A high-efficiency treatment method for terephthalic acid oxidation residue

Abstract

This invention relates to the field of terephthalic acid oxidation residue technology, specifically a high-efficiency treatment method for terephthalic acid oxidation residue. The method includes the following steps: S1. Pretreatment; S2. Separation; S3. Evaporation and concentration; S4. Incineration; S5. Ash dissolution; S6. Filtration; S7. Sodium carbonate recovery; S8. Sodium carbonate recycling; S9. Bromine recovery and utilization; S10. Cobalt-manganese catalyst recovery; S11. Precipitate treatment; S12. Cobalt-manganese catalyst recycling. This application utilizes the waste heat or residual heat from the top of the xylene oxidation unit as a heat source to heat and concentrate the first filtrate. The acetic acid flash evaporator in the crystallizer serves as the heat source for evaporator V3 to evaporate and concentrate sodium carbonate, reducing process energy consumption and improving sodium carbonate recovery efficiency. Simultaneously, it achieves the conversion of organic matter in the residue into carbonates for recycling, and realizes the recovery and recycling of the cobalt-manganese-bromine catalyst in the residue.

Description

Technical Field

[0001] This invention relates to the field of terephthalic acid oxidation residue technology, specifically to a high-efficiency treatment method for terephthalic acid oxidation residue. Background Art

[0002] Permethrin (PTA) is an important organic synthetic monomer in the chemical industry, mainly used in the production of polyethylene terephthalate (PET) and bottle-grade polyester. Currently, China's PTA production capacity has exceeded 50 million tons. To ensure the quality of PTA products, the mother liquor needs to be extracted during the PTA production process and then sent to a thin-film evaporator to recover acetic acid. The distillation residue is discharged as waste, accounting for approximately 0.45-0.6% of the total PTA production. The main components of this residue are oxidation byproducts of organic acids, along with small amounts of cobalt, manganese, heavy metals, and bromides. Furthermore, during PTA manufacturing, alkaline solutions are often used for cleaning to remove blockages in various equipment and pipelines. Other waste materials from leaks, spills, and drips from the site and system are also discharged into waste collection ponds. These waste residues are also discharged into the PTA oxidation waste residue system. Because these waste residues are complex in composition and their composition and content fluctuate with the high-temperature oxidation process, comprehensive recycling and utilization of the waste residues presents challenges.

[0003] For example, Chinese patent application CN2021100727035 describes a comprehensive utilization process for PTA oxidation residue. This patent involves esterifying and distilling the PTA oxidation residue with octanol and other substances to obtain esters. The residue from the distillation vessel is then incinerated to obtain cobalt, manganese, and bromide salts. These are then extracted and purified to obtain cobalt sulfate and manganese sulfate. Further precipitation, washing, concentration, and crystallization with sodium bicarbonate yield cobalt acetate and manganese acetate. Sodium bromide is then dissolved, decolorized, concentrated, crystallized, and centrifuged to obtain the final product. This process is complex and unstable, generates large amounts of wastewater, and causes severe environmental pollution.

[0004] A method for recycling PTA oxidation residue, disclosed in Chinese patent application number CN2013104108951, involves mixing PTA oxidation residue, water, and an oil-phase extractant, followed by extraction, distillation, and separation to obtain a mixture of benzoic acid, p-methylbenzoic acid, isophthalic acid, and terephthalic acid. However, this method also suffers from drawbacks such as complex processes, easy equipment and pipeline blockage during distillation, high recycling costs, and the inability to recover sodium carbonate and bromine.

[0005] Therefore, it is necessary to design a high-efficiency treatment method for terephthalic acid oxidation residue to efficiently recover sodium carbonate and bromine, reduce process energy consumption, and improve recovery efficiency. Summary of the Invention

[0006] To address the above problems, this invention provides a high-efficiency treatment method for terephthalic acid oxidation residue.

[0007] The technical solution adopted by this invention to solve its technical problem is: a high-efficiency treatment method for terephthalic acid oxidation residue, comprising the following steps:

[0008] S1. Pretreatment: Add the terephthalic acid oxidation residue to the mixing device, then add sodium carbonate or sodium hydroxide and an aqueous solution of sodium carbonate, stir and react, and adjust the pH of the solution to 7-8, controlling the solid content in the solution to 3-5%;

[0009] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate, wherein the solid content in the first filtrate is 3-5%;

[0010] S3. Evaporation and Concentration: The first filtrate obtained in step S2 is added to the multi-effect evaporation system V1. The residual heat at the top of the dehydration tower of the xylene oxidation unit, which is 85°C, is used as a heat source for evaporation and concentration. The solid content of the first filtrate obtained in step S2 is concentrated from 3~5% to 25~40%. Then it is sent to the single-effect evaporation system V2 for evaporation and concentration to 50~70% to obtain a concentrated liquid. The water vapor generated during the evaporation process is recovered after cooling.

[0011] S4. Incineration: The concentrated liquid obtained in step S3 is sent to an incinerator for incineration to obtain ash residue. The high-temperature flue gas generated during the incineration process is heat-treated by heat exchange furnace and saturated water in water-cooled wall to obtain water vapor with a temperature of 180~360℃ and a pressure of 1.0~9.8 MPa.

[0012] S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, and then add pure water to make the ash and slag concentration reach 15~25% to obtain ash and slag dissolution solution.

[0013] S6. Filtration: The ash residue solution obtained in step S5 is filtered. The filtered solid filter cake is washed with pulping water and sent to a centrifuge to separate solid B and filtrate. The filtrate is pumped into evaporator V3.

[0014] S7. Sodium carbonate recovery: Acetic acid flash vapor from the terephthalic acid crystallizer in the xylene oxidation unit is used as the heat source for evaporator V3. The flash vapor temperature is 85~95℃ and the pressure is -46~-55Kpag. When the sodium carbonate concentration in the salt leg at the bottom of evaporator V3 reaches 28~32%, it is collected by gravity flow and sent to evaporator V4 to further concentrate the sodium carbonate concentration to 58~62%. Then, the filter cake with a moisture content of 13~17% and bromine-containing mother liquor are obtained by centrifugation. The filter cake is directly used to prepare sodium carbonate aqueous solution or dried to obtain solid sodium carbonate product. The water vapor generated during the evaporation process is recovered after cooling.

[0015] S8. Sodium carbonate recycling: Add the evaporated water or pure water condensed by the condenser during the evaporation process in steps S3 and S7 to the filter cake obtained in step S7 to prepare sodium carbonate with a concentration of 20~25%, and return it to step S1 for recycling.

[0016] S9. Bromine recovery and utilization: When the sodium bromide content in the bromine-containing mother liquor in step S7 reaches 30~43%, the bromine-containing mother liquor is transferred to the reaction evaporator. Phosphoric acid or sulfuric acid aqueous solution is added to the reaction evaporator, heated to boiling, and the distillate is collected to obtain crude hydrobromic acid, which is sent to the catalyst device as raw material. When no hydrobromic acid is distilled off, the remaining liquid is sent to the crystallization kettle, cooled or evaporated to crystallize and obtain sodium hydrogen phosphate or sodium sulfate products.

[0017] S10. Recovery of cobalt-manganese catalyst: Add solid A obtained in step S2 to a mixer, add dilute acetic acid to the mixer, heat to 80℃~boiling, maintain for 30~180min, filter while hot to obtain catalyst filtrate and solid C;

[0018] S11. Precipitate treatment: Solid B obtained in step S6 and solid C obtained in step S10 are fed into the reactor, and hydrobromic acid and water are added to react. When the concentration of cobalt and manganese ions in the solution no longer changes or the dissolution is complete, cobalt carbonate and / or manganese carbonate are added to adjust the pH of the solution to 5-6 until it is completely dissolved. The catalyst filtrate is obtained by filtration.

[0019] S12. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S10 and S11 is returned to the catalyst preparation system for use.

[0020] As an optimization, in step S1, the sodium hydroxide aqueous solution contains 20-40% sodium hydroxide, and the sodium carbonate aqueous solution contains 20-25% sodium carbonate.

[0021] As an optimization, the multi-effect evaporation system V1 in step S3 includes a plate falling film evaporator and a forced circulation evaporator;

[0022] The single-effect evaporation system V2 includes two forced circulation evaporators;

[0023] The condensate at the top of the evaporator is returned to the system for use as PAT pulping water;

[0024] In step S3, the carrier of the waste heat at the top of the dehydration tower of the xylene oxidation unit is an organic gas containing 61-65% isobutyl acetate, 22-25.7% water and 9-12% methyl acetate.

[0025] Preferably, the steam pressure in step S4 is 5.0~9.8 MPa, and the temperature is 270~360℃, resulting in higher energy efficiency and a wider range of applications.

[0026] As an optimization, the water vapor generated during the evaporation process in steps S3 and S7 is condensed by a condenser and then pumped by a condensate pump to the PTA pulping water tank and the sodium carbonate dissolving tank for recycling.

[0027] As an optimization, in step S7, the acetic acid condensate after condensation in the acetic acid flash evaporator is pumped back to the condenser of the terephthalic acid crystallizer for recycling. Through such a loop, the energy in the acetic acid flash vapor is recovered and reused.

[0028] As an optimization, in step S9, the molar ratio of bromide ions to phosphoric acid or sulfuric acid is 2:1.01~1.1, and the concentration of added phosphoric acid is 40~98% and the concentration of sulfuric acid is 40~95%.

[0029] As an optimization, the dilute acetic acid in step S10 is obtained from the recovered dilute acetic acid in the terephthalic acid oxidation device or is prepared by mixing fresh acetic acid, wherein the acetic acid content is 25-40%, and the molar ratio of cobalt and manganese to acetic acid is 1:2.05-6.0.

[0030] As an optimization, in step S11, the molar ratio of cobalt and manganese to hydrobromic acid in both solid B and solid C is 1:2.2~3.0.

[0031] As an optimization, the recycling of the cobalt-manganese catalyst in step S12 involves mixing the catalyst filtrate obtained in steps S10 and S11 with fresh catalyst in any proportion to obtain a cobalt-manganese-bromine mixed catalyst, which is then returned to the system for recycling.

[0032] The secondary steam evaporated from the plate falling film evaporator has a temperature of about 70°C and a pressure of about -69 kPag. Part of it is used as a heat source for the multi-effect evaporation system V1 to concentrate the collected filtrate from a concentration of 3-5% to 25-40%. The excess secondary steam and the water vapor evaporated from the single-effect evaporator V2 are condensed by the condenser and then pumped for recycling or sent to the sewage unit.

[0033] After the concentrated liquid from the second effect of the multi-effect evaporation system V1 enters the raw material tank of the single-effect evaporation system V2 for buffering, the raw material liquid is sent to the forced circulation evaporator of the single-effect evaporation system V2 for evaporation and concentration by the feed pump. The heat source of the heater of the single-effect evaporation system V2 comes from the secondary steam of the evaporator separator of the multi-effect evaporation system V1, with a temperature of about 73.8℃ and -64kPag.

[0034] The secondary steam evaporated by the forced circulation evaporator of the single-effect evaporation system V2 has a temperature of about 50°C and a pressure of about -88 kPag. After being condensed by the condenser, the secondary steam is sent to the sewage unit by the condensate pump.

[0035] The liquid concentration in the forced circulation pump of the single-effect evaporation system V2 is about 36%. It is sent to the multi-effect evaporation system V1 for further concentration through the feed pump outlet. The heat source of the shell side of the heater of the multi-effect evaporation system V1 comes from the exhaust gas of the boiler continuous blow-out expansion tank and the condensate expansion tank or the low-pressure steam in the plant area. The condensate is sent to the boiler deaerator through the transfer pump. The concentrated liquid after evaporation in the multi-effect evaporation system V1 is sent to the feed buffer tank in front of the furnace through the discharge pump. The normal discharge concentration of the single-effect evaporation system V2 is 53%~70%. The system shares a vacuum system to maintain the system pressure. The vacuum pump outlet is discharged after passing through the gas-liquid separator to the water seal tank for alkaline washing and then vented.

[0036] The concentrate from the single-effect evaporation system V2 enters the concentrate feed tank through the top of the tank. The feed tank is equipped with a circulating pump for jet stirring to prevent the concentrate from settling and separating. The gas phase of the feed tank enters the water seal tank. The feed pump sends the concentrate to the insulated furnace, where it is atomized and evenly dispersed into the furnace for combustion. The feed pressure of the concentrate gun is controlled by the reflux control valve.

[0037] The insulated furnace is equipped with biogas and natural gas nozzles, and the biogas and natural gas feed rates are adjusted according to the concentrate feed rate. After the concentrate is burned in the insulated furnace, the molten sodium carbonate and sodium bromide flow around the furnace to the melting pool at the bottom of the furnace. The flue gas with a temperature ≥1100℃ enters the heat exchange furnace and exchanges heat with saturated water in the water-cooled wall. The heat-absorbing saturated water flows to the steam drum through a thermal circulation system, where gas-liquid separation occurs. The separated saturated steam enters the superheater and desuperheater, and the steam outlet temperature is controlled at 360℃. The flue gas then passes through a water-cooled screen, superheater, evaporator, economizer, and a six-stage air preheater for heat exchange before entering the bag filter. After dust removal, the flue gas enters the SCR for denitrification and then enters a two-stage air preheater for further heat recovery. Finally, it is discharged into the atmosphere through the chimney via the induced draft fan outlet. An online flue gas monitoring instrument is installed on the chimney body. The insulated furnace has two outlets at the bottom, equipped with chutes. The molten material flows through the chutes to a twin-shaft cooler, where the rapidly cooled sodium carbonate and sodium bromide form lumps. After being cooled and crushed by the twin-shaft cooler, the molten material falls onto a screw conveyor. The screw conveyor sends the ash to a drum cooler for further cooling before it enters a crusher. The crushed ash falls onto a bidirectional screw conveyor, which can either send it to a slag melting tank or be packaged. The bag filter dust collector is equipped with a bidirectional screw conveyor at the bottom, which normally sends the ash collected by the bags to the ash melting tank, or it can be cooled by a thin-film cooler and then packaged.

[0038] The beneficial effects of this solution are that it provides a highly efficient method for treating terephthalic acid oxidation residue, which has the following advantages:

[0039] The system utilizes the waste heat or residual heat from the top of the xylene oxidation unit as a heat source to heat and concentrate the first filtrate, and uses the acetic acid flash vapor in the crystallizer as a heat source for evaporator V3 to evaporate and concentrate sodium carbonate, thereby reducing energy consumption in the residue treatment process.

[0040] The high-temperature flue gas generated during the incineration process is exchanged to obtain superheated steam, which can be used for heating other processes, achieving high efficiency and energy saving and reducing energy waste;

[0041] This technology enables the conversion of organic matter in terephthalic acid oxidation residue into carbonates for recycling.

[0042] The recovery and recycling of cobalt, manganese, and bromine catalysts in terephthalic acid oxidation residues has been achieved.

[0043] The water produced during the treatment process is recycled, with no wastewater discharge.

[0044] The residue treatment process is green and energy-saving, with no waste emissions. Detailed Implementation

[0045] Example 1:

[0046] A high-efficiency treatment method for terephthalic acid oxidation residue includes the following steps:

[0047] S1. Pretreatment: Add the terephthalic acid oxidation residue to the mixing device, then add sodium carbonate aqueous solution and stir to react, adjust the pH of the solution to 7, and control the solid content of the solution to 3%;

[0048] The sodium carbonate aqueous solution contains 20% sodium carbonate.

[0049] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate, wherein the solid content of the first filtrate is 3%;

[0050] S3. Evaporation and Concentration: The first filtrate obtained in step S2 is added to the multi-effect evaporation system V1. The residual heat at the top of the dehydration tower of the xylene oxidation unit, which is 85°C, is used as a heat source for evaporation and concentration. The solid content of the first filtrate obtained in step S2 is concentrated from 3% to 25%. Then it is sent to the single-effect evaporation system V2 for evaporation and concentration to 50% to obtain a concentrated liquid. The water vapor generated during the evaporation process is recovered after cooling.

[0051] The multi-effect evaporation system V1 includes one plate falling film evaporator and one forced circulation evaporator;

[0052] The single-effect evaporation system V2 includes two forced circulation evaporators;

[0053] The condensate at the top of the evaporator is returned to the system as pulping water;

[0054] The waste heat carrier at the top of the dehydration tower of the xylene oxidation unit is an organic gas containing 61% isobutyl acetate, 22% water and 9% methyl acetate.

[0055] The water vapor generated during the evaporation process is condensed by the condenser and then pumped by the condensate pump to the PAT pulping water tank, sodium carbonate dissolving tank or ash dissolving tank for recycling.

[0056] S4. Incineration: The concentrated liquid obtained in step S3 is sent to the incinerator for incineration to obtain ash residue. The high-temperature flue gas generated during the incineration process is heat-treated by heat exchange furnace and saturated water in water-cooled wall to obtain 5.0 MPa, 180℃ water steam.

[0057] S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, and then add pure water. The pure water is the distilled water recovered from the evaporation and concentration process in step S3 and pure water from the pure water device, so that the ash and slag concentration reaches 15% and the ash and slag dissolution solution is obtained.

[0058] S6. Filtration: The ash residue solution obtained in step S5 is filtered. The filtered solid filter cake is washed with pulping water and sent to a centrifuge to separate solid B and filtrate. The filtrate is pumped into evaporator V3.

[0059] S7. Sodium carbonate recovery: Acetic acid flash vapor from the terephthalic acid crystallizer in the xylene oxidation unit is used as the heat source for evaporator V3. The flash vapor temperature is 85℃ and the pressure is -46Kpag. When the sodium carbonate concentration in the salt leg at the bottom of evaporator V3 reaches 28%, it is collected by gravity flow and sent to evaporator V4 to further concentrate the sodium carbonate concentration to 58%. Then, the filter cake with a moisture content of 13% and bromine-containing mother liquor are obtained by centrifugation. The filter cake is directly used to prepare sodium carbonate aqueous solution or dried to obtain solid sodium carbonate product. The water vapor generated during the evaporation process is recovered after cooling.

[0060] The water vapor generated during the evaporation process is condensed by a condenser and then pumped to a sodium carbonate dissolving tank for recycling.

[0061] The acetic acid condensate after condensation in the acetic acid flash evaporator is pumped back to the condenser of the terephthalic acid crystallizer for recycling.

[0062] S8. Sodium carbonate recycling: Add the evaporated water condensed by the condenser during the evaporation process in steps S3 and S7 to the filter cake obtained in step S7 to prepare sodium carbonate with a concentration of 20%, and return it to step S1 for recycling.

[0063] S9. Bromine recovery and utilization: When the sodium bromide content in the bromine-containing mother liquor in step S7 reaches 30%, the bromine-containing mother liquor is transferred to the reaction evaporator. Phosphoric acid aqueous solution is added to the reaction evaporator, heated to boiling, and the distillate is collected to obtain crude hydrobromic acid, which is sent to the catalyst device as raw material. When no hydrobromic acid is distilled off, the remaining liquid is sent to the crystallization kettle and cooled to obtain sodium hydrogen phosphate product.

[0064] The molar ratio of bromide ions to phosphoric acid is 2:1.01, and the concentration of added phosphoric acid is 40-98%.

[0065] S10. Recovery of cobalt-manganese catalyst: Add solid A obtained in step S2 to a mixer, add dilute acetic acid to the mixer, heat to boiling, maintain for 180 min, filter while hot to obtain catalyst filtrate and solid C;

[0066] The dilute acetic acid is derived from the recovered dilute acetic acid in the terephthalic acid oxidation unit or is prepared by mixing fresh acetic acid, wherein the acetic acid content is 25%, and the molar ratio of cobalt and manganese to acetic acid is 1:2.05.

[0067] S11. Precipitate Treatment: Solid B obtained in step S6 and solid C obtained in step S10 are fed into a reactor, and hydrobromic acid and water are added to react. The molar ratio of cobalt manganese to hydrobromic acid is 1:2.2. When the concentration of cobalt and manganese ions in the solution no longer changes, cobalt carbonate is added and stirred to dissolve. The pH of the solution is adjusted to 5, and the solution is filtered to obtain the catalyst filtrate. After the reaction is completed, the concentration of cobalt ions is 3.2%.

[0068] The molar ratio of cobalt and manganese to hydrobromic acid in both solids B and C is 1:2.2;

[0069] S12. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S10 and S11 is returned to the catalyst preparation system and mixed with fresh catalyst for reuse;

[0070] The catalyst filtrate is mixed with fresh catalyst in any proportion.

[0071] Example 2:

[0072] A high-efficiency treatment method for terephthalic acid oxidation residue includes the following steps:

[0073] S1. Pretreatment: Add the terephthalic acid oxidation residue to the mixing device, then add sodium hydroxide aqueous solution and stir to react. Adjust the pH of the solution to 4.1, then add sodium carbonate aqueous solution to adjust the pH of the solution to 8, and control the solid content in the solution to 5%.

[0074] The sodium hydroxide aqueous solution contains 40% sodium hydroxide, and the sodium carbonate aqueous solution contains 20% sodium carbonate.

[0075] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate, wherein the solid content of the first filtrate is 5%;

[0076] S3. Evaporation and Concentration: The first filtrate obtained in step S2 is added to the multi-effect evaporation system V1. The residual heat at the top of the dehydration tower of the xylene oxidation unit, which is 85°C, is used as a heat source for evaporation and concentration. The solid content of the first filtrate obtained in step S2 is concentrated from 5% to 25-40%. Then it is sent to the single-effect evaporation system V2 for evaporation and concentration to 70% to obtain a concentrated liquid. The water vapor generated during the evaporation process is recovered after cooling.

[0077] The multi-effect evaporation system V1 includes one plate falling film evaporator and one forced circulation evaporator;

[0078] The single-effect evaporation system V2 includes two forced circulation evaporators;

[0079] The condensate at the top of the evaporator is returned to the system as pulping water;

[0080] In step S3, the carrier of the waste heat at the top of the dehydration tower of the xylene oxidation unit is an organic gas containing 65% isobutyl acetate, 25.7% water and 12% methyl acetate.

[0081] The water vapor generated during the evaporation process is condensed by the condenser and then pumped by the condensate pump to the PAT water tank, sodium carbonate dissolving tank or ash dissolving tank for recycling.

[0082] S4. Incineration: The concentrated liquid obtained in step S3 is sent to the incinerator for incineration to obtain ash residue. The high-temperature flue gas generated during the incineration process is heat-treated by heat exchange furnace and saturated water in water-cooled wall to obtain 9.8 MPa, 360℃ water vapor.

[0083] S5. Ash Dissolution: The ash obtained in step S4 is added to the dissolution tank, followed by pure water from a pure water device. This brings the ash concentration to 15%, yielding an ash dissolution solution.

[0084] S6. Filtration: The ash residue solution obtained in step S5 is filtered. The filtered solid filter cake is washed with pulping water and sent to a centrifuge to separate solid B and filtrate. The filtrate is pumped into evaporator V3.

[0085] S7. Sodium carbonate recovery: Acetic acid flash vapor from the terephthalic acid crystallizer in the xylene oxidation unit is used as the heat source for evaporator V3. The flash vapor temperature is 95℃ and the pressure is -55Kpag. When the sodium carbonate concentration in the salt leg at the bottom of evaporator V3 reaches 32%, it is collected by gravity flow and sent to evaporator V4 to further concentrate the sodium carbonate concentration to 62%. Then, the filter cake with a moisture content of 17% and bromine-containing mother liquor are obtained by centrifugation. The filter cake is directly used to prepare sodium carbonate aqueous solution or dried to obtain solid sodium carbonate product. The water vapor generated during the evaporation process is recovered after cooling.

[0086] The acetic acid condensate after condensation in the acetic acid flash evaporator is pumped back to the condenser of the terephthalic acid crystallizer for recycling.

[0087] S8. Sodium carbonate recycling: Add pure water to the filter cake obtained in step S7 to prepare a 25% concentration of sodium carbonate, and return to step S1 for recycling.

[0088] S9. Bromine recovery and utilization: When the sodium bromide content in the bromine-containing mother liquor in step S7 reaches 43%, the bromine-containing mother liquor is transferred to the reaction evaporator. A sulfuric acid aqueous solution is added to the reaction evaporator, heated to boiling, and the distillate is collected to obtain crude hydrobromic acid, which is sent to the catalyst device as raw material. When no hydrobromic acid is distilled off, the remaining liquid is sent to the crystallization kettle for evaporation and crystallization to obtain sodium sulfate product.

[0089] The molar ratio of bromide ions to phosphoric acid or sulfuric acid is 2:1.1, and the concentration of sulfuric acid is 40%.

[0090] S10. Recovery of cobalt-manganese catalyst: Add solid A obtained in step S2 to a mixer, add dilute acetic acid to the mixer, heat to 80°C, maintain for 30 min, filter while hot to obtain catalyst filtrate and solid C;

[0091] The dilute acetic acid is derived from the recovered dilute acetic acid from the terephthalic acid oxidation unit or is prepared by mixing fresh acetic acid, wherein the acetic acid content is 40%, and the molar ratio of cobalt and manganese to acetic acid is 1:6.0.

[0092] S11. Precipitate Treatment: Solid B obtained in step S6 and solid C obtained in step S10 are fed into a reactor, and hydrobromic acid and water are added for reaction. The molar ratio of cobalt and manganese to hydrobromic acid is 1:3.0. When the concentration of cobalt and manganese ions in the solution no longer changes or dissolution is complete, manganese carbonate is added to adjust the pH of the solution to 6 until it is completely dissolved. The solution is then filtered to obtain the catalyst filtrate. After the final reaction, the manganese ion concentration is 3.5%.

[0093] The molar ratio of cobalt and manganese to hydrobromic acid in both solids B and C is 1:3.0;

[0094] S12. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S10 and S11 is returned to the catalyst preparation system and mixed with fresh catalyst for reuse;

[0095] The catalyst filtrate is mixed with fresh catalyst in any proportion.

[0096] Example 3:

[0097] A high-efficiency treatment method for terephthalic acid oxidation residue includes the following steps:

[0098] S1. Pretreatment: Add the terephthalic acid oxidation residue to the mixing device, then add sodium hydroxide aqueous solution and stir to react. Adjust the pH of the solution to 3.05, then add sodium carbonate aqueous solution to adjust the pH of the solution to 7.5, and control the solid content in the solution to 4%.

[0099] The sodium hydroxide aqueous solution contains 30% sodium hydroxide, and the sodium carbonate aqueous solution contains 25% sodium carbonate.

[0100] S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate, the solid content of which is 4.63%.

[0101] S3. Evaporation and Concentration: The first filtrate obtained in step S2 is added to the multi-effect evaporation system V1. The residual heat at the top of the dehydration tower of the xylene oxidation unit, which is 85°C, is used as a heat source for evaporation and concentration. The solid content of the first filtrate obtained in step S2 is concentrated from 4% to 33%. Then it is sent to the single-effect evaporation system V2 for evaporation and concentration to 60% to obtain a concentrated liquid. The water vapor generated during the evaporation process is recovered after cooling.

[0102] The multi-effect evaporation system V1 includes one plate falling film evaporator and one forced circulation evaporator;

[0103] The single-effect evaporation system V2 includes two forced circulation evaporators;

[0104] The condensate at the top of the evaporator is returned to the system as pulping water;

[0105] In step S3, the carrier of the waste heat at the top of the dehydration tower of the xylene oxidation unit is an organic gas containing 63% isobutyl acetate, 24% water and 10.5% methyl acetate.

[0106] The water vapor generated during the evaporation process is condensed by the condenser and then pumped by the condensate pump to the PAT pulping water tank, sodium carbonate dissolving tank or ash dissolving tank for recycling.

[0107] S4. Incineration: The concentrated liquid obtained in step S3 is sent to the incinerator for incineration to obtain ash residue. The high-temperature flue gas generated during the incineration process is heat-treated by heat exchange furnace and saturated water in water-cooled wall to obtain 5.5 MPa, 270℃ water vapor.

[0108] S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, and then add pure water to make the ash and slag concentration reach 20% to obtain the ash and slag dissolution solution.

[0109] S6. Filtration: The ash residue solution obtained in step S5 is filtered. The filtered solid filter cake is washed with pulping water and sent to a centrifuge to separate solid B and filtrate. The filtrate is pumped into evaporator V3.

[0110] S7. Sodium carbonate recovery: Acetic acid flash vapor from the terephthalic acid crystallizer in the xylene oxidation unit is used as the heat source for evaporator V3. The flash vapor temperature is 90℃ and the pressure is -50Kpag. When the sodium carbonate concentration in the salt leg at the bottom of evaporator V3 reaches 30%, it is collected by gravity flow and sent to evaporator V4 to further concentrate the sodium carbonate concentration to 60%. Then, it is separated by centrifuge to obtain a filter cake with a moisture content of 15% and a bromine-containing mother liquor. The filter cake is directly used to prepare sodium carbonate aqueous solution. The water vapor generated during the evaporation process is recovered after cooling.

[0111] The acetic acid condensate after condensation in the acetic acid flash evaporator is pumped back to the condenser of the terephthalic acid crystallizer for recycling.

[0112] S8. Sodium carbonate recycling: Add the evaporated water condensed by the condenser during the evaporation process in steps S3 and S7 to the filter cake obtained in step S7 to prepare sodium carbonate with a concentration of 23%, and return it to step S1 for recycling.

[0113] S9. Bromine recovery and utilization: When the sodium bromide content in the bromine-containing mother liquor in step S7 reaches 36%, the bromine-containing mother liquor is transferred to the reaction evaporator. Phosphoric acid aqueous solution is added to the reaction evaporator, heated to boiling, and the distillate is collected to obtain crude hydrobromic acid, which is sent to the catalyst device as raw material. When no hydrobromic acid is distilled off, the remaining liquid is sent to the crystallization kettle, cooled or evaporated to crystallize and obtain sodium hydrogen phosphate product.

[0114] The molar ratio of bromide ions to phosphoric acid or sulfuric acid is 2:1.05, and the concentration of the added phosphoric acid is 60%.

[0115] S10. Recovery of cobalt-manganese catalyst: Add solid A obtained in step S2 to a mixer, add dilute acetic acid to the mixer, heat to 95°C, maintain for 100 min, filter while hot to obtain catalyst filtrate and solid C;

[0116] The dilute acetic acid is obtained from the recovered dilute acetic acid in the terephthalic acid oxidation unit or is prepared by mixing fresh acetic acid, wherein the acetic acid content is 32% and the molar ratio of cobalt and manganese to acetic acid is 1:4.

[0117] S11. Precipitate Treatment: Solid B obtained in step S6 and solid C obtained in step S10 are fed into a reactor, and hydrobromic acid and water are added for reaction. The molar ratio of cobalt and manganese to hydrobromic acid is 1:2.6. When the concentration of cobalt and manganese ions in the solution no longer changes or dissolution is complete, cobalt carbonate and manganese carbonate are added, stirred and dissolved, and the pH of the solution is adjusted to 5.5. Cobalt carbonate and manganese carbonate are first mixed in a 1:1 molar ratio before being added. The solution is filtered to obtain the catalyst filtrate. After the final reaction, the concentrations of cobalt and manganese ions are 2.7% and 3.1%, respectively.

[0118] The molar ratio of cobalt and manganese to hydrobromic acid in both solids B and C is 1:2.6;

[0119] S12. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S10 and S11 is returned to the catalyst preparation system and mixed with fresh catalyst for reuse;

[0120] The catalyst filtrate is mixed with fresh catalyst in any proportion.

[0121] The above-described specific embodiments are merely specific examples of the present invention. The patent protection scope of the present invention includes, but is not limited to, the product form and style of the above-described specific embodiments. Any efficient treatment method for terephthalic acid oxidation residue that conforms to the claims of the present invention, and any appropriate changes or modifications made thereto by those skilled in the art, shall fall within the patent protection scope of the present invention.

Claims

1. A high-efficiency treatment method for terephthalic acid oxidation residue, characterized in that: Includes the following steps: S1. Pretreatment: Add the terephthalic acid oxidation residue to the mixing device, then add sodium carbonate aqueous solution or sodium hydroxide aqueous solution and sodium carbonate aqueous solution, stir and react, and adjust the pH of the solution to 7~8, and control the solid content in the solution to 3~5%; S2. Separation: The mixture after pretreatment in step S1 is filtered to obtain solid A and a first filtrate, wherein the solid content in the first filtrate is 3-5%; S3. Evaporation and Concentration: The first filtrate obtained in step S2 is added to the multi-effect evaporation system V1. The residual heat at the top of the dehydration tower of the xylene oxidation unit, which is 85°C, is used as a heat source for evaporation and concentration. The solid content of the first filtrate obtained in step S2 is concentrated from 3~5% to 25~40%. Then it is sent to the single-effect evaporation system V2 for evaporation and concentration to 50~70% to obtain a concentrated liquid. The water vapor generated during the evaporation process is recovered after cooling. S4. Incineration: The concentrated liquid obtained in step S3 is sent to an incinerator for incineration to obtain ash residue. The high-temperature flue gas generated during the incineration process is heat-treated by heat exchange furnace and saturated water in water-cooled wall to obtain water vapor with a pressure of 1.0~9.8MPa and a temperature of 180~360℃. S5. Ash and slag dissolution: Add the ash and slag obtained in step S4 to the dissolution tank, and then add pure water to make the ash and slag concentration reach 15~25% to obtain ash and slag dissolution solution. S6. Filtration: The ash residue solution obtained in step S5 is filtered. The filtered solid filter cake is washed with pulping water and sent to a centrifuge to separate solid B and filtrate. The filtrate is pumped into evaporator V3. S7. Sodium carbonate recovery: Acetic acid flash vapor from the terephthalic acid crystallizer in the xylene oxidation unit is used as the heat source for evaporator V3. The flash vapor temperature is 85~95℃ and the pressure is -55~-46kPag. When the sodium carbonate concentration in the salt leg at the bottom of evaporator V3 reaches 28~32%, it is collected by gravity flow and sent to evaporator V4 to further concentrate the sodium carbonate concentration to 58~62%. Then, the filter cake with a moisture content of 13~17% and bromine-containing mother liquor are obtained by centrifugation. The filter cake is directly used to prepare sodium carbonate aqueous solution or dried to obtain solid sodium carbonate product. The water vapor generated during the evaporation process is recovered after cooling. S8. Sodium carbonate recycling: Add the evaporated water or pure water condensed by the condenser during the evaporation process in steps S3 and S7 to the filter cake obtained in step S7 to prepare sodium carbonate with a concentration of 20~25%, and return it to step S1 for recycling. S9. Bromine recovery and utilization: When the sodium bromide content in the bromine-containing mother liquor in step S7 reaches 30~43%, the bromine-containing mother liquor is transferred to the reaction evaporator. Phosphoric acid or sulfuric acid aqueous solution is added to the reaction evaporator, heated to boiling, and the distillate is collected to obtain crude hydrobromic acid, which is sent to the catalyst device as raw material. When no hydrobromic acid is distilled off, the remaining liquid is sent to the crystallization kettle, cooled or evaporated to crystallize and obtain sodium hydrogen phosphate or sodium sulfate products. S10. Recovery of cobalt-manganese catalyst: Add solid A obtained in step S2 to a mixer, add dilute acetic acid to the mixer, heat to 80°C, 95°C or boiling, maintain for 30~180 min, filter while hot to obtain catalyst filtrate and solid C. S11. Precipitate treatment: Solid B obtained in step S6 and solid C obtained in step S10 are fed into the reactor, and hydrobromic acid and water are added to react. When the concentration of cobalt and manganese ions in the solution no longer changes or the dissolution is complete, cobalt carbonate and / or manganese carbonate are added to adjust the pH of the solution to 5-6 until it is completely dissolved. The catalyst filtrate is obtained by filtration. S12. Recycling of cobalt-manganese catalyst: The catalyst filtrate obtained in steps S10 and S11 is returned to the catalyst blending system and mixed with fresh catalyst for use.

2. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: In step S1, the sodium hydroxide aqueous solution contains 20-40% sodium hydroxide, and the sodium carbonate aqueous solution contains 20-25% sodium carbonate.

3. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: The multi-effect evaporation system V1 in step S3 includes a plate falling film evaporator and a forced circulation evaporator; The single-effect evaporation system V2 includes two forced circulation evaporators; The condensate at the top of the evaporator is returned to the system as PTA pulping water; In step S3, the carrier of the waste heat at the top of the dehydration tower of the xylene oxidation unit is an organic gas containing 61-65% isobutyl acetate, 22-25.7% water and 9-12% methyl acrylate.

4. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: In step S4, the pressure of the water vapor is 5.0~9.8MPa and the temperature is 270~360℃.

5. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: The water vapor generated during the evaporation process in steps S3 and S7 is condensed by the condenser and then pumped by the condensate pump to the PTA pulping water tank and the sodium carbonate dissolving tank for recycling.

6. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: In step S7, the acetic acid condensate after condensation in the acetic acid flash evaporator is pumped back to the condenser of the terephthalic acid crystallizer for recycling.

7. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: In step S9, the molar ratio of bromide ions to phosphoric acid or sulfuric acid is 2:1.01~1.1, and the concentration of added phosphoric acid is 40~98% and the concentration of added sulfuric acid is 40~95%.

8. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: The dilute acetic acid in step S10 comes from the recovered dilute acetic acid in the terephthalic acid oxidation device or is prepared by mixing fresh acetic acid, wherein the acetic acid content is 25-40%, and the molar ratio of cobalt and manganese to acetic acid is 1:2.05-6.

0.

9. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: In step S11, the molar ratio of cobalt and manganese to hydrobromic acid in both solid B and solid C is 1:2.2~3.

0.

10. The high-efficiency treatment method for terephthalic acid oxidation residue according to claim 1, characterized in that: The recycling of the cobalt-manganese catalyst in step S12 involves mixing the catalyst filtrate obtained in steps S10 and S11 with fresh catalyst in any proportion to obtain a cobalt-manganese-bromine mixed catalyst, which is then returned to the system for recycling.