CN106746100B - Treatment method of ethylene refining waste alkali liquor - Google Patents
Treatment method of ethylene refining waste alkali liquor Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
- C02F1/048—Purification of waste water by evaporation
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/24—Treatment of water, waste water, or sewage by flotation
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/40—Devices for separating or removing fatty or oily substances or similar floating material
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C02F1/72—Treatment of water, waste water, or sewage by oxidation
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
- C02F2103/36—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 from the manufacture of organic compounds
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- C02F2303/00—Specific treatment goals
- C02F2303/16—Regeneration of sorbents, filters
Abstract
The invention discloses a treatment method of ethylene refining waste lye, which comprises the steps of (1) removing oil by air flotation, and removing oil substances carried in the waste lye; (2) performing high-temperature wet oxidation treatment, namely adding NaOH into the deoiled waste alkali liquor to perform high-temperature wet oxidation treatment; (3) sulfuric acid treatment, namely adding sulfuric acid into the waste alkali liquor to convert hydroxyl and carbonate into sulfate radicals; (4) performing activated carbon adsorption, namely performing activated carbon adsorption on the acidic waste liquid after sulfuric acid treatment; (5) adjusting the alkali concentration, adding solid NaOH into the adsorbed waste alkali liquor, and increasing the concentration of NaOH in the solution; (6) and (3) evaporation and concentration: evaporating and concentrating the waste alkali liquor, improving the concentration of NaOH in the solution, and recovering precipitated sodium sulfate to obtain a NaOH concentrated solution; (7) activated carbon regeneration: and (3) utilizing the saturated activated carbon obtained in the step (6) and generated in the alkali liquor regeneration step (4), recycling the regenerated activated carbon in the step (4), and recycling the generated waste alkali liquor in an upstream alkali washing tower. The method can efficiently remove COD and sulfides in the ethylene refining waste alkali liquor, recover high-purity sodium sulfate and realize zero emission of the ethylene refining waste alkali liquor.
Description
Technical Field
The invention belongs to the technical field of environment-friendly wastewater treatment, and particularly relates to a treatment method of ethylene refining waste alkali liquor in a chemical plant.
Background
In the ethylene refining process, the alkali washing method is generally adopted to remove CO in the cracking gas2、H2S, and the like. The alkaline washing process produces a large amount of spent lye which, in addition to the remaining sodium hydroxide, also contains Na which is formed during the alkaline washing process2S、Na2CO3And the like. On the other hand, due to condensation of heavy components in the cracked gas and polymerization of diolefins and aldehydes in the alkali washing process, a large amount of organic matters enter the waste alkali liquor, and the treatment difficulty of the waste alkali liquor is increased. The ethylene waste alkali liquid belongs to high-concentration organic wastewater, and has high COD, sulfide and salt contents and great treatment difficulty. With the scale-up of ethylene plants, the discharge amount of waste alkali liquid is increasing, and the harmless treatment and comprehensive utilization thereof have become important subjects to which researchers pay attention.
According to the water quality characteristics of the ethylene waste lye, some patents propose treatment methods. CN201010526697.8 discloses a method for recovering sodium sulfate from waste alkali liquor of an ethylene device, after neutralization treatment of wet oxidation effluent, anhydrous sodium sulfate containing entrained water is crystallized from a neutralization solution by an evaporation crystallization method, the anhydrous sodium sulfate containing entrained water is dried to obtain an anhydrous sodium sulfate product, partial evaporation mother liquor returns to a neutralization unit, the freezing mother liquor after freezing and recovering sodium sulfate decahydrate from partial evaporation mother liquor is subjected to biochemical treatment, and the recovered sodium sulfate decahydrate returns to the neutralization unit. The method reduces the salt content in the effluent of wet oxidation, avoids the impact of high-salt wastewater subjected to wet oxidation treatment on subsequent biochemical treatment, and simultaneously recovers the sodium sulfate in the ethylene waste alkali liquor. However, a large amount of energy is consumed in one step of direct evaporation crystallization, and the COD content in the evaporation mother liquor is high, so that the evaporation mother liquor needs to be further treated by a biochemical method.
CN200510122185.4 discloses a regeneration treatment process for ethylene alkaline washing waste liquid, which comprises the following operation steps: the waste alkali liquor is subjected to oil removal, causticization, desulfurization and other steps, and a load type solid flocculant, a metal oxide and other substances are added in sequence. The S is obtained as a by-product in the causticizing and desulfurizing process by sulfide conversion2－The method simplifies the treatment process of the ethylene waste alkali liquor and recovers useful substances, but the whole process does not consider the removal of COD in the ethylene waste alkali liquor, and introduces various impurities to influence the recovery quality of the waste alkali liquor.
CN201010205763.1 discloses a method for treating waste lye by high temperature wet oxidation, which uses oxygen in the air to oxidize inorganic sulfides and organic matters in the waste lye at 220-260 ℃ and under the pressure of keeping the waste lye in a liquid phase. The method is to S2-The removal rate of the wastewater reaches 100 percent, the removal rate of COD reaches 75 to 85 percent, but the COD concentration in the effluent is more than 20000mg/L, and the effluent contains a large amount of sodium salt, and the effluent can enter a biochemical system after being diluted in a large amount.
In conclusion, the existing methods for treating the waste alkali liquor have the problems of being inappropriate or inadequate, or insufficient in treatment effect, or large in investment and high in operating cost, or low in recovery quality, or needing to discharge the treated waste alkali liquor to a sewage treatment system, or generating high-salt-content wastewater, and the like.
Disclosure of Invention
The invention provides a method for treating ethylene refining waste alkali liquor, aiming at overcoming the defects of the prior ethylene refining waste alkali liquor treatment technology and aiming at the characteristics of the ethylene refining waste alkali liquor. The method can efficiently remove COD and sulfides in the ethylene refining waste alkali liquor, recover high-purity sodium sulfate and realize zero emission of the ethylene refining waste alkali liquor.
The invention relates to a method for treating ethylene refining waste alkali liquor, which comprises the following steps:
(1) removing oil by air flotation, and removing oil substances carried in the ethylene refining waste alkali liquor;
(2) high-temperature wet oxidation treatment, namely adding sodium hydroxide into the deoiled waste alkali liquor, and performing high-temperature wet oxidation treatment under an alkaline condition;
(3) sulfuric acid treatment, namely adding sulfuric acid into the waste alkali liquor after wet oxidation treatment to completely convert hydroxyl and carbonate into sulfate radicals;
(4) performing activated carbon adsorption, and performing activated carbon adsorption treatment on the acidic waste liquid after the sulfuric acid treatment;
(5) adjusting the alkali concentration, adding solid sodium hydroxide into the adsorbed waste alkali liquor, and increasing the concentration of the sodium hydroxide in the solution;
(6) and (3) evaporation and concentration: evaporating and concentrating the waste alkali liquor after the alkali concentration is adjusted, further improving the sodium hydroxide concentration in the solution, recovering the precipitated sodium sulfate, and simultaneously obtaining a sodium hydroxide concentrated solution;
(7) activated carbon regeneration: and (3) regenerating the saturated activated carbon generated in the step (4) by using the waste alkali liquor obtained in the step (6), reusing the regenerated activated carbon in the step (4), and reusing the generated waste alkali liquor in an upstream alkaline washing tower.
In the invention, the air flotation oil removal in the step (1) is to introduce air into the oily wastewater to generate bubbles in the water, so that the oil dispersed in the water is adhered to the bubbles and floats on the water surface along with the air to be removed. The oil removal efficiency is greatly improved by replacing gravity oil removal with air flotation oil removal, the oil content in the waste alkali liquor after the oil removal by air flotation is reduced to be below 20mg/L, and the requirement of a high-temperature wet oxidation process on the oil content of inlet water is met.
In the invention, sodium hydroxide solid is added into the deoiled waste alkali liquor. The addition amount of the sodium hydroxide is 3.0-4.0 wt% of the concentration of the sodium hydroxide in the waste alkali liquor subjected to high-temperature wet oxidation treatment, so that the whole wet oxidation reaction is carried out under an alkaline condition, and the removal efficiency of COD in the treatment process is effectively ensured. When high-temperature wet oxidation treatment is carried out, a certain amount of alkali is consumed while organic matters are oxidized, and a certain amount of alkali can be neutralized by generated acidic substances; if the alkali concentration is too low, the organic matter is not completely oxidized on the one hand, and the acidic substance formed on the other hand causes the solution in the reactor to become acidic, which causes corrosion of the reactor material. The appropriate alkali concentration not only enables the whole wet oxidation reaction to be carried out under the alkaline condition, but also can be effectively recycled in the subsequent steps, and no waste is caused.
In the invention, the reaction temperature of the high-temperature wet oxidation in the step (2) is controlled to be 240-320 ℃, preferably 260-280 ℃; the reaction pressure is 6.0-20.0 MPa, preferably 8.0-12.0 MPa; the reaction time is 40-90 minutes. The high-temperature wet oxidation treatment can efficiently remove the divalent sulfur ions (S) in the waste alkali liquor2-) Organic pollutants are oxidized into micromolecular organic acids, alcohols and other substances, and COD in the waste alkali liquor is greatly removed. S2-The removal rate can reach more than 99.9wt percent, and the effluent S2-The concentration is less than 1mg/L, S2-Almost total conversion to SO4 2-The divalent sulfide is oxidized completely, and the operation process can not generate malodorous gas polluting the atmosphere.
In the invention, in the step (3), 98% concentrated sulfuric acid is added into the waste alkali liquor according to the concentration of carbonate and hydroxyl in the high-temperature wet oxidation effluent, and the pH of the solution is controlled to be 2-6. The added concentrated sulfuric acid can enable sodium hydroxide and sodium carbonate in the waste alkali liquor to be completely converted into sodium sulfate, small molecular organic matters in the wet oxidation effluent are easy to dissociate under an acidic condition, a large number of organic matters exist in a form of cations, and oxygen-containing groups on the surface of the activated carbon, such as hydroxyl, carboxyl, carbonyl and the like, have a strong electrostatic adsorption effect on the organic matters, and are beneficial to improving the subsequent adsorption effect. In the process, the removal rate of carbonate ions in the solution can reach more than 99 percent, on one hand, the concentration of sodium sulfate in the solution is improved, and the high-concentration sodium sulfate has a salting-out effect on small molecular organic matters in the solution, so that the equilibrium adsorption quantity of the organic matters on the active carbon is increased, and the adsorption efficiency of the active carbon is improved; on the other hand, the sodium salt in the solution can be converted into single sodium sulfate, thereby providing favorable conditions for subsequent recovery of high-purity sodium sulfate.
In the invention, the deoiled waste alkali liquor is subjected to wet oxidation treatment and sulfuric acid acidification treatment, wherein the waste alkali liquor mainly contains sodium sulfate and micromolecular organic acid substances, and the concentration of the sodium sulfate can reach more than 20 wt%. The waste alkali liquid after acidification treatment is adsorbed by active carbon, and due to the existence of high-concentration sodium sulfate in the solution, the ionic strength is very strong, the interaction between ions and a solvent is increased, and the balance adsorption quantity of organic matters on the active carbon can be improved.
In the invention, the activated carbon used in the step (4) is wood powder activated carbon, the amount of the activated carbon added in each ton of waste alkali liquor is 5-15 kg, the mixture is stirred and mixed for 0.2-1.0 h, then the mixture is filtered by a filter press, filtrate is sent to a subsequent alkali concentration adjusting unit, the activated carbon adsorbed to a saturated state is regenerated by the waste alkali liquor obtained in the step (6), and the regenerated activated carbon is recycled.
According to the characteristics that the solubility of sodium sulfate in sodium hydroxide solutions with different concentrations is different and the solubility of the sodium sulfate is gradually reduced along with the increase of the concentration of the sodium hydroxide in the solution within a certain temperature range (less than or equal to 250 ℃), the sodium sulfate and the sodium hydroxide in the waste alkali liquor are separated and recycled. The adjustment of the alkali concentration in the step (5) and the evaporation and concentration in the step (6) are both for increasing the concentration of sodium hydroxide in the solution and recovering sodium sulfate, but the following four problems are considered: 1) fully recovering sodium sulfate; 2) the energy saving problem in the step (6); 3) after the sodium sulfate is evaporated, concentrated and separated, the sodium sulfate dissolved in the high-concentration sodium hydroxide solution can not influence the subsequent operation, can be fully recycled to an alkaline tower at the upstream and/or the regeneration of the activated carbon, and does not generate waste. Therefore, in the present invention, the concentration of sodium hydroxide in the solution after the alkali concentration is adjusted in step (5) is generally controlled to be 10wt% to 20 wt%. In step (6), the concentration of sodium hydroxide in the solution after evaporation and concentration of the waste alkali liquor is generally controlled to be 30-60 wt%. In the step (6), the temperature of the evaporation concentrated solution is controlled to be 40-120 ℃, and preferably 60-100 ℃. After the treatment in the step (6), the concentration of sodium sulfate in the solution can be reduced to 0.1-1.9 wt%, and the separated sodium sulfate is recovered. The recovery rate of the sodium sulfate in the method can reach more than 95 percent.
In the invention, the activated carbon regeneration in the step (7) is to analyze and regenerate the activated carbon which is saturated in the step (4) by using a sodium hydroxide solution, preferably, the alkali liquor which is evaporated and concentrated in the step (6) is adopted, the adsorption efficiency of the regenerated activated carbon can reach more than 95% of that of the fresh activated carbon, and the sodium hydroxide solution generated in the regeneration process is recycled to an upstream alkaline washing tower.
Compared with the prior art, the method has the following outstanding characteristics:
(1) aiming at the water quality characteristics of the ethylene refining waste alkali liquor, the invention adopts the treatment processes of air floatation oil removal, high-temperature wet oxidation, sulfuric acid acidification, activated carbon adsorption, alkali concentration adjustment, evaporation concentration and activated carbon regeneration, and finally obtains the high-purity sodium sulfate crystal. After treatment, the COD removal rate of the waste alkali liquor can reach more than 98 percent; s2-The removal rate can reach more than 99.9 percent, and S2-The oxidation is thorough, almost completely converted into sulfate radicals, and the content of sulfide is below 1 mg/L; the odor of the waste alkali liquor is completely removed, and atmospheric pollutants such as hydrogen sulfide and the like generated by directly acidifying the waste alkali liquor are avoided; meanwhile, the COD can be greatly reduced.
(2) The waste alkali liquor is treated by sulfuric acid after wet oxidation treatment, so that the concentration of sodium sulfate in the solution is improved, the efficiency of the activated carbon for adsorbing organic matters is obviously improved, and the using amount of the activated carbon is reduced. Meanwhile, carbonate in the waste alkali liquor is converted into sulfate radicals, and the sulfate radicals and sulfate radicals generated by wet oxidation treatment provide favorable conditions for subsequent recovery of high-purity and high-recovery sodium sulfate.
(3) The concentration of sodium hydroxide in the solution is improved by two steps of operation of adjusting the concentration of alkali and evaporation concentration, sodium sulfate is crystallized and separated out in large quantity, the separation of sodium sulfate and sodium hydroxide is realized, residual micromolecular organic matters in the solution after the activated carbon adsorption treatment are removed, the separation of sodium sulfate and other impurity substances is realized, the high-purity sodium sulfate can be recovered, the residual concentrated solution of sodium hydroxide can be reused for the regeneration of activated carbon, the generated regenerated solution is continuously reused for an upstream alkaline washing tower, and the zero discharge of wastewater is realized.
Drawings
FIG. 1 is a process flow diagram of the process of the present invention;
wherein: 1-air floatation oil removal, 2-high-temperature wet oxidation treatment, 3-sulfuric acid treatment, 4-activated carbon adsorption, 5-alkali concentration adjustment, 6-evaporation concentration and 7-activated carbon regeneration.
Detailed Description
The technical solution of the present invention is further illustrated by the following examples. In the present invention, wt% is a mass fraction.
Example 1
One strand of waste alkali liquor produced in the ethylene production process, wherein COD is 43000mg/L, and the concentration of sodium sulfide is 3.7wt% (S)2-: 16090 mg/L), a sodium carbonate concentration of 1.8wt% (19080 mg/L), a sodium hydroxide concentration of 2.8wt%, an oil of 320 mg/L. The treatment is carried out by adopting the method of the invention under the following conditions:
(1) air flotation oil removal: air is introduced into the ethylene waste alkali liquor to generate bubbles in the waste alkali liquor, and trace light oil carried in the waste alkali liquor adheres to the bubbles and floats on the water surface along with the air to be removed. After the air flotation oil removal treatment, the oil content in the waste alkali liquor is reduced to 17 mg/L.
(2) High-temperature wet oxidation treatment: adding solid sodium hydroxide into the waste alkali liquor after air floatation oil removal to ensure that the concentration of the sodium hydroxide in the waste alkali liquor is 3.5 wt%. Carrying out high-temperature wet oxidation treatment under an alkaline condition, wherein the reaction temperature is 270 ℃, the reaction pressure is 9.0MPa, and the reaction retention time is 60 min. After high-temperature wet oxidation treatment, the S in the effluent2-The concentration is 0.3mg/L, COD is 2980mg/L, the concentration of sodium sulfate is 71380mg/L, the concentration of sodium carbonate is 44580mg/L, and the concentration of sodium hydroxide is 1.3 wt%.
(3) Sulfuric acid treatment: and adding 98% concentrated sulfuric acid into the waste alkali liquor according to the concentration of hydroxyl and carbonate in the high-temperature wet oxidation effluent, and adjusting the pH of the solution to 4. The hydroxyl and carbonate in the solution are all converted into sulfate radical, and the concentration of sodium sulfate in the waste alkali liquor is 156480 mg/L.
(4) Activated carbon adsorption: adding wood powdery active carbon into the acidified waste alkali liquid, adding 10kg of active carbon into the waste alkali liquid every 1m, stirring and mixing for 0.5 hour, wherein the effluent COD is 595 mg/L.
(5) Adjusting the alkali concentration: adding solid sodium hydroxide (150 kg of solid sodium hydroxide is added in the waste alkali liquid every 1 m) after the waste alkali liquid is adsorbed by the activated carbon, so that the concentration of the sodium hydroxide in the solution is increased to 13 wt%.
(6) And (3) evaporation and concentration: evaporating and concentrating the waste alkali liquor to 30% of the volume of the stock solution, wherein the concentration of sodium hydroxide in the solution is 43 wt%. The temperature is controlled to be 70 ℃, the concentration of sodium sulfate in the waste alkali liquor is reduced to 0.35wt%, a large amount of crystalline sodium sulfate is separated out, and 151.5kg of sodium sulfate with the purity of 98.7 percent can be recovered from each cubic meter of waste alkali liquor. Solid-liquid separation and recovery of crystalline sodium sulfate, and high-concentration sodium hydroxide solution for regeneration of saturated activated carbon.
(7) Activated carbon regeneration: and (3) under the environment of 50 ℃, the sodium hydroxide solution generated in the step (6) is used for analyzing the activated carbon which is saturated in the step (4) in one step, the activated carbon is washed twice by fresh water, the adsorption capacity of the regenerated activated carbon can reach 95% of that of the fresh activated carbon, and the sodium hydroxide solution and the washing water generated in the regeneration process are recycled to an upstream alkaline washing tower.
Example 2
One strand of waste alkali liquor produced in the ethylene production process, wherein COD is 62000mg/L, and the concentration of sodium sulfide is 6.3wt% (S)2-: 28430 mg/L), a sodium carbonate concentration of 2.3wt% (24380 mg/L), a sodium hydroxide concentration of 2.1wt%, and an oil concentration of 480 mg/L. The treatment is carried out by adopting the method of the invention under the following conditions:
(1) air flotation oil removal: air is introduced into the ethylene waste alkali liquor to generate bubbles in the waste alkali liquor, and trace light oil carried in the waste alkali liquor adheres to the bubbles and floats on the water surface along with the air to be removed. After the air flotation oil removal treatment, the oil content in the waste alkali liquor is reduced to 20 mg/L.
(2) High-temperature wet oxidation treatment: adding solid sodium hydroxide into the waste alkali liquor after the air floatation oil removal treatment to ensure that the concentration of the sodium hydroxide in the waste alkali liquor is 3.5 wt%. Carrying out high-temperature wet oxidation treatment under an alkaline condition, wherein the reaction temperature is 270 ℃, the reaction pressure is 9.0MPa, and the reaction retention time is 60 min. After high-temperature wet oxidation treatment, the S in the effluent2-The concentration is 0.5mg/L, COD is 1180mg/L, the concentration of sodium sulfate is 126100mg/L, the concentration of sodium carbonate is 27980mg/L, and the concentration of sodium hydroxide is 1.8 wt%.
(3) Sulfuric acid treatment: and adding 98% concentrated sulfuric acid into the waste alkali liquor according to the concentration of hydroxyl and carbonate in the high-temperature wet oxidation effluent, and adjusting the pH of the solution to 2. The hydroxyl and carbonate in the solution are all converted into sulfate radical, and the concentration of sodium sulfate in the waste alkali liquor is 163580 mg/L.
(4) Activated carbon adsorption: adding wood powdery activated carbon into the acidified waste alkali residue, adding 13kg of activated carbon into the waste alkali liquid every 1m, stirring and mixing for 1.5 hours, wherein the COD of the effluent is 230 mg/L.
(5) Adjusting the alkali concentration: solid sodium hydroxide (208 kg solid sodium hydroxide added to concentrated solution every 1 m) was added to the waste lye from which the crude phenol was separated, so that the sodium hydroxide concentration in the solution increased to 18 wt%.
(6) And (3) evaporation and concentration: evaporating and concentrating the waste alkali liquor to 35% of the volume of the stock solution, wherein the concentration of sodium hydroxide in the solution is 51.4 wt%. The temperature is controlled to be 90 ℃, the concentration of sodium sulfate in the waste alkali liquor is reduced to 0.18wt%, a large amount of crystallized sodium sulfate is separated out, and 160.9kg of sodium sulfate with the purity of 98.9 percent can be recovered from each cubic meter of waste alkali liquor. Solid-liquid separation and recovery of crystalline sodium sulfate, and dilution of high-concentration sodium hydroxide solution for regeneration of saturated activated carbon.
(7) Activated carbon regeneration: and (3) under the environment of 70 ℃, the sodium hydroxide solution generated in the step (6) is used for analyzing the activated carbon which is saturated in the step (4) in a one-time manner, the activated carbon is washed twice by fresh water, the adsorption capacity of the regenerated activated carbon can reach 98% of that of the fresh activated carbon, and the sodium hydroxide solution and the washing water generated in the regeneration process can be recycled to an upstream alkaline washing tower.
Comparative example 1
The same waste lye as in example 1 was treated with the difference that the treatment with sulfuric acid to remove carbonate and adjust the pH of the solution was not carried out and the waste lye was treated with high temperature wet oxidation and then directly adsorbed with activated carbon.
Adding wood powdery active carbon into the waste alkali liquid after high-temperature wet oxidation, adding 10kg of active carbon into the waste alkali liquid every 1m, stirring and mixing for 0.5 hour, wherein the salting-out effect on small-molecular organic matters is poorer due to the fact that the concentration of sodium sulfate in the solution is lower than that of the neutralized waste alkali liquid, the COD of effluent is 920mg/L, and sodium sulfate and sodium carbonate are obtained after alkali concentration adjustment and evaporation concentration, so that high-purity sodium sulfate cannot be obtained.
Comparative example 2
The same spent lye as in example 1 was treated with the method described in CN 201010526697.8. After wet oxidation and neutralization treatment of the waste alkali liquor, anhydrous sodium sulfate containing entrained water is crystallized from the neutralized liquor by an evaporative crystallization method, and the anhydrous sodium sulfate containing entrained water is dried to obtain an anhydrous sodium sulfate product with the purity of 95.3%. COD in the evaporation mother liquor is 1730 mg/L. And returning part of the evaporation mother liquor to the neutralization unit, and carrying out biochemical treatment on the freezing mother liquor obtained after freezing the part of the evaporation mother liquor and recovering sodium sulfate decahydrate, wherein COD in the obtained freezing mother liquor is 1280 mg/L. Because a part of the evaporation mother liquor flows back to the neutralization unit, the energy consumption in the evaporation crystallization process is increased; neutralization solution directly carries out the evaporation crystallization and handles, because COD concentration is higher, makes the evaporation crystallization product purity reduce on the one hand, and on the other hand has caused COD concentration in evaporation mother liquor and the freezing mother liquor to be higher, and this part COD is mainly micromolecular organic acid material, can't get rid of through biochemical treatment.
Claims (9)
1. A method for treating ethylene refining waste lye is characterized by comprising the following steps:
(1) removing oil by air flotation, and removing oil substances carried in the ethylene refining waste alkali liquor;
(2) high-temperature wet oxidation treatment, namely adding sodium hydroxide into the deoiled waste alkali liquor, and performing high-temperature wet oxidation treatment under an alkaline condition;
(3) sulfuric acid treatment, namely adding sulfuric acid into the waste alkali liquor after wet oxidation treatment to completely convert hydroxyl and carbonate into sulfate radicals; after the deoiled waste alkali liquor is subjected to wet oxidation treatment and sulfuric acid acidification treatment, the waste alkali liquor mainly contains sodium sulfate and micromolecular organic acid substances, and the concentration of the sodium sulfate is more than 20 wt%;
(4) performing activated carbon adsorption, and performing activated carbon adsorption treatment on the acidic waste liquid after the sulfuric acid treatment;
(5) adjusting the alkali concentration, adding solid sodium hydroxide into the adsorbed waste alkali liquor, and increasing the concentration of the sodium hydroxide in the solution;
(6) and (3) evaporation and concentration: evaporating and concentrating the waste alkali liquor after the alkali concentration is adjusted, further improving the sodium hydroxide concentration in the solution, recovering the precipitated sodium sulfate, and simultaneously obtaining a sodium hydroxide concentrated solution;
(7) activated carbon regeneration: and (3) regenerating the saturated activated carbon generated in the step (4) by using the waste alkali liquor obtained in the step (6), reusing the regenerated activated carbon in the step (4), and reusing the generated waste alkali liquor in an upstream alkaline washing tower.
2. The method of claim 1, wherein: the oil content in the waste alkali liquor after the oil removal by air floatation in the step (1) is reduced to be below 20mg/L, and the requirement of a high-temperature wet oxidation process on the water inlet oil content is met.
3. The method of claim 1, wherein: adding sodium hydroxide solid into the deoiled waste alkali liquor, wherein the addition amount is 3.0-4.0 wt% of the sodium hydroxide concentration in the waste alkali liquor subjected to high-temperature wet oxidation treatment, so that the whole wet oxidation reaction is carried out under an alkaline condition.
4. The method of claim 1, wherein: in the step (2), the reaction temperature of the high-temperature wet oxidation is controlled to be 240-320 ℃, the reaction pressure is 6.0-20.0 MPa, and the reaction time is 40-90 minutes.
5. The method of claim 1, wherein: and (3) adding 98% concentrated sulfuric acid into the waste alkali liquor according to the concentration of carbonate and hydroxyl in the high-temperature wet oxidation effluent, and controlling the pH of the solution to be 2-6.
6. The method of claim 1, wherein: and (4) adding 5-15 kg of activated carbon into each ton of waste alkali liquor, stirring and mixing for 0.2-1.0 h, filtering by a filter press, and feeding the filtrate into a subsequent alkali concentration adjusting unit.
7. The method of claim 1, wherein: and (5) adjusting the concentration of the alkali to 10-20 wt% of sodium hydroxide in the solution.
8. The method of claim 1, wherein: and (6) controlling the concentration of sodium hydroxide in the solution obtained after evaporation and concentration of the waste alkali liquor to be 30-60 wt%, and controlling the temperature of the evaporation and concentration solution to be 40-120 ℃.
9. The method of claim 1, wherein: and (4) regenerating the activated carbon in the step (7) by adopting the alkali liquor evaporated and concentrated in the step (6), wherein the adsorption efficiency of the regenerated activated carbon reaches over 95 percent of that of fresh activated carbon, and the sodium hydroxide solution generated in the regeneration process is recycled to an upstream alkali washing tower.
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| CN112850944B (en) * | 2020-12-23 | 2023-05-16 | 苏州清然环保科技有限公司 | Treatment method of ethylene waste caustic sludge wastewater |
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| CN103241885A (en) * | 2013-05-15 | 2013-08-14 | 绍兴奇彩化工有限公司 | Method for treating acid waste water of disperse dye |
| CN104609622A (en) * | 2013-11-05 | 2015-05-13 | 中国石油化工股份有限公司 | Treatment method of spent lye from ethylene production |
| CN104609624A (en) * | 2013-11-05 | 2015-05-13 | 中国石油化工股份有限公司 | Oil refining waste alkali liquid treatment method |
| CN104870380A (en) * | 2012-10-26 | 2015-08-26 | 西门子能量股份有限公司 | Methods and systems for treating spent caustic and regenerating media |
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| CN104870380A (en) * | 2012-10-26 | 2015-08-26 | 西门子能量股份有限公司 | Methods and systems for treating spent caustic and regenerating media |
| CN103241885A (en) * | 2013-05-15 | 2013-08-14 | 绍兴奇彩化工有限公司 | Method for treating acid waste water of disperse dye |
| CN104609622A (en) * | 2013-11-05 | 2015-05-13 | 中国石油化工股份有限公司 | Treatment method of spent lye from ethylene production |
| CN104609624A (en) * | 2013-11-05 | 2015-05-13 | 中国石油化工股份有限公司 | Oil refining waste alkali liquid treatment method |
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