Tail gas waste heat utilization system of mixed acid waste liquid treatment system

Abstract

The utility model relates to the technical field of acid pickling waste liquid resourceful treatment and regeneration, in particular to a tail gas waste heat utilization system of a mixed acid waste liquid treatment system, which is used for treating mixed acid waste liquid and discharging high-temperature tail gas and comprises a first heat exchanger, a second heat exchanger and a refrigerating mechanism. A first heat exchange circulating water path is arranged between the first heat exchanger and the refrigerating mechanism; the first heat exchanger provides a heat source for the refrigerating mechanism by using tail gas heat and reduces the water temperature of the first heat exchange circulating water path by means of the refrigerating mechanism; a second heat exchange circulating water path is arranged between the second heat exchanger and the refrigerating mechanism. The second heat exchanger is further connected to a circulating pipeline of the mixed acid waste liquid treatment system so as to reduce the temperature of circulating liquid. Through the tail gas waste heat utilization system, flue gas waste heat of the mixed acid waste liquid treatment system is effectively recycled, and energy waste is reduced; and the second heat exchanger reduces the circulating liquid temperature of the mixed acid waste liquid treatment system and improves the oxidation efficiency of the flue gas.

Description

Technical Field

[0001] The utility model relates to the technical field of resource treatment and regeneration of pickling waste liquid, in particular to a tail gas waste heat utilization system of a mixed acid waste liquid treatment system. Background Art

[0002] Pickling in the metallurgical industry is an essential step in metal surface treatment, playing a particularly important role in the pretreatment of materials such as plates, bars, and wire rods. While this process improves the processing properties of metal materials, it also generates large amounts of pickling wastewater. The waste acid and heavy metals contained in this wastewater pose a serious threat to the environment, making it a pollutant that metallurgical companies urgently need to address.

[0003] Due to the harmful substances they contain, these pickling wastewaters are classified as major substances on the national hazardous waste list. Existing technologies include a mixed acid wastewater recycling system that utilizes concentration, decomposition, acid absorption, oxidation, and denitrification to recycle mixed acid wastewater. However, this treatment method produces high-temperature exhaust gases, which are directly discharged into the air, resulting in significant energy waste. Therefore, an effective heat utilization system is urgently needed to recycle the large amount of heat emitted by mixed acid wastewater recycling systems. Summary of the Invention

[0004] The purpose of the utility model is to provide a tail gas waste heat utilization system and process for a mixed acid waste liquid treatment system, so as to solve the problem of energy waste in the mixed acid waste liquid treatment process.

[0005] To achieve the above-mentioned objectives, the technical solution of the present invention 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 to treat mixed acid waste liquid and discharge 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 circulation water circuit 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 to utilize the heat of the tail gas to provide a heat source to the refrigeration mechanism and to reduce the water temperature of the first heat exchange circulation water circuit with the help of the refrigeration mechanism; a second heat exchange circulation water circuit is provided between the second heat exchanger and the refrigeration mechanism, the water temperature of the second heat exchange circulation water circuit is reduced with the help of the refrigeration mechanism, and the second heat exchanger is also connected to the circulation pipeline of the circulating liquid of the mixed acid waste liquid treatment system to reduce the temperature of the circulating liquid.

[0006] 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, and 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 with the help of the tail gas discharged from the mixed acid waste liquid treatment system, thereby using the heat of the tail gas to provide a heat source to the refrigeration mechanism, and the refrigeration mechanism uses the heat source to cool the first high-temperature water to the first low-temperature water, thereby reducing the water temperature of the first heat exchange circulation water circuit with the help of the refrigeration mechanism.

[0007] 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, and the second heat exchange water outlet is connected to the second refrigeration water inlet of the refrigeration mechanism. The refrigeration mechanism reduces the water temperature of the second heat exchange circulation water circuit by cooling the second high-temperature water from the second heat exchanger to second low-temperature water.

[0008] In one embodiment, the refrigeration mechanism is a lithium bromide refrigeration mechanism, wherein the concentration of lithium bromide ranges from 40% to 60%.

[0009] In one embodiment, it also includes 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 transportation in the first heat exchange circulation water circuit, and the second water-driven pump group is used to realize water circulation transportation in the second heat exchange circulation water circuit.

[0010] In one embodiment, the mixed acid waste liquid treatment system includes a decomposition furnace, a pre-concentration mechanism, an absorption mechanism, a cooling mechanism, an oxidation mechanism, a denitrification mechanism and a flue gas pipe connecting the various mechanisms. The circulation pipeline is connected to a cooler, an oxidation mechanism and the second heat exchanger. The cooler is used to cool the circulating liquid from the oxidation mechanism for the first time, and the second heat exchanger is used to cool the circulating liquid for the second time. The circulation pipeline is also provided with a branch connected to the flue gas pipe. The second heat exchanger is used to provide the circulating liquid after the second cooling to the oxidation mechanism or the oxidation mechanism and the flue gas pipe.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) Through the tail gas waste 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, reducing energy waste.

[0013] (2) The heat exchange process of the second heat exchanger reduces the temperature of the circulating fluid in the mixed acid waste liquid treatment system, 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.

[0014] (3) Effectively utilize the flue gas heat as a heat source to promote the operation of the refrigeration mechanism, so that the refrigeration mechanism outputs low-temperature water. The low-temperature water reduces the temperature of the flue gas on the one hand and the temperature of the circulating fluid on the other hand, thus realizing the recovery and utilization of heat. In turn, the heat is used to reduce the temperature of the circulating fluid and improve the oxidation efficiency, thus realizing the effective circulation of heat.

[0015] (4) It has achieved multiple improvements in production efficiency, energy efficiency and economic benefits, and has high economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present utility model.

[0017] Figure 2 It is a partial structural diagram of an embodiment of the utility model.

[0018] Figure 3 It is a partial structural diagram of another embodiment of the present invention. DETAILED DESCRIPTION

[0019] To further illustrate various embodiments, the present invention is provided with accompanying drawings. These drawings form part of the disclosure of this invention and are primarily used to illustrate the embodiments and, in conjunction with the relevant description in the specification, to explain the operating principles of the embodiments. By referring to these drawings, those skilled in the art will understand other possible implementations and the advantages of this invention. The components in the figures are not drawn to scale, and similar reference numerals are generally used to represent similar components.

[0020] See Figure 1 and Figure 2As shown, the present invention discloses a tail gas waste heat utilization system for a mixed acid waste liquid treatment system. The mixed acid waste liquid treatment system 10 is used to treat mixed acid waste liquid and discharge 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 circulation water circuit 201 is provided between the first heat exchanger 21 and the refrigeration mechanism 23. The first heat exchanger 21 is also connected to the tail gas discharge end of the mixed acid waste liquid treatment system 10 to use the heat of the tail gas to provide a heat source to the refrigeration mechanism 23 and to reduce the water temperature of the first heat exchange circulation water circuit 201 by means of the refrigeration mechanism 23. A second heat exchange circulation water circuit 202 is provided between the second heat exchanger 22 and the refrigeration mechanism 23. The refrigeration mechanism 23 is used to reduce the water temperature of the second heat exchange circulation water circuit 202. The second heat exchanger 22 is also connected to the circulation pipeline of the circulating fluid of the mixed acid waste liquid treatment system 10 to reduce the temperature of the circulating fluid.

[0021] The mixed acid waste liquid treatment system 10 includes a decomposition furnace 11, a pre-concentration mechanism 12, an absorption mechanism 13, a cooling mechanism 14, an oxidation mechanism 15, a denitrification mechanism 16, and a flue gas duct connecting these mechanisms, enabling the recycling and reuse 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 injected into the decomposition furnace 11 for decomposition. The hot flue gas generated during the decomposition process enters the pre-concentration mechanism 12 through the flue gas duct for cooling and dust removal. The cooled flue gas then enters the absorption mechanism 13 through the flue gas duct to recover the regenerated acid. The cooling mechanism 14 further reduces the flue gas temperature, ensuring 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 the regenerated acid. The operating temperature of the oxidation mechanism 15 has a significant 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 circulation pipeline 101. A cooler 17 in the circulation pipeline 101 cools the circulating liquid, thereby reducing the operating temperature of the oxidation mechanism 15. Finally, the denitrification mechanism 16 denitrates the flue gas to ensure that the nitrogen oxide content in the flue gas meets the emission standards. The catalytic reaction during denitrification may require heating the flue gas, resulting in a higher temperature for the flue gas ultimately discharged from the mixed acid waste liquid treatment system 10. In this embodiment of the mixed acid waste liquid treatment system 10, the flue gas temperature discharged from the exhaust outlet is between 180°C and 250°C. Directly discharging the flue gas into the air would result in significant heat loss and excessively high ambient temperature around the exhaust outlet, hindering heat dissipation from the mixed acid waste liquid treatment system 10.

[0022] The present invention reduces the exhaust flue gas temperature by providing a first heat exchanger 21, converting the flue gas temperature into the temperature of the first heat exchange circulation water circuit 201, and using this heat as a heat source for the refrigeration mechanism 23, thereby driving the refrigeration mechanism 23 to operate, so that heat is recycled and utilized, improving energy utilization and preventing the surrounding air from being excessively heated. Secondly, since the oxidation mechanism 15 of the mixed acid waste liquid treatment system 10 needs to be cooled during operation, the present invention adds a second heat exchanger 22 to the circulating fluid circulation pipeline 101 thereof, and utilizes the second heat exchange circulation water circuit 202 between the refrigeration mechanism 23 and the second heat exchanger 22 to reduce the circulating fluid temperature of the mixed acid waste liquid treatment system 10, thereby improving the cooling effect on the oxidation mechanism 15, thereby improving the oxidation efficiency. The present invention can reduce the temperature of the flue gas discharged from the mixed acid waste liquid treatment system 10 and reduce the impact of the flue gas temperature on the environment through water circulation between the first heat exchanger 21, the second heat exchanger 22 and the refrigeration mechanism 23; secondly, the flue gas temperature can be used as a heat source for the refrigeration mechanism 23 to drive the refrigeration mechanism 23 to work, thereby realizing heat recovery and reuse, and improving energy utilization; thirdly, the refrigeration mechanism 23 can also use the heat from the flue gas to achieve heat conversion, reduce the temperature of the second heat exchange circulation water path 202, and achieve the purpose of cooling the circulating liquid and improving the oxidation efficiency; finally, the refrigeration mechanism 23 can reduce the water temperature of the first heat exchange circulation water path 201 and the second heat exchange circulation water path 202 by relying solely on the heat of the exhaust gas, thereby providing low-temperature water for the first heat exchanger 21 and the second heat exchanger 22, and then using the low-temperature water to reduce the temperature of the flue gas and the circulating liquid, without the need for energy input and making full use of heat conversion to optimize the treatment effect of the mixed acid waste liquid treatment system 10.

[0023] 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, and the first heat exchange water outlet is connected to the first refrigeration water inlet of the refrigeration mechanism 23. The first heat exchanger 21 is used to heat the first low-temperature water from the refrigeration mechanism 23 into first high-temperature water with the help of the exhaust gas discharged from the mixed acid waste liquid treatment system 10, thereby using the heat of the exhaust gas to provide a heat source to the refrigeration mechanism 23. The refrigeration mechanism 23 uses the heat source to cool the first high-temperature water to first low-temperature water, thereby reducing the water temperature of the first heat exchange circulation water circuit 201 with the help of the refrigeration mechanism 23.

[0024] 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. 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 circulation water circuit 202 by cooling the second high-temperature water from the second heat exchanger 22 to second low-temperature water.

[0025] The first heat exchanger 21 and the second heat exchanger 22 are respectively provided with independent heat exchange circulation water circuits to realize heat exchange with the refrigeration mechanism 23, which can not only reduce the water temperature of their respective heat exchange circulation water circuits, but also provide water of different temperatures to the first heat exchanger 21 and the second heat exchanger 22 as needed.

[0026] The second heat exchanger 22 participates in the circulating liquid flow direction of the circulating pipeline 101 of the mixed acid waste liquid treatment system 10. Figure 2 As shown, the circulating liquid flows out of the oxidation mechanism 15 and enters the cooler 17 through a one-way valve for the first cooling. The circulation pipeline is provided with two branches so that the circulating liquid leaving the cooler 17 is divided into two branches. In this embodiment, the circulating liquid is split before leaving the cooler 17 and entering the second heat exchanger 22. One branch is split into the flue gas pipe and the other branch enters the second heat exchanger 22 for the second cooling. Thus, the second heat exchanger 22 provides the oxidation mechanism 15 with the circulating liquid after two-stage cooling, so that the temperature of the circulating liquid is further reduced, ensuring that the oxidation mechanism 15 can operate at a lower temperature and improve the oxidation efficiency. Each branch is provided with a valve to control the on-off and flow rate of the circulating liquid. The part of the circulating liquid that enters the flue gas pipe is used to cool the flue gas in the mixed acid waste liquid treatment system 10. The circulating liquid is split before entering the second heat exchanger 22 so that the circulating liquid entering the second heat exchanger 22 is less, so that the cooling effect of the second heat exchanger 22 on this part of the circulating liquid is more obvious. In another embodiment, refer to Figure 3 As shown, the circulating liquid is cooled twice by the cooler 17 and the second heat exchanger 22 and then split. One path enters the flue gas duct to cool the flue gas, and the other path enters the oxidation mechanism 15. Thus, the second heat exchanger supplies the circulating liquid that has been cooled twice to the flue gas duct and the oxidation mechanism respectively. This design allows the circulating liquid to enter the flue gas duct at a lower temperature, and the cooling effect on the flue gas is more obvious.

[0027] Refrigeration mechanism 23 of this embodiment is a lithium bromide refrigeration mechanism, wherein the lithium bromide concentration ranges from 40% to 60%. It utilizes the input heat source to reduce the water temperature of first heat exchange circulation water path 201 and second heat exchange circulation water path 202, thereby achieving the purpose of cooling. The operating principle of the lithium bromide refrigeration mechanism is conventional and will not be further described here.

[0028] See Figure 1 As shown, the system further includes a first water-driven pump assembly and a second water-driven pump assembly. The first water-driven pump assembly is used to circulate water in the first heat exchange circulation waterway 201, and the second water-driven pump assembly is used to circulate water in the second heat exchange circulation waterway 202. The first water-driven pump assembly and the second water-driven pump assembly can ensure the normal circulation of water in the first heat exchange circulation waterway 201 and the second heat exchange circulation waterway 202, so that heat exchange proceeds normally, thereby achieving the desired heat exchange effect.

[0029] The refrigeration mechanism 23 is also connected to a cooling water circuit 203, which is used to cool the refrigeration mechanism 23 to prevent the refrigeration mechanism 23 from overheating during operation. The first heat exchange circulation water circuit 201 and the second heat exchange circulation water circuit 202 are each provided with a water supply circuit 204, so that water can circulate through the first heat exchange circulation water circuit 201 and the second heat exchange circulation water circuit 202 when operation begins. When the first heat exchange circulation water circuit 201 and the second heat exchange circulation water circuit 202 are performing normal water circulation, the water supply circuit 204 can no longer supply water to the first heat exchange circulation water circuit 201 and the second heat exchange circulation water circuit 202. In addition, the temperature of the water supplied by the water supply circuit 204 should match the water temperature of the corresponding heat exchange circulation water circuit to ensure that the water temperature of the heat exchange circulation water circuit meets the requirements.

[0030] The utility model also discloses a tail gas waste heat utilization process of a mixed acid waste liquid treatment system. The process is based on the tail gas waste heat utilization system of the mixed acid waste liquid treatment system. The process includes at least two parts: tail gas waste heat recovery and circulating liquid cooling. The tail gas waste heat recovery step includes:

[0031] a) introducing the tail gas into the first heat exchanger 21;

[0032] b) The refrigeration mechanism 23 provides first low-temperature water to the first heat exchanger 21, and the first heat exchanger 21 uses the heat of the exhaust gas to heat the first low-temperature water into first high-temperature water;

[0033] c) supplying the first high-temperature water to the refrigeration mechanism 23, so that the heated first high-temperature water is used as a heat source to drive the refrigeration mechanism 23;

[0034] d) The refrigeration mechanism 23 cools the water in the first heat exchange circulation water path 201 .

[0035] The steps for cooling the circulating fluid include:

[0036] 1) The refrigeration mechanism 23 delivers the second low-temperature water to the second heat exchanger 22;

[0037] 2) In the second heat exchanger 22, the second low-temperature water exchanges heat with the circulating fluid to reduce the temperature of the circulating fluid, and the temperature of the second low-temperature water increases to form second high-temperature water;

[0038] 3) The second high-temperature water formed by heating the second low-temperature water flows back to the refrigeration mechanism 23 , thereby forming a second heat exchange circulation water path 202 between the second heat exchanger 22 and the refrigeration mechanism 23 .

[0039] The second heat exchanger 22 is respectively Figure 2 or Figure 3 One of the embodiments shown cools the circulating fluid. The two cooling methods have been described in detail in the above content and will not be repeated here.

[0040] The temperature of the first low-temperature water is 70-85°C, and in this embodiment, it is more preferably 75-80°C. The temperature of the first high-temperature water is 90-105°C, and in this embodiment, it is more preferably 95-100°C.

[0041] The temperature of the second low-temperature water is 7-17°C, and in this embodiment, it is more preferably 7-12°C. The temperature of the second high-temperature water is 12-22°C, and in this embodiment, it is more preferably 12-18°C.

[0042] The temperature of the circulating fluid after passing through the second heat exchanger 22 is 15-37°C, and in this embodiment, it is further preferably 20-30°C. The flow rate range of the circulating fluid is 60-160m 3 / h.

[0043] Although the present invention is specifically shown and described in conjunction with the preferred embodiments, those skilled in the art should understand that the remaining undescribed parts are prior art, and that various changes made to the present invention in form and detail without departing from the spirit and scope of the present invention as defined by the appended claims fall within the scope of protection of the present invention.

Claims

1. A tail gas waste heat utilization system for a mixed acid waste liquid treatment system, characterized by: The mixed acid waste liquid treatment system is used to treat mixed acid waste liquid and discharge high-temperature exhaust gas. The exhaust gas waste heat utilization system includes a first heat exchanger, a second heat exchanger and a refrigeration mechanism. A first heat exchange circulation water circuit is provided between the first heat exchanger and the refrigeration mechanism. The first heat exchanger is also connected to the exhaust gas discharge end of the mixed acid waste liquid treatment system to utilize the heat of the exhaust gas to provide a heat source to the refrigeration mechanism and use the refrigeration mechanism to reduce the water temperature of the first heat exchange circulation water circuit; a second heat exchange circulation water circuit is provided between the second heat exchanger and the refrigeration mechanism. The water temperature of the second heat exchange circulation water circuit is reduced by means of the refrigeration mechanism. The second heat exchanger is also connected to the circulation pipeline of the circulating liquid of the mixed acid waste liquid treatment system to reduce the temperature of the circulating liquid.

2. The tail gas waste heat utilization system of the 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 the first refrigeration water outlet of the refrigeration mechanism, and 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 with the help of the tail gas discharged from the mixed acid waste liquid treatment system, thereby using the heat of the tail gas to provide a heat source to the refrigeration mechanism, and the refrigeration mechanism uses the heat source to cool the first high-temperature water to the first low-temperature water, thereby reducing the water temperature of the first heat exchange circulation water circuit with the help of the refrigeration mechanism.

3. The tail gas waste heat utilization system of the 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 the second refrigeration water outlet of the refrigeration mechanism, and the second heat exchange water outlet is connected to the second refrigeration water inlet of the refrigeration mechanism. The refrigeration mechanism reduces the water temperature of the second heat exchange circulation water circuit by cooling the second high-temperature water from the second heat exchanger to second low-temperature water.

4. The tail gas waste heat utilization system of the 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 the mixed acid waste liquid treatment system according to claim 1, characterized in that: It also includes 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 transportation in the first heat exchange circulation water circuit, and the second water-driven pump group is used to realize water circulation and transportation in the second heat exchange circulation water circuit.

6. The tail gas waste heat utilization system of the mixed acid waste liquid treatment system according to claim 1, characterized in that: The mixed acid waste liquid treatment system includes a decomposition furnace, a pre-concentration mechanism, an absorption mechanism, a cooling mechanism, an oxidation mechanism, a denitrification mechanism and a flue gas duct connecting the various mechanisms. The circulation pipeline is connected to a cooler, an oxidation mechanism and the second heat exchanger. The cooler is used to cool the circulating liquid from the oxidation mechanism for the first time, and the second heat exchanger is used to cool the circulating liquid for the second time. The circulation pipeline is also provided with a branch connected to the flue gas duct. The second heat exchanger is used to provide the circulating liquid after the second cooling to the oxidation mechanism or the oxidation mechanism and the flue gas duct.

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