Chlor-alkali electrolysis-waste catalyst recovery coupling integration process without waste circulation

Abstract

The invention belongs to the technical field of chlor-alkali-waste catalyst recovery coupling, and particularly relates to a waste-free circulating chlor-alkali electrolysis-waste catalyst recovery coupling integrated process which comprises the following steps: chlor-alkali electrolysis: circulating and returning a refined NaCl solution to a chlor-alkali electrolytic tank and carrying out chlor-alkali electrolysis to prepare Cl2, HCl and NaOH solutions; preparing acid liquor and alkali liquor; crushing the waste catalyst and carrying out alkaline leaching reaction; carrying out oxidative acidification reaction; pickling; removing impurities; performing extraction; performing back extraction; inducing polymerization extraction; oxidizing and degrading COD (Chemical Oxygen Demand) while adjusting the pH value of the system to be neutral, and then adding chemical salt to prepare until the concentration of a high-purity sodium chloride solution is reached, so as to obtain a refined sodium chloride solution and reuse the refined sodium chloride solution to a chlor-alkali electrolysis process. According to the integration process, waste-free circulation is achieved, and the obtained products are diversified, excellent in performance and high in economic value.

Description

Technical Field

[0001] The invention belongs to the technical field of chlor-alkali-waste catalyst recovery coupling, and in particular relates to a coupled integrated process of chlor-alkali electrolysis-waste catalyst recovery without waste circulation. Background Art

[0002] The high-quality development of the petrochemical industry is related to green and low-carbon development and the improvement of people's livelihood and welfare, and the disposal of solid and hazardous waste is one of the key tasks, among which the disposal of waste catalysts and resource reuse have become the mainstream direction.

[0003] Industrial catalysts are an important part of the chemical industry and complement each other. Industrial catalysts can be divided into oil refining catalysts, chemical catalysts and environmental catalysts. The current scale of catalysts in the petrochemical industry is 410,000 tons, chemical catalysts are 520,000 tons, and denitrification catalysts among environmental catalysts are 800,000 tons. A large number of discarded industrial catalysts have become the most important industrial hazardous wastes. Their resource disposal is limited by the high amount of wastewater and waste salt, resulting in poor economic efficiency.

[0004] The chlor-alkali industry is a basic raw material industry that produces caustic soda, chlorine and hydrogen using sodium chloride as raw material. It plays a pivotal role in the development of the global economy. According to data, my country's caustic soda production reached 34.64 million tons in 2019, a year-on-year increase of 0.5%. As of 2020, my country's total caustic soda production was about 36.43 million tons. At the same time, due to resource and environmental constraints, in response to global climate change, energy conservation and emission reduction have become limiting factors in the development of the chlor-alkali industry.

[0005] Among the improvements in the existing technology, only process adjustments and optimizations are carried out within the industry, which limits the improvement effect.

[0006] Patent document CN 109208024A discloses a chlor-alkali production process, which only makes minor optimization and improvements to the existing process. Although it also involves the issue of saving chlor-alkali resources, it solves the problem of increased consumption of the amount of alkali required for subsequent treatment and the amount of brine treatment due to the addition of acid to the anode liquid through the recycling of brine. However, on the one hand, this process does not solve the problem of high energy consumption in the preparation, concentration and drying of caustic soda. On the other hand, it only performs process optimization within the industry and does not involve process coupling between different fields.

[0007] Therefore, it is worthwhile to study how to promote the coupled development of petrochemicals with building materials, metallurgy, energy conservation and environmental protection industries, and further try to improve the efficiency of resource recycling through integrated processes between different fields. Summary of the invention

[0008] The purpose of the present invention is to provide a coupled integrated process of chlor-alkali electrolysis-waste catalyst recovery without waste circulation, in view of the problems in the existing resource utilization process; the intermediate product of the chlor-alkali process is used as the raw material of the waste catalyst recovery process, and the high-salt wastewater recovered is used for electrolysis of alkali solution and hydrochloric acid solution in the chlor-alkali industry, so as to realize the coupled waste-free circulation integrated process of the chlor-alkali technology field and the solid waste recovery technology field; the integrated process not only realizes waste-free circulation, but also has low cost and energy consumption, short process, high efficiency and no pollution, and the obtained products are diverse and have excellent performance, and have high economic value.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A coupled integrated process for chlor-alkali electrolysis and waste catalyst recovery without waste circulation comprises the following steps:

[0011] (1) Chlor-alkali electrolysis: The purified NaCl solution obtained by catalyst recovery and purification is circulated back to the chlor-alkali electrolysis cell and subjected to chlor-alkali electrolysis to prepare Cl2, HCl and NaOH solutions;

[0012] (2) Acid solution preparation: Cl2 and H2 obtained by electrolysis are introduced into a synthesis furnace for reaction to prepare HCl; the obtained HCl is then mixed with deionized water to prepare an acid solution; the concentration of the acid solution is preferably 5wt%-20wt% (e.g., 6wt%, 10wt%, 15wt%, 18wt%);

[0013] (3) Preparation of alkali solution: adding deionized water to the NaOH solution obtained by electrolysis to prepare alkali solution; the concentration of the alkali solution is preferably 10wt%-30wt% (e.g., 12wt%, 15wt%, 20wt%, 25wt%);

[0014] (4) Alkali leaching reaction: crushing the waste catalyst to be recycled (e.g., put into a Raymond crusher) to a particle size of 200-300 mesh (e.g., 210 mesh, 250 mesh, 280 mesh) to obtain a crushed waste catalyst powder; the waste catalyst is a waste environmentally friendly catalyst containing vanadium-tungsten-molybdenum-titanium;

[0015] Then, the waste catalyst powder is evenly mixed with the prepared alkali solution and the inducer, and then an alkali leaching reaction is performed;

[0016] (5) Oxidation acidification reaction: After the alkaline leaching reaction in step (4), the Cl2 prepared in step (1) is introduced into the reaction kettle while stirring, so that the gas and the solid and liquid are fully contacted and mixed until the pH value is reduced to 9-10 (e.g., 9.5), and further stirred to carry out oxidation acidification reaction, and the stirring time is 1.0-1.5h (e.g., 1.2h, 1.4h);

[0017] The product after the reaction is subjected to solid-liquid separation, and is slurried and washed (e.g., 1-3 times) until the pH value of the solution is 13-14 (e.g., 13.5), and a solution i and a solid i are separated;

[0018] (6) acid washing: the solid i obtained in step (5) is mixed with the acid solution prepared in step (2) to an initial pH of 1-4 (e.g., 2, 3, 3.5), and then the solid-liquid separation is performed after the acid washing reaction to obtain a solution ii and a solid ii;

[0019] (7) removing impurities: mixing the obtained solution i and solution ii, adding the acid solution prepared in step (2) until the pH of the mixed solution is 10-10.5, then adding a precipitant (e.g., magnesium sulfate heptahydrate, magnesium chloride, magnesium nitrate), stirring until dissolved, and reacting; after the reaction is completed, sedimentation and solid-liquid separation are performed to separate solution iii and solid iii (which can be used as general solid waste);

[0020] (8) adding the acid solution to the obtained solution iii to adjust the pH of the system to 2.5-4.5, and then adding the acidified composite extractant for extraction to obtain an extractant and a high-purity NaCl solution (the concentration of the high-purity NaCl solution may be 10 wt%-15 wt%, such as 12 wt%, 14 wt%);

[0021] (9) adding aqueous ammonia to the extract (organic solution) obtained in step (8) for back extraction to obtain a high-purity vanadium-tungsten solution and an organic phase; optionally, recycling the organic phase;

[0022] (10) adding the prepared acid solution (e.g., a concentration of 10 wt%) to the high-purity NaCl solution obtained in step (8) until the pH of the system is 1.5-3 (preferably 2), then adding a P-type inducer and stirring to carry out a VWP induced polymerization reaction; then repeating the extraction operation of step (8) to obtain a high-purity sodium chloride solution with V / W heavy metals removed; wherein the induced polymerization reaction time is 0.5h-2.5h (e.g., 1.0h, 1.5h, 2.0h), and the reaction temperature is room temperature;

[0023] (11) The sodium hydroxide solution obtained by electrolysis and Cl2 are introduced into the high-purity sodium chloride solution from which V / W heavy metals have been removed, and the mixture is fully mixed and reacted (for example, reacting at 50-80° C. for 0.5-1.5 h, wherein NaOH reacts with Cl2 to generate NaClO for oxidative degradation of COD). While oxidative degradation of COD is performed, the pH of the system is adjusted to neutral, and then chemical salts are added to prepare a high-purity sodium chloride solution with a concentration of 300-350 g / L (for example, 310 g / L, 320 g / L, 330 g / L, 340 g / L), thereby obtaining a refined sodium chloride solution and recycling it to the chlor-alkali electrolysis process of step (1).

[0024] In step (1), the refined NaCl solution is used as the anolyte and can be fed into the ion membrane electrolyzer at a flow rate of 150-500 kg / h (e.g., 200 kg / h, 300 kg / h, 400 kg / h), and electrolysis is performed under the action of direct current, and Cl2 is produced at the anode and NaOH solution and H2 are produced at the cathode. According to the coupled integrated process provided by the present invention, in some embodiments, in step (1), the concentration of the refined NaCl solution circulated back to the chlor-alkali electrolytic cell is 300-350 g / L, such as 305 g / L, 310 g / L, 315 g / L, 320 g / L, 330 g / L, 340 g / L.

[0025] In some embodiments, in step (1), the current of the chlor-alkali electrolysis is 4-6 kA (e.g., 4.5 kA, 5 kA, 5.3 kA, 5.6 kA).

[0026] In some embodiments, in step (1), the concentration of the NaOH solution is 31-40 wt%, such as 32 wt%, 35 wt%, 38 wt%.

[0027] In some embodiments, in step (2), the molar ratio of H2 to Cl2 is (1.15-1.1):1, such as 1.16:1; the reaction conditions are conventionally selected in the art and will not be described in detail here.

[0028] In some embodiments, in step (4), the waste catalyst is selected from one or more of a waste denitration catalyst, a waste hydroreduction catalyst, a waste oil catalyst and a waste hydroreforming catalyst.

[0029] In some embodiments, in step (4), the inducer is sodium titanate and / or sodium phosphate; the amount of the inducer added is 0.1%-1% (e.g., 0.2%, 0.4%, 0.5%, 0.8%) of the mass of the waste catalyst powder; the amount of alkali solution added is calculated on a liquid-to-solid ratio, and the liquid-to-solid ratio (l:s) of the alkali solution to the waste catalyst is 1:1-3:1 (e.g., 1.5:1, 2:1, 2.5:1) mL / g.

[0030] In some embodiments, in step (4), the process conditions of the alkali leaching reaction include: reaction temperature of 100-240°C (eg, 120°C, 150°C, 200°C), reaction time of 30-120min (eg, 40min, 60min, 100min).

[0031] In some embodiments, in step (6), the concentration of the acid solution is 5wt%-20wt% (e.g., 6wt%, 10wt%, 15wt%), and the amount of the acid solution added is calculated based on the liquid-to-solid ratio, and the liquid-to-solid ratio (l:s) of the acid solution to the solid is 1:1-3:1 (e.g., 1.2:1, 1.5:1, 1.8:1, 2:1, 2.5:1) mL / g. During the pickling process, a pickling aid (e.g., titanium trichloride) can be optionally added, which can be used to remove iron impurities contained in the waste catalyst.

[0032] In some embodiments, in step (6), the process conditions of the pickling reaction include: a reaction temperature of 70°C-90°C (e.g., 75°C, 80°C, 85°C), a reaction time of 45-90min (e.g., 50min, 60min, 80min); after solid-liquid separation, pulping and cleaning are optionally performed, and the number of pulping and cleaning times is 4-7 times (e.g., 5 times, 6 times).

[0033] In step (6), the solid ii is washed with water until the conductivity of the filtrate is less than 400 μs / cm; the solid ii obtained by washing is dried and calcined at a certain temperature to obtain a reconstructed catalyst carrier; wherein the drying temperature is 100-250°C and the drying time is 90-180 min; after drying, it is calcined at 550-600°C for 3-4 h, and the components and other indicators of the powder are detected to obtain a reconstructed catalyst carrier.

[0034] In some embodiments, in step (7), the amount of magnesium sulfate heptahydrate added is 5wt%-20wt% of the initial waste catalyst powder mass, for example, 6wt%, 10wt%, 15wt%, 18wt%.

[0035] In some embodiments, in step (7), the process conditions of the reaction include: reaction temperature of 65-95°C (e.g., 70°C, 80°C, 90°C), reaction time of 60-180min (e.g., 80min, 120min, 150min); sedimentation time of 30-120min (e.g., 40min, 60min, 80min, 90min, 100min).

[0036] The initial solution in step (8) is a mixed solution containing sodium chloride, sodium hydroxide, sodium vanadate, sodium tungstate, and a small amount (ppm level) of calcium chloride and a small amount (ppm level) of magnesium chloride. In step (8), the mixed solution is selectively extracted by acidification and a composite extractant, so that most of the vanadium and tungsten in the mixed solution are extracted and recovered, and a solution containing sodium chloride and a small amount of hydrochloric acid, a trace amount of calcium chloride, a trace amount of magnesium chloride, a trace amount of vanadium, and a trace amount of tungsten (calcium, magnesium, vanadium, and tungsten are all at ppm level) can be obtained.

[0037] In some embodiments, in step (8), the composite extractant is a mixture of main extractant + co-extractant + phase regulator + diluent; wherein the volume ratio of main extractant: co-extractant: phase regulator: diluent = (4-6): (2-5): (1-3): (25-30), for example, 6:5:2:27, 4:2:2:25, 5:3:2:26.

[0038] In some embodiments, the main extractant is one or more of a primary amine, a secondary amine, a tertiary amine and a quaternary ammonium salt; for example, N235;

[0039] In some embodiments, the synergist is a lipid; it can be selected from tributyl phosphate and / or trialkylphosphine oxide, such as TBP;

[0040] In some embodiments, the phase modifier is a higher alcohol, such as n-butanol, sec-octanol;

[0041] In some embodiments, the diluent is sulfonated kerosene.

[0042] In some embodiments, in step (8), the extraction process conditions include: the A / O of the extraction is 5:1-12:1 (e.g., 6:1, 8:1, 10:1); the extraction time is 1-5 min (e.g., 2 min, 3 min, 4 min);

[0043] The extraction is centrifugal extraction, and the centrifuge speed is 46-50 Hz (eg, 48 Hz).

[0044] In some embodiments, in step (9), the concentration of the aqueous ammonia is 7.5 wt%-15 wt% (eg, 8 wt%, 10 wt%, 12 wt%).

[0045] In some embodiments, the A / O ratio of the stripping is 1:1-1:3, for example, 1:1.5, 1:2, 1:2.5.

[0046] In some embodiments, in step (10), the P-type inducer is selected from one or more of Na3PO4, Na2HPO4 and NaH2PO4.

[0047] In some embodiments, the amount of the P-type inducer added is calculated as a solid-liquid mass ratio, solid-liquid mass ratio (s:l) = 0.5:100-2.5:100, for example, 1:100, 1.5:100, 2.0:100.

[0048] In some embodiments, in step (11), the mass ratio of Cl2 (calculated as pure gas) added to the high-purity sodium chloride solution for removing V / W heavy metals is 0.5:100-2.5:100 (for example, 0.8:100, 1.0:100, 1.5:100, 2.0:100).

[0049] In some embodiments, in step (11), the amount of sodium hydroxide solution added is based on the mass of sodium hydroxide; in the high-purity sodium chloride solution for removing V / W heavy metals, the mass ratio of the amount of sodium hydroxide added (based on the solid sodium hydroxide in the sodium hydroxide solution) to the solution is 1.25:100-4.5:100 (for example, 1.5:100, 2.0:100, 2.5:100, 3.0:100, 3.5:100, 4.0:100). A portion of the added sodium hydroxide is used to neutralize the free acid in step (10), and the other portion reacts with Cl2 to generate oxidizing NaClO.

[0050] In some embodiments, in step (11), the reaction temperature is 35°C-45°C (eg, 40°C); the reaction time is 0.5h-2.5h (eg, 2h).

[0051] In the present invention, some equations that may be involved in each process of waste catalyst recovery are as follows:

[0052] M x O y +2n NaOH=n Na2O*M x O y +n H2O(dissolved);

[0053] Na2O*M x O y + 2HCl = NaCl + H2O (separation and purification);

[0054] NaOH+HCl=NaCl+H2O (excess alkali neutralization);

[0055] Cl2+2NaOH=NaCl+NaClO+H2O;

[0056] 2NaOH+As2O3=2NaAsO2+H2O (dissolution and separation of impure arsenic);

[0057] NaClO+2NaOH+NaAsO2=NaCl+Na3AsO4+H2O (low-valent arsenic oxidation).

[0058] In the present invention, some equations that may be involved in each process of refining sodium chloride solution are as follows:

[0059] 3MgCl2+2Na3AsO4=Mg3(AsO4)3↓+6NaCl (impurity removal);

[0060] VO 3- +WO4 2- +P 诱导剂 =[H2P2W 14 V4O 62 ](heavy metal induced polymerization);

[0061] [H2P2W 14 V4O 62 ]+N-extractant=[H2P2W 14 V4O 62 ]-N-Extractant (vanadium and tungsten removal);

[0062] C2+COD→CO+H2O (organic matter degradation).

[0063] There are many impurity elements such as V / W / As in the waste catalyst, and the properties of the sodium chloride wastewater generated during the recovery process have a great impact on the chlor-alkali electrolysis of sodium chloride process. In order to solve the harmful impurities in the sodium chloride wastewater, the coupled integrated process of the present invention is provided with an oxidation acidification process, which consumes free NaOH to reduce the pH on the one hand, and on the other hand, the strong oxidizing property of the generated NaClO promotes the efficient dissolution and oxidation of low-valent arsenic in the waste catalyst, so that the subsequent impurity removal process can reduce the arsenic content to the ppb level (the precipitation generated by high-valent arsenate and impurity removers such as magnesium sulfate and magnesium chloride is more stable, and the residual arsenic content is lower), so as to meet the requirements of chlor-alkali electrolysis for the As content in the sodium chloride solution.

[0064] In the present invention, the extraction operation of step (8), the stripping operation of step (9) and the VWP induced polymerization reaction of step (10) constitute the "induced polymerization extraction" process; the key to this process is to perform extraction and stripping operations after vanadium tungsten induced polymerization to form polyanions, and before vanadium tungsten induced polymerization, the solution iii obtained after impurity removal can also be subjected to extraction and stripping operations.

[0065] In the "Induced Polymerization Extraction" process, VO 3- +WO4 2- +P 诱导剂 =[H2P2W 14 V4O 62](polymer), utilizing the polymerization effect of the inducer to realize the efficient extraction and recovery of low-concentration heavy metals VW; compared with conventional extraction, the heavy metal V / W content in the NaCl wastewater obtained after the induced polymerization extraction process reaches below ppb level, which can meet the requirements of chlor-alkali electrolysis for the W / V content in the sodium chloride solution; in addition, the solution after the induced polymerization extraction is oxidized by the chlorine gas generated by electrolysis, and the COD content is 80-120ppm, which is mainly attributed to the incomplete separation of the organic phase and the inorganic phase during the extraction process. The present invention makes full use of the concept of zero-waste circulation and utilizes the oxidizing property of the chlorine gas generated by electrolysis to realize the oxidative degradation of organic matter in the waste solution recovered by extraction, so that the COD content is reduced to below 50ppm, meeting the requirements of the chlor-alkali electrolysis process for the sodium chloride solution.

[0066] The present invention is based on the inventive concept of collaborative innovation in two different technical fields of chlor-alkali and solid waste recovery. The intermediate products of the chlor-alkali industry (alkali solution and acid solution obtained by electrolysis) are used as raw materials for the waste catalyst recovery process. At the same time, the refined high-salt wastewater generated is recycled back to the electrolysis process as raw materials, realizing the coupling and waste-free cycle between the chlor-alkali and solid waste recovery fields. In this coupled integrated process, the process of circulating and electrolyzing the obtained refined sodium chloride solution is an important part of the coupling process and is indispensable; if the ready-made acid or alkali solution is directly added, the coupling process cannot be realized; and the chlor-alkali electrolysis process is used in the coupling process, which can save the wastewater treatment process of waste catalyst recovery evaporation and crystallization. Chlor-alkali electrolysis is the key to realizing the resource utilization of catalyst recovery wastewater.

[0067] Through this process coupling, the wastewater treatment required in the waste solid recycling field and the additional salt purchase and dissolution process required in the chlor-alkali field are eliminated, solving the industry pain points of recycling and treating high-salt wastewater, and achieving energy conservation and consumption reduction in these two fields at the same time. In addition, this coupling process can also eliminate the evaporation and crystallization of high-salt wastewater and chemical salt disposal processes and equipment in the waste catalyst recovery, and at the same time eliminate high-energy-consuming processes such as multi-stage concentration and drying in the preparation of caustic soda in the traditional chlor-alkali industry. Through technological collaborative innovation, it promotes the coupled development of different industries, improves the efficiency of resource recycling, reduces process flows, and achieves collaborative carbon reduction.

[0068] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0069] (1) The present invention can achieve the synergistic coupling of the chlor-alkali-waste industrial catalyst recovery process, solve the limitation of wastewater and waste salt on the waste catalyst recovery process, and achieve waste-free circulation while obtaining recovered solids and recovered liquids that meet the use requirements, thereby enriching the system categories of the obtained final products and improving direct economic benefits;

[0070] (2) The present invention can save the high-salt wastewater treatment process and equipment, as well as the multi-stage concentration and drying process of chlor-alkali to prepare caustic soda, and save the raw material resources of sodium chloride in the electrolysis process through the circulation of high-salt water, reduce the process flow and raw materials, and improve indirect benefits;

[0071] (3) Through process coupling, high-energy-consuming links such as concentration, evaporation and drying in the two fields of chlor-alkali and waste industrial catalyst recovery are eliminated, achieving energy conservation and consumption reduction and reducing wastewater and waste residue, thereby reducing pollution and carbon emissions in a coordinated manner, which is in line with the current dual-carbon trend and has great environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a schematic diagram of the process of the coupling integration process described in one embodiment of the present invention. DETAILED DESCRIPTION

[0073] In order to understand the technical features and contents of the present invention in detail, the preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described in the embodiments, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described here.

[0074] In some embodiments of the present invention, a coupled integrated process of chlor-alkali electrolysis and waste catalyst recovery without waste circulation is described in detail in detail. Figure 1 As shown, the following steps are included:

[0075] (1) Chlor-alkali electrolysis: The refined NaCl solution obtained by catalyst recovery and purification is circulated back to the chlor-alkali electrolysis cell and subjected to chlor-alkali electrolysis. The current of chlor-alkali electrolysis is 4-6 kA to prepare Cl2, HCl and NaOH solutions; the concentration of NaOH solution is 31-40 wt%.

[0076] (2) Acid solution preparation: Cl2 and H2 obtained by electrolysis are introduced into a synthesis furnace for reaction to prepare HCl; the obtained HCl is then mixed with deionized water to prepare an acid solution; the concentration of the acid solution may be 5wt%-20wt%;

[0077] (3) Preparation of alkali solution: adding deionized water to the NaOH solution obtained by electrolysis to prepare alkali solution; the concentration of the alkali solution can be 10wt%-30wt%;

[0078] (4) Alkali leaching reaction (surface reconstruction): crushing the waste catalyst to be recycled to a particle size of 200-300 mesh to obtain a crushed waste catalyst powder; the waste catalyst is a waste environmentally friendly catalyst containing vanadium-tungsten-molybdenum-titanium;

[0079] Then, the waste catalyst powder is evenly mixed with the prepared alkali solution and the inducer, and then an alkali leaching reaction is carried out; the inducer is sodium titanate and / or sodium phosphate; the amount of the inducer added is 0.1%-1% of the mass of the waste catalyst powder, and the liquid-solid ratio (l:s) of the alkali solution to the waste catalyst is 1:1-3:1 mL / g; the temperature of the alkali leaching reaction is 100-240° C., and the reaction time is 30-120 min;

[0080] (5) Oxidation and acidification reaction: After the alkaline leaching reaction in step (4), the Cl2 prepared in step (1) is introduced into the reaction kettle while stirring, so that the gas and the solid and liquid are fully contacted and mixed until the pH value is reduced to 9-10, and further stirred to carry out oxidation and acidification reaction, and the stirring time is 1.0-1.5h;

[0081] The product after the reaction is subjected to solid-liquid separation, and is slurried and washed for 3-5 times until the pH value of the solution is 13-14, and a solution i and a solid i are separated;

[0082] (6) secondary pickling: the solid i obtained in step (5) is mixed with the acid solution prepared in step (2) to an initial pH of 1-4, pickled at 70° C.-90° C. for 45-90 min, and then the solid and liquid are separated, and pulping and washing are optionally performed, the number of pulping and washing is 4-7 times, and solution ii and solid ii are separated;

[0083] The concentration of the acid solution is 5wt%-20wt%, and the liquid-to-solid ratio (l:s) of the acid solution to the solid is 1:1-3:1mL / g;

[0084] (7) removing impurities: mixing the obtained solution i and solution ii, adding the acid solution prepared in step (2) until the pH value of the mixed solution is 10-10.5, then adding magnesium sulfate heptahydrate and stirring until dissolved, and reacting at 65-95° C. for 60-180 min; the amount of magnesium sulfate heptahydrate added is 5wt%-20wt% of the initial mass of the spent catalyst powder; after the reaction is completed, the solution iii and the solid iii are separated by sedimentation and solid-liquid separation;

[0085] (8) adding the acid solution to the obtained solution iii to adjust the pH of the system to 2.5-4.5, then adding the acidified composite extractant for centrifugal extraction, the A / O ratio of the extraction is 5:1-12:1, the extraction time is 1-5 min, and the centrifuge speed is 46-50 Hz; obtaining an extractant and a high-purity NaCl solution;

[0086] In the composite extractant, the volume ratio of main extractant: co-extractant: phase regulator: diluent = (4-6): (2-5): (1-3): (25-30);

[0087] (9) adding aqueous ammonia (with a concentration of 7.5 wt% to 15 wt%) to the extract obtained in step (8) for stripping, wherein the A / O ratio of the stripping is 1:1 to 1:3, to obtain a high-purity vanadium-tungsten solution and an organic phase; optionally, recycling the organic phase;

[0088] (10) adding the prepared acid solution to the high-purity NaCl solution obtained in step (8) until the system pH is 1.5-3, then adding a P-type inducer and stirring and mixing to carry out a VWP induced polymerization reaction, wherein the P-type inducer is selected from one or more of Na3PO4, Na2HPO4 and NaH2PO4; the amount of the P-type inducer added is calculated as a solid-liquid mass ratio, and the solid-liquid mass ratio (s:l) is 0.5:100-2.5:100; optionally repeating the extraction operation of step (8) to obtain a high-purity sodium chloride solution from which V / W heavy metals are removed; wherein the reaction time is 0.5h-2.5h and the reaction temperature is room temperature;

[0089] (11) The sodium hydroxide solution obtained by electrolysis and Cl2 are introduced into the high-purity sodium chloride solution from which V / W heavy metals have been removed, and the mixture is fully mixed and reacted to oxidatively degrade COD while adjusting the pH of the system to neutral. Then, chemical salts are added until the concentration of the high-purity sodium chloride solution is 300-350 g / L, thereby obtaining a refined sodium chloride solution which is recycled to the chlor-alkali electrolysis process of step (1).

[0090] <Source of raw materials>

[0091] In each embodiment and comparative example, the waste catalyst used is a denitration catalyst deactivated in a power plant of the State Energy Group;

[0092] Based on the total weight of the waste catalyst, the active components and their main physical and chemical properties are shown in Table 1 below:

[0093] Table 1

[0094]

[0095] The magnesium sulfate heptahydrate, N235, TBP, sec-octanol, sulfonated kerosene and NaH2PO4 used are all conventional raw materials and are commercially available.

[0096] Embodiment 1:

[0097] Chlor-alkali electrolysis without waste recycling - coupled integrated process for waste catalyst recovery, see Figure 1 As shown, the following steps are included:

[0098] (1) Electrolysis of purified NaCl solution: The purified NaCl solution with a concentration of 310 g / L obtained by catalyst recovery and purification is used as the electrolysis anode solution and fed into the ion membrane electrolyzer at a flow rate of 200 kg / h. The NaCl solution is electrolyzed by applying power until the current reaches 5.3 kA, generating Cl2 at the anode and NaOH solution and H2 at the cathode until the concentration of the NaOH solution generated at the cathode reaches 31 wt%;

[0099] (2) Acid solution preparation: H2 generated at the cathode is introduced into a synthesis furnace to react with Cl2 generated at the anode at a molar ratio of (1.15-1.1):1 to prepare HCl; the obtained HCl is then mixed with deionized water at a mass ratio of 1:5 to prepare an acid solution with a concentration of 16 wt%;

[0100] (3) preparing alkaline solution: mixing the NaOH solution prepared in step (1) with deionized water in a mass ratio of 4:1, stirring until uniform, and preparing an alkaline solution with a concentration of 25.8 wt %;

[0101] (4) Catalyst pretreatment and alkali leaching reaction: The waste catalysts shown in Table 1 after ash removal were dried at 120° C. for 3 h until the moisture content was less than 5 wt %, and then disassembled and crushed in a Raymond crusher until the particle size was 300 mesh, thereby obtaining the crushed waste catalyst powder;

[0102] Then, 500 g of the ground spent catalyst powder, 750 mL of the alkali solution prepared in step (3), and 5.0 g of sodium metatitanate were poured into a reaction kettle and mixed. After stirring evenly, an alkali leaching reaction was carried out at 140° C. for 2 h, and stirring was maintained during the reaction.

[0103] (5) Oxidation and acidification reaction: After the alkaline leaching reaction, slowly introduce the electrolytic Cl2 from the bottom of the reactor and stir evenly until the pH value of the slurry in the reactor reaches 10.5, and continue stirring for 1.5 h to carry out the oxidation and acidification reaction;

[0104] The product after the reaction was cooled to room temperature, and solid-liquid separation was performed using a filter press to obtain solution-1 and solid-1; solid-1 was pulped and washed once with 500 ml of clean water to obtain solution-2 and solid i; solution-1 and solution-2 were mixed to obtain solution i;

[0105] The obtained solid i is used for the subsequent recovery of vanadium, tungsten and titanium powders, and the obtained solution i is used for the subsequent recovery of vanadium, tungsten;

[0106] (6) Acid washing: the solid i obtained in step (5) was mixed with 500 mL of the acid solution prepared in step (2) and poured into a reactor, stirred evenly, and the initial pH value of the system was measured by a pH meter to be 1.352, 200 g of a 15 wt% titanium trichloride solution was added, and then stirred at 85° C. for 1.5 h, solid-liquid separation was performed, and pulping and washing were performed for 4-7 times to separate solution ii and solid ii;

[0107] The solid ii is washed with clean water until the conductivity of the filtrate is less than 400 μs / cm, and then the washed solid ii is dried at 150° C. for 90 min, calcined at 550° C. for 4 h, and the powder index is tested to obtain a reconstructed catalyst carrier;

[0108] (7) impurity removal: the solution ii obtained in step (6) was mixed with the solution i obtained in step (5), and the pH of the system was adjusted to 10.15 with the acid solution prepared in step (2), and then 50 g of magnesium sulfate heptahydrate was added and stirred until dissolved, reacted at 80° C. for 1.5 h, and settled for 50 min before solid-liquid separation to obtain solution iii and solid iii;

[0109] The obtained solid iii is washed with clean water 2-3 times and then used as general solid waste;

[0110] (8) Extraction: The solution iii obtained in step (7) is adjusted to a pH of 3.56 by the acid solution prepared in step (2), and then centrifuged using the acidified composite extractant at an A / O ratio of 10:1 to obtain an extractant and a high-purity sodium chloride solution;

[0111] The ratio of each component in the composite extractant is N235: TBP: octanol: sulfonated kerosene = 6:5:2:27 (volume ratio), the extraction time is 2 min, and the centrifuge speed is 50 Hz;

[0112] (9) back extraction: the extract obtained in step (8) is back extracted with 10 wt% ammonia water at an A / O ratio of 1:2 to obtain a high-purity vanadium-tungsten solution and an organic phase; the organic phase is recycled, and the components of the high-purity vanadium-tungsten solution are measured and recovered;

[0113] (10) Induced polymerization-extraction: the acid solution prepared in step (2) is added to the high-purity sodium chloride solution obtained in step (8) until the pH value of the system is 2.0, and then NaH2PO4 is added (the amount of NaH2PO4 added is calculated based on the solid-liquid mass ratio so that the solid-liquid (s:l) mass ratio = 1:100), and the mixture is fully mixed and stirred at room temperature to carry out VWP induced polymerization reaction for 1.0 h; the extraction operation of step (8) is repeated to obtain a high-purity sodium chloride solution from which V / W heavy metals have been removed;

[0114] (11) Adding the sodium hydroxide solution obtained by electrolysis and Cl2 to the high-purity sodium chloride solution from which V / W heavy metals have been removed and mixing thoroughly, wherein the amount of the sodium hydroxide solution added is based on the mass of solid sodium hydroxide in the solution, the ratio of the mass of solid sodium hydroxide to the mass of the solution is 3.5:100, and the ratio of the amount of Cl2 (based on the mass of pure Cl2) added to the mass of the solution is 1.6:100, and reacting at 60°C for 0.5h, while oxidizing and degrading COD, adjusting the pH of the system to neutral; then adding 750g of conventional chemical salt to prepare the high-purity sodium chloride solution to a concentration of 310g / L, as a refined sodium chloride solution and recycling it to the chlor-alkali electrolysis process of step (1).

[0115] The recovered solid and recovered liquid produced by the coupled integrated process were tested, and the test results are shown in Tables 2 and 3.

[0116] Embodiment 2:

[0117] The coupled integrated process of chlor-alkali electrolysis and waste catalyst recovery without waste circulation is carried out with reference to Example 1, except that:

[0118] In the preparation of the alkali solution in step (3), the NaOH solution obtained in step 1) is mixed with deionized water in a mass ratio of 2:1, and stirred until uniform to prepare the alkali solution.

[0119] The recovered solid and recovered liquid produced by the coupled integrated process were tested, and the test results are shown in Tables 2 and 3.

[0120] Embodiment 3:

[0121] The coupled integrated process of chlor-alkali electrolysis and waste catalyst recovery without waste circulation is carried out with reference to Example 1, except that:

[0122] The reaction temperature of the alkali leaching reaction in step (4) is 145°C.

[0123] The recovered solid and recovered liquid produced by the coupled integrated process were tested, and the test results are shown in Tables 2 and 3.

[0124] Embodiment 4:

[0125] The coupled integrated process of chlor-alkali electrolysis and waste catalyst recovery without waste circulation is carried out with reference to Example 1, except that:

[0126] In step (10), the acid solution prepared in step (2) is added to the high-purity sodium chloride solution obtained in step (8) until the pH value of the system is 1.95, and then Na3PO4 is added (the amount of Na3PO4 added is calculated by solid-liquid mass ratio, solid-liquid (s:l) mass ratio = 1.0:100), and the mixture is fully mixed and stirred at room temperature for 1 hour to carry out VWP induced polymerization reaction; and the extraction operation of step (8) is repeated to obtain a high-purity sodium chloride solution from which V / W heavy metals are removed.

[0127] The recovered solid and recovered liquid produced by the coupled integrated process were tested, and the test results are shown in Tables 2 and 3.

[0128] Comparative Example 1:

[0129] The process for recycling the spent catalyst is similar to that of Example 1, except that: the electrolysis of the refined NaCl solution in step (1) is not performed, the required alkali solution and acid solution are prepared by additional commercially available caustic soda flakes and additional commercially available hydrochloric acid; and the required Cl2 is also added additionally to the system.

[0130] The obtained recovered solid and recovered liquid were tested, and the test results are shown in Table 2 and Table 4.

[0131] Comparative Example 2:

[0132] The process for recovering the spent catalyst is similar to that of Example 1, except that commercially available sodium chloride solution and deionized water are used to prepare the anolyte required for the chlor-alkali electrolysis process.

[0133] The obtained recovered solid and recovered liquid were tested, and the test results are shown in Table 2 and Table 4.

[0134] Comparative Example 3:

[0135] The coupled integrated process of chlor-alkali electrolysis and waste catalyst recovery without waste circulation is carried out with reference to Example 1, except that the induced polymerization-extraction process of steps (8) to (10) is not provided.

[0136] The obtained recovered solid and recovered liquid were tested, and the test results are shown in Table 2 and Table 4.

[0137] Comparative Example 4:

[0138] The coupled integrated process of chlor-alkali electrolysis and waste catalyst recovery without waste circulation is carried out with reference to Example 1, except that the oxidation removal of COD in step (11) is not provided.

[0139] The obtained recovered solid and recovered liquid were tested, and the test results are shown in Table 2 and Table 4.

[0140] Index test of recovered solids (eg, reconstructed catalyst supports): The composition after cleaning is tested by XRF, in units of (wt %).

[0141] Table 2 Test results of the content of the main active components contained in the recovered catalyst carrier

[0142] sample <![CDATA[V2O5]]> <![CDATA[WO3]]> <![CDATA[TiO2]]> <![CDATA[Fe2O3]]> <![CDATA[SiO2]]> <![CDATA[Na2O]]> <![CDATA[SO3]]> CaO Example 1 0.1126 2.0768 92.1064 0.0087 1.9817 0.0114 3.4208 0.0367 Example 2 0.1073 2.0687 92.1106 0.0093 2.0187 0.0235 3.242 0.0826 Example 3 0.2023 2.3517 91.5563 0.0101 2.1214 0.0302 3.4257 0.0453 Example 4 0.1920 2.1351 91.4663 0.0091 2.2124 0.0233 3.2437 0.0324 Comparative Example 1 0.4503 3.422 90.9818 0.3344 3.1989 0.011 0.6212 0.0083 Comparative Example 2 0.4373 3.1218 91.286 0.3364 3.3513 0.0149 0.5431 0.0008 Comparative Example 3 0.3191 3.2121 91.2433 0.0091 2.3222 0.0122 2.7242 0.0112 Comparative Example 4 0.1012 2.1103 92.0110 0.0087 1.9353 0.0223 3.4313 0.0323

[0143] Note: In Table 2, the content of each component is expressed in percentage (wt%) based on the total mass of the recovered carrier; in addition to the main active components and their percentages shown in Table 2, the remainder is other impurities.

[0144] Index test of recovered liquid (e.g., refined sodium chloride solution): Test the composition and COD of sodium chloride by ICP and colorimetry.

[0145] Table 3 Index test results of each embodiment of refined sodium chloride solution

[0146]

[0147] Table 4 Index test results of refined sodium chloride solution in each comparative example

[0148]

[0149] By comparing the embodiments and comparative examples 1-2, it can be seen that compared with the process of directly using commercial caustic soda / acid catalyst recovery or directly using commercial sodium chloride electrolysis to obtain acid / alkali solution, the test indicators of the recovery carrier and the refined sodium chloride alkali solution prepared by the coupling process of the present invention are not much different, indicating that the coupling process of the present invention can eliminate the high-energy-consuming links such as concentration, evaporation and drying in the two fields of chlor-alkali-waste industrial catalyst recovery, while also being able to obtain a recovery carrier and a refined sodium chloride alkali solution with equivalent indicators, and can achieve waste-free circulation while being able to obtain recovered solids and recovered liquids that meet the use requirements, thereby improving direct economic benefits.

[0150] By comparing the embodiments and comparative example 3, it can be seen that the W / V of heavy metals in the refined sodium chloride solution obtained by the method of the present invention reaches the ppb level due to the induced polymerization extraction step, while the W concentration in the refined sodium chloride solution obtained by the conventional extraction step in comparative example 3 exceeds 40 ppm and the V concentration exceeds 2 ppm, which exceeds the standard for heavy metals in the electrolysis process, indicating that the induced polymerization extraction step is a key step for the method of the present invention to obtain the desired technical effect.

[0151] By comparing the embodiments and comparative example 4, it can be seen that in the method of the present invention, due to the synergistic oxidation effect of chlorine and sodium hydroxide, the COD content is reduced from 93ppm in comparative example 4 to 9-17ppm, reaching the indicator of COD below 40ppm required for chlor-alkali electrolysis, indicating that the step of oxidative degradation to remove COD is one of the key steps for the method of the present invention to obtain the desired technical effect.

[0152] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the spirit of the present invention.

Claims

1. A coupled integrated process for chlor-alkali electrolysis and waste catalyst recovery without waste circulation, characterized in that: The following steps are involved: (1) Chlor-alkali electrolysis: The purified NaCl solution obtained by catalyst recovery and purification is circulated back to the chlor-alkali electrolysis cell and subjected to chlor-alkali electrolysis to prepare Cl2, HCl and NaOH solutions; (2) Acid solution preparation: Cl2 and H2 obtained by electrolysis are introduced into a synthesis furnace for reaction to prepare HCl; the obtained HCl is then mixed with deionized water to prepare an acid solution; the concentration of the acid solution is preferably 5wt%-20wt%; (3) Preparation of alkali solution: adding deionized water to the NaOH solution obtained by electrolysis to prepare alkali solution; the concentration of the alkali solution is preferably 10wt%-30wt%; (4) Alkali leaching reaction: crushing the waste catalyst to be recycled to a particle size of 200-300 mesh to obtain a crushed waste catalyst powder; the waste catalyst is a waste environmentally friendly catalyst containing vanadium-tungsten-molybdenum-titanium; Then, the waste catalyst powder is evenly mixed with the prepared alkali solution and the inducer, and then an alkali leaching reaction is performed; (5) Oxidation and acidification reaction: After the alkaline leaching reaction in step (4), the Cl2 prepared in step (1) is introduced into the reaction kettle while stirring, so that the gas and the solid and liquid are fully contacted and mixed until the pH value is reduced to 9-10, and further stirred to carry out oxidation and acidification reaction, and the stirring time is 1.0-1.5h; The product after the reaction is subjected to solid-liquid separation, and is slurried and washed until the pH value of the solution is 13-14, and a solution i and a solid i are separated; (6) acid washing: mixing the solid i obtained in step (5) with the acid solution prepared in step (2) until the initial pH is 1-4, performing an acid washing reaction and then performing solid-liquid separation to obtain a solution ii and a solid ii; (7) removing impurities: mixing the obtained solution i and solution ii, adding the acid solution prepared in step (2) until the pH of the mixed solution is 10-10.5, then adding a precipitant, stirring until dissolved, and reacting; after the reaction is completed, sedimentation and solid-liquid separation are performed to separate solution iii and solid iii; (8) adding the acid solution to the obtained solution iii to adjust the pH of the system to 2.5-4.5, and then adding the acidified composite extractant for extraction to obtain an extractant and a high-purity NaCl solution; (9) adding aqueous ammonia to the extract obtained in step (8) for stripping to obtain a high-purity vanadium-tungsten solution and an organic phase; optionally, recycling the organic phase; (10) adding the prepared acid solution to the high-purity NaCl solution obtained in step (8) until the pH of the system is 1.5-3, then adding a P-type inducer and stirring to carry out a VWP induced polymerization reaction; and then repeating the extraction operation of step (8) to obtain a high-purity sodium chloride solution from which V / W heavy metals have been removed; wherein the reaction time is 0.5h-2.5h, and the reaction temperature is room temperature; (11) The sodium hydroxide solution obtained by electrolysis and Cl2 are introduced into the high-purity sodium chloride solution from which V / W heavy metals have been removed, and the mixture is fully mixed and reacted to oxidatively degrade COD while adjusting the pH of the system to neutral. Then, chemical salts are added until the concentration of the high-purity sodium chloride solution is 300-350 g / L, thereby obtaining a refined sodium chloride solution which is recycled to the chlor-alkali electrolysis process of step (1).

2. The coupling integration process according to claim 1, characterized in that: In step (1), the concentration of the refined NaCl solution circulated back to the chlor-alkali electrolytic cell is 300-350 g / L; The current of the chlor-alkali electrolysis is 4-6 kA; The concentration of the NaOH solution is 31-40 wt %.

3. The coupling integration process according to claim 1, characterized in that: In step (4), the waste catalyst is selected from one or more of a waste denitration catalyst, a waste hydrogenation reduction catalyst, a waste oil product catalyst and a waste hydrogenation reforming catalyst.

4. The coupling integration process according to claim 1, characterized in that: In step (4), the inducer is sodium titanate and / or sodium phosphate; the amount of the inducer added is 0.1%-1% of the mass of the waste catalyst powder; the liquid-to-solid ratio (l:s) of the alkali solution to the waste catalyst is 1:1-3:1 mL / g; In step (4), the process conditions of the alkali leaching reaction include: reaction temperature of 100-240° C., reaction time of 30-120 min.

5. The coupling integration process according to claim 1, characterized in that: In step (6), the concentration of the acid solution is 5wt%-20wt%, and the liquid-to-solid ratio (l:s) of the acid solution to the solid is 1:1-3:1mL / g; The process conditions of the pickling reaction include: reaction temperature of 70°C-90°C, reaction time of 45-90min; After solid-liquid separation, pulping and washing are optionally performed, and the number of pulping and washing times is 4-7 times.

6. The coupling integration process according to claim 1, characterized in that: In step (7), the amount of magnesium sulfate heptahydrate added is 5wt%-20wt% of the initial waste catalyst powder mass; The process conditions of the reaction include: reaction temperature of 65-95°C, reaction time of 60-180min; and sedimentation time of 30-120min.

7. The coupling integration process according to claim 1, characterized in that: In step (8), the composite extractant is a mixture of a main extractant + a co-extractant + a phase regulator + a diluent; wherein the volume ratio of the main extractant: the co-extractant: the phase regulator: the diluent is (4-6): (2-5): (1-3): (25-30); Preferably, the main extractant is one or more of a primary amine, a secondary amine, a tertiary amine and a quaternary ammonium salt; Preferably, the synergistic extractant is a lipid; Preferably, the phase regulator is a higher alcohol; Preferably, the diluent is sulphonated kerosene.

8. The coupling integration process according to claim 1, characterized in that: In step (8), the extraction process conditions include: the extraction A / O is 5:1-12:1; the extraction time is 1-5min; The extraction is centrifugal extraction, and the speed of the centrifuge is 46-50 Hz.

9. The coupling integration process according to claim 1, characterized in that: In step (9), the concentration of the aqueous ammonia is 7.5wt%-15wt%; The A / O ratio of the stripping is 1:1-1:

3.

10. The coupling integration process according to claim 1, characterized in that: In step (10), the P-type inducing agent is selected from one or more of Na3PO4, Na2HPO4 and NaH2PO4; The amount of the P-type inducer added is calculated based on the solid-liquid mass ratio, and the solid-liquid mass ratio (s:l) is 0.5:100-2.5:100.

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