A method for resource utilization of waste alkali and waste hydrochloric acid produced as by-products of a tetrachloroethylene heavy component incineration device

Abstract

The present invention relates to a method for resource utilization of waste alkali and waste hydrochloric acid produced as by-products of a tetrachloroethylene heavy component incineration device, comprising the following steps: (1) filtering the waste alkali and waste hydrochloric acid produced as by-products of the tetrachloroethylene heavy component incineration device respectively to obtain a waste alkali filtrate and a waste hydrochloric acid filtrate; (2) subjecting the waste hydrochloric acid obtained in step (1) to organic matter degradation treatment and filtering again; (3) neutralizing the waste alkali filtrate and the waste hydrochloric acid; (4) introducing the neutralized brine obtained in step (3) into a clarification tank, filtering the clarified supernatant to obtain a filtrate; and (5) subjecting the filtrate in step (4) to adsorption treatment and then A / O oxidation treatment to obtain a brine with a COD of less than 100 mg / L. The present invention not only solves the problem that waste hydrochloric acid containing organic matter is difficult to treat, but also solves the problem that the brine generated after acid-base neutralization is directly discharged and wastes resources, thereby reducing environmental pollution, turning waste into treasure, and reducing production costs for enterprises.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment and relates to a method and a device for resource utilization of waste alkali and waste hydrochloric acid produced as by-products of a tetrachloroethylene heavy component incineration device. Background Art

[0002] With the implementation of the sustainable development strategy, environmental protection has received more and more attention, especially for the chlor-alkali industry, where waste acid, waste alkali and other wastewater treatment, resource utilization and treatment costs have received widespread attention from all walks of life.

[0003] To address the environmental pollution caused by waste acid and alkali liquor and to recycle the useful components in wastewater, the chlor-alkali industry has developed various methods and devices for treating these waste acids and alkali liquors. These methods, such as neutralizing the waste acid and alkali, address the issue of residual waste acid and alkali, as described in Chinese patent document CN111842408A (202010578291.8). However, this treatment method fails to comprehensively consider whether the waste acid and alkali contain residual impurities such as organic matter and heavy metals, as well as treatment costs. The composition of tetrachloroethylene's heavy components is divided into two phases: solid and liquid. The solid phase includes hexachloroethane and hexachlorobenzene, while the liquid phase includes tetrachloroethylene, hexachlorobutadiene, and residual carbon tetrachloride. The main components of the waste alkali after incineration are sodium carbonate, sodium bicarbonate, and a small amount of sodium chloride; the main components of the waste hydrochloric acid after incineration are hydrogen chloride, methyl chloride, dimethyl ether, toluene, and chlorobenzene. The existing acid-base neutralization treatment method simply neutralizes the acid and base without removing the organic matter that may exist in the waste acid and waste alkali. This does not meet the national emission standards. Organic matter will cause great harm to the environment. If it is discharged without removal, it will not only pollute the environment, but also endanger human health.

[0004] Therefore, there are still many areas in the existing methods for treating waste acid and waste alkali that need further improvement. The industry urgently needs to provide an effective method for treating waste acid and waste alkali that comprehensively considers cost and other issues. Summary of the Invention

[0005] In order to solve the problem that the types and components of impurities in the by-product waste alkali and waste hydrochloric acid of the tetrachloroethylene heavy component incineration device are relatively complex and the existing methods cannot treat them thoroughly, the present invention provides a method for resource utilization of the by-product waste alkali and waste hydrochloric acid of the tetrachloroethylene heavy component incineration device. The method not only solves the problem of residual waste alkali and waste hydrochloric acid, but also recycles and utilizes the brine generated after acid-base neutralization and sends it back to the chlor-alkali workshop for use, thereby reducing the processing cost and production cost of the enterprise.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for resource utilization of waste alkali and waste hydrochloric acid produced as by-products of a tetrachloroethylene heavy component incineration device, characterized by comprising the following steps:

[0008] (1) introducing the by-product waste alkali and waste hydrochloric acid of the tetrachloroethylene heavy component incineration device into filters for filtering treatment to remove solid impurities present in the by-product waste alkali and waste hydrochloric acid, thereby obtaining waste alkali filtrate and waste hydrochloric acid filtrate respectively;

[0009] (2) subjecting the waste hydrochloric acid obtained in step (1) to organic matter degradation treatment until the COD is less than 3000 mg / L and the TOC is less than 8000 mg / L, and filtering again;

[0010] (3) neutralizing the waste alkali filtrate obtained by the treatment in step (1) and the waste hydrochloric acid obtained by the treatment in step (2) to obtain a neutralized brine;

[0011] (4) introducing the neutralized brine from step (3) into a clarification tank, and filtering the clarified supernatant to obtain a filtrate;

[0012] (5) The filtrate of step (4) is first subjected to adsorption treatment and then subjected to A / O oxidation treatment to obtain brine with a COD of less than 100 mg / L.

[0013] The main components (excluding water) of the waste alkali after incineration are sodium carbonate, sodium bicarbonate, and a small amount of sodium chloride; the sodium carbonate content is 50-60%, the sodium bicarbonate content is 35-45%, the sodium chloride content is 5-15%, and the pH is 9-11. The main components (excluding water) of the waste hydrochloric acid after incineration are hydrogen chloride 13-40%, methyl chloride 25-52%, dimethyl ether 20-47%, toluene 10-37%, and chlorobenzene 5-32%. The pH is 3-5, the COD is 20,000±1,000 mg / L, and the TOC is 53,000±2,000 mg / L.

[0014] Preferably, the degradation treatment in step (2) is an electrocatalytic oxidation treatment, the voltage of the electrocatalytic oxidation treatment is: 5-50V; the distance between the cathode plate and the anode plate is: 2-3cm; the coating material of the anode plate is a copper-based material, and the coating amount is 15-20g / m 2 The thickness of the anode plate is 2-3mm; the cathode plate is a stainless steel plate with a thickness of 2-3mm. The current density is 25-200mA / cm 2 The residence time of electrocatalytic oxidation treatment is 40 to 80 minutes.

[0015] Preferably, the copper-based material is a composite material of cuprous oxide and a support material. The copper-based material is composed of 90-98% by mass of cuprous oxide and 2-10% by mass of a support material. The support material is one or two of Pt, Pd, Mo2S, NiO, Fe2O3, ZnO, and Al2O3.

[0016] In step (2), the organic matter is degraded into some small molecular organic matter, methane chloride, methanol, etc.

[0017] Preferably, the neutralization treatment in step (3) is to introduce the waste alkali and waste hydrochloric acid after completing steps (1) and (2) into the acid pipe and the alkaline pipe respectively through an alkali-resistant pump and an acid-resistant pump; the pressure is adjusted to a low pressure state (2 to 10 Pa), and then the waste alkali and waste hydrochloric acid are flushed out through the pipe openings of the acid pipe and the alkaline pipe respectively, and an acid-base neutralization reaction is carried out in the neutralization reaction tank until the pH in the neutralization reaction tank is neutral.

[0018] Preferably, the filtration treatment in step (4) is: using a filter that is resistant to salt corrosion.

[0019] The adsorption treatment in step (5) refers to: using activated carbon for adsorption.

[0020] The A / O oxidation treatment in step (5) includes an anoxic biochemical pool in section A and an aerobic biochemical pool in section O. The anoxic biochemical pool in section A (anoxic section) has a wastewater retention time of 1 to 3 hours; the aerobic biochemical pool in section O (aerobic section) has a wastewater retention time of 6 to 8 hours.

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention degrades waste hydrochloric acid containing a large amount of organic matter before acid-base neutralization treatment, which greatly reduces the organic matter content in the waste hydrochloric acid and greatly improves the treatment efficiency of waste hydrochloric acid and waste alkali. The waste hydrochloric acid of the present invention is first filtered to remove possible solid impurities. The filtered waste hydrochloric acid is then subjected to catalytic degradation treatment to remove most of the organic matter in the waste hydrochloric acid, thereby achieving the purpose of reducing COD and TOC. Subsequently, it is neutralized with the waste alkali that has been filtered to obtain brine, and then some residual organic matter is treated to obtain brine that can be recycled and reused. Finally, dehydration and other treatments are performed to obtain a relatively concentrated brine that is sent to the chlor-alkali workshop for reuse, thereby realizing the resource utilization of by-product waste alkali and waste hydrochloric acid. Among them, the organic matter degradation removal rate of the waste hydrochloric acid after catalytic treatment exceeds 85%, COD is reduced by 85-90%, and TOC is reduced by 87-90%.

[0023] (2) After neutralization of waste acid and alkali, most companies directly discharge the brine, ignoring the reuse value of the brine. The present invention returns the qualified brine produced after neutralization of waste hydrochloric acid and waste alkali to the company's chlor-alkali workshop for recycling, thereby making resource utilization of waste hydrochloric acid and waste alkali and reducing the company's production costs.

[0024] In summary, the present invention not only solves the problem of waste hydrochloric acid containing organic matter being difficult to handle, but also enables the brine generated by waste hydrochloric acid and waste alkali to be returned to the chlor-alkali workshop for reuse, truly realizing the resource utilization of waste hydrochloric acid and waste alkali, and reducing the company's production costs. While protecting the environment and reducing pollution, it also achieves the resource utilization of waste acid and waste alkali, achieving multiple goals at one stroke. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a block flow chart of the treatment and resource utilization of waste hydrochloric acid and waste alkali. DETAILED DESCRIPTION

[0026] Below with reference to the embodiments and appended Figure 1 The present invention will be further described. In a specific embodiment of the present invention, waste alkali and waste hydrochloric acid are treated using a tetrachloroethylene heavy component incineration device. Excluding water, the waste alkali's main components are: 53% sodium carbonate, 37% sodium bicarbonate, and 10% sodium chloride; the pH is approximately 10. Excluding water, the waste hydrochloric acid's main components are: 20% hydrogen chloride, 36% methyl chloride, 25% dimethyl ether, 13% toluene, and 6% chlorobenzene; the pH is approximately 4, the COD is approximately 20,000 mg / L, and the TOC is approximately 53,000 mg / L.

[0027] Example 1

[0028] A method for resource utilization of waste alkali and waste hydrochloric acid produced as by-products of a tetrachloroethylene heavy component incineration device, comprising the following steps:

[0029] Step 1: introducing waste alkali and waste hydrochloric acid produced as by-products of the tetrachloroethylene heavy component incineration device into a filter for filtration to remove particulate matter in the wastewater and obtain a filtrate;

[0030] Step 2: introducing the waste hydrochloric acid filtrate containing organic matter into a degradation device to obtain waste hydrochloric acid with COD less than 3000 mg / L and TOC less than 8000 mg / L, and filtering it again; the degradation device is an electrocatalytic oxidation device, and the specific conditions of electrocatalytic oxidation degradation are: voltage: 20V; area of anode plate and cathode plate: 50*80mm; distance between cathode plates: 2.5cm; coating of anode plate is copper-based composite material; cathode plate is stainless steel plate.

[0031] The thickness of the anode electrode plate is 2 mm and the coating amount is 17 g / m 2The cathode electrode plate thickness is 2 mm. The current density is 45 mA / cm 2 , the residence time is 50 min, and the amount of waste hydrochloric acid is 2 L. The copper-based composite material consists of 98% cuprous oxide and 2% NiO.

[0032] The residual organic matter in the brine obtained after electrocatalytic degradation was: methane chloride 1%, methanol 3%, dimethyl ether 1%, toluene 0%, chlorobenzene 0%. The COD was 2200 mg / L and the TOC was 5300 mg / L.

[0033] Step 3: introducing the waste alkali and waste hydrochloric acid from Step 1 and Step 2 into the acid pipe and alkaline pipe respectively through an alkali-resistant pump and an acid-resistant pump; the pipe openings of the acid pipe and the alkaline pipe are arranged opposite to each other;

[0034] Step 4: Adjust the pressure of the waste alkali and waste hydrochloric acid produced as by-products of the tetrachloroethylene heavy component incineration device to a low pressure state (5 Pa), and then flush the waste alkali and waste hydrochloric acid through the pipe openings of the acid pipe and the alkaline pipe respectively, and perform an acid-base neutralization reaction in the neutralization reaction tank until the pH in the neutralization reaction tank is approximately neutral;

[0035] Step 5: introducing the neutralized brine obtained in step 4 into a clarification tank, and after clarification, filtering the supernatant in the clarification tank to obtain a filtrate;

[0036] In step six, the filtrate from step five is first subjected to adsorption treatment using activated carbon, filtered, and then subjected to A / O oxidation treatment to obtain brine with a COD of less than 100 mg / L, which is then sent back to the company's chlor-alkali workshop for recycling.

[0037] The specific conditions of A / O oxidation treatment are: Section A anoxic biochemical pool (anoxic section): wastewater retention time 2 hours; Section O aerobic biochemical pool (aerobic section): wastewater retention time 7 hours.

[0038] The final brine had only 0.4% methane chloride remaining.

[0039] Example 2

[0040] Unlike Example 1, only the type of copper-based composite material loading was changed. The copper-based composite material now consisted of 98% cuprous oxide and 2% ZnO. Residual organic matter in the resulting brine after electrocatalytic degradation included 1% methane chloride, 4% methanol, 2% dimethyl ether, 0.5% toluene, and 0.2% chlorobenzene. COD was 2700 mg / L, and TOC was 6800 mg / L. The final brine contained 0.7% methane chloride and 0.5% methanol.

[0041] Example 3

[0042] Unlike Example 1, only the electrocatalytic oxidation degradation voltage was changed to 50 V. The residual organic matter in the brine obtained after electrocatalytic degradation was: 1% methane chloride, 3% methanol, 2% dimethyl ether, 0% toluene, and 0% chlorobenzene. The COD was 2560 mg / L, and the TOC was 6400 mg / L. The final brine contained 0.5% methane chloride and 0.6% methanol.

[0043] Example 4

[0044] Different from Example 1, only the amount of electrocatalytic oxidation degradation anode coating was changed to 15 g / m 2 The residual organic matter in the brine after electrocatalytic degradation was: 2% methane chloride, 4% methanol, 1% dimethyl ether, 0.2% toluene, 0% chlorobenzene, COD of 2800 mg / L, and TOC of 7000 mg / L. The final brine contained 0.7% methane chloride and 0.7% methanol.

[0045] Example 5

[0046] Different from Example 1, the amount of electrocatalytic oxidation degradation anode coating was changed to 20 g / m 2 The residual organic matter in the brine after electrocatalytic degradation was: 1% methane chloride, 2.6% methanol, 1% dimethyl ether, 0.2% toluene, 0% chlorobenzene, COD of 2400 mg / L, and TOC of 6700 mg / L. The final brine contained 0.5% methane chloride and 0.2% methanol.

[0047] Comparative Example 1

[0048] This embodiment differs from Example 1 in that the coating material of the catalyst (positive electrode) in the degradation device in step 2 of this embodiment is an aluminum-based catalyst composed of 98% aluminum oxide and 2% nickel oxide. All other aspects are the same as in Example 1.

[0049] The residual organic matter in the brine after electrocatalytic degradation was: 2% methane chloride, 3% methanol, 3% dimethyl ether, 0.5% toluene, and 0% chlorobenzene. The COD was 4200 mg / L, and the TOC was 10,000 mg / L. The final brine contained 1.2% methane chloride and 0.8% methanol.

[0050] Comparative Example 2

[0051] The difference from Example 1 is that the neutralization reaction is performed first, followed by electrocatalytic degradation. The residual organic matter in the brine after electrocatalytic degradation is: 4% methane chloride, 7% methanol, 4% dimethyl ether, 2% toluene, and 1% chlorobenzene. The COD is 9800 mg / L, and the TOC is 25000 mg / L. The final brine contains 2% methane chloride and 1.2% methanol.

[0052] Comparative Example 3

[0053] The difference from Example 1 is that the A / O treatment is performed first and then the electrocatalytic degradation is performed.

[0054] The remaining organic matter in the brine after electrocatalytic degradation was: 2% methane chloride, 5% methanol, 3% dimethyl ether, 1% toluene, and 0.2% chlorobenzene. The COD was 5200 mg / L, and the TOC was 12000 mg / L. The final brine contained 1.4% methane chloride and 0.9% methanol.

Claims

1. A method for resource utilization of waste alkali and waste hydrochloric acid produced as by-products of a tetrachloroethylene heavy component incineration device, characterized in that: The following steps are involved: (1) The by-product waste alkali and waste hydrochloric acid of the tetrachloroethylene heavy component incineration device are introduced into filters for filtration treatment to remove solid impurities in the by-product waste alkali and waste hydrochloric acid, thereby obtaining waste alkali filtrate and waste hydrochloric acid filtrate respectively; (2) The waste hydrochloric acid after step (1) is subjected to organic matter degradation treatment until the COD is less than 3000 mg / L and the TOC is less than 8000 mg / L, and then filtered again; The degradation treatment is an electrocatalytic oxidation treatment, the voltage of the electrocatalytic oxidation treatment is: 5-50V, the distance between the cathode plate and the anode plate is 2-3cm; the coating material of the anode plate is a copper-based material; the copper-based material is composed of 90-98% by mass of cuprous oxide and 2-10% by mass of a load material, and the load material is one or two of Pt, Pd, Mo2S, NiO, Fe2O3, ZnO, and Al2O3; (3) neutralizing the waste alkali filtrate obtained by the treatment in step (1) and the waste hydrochloric acid obtained by the treatment in step (2) to obtain a neutralized brine; (4) introducing the neutralized brine from step (3) into a clarification tank, filtering the clarified supernatant to obtain a filtrate; (5) The filtrate from step (4) is first subjected to adsorption treatment and then subjected to A / O oxidation treatment to obtain brine with a COD of less than 100 mg / L.

2. The method according to claim 1, characterized in that The current density of the electrocatalytic oxidation treatment in step (2) is 25~200mA / cm 2 The residence time of electrocatalytic oxidation treatment is 40~80min.

3. The method according to claim 1, characterized in that The coating amount of the coating material in step (2) is 15~20g / m 2 .

4. The method according to claim 1, wherein The adsorption treatment in step (5) refers to: using activated carbon for adsorption.

5. The method according to claim 1, wherein The A / O oxidation treatment in step (5) includes an anoxic biochemical pool in section A and an aerobic biochemical pool in section O. The wastewater stays in the anoxic biochemical pool for 1 to 3 hours, and in the aerobic biochemical pool for 6 to 8 hours.

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