A method for treating waste hydrochloric acid containing iron and zinc

Abstract

The present invention relates to the technical field of industrial wastewater treatment, and discloses a method for treating waste hydrochloric acid containing iron and zinc, comprising the following steps: step 1, reducing the organic content of waste hydrochloric acid containing zinc and iron by absorption on activated carbon to obtain a low COD feed liquid; step 2, mixing the low COD feed liquid with an extractant for multi-stage extraction and separation to obtain an organic phase and a waste hydrochloric acid solution containing iron; the organic phase is stripped with water to obtain a zinc chloride solution; step 3, catalytically oxidizing and adjusting the basicity of the waste hydrochloric acid solution containing iron in sequence to obtain a water treatment agent; step 4, the zinc chloride solution is used to produce a zinc chloride product. This scheme can quickly prepare a qualified ferric chloride or polyferric chloride water treatment agent product by sequentially subjecting the waste hydrochloric acid containing zinc and iron to activated carbon pretreatment, extraction and separation, catalytic oxidation, and basicity adjustment, effectively simplifying the treatment process, improving production efficiency, and quickly realizing the resource utilization of waste hydrochloric acid containing zinc and iron.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and in particular to a method for treating waste hydrochloric acid containing iron and zinc. Background Art

[0002] Waste hydrochloric acid containing zinc and iron mainly comes from galvanizing plants. Before galvanizing or spraying, the rust and oxide film on the surface of steel need to be pickled, and unqualified galvanized steel needs to use hydrochloric acid to backwash the zinc layer on the surface for zinc removal. When the hydrochloric acid content of the two is reduced to a certain concentration, it cannot be used anymore and becomes waste liquid. This type of waste liquid generally contains high-concentration hydrochloric acid, ferrous chloride and zinc chloride, so it has good recycling value. Due to the difficulty of the zinc and iron separation process, the resource recycling of waste hydrochloric acid containing zinc and iron is seriously restricted. In addition, with the increasing scarcity of global mineral resources, it is extremely important to realize the resource utilization of waste hydrochloric acid containing zinc and iron.

[0003] At present, there are four main methods for treating waste hydrochloric acid containing zinc and iron: 1. Neutralization precipitation method: by adding an appropriate amount of neutralizer (caustic soda, lime, etc.) to the pickling waste liquid, the pH value is adjusted by acid-base neutralization reaction, and the metal ions in the pickling waste liquid are precipitated in the form of hydroxides. The precipitate is separated by solid-liquid separation of the filter press equipment to achieve the treatment effect; 2. Resin adsorption method: the resin adsorbs zinc chloride to separate zinc chloride from the hydrochloric acid system; 3. Extraction oxidation method: add an oxidant to the solution to oxidize ferrous chloride into ferric chloride or polyferric chloride solution, and then use an extractant to extract and remove zinc. In particular, the extraction oxidation method is widely used due to its high selectivity, simple operation and high cost performance. For example, the prior art CN105696010A discloses a method for recycling waste hydrochloric acid solution containing iron and zinc, which specifically comprises the following steps: (1) consuming acid and reducing to make the acidity meet the requirements, and reducing the trivalent iron in the waste acid to ferrous iron; (2) extracting and separating zinc and iron to obtain a ferrous chloride solution; (3) extracting the organic phase to transfer zinc to a stripping solution through stripping, and extracting and recycling the organic phase; (4) treating the stripping solution with alkali in stages to obtain zinc hydroxide, and recycling the stripping solution: adding an appropriate amount of hydrogen peroxide to the stripping solution obtained after oil separation to oxidize the ferrous iron to trivalent iron, adding sodium hydroxide, adjusting the pH value to 3.2-5.0, precipitating the iron in the form of ferric hydroxide, filtering, and obtaining a mixed residue of ferric hydroxide and zinc hydroxide and a filtrate containing zinc; the mixed residue is dissolved with hydrochloric acid and returned to the feed solution; adding sodium hydroxide to the zinc-containing filtrate to adjust the pH value to 7.0-8.0, precipitating the zinc in the form of zinc hydroxide, and filtering to obtain zinc hydroxide and a filtrate. The method of the present invention utilizes the difference in the extraction ability of trioctylamine N235 on ferrous iron and zinc to separate iron and zinc, thereby obtaining relatively pure ferrous chloride liquid and zinc hydroxide solid. Among them, ferrous chloride can be oxidized to ferric chloride, and both ferrous chloride and ferric chloride can be used as water treatment agents; zinc hydroxide can be used as a raw material for preparing zinc oxide or zinc chloride.

[0004] However, the prior art still has the following technical problems: (1) The prior art consumes acid and reduction before separation, and still needs to be oxidized and then alkali is added for precipitation after extraction and separation, which results in a complex process and low production efficiency. In addition, repeated reduction and oxidation result in waste of reagents and are uneconomical. (2) The iron and zinc in the waste hydrochloric acid in the prior art are precipitated with sodium hydroxide, which produces a large amount of waste liquid that needs to be treated before discharge, resulting in low environmental benefits.

[0005] In view of this, the development of an efficient, low-waste liquid treatment method for iron-zinc-containing waste hydrochloric acid not only effectively makes up for the shortcomings of the existing technology, but also can quickly separate iron and zinc in the waste hydrochloric acid, which is of great significance to the resource utilization of iron-zinc-containing waste hydrochloric acid. Summary of the invention

[0006] The present invention aims to provide a method for treating waste hydrochloric acid containing iron and zinc, and solves the technical problem that the process is complicated and the production efficiency is reduced when treating waste hydrochloric acid containing iron and zinc with the prior art.

[0007] To achieve the above object, the present invention adopts the following technical scheme: a method for treating waste hydrochloric acid containing iron and zinc, comprising the following steps:

[0008] Step 1: Material pretreatment: waste hydrochloric acid containing zinc and iron is absorbed by activated carbon to reduce the organic content and obtain a low COD feed liquid;

[0009] Step 2, extraction and separation: the low COD feed liquid and the extractant are subjected to multi-stage extraction and separation at a volume ratio of 1:5-6 to obtain an organic phase and an aqueous phase, wherein the aqueous phase is an iron-containing waste hydrochloric acid solution; a stripping agent is added to the organic phase for stripping to obtain a recovered extractant and a zinc chloride solution;

[0010] Step 3, recovering iron: subjecting the iron-containing waste hydrochloric acid solution obtained in step 2 to catalytic oxidation and salt base adjustment in sequence to obtain a ferric chloride water treatment agent or a polyferric chloride water treatment agent;

[0011] Step 4: Recover zinc: The zinc chloride solution is used to produce zinc chloride products.

[0012] The principles and advantages of this solution are:

[0013] 1. Compared with the existing technology with complex process and reduced production efficiency, this solution can quickly prepare qualified ferric chloride or polyferric chloride water treatment agent products by subjecting zinc- and iron-containing waste hydrochloric acid to activated carbon pretreatment, extraction separation, catalytic oxidation, and salt base adjustment in sequence, effectively simplifying the treatment process, improving production efficiency, and quickly realizing the resource utilization of zinc- and iron-containing waste hydrochloric acid.

[0014] 2. Compared with the prior art which consumes acid and reduces before extraction and separation, and still needs oxidation and alkali precipitation after extraction and separation, resulting in reagent waste, this solution only needs one catalytic oxidation after adsorption and extraction and separation to prepare qualified ferric chloride or polyferric chloride water treatment agent products, effectively reducing the amount of reagents used, reducing costs, and improving production efficiency.

[0015] 3. In this scheme, the extractant and the stripping agent can be reused after use, and no excessive waste liquid is generated in the other steps, which effectively reduces the amount of waste liquid in the recycling process of zinc-containing and iron-containing waste hydrochloric acid, improves the environmental benefits of the resource utilization of zinc-containing and iron-containing waste hydrochloric acid, and thus achieves the unity of economic and environmental benefits.

[0016] Preferably, as an improvement, in step one, a pretreatment tower loaded with multi-layer activated carbon is used to treat the zinc- and iron-containing waste hydrochloric acid to reduce the COD in the zinc- and iron-containing waste hydrochloric acid to less than 500 mg / L.

[0017] Technical effect: This scheme adopts the above-mentioned setting, which mainly adsorbs and removes surfactants in waste hydrochloric acid to prevent the surfactants from affecting the extraction and separation effect in the subsequent extraction stage.

[0018] Preferably, as an improvement, in step 2, the extractant comprises the following raw materials in parts by weight: 275 to 300 parts of diluent sulfonated kerosene 260, 40 to 60 parts of secondary octanol and 100 to 200 parts of trioctylamine N235.

[0019] Technical effect: This scheme adopts the above-mentioned method to configure the extractant, and after three repeated extractions, zinc is achieved to be less than 50 mg / L, effectively separating zinc. Among them, sulfonated kerosene 260 is used as a non-polar diluent to dilute the extraction system and reduce the viscosity of the extraction system, thereby improving the separation effect of the aqueous phase and the organic phase; and 2-octanol is used as a medium-polarity diluent to form a microemulsion between the aqueous phase and the organic phase interface to promote the mass transfer process of metal ions; and 2-octanol can also slightly complex metal ions and can help stabilize the metal-extractant complex through hydrogen bonds or other weak interactions to prevent it from decomposing in the organic phase. Trioctylamine N235 is mainly used for selective extraction and complexation of zinc ions, so that after extraction, zinc ions enter the organic phase in the form of a complex, while hydrochloric acid and iron ions remain in the aqueous phase to obtain low-zinc and iron-containing waste hydrochloric acid, thereby achieving separation of zinc and iron.

[0020] The applicant has found through long-term experiments that if the amount of the diluent sulfonated kerosene / sec-octanol is too high, the zinc and iron separation effect will be reduced due to its poor zinc extraction selectivity; if the amount of sulfonated kerosene / sec-octanol is too low, the extraction and separation effect will be reduced due to the excessively high solution concentration during extraction and the reduced stability of the zinc ion complex; if only sec-octanol is used as the diluent, the extraction and separation effect will be reduced due to the reduced stability of the zinc ion complex; if only sulfonated kerosene 260 is used as the diluent, the generation of zinc ion complex will be reduced due to the decrease in mass transfer efficiency, and the extraction and separation effect may be reduced due to insufficient stability of the complex; if the amount of trioctylamine N235 is too much, the mass transfer effect at the interface will be reduced due to the increase in the viscosity of the organic phase, and the extraction efficiency will be too high due to the significant increase in the concentration of N235 in the organic phase, which may cause metal ions that were not originally preferentially extracted (such as Fe 3+ , Fe 2+ ) is also extracted into the organic phase in large quantities, thereby causing co-extraction, thereby reducing the extraction and separation effect; if the amount of trioctylamine N235 is too small, it may cause insufficient extraction efficiency, incomplete extraction of target metal ions, decreased selectivity, reduced mass transfer efficiency, and complex instability, thereby reducing the separation effect of zinc and iron, resulting in more zinc residues in the iron-containing waste hydrochloric acid, thereby affecting the quality of the ferric chloride water treatment agent.

[0021] Preferably, as an improvement, in step 2, the stripping agent is water.

[0022] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for the back extraction of zinc ions from the organic phase and the recovery and utilization of zinc ions. Specifically, when water is used as the back extraction agent, the H+ concentration in the aqueous phase is relatively high, which can protonate the extractant and weaken its binding force with zinc ions. At the same time, the competitive complexing effect of water molecules also helps to transfer zinc ions from the organic phase to the aqueous phase. After back extraction, zinc ions (Zn2+) are redissolved in the aqueous phase to obtain a zinc chloride solution, and the extractant can be reused for front-end extraction.

[0023] Preferably, as an improvement, in step three, the catalytic oxidation uses sodium nitrite as a catalyst and oxygen as an oxidant to catalytically oxidize the ferrous ions in the solution into ferric ions.

[0024] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for catalytically oxidizing ferrous ions in the solution into ferric ions to obtain ferric chloride solution or polyferric chloride solution. The applicant has found through long-term experiments that if conventional oxidants are used for oxidation, not only a large amount of hydrochloric acid and oxidants are consumed, but also the oxidation reaction is incomplete or inefficient, which affects the finishing effect or efficiency and reduces production benefits. However, this scheme uses sodium nitrite as a catalyst and oxygen as an oxidant to oxidize ferrous ions. The cost of sodium nitrite and oxygen is low, which reduces the consumption and processing costs of chemicals. And the reaction products are mainly water and nitrogen dioxide, and no harmful by-products are produced, which reduces the burden of wastewater treatment and is environmentally friendly. In addition, the reaction conditions of this scheme are mild and the operating safety is high. It can achieve an efficient and stable oxidation process, which is suitable for large-scale industrial applications and reduces equipment corrosion and loss.

[0025] Preferably, as an improvement, the pressure of the catalytic oxidation is 0.02-0.03 MPa, the temperature is 70-75° C., and the reaction time is 3-4 h.

[0026] Technical effect: This scheme adopts the above-mentioned setting, and slight pressurization is convenient to increase the solubility of oxygen, thereby improving the contact reaction effect between oxygen and ferrous ions in the solution, and completely oxidizing the ferrous ions in the solution into ferric ions. The applicant has found through long-term experiments that if the reaction pressure is too high, the equipment requirements will increase, the oxygen solubility will be too high, and the side reactions will increase, which will increase the safety hazards. If the reaction pressure is too low, the reaction rate will decrease and the mass transfer efficiency will decrease due to insufficient oxygen solubility, thereby affecting the oxidation effect. If the reaction temperature is too high, the oxidation rate is too fast, which may cause local overoxidation, catalyst deactivation, increased equipment corrosion and safety problems. If the reaction temperature is too low, the oxidation rate will be too slow and the mass transfer efficiency will be reduced, resulting in increased energy consumption and affecting production efficiency.

[0027] Preferably, as an improvement, in step three, the basicity is adjusted to adjust the basicity of the reaction solution to 5-20.

[0028] Technical effect: This scheme adopts the above-mentioned setting to facilitate improving the stability of polyferric chloride water treatment agent or ferric chloride water treatment agent, and effectively avoids the phenomenon that the ferric chloride solution produced in the prior art can only be discharged as wastewater after treatment due to unstable performance, thereby further improving the wastewater treatment efficiency and improving the resource utilization rate of wastewater.

[0029] Preferably, as an improvement, in step three, after adjusting the salt base, evaporation concentration or dilution is also included so that the ferric chloride content in the ferric chloride water treatment agent is ≥13%, or the polyferric chloride content in the polyferric chloride water treatment agent is ≥8%.

[0030] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for preparing products that meet the standards of water treatment agents. This scheme limits the evaporation concentration or dilution operation to after catalytic oxidation, so that the ferric chloride solution or polyferric chloride solution produced by iron-containing waste hydrochloric acid with different zinc ion contents (such as high zinc, low zinc, etc.) in the factory area can be reasonably compounded, combined or concentrated according to product requirements, effectively reducing the energy consumption of evaporation concentration, thereby reducing production costs and improving production efficiency.

[0031] Preferably, as an improvement, in step 4, the zinc chloride solution obtained by back extraction is purified by iron removal, evaporated and concentrated, and dried to selectively produce five types of products in both solid and liquid states in "HG / T2323-2019 Industrial Zinc Chloride".

[0032] Technical effect: This scheme adopts the above-mentioned setting, which is convenient for resource recovery and utilization of zinc in zinc-containing and iron-containing waste hydrochloric acid, avoiding its residue in ferric chloride-related products to reduce their quality, and can also realize the recovery and utilization of zinc, thereby improving the effect and benefits of resource recycling. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The process flow chart of the method for treating waste hydrochloric acid containing iron and zinc in an embodiment of the present invention.

[0034] Figure 2 It is a front view of the catalytic oxidation device in an embodiment of the present invention.

[0035] Figure 3 It is a top view of the catalytic oxidation device in an embodiment of the present invention.

[0036] Figure 4 It is a schematic diagram of the connection structure between the ejector and the acceleration reactor of the catalytic oxidation device in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial sources.

[0038] The marks in the drawings of the specification include: circulating pump 1, feed pipe 2, cylinder 3, discharge pipe 4, ejector 5, connecting pipe 6, manhole 7, oxygen inlet hole 8, auxiliary material hole 9, ejector installation port 10, liquid material feed port 11, suction hole 12, observation mirror 13, remote thermometer 14, solid material addition port 15, bursting disc 16, pressure relief valve 17, tail gas hole 18, liquid alkali and tap water inlet hole 19, remote pressure gauge 20, graphite inlet 21, graphite outlet 22, one-way suction valve 23.

[0039] Example

[0040] This scheme provides a method for treating waste hydrochloric acid containing iron and zinc. The process flow is as follows: Figure 1 As shown, the following steps are included:

[0041] Step 1: Material pretreatment: waste hydrochloric acid containing zinc and iron is absorbed by activated carbon to reduce the organic content and obtain a low COD feed liquid;

[0042] As a reference, the characteristics of a batch of iron-zinc waste hydrochloric acid stock solution treated by this scheme are shown in Table 1:

[0043] Table 1 Composition of waste hydrochloric acid containing iron and zinc treated by this scheme

[0044] name <![CDATA[H + (mol / L)]]> Zn(mg / L) Fe(%) Cr(mg / L) COD / mg / L content 1.55 87400 7.42 45 710.4

[0045] Filter to remove suspended impurities, then waste hydrochloric acid containing zinc and iron is 3 / h flow rate through the pretreatment tower filled with multi-layer activated carbon to complete the adsorption treatment, reducing the COD in the zinc-containing and iron-containing waste hydrochloric acid to less than 500mg / L. The applicant's analysis shows that the activated carbon adsorption stage mainly removes the residual surfactant in the waste hydrochloric acid to prevent the surfactant from affecting the extraction and separation effect in the subsequent extraction stage.

[0046] Step 2, extraction and separation: the low COD feed liquid and the extractant are subjected to three-stage countercurrent extraction and separation at a volume ratio of 1:5-6 to obtain an organic phase and an aqueous phase, wherein the aqueous phase is an iron-containing waste hydrochloric acid solution (or ferrous chloride solution, with a detected zinc content of <50 mg / L); a stripping agent is added to the organic phase, and after five-stage stripping, a recovered extractant and a zinc chloride solution are obtained;

[0047] As a reference, the extractant includes the following raw materials by mass: 275-300 parts of diluent sulfonated kerosene 260, 40-60 parts of sec-octanol and 100-200 parts of trioctylamine N235. The stripping agent is water. Both can be recycled and applied to extraction and stripping after use. Specifically, the recycled extractant can be recycled to the front-end extraction; the zinc chloride solution obtained by stripping the organic phase with the stripping agent can be recycled to the stripping stage after drying and crystallization.

[0048] During the preliminary experiments, the applicant found that if the activated carbon adsorption stage is missing, the extraction process will need to add 1 to 2 more stages to achieve the zinc removal effect of the current 3-stage extraction. It can be seen that this solution can effectively shorten the extraction process by adding an adsorption stage, thereby improving production efficiency.

[0049] Step 3, recovering iron: subjecting the iron-containing waste hydrochloric acid solution obtained in step 2 to catalytic oxidation and salt base adjustment in sequence to obtain a ferric chloride water treatment agent or a polyferric chloride water treatment agent;

[0050] As a reference, catalytic oxidation uses sodium nitrite as a catalyst and oxygen as an oxidant to catalytically oxidize ferrous ions in a solution into ferric ions; the pressure of the catalytic oxidation is 0.02 to 0.03 MPa, the temperature is 70 to 75°C, and the reaction time is 3 to 4 hours.

[0051] The present solution also provides a catalytic oxidation device for waste hydrochloric acid containing iron, comprising a cylinder 3, a circulation system connected to the cylinder 3, an ejector 5 connected between the cylinder 3 and the circulation system, and a reaction accelerator connected to the lower part of the ejector 5, wherein the reaction accelerator is located in the cylinder 3. The material of the present device is preferably glass fiber reinforced plastic, which is resistant to high temperature, acid and alkali, has strong pressure bearing capacity, and can also resist fluoride ions in the raw material waste hydrochloric acid to prevent internal corrosion of the device.

[0052] like Figure 2 As shown, the circulation system includes a discharge pipe 4 connected to the bottom of the cylinder 3, a circulation pump 1 connected to the discharge pipe 4, a feed pipe 2 connected between the circulation pump 1 and the ejector 5, and an output pipe 18 connected to the feed pipe 2. Multiple circulation pumps 1 can be provided. In this embodiment, two are taken as an example, which are symmetrically arranged on both sides of the cylinder 3. Valves (not shown in the figure) are provided on the feed pipe 2 and the output pipe 18. The circulation pump 1 can extract the liquid material in the cylinder 3 and send it to the ejector 5 from the top of the cylinder 3. When it is injected into the cylinder 3 through the ejector 5, it accelerates the reaction with the reaction gas, and then returns to the cylinder 3 to replenish and accelerate the circulation of the liquid material, thereby accelerating the reaction rate.

[0053] The circulation system also includes graphite heat exchangers, such as Figure 3 As shown, a graphite inlet 21 is provided at the top of the cylinder 3. Figure 2As shown, a graphite outlet 22 is provided at the bottom of the cylinder 3, and a graphite heat exchanger is connected between the graphite inlet 21 and the graphite outlet 22 (not shown in the figure). The material is pumped into the graphite heat exchanger from the graphite outlet 22 through the graphite heat exchanger pump, and then re-enters the cylinder 3 through the graphite inlet 21, thereby cooling the material for heat exchange and temperature reduction. Specifically, the catalytic oxidation reaction in this scheme is an exothermic reaction, and the reaction can be started under normal temperature conditions. As the reaction releases heat, the temperature in the tank will gradually rise. A graphite heat exchanger and a graphite heat exchanger pump are set in the circulation system, so that the graphite heat exchanger pump can pump the waste hydrochloric acid from the graphite outlet into the graphite heat exchanger, and re-enter the tank through the graphite inlet after heat exchange, thereby realizing cooling of the waste hydrochloric acid, ensuring that the catalytic oxidation is carried out quickly while avoiding damage to the equipment by excessively high temperature. The start and stop control method of the graphite heat exchanger is as follows: when the temperature of the reaction liquid in the tank is 72-73°C, the graphite heat exchanger pump is turned on, and the reaction solution enters the graphite heat exchanger for heat exchange and cooling before returning to the tank; when the temperature drops to 68-70°C, the graphite heat exchanger pump is turned off and the heat exchange is suspended; after the temperature rises, the heat exchange is started again, and this process is repeated to control the reaction liquid temperature below 75°C, effectively avoiding high temperature damage to the equipment; the reaction liquid temperature can also be controlled to be at a rapid reaction temperature to improve the reaction efficiency.

[0054] like Figure 4 As shown, the ejector 5 is located at the top of the cylinder 3, and an ejector mounting port 10 communicating with the inside of the cylinder 3 is provided on the top of the cylinder 3, and the ejector mounting port 10 is used to fix the ejector 5, and the feed pipe 2 is connected to the ejector 5 from the top, and the mouth of the feed pipe 2 extends into the ejector 5, and a connecting pipe 6 communicating with the inner cavity of the cylinder 3 is provided on the side wall of the ejector 5, and a single-phase air intake valve is provided in the connecting pipe 6, and an accelerating reactor is connected to the bottom of the ejector 5, and the accelerating reactor includes an integrally formed straight pipe and a bent pipe, and an inverted cone pipe is fixed to the straight pipe portion, and the mouth of the inverted cone pipe is in the shape of an inverted cone; a plurality of bent pipes are provided, which are evenly distributed around the straight pipe in a circular direction with the straight pipe as a circle, and the mouth of the bent pipe is upwardly tilted. The liquid material ejected from the ejector 5 is sprayed onto the inner wall of the inverted cone tube, and the shape of the inverted cone tube can once again play a role in collecting and pressurizing the liquid material, so that the liquid material is accelerated to flow out of the ejector 5, so that the gas inside the ejector 5 is quickly rushed out and becomes a negative pressure state, so that the reaction gas in the cylinder 3 can be quickly sucked into the ejector 5 along the connecting pipe 6 to react with the liquid material, thereby accelerating the speed of the reaction gas entering the ejector 5 and improving the reaction efficiency. A bend is set under the straight pipe, so that after the liquid material flows into the straight pipe, it can flow to the pipe mouth along the arc inner wall of the bend. On the one hand, it can improve the smoothness of the liquid material flowing out of the bend, speed up the flow rate of the liquid material, and improve the efficiency; on the other hand, the pipe mouth of the bend is tilted upward, so that the liquid material has an upward trend after being ejected, so that it can have a positive contact with the reaction gas introduced from the top of the cylinder 3, thereby increasing the contact area between the liquid material and the reaction gas, and further improving the reaction rate.

[0055] like Figure 3 As shown, the top of the cylinder 3 is also provided with an auxiliary material hole 9, a liquid alkali and tap water inlet hole 19, an oxygen inlet hole 8, an air intake hole 12, a manhole 7, an observation mirror 13 arranged on the manhole 7, a one-way air intake valve 23, a remote pressure gauge 20, a bursting disc 16, a remote thermometer 14, a pressure relief valve 17, a solid material addition port 15, a liquid material feed port 11 and an exhaust hole 18 located in the middle of the top of the cylinder 3.

[0056] The oxygen inlet 8 is used to introduce the reaction gas into the cylinder 3; the liquid alkali and tap water inlet holes 19 are convenient for pumping liquid alkali and tap water from the outside, the liquid alkali is used to adjust the basicity, and the tap water is used to adjust the iron content according to demand; the one-way suction valve 23 is used to prevent negative pressure from being generated inside the cylinder 3 during discharge to prevent the glass bottle from breaking; the auxiliary material hole 9 is convenient for adding auxiliary materials such as catalysts to increase the reaction plastic, the liquid material feed port 11 is convenient for feeding the liquid material into the cylinder 3, the suction hole 12 is convenient for the reaction gas in the cylinder 3 to enter the ejector 5 and react with the liquid material, thereby accelerating the reaction rate, and the observation mirror 13 is used for the operator to observe the contents of the reactor The remote thermometer 14 is used to monitor the temperature changes in the cylinder 3; the remote pressure gauge 20 is used to monitor the pressure in the cylinder 3; the bursting disc 16 can prevent the pressure in the cylinder 3 from being out of control and burst to form a through hole for forced pressure relief; the pressure relief valve 17 is used to adjust the internal pressure of the cylinder 3 when necessary; the tail gas hole 18 is connected to the tail gas treatment device, which is used to output the tail gas obtained after the reaction in the cylinder 3 to prevent the tail gas from accumulating in the cylinder 3 and affecting the reaction rate; the setting of the manhole 7 makes it convenient for the staff to enter and exit when the cylinder 3 needs maintenance.

[0057] The method of using the catalytic oxidation device is as follows:

[0058] Take the preparation of polyferric chloride as an example: the raw material is waste hydrochloric acid produced by an iron washing plant (mainly waste hydrochloric acid containing ferrous chloride). The catalyst is sodium nitrite. The reaction gas is oxygen.

[0059] The working process is as follows:

[0060] ① After filtration, adsorption and extraction, the iron-zinc-containing waste hydrochloric acid stock solution is obtained to obtain a ferrous chloride solution with a pH value less than 1. The ferrous chloride solution is injected into the cylinder 3 through the liquid material feed port 11, and the reaction gas is introduced into the cylinder 3 from the oxygen inlet hole 8.

[0061] ② Start the circulation pump 1, pump the liquid material into the ejector 5 through the circulation pump, and then spray it into the cylinder 3 through the ejector 5. A vacuum is formed inside the ejector 5, so that the reaction gas in the cylinder 3 can be sucked into the ejector 5 through the connecting pipe 6 to react with the divalent iron in the ferrous chloride solution and oxidize it into trivalent iron.

[0062] ③ The sodium nitrite solution is injected into the cylinder 3 through the auxiliary material hole 9.

[0063] ④ Open the oxygen valve, and oxygen enters the cylinder 3 from the oxygen inlet hole 8.

[0064] ⑤ Adjust the pressure in the cylinder 3 and control the pressure at 0.02Mpa (optionally 0.02~0.03MPa).

[0065] The pressure control of this scheme is used to ensure the amount of oxygen, that is, the pressure is limited to 0.02-0.03 MPa, which can meet the required amount of oxygen. After the reaction is completed, the pressure continues to rise and no longer drops. After entering the pressure holding state for 5-10 minutes, the divalent iron content is sampled and tested. When the divalent iron content is qualified (that is, when producing polyferric chloride, the ferrous ion content is controlled to be ≤0.2%; when producing ferric chloride, the ferrous ion content is controlled to be ≤0.1%), it means that the oxidation is complete and the reaction can be stopped.

[0066] ⑥ When the temperature inside the cylinder 3 reaches 70-73°C, start the circulating cooling water system to keep the temperature inside the cylinder 3 not exceeding 75°C.

[0067] ⑦React for 3 hours (optionally 3 to 4 hours) to completely oxidize the divalent iron in the waste hydrochloric acid into trivalent iron.

[0068] ⑧Open the valve on the output pipe and the valve of the tail gas hole 18, close the valve of the feed pipe 2, so that the completely oxidized reaction solution is transferred to the product temporary storage tank through the circulation pump 1 for 24 hours of aging, and the tail gas enters the tail gas system through the tail gas hole 18 for treatment and discharge after meeting the standards. After the reaction solution is aged, it is evaporated and concentrated or formulated according to the product index to obtain the water treatment agent and then transferred to the product tank for storage.

[0069] Among them, adjusting the basicity is to adjust the basicity of the reaction solution to 5-20; after adjusting the basicity, it also includes evaporation concentration or dilution, or mixing ferrous chloride solutions of different concentrations obtained by treating different iron-containing waste hydrochloric acid, so that the ferric chloride content in the ferric chloride water treatment agent is ≥13%, or the polyferric chloride content in the polyferric chloride water treatment agent is ≥8%.

[0070] Step 4: Recovering zinc: The zinc chloride solution is used to produce zinc chloride products;

[0071] As a reference, the zinc chloride solution obtained by back extraction is purified by iron removal, evaporated, concentrated, and dried to selectively produce five types of products in both solid and liquid states in "HG / T2323-2019 Industrial Zinc Chloride".

[0072] According to empirical tests, the zinc content in the iron-zinc waste hydrochloric acid before extraction is 87300 mg / L, and the zinc content in the ferrous chloride solution obtained by extraction is 26.5 mg / L, which significantly reduces the zinc content in the iron-zinc waste hydrochloric acid (i.e., ferrous chloride solution). And for every 1 ton of iron-zinc waste hydrochloric acid treated, 0.94 ton of water treatment agent and 0.06 ton of zinc chloride solid can be obtained, effectively realizing the recycling of iron-zinc waste hydrochloric acid.

[0073] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions and / or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for treating waste hydrochloric acid containing iron and zinc, characterized in that: The steps include: Step 1: Material pretreatment: waste hydrochloric acid containing zinc and iron is absorbed by activated carbon to reduce the organic content and obtain a low COD feed liquid; Step 2, extraction and separation: the low COD feed liquid and the extractant are subjected to multi-stage extraction and separation at a volume ratio of 1:5-6 to obtain an organic phase and an aqueous phase, wherein the aqueous phase is an iron-containing waste hydrochloric acid solution; a stripping agent is added to the organic phase for stripping to obtain a recovered extractant and a zinc chloride solution; Step 3, recovering iron: subjecting the iron-containing waste hydrochloric acid solution obtained in step 2 to catalytic oxidation and salt base adjustment in sequence to obtain a ferric chloride water treatment agent or a polyferric chloride water treatment agent; Step 4: Recover zinc: The zinc chloride solution is used to produce zinc chloride products.

2. The method for treating waste hydrochloric acid containing iron and zinc according to claim 1, characterized in that: In step one, a pretreatment tower filled with multi-layer activated carbon is used to treat the zinc- and iron-containing waste hydrochloric acid to reduce the COD in the zinc- and iron-containing waste hydrochloric acid to less than 500 mg / L.

3. The method for treating waste hydrochloric acid containing iron and zinc according to claim 1, characterized in that: In step 2, the extractant comprises the following raw materials in parts by weight: 275-300 parts of diluent sulfonated kerosene 260, 40-60 parts of secondary octanol and 100-200 parts of trioctylamine N235.

4. The method for treating waste hydrochloric acid containing iron and zinc according to claim 1, characterized in that: In step 2, the stripping agent is water.

5. The method for treating waste hydrochloric acid containing iron and zinc according to claim 1, characterized in that: In step three, the catalytic oxidation uses sodium nitrite as a catalyst and oxygen as an oxidant to catalytically oxidize the ferrous ions in the solution into ferric ions.

6. The method for treating waste hydrochloric acid containing iron and zinc according to claim 5, characterized in that: The catalytic oxidation pressure is 0.02-0.03 MPa, the temperature is 70-75° C., and the reaction time is 3-4 hours.

7. The method for treating waste hydrochloric acid containing iron and zinc according to claim 1, characterized in that: In step 3, the basicity of the reaction solution is adjusted to 5-20.

8. The method for treating waste hydrochloric acid containing iron and zinc according to claim 1, characterized in that: In step three, after adjusting the salt base, evaporation concentration or dilution is further included to make the ferric chloride content in the ferric chloride water treatment agent ≥13%, or the polyferric chloride content in the polyferric chloride water treatment agent ≥8%.

9. The method for treating waste hydrochloric acid containing iron and zinc according to claim 1, characterized in that: In step 4, the zinc chloride solution obtained by back extraction is purified by iron removal, evaporated, concentrated, and dried to selectively produce five types of products in both solid and liquid states as specified in "HG / T2323-2019 Industrial Zinc Chloride".

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