Method for treating acid waste liquid and waste gas

Abstract

The invention relates to the industrial fields of metallurgy, electronics and the like, and provides an acid waste liquid and waste gas treatment method which comprises the following steps: step 1, injecting an acid waste liquid into a reaction container, sequentially adding lime powder and light calcium carbonate to carry out neutralization reaction, adjusting the pH value to 4-6.5, precipitating a copper-containing compound, and carrying out solid-liquid separation to obtain copper slag and filtrate; 2, concentrating and crystallizing the filtrate in the step 1 to prepare calcium chloride; reacting the copper slag with sulfuric acid to generate copper sulfate; and thirdly, the acid waste gas is introduced into an incinerator and incinerated at the temperature of 800-1000 DEG C, and incineration tail gas containing SO2 is generated. The copper recovery rate in the waste liquid is greater than or equal to 98%; the waste gas sulfur recovery rate is larger than or equal to 99.99%, the sulfuric acid yield is larger than or equal to 96%, waste liquid-waste gas-product closed-loop circulation is achieved, waste liquid is utilized by the incinerator for neutralizing waste heat, and energy consumption is reduced by 30%. The catalytic oxidation unit adopts a honeycomb Pt catalyst, the pressure loss of the system is reduced by 40%, and the operation stability is improved.

Description

Technical Field

[0001] The present invention relates to industrial fields such as metallurgy and electronics, and specifically provides a method for treating acidic waste liquid and waste gas. Background Art

[0002] The efficient treatment of acidic waste liquid and waste gas has always been a difficult problem in the fields of metallurgy, chemical engineering, and electronic manufacturing.

[0003] In traditional processes, waste liquid and waste gas usually adopt separate treatment routes:

[0004] Waste liquid treatment: The mainstream methods include neutralization precipitation, electrolysis, and ion exchange. For example, in the neutralization method, lime and calcium carbonate are added step by step to precipitate copper ions and recover calcium chloride, but there are problems such as large consumption of reagents, high moisture content of filter residue (≥30%), and equipment corrosion caused by residual chloride ions; the electrolysis method has high energy consumption (≥5 kWh / m 3 ) and is difficult to treat low-concentration copper waste liquid (Cu 2+ <5%).

[0005] Waste gas treatment: The Claus process and its derivative technologies (such as Super Claus, SCOT) are the main means for treating sulfur-containing waste gas, but the sulfur recovery rate is limited by the thermodynamic equilibrium (≤99.8%), and a tail gas desulfurization device (such as alkali solution washing) needs to be equipped to control SO2 emissions, resulting in a complex process and a large amount of wastewater generation. In addition, the traditional incineration process (temperature ≤800°C) does not completely convert organic sulfur such as COS and CS2, and the SO2 concentration in the tail gas is often higher than 200 mg / m 3 , making it difficult to meet the strict standards of GB 31574-2015.

[0006] The existing technologies have the following key defects: The copper recovery rate in the waste liquid is generally ≤95%, and the purity of calcium chloride is less than 90% due to impurity entrainment; the sulfur recovery rate of the waste gas is restricted by the Claus reaction equilibrium, and the residual sulfur is discharged in the form of SO2, resulting in significant resource waste. Chlorine gas (Cl2) is easily released during the neutralization process of the waste liquid, and salt-containing wastewater (Na2SO3 / NaHSO3) is generated during the wet desulfurization of the waste gas, requiring additional treatment costs. The equipment redundancy of the step-by-step process is high (such as the waste liquid evaporator and the tail gas incinerator operate independently), and the waste heat of the waste liquid reaction is not utilized, increasing the comprehensive energy consumption by 25% - 40%. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technologies, the present invention provides a method for treating acidic waste liquid and waste gas, which solves the problems in the existing methods that the treatment of waste liquid and waste gas is separated, resource synergistic utilization cannot be achieved, and secondary pollution is easily generated. After the waste gas is incinerated, the SO2 emission concentration is difficult to stably be lower than 100 mg / m 3, an additional desulfurization device is required, which increases the cost, and the waste heat generated during the neutralization process of the waste liquid is not recovered, resulting in waste of energy consumption.

[0008] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for treating acidic waste liquid and waste gas, comprising the following steps:

[0009] Step 1: Inject the acidic waste liquid into a reaction vessel, and sequentially add lime powder and light calcium carbonate for neutralization reaction, adjust the pH to 4 - 6.5, precipitate copper compounds, and obtain copper slag and filtrate after solid-liquid separation;

[0010] Step 2: Concentrate and crystallize the filtrate in Step 1 to prepare calcium chloride; react the copper slag with sulfuric acid to generate copper sulfate;

[0011] Step 3: Pass the acidic waste gas into an incinerator and incinerate it at 800 - 1000 °C to generate incineration tail gas containing SO2;

[0012] Step 4: The incineration tail gas sequentially passes through two-stage catalytic oxidation units, using a Pt or V2O5-based catalyst to oxidize SO2 to SO3, and combines with water to condense into sulfuric acid;

[0013] Step 5: The tail gas is reheated to 120 - 150 °C and then discharged, where the SO2 concentration ≤ 100 mg / m 3 .

[0014] Preferably, the acidic waste liquid is an electronic etching waste liquid, containing 10% - 20% HCl, Cu 2+ 5% - 15%; the acidic waste gas is a smelting waste gas, containing 20% - 40% H2S, 1% - 5% COS, and the total sulfur content in the waste gas ≤ 30000 ppm.

[0015] Preferably, the addition amount of lime powder in Step 1 is 5% - 10% of the total mass of the waste liquid, and the addition amount of light calcium carbonate satisfies that the pH of the solution reaches 6.5 ± 0.2 after the reaction.

[0016] Preferably, the copper slag after solid-liquid separation in Step 1 contains basic copper carbonate and copper hydroxide, and the molar ratio of its reaction with sulfuric acid is 1:(1.2 - 1.5), the reaction temperature is 80 - 100 °C, and the reaction time is 30 - 60 minutes.

[0017] Preferably, the oxygen concentration in the incinerator in Step 3 is controlled at 2% - 5%, the incineration residence time is 1 - 3 seconds, and the temperature fluctuation range of the incinerator does not exceed ±50 °C.

[0018] 6. The treatment method for acidic waste liquid and waste gas according to claim 1, characterized in that part of the heat of the incinerator in step 3 comes from the waste heat generated by the neutralization reaction in step 1, which is recovered and utilized through a shell-and-tube heat exchanger, and the heat recovery efficiency is ≥ 85%.

[0019] Preferably, the operating temperature of the first-stage catalytic oxidation unit in step 4 is 350 - 450 °C, and the conversion rate is 95% - 97%; the operating temperature of the second-stage catalytic oxidation unit is 400 - 500 °C, and the conversion rate is 98% - 99%.

[0020] Preferably, the concentration of the condensed sulfuric acid in step 4 is 93% - 98%, and the residual SO2 concentration in the tail gas satisfies the following formula:

[0021]

[0022] where η1 is the conversion rate of the first stage, η2 is the conversion rate of the second stage, Qinitial is the initial SO2 mass flow rate (kg / h), and V 尾气 is the tail gas volume flow rate (m 3 / h).

[0023] Preferably, the catalyst of the catalytic oxidation unit in step 4 is a honeycomb Pt coating, with a specific surface area of ≥ 200 m 2 / g, a porosity of ≥ 70%, and a catalyst packing density of 0.6 - 0.8 g / cm 3 .

[0024] Preferably, the heat source for reheating the tail gas in step 5 comes from the waste heat of the incinerator waste gas, and heat exchange is achieved through a finned heat exchanger, reducing the energy consumption for tail gas heating by 40% - 50%.

[0025] The present invention provides a treatment method for acidic waste liquid and waste gas. It has the following beneficial effects:

[0026] 1. In the present invention, the copper recovery rate in the waste liquid is ≥ 98%, and the calcium chloride purity is ≥ 95%; the two-stage catalytic oxidation technology deeply converts SO2 in the waste gas into sulfuric acid, with a waste gas sulfur recovery rate of ≥ 99.99% and a sulfuric acid yield of ≥ 96%, realizing a "waste liquid - waste gas - product" closed-loop cycle.

[0027] 2. In the present invention, the incinerator utilizes the waste heat of waste liquid neutralization, reducing the energy consumption by 30%; the catalytic oxidation unit uses a honeycomb Pt catalyst, reducing the system pressure loss by 40%, improving the operation stability, reducing the comprehensive treatment cost by 25% compared with the step-by-step process, and the sulfuric acid and calcium chloride by-products can offset 50% of the operation cost, with significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flowchart of the present invention. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Please refer to the attached Figure 1 , the embodiments of the present invention provide a method for treating acidic waste liquid and waste gas, including the following steps:

[0031] Step 1: Inject the acidic waste liquid into a reaction container, and sequentially add lime powder and light calcium carbonate for neutralization reaction, adjust the pH to 4-6.5, precipitate copper-containing compounds, and obtain copper slag and filtrate after solid-liquid separation. The copper slag after solid-liquid separation contains basic copper carbonate and copper hydroxide, and the molar ratio of its reaction with sulfuric acid is 1:(1.2-1.5), the reaction temperature is 80-100 °C, and the reaction time is 30-60 minutes. Among them, the acidic waste liquid is electronic etching waste liquid, containing 10%-20% HCl, Cu 2+ 5%-15%, the addition amount of lime powder is 5%-10% of the total mass of the waste liquid, and the addition amount of light calcium carbonate satisfies that the pH of the solution after reaction reaches 6.5±0.2;

[0032] Step 2: Concentrate and crystallize the filtrate in Step 1 to prepare calcium chloride; the copper slag reacts with sulfuric acid to generate copper sulfate;

[0033] Step 3: Pass the acidic waste gas into an incinerator and incinerate it at 800-1000 °C. The oxygen concentration in the incinerator is controlled at 2%-5%, the incineration residence time is 1-3 seconds, and the temperature fluctuation range of the incinerator does not exceed ±50 °C, generating incineration tail gas containing SO2. Among them, the acidic waste gas is smelting waste gas, containing 20%-40% H2S and 1%-5% COS, and the total sulfur content in the waste gas ≤30000 ppm. In addition, part of the heat of the incinerator comes from the waste heat generated by the neutralization reaction in Step 1 and is recovered and utilized through a shell-and-tube heat exchanger, and the heat recovery efficiency ≥85%;

[0034] Step 4: The incineration tail gas passes through two-stage catalytic oxidation units in sequence. The operating temperature of the first-stage catalytic oxidation unit is 350-450 °C, and the conversion rate is 95%-97%; the operating temperature of the second-stage catalytic oxidation unit is 400-500 °C, and the conversion rate is 98%-99%. The catalyst of the catalytic oxidation unit is a honeycomb Pt coating, and its specific surface area ≥200m 2 / g, the porosity ≥70%, and the catalyst packing density is 0.6-0.8 g / cm 3, using a Pt or V2O5-based catalyst, SO2 is oxidized to SO3, combined with water and condensed into sulfuric acid. The concentration of the condensed sulfuric acid is 93% - 98%. The residual SO2 concentration in the tail gas satisfies the following formula:

[0035]

[0036] where η1 is the first-stage conversion rate, η2 is the second-stage conversion rate, Qinitial is the initial SO2 mass flow rate (kg / h), and V 尾气 is the tail gas volume flow rate (m 3 / h);

[0037] Step Five: The tail gas is reheated to 120 - 150 °C and then discharged, where the SO2 concentration ≤ 100 mg / m 3 . The heat source for reheating the tail gas comes from the waste heat of the incinerator exhaust gas, and heat exchange is achieved through a finned heat exchanger, reducing the energy consumption for tail gas heating by 40% - 50%.

[0038] The following is introduced in combination with specific embodiments:

[0039] Embodiment

[0040] I. Embodiment Conditions and Raw Materials

[0041] Acidic waste liquid: taken from the electronic etching process, composition: HCl concentration 15%, Cu 2+ concentration 12%, pH = 1.2, waste liquid treatment volume 2 m 3 / h.

[0042] Acidic waste gas: taken from copper smelting flue gas, composition: H2S concentration 35%, COS concentration 3%, CO2 content 55%, the rest is N2, waste gas flow rate 5000 m 3 / h.

[0043] Neutralizing agent: lime powder (CaO content ≥ 90%), light calcium carbonate (CaCO3 purity ≥ 98%).

[0044] Catalyst: honeycomb Pt-coated catalyst (specific surface area 220 m 2 / g, porosity 75%, packing density 0.7 g / cm 3 ).

[0045] II. Specific Implementation Steps

[0046] Step One:

[0047] S1. Inject the acidic waste liquid into the reaction kettle, add lime powder at 8% of the total mass of the waste liquid, stir for 30 minutes, and adjust the pH to 4.0;

[0048] S2. Slowly add light calcium carbonate until the pH reaches 6.5, and continue the reaction for 1 hour to form basic copper carbonate Cu2(OH)2CO3 and copper hydroxide Cu(OH)2 precipitate;

[0049] S3. Use a plate and frame filter press for solid-liquid separation to obtain copper slag (moisture content ≤ 15%) and filtrate.

[0050] Step 2:

[0051] S1. Concentrate the filtrate through a multi-effect evaporator until the CaCl2 concentration reaches 40%, and obtain calcium chloride with a purity of 96% after cooling crystallization;

[0052] S2. Mix the copper slag with ammonium sulfate at a molar ratio of 1:1.3 with a concentration of 98%, react at 90 °C for 45 minutes to form a copper sulfate solution, and obtain CuSO4·5H2O with a purity ≥ 99% after crystallization and drying.

[0053] Step 3:

[0054] S1. Pass the acidic waste gas into the incinerator, control the incineration temperature at 950 °C, the oxygen concentration at 3.5%, and the residence time at 2 seconds to generate tail gas containing SO2 (initial SO2 concentration of 12000 ppm);

[0055] S2. Recover heat from the incineration tail gas through a waste heat boiler (thermal efficiency 88%), cool it down to 380 °C and then enter the first-stage catalytic oxidation unit;

[0056] S3. The operating temperature of the first-stage catalytic oxidation unit is 400 °C, using a Pt catalyst, with a SO2 conversion rate of 96%, and the generated SO3 combines with water to condense into sulfuric acid with a concentration of 95%;

[0057] S4. The remaining tail gas enters the second-stage catalytic oxidation unit, with an operating temperature of 480 °C and a SO2 conversion rate of 98.5%. The SO2 concentration in the final tail gas is calculated as follows:

[0058]

[0059] S5. The tail gas is reheated to 135 °C using the waste heat of incineration through a finned tube heat exchanger and then discharged.

[0060] Comparative experiment

[0061]

[0062]

[0063] Waste liquid treatment: Cu 2+ Recovery rate 98.5%, Cu in the filtrate 2+ Residual concentration 0.08 ppm; Calcium chloride production 1.2 t / h, purity 96%.

[0064] Waste gas treatment: The total sulfur recovery rate is 99.99%, the sulfuric acid output is 3.8 t / h, and the concentration is 95%; the tail gas SO2 emission concentration is 72 mg / m 3 , meeting the GB 31574-2015 standard.

[0065] Energy consumption: Due to the utilization of the waste liquid neutralization waste heat, the fuel consumption of the incinerator is reduced by 32%; the energy consumption of the tail gas reheating is reduced by 45%.

[0066] Implementation results: Through the collaborative treatment of waste liquid - waste gas, cascaded utilization of waste heat, and two-stage catalytic oxidation, the efficient recovery of copper and sulfur resources and ultra-low emissions are achieved, the comprehensive cost is reduced by 28%, and it has significant industrial application value.

[0067] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for treating acidic waste liquid and waste gas, characterized in that, It includes the following steps: Step 1: Inject the acidic waste liquid into a reaction vessel, sequentially add lime powder and light calcium carbonate for neutralization reaction, adjust the pH to 4 - 6.5, precipitate copper-containing compounds, and obtain copper slag and filtrate after solid-liquid separation; Step 2: Concentrate and crystallize the filtrate in Step 1 to prepare calcium chloride; react the copper slag with sulfuric acid to generate copper sulfate; Step 3: Pass the acidic waste gas into an incinerator and incinerate it at 800 - 1000 °C to generate incineration tail gas containing SO2; Step 4: The incineration tail gas passes through two-stage catalytic oxidation units in sequence, using a Pt or V2O5-based catalyst to oxidize SO2 to SO3, and combine with water to condense into sulfuric acid; Step 5: The tail gas is reheated to 120 - 150 °C and then discharged, with the SO2 concentration ≤ 100 mg / m 3 .

2. The treatment method for acidic waste liquid and waste gas according to claim 1, wherein The acidic waste liquid is an electronic etching waste liquid, containing 10% - 20% HCl and 2+ 5% - 15% Cu; the acidic waste gas is a smelting waste gas, containing 20% - 40% H2S and 1% - 5% COS, and the total sulfur content in the waste gas ≤ 30000 ppm.

3. The treatment method for acidic waste liquid and waste gas according to claim 1, characterized in that, In Step 1, the addition amount of lime powder is 5% - 10% of the total mass of the waste liquid, and the addition amount of light calcium carbonate is such that the pH of the solution after reaction reaches 6.5 ± 0.

2.

4. A method for treating acidic waste liquid and waste gas according to claim 1, characterized in that, The copper slag after solid-liquid separation in Step 1 contains basic copper carbonate and copper hydroxide, and the molar ratio of its reaction with sulfuric acid is 1:(1.2 - 1.5), the reaction temperature is 80 - 100 °C, and the reaction time is 30 - 60 minutes.

5. A method for treating acidic waste liquid and waste gas according to claim 1, characterized in that, In Step 3, the oxygen concentration in the incinerator is controlled at 2% - 5%, the incineration residence time is 1 - 3 seconds, and the temperature fluctuation range of the incinerator does not exceed ±50 °C.

6. The treatment method for acidic waste liquid and waste gas according to claim 1, characterized in that, Part of the heat source of the incinerator in Step 3 comes from the waste heat generated by the neutralization reaction in Step 1, which is recovered and utilized through a shell-and-tube heat exchanger, and the heat recovery efficiency ≥ 85%.

7. A method for treating acidic waste liquid and waste gas according to claim 1, characterized in that, In Step 4, the operating temperature of the first-stage catalytic oxidation unit is 350 - 450 °C, and the conversion rate is 95% - 97%; the operating temperature of the second-stage catalytic oxidation unit is 400 - 500 °C, and the conversion rate is 98% - 99%.

8. A method for treating acidic waste liquid and waste gas according to claim 1, characterized in that, The concentration of the condensed sulfuric acid in Step 4 is 93% - 98%, and the residual SO2 concentration in the tail gas satisfies the following formula: Among them, η1 is the conversion rate of the first stage, η2 is the conversion rate of the second stage, and Q 初始 is the initial SO2 mass flow rate (kg / h), and V 尾气 is the tail gas volume flow rate (m 3 / h).

9. A method for treating acidic waste liquid and waste gas according to claim 1, characterized in that, In step 4, the catalyst of the catalytic oxidation unit is a honeycomb Pt coating with a specific surface area ≥ 200 m 2 / g and a porosity ≥ 70%. The catalyst packing density is 0.6 - 0.8 g / cm 3 .

10. A method for treating acidic waste liquid and waste gas according to claim 1, characterized in that, In Step 5, the heat source for reheating the tail gas comes from the waste heat of the incinerator exhaust gas, and heat exchange is achieved through a finned heat exchanger, reducing the energy consumption for tail gas heating by 40% - 50%.

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