Efficient and energy-saving PTA (pure terephthalic acid) wastewater treatment device

Abstract

The utility model discloses an efficient and energy-saving PTA (pure terephthalic acid) wastewater treatment device which comprises a multi-effect evaporation unit, a waste heat recovery unit and a PTA mother liquor heat recovery unit. The multi-effect evaporation unit adopts four-effect evaporators which are connected in series to realize reverse step-by-step evaporation and concentration of wastewater; the waste heat recovery unit recovers system waste heat through a parallel heat exchanger and a series hot water flash tank and provides heat for an evaporator. And the PTA mother liquor heat recovery unit releases heat step by step through a mother liquor flash tank and supplies the heat to the evaporator. The wastewater enters a front crystallizer for crystallization after being evaporated and concentrated, and residues are fed into an alkali incinerator for treatment. Through multi-effect evaporation and waste heat gradient utilization, energy consumption is remarkably reduced, extra steam is not needed, waste heat can be used for power generation, and the device has the advantages of being efficient, capable of saving energy and low in material consumption and is suitable for large-scale treatment of PTA waste water.

Description

Technical Field

[0001] This utility model relates to the field of PTA production technology, and more specifically, to a highly efficient and energy-saving PTA wastewater treatment device. Background Technology

[0002] Terephthalic acid (PTA) is an important raw material for the production of polyester (PET) fibers and resins. Currently, the mainstream PTA wastewater treatment solution is the biological treatment method: a high-efficiency anaerobic + two-stage aerobic treatment process, which consists of a pretreatment system, an anaerobic biological system (IC), a biogas recovery system, a two-stage aerobic biological treatment system, a post-treatment and discharge system, a sludge treatment system, and a chemical reagent and nutrient dosing system. After being treated to meet the standards at the wastewater treatment plant, it is discharged into the environment.

[0003] Existing wastewater treatment processes all adopt end-of-pipe treatment and passive treatment approaches. Although they can meet discharge requirements, these devices occupy a large area, consume a lot of energy and materials, generate a large amount of sludge that needs to be treated separately, and the treated water needs to be discharged externally. They fail to meet the requirements for wastewater reduction and are far from meeting the requirements for zero discharge.

[0004] Chinese Patent Publication No. CN211111110U, published on July 28, 2020, entitled "An Invention for PTA Wastewater Treatment Device". This application discloses a PTA wastewater treatment device that adopts the concept of end-of-pipe treatment and passive treatment. Although it can achieve stable and continuous treatment and low pollution emission indicators, it has high energy and material consumption during the treatment process. Utility Model Content

[0005] This invention overcomes the shortcomings of existing technologies in treating PTA wastewater, which have high energy and material consumption. It provides a highly efficient and energy-saving PTA wastewater treatment device that can use the waste heat recovered by the heat recovery device to treat PTA wastewater without consuming fresh steam. This significantly reduces the energy consumption of the entire device, giving it the advantages of low energy and low material consumption.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: 1. A high-efficiency and energy-saving PTA wastewater treatment device, comprising:

[0007] The multi-effect evaporation unit includes several evaporators; PTA wastewater enters the several evaporators sequentially for evaporation.

[0008] The waste heat recovery unit includes several heat exchangers connected in parallel and several hot water flash tanks, with the hot water flash tanks providing heat to the several evaporators.

[0009] The PTA mother liquor heat recovery unit includes a mother liquor flash tank that provides heat to several evaporators.

[0010] This invention utilizes a multi-effect evaporator to treat PTA wastewater. The required heat is provided by a waste heat recovery unit and a PTA mother liquor heat recovery unit, thus treating PTA wastewater efficiently and with low energy consumption. It does not require the consumption of fresh steam, thereby significantly reducing the energy consumption of the entire device and has the advantages of low energy consumption and low material consumption.

[0011] Preferably, the multi-effect evaporation unit includes:

[0012] Single-effect evaporator;

[0013] In a double-effect evaporator, the top steam from the first-effect evaporator enters the second-effect evaporator.

[0014] In a triple-effect evaporator, the top steam from the double-effect evaporator enters the triple-effect evaporator.

[0015] The steam from the top of the triple-effect evaporator enters the quadruple-effect evaporator.

[0016] The first-effect evaporator, second-effect evaporator, third-effect evaporator and fourth-effect evaporator are connected in sequence. The steam generated by the internal evaporation provides the heat required for the evaporation of the next stage evaporator, thereby improving the energy utilization rate.

[0017] Preferably, the PTA wastewater enters from the side wall of the four-effect evaporator and flows out from the bottom of the four-effect evaporator;

[0018] It then enters from the side wall of the triple-effect evaporator and flows out from the bottom of the triple-effect evaporator;

[0019] It then enters from the side wall of the second-effect evaporator and flows out from the bottom of the second-effect evaporator;

[0020] It then enters from the side wall of the first-effect evaporator and flows out from the bottom of the first-effect evaporator.

[0021] The flow direction of PTA wastewater is opposite to the flow direction of steam in the first-effect, second-effect, third-effect, and fourth-effect evaporators, thereby gradually improving the evaporation efficiency of PTA wastewater and increasing its concentration, which facilitates subsequent improvement in crystallization efficiency.

[0022] Preferably, several hot water flash tanks include:

[0023] The bottom outlet of the hot water primary flash tank is connected to the side wall inlet of the hot water secondary flash tank; the steam at the top of the hot water primary flash tank enters the first-effect evaporator and then flows back into the hot water primary flash tank.

[0024] The bottom outlet of the hot water secondary flash tank is connected to the side wall inlet of the hot water tertiary flash tank; the steam at the top of the hot water secondary flash tank enters the double-effect evaporator and then flows back into the hot water secondary flash tank.

[0025] The bottom outlet of the hot water three-stage flash tank is connected to the side wall inlet of the hot water four-stage flash tank; the steam at the top of the hot water three-stage flash tank enters the triple-effect evaporator and then flows back into the hot water three-stage flash tank.

[0026] The bottom outlet of the hot water four-stage flash tank is connected to the hot water buffer tank; the top steam of the hot water four-stage flash tank enters the four-effect evaporator and then flows back to the hot water four-stage flash tank.

[0027] The water in the hot water buffer tank then enters the hot water cooler, and then flows into several parallel heat exchangers to absorb heat, repeating the above cycle. In other words, the waste heat recovery unit in this embodiment can recover and utilize the preheating of each part, improve the evaporation efficiency of the evaporator, and thus improve the treatment efficiency of PTA wastewater.

[0028] Preferably, the heat exchangers connected in parallel include an oxidation reactor tail gas heat exchanger, a post-oxidation reactor tail gas heat exchanger, and a crystallizer gas phase heat exchanger.

[0029] The aforementioned parallel heat exchangers, together with the gas phase heat exchanger of the PTA atmospheric stripping tower, generate high-temperature hot water, which then sequentially enters several hot water flash tanks for flash evaporation.

[0030] Preferably, the PTA mother liquor heat recovery unit includes:

[0031] The top steam of the mother liquor flash tank enters the first-effect evaporator and then enters the PTA unit's reuse tank.

[0032] The top steam of the mother liquor secondary flash tank enters the double-effect evaporator and then enters the PTA unit recycling tank; the bottom outlet of the mother liquor primary flash tank is connected to the side wall of the mother liquor secondary flash tank.

[0033] The top steam of the mother liquor three-stage flash tank enters the triple-effect evaporator and then enters the PTA unit recycling tank; the bottom outlet of the mother liquor two-stage flash tank is connected to the side wall of the mother liquor three-stage flash tank.

[0034] The top steam of the mother liquor four-stage flash tank enters the four-effect evaporator and then enters the PTA unit recycling tank; the bottom outlet of the mother liquor three-stage flash tank is connected to the side wall of the mother liquor four-stage flash tank.

[0035] The bottom outlet of the fourth-stage flash evaporator for mother liquor is connected to the PTA cryogenic mother liquor tank.

[0036] In this embodiment, the PTA mother liquor undergoes flash evaporation sequentially in a primary flash tank, a secondary flash tank, a tertiary flash tank, and a quaternary flash tank, utilizing the heat within the PTA mother liquor at each stage. Simultaneously, the steam generated in each flash tank provides heat for the corresponding evaporator, improving evaporation efficiency. After providing heat, the steam entering the evaporator is collected in the PTA unit's recycling tank, achieving the step-by-step utilization of PTA mother liquor energy. The bottom outlet of the quaternary flash tank is connected to a low-temperature PTA mother liquor tank, which collects the final PTA low-temperature mother liquor flowing out from the bottom outlet of the quaternary flash tank.

[0037] As a preferred option, it also includes a furnace-front first-effect crystallizer and a furnace-front second-effect crystallizer. PTA wastewater enters several evaporators in sequence for evaporation and then enters the furnace-front first-effect crystallizer and the furnace-front second-effect crystallizer in sequence for evaporation and crystallization.

[0038] Specifically, after the PTA wastewater flows out from the bottom of the first-effect evaporator, it enters the first-effect crystallizer in front of the furnace for evaporation and crystallization. After crystallizing in the first-effect crystallizer in front of the furnace, the PTA wastewater enters the second-effect crystallizer in front of the furnace from the bottom of the first-effect crystallizer in front of the furnace for crystallization.

[0039] Preferably, the top steam of the mother liquor primary flash tank enters the furnace front first-effect crystallizer and then flows back to the mother liquor primary flash tank; the top steam in the furnace front first-effect crystallizer enters the furnace front second-effect crystallizer.

[0040] The mother liquor flash evaporator can provide the energy required for crystallization to the furnace-front first-effect crystallizer.

[0041] Preferably, the bottom of the double-effect crystallizer is connected to the alkali incinerator, and the alkali incinerator is connected to the ash dissolving tank.

[0042] The PTA wastewater in the pre-furnace double-effect crystallizer evaporates and crystallizes in the pre-furnace double-effect crystallizer, and then enters the alkali incinerator for combustion. After that, it enters the ash dissolution tank to facilitate further crystallization and purification treatment.

[0043] As a preferred embodiment, it also includes a stripping tower evaporator and a stripping tower; after the PTA wastewater enters the stripping tower evaporator for evaporation, it enters the triple-effect evaporator, the double-effect evaporator and the first-effect evaporator in sequence for evaporation; the steam at the top of the stripping tower enters the stripping tower evaporator and then flows back into the stripping tower.

[0044] The above structure can further utilize the heat in the PTA wastewater and the heat of the steam at the top of the quadruple-effect evaporator to improve the treatment efficiency of PTA wastewater.

[0045] Compared with the prior art, the beneficial effects of this utility model are: using a multi-effect evaporator to treat PTA wastewater, the required heat is provided by the waste heat recovery unit and the PTA mother liquor heat recovery unit, thus treating PTA wastewater efficiently and with low energy consumption. It does not require the consumption of fresh steam, and the excess waste heat can also be used for power generation, thereby significantly reducing the energy consumption of the entire device. It has the advantages of low energy consumption and low material consumption. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the present invention.

[0047] Figure 2 This is a simplified schematic diagram of the waste heat recovery unit of this utility model.

[0048] In the diagram: 01 First-effect evaporator, 02 Second-effect evaporator, 03 Third-effect evaporator, 04 Fourth-effect evaporator, 05 Intercooler, 06 Product water tank, 07 Vacuum system, 08 Stripping tower, 09 Stripping tower evaporator;

[0049] 11. Furnace-front single-effect crystallizer, 12. Furnace-front double-effect crystallizer, 13. Furnace-front intercooler, 14. Furnace-front vacuum system, 15. Alkali incinerator, 16. Ash and slag dissolving tank.

[0050] Mother liquor primary flash tank 22, mother liquor secondary flash tank 23, mother liquor tertiary flash tank 24, mother liquor quaternary flash tank 25; primary hot water flash tank 26, secondary hot water flash tank 27, tertiary hot water flash tank 28, quaternary hot water flash tank 29.

[0051] Hot water buffer tank 30, hot water cooler 31, tail gas heat exchanger of oxidation reactor 32, tail gas heat exchanger of post-oxidation reactor 33, vapor phase heat exchanger of crystallizer 34, washing liquid heat exchanger of dryer washing tower 35, waste heat boiler wastewater heat exchanger 36, and vapor phase heat exchanger of atmospheric stripping tower 37. Detailed Implementation

[0052] The technical solution of this utility model will be further described in detail below through specific embodiments and with reference to the accompanying drawings:

[0053] Example 1: Refer to Figure 1 and Figure 2 As shown, a high-efficiency and energy-saving PTA wastewater treatment device includes: a multi-effect evaporation unit, a waste heat recovery unit, and a PTA mother liquor heat recovery unit.

[0054] The multi-effect evaporation unit consists of several evaporators that utilize heat in stages; PTA wastewater enters several evaporators sequentially for evaporation.

[0055] The waste heat recovery unit includes several heat exchangers connected in parallel and several hot water flash tanks connected in series with the several heat exchangers connected in parallel. The several hot water flash tanks provide heat to the several evaporators.

[0056] The PTA mother liquor heat recovery unit includes a corresponding mother liquor flash tank that provides heat to several evaporators.

[0057] In one embodiment, the multi-effect evaporation unit includes: a first-effect evaporator 01, a second-effect evaporator 02, a third-effect evaporator 03, and a fourth-effect evaporator 04.

[0058] The top steam of the first-effect evaporator 01 enters the second-effect evaporator 02, providing the heat required for evaporation in the second-effect evaporator 02.

[0059] The top steam of the second-effect evaporator 02 enters the third-effect evaporator 03, providing the heat required for evaporation in the third-effect evaporator 03.

[0060] The top steam of the triple-effect evaporator 03 enters the quadruple-effect evaporator 04, providing the heat required for evaporation within the quadruple-effect evaporator 04.

[0061] In this embodiment, the first-effect evaporator 01, the second-effect evaporator 02, the third-effect evaporator 03, and the fourth-effect evaporator 04 are connected in sequence. The steam generated by the internal evaporation provides the heat required for the evaporation of the next stage evaporator, improving energy utilization. The steam at the top of the fourth-effect evaporator 04 enters the intercooler 05, and then a portion of the steam in the intercooler 05 enters the product water tank 06, and finally enters the stripping tower 08. After the heat is utilized by the stripping tower 08, the steam enters the greywater recycling system for reuse. The remaining steam in the intercooler 05 enters the vacuum system 07.

[0062] Evaporator 01 (first effect), evaporator 02 (second effect), evaporator 03 (third effect), and evaporator 04 (fourth effect) are used for staged evaporation and concentration of PTA wastewater. The flow direction of the PTA wastewater is opposite to the flow direction of the steam in evaporators 01, 02, 03, and 04. Specifically:

[0063] PTA wastewater enters from the side wall of the four-effect evaporator 04 and flows out from the bottom of the four-effect evaporator 04.

[0064] It then enters from the side wall of the triple-effect evaporator 03 and flows out from the bottom of the triple-effect evaporator 03;

[0065] It then enters from the side wall of the second-effect evaporator 02 and flows out from the bottom of the second-effect evaporator 02;

[0066] It then enters from the side wall of the first-effect evaporator 01 and flows out from the bottom of the first-effect evaporator 01.

[0067] The flow direction of PTA wastewater is opposite to the flow direction of steam in the first-effect evaporator 01, second-effect evaporator 02, third-effect evaporator 03, and fourth-effect evaporator 04, thereby gradually improving the evaporation efficiency of PTA wastewater and increasing the concentration of PTA wastewater, which facilitates subsequent improvement in crystallization efficiency.

[0068] After the PTA wastewater flows out from the bottom of the first-effect evaporator 01, it enters the pre-furnace double-effect evaporation and crystallization unit for evaporation and crystallization. Specifically, the pre-furnace double-effect evaporation and crystallization unit includes a pre-furnace first-effect crystallizer 11 and a pre-furnace second-effect crystallizer 12.

[0069] PTA wastewater sequentially enters several evaporators for evaporation, and then sequentially enters the furnace-front first-effect crystallizer 11 and the furnace-front second-effect crystallizer 12 for further evaporation and crystallization. Specifically, after flowing out from the bottom of the first-effect evaporator 01, the PTA wastewater enters the furnace-front first-effect crystallizer 11 for evaporation and crystallization. After crystallizing in the furnace-front first-effect crystallizer 11, the PTA wastewater then enters the furnace-front second-effect crystallizer 12 from the bottom of the furnace-front first-effect crystallizer 11 for further crystallization.

[0070] The bottom of the pre-furnace double-effect crystallizer 12 is connected to the alkali incinerator 15, and the alkali incinerator 15 is connected to the ash dissolving tank 16. The PTA wastewater in the pre-furnace double-effect crystallizer 12 evaporates and crystallizes in the pre-furnace double-effect crystallizer 12, then enters the alkali incinerator 15 for combustion, and then enters the ash dissolving tank 16.

[0071] Steam from the top of the furnace-front double-effect crystallizer 12 enters the furnace-front intercooler 13, and then enters the furnace-front vacuum system 14.

[0072] In one embodiment, the PTA mother liquor heat recovery unit is used to recover heat from the PTA mother liquor. The PTA mother liquor heat recovery unit includes: a primary flash evaporator 22, a secondary flash evaporator 23, a tertiary flash evaporator 24, and a quaternary flash evaporator 25.

[0073] After the top steam of the mother liquor flash tank 22 enters the first-effect evaporator 01, it provides heat to the first-effect evaporator 01 for evaporation, and then enters the PTA unit recycling tank.

[0074] The bottom outlet of the primary flash evaporator 22 is connected to the side wall of the secondary flash evaporator 23, allowing the liquid in the primary flash evaporator 22 to enter the secondary flash evaporator 23 for flash evaporation. The steam generated by flash evaporation in the secondary flash evaporator 23 enters the double-effect evaporator 02 from the top, providing heat to the double-effect evaporator 02 for evaporation, and then enters the PTA unit's recycling tank.

[0075] The bottom outlet of the secondary flash evaporator 23 is connected to the side wall of the tertiary flash evaporator 24, allowing the liquid in the secondary flash evaporator 23 to enter the tertiary flash evaporator 24 for flash evaporation. The steam generated by flash evaporation in the tertiary flash evaporator 24 enters the triple-effect evaporator 03 from the top, providing heat to the triple-effect evaporator 03 for evaporation, and then enters the PTA unit's recycling tank.

[0076] The bottom outlet of the mother liquor three-stage flash evaporator 24 is connected to the side wall of the mother liquor four-stage flash evaporator 25, allowing the liquid in the mother liquor three-stage flash evaporator 24 to enter the mother liquor four-stage flash evaporator 25 for flash evaporation. The steam generated by flash evaporation in the mother liquor four-stage flash evaporator 25 enters the quadruple-effect evaporator 04 from the top, providing heat to the quadruple-effect evaporator 04 for evaporation, and then enters the PTA unit's recycling tank.

[0077] In other words, in this embodiment, the PTA mother liquor undergoes flash evaporation sequentially in a primary flash evaporator 22, a secondary flash evaporator 23, a tertiary flash evaporator 24, and a quaternary flash evaporator 25, utilizing the heat within the PTA mother liquor stage by stage. Simultaneously, the steam generated in each flash evaporator provides heat for the corresponding evaporator, improving the evaporation efficiency within the evaporator. After providing heat, the steam entering the evaporator is collected and stored in the PTA unit's recycling tank, achieving the staged utilization of PTA mother liquor energy. The bottom outlet of the quaternary flash evaporator 25 is connected to a low-temperature PTA mother liquor tank, which collects the final PTA low-temperature mother liquor flowing out from the bottom outlet of the quaternary flash evaporator 25.

[0078] In one embodiment, a plurality of parallel heat exchangers include: an oxidation reactor tail gas heat exchanger 32, a post-oxidation reactor tail gas heat exchanger 33, a crystallizer vapor phase heat exchanger 34, a dryer scrubbing tower washing liquid heat exchanger 35, and a waste heat boiler wastewater heat exchanger 36. These parallel heat exchangers, together with the PTA atmospheric stripping tower vapor phase heat exchanger 37, generate high-temperature hot water, which then sequentially enters a plurality of hot water flash tanks for flash evaporation.

[0079] In this embodiment, the plurality of hot water flash tanks include: a primary hot water flash tank 26, a secondary hot water flash tank 27, a tertiary hot water flash tank 28, and a quaternary hot water flash tank 29.

[0080] The bottom outlet of the primary flash tank 26 is connected to the side wall inlet of the secondary flash tank 27, allowing the hot water in the primary flash tank 26 to enter the secondary flash tank 27 for flash evaporation. The steam at the top of the primary flash tank 26 enters the first-effect evaporator 01, providing the heat required for evaporation, and then flows back to the primary flash tank 26.

[0081] The bottom outlet of the second-stage flash evaporator 27 is connected to the side wall inlet of the third-stage flash evaporator 28, allowing the hot water in the second-stage flash evaporator 27 to enter the third-stage flash evaporator 28 for flash evaporation. The steam from the top of the second-stage flash evaporator 27 enters the double-effect evaporator 02, providing the heat required for evaporation, and then flows back into the second-stage flash evaporator 27.

[0082] The bottom outlet of the three-stage flash evaporator 28 is connected to the side wall inlet of the four-stage flash evaporator 29, allowing the hot water in the three-stage flash evaporator 28 to enter the four-stage flash evaporator 29 for flash evaporation. The steam at the top of the three-stage flash evaporator 28 enters the triple-effect evaporator 03, providing the heat required for evaporation, and then flows back into the three-stage flash evaporator 28.

[0083] The bottom outlet of the four-stage flash evaporator 29 is connected to the hot water buffer tank 30, allowing the hot water in the four-stage flash evaporator 29 to enter the hot water buffer tank 30. The steam from the top of the four-stage flash evaporator 29 enters the quadruple-effect evaporator 04, providing the heat required for evaporation in the quadruple-effect evaporator 04, and then flows back to the four-stage flash evaporator 29.

[0084] The water in the hot water buffer tank 30 then enters the hot water cooler 31, and then flows into several parallel heat exchangers to absorb heat, repeating the above cycle. In other words, the waste heat recovery unit in this embodiment can recover and utilize the preheating of each part, improve the evaporation efficiency of the evaporator, and thus improve the treatment efficiency of PTA wastewater.

[0085] In this application, a multi-effect evaporator is used to treat PTA wastewater. The required heat is provided by the waste heat recovery unit and the PTA mother liquor heat recovery unit, thereby treating PTA wastewater efficiently and with low energy consumption. No fresh steam is required, and the excess waste heat can be used for power generation, which can significantly reduce the energy consumption of the entire device and has the advantages of low energy consumption and low material consumption.

[0086] Example 2: Refer to Figure 1 and Figure 2 As shown, a high-efficiency and energy-saving PTA wastewater treatment device includes: a multi-effect evaporation unit, a waste heat recovery unit, and a PTA mother liquor heat recovery unit.

[0087] The multi-effect evaporation unit consists of several evaporators that utilize heat in stages; PTA wastewater enters several evaporators sequentially for evaporation.

[0088] The waste heat recovery unit includes several heat exchangers connected in parallel and several hot water flash tanks connected in series with the several heat exchangers connected in parallel. The several hot water flash tanks provide heat to the several evaporators.

[0089] The PTA mother liquor heat recovery unit includes a corresponding mother liquor flash tank that provides heat to several evaporators.

[0090] In one embodiment, the multi-effect evaporation unit includes: a first-effect evaporator 01, a second-effect evaporator 02, a third-effect evaporator 03, and a fourth-effect evaporator 04.

[0091] The top steam of the first-effect evaporator 01 enters the second-effect evaporator 02, providing the heat required for evaporation in the second-effect evaporator 02.

[0092] The top steam of the second-effect evaporator 02 enters the third-effect evaporator 03, providing the heat required for evaporation in the third-effect evaporator 03.

[0093] The top steam of the triple-effect evaporator 03 enters the quadruple-effect evaporator 04, providing the heat required for evaporation within the quadruple-effect evaporator 04.

[0094] In this embodiment, the first-effect evaporator 01, the second-effect evaporator 02, the third-effect evaporator 03, and the fourth-effect evaporator 04 are connected in sequence. The steam generated by the internal evaporation provides the heat required for the evaporation of the next stage evaporator, improving energy utilization. The steam at the top of the fourth-effect evaporator 04 enters the intercooler 05, and then a portion of the steam in the intercooler 05 enters the product water tank 06, and finally enters the stripping tower 08. After the heat is utilized by the stripping tower 08, the steam enters the greywater recycling system for reuse. The remaining steam in the intercooler 05 enters the vacuum system 07.

[0095] Evaporator 01 (first effect), evaporator 02 (second effect), evaporator 03 (third effect), and evaporator 04 (fourth effect) are used for staged evaporation and concentration of PTA wastewater. The flow direction of the PTA wastewater is opposite to the flow direction of the steam in evaporators 01, 02, 03, and 04. Specifically:

[0096] PTA wastewater enters from the side wall of the four-effect evaporator 04 and flows out from the bottom of the four-effect evaporator 04.

[0097] It then enters from the side wall of the triple-effect evaporator 03 and flows out from the bottom of the triple-effect evaporator 03;

[0098] It then enters from the side wall of the second-effect evaporator 02 and flows out from the bottom of the second-effect evaporator 02;

[0099] It then enters from the side wall of the first-effect evaporator 01 and flows out from the bottom of the first-effect evaporator 01.

[0100] The flow direction of PTA wastewater is opposite to the flow direction of steam in the first-effect evaporator 01, second-effect evaporator 02, third-effect evaporator 03, and fourth-effect evaporator 04, thereby gradually improving the evaporation efficiency of PTA wastewater and increasing the concentration of PTA wastewater, which facilitates subsequent improvement in crystallization efficiency.

[0101] After the PTA wastewater flows out from the bottom of the first-effect evaporator 01, it enters the pre-furnace double-effect evaporation and crystallization unit for evaporation and crystallization. Specifically, the pre-furnace double-effect evaporation and crystallization unit includes a pre-furnace first-effect crystallizer 11 and a pre-furnace second-effect crystallizer 12.

[0102] PTA wastewater sequentially enters several evaporators for evaporation, and then sequentially enters the furnace-front first-effect crystallizer 11 and the furnace-front second-effect crystallizer 12 for further evaporation and crystallization. Specifically, after flowing out from the bottom of the first-effect evaporator 01, the PTA wastewater enters the furnace-front first-effect crystallizer 11 for evaporation and crystallization. After crystallizing in the furnace-front first-effect crystallizer 11, the PTA wastewater then enters the furnace-front second-effect crystallizer 12 from the bottom of the furnace-front first-effect crystallizer 11 for further crystallization.

[0103] The bottom of the pre-furnace double-effect crystallizer 12 is connected to the alkali incinerator 15, and the alkali incinerator 15 is connected to the ash dissolving tank 16. The PTA wastewater in the pre-furnace double-effect crystallizer 12 evaporates and crystallizes in the pre-furnace double-effect crystallizer 12, then enters the alkali incinerator 15 for combustion, and then enters the ash dissolving tank 16.

[0104] Steam from the top of the furnace-front double-effect crystallizer 12 enters the furnace-front intercooler 13, and then enters the furnace-front vacuum system 14.

[0105] In one embodiment, the PTA mother liquor heat recovery unit is used to recover heat from the PTA mother liquor. The PTA mother liquor heat recovery unit includes: a primary flash evaporator 22, a secondary flash evaporator 23, a tertiary flash evaporator 24, and a quaternary flash evaporator 25.

[0106] After the top steam of the mother liquor flash tank 22 enters the first-effect evaporator 01, it provides heat to the first-effect evaporator 01 for evaporation, and then enters the PTA unit recycling tank.

[0107] The bottom outlet of the primary flash evaporator 22 is connected to the side wall of the secondary flash evaporator 23, allowing the liquid in the primary flash evaporator 22 to enter the secondary flash evaporator 23 for flash evaporation. The steam generated by flash evaporation in the secondary flash evaporator 23 enters the double-effect evaporator 02 from the top, providing heat to the double-effect evaporator 02 for evaporation, and then enters the PTA unit's recycling tank.

[0108] The bottom outlet of the secondary flash evaporator 23 is connected to the side wall of the tertiary flash evaporator 24, allowing the liquid in the secondary flash evaporator 23 to enter the tertiary flash evaporator 24 for flash evaporation. The steam generated by flash evaporation in the tertiary flash evaporator 24 enters the triple-effect evaporator 03 from the top, providing heat to the triple-effect evaporator 03 for evaporation, and then enters the PTA unit's recycling tank.

[0109] The bottom outlet of the mother liquor three-stage flash evaporator 24 is connected to the side wall of the mother liquor four-stage flash evaporator 25, allowing the liquid in the mother liquor three-stage flash evaporator 24 to enter the mother liquor four-stage flash evaporator 25 for flash evaporation. The steam generated by flash evaporation in the mother liquor four-stage flash evaporator 25 enters the quadruple-effect evaporator 04 from the top, providing heat to the quadruple-effect evaporator 04 for evaporation, and then enters the PTA unit's recycling tank.

[0110] In other words, in this embodiment, the PTA mother liquor undergoes flash evaporation sequentially in a primary flash evaporator 22, a secondary flash evaporator 23, a tertiary flash evaporator 24, and a quaternary flash evaporator 25, utilizing the heat within the PTA mother liquor stage by stage. Simultaneously, the steam generated in each flash evaporator provides heat for the corresponding evaporator, improving the evaporation efficiency within the evaporator. After providing heat, the steam entering the evaporator is collected and stored in the PTA unit's recycling tank, achieving the staged utilization of PTA mother liquor energy. The bottom outlet of the quaternary flash evaporator 25 is connected to a low-temperature PTA mother liquor tank, which collects the final PTA low-temperature mother liquor flowing out from the bottom outlet of the quaternary flash evaporator 25.

[0111] In one embodiment, a plurality of parallel heat exchangers include: an oxidation reactor tail gas heat exchanger 32, a post-oxidation reactor tail gas heat exchanger 33, a crystallizer vapor phase heat exchanger 34, a dryer scrubbing tower washing liquid heat exchanger 35, and a waste heat boiler wastewater heat exchanger 36. These parallel heat exchangers, together with the PTA atmospheric stripping tower vapor phase heat exchanger 37, generate high-temperature hot water, which then sequentially enters a plurality of hot water flash tanks for flash evaporation.

[0112] In this embodiment, the plurality of hot water flash tanks include: a primary hot water flash tank 26, a secondary hot water flash tank 27, a tertiary hot water flash tank 28, and a quaternary hot water flash tank 29.

[0113] The bottom outlet of the primary flash tank 26 is connected to the side wall inlet of the secondary flash tank 27, allowing the hot water in the primary flash tank 26 to enter the secondary flash tank 27 for flash evaporation. The steam at the top of the primary flash tank 26 enters the first-effect evaporator 01, providing the heat required for evaporation, and then flows back to the primary flash tank 26.

[0114] The bottom outlet of the second-stage flash evaporator 27 is connected to the side wall inlet of the third-stage flash evaporator 28, allowing the hot water in the second-stage flash evaporator 27 to enter the third-stage flash evaporator 28 for flash evaporation. The steam from the top of the second-stage flash evaporator 27 enters the double-effect evaporator 02, providing the heat required for evaporation, and then flows back into the second-stage flash evaporator 27.

[0115] The bottom outlet of the three-stage flash evaporator 28 is connected to the side wall inlet of the four-stage flash evaporator 29, allowing the hot water in the three-stage flash evaporator 28 to enter the four-stage flash evaporator 29 for flash evaporation. The steam at the top of the three-stage flash evaporator 28 enters the triple-effect evaporator 03, providing the heat required for evaporation, and then flows back into the three-stage flash evaporator 28.

[0116] The bottom outlet of the four-stage flash evaporator 29 is connected to the hot water buffer tank 30, allowing the hot water in the four-stage flash evaporator 29 to enter the hot water buffer tank 30. The steam from the top of the four-stage flash evaporator 29 enters the quadruple-effect evaporator 04, providing the heat required for evaporation in the quadruple-effect evaporator 04, and then flows back to the four-stage flash evaporator 29.

[0117] The water in the hot water buffer tank 30 then enters the hot water cooler 31, and then flows into several parallel heat exchangers to absorb heat, repeating the above cycle. In other words, the waste heat recovery unit in this embodiment can recover and utilize the preheating of each part, improve the evaporation efficiency of the evaporator, and thus improve the treatment efficiency of PTA wastewater.

[0118] This embodiment is similar in structure to Embodiment 1, except that it also includes a stripping tower evaporator 09. A portion of the PTA wastewater enters the stripping tower evaporator 09 for evaporation. After evaporation, it sequentially enters the triple-effect evaporator 03, the double-effect evaporator 02, and the single-effect evaporator 01 for further evaporation. The steam evaporated from the PTA wastewater in the stripping tower 08 enters the intercooler 05, and together with the steam evaporated from the quadruple-effect evaporator 04, it enters the intercooler 05, then the product water tank 06, and finally enters the stripping tower 08.

[0119] Water entering the stripping tower 08 from the product water tank 06 generates steam, which then enters the stripping tower evaporator 09 from the top outlet of the stripping tower 08, providing the heat required for the stripping tower evaporator 09 to evaporate PTA wastewater.

[0120] Therefore, in this embodiment, the heat in the PTA wastewater and the heat of the steam at the top of the four-effect evaporator 04 can be further utilized to improve the treatment efficiency of PTA wastewater.

[0121] This application utilizes a multi-effect evaporator to treat PTA wastewater. The required heat is provided by a waste heat recovery unit and a PTA mother liquor heat recovery unit, thus achieving efficient and low-energy wastewater treatment. No fresh steam is required, and excess waste heat can be used for power generation, significantly reducing the overall energy consumption of the device. This results in advantages of low energy and low material consumption. Furthermore, this embodiment further utilizes the heat from the PTA wastewater and the heat from the steam at the top of the four-effect evaporator (04) to improve the PTA wastewater treatment efficiency.

[0122] The embodiments described above are merely preferred solutions of this utility model and are not intended to limit this utility model in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A highly efficient and energy-saving PTA wastewater treatment device, characterized in that, include: A multi-effect evaporation unit, comprising several evaporators; PTA wastewater sequentially enters several evaporators for evaporation; The waste heat recovery unit includes several heat exchangers connected in parallel and several hot water flash tanks, with the hot water flash tanks providing heat to the several evaporators. The PTA mother liquor heat recovery unit includes a mother liquor flash tank that provides heat to several evaporators.

2. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 1, characterized in that, The multi-effect evaporation unit includes: Single-effect evaporator; In a double-effect evaporator, the top steam from the first-effect evaporator enters the second-effect evaporator. In a triple-effect evaporator, the top steam from the double-effect evaporator enters the triple-effect evaporator. The steam from the top of the triple-effect evaporator enters the quadruple-effect evaporator.

3. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 2, characterized in that, PTA wastewater enters from the side wall of the quadruple-effect evaporator and flows out from the bottom of the quadruple-effect evaporator; It then enters from the side wall of the triple-effect evaporator and flows out from the bottom of the triple-effect evaporator; It then enters from the side wall of the second-effect evaporator and flows out from the bottom of the second-effect evaporator; It then enters from the side wall of the first-effect evaporator and flows out from the bottom of the first-effect evaporator.

4. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 2 or 3, characterized in that, Several hot water flash tanks include: The bottom outlet of the hot water primary flash tank is connected to the side wall inlet of the hot water secondary flash tank; the steam at the top of the hot water primary flash tank enters the first-effect evaporator and then flows back into the hot water primary flash tank. The bottom outlet of the hot water secondary flash tank is connected to the side wall inlet of the hot water tertiary flash tank; the steam at the top of the hot water secondary flash tank enters the double-effect evaporator and then flows back into the hot water secondary flash tank. The bottom outlet of the hot water three-stage flash tank is connected to the side wall inlet of the hot water four-stage flash tank; the steam at the top of the hot water three-stage flash tank enters the triple-effect evaporator and then flows back into the hot water three-stage flash tank. The bottom outlet of the hot water four-stage flash tank is connected to the hot water buffer tank; the top steam of the hot water four-stage flash tank enters the four-effect evaporator and then flows back to the hot water four-stage flash tank.

5. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 4, characterized in that, Several heat exchangers connected in parallel include an oxidation reactor tail gas heat exchanger, a post-oxidation reactor tail gas heat exchanger, and a crystallizer gas phase heat exchanger.

6. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 2 or 3, characterized in that, The PTA mother liquor heat recovery unit includes: The top steam of the mother liquor flash tank enters the first-effect evaporator and then enters the PTA unit's reuse tank. The top steam of the mother liquor secondary flash tank enters the double-effect evaporator and then enters the PTA unit recycling tank; the bottom outlet of the mother liquor primary flash tank is connected to the side wall of the mother liquor secondary flash tank. The top steam of the mother liquor three-stage flash tank enters the triple-effect evaporator and then enters the PTA unit recycling tank; the bottom outlet of the mother liquor two-stage flash tank is connected to the side wall of the mother liquor three-stage flash tank. The top steam of the mother liquor four-stage flash tank enters the four-effect evaporator and then enters the PTA unit recycling tank; the bottom outlet of the mother liquor three-stage flash tank is connected to the side wall of the mother liquor four-stage flash tank. The bottom outlet of the fourth-stage flash evaporator for mother liquor is connected to the PTA cryogenic mother liquor tank.

7. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 6, characterized in that, It also includes a furnace-front first-effect crystallizer and a furnace-front second-effect crystallizer. PTA wastewater enters several evaporators in sequence for evaporation and then enters the furnace-front first-effect crystallizer and the furnace-front second-effect crystallizer in sequence for evaporation and crystallization.

8. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 7, characterized in that, The top steam of the mother liquor flash tank enters the furnace front first-effect crystallizer and then flows back to the mother liquor flash tank; the top steam of the furnace front first-effect crystallizer enters the furnace front second-effect crystallizer.

9. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 8, characterized in that, The bottom of the double-effect crystallizer in front of the furnace is connected to the alkali incinerator, and the alkali incinerator is connected to the ash dissolving tank.

10. The high-efficiency and energy-saving PTA wastewater treatment device according to claim 2 or 3, characterized in that, It also includes a stripping tower evaporator and a stripping tower; after the PTA wastewater enters the stripping tower evaporator for evaporation, it enters the triple-effect evaporator, the double-effect evaporator and the first-effect evaporator in sequence for evaporation; the steam at the top of the stripping tower enters the stripping tower evaporator and then flows back into the stripping tower.

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