Exhaust gas waste heat utilization system and process for mixed acid waste liquid treatment system

Abstract

The present invention relates to the technical field of pickling waste liquid resource recycling and regeneration, and specifically relates to an exhaust gas waste heat utilization system and process for a mixed acid waste liquid treatment system. The mixed acid waste liquid treatment system is configured to treat mixed acid waste liquid and discharge high-temperature exhaust gas. The exhaust gas waste heat utilization system comprises a first heat exchanger, a second heat exchanger and a refrigeration mechanism, wherein a first heat exchange circulating water circuit is provided between the first heat exchanger and the refrigeration mechanism, and the first heat exchanger uses exhaust gas heat to provide a heat source for the refrigeration mechanism and reduces the water temperature of the first heat exchange circulating water circuit by means of the refrigeration mechanism; and a second heat exchange circulating water circuit is provided between the second heat exchanger and the refrigeration mechanism, and the second heat exchanger is further connected to circulating piping of the mixed acid waste liquid treatment system so as to reduce the temperature of a circulating liquid. By means of the exhaust gas waste heat utilization system, flue gas waste heat from the mixed acid waste liquid treatment system is effectively recovered, reducing energy waste; and the second heat exchanger reduces the temperature of the circulating liquid of the mixed acid waste liquid treatment system, thereby enhancing the oxidation efficiency of flue gas.

Description

Tail gas waste heat utilization system and process of mixed acid waste liquid treatment system TECHNICAL FIELD

[0001] The present application relates to the field of acid pickling waste liquid resource treatment and regeneration technology, in particular to a tail gas waste heat utilization system and process of mixed acid waste liquid treatment system. BACKGROUND

[0002] The pickling process in the metallurgical industry is an indispensable step in metal surface treatment, especially in the pretreatment of materials such as plates, rods and wires. This process improves the processing performance of metal materials, but also produces a large amount of pickling waste liquid. The waste acid and heavy metals contained in these waste liquids pose a serious threat to the environment and become a pollutant that metallurgical enterprises need to solve urgently.

[0003] These pickling waste liquids are classified as important substances in the national hazardous waste list because of the harmful substances they contain. In the prior art, there is a mixed acid waste liquid resource regeneration system that realizes the resource regeneration and utilization of mixed acid waste liquid through steps such as concentration, decomposition, acid absorption, oxidation and denitration. However, this treatment method discharges waste gas at a high temperature, which directly discharges into the air, causing a large amount of energy waste, so an effective heat utilization system is needed to recover and utilize the large amount of heat discharged from the mixed acid waste liquid resource regeneration system.

[0004] SUMMARY

[0005] The purpose of the present application is to provide a tail gas waste heat utilization system and process of mixed acid waste liquid treatment system to solve the problem of energy waste in the above-mentioned mixed acid waste liquid treatment process.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application includes: a tail gas waste heat utilization system of a mixed acid waste liquid treatment system, the mixed acid waste liquid treatment system is used for treating mixed acid waste liquid and discharging high-temperature tail gas, the tail gas waste heat utilization system includes a first heat exchanger, a second heat exchanger and a refrigeration mechanism, a first heat exchange circulating water path is provided between the first heat exchanger and the refrigeration mechanism, the first heat exchanger is also connected to the tail gas discharge end of the mixed acid waste liquid treatment system, so as to utilize the tail gas heat to provide a heat source for the refrigeration mechanism and reduce the water temperature of the first heat exchange circulating water path by means of the refrigeration mechanism; a second heat exchange circulating water path is provided between the second heat exchanger and the refrigeration mechanism, the water temperature of the second heat exchange circulating water path is reduced by means of the refrigeration mechanism, and the second heat exchanger is also connected to the circulating pipeline of the circulating liquid of the mixed acid waste liquid treatment system, so as to reduce the temperature of the circulating liquid.

[0007] In one embodiment, the first heat exchanger is provided with a first heat exchange water inlet and a first heat exchange water outlet, the first heat exchange water inlet is connected to the first refrigeration water outlet of the refrigeration mechanism, the first heat exchange water outlet is connected to the first refrigeration water inlet of the refrigeration mechanism, the first heat exchanger is used to heat the first low-temperature water from the refrigeration mechanism into first high-temperature water by the tail gas discharged from the mixed acid waste liquid treatment system, so as to provide a heat source for the refrigeration mechanism by using the heat of the tail gas, and the refrigeration mechanism uses the heat source to cool the first high-temperature water into the first low-temperature water, so as to reduce the water temperature of the first heat exchange circulating water path by means of the refrigeration mechanism.

[0008] In one embodiment, the second heat exchanger is provided with a second heat exchange water inlet and a second heat exchange water outlet, the second heat exchange water inlet is connected to the second refrigeration water outlet of the refrigeration mechanism, the second heat exchange water outlet is connected to the second refrigeration water inlet of the refrigeration mechanism, and the refrigeration mechanism reduces the water temperature of the second heat exchange circulating water path by cooling the second high-temperature water from the second heat exchanger into second low-temperature water.

[0009] In one embodiment, the refrigeration mechanism is a lithium bromide refrigeration mechanism, wherein the concentration of lithium bromide ranges from 40% to 60%.

[0010] In one embodiment, it further comprises a first water-driven pump group and a second water-driven pump group, the first water-driven pump group is used to realize water circulation and delivery of the first heat exchange circulating water path, and the second water-driven pump group is used to realize water circulation and delivery of the second heat exchange circulating water path.

[0011] In one embodiment, the mixed acid waste liquid treatment system comprises a decomposition furnace, a pre-concentration mechanism, an absorption mechanism, a cooling mechanism, an oxidation mechanism, a denitration mechanism, and a flue gas pipeline connecting the mechanisms, the circulating pipeline is connected with a cooler, the oxidation mechanism, and the second heat exchanger, the cooler is used to cool the circulating liquid from the oxidation mechanism for the first time, the second heat exchanger is used to cool the circulating liquid for the second time, and the circulating pipeline is further provided with a branch connected to the flue gas pipeline, and the second heat exchanger is used to provide the circulating liquid cooled for the second time to the oxidation mechanism or the oxidation mechanism and the flue gas pipeline.

[0012] The technical scheme of the present application further comprises: a tail gas waste heat utilization process of a mixed acid waste liquid treatment system, characterized in that: the process is based on the tail gas waste heat utilization system of the above-mentioned mixed acid waste liquid treatment system, and the process at least comprises two parts of tail gas waste heat recovery and circulating liquid cooling, wherein,

[0013] The step of tail gas waste heat recovery comprises:

[0014] a) introducing the tail gas into the first heat exchanger;

[0015] b) the refrigeration mechanism provides first low-temperature water to the first heat exchanger, and the first heat exchanger heats the first low-temperature water into first high-temperature water by using exhaust heat;

[0016] c) the first high-temperature water is supplied to the refrigeration mechanism to drive the refrigeration mechanism by using the heated first high-temperature water as a heat source;

[0017] d) the refrigeration mechanism cools down water in a first heat exchange circulating water path;

[0018] The step of cooling down the circulating liquid includes:

[0019] 1) the refrigeration mechanism supplies second low-temperature water to the second heat exchanger;

[0020] 2) in the second heat exchanger, the second low-temperature water exchanges heat with the circulating liquid to reduce the temperature of the circulating liquid, and the second low-temperature water is heated to form second high-temperature water;

[0021] 3) the second high-temperature water formed by heating the second low-temperature water is returned to the refrigeration mechanism, thereby forming a second heat exchange circulating water path between the second heat exchanger and the refrigeration mechanism.

[0022] In an embodiment, the temperature of the first low-temperature water is 70-85℃, and the temperature of the first high-temperature water is 90-105℃.

[0023] In an embodiment, the temperature of the second low-temperature water is 7-17℃, and the temperature of the second high-temperature water is 12-22℃.

[0024] In an embodiment, the temperature of the circulating liquid after passing through the second heat exchanger is 15-37℃.

[0025] Compared with the prior art, the present application has the following beneficial effects:

[0026] (1) By using the exhaust heat utilization system, the waste heat of the low-grade flue gas at the end of the mixed acid waste liquid treatment system is effectively recovered, and energy waste is reduced.

[0027] (2) By the heat exchange process of the second heat exchanger, the temperature of the circulating liquid in the mixed acid waste liquid treatment system is reduced, thereby improving the oxidation efficiency of nitrogen oxides in the flue gas in the mixed acid waste liquid treatment system, and realizing efficient regeneration and utilization of the waste acid liquid.

[0028] (3) The flue gas heat is effectively used as a heat source to promote the operation of the refrigeration mechanism, so that the refrigeration mechanism outputs low-temperature water, which reduces the temperature of the flue gas on one hand and reduces the temperature of the circulating liquid on the other hand, thereby realizing the recycling of heat and in turn using the heat to reduce the temperature of the circulating liquid and improve the oxidation efficiency, and realizing the effective circulation of heat.

[0029] (4) The multiple promotion of production efficiency, energy efficiency and economic efficiency is realized, and the application has high economic value. BRIEF DESCRIPTION OF DRAWINGS

[0030] Fig. 1 is a schematic diagram of the overall structure of an embodiment of the application.

[0031] Fig. 2 is a schematic diagram of part of the structure of an embodiment of the application.

[0032] Fig. 3 is a schematic diagram of part of the structure of another embodiment of the application. DETAILED DESCRIPTION

[0033] To further illustrate the embodiments, the application provides accompanying drawings. These drawings are part of the disclosure of the application, and are mainly used to illustrate the embodiments, and can be used to explain the operating principles of the embodiments in conjunction with the relevant descriptions in the specification. Those of ordinary skill in the art should be able to understand other possible implementations and advantages of the application in conjunction with these. The components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0034] Referring to Figs. 1 and 2, the application discloses a tail gas waste heat utilization system of a mixed acid waste liquid treatment system, the mixed acid waste liquid treatment system 10 is used for treating mixed acid waste liquid and discharging high-temperature tail gas, the tail gas waste heat utilization system 20 includes a first heat exchanger 21, a second heat exchanger 22 and a refrigeration mechanism 23, a first heat exchange circulating water path 201 is arranged between the first heat exchanger 21 and the refrigeration mechanism 23, the first heat exchanger 21 is also connected to a tail gas discharge end of the mixed acid waste liquid treatment system 10, so as to utilize the heat of the tail gas to provide a heat source for the refrigeration mechanism 23 and reduce the water temperature of the first heat exchange circulating water path 201 by means of the refrigeration mechanism 23. A second heat exchange circulating water path 202 is arranged between the second heat exchanger 22 and the refrigeration mechanism 23, the water temperature of the second heat exchange circulating water path 202 is reduced by means of the refrigeration mechanism 23, and the second heat exchanger 22 is also connected to a circulating pipeline of circulating liquid of the mixed acid waste liquid treatment system 10, so as to reduce the temperature of the circulating liquid.

[0035] The mixed acid waste liquid treatment system 10 comprises a decomposition furnace 11, a pre-concentration mechanism 12, an absorption mechanism 13, a cooling mechanism 14, an oxidation mechanism 15, a denitration mechanism 16 and flue gas pipelines connecting the mechanisms, so as to realize the resource recycling of the mixed acid waste liquid. In the mixed acid waste liquid treatment system 10, the mixed acid waste liquid is first concentrated by the pre-concentration mechanism 12, and then sprayed into the decomposition furnace 11 for decomposition. The hot flue gas generated in the decomposition process enters the pre-concentration mechanism 12 through the flue gas pipeline for cooling and dust removal. The cooled flue gas then enters the absorption mechanism 13 through the flue gas pipeline to realize the recovery of regenerated acid. The cooling mechanism 14 further reduces the temperature of the flue gas to provide conditions for the efficient operation of the oxidation mechanism 15. The oxidation mechanism 15 oxidizes nitrogen oxides in the flue gas to further improve the recovery rate of regenerated acid. The working temperature of the oxidation mechanism 15 has a greater impact on the oxidation efficiency. The lower the temperature, the higher the oxidation efficiency. Therefore, the mixed acid waste liquid treatment system 10 is provided with a circulating pipeline 101, and a cooler 17 in the circulating pipeline 101 is used to cool the circulating liquid, thereby reducing the working temperature of the oxidation mechanism 15. Finally, the denitration mechanism 16 denitrates the flue gas to ensure that the content of nitrogen oxides in the flue gas meets the emission standard. At the same time, the catalytic reaction during denitration may require heating of the flue gas, so that the temperature of the flue gas finally discharged from the mixed acid waste liquid treatment system 10 is relatively high. The mixed acid waste liquid treatment system 10 of the embodiment has a flue gas temperature of 180-250℃ at the tail gas discharge end, and the flue gas temperature is relatively high. If the flue gas is directly discharged into the air, there will be a large amount of heat loss, and the ambient temperature around the tail gas discharge port will be too high, which is not conducive to the heat dissipation of the mixed acid waste liquid treatment system 10.

[0036] The application reduces the temperature of the exhaust flue gas by setting the first heat exchanger 21, and the temperature of the flue gas is converted into the temperature of the first heat exchange circulating water path 201, and the heat is used as the heat source of the refrigeration mechanism 23, and then drives the refrigeration mechanism 23 to work, so that the heat is recycled and utilized, and the utilization rate of energy is improved, and the surrounding air can also be prevented from being excessively heated. Secondly, since the oxidation mechanism 15 of the mixed acid waste liquid treatment system 10 needs to be cooled during the working process, the second heat exchanger 22 is added to the circulating pipeline 101 of the circulating liquid, and the temperature of the circulating liquid of the mixed acid waste liquid treatment system 10 is reduced by the second heat exchange circulating water path 202 between the refrigeration mechanism 23 and the second heat exchanger 22, so as to improve the cooling effect of the oxidation mechanism 15, and then improve the oxidation efficiency. The water circulation between the first heat exchanger 21, the second heat exchanger 22 and the refrigeration mechanism 23 can not only reduce the temperature of the exhaust flue gas of the mixed acid waste liquid treatment system 10, but also reduce the influence of the flue gas temperature on the environment. Secondly, the flue gas temperature can also be used as the heat source of the refrigeration mechanism 23 to drive the refrigeration mechanism 23 to work, so as to realize the recycling and reuse of heat, improve the utilization rate of energy, and realize heat conversion by the refrigeration mechanism 23. Finally, the refrigeration mechanism 23 can reduce the water temperature of the first heat exchange circulating water path 201 and the second heat exchange circulating water path 202 by the heat of the exhaust gas, so as to provide low-temperature water for the first heat exchanger 21 and the second heat exchanger 22, and then utilize the low-temperature water to reduce the temperature of the flue gas and the circulating liquid, without inputting energy and fully utilizing heat conversion to optimize the treatment effect of the mixed acid waste liquid treatment system 10.

[0037] The first heat exchanger 21 is provided with a first heat exchange water inlet and a first heat exchange water outlet, the first heat exchange water inlet is connected to the first refrigeration water outlet of the refrigeration mechanism 23, the first heat exchange water outlet is connected to the first refrigeration water inlet of the refrigeration mechanism 23, and the first heat exchanger 21 is used to heat the first low-temperature water from the refrigeration mechanism 23 into first high-temperature water by the exhaust gas of the mixed acid waste liquid treatment system 10, so as to provide the heat source for the refrigeration mechanism 23 by the heat of the exhaust gas, and the refrigeration mechanism 23 reduces the first high-temperature water into the first low-temperature water by the heat source, so as to reduce the water temperature of the first heat exchange circulating water path 201 by the refrigeration mechanism 23.

[0038] The second heat exchanger 22 is provided with a second heat exchange water inlet and a second heat exchange water outlet, the second heat exchange water inlet is connected to the second refrigeration water outlet of the refrigeration mechanism 23, and the second heat exchange water outlet is connected to the second refrigeration water inlet of the refrigeration mechanism 23. The refrigeration mechanism 23 reduces the water temperature of the second heat exchange circulating water path 202 by reducing the second high-temperature water from the second heat exchanger 22 into the second low-temperature water.

[0039] The first heat exchanger 21 and the second heat exchanger 22 are respectively provided with independent heat exchange circulating water paths to exchange heat with the refrigeration mechanism 23, so as to reduce the water temperature of the respective heat exchange circulating water paths and provide water with different temperatures to the first heat exchanger 21 and the second heat exchanger 22 according to requirements.

[0040] The second heat exchanger 22 participates in the circulation of the circulating pipeline 101 of the mixed acid waste liquid treatment system 10, and the circulating liquid flows to the second heat exchanger 22 to be cooled for the second time, so that the second heat exchanger 22 provides the oxidizing mechanism 15 with the circulating liquid cooled for the second time, so that the temperature of the circulating liquid is further reduced, and the oxidizing mechanism 15 can work at a lower temperature, and the oxidation efficiency is improved. Each branch is provided with a valve to control the on-off and flow of the circulating liquid, and the part of the circulating liquid entering the flue gas pipeline is used for cooling the flue gas in the mixed acid waste liquid treatment system 10. The circulating liquid is branched before entering the second heat exchanger 22, so that the circulating liquid entering the second heat exchanger 22 is less, and the cooling effect of the second heat exchanger 22 on the part of the circulating liquid is more obvious. In another embodiment, the circulating liquid is branched after being cooled for the second time by the cooler 17 and the second heat exchanger 22, one branch enters the flue gas pipeline to cool the flue gas, and the other branch enters the oxidizing mechanism 15, so that the second heat exchanger supplies the flue gas pipeline and the oxidizing mechanism with the circulating liquid cooled for the second time. This design enables the circulating liquid to enter the flue gas pipeline at a lower temperature, and the cooling effect on the flue gas is more obvious.

[0041] The refrigeration mechanism 23 of the embodiment is a lithium bromide refrigeration mechanism, wherein the concentration of lithium bromide ranges from 40% to 60%, and the lithium bromide refrigeration mechanism reduces the water temperature of the first heat exchange circulating water path 201 and the second heat exchange circulating water path 202 by using the input heat source, so as to achieve the purpose of refrigeration. The working principle of the lithium bromide refrigeration mechanism is the prior art, and will not be described here.

[0042] As shown in FIG. 1, the first water-driven pump group is used to realize the water circulation and delivery of the first heat exchange circulating water path 201, and the second water-driven pump group is used to realize the water circulation and delivery of the second heat exchange circulating water path 202. The first water-driven pump group and the second water-driven pump group can ensure the normal circulation and delivery of the water in the first heat exchange circulating water path 201 and the second heat exchange circulating water path 202, so that the heat exchange is normally carried out, and the desired heat exchange effect is achieved.

[0043] The refrigeration mechanism 23 is also connected with a cooling water path 203, which is used to cool the refrigeration mechanism 23 to prevent the refrigeration mechanism 23 from being too high in temperature during operation. The first heat exchange circulating water path 201 and the second heat exchange circulating water path 202 are respectively provided with a water supplement path 204, so that the first heat exchange circulating water path 201 and the second heat exchange circulating water path 202 can have water for circulation when starting to work, and the water supplement path 204 can no longer supply water to the first heat exchange circulating water path 201 and the second heat exchange circulating water path 202 when the first heat exchange circulating water path 201 and the second heat exchange circulating water path 202 perform normal water circulation. In addition, the temperature of the water supplemented by the water supplement path 204 should match the water temperature of the corresponding heat exchange circulating water path, so as to ensure that the water temperature of the heat exchange circulating water path meets the requirements.

[0044] The application also discloses a tail gas waste heat utilization process of a mixed acid waste liquid treatment system, which is based on the tail gas waste heat utilization system of the mixed acid waste liquid treatment system, and at least includes two parts of tail gas waste heat recovery and circulating liquid cooling.

[0045] a) introducing the tail gas into the first heat exchanger 21;

[0046] b) the refrigeration mechanism 23 providing the first heat exchanger 21 with first low-temperature water, and the first heat exchanger 21 heating the first low-temperature water into first high-temperature water by using the heat of the tail gas;

[0047] c) the first high-temperature water being supplied to the refrigeration mechanism 23 to drive the refrigeration mechanism 23 by taking the heated first high-temperature water as a heat source;

[0048] d) the refrigeration mechanism 23 cooling the water of the first heat exchange circulating water path 201.

[0049] The step of circulating liquid cooling includes:

[0050] 1) the refrigeration mechanism 23 delivering second low-temperature water to the second heat exchanger 22;

[0051] 2) in the second heat exchanger 22, the second low-temperature water exchanges heat with the circulating liquid to reduce the temperature of the circulating liquid, and the second low-temperature water is increased in temperature to form second high-temperature water;

[0052] 3) the second high-temperature water formed by the second low-temperature water after being increased in temperature is returned to the refrigeration mechanism 23, so as to form the second heat exchange circulating water path 202 between the second heat exchanger 22 and the refrigeration mechanism 23.

[0053] The second heat exchanger 22 cools the circulating liquid by one of the embodiments shown in FIG. 2 or FIG. 3, and the two cooling modes are described in detail in the foregoing content, and will not be repeated here.

[0054] The temperature of the first low-temperature water is 70-85°C, and the present embodiment is further preferably 75-80°C. The temperature of the first high-temperature water is 90-105°C, and the present embodiment is further preferably 95-100°C.

[0055] The temperature of the second low-temperature water is 7-17°C, and the present embodiment is further preferably 7-12°C. The temperature of the second high-temperature water is 12-22°C, and the present embodiment is further preferably 12-18°C.

[0056] The temperature of the circulating liquid after passing through the second heat exchanger 22 is 15-37°C, and the present embodiment is further preferably 20-30°C. The flow rate of the circulating liquid is in the range of 60-160 m 3 / h.

[0057] Although the present application has been specifically shown and described with reference to preferred embodiments, it will be obvious that various changes in form and detail can be made therein without departing from the spirit and scope of the application as defined by the appended claims.

Claims

1. A tail gas waste heat utilization system of a mixed acid waste liquid treatment system, characterized by: The mixed acid waste liquid treatment system is used for treating mixed acid waste liquid and discharging high-temperature tail gas, and the tail gas waste heat utilization system comprises a first heat exchanger, a second heat exchanger and a refrigeration mechanism, a first heat exchange circulating water path is arranged between the first heat exchanger and the refrigeration mechanism, the first heat exchanger is further connected to a tail gas discharge end of the mixed acid waste liquid treatment system, so as to utilize tail gas heat to provide a heat source for the refrigeration mechanism and reduce the water temperature of the first heat exchange circulating water path by means of the refrigeration mechanism; a second heat exchange circulating water path is arranged between the second heat exchanger and the refrigeration mechanism, the water temperature of the second heat exchange circulating water path is reduced by means of the refrigeration mechanism, and the second heat exchanger is further connected to a circulating pipeline of circulating liquid of the mixed acid waste liquid treatment system, so as to reduce the temperature of the circulating liquid.

2. The tail gas waste heat utilization system of a mixed acid waste liquid treatment system according to claim 1, characterized in that: The first heat exchanger is provided with a first heat exchange water inlet and a first heat exchange water outlet, the first heat exchange water inlet is connected to a first refrigeration water outlet of the refrigeration mechanism, the first heat exchange water outlet is connected to a first refrigeration water inlet of the refrigeration mechanism, and the first heat exchanger is used for heating first low-temperature water from the refrigeration mechanism to first high-temperature water by means of tail gas discharged by the mixed acid waste liquid treatment system, so as to utilize tail gas heat to provide a heat source for the refrigeration mechanism, and the refrigeration mechanism utilizes the heat source to reduce the first high-temperature water to the first low-temperature water, so as to reduce the water temperature of the first heat exchange circulating water path by means of the refrigeration mechanism.

3. The tail gas waste heat utilization system of a mixed acid waste liquid treatment system according to claim 1, characterized in that: The second heat exchanger is provided with a second heat exchange water inlet and a second heat exchange water outlet, the second heat exchange water inlet is connected to a second refrigeration water outlet of the refrigeration mechanism, the second heat exchange water outlet is connected to a second refrigeration water inlet of the refrigeration mechanism, and the refrigeration mechanism reduces the water temperature of the second heat exchange circulating water path by reducing second high-temperature water from the second heat exchanger to second low-temperature water.

4. The tail gas waste heat utilization system of a mixed acid waste liquid treatment system according to claim 1, characterized in that: The refrigeration mechanism is a lithium bromide refrigeration mechanism, wherein the concentration of lithium bromide ranges from 40% to 60%.

5. The tail gas waste heat utilization system of a mixed acid waste liquid treatment system according to claim 1, characterized in that: Further comprising a first water-driven pump group and a second water-driven pump group, the first water-driven pump group is used for realizing water circulation conveying of the first heat exchange circulating water path, and the second water-driven pump group is used for realizing water circulation conveying of the second heat exchange circulating water path.

6. The tail gas waste heat utilization system of a mixed acid waste liquid treatment system according to claim 1, characterized in that: The mixed acid waste liquid treatment system comprises a decomposition furnace, a pre-concentration mechanism, an absorption mechanism, a cooling mechanism, an oxidation mechanism, a denitration mechanism and a flue gas pipeline connected with each mechanism, the circulating pipeline is connected with a cooler, the oxidation mechanism and the second heat exchanger, the cooler is used for reducing the temperature of the circulating liquid from the oxidation mechanism for the first time, the second heat exchanger is used for reducing the temperature of the circulating liquid for the second time, and the circulating pipeline is further provided with a branch connected to the flue gas pipeline, and the second heat exchanger is used for providing the second time reduced circulating liquid to the oxidation mechanism or the oxidation mechanism and the flue gas pipeline.

7. A tail gas waste heat utilization process of a mixed acid waste liquid treatment system, characterized in that: The process is based on the tail gas waste heat utilization system of the mixed acid waste liquid treatment system in any one of claims 1-6, and at least comprises two parts of tail gas waste heat recovery and circulating liquid temperature reduction, wherein the step of tail gas waste heat recovery comprises: a) introducing the tail gas into the first heat exchanger; b) the refrigeration mechanism provides first low-temperature water to the first heat exchanger, and the first heat exchanger heats the first low-temperature water into first high-temperature water by using exhaust heat; c) the first high-temperature water is supplied to the refrigeration mechanism to drive the refrigeration mechanism by using the heated first high-temperature water as a heat source; d) the refrigeration mechanism cools down the water in the first heat exchange circulating water path; the step of cooling down the circulating liquid includes: 1) the refrigeration mechanism sends second low-temperature water to the second heat exchanger; 2) in the second heat exchanger, the second low-temperature water exchanges heat with the circulating liquid to lower the temperature of the circulating liquid, and the temperature of the second low-temperature water is raised to form second high-temperature water; 3) the second high-temperature water formed by raising the temperature of the second low-temperature water is returned to the refrigeration mechanism, thereby forming a second heat exchange circulating water path between the second heat exchanger and the refrigeration mechanism.

8. The tail gas waste heat utilization process of a mixed acid waste liquid treatment system according to claim 7, characterized in that: The temperature of the first low-temperature water is 70-85℃, and the temperature of the first high-temperature water is 90-105℃.

9. The tail gas waste heat utilization process of a mixed acid waste liquid treatment system according to claim 7, characterized in that: The temperature of the second low-temperature water is 7-17℃, and the temperature of the second high-temperature water is 12-22℃.

10. The tail gas waste heat utilization process of a mixed acid waste liquid treatment system according to claim 7, characterized in that: The temperature of the circulating liquid after passing through the second heat exchanger is 15-37℃.

Images