), inlet flow rate 40m / s, remove 1-10μm particles;

[0069] Bag filter;

[0070] S2: Preparation and modification of germanium molecular sieve carrier;

[0071] Objective: To synthesize a Ge-AN-Al2O3 molecular sieve carrier with a multi-stage pore structure, specific surface area ≥600m 2 / g, pore size 2nm.

[0072] γ-Al2O3 support pretreatment: γ-Al2O3 (particle size 100 μm) was placed in a muffle furnace and calcined at 600 ℃ for 4 h to remove surface hydroxyl groups. After cooling, it was immersed in a 5% nitric acid solution and stirred at 72 ℃ for 50 min. After washing to neutral, it was dried at 110 ℃ and used as needed, obtaining pretreated γ-Al2O3;

[0073] Germanium doping modification;

[0074] Impregnation solution preparation: sodium germanate (Na2GeO3) was dissolved in deionized water at a concentration of 6 wt%, and the pH was adjusted to 11 with ammonia water, obtaining an impregnation solution;

[0075] Hydrothermal synthesis: pretreated γ-Al2O3 was mixed with the impregnation solution at a solid-liquid ratio of 1.5:7, transferred to a high-pressure reaction kettle, and hydrothermally reacted at 180 ℃ for 6 h to form a Ge-Al2O3 molecular sieve framework;

[0076] Surface acid site regulation: the Ge-Al2O3 molecular sieve framework was immersed in a 0.2 mol / L NH4NO3 solution (liquid-solid ratio 10:1) at 80 ℃ for ion exchange for 2 h, repeated 3 times, and calcined at 620 ℃ for 3 h to form H-type acid sites, obtaining a Ge-AN-Al2O3 support;

[0077] S3: Fe-Cu bimetallic nanocluster loading;

[0078] Objective: to uniformly load Fe3O4-CuO nanoclusters (particle size ≤5 nm) in the molecular sieve channel.

[0079] Stepwise impregnation method:

[0080] Fe precursor loading: a 15 wt% Fe(NO3)3 solution (ethanol as solvent) was prepared, and the Ge-AN-Al2O3 support was impregnated at a liquid-solid ratio of 3:1, ultrasonic dispersed for 30 min, and dried at 120 ℃;

[0081] Cu precursor loading: an 8 wt% Cu(NO3)2 solution (methanol as solvent) was prepared, and the Ge-AN-Al2O3 support was twice impregnated at a liquid-solid ratio of 2:1, and dried at 120 ℃;

[0082] Reduction-oxidation activation: the Ge-AN-Al2O3 support loaded with Fe-Cu precursors was placed in a tube furnace, and H2 / N2 mixed gas (H2 accounted for 10%) was used as the atmosphere, and reduced at 400 ℃ for 60 min. The atmosphere was switched to air, and oxidized at 600 ℃ for 2 h to form Fe3O4-CuO nanoclusters;

[0083] S4: dynamic pulse electric field activation of Fe3O4-CuO nanoclusters;

[0084] Objective: Enhance the surface oxygen vacancies of Fe3O4-CuO nanoclusters by pulse electric field (5 V, 500 Hz) to improve the adsorption efficiency of Cl2.

[0085] Reactor structure: titanium alloy mesh electrode (10 mm interval) embedded in the fixed bed reactor, electrode and dechlorination agent bed interval ≤2 mm, bed filling density ≥800 kg / m 3 .

[0086] Pulse parameters: continuous pulse (activation 5 s / interval 30 s) for electric field application, temperature 150 ℃, dry dechlorination agent obtained;

[0087] S5: dry dechlorination;

[0088] Three-stage series adsorption bed (each bed thickness 0.5 m) in the fixed bed reactor, filled with dry dechlorination agent, density 800 kg / m 3 ;

[0089] At a temperature of 180 ℃, space velocity 1500 h -1 , pressure -0.5 kPa, pulse electric field assisted (3 V / 200 Hz, activation interval 30 s), ionization dry adsorption of Cl2 in gas phase carbon black tail gas is promoted;

[0090] S6: wet reduction and dechlorination;

[0091] Objective: Use sodium thiosulfate (Na2S2O3) to reduce residual Cl2 to generate recyclable NaCl / Na2SO4 mixed salt.

[0092] Prepare a sodium thiosulfate solution with a concentration of 8 wt%, add 0.6% haloalkane dehalogenase (stabilizer), adjust the pH to 10 with NaOH, and obtain a dechlorination liquid;

[0093] Under the conditions of liquid-gas ratio 4 L / m 3 , space velocity 1800 h -1 , wet reduction of gas phase carbon black tail gas after dry adsorption by dechlorination liquid to obtain dechlorination tail gas;

[0094] By-product recovery: dechlorination liquid is concentrated and crystallized by multi-effect evaporator (vacuum degree -0.09 MPa, temperature 85 ℃), and industrial grade NaCl and Na2SO4 are obtained by centrifugal separation;

[0095] S7: photothermal coupling regeneration;

[0096] Regeneration process: thermal regeneration, saturated dry dechlorination agent is first heated to 200 ℃ at a rate of 3 ℃ / min, and then heated to 400 ℃ at a rate of 5 ℃ / min under N2 protection, and the adsorbed Cl2 / HCl is decomposed for 2 h;

[0097] photocatalytic assisted, synchronously applying ultraviolet light (wavelength 254 nm, intensity 50 mW / cm 2 ), exciting Fe-Cu nanocluster surface ·OH free radicals, deeply decomposing organic chlorine pollutants (such as CH3Cl) to obtain Cl2;

[0098] Regeneration tail gas treatment, the released Cl2 is introduced into the wet dechlorination system to form a closed loop.

[0099] Example 2: This example provides a fumed white carbon black tail gas dechlorination process, comprising the following steps:

[0100] S1: tail gas pretreatment and particulate matter separation;

[0101] The fumed white carbon black tail gas is separated by three-stage cyclone separation to remove silica particles:

[0102] First-stage cyclone (temperature 180℃), inlet flow rate 15m / s, remove >50μm particles;

[0103] Second-stage cyclone (temperature 150℃), inlet flow rate 25m / s, remove 10-50μm particles;

[0104] Third-stage cyclone (temperature 120℃), inlet flow rate 35m / s, remove 1-10μm particles;

[0105] Bag dust removal filtration;

[0106] S2: germanium molecular sieve carrier preparation and modification;

[0107] γ-Al2O3 carrier pretreatment: γ-Al2O3 (particle size 50μm) is placed in a muffle furnace, calcined at 500℃ for 2h to remove surface hydroxyl groups, cooled and immersed in a 5% nitric acid solution, stirred at 60℃ for 30min, washed to neutral, dried at 90℃ for standby, to obtain pretreated γ-Al2O3;

[0108] Germanium doping modification;

[0109] Impregnation solution preparation: dissolve sodium germanate (Na2GeO3) in deionized water, concentration 4-6wt%, adjust pH to 9 with ammonia water, to obtain the impregnation solution;

[0110] Hydrothermal synthesis: pretreated γ-Al2O3 is mixed with the impregnation solution at a solid-liquid ratio of 1:5, transferred to a high-pressure reaction kettle, and hydrothermally reacted at 160℃ for 4h to form a Ge-Al2O3 molecular sieve framework;

[0111] Surface acid site regulation: Ge-Al2O3 molecular sieve framework was immersed in 0.1 mol / L NH4NO3 solution (liquid-solid ratio 10:1), ion exchanged at 70°C for 1 h, repeated 3 times, calcined at 550°C for 2 h to form H-type acid sites, and Ge-AN-Al2O3 carrier was obtained;

[0112] S3: Fe-Cu bimetallic nanocluster loading;

[0113] Stepwise impregnation method:

[0114] Fe precursor loading: 10wt% Fe(NO3)3 solution (ethanol as solvent) was prepared, Ge-AN-Al2O3 carrier was immersed according to liquid-solid ratio 3:1, ultrasonic dispersion for 20 min, and dried at 100°C;

[0115] Cu precursor loading: 5wt% Cu(NO3)2 solution (methanol as solvent) was prepared, Ge-AN-Al2O3 carrier was twice immersed according to liquid-solid ratio 2:1, and dried at 100°C;

[0116] Reduction-oxidation activation: Ge-AN-Al2O3 carrier loaded with Fe-Cu precursor was placed in a tube furnace, reduced at 300°C for 30 min under H2 / N2 mixed gas (H2 accounted for 10%), and switched to air atmosphere, and oxidized at 500°C for 1 h to form Fe3O4-CuO nanoclusters;

[0117] S4: Dynamic pulse electric field activation of Fe3O4-CuO nanoclusters;

[0118] Fe3O4-CuO nanoclusters were placed in a fixed bed reactor, titanium alloy mesh electrodes were embedded in the reactor (spacing 10 mm), the electrode and the dechlorination agent bed layer spacing was ≤2 mm, and the bed layer filling density was ≥800 kg / m 3 ;

[0119] The electric field (2V, 100Hz) was applied to the reactor in a continuous pulse mode (activation 5s / interval 30s), and the temperature was 80°C, which enhanced the surface oxygen vacancies of Fe3O4-CuO nanoclusters to obtain dry dechlorination agent;

[0120] S5: Dry dechlorination;

[0121] Three-stage series adsorption beds (each bed thickness 0.5m) were arranged in the fixed bed reactor, and dry dechlorination agent was filled, and the density was 600 kg / m 3 ;

[0122] At a temperature of 120°C, space velocity of 1000h -1 , pressure-1kPa, pulse electric field auxiliary (3V / 200Hz, activation interval 30s), ionization of Cl2 in gas phase white carbon black tail gas was promoted by dry adsorption;

[0123] S6: Wet reduction and dechlorination in coordination;

[0124] Objective: Reduce residual Cl2 with sodium thiosulfate (Na2S2O3) to generate recyclable NaCl / Na2SO4 mixed salt.

[0125] Prepare a 5wt% sodium thiosulfate solution, add 0.4% haloalkane dehalogenase (stabilizer), adjust the pH to 8 with NaOH, and obtain a dechlorination solution;

[0126] Under the conditions of liquid-gas ratio 4L / m 3 , and space velocity 1800h -1 , the dry adsorbed gas phase white carbon black tail gas is subjected to wet reduction by the dechlorination solution to obtain dechlorination tail gas;

[0127] By-product recovery: The dechlorination solution is concentrated and crystallized by a multi-effect evaporator (vacuum degree -0.09MPa, temperature 85℃), and industrial-grade NaCl and Na2SO4 are obtained by centrifugal separation;

[0128] S7: Photothermal coupling regeneration;

[0129] Regeneration process: Thermal regeneration, saturated dry dechlorination agent is first heated to 200℃ at a rate of 3℃ / min, and then heated to 400℃ at a rate of 5℃ / min, and held for 1.5h to decompose and adsorb Cl2 / HCl;

[0130] Photocatalytic assistance, synchronous application of ultraviolet light (wavelength 254nm, intensity 50mW / cm 2 ), to excite ·OH free radicals on the surface of Fe-Cu nanoclusters, and to deeply decompose organic chlorine pollutants (such as CH3Cl) to obtain Cl2;

[0131] Regeneration tail gas treatment: The released Cl2 from the regeneration is introduced into the wet dechlorination system to form a closed loop.

[0132] Example 3: This example provides a gas phase white carbon black tail gas dechlorination process, comprising the following steps:

[0133] S1: Tail gas pretreatment and particulate matter separation;

[0134] Objective: To remove the residual nanoscale silica particles (particle size ≤100nm) in the gas phase white carbon black tail gas to avoid clogging the pores of the subsequent dechlorination agent.

[0135] The gas phase white carbon black tail gas is subjected to three-stage cyclone separation to remove silica particles:

[0136] First-stage cyclone (temperature 185℃), inlet flow rate 16m / s, remove >50μm particles;

[0137] Secondary cyclone (temperature 163℃), inlet flow rate 27 m / s, remove 10-50 μm particles;

[0138] Tertiary cyclone (temperature 131℃), inlet flow rate 39 m / s, remove 1-10 μm particles;

[0139] Bag filter;

[0140] S2: Preparation and modification of germanium molecular sieve carrier

[0141] Objective: Synthesis of Ge-AN-Al2O3 molecular sieve carrier with multi-level pore structure, specific surface area ≥ 600 m 2 / g, pore size 1 nm.

[0142] γ-Al2O3 carrier pretreatment: γ-Al2O3 (particle size 80 μm) was placed in a muffle furnace, calcined at 520℃ for 3h to remove surface hydroxyl groups, and then immersed in a 5% nitric acid solution after cooling, stirred at 70℃ for 40 min, washed to neutral, and dried at 100℃ for standby, to obtain pretreated γ-Al2O3;

[0143] Germanium doping modification;

[0144] Impregnation solution preparation: Dissolve sodium germanate (Na2GeO3) in deionized water with a concentration of 5wt%, adjust the pH to 10 with ammonia water to obtain the impregnation solution;

[0145] Hydrothermal synthesis: Mix pretreated γ-Al2O3 with the impregnation solution at a solid-liquid ratio of 1.2:6, transfer to a high-pressure reaction kettle, and hydrothermally react at 170℃ for 4h to form a Ge-Al2O3 molecular sieve framework;

[0146] Surface acid site regulation: Immersing the Ge-Al2O3 molecular sieve framework in a 0.1 mol / L NH4NO3 solution (liquid-solid ratio 10:1) at 75℃ for 2h, repeating 3 times, and calcining at 580℃ for 3h to form H-type acid sites, to obtain Ge-AN-Al2O3 carrier;

[0147] S3: Fe-Cu bimetallic nanocluster loading;

[0148] Objective: Uniformly load Fe3O4-CuO nanoclusters (particle size ≤ 5 nm) in the molecular sieve channels.

[0149] Stepwise impregnation method:

[0150] Fe precursor loading: Prepare a 12wt% Fe(NO3)3 solution (ethanol as solvent), impregnate the Ge-AN-Al2O3 carrier at a liquid-solid ratio of 3:1, ultrasonic dispersion for 25 min, and dry at 120℃;

[0151] Cu precursor loading: 7wt% Cu(NO3)2 solution (methanol as solvent) was prepared, and Ge-AN-Al2O3 carrier was twice impregnated with the solution at a liquid-solid ratio of 2:1, and then dried at 110°C;

[0152] Reduction-oxidation activation: the Fe-Cu precursor loaded Ge-AN-Al2O3 carrier was placed in a tube furnace, and was reduced at 360°C for 40 min under H2 / N2 mixed gas (H2 accounted for 10%), and then was switched to air atmosphere and oxidized at 550°C for 2 h to form Fe3O4-CuO nanoclusters;

[0153] S4: dynamic pulse electric field activation of Fe3O4-CuO nanoclusters;

[0154] The Fe3O4-CuO nanoclusters were placed in a fixed bed reactor, and a titanium alloy mesh electrode was embedded in the reactor (spacing 10 mm), and the spacing between the electrode and the dechlorination agent bed was ≤2 mm, and the bed packing density was ≥800 kg / m 3 ;

[0155] A continuous pulse (activation 5 s / interval 30 s) electric field (4 V, 200 Hz) was applied to the reactor at a temperature of 100°C to enhance the surface oxygen vacancies of the Fe3O4-CuO nanoclusters, and a dry dechlorination agent was obtained;

[0156] S5: dry dechlorination;

[0157] Three-stage series adsorption beds (each bed thickness 0.5 m) were arranged in the fixed bed reactor, and the dry dechlorination agent was filled, and the density was 700 kg / m 3 ;

[0158] At a temperature of 150°C, an airspeed of 1300 h -1 -0.8 kPa, and pulse electric field assistance (3 V / 200 Hz, activation interval 30 s), the ionization of Cl2 in the gas phase carbon black tail gas was promoted by dry adsorption;

[0159] S6: wet reduction and dechlorination;

[0160] Objective: using sodium thiosulfate (Na2S2O3) to reduce residual Cl2 to generate recyclable NaCl / Na2SO4 mixed salt.

[0161] A 6wt% sodium thiosulfate solution was prepared, 0.5% haloalkane dehalogenase (stabilizer) was added, and the pH was adjusted to 9 by NaOH to obtain a dechlorination solution;

[0162] The gas phase carbon black tail gas after dry adsorption was passed through the dechlorination solution for wet reduction under the conditions of a liquid-gas ratio of 4 L / m 3 , and an airspeed of 1800 h -1 to obtain a dechlorination tail gas;

[0163] The by-product recovery, the dechlorination liquid is concentrated and crystallized by multi-effect evaporator (vacuum degree-0.09 MPa, temperature 85℃), and industrial grade NaCl and Na2SO4 are obtained by centrifugal separation;

[0164] S7: Photothermal coupling regeneration;

[0165] Regeneration process: thermal regeneration, saturated dry dechlorination agent is first heated to 200℃ at a rate of 3℃ / min, and then heated to 400℃ at a rate of 5℃ / min, and the adsorbed Cl2 / HCl is decomposed for 2h;

[0166] Photocatalytic assistance, synchronous application of ultraviolet light (wavelength 254nm, intensity 50mW / cm 2 ), to excite ·OH free radicals on the surface of Fe-Cu nanoclusters, and to deeply decompose organic chlorine pollutants (such as CH3Cl) to obtain Cl2;

[0167] Regeneration tail gas treatment, the Cl2 released in regeneration is introduced into the wet dechlorination system to form a closed loop.

[0168] Comparative Example 1: The difference between this comparative example and Example 3 is that the Fe3O4-CuO nanoclusters are not activated by dynamic pulse electric field.

[0169] Comparative Example 2: The difference between this comparative example and Example 3 is that no halogenated alkane dehalogenase stabilizer is added in S6.

[0170] Comparative Example 3: The difference between this comparative example and Example 3 is that the Fe3O4-CuO nanoclusters are not activated by dynamic pulse electric field, and no halogenated alkane dehalogenase stabilizer is added in S6.

[0171] Experimental Example:

[0172] 1. Dechlorination efficiency verification;

[0173] Test steps:

[0174] Sampling point setting: online chloride ion detector (HJ 543-2015) is set at the outlet of the dry dechlorination section (after S5) and the outlet of the wet dechlorination section (after S6).

[0175] Detection method:

[0176] Dry section Cl2 removal rate: iodometric method (GB / T 16157) is used to detect the Cl2 concentration at the inlet and outlet.

[0177] Wet section Cl2 removal rate: residual Cl2 is calculated by the consumption of sodium thiosulfate solution (GB 16297-1996).

[0178] Data recording: collect once an hour, continuously monitor for 24 hours and take the average value.

[0179] 2. Alkali consumption and waste liquid volume verification;

[0180] Test steps:

[0181] Alkali consumption: the circulation amount of sodium thiosulfate solution in the wet section is 4L / m 3 Metering (recorded by a flow meter).

[0182] Waste liquid production: measure the volume of waste liquid after concentration by a multi-effect evaporator (refer to HJ 884-2018 evaporation residue detection).

[0183] Waste liquid component analysis: detect the Cl - and SO4 2- concentrations in the concentrated liquid (GB / T 11896, GB / T 5750.5).

[0184] 3. By-product purity verification;

[0185] Test steps:

[0186] Crystalline salt sampling: collect NaCl / Na2SO4 mixed salt samples from the outlet of the multi-effect evaporator.

[0187] Purity detection: detect the Cl - content of NaCl according to Industrial Salt (GB / T 5462-2015).

[0188] Detect the SO4 2- content of Na2SO4 according to Industrial Anhydrous Sodium Sulfate (GB / T 6009-2014).

[0189] Impurity analysis: detect the heavy metal (Fe, Cu, etc.) residues by ICP-MS (GB / T 33042-2016).

[0190] The test results are shown in the following table:

[0191] Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Total Cl2 removal 99.2％ 99.1％ 99.3％ 98.5％ 99.0％ 98.1％ Sodium thiosulfate consumption 2.8 t / h 2.7 t / h 2.6 t / h 3.1 t / h 3.3 t / h 5.1 t / h Waste liquid production 3.3m 3 / h]] 3.2 m 3 / h]] 3.5m 3 / h]] 3.4 m 3 / h]] 4.8 m 3 / h]] 5.2 m 3 / h]] NaCl purity (Cl - ) 99.6％ 99.4％ 99.8％ 99.2％ 99.7％ 99.1％ Na2SO4purity (SO4 2- )]]> 99.3％ 99.1％ 99.5％ 99.1％ 99.4％ 99.2％ Heavy metal residue (Fe) ≤ 15 ppm ≤ 18 ppm ≤ 13 ppm ≤ 20 ppm ≤ 14 ppm ≤ 16 ppm

[0192] The present application proves by comparison experiments that the introduction of halogenated alkyl dehalogenase as a stabilizer into the sodium thiosulfate solution system significantly optimizes the reaction process, and realizes the synchronous reduction of sodium thiosulfate consumption and waste liquid production;

[0193] The haloalkane dehalogenase plays a key role in catalyzing and stabilizing the reaction system. The molecular structure of the haloalkane dehalogenase can form a synergistic site with the active component in the sodium thiosulfate solution, so as to improve the selectivity and efficiency of the sodium thiosulfate participating in the reaction by adjusting the chemical potential of the local microenvironment. The enzyme catalysis mechanism effectively avoids the consumption of sodium thiosulfate in the non-target reaction, and reduces the generation of reaction byproducts, thereby systematically reducing the waste liquid discharge.

[0194] Through comparison and verification, the activation treatment of Fe3O4-CuO nanoclusters by a dynamic pulse electric field can significantly improve the removal efficiency of chlorine in the system, and effectively reduce the residual concentration of Fe element in the byproducts NaCl and Na2SO4, thereby substantially improving the purification level of the byproducts.

[0195] When the dynamic pulse electric field acts on the Fe3O4-CuO nanoclusters, the high-frequency electric field change can instantaneously polarize the electron distribution on the surface of the nanoclusters, and activate the active crystal surface and active site in the nanoclusters. The electric field activation not only enhances the adsorption and activation ability of the nanoclusters to chlorine molecules, but also improves the immobilization efficiency of the Fe 3+ and other heavy metal ions. In the subsequent byproduct formation process, the activated nanoclusters can more effectively enrich and immobilize Fe elements on the surface, thereby reducing the residual concentration of Fe in the byproducts.

[0196] Through comparison experiments, it is revealed that there is a significant synergistic effect between the haloalkane dehalogenase and the Fe3O4-CuO nanoclusters activated by the dynamic pulse electric field. When the two work together, they exhibit a synergistic effect beyond the sum of the individual effects in terms of reducing the consumption of sodium thiosulfate, reducing the amount of waste liquid, and improving the purity of the byproducts.

[0197] The synergistic mechanism of the haloalkane dehalogenase and the Fe3O4-CuO nanoclusters is reflected in multiple aspects. On the one hand, the catalytic reaction of the haloalkane dehalogenase can optimize the chemical microenvironment of the reaction system, making the active sites of the Fe3O4-CuO nanoclusters more easily exposed and involved in the reaction. On the other hand, the Fe3O4-CuO nanoclusters activated by the dynamic pulse electric field can immobilize the haloalkane dehalogenase molecules through the active sites on the surface, forming an enzyme-nanocluster complex. This complex can simultaneously exert the efficient catalysis of the enzyme and the adsorption enrichment of the nanoclusters, significantly improving the synergistic catalytic efficiency of the entire reaction system, thereby achieving synergistic effect in reducing consumption and improving purity.

[0198] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A process for dechlorination of fumed silica tail gas, characterized in that, Includes the following steps: S1: Exhaust gas pretreatment and particulate matter separation; The fumed silica tail gas is separated by a three-stage cyclone separator and filtered by a bag filter. S2: Preparation and modification of germanium molecular sieve support; Pretreatment of γ-Al2O3 support: γ-Al2O3 was calcined to remove surface hydroxyl groups, cooled and then immersed in nitric acid solution, washed and dried to obtain pretreated γ-Al2O3; Germanium doping modification; Pretreated γ-Al2O3 was mixed with sodium germanate solution and hydrothermally reacted to form a Ge-Al2O3 molecular sieve framework. The Ge-Al2O3 molecular sieve framework was immersed in NH4NO3 solution for ion exchange, and then calcined to obtain the Ge-AN-Al2O3 support. S3: Fe-Cu bimetallic nanoclusters supported; Fe precursor loading was used to prepare Fe(NO3)3 solution, which was then impregnated with Ge-AN-Al2O3 support, ultrasonically dispersed and dried. Cu precursor loading was prepared into Cu(NO3)2 solution, and then Ge-AN-Al2O3 support was impregnated twice and dried. Reduction-oxidation activation: After reducing the Ge-AN-Al2O3 support loaded with Fe-Cu precursor in a mixed H2 / N2 atmosphere, the atmosphere was switched to air, and Fe3O4-CuO nanoclusters were oxidized to form Fe3O4-CuO nanoclusters. S4: Dynamic pulsed electric field activation of Fe3O4-CuO nanoclusters; S5: Dry dechlorination; A dry dechlorination agent is filled into a fixed-bed reactor, and dry adsorption of fumed silica tail gas is promoted under the assistance of a pulsed electric field. S6: Wet reduction synergistic dechlorination; Prepare a sodium thiosulfate solution, add haloalkane dehalogenase, adjust the pH to obtain a dechlorinated solution; The fumed silica tail gas after dry adsorption is subjected to wet reduction with dechlorination liquid to obtain dechlorinated tail gas. Byproduct recovery: The dechlorination liquid is concentrated and crystallized by a multi-effect evaporator, and then separated by centrifugation to obtain industrial-grade NaCl and Na2SO4; S7: Photothermal coupling regeneration; The saturated dry dechlorination agent is heated and decomposed at a constant temperature to remove the adsorbed Cl2 / HCl. At the same time, ultraviolet light is applied to stimulate free radical decomposition and release Cl2. Regeneration tail gas treatment: The Cl2 released during regeneration is introduced into the dechlorination liquid for wet reduction, forming a closed-loop cycle.

2. The dechlorination process for fumed silica tail gas according to claim 1, characterized in that, S1 specifically refers to exhaust gas pretreatment and particulate matter separation; The fumed silica tail gas is sequentially passed through a three-stage cyclone separator to remove silica particles. The first-stage cyclone separator, with a temperature of 180-200℃ and an inlet flow velocity of 15-20m / s, removes particles >50μm. Two-stage cyclone separator, temperature 150-170℃, inlet flow velocity 25-30m / s, removes 10-50μm particles; Three-stage cyclone separator, temperature 120-140℃, inlet flow velocity 35-40m / s, removes 1-10μm particles.

3. The dechlorination process for fumed silica tail gas according to claim 1, characterized in that, S2 specifically involves calcining γ-Al2O3 with a particle size of 50-100μm at 500-600℃ for 2-4h to remove surface hydroxyl groups, immersing it in nitric acid solution after cooling, stirring at 60-72℃ for 30-50min, washing until neutral, and drying at 90-110℃ for later use to obtain pretreated γ-Al2O3. Sodium germanate is dissolved in deionized water at a concentration of 4-6 wt%, and the pH is adjusted by ammonia water to obtain the impregnation solution; Pretreated γ-Al2O3 and impregnation solution are mixed at a solid-liquid ratio of 1-1.5:5-7 and hydrothermally reacted at 160-180℃ for 4-6 hours to form a Ge-Al2O3 molecular sieve framework. The Ge-Al2O3 molecular sieve framework was immersed in a 0.1-0.2 mol / L NH4NO3 solution, and ion exchange was carried out at 70-80℃ for 1-2 h, followed by calcination at 550-620℃ for 2-3 h to form H-type acidic sites, thus obtaining the Ge-AN-Al2O3 support.

4. The dechlorination process for fumed silica tail gas according to claim 1, characterized in that, S3 is specifically prepared as follows: a 10-15 wt% Fe(NO3)3 solution is prepared, impregnated with Ge-AN-Al2O3 support, ultrasonically dispersed for 20-30 min, and dried at 100-120℃; Prepare a 5-8 wt% Cu(NO3)2 solution, impregnate the Ge-AN-Al2O3 support twice, and dry at 100-120℃; The Ge-AN-Al2O3 support loaded with Fe-Cu precursor was placed in a tube furnace and reduced at 300-400℃ for 30-60 min under a mixed H2 / N2 atmosphere. Then, the atmosphere was switched to air and oxidized at 500-600℃ for 1-2 h to form Fe3O4-CuO nanoclusters.

5. The dechlorination process for fumed silica tail gas according to claim 1, characterized in that, Specifically, S4 involves placing Fe3O4-CuO nanoclusters within a fixed-bed reactor, with titanium alloy mesh electrodes embedded within the reactor. The distance between the electrodes and the dechlorinating agent bed is ≤2mm, and the bed packing density is ≥800kg / m³. 3 ; A continuous pulsed electric field is applied to the reactor, with a voltage of 2-3V, a frequency of 100-500Hz, and a temperature of 80-150℃.

6. The dechlorination process for fumed silica tail gas according to claim 1, characterized in that, S5 specifically refers to: a fixed-bed reactor equipped with three stages of series adsorption beds, filled with a dry dechlorination agent with a density of 600-800 kg / m³. 3 ; At temperatures of 120-180℃ and air velocities of 1000-1500 h⁻¹ -1 Under pressure of -0.5 to -1 kPa and pulsed electric field assistance, the dry adsorption of Cl2 ionization in fumed silica tail gas is promoted.

7. The dechlorination process for fumed silica tail gas according to claim 1, characterized in that, S6 specifically involves preparing a 5-8 wt% sodium thiosulfate solution, adding 0.4-0.6% haloalkane dehalogenase, and adjusting the pH to 8-10 using NaOH to obtain a dechlorinated solution. The fumed silica tail gas after dry adsorption is subjected to wet reduction with dechlorination liquid to obtain dechlorinated tail gas. The dechlorination solution was concentrated and crystallized by a multi-effect evaporator, and then separated by centrifugation to obtain industrial-grade NaCl and Na2SO4.

8. The dechlorination process for fumed silica tail gas according to claim 1, characterized in that, S7 specifically involves: under N2 protection, saturated dry dechlorination agent is subjected to gradient heating and then kept at a constant temperature for 1.5-2 hours to decompose the adsorbed Cl2 / HCl. Simultaneous application of ultraviolet light excites ·OH free radicals on the surface of Fe-Cu nanoclusters, deeply decomposes organochlorine pollutants to release Cl2, and the regenerated Cl2 is introduced into the dechlorination liquid for wet reduction, forming a closed-loop cycle.

Images