A method for treating a high-salinity mother liquor
By treating the high-salt mother liquor with alkali neutralization, evaporation, and freeze crystallization, the problem of treating high-concentration chloride ion-containing saline wastewater has been solved, achieving efficient recovery of materials such as sodium chloride, and realizing zero discharge and resource recycling.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-24
- Publication Date
- 2026-06-26
AI Technical Summary
Existing technologies are unable to effectively treat the high-salt crystallization mother liquor during the preparation of 4,6-diaminoresorcinol hydrochloride, resulting in the inability to achieve zero discharge of "three wastes" and the failure to recover valuable components such as sodium chloride.
After neutralization with alkali, the solution is evaporated in a triple-effect evaporator, followed by freeze crystallization to separate sodium chloride and organic sodium salts. Finally, the residual mother liquor is recycled back to the triple-effect evaporator to achieve the recovery and recycling of solid salts.
It achieves complete treatment of high-salt mother liquor, recovers usable materials such as sodium chloride, reduces production costs, meets energy-saving and environmentally friendly production requirements, and achieves zero discharge of "three wastes".
Smart Images
Figure CN122277006A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of organic wastewater treatment technology, and specifically relates to a method for treating high-salt mother liquor. Background Technology
[0002] PBO fiber (poly(p-phenylenebenzodioxazole)) is known as the "king of fibers" due to its excellent properties. PBO fiber is prepared by the polymerization reaction of terephthalic acid and 4,6-diaminoresorcinol (DAR) hydrochloride. Because it is a polymerization reaction, the purity of the monomers is crucial. The presence of impurities can terminate the polymerization reaction, reducing the degree of polymerization and degrading the performance of the polymer material. Therefore, monomer purity plays a vital role in the preparation of high-performance PBO fibers.
[0003] Currently, the main methods for preparing DAR hydrochloride, based on the raw materials, are the 1,2,3-trichlorobenzene method and the resorcinol method. The former, which involves nitration, hydrolysis, hydrogenation, and crystallization, produces DAR with higher purity because no isomers are generated.
[0004] During the hydrogenation reaction, 2-chloro-4,6-dinitroresorcinol undergoes hydrogenation and dechlorination reactions under the action of a catalyst and a dechlorination accelerator to generate 4,6-diaminoresorcinol. The 4,6-diaminoresorcinol in the hydrogenation solution reacts with hydrochloric acid to form a salt that precipitates from the mother liquor. The salt-forming solution is filtered to obtain crude DAR hydrochloride containing the catalyst. This crude product is then purified by removing the catalyst and recrystallization to prepare 4,6-diaminoresorcinol hydrochloride.
[0005] The high-salt crystallization mother liquor in the preparation process of 4,6-diaminoresorcinol hydrochloride needs to be thoroughly treated to achieve zero discharge of "three wastes". Summary of the Invention
[0006] Purpose of the invention: The purpose of this invention is to provide a method for treating high-salt mother liquor.
[0007] This invention proposes a treatment method for the high-salt crystallization mother liquor during the preparation of 4,6-diaminoresorcinol hydrochloride. The method recovers usable components (mainly sodium chloride and a small amount of organic sodium salt, with a sodium chloride content exceeding 95%), achieving zero discharge of wastewater, waste gas, and solid waste, and thoroughly treating the high-salt waste liquor. The recovered solid salts, after appropriate treatment, can be used as industrial salt raw materials in the chlor-alkali industry.
[0008] Technical solution: The objective of this invention is achieved through the following technical solution:
[0009] This invention provides a method for treating high-salt mother liquor, comprising the following steps:
[0010] (1) Neutralize the mother liquor by adding alkali first;
[0011] (2) The neutralized crystallization mother liquor is subjected to triple-effect evaporation in a triple-effect evaporator, and the evaporation condensate is recycled.
[0012] (3) The residual liquid after evaporation is subjected to freeze crystallization, which mainly produces sodium chloride and a small amount of organic sodium salts, with a sodium chloride content of over 95%. The precipitated solid salts are collected and recovered.
[0013] (4) The remaining mother liquor is returned to the triple-effect evaporator for recycling.
[0014] In this invention, most of the solid salts will precipitate out, mainly sodium chloride and sodium salts of a small amount of organic matter. The sodium chloride content reaches more than 95%. The recovered solid salts can be used as industrial salt raw materials for the chlor-alkali industry after appropriate treatment.
[0015] Preferably, in step (1), the alkali neutralization treatment uses 30% liquid alkali.
[0016] Preferably, in step (1), the amount of alkali required for neutralizing the crystallization mother liquor is calculated based on the acid content of each batch of crystallization mother liquor, and the crystallization mother liquor is neutralized to pH 7-8.
[0017] Further, the mother liquor is neutralized to pH 7.0-7.5.
[0018] Preferably, in step (2), the heating temperature of the triple-effect evaporation treatment is controlled at 105℃-135℃.
[0019] Preferably, in step (2), the recovery rate of the evaporated condensate is 15%-35% of the crystallization mother liquor.
[0020] Preferably, in step (3), the temperature of the freeze-crystallization is -10°C to -25°C.
[0021] Preferably, in step (3), the freezing crystallization adopts a programmed cooling control of the freezing temperature, and the cooling rate is 2°C per minute.
[0022] Preferably, in step (3), the freezing and crystallization time is 20 min to 40 min.
[0023] Furthermore, the freeze-crystallization time is 30-40 minutes.
[0024] Beneficial effects:
[0025] This invention provides a method for thoroughly treating the high-salt crystallization mother liquor from the hydrogenation process to prepare 4,6-diaminoresorcinol hydrochloride, recovering usable materials and reducing production costs. This method effectively solves the problem of treating high-concentration chloride-containing wastewater, addressing the challenges of wastewater treatment while fully meeting the requirements of energy-saving and environmentally friendly production. Attached Figure Description
[0026] Figure 1 This is a flowchart illustrating the processing of the crystallization mother liquor of this invention. Detailed Implementation
[0027] The technical solution of the present invention will be described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the embodiments described.
[0028] In the embodiments of the present invention, the recrystallization mother liquor of 4,6-diaminoresorcinol hydrochloride contains hydrochloric acid (12%), 4,6-diaminoresorcinol hydrochloride (2%), and water (86%).
[0029] The treatment process for the above-mentioned crystallization mother liquor is as follows: Figure 1 Add crystallization mother liquor and 30% sodium hydroxide solution to the neutralization vessel to neutralize the crystallization mother liquor; the neutralized mother liquor is then subjected to triple-effect evaporation using a complete set of triple-effect evaporation equipment, and the condensate is reused; the residual liquid after evaporation enters the freeze crystallization device for freeze crystallization; after freeze treatment, centrifuge is used to separate and collect the precipitated solid salts for recycling; the centrifuged mother liquor is then recycled back into the triple-effect evaporation equipment.
[0030] Example 1
[0031] Take 600 ml of the recrystallization mother liquor of 4,6-diaminoresorcinol hydrochloride and determine the acid concentration of the mother liquor by potentiometric titration. Based on the acid concentration, add 46 ml of 30% sodium hydroxide solution to neutralize to pH 7.0. Perform triple-effect evaporation on the neutralized mother liquor, controlling the evaporation temperature at 135℃, and recover 210 ml of condensate.
[0032] The residual liquid after evaporation is subjected to freeze crystallization at a controlled temperature of -25°C for 30 minutes, resulting in the precipitation of 104g of solid salts (mainly sodium chloride and a small amount of organic sodium salts, with a sodium chloride content exceeding 95%), which are collected and bagged. The recovered solid salts, after appropriate treatment, can be used as industrial salt raw materials in the chlor-alkali industry. The high-salt mother liquor after freeze-treatment is pumped back to the triple-effect evaporator for recycling. This method achieves the harmless treatment of the recrystallization mother liquor.
[0033] Example 2
[0034] Take 600 ml of the recrystallization mother liquor of 4,6-diaminoresorcinol hydrochloride and determine its acid concentration by potentiometric titration. Based on the acid concentration, add 55 ml of 30% sodium hydroxide solution to neutralize to pH 7.5. Perform triple-effect evaporation on the neutralized mother liquor, controlling the evaporation temperature at 135℃, and recover 200 ml of condensate.
[0035] The residual liquid after evaporation is subjected to freeze crystallization at a controlled temperature of -20°C for 40 minutes, resulting in the precipitation of 95g of solid salts (mainly sodium chloride and a small amount of organic sodium salts, with a sodium chloride content exceeding 95%), which are then collected and bagged. The recovered solid salts, after appropriate treatment, can be used as industrial salt raw materials in the chlor-alkali industry. The high-salt mother liquor after freeze-treatment is pumped back to the triple-effect evaporator for recycling. This method achieves the harmless treatment of the recrystallization mother liquor.
[0036] Example 3
[0037] Take 600 ml of the recrystallization mother liquor of 4,6-diaminoresorcinol hydrochloride and determine the acid concentration of the mother liquor by potentiometric titration. Based on the acid concentration, add 50 ml of 30% sodium hydroxide solution to neutralize to pH 7.2; subject the neutralized mother liquor to triple-effect evaporation treatment, controlling the evaporation temperature at 105℃, and recover 90 ml of condensate.
[0038] The residual liquid after evaporation is subjected to freeze crystallization at a controlled temperature of -15℃ for 35 minutes, resulting in the precipitation of 75g of solid salts (mainly sodium chloride and a small amount of organic sodium salts, with a sodium chloride content exceeding 95%), which are then collected and bagged. The recovered solid salts, after appropriate treatment, can be used as industrial salt raw materials in the chlor-alkali industry. The high-salt mother liquor after freeze-treatment is pumped back to the triple-effect evaporator for recycling. This method achieves the harmless treatment of the recrystallization mother liquor.
[0039] Example 4
[0040] Take 600 ml of the recrystallization mother liquor of 4,6-diaminoresorcinol hydrochloride and determine the acid concentration of the mother liquor by potentiometric titration. Based on the acid concentration, add 50 ml of 30% sodium hydroxide solution to neutralize to pH 7.2; perform triple-effect evaporation on the neutralized mother liquor, controlling the evaporation temperature at 115℃, and recover 150 ml of condensate.
[0041] The residual liquid after evaporation is subjected to freeze crystallization at a controlled temperature of -10℃ for 20 minutes, resulting in the precipitation of 60g of solid salts (mainly sodium chloride and a small amount of organic sodium salts, with a sodium chloride content exceeding 95%), which are then collected and bagged. The recovered solid salts, after appropriate treatment, can be used as industrial salt raw materials in the chlor-alkali industry. The high-salt mother liquor after freeze-treatment is pumped back to the triple-effect evaporator for recycling. This method achieves the harmless treatment of the recrystallization mother liquor.
[0042] Example 5
[0043] Take 600 ml of the recrystallization mother liquor of 4,6-diaminoresorcinol hydrochloride and determine the acid concentration of the mother liquor by potentiometric titration. Based on the acid concentration, add 50 ml of 30% sodium hydroxide solution to neutralize to pH 7.2; perform triple-effect evaporation on the neutralized mother liquor, control the evaporation temperature at 120℃, and recover 160 ml of condensate.
[0044] The residual liquid after evaporation is subjected to freeze crystallization at a controlled temperature of -20℃ for 40 minutes, resulting in the precipitation of 90g of solid salts (mainly sodium chloride and a small amount of organic sodium salts, with a sodium chloride content exceeding 95%), which are then collected and bagged. The recovered solid salts, after appropriate treatment, can be used as industrial salt raw materials in the chlor-alkali industry. The high-salt mother liquor after freeze-treatment is pumped back to the triple-effect evaporator for recycling. This method achieves the harmless treatment of the recrystallization mother liquor.
[0045] Example 6
[0046] Take 600 ml of the recrystallization mother liquor of 4,6-diaminoresorcinol hydrochloride and determine the acid concentration of the mother liquor by potentiometric titration. Based on the acid concentration, add 50 ml of 30% sodium hydroxide solution to neutralize to pH 7.2; perform triple-effect evaporation on the neutralized mother liquor, controlling the evaporation temperature at 125℃, and recover 180 ml of condensate.
[0047] The residual liquid after evaporation is subjected to freeze crystallization at a controlled temperature of -20°C for 30 minutes, resulting in the precipitation of 90g of solid salts (mainly sodium chloride and a small amount of organic sodium salts, with a sodium chloride content exceeding 95%), which are then collected and bagged. The recovered solid salts, after appropriate treatment, can be used as industrial salt raw materials in the chlor-alkali industry. The high-salt mother liquor after freeze-treatment is pumped back to the triple-effect evaporator for recycling. This method achieves the harmless treatment of the recrystallization mother liquor.
[0048] Example 7
[0049] Take 600 ml of the recrystallization mother liquor of 4,6-diaminoresorcinol hydrochloride and determine the acid concentration of the mother liquor by potentiometric titration. Based on the acid concentration, add 50 ml of 30% sodium hydroxide solution to neutralize to pH 7.2; then perform triple-effect evaporation on the neutralized mother liquor, controlling the evaporation temperature at 130℃, and recover 190 ml of condensate.
[0050] The residual liquid after evaporation is subjected to freeze crystallization at a controlled temperature of -25°C for 30 minutes, resulting in the precipitation of 100g of solid salts (mainly sodium chloride and a small amount of organic sodium salts, with a sodium chloride content exceeding 95%), which are then collected and bagged. The recovered solid salts, after appropriate treatment, can be used as industrial salt raw materials in the chlor-alkali industry. The high-salt mother liquor after freeze-treatment is pumped back to the triple-effect evaporator for recycling. This method achieves the harmless treatment of the recrystallization mother liquor.
[0051] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.
Claims
1. A method for treating high-salt mother liquor, characterized in that, Includes the following steps: (1) Neutralize the mother liquor by adding alkali first; (2) The neutralized crystallization mother liquor is subjected to triple-effect evaporation in a triple-effect evaporator, and the evaporation condensate is recycled. (3) The residual liquid after evaporation is subjected to freeze crystallization treatment, and the precipitated solid salts are collected; (4) The remaining mother liquor is returned to the triple-effect evaporator for recycling.
2. The processing method according to claim 1, characterized in that, In step (1), the alkali neutralization treatment uses 30% liquid alkali.
3. The processing method according to claim 1, characterized in that, In step (1), the amount of alkali required for neutralization of the crystallization mother liquor is calculated based on the acid content of each batch of crystallization mother liquor, and the crystallization mother liquor is neutralized to pH 7-8.
4. The processing method according to claim 1, characterized in that, In step (2), the heating temperature of the triple-effect evaporation process is controlled at 105℃-135℃.
5. The processing method according to claim 1, characterized in that, In step (2), the recovery rate of the evaporated condensate is 15%-35% of the crystallization mother liquor.
6. The processing method according to claim 1, characterized in that, In step (3), the temperature of the freeze crystallization is -10°C to -25°C.
7. The processing method according to claim 1, characterized in that, In step (3), the freezing crystallization adopts a programmed cooling control of the freezing temperature, with a cooling rate of 2°C per minute.
8. The processing method according to claim 1, characterized in that, In step (3), the freezing and crystallization time is 20 min to 40 min.
9. The processing method according to claim 8, characterized in that, The freeze-crystallization time is 30-40 minutes.