System and method for improving heat recovery rate of acid production system

Abstract

The present invention provides a system and method for improving the heat recovery rate of an acid production system. The system comprises a low-temperature waste heat recovery device, a flue gas purification device, a flue gas drying device, a first acid pipeline, a second acid pipeline, a hot water heat exchanger, a refrigeration unit, and a chilled water heat exchanger. The low-temperature waste heat recovery device comprises a desalted water heater. The first acid pipeline is connected to a high-temperature and high-concentration acid output channel, and the hot water heat exchanger is arranged on the first acid pipeline. The desalted water input channel forms a second water replenishment source for the low-temperature waste heat recovery device. Both ends of the second acid pipeline are connected to the flue gas purification device, and the chilled water heat exchanger is arranged on the second acid pipeline. By increasing the water replenishment amount of the second water replenishment source while reducing the water replenishment amount from the first water replenishment source of the flue gas drying device to maintain the water balance of the low-temperature waste heat recovery device, the heat recovery rate of heat exchange with the high-temperature and high-concentration acid can be improved while increasing the amount of steam produced by the low-temperature waste heat recovery device.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste heat or waste heat recovery in an acid-making system, and in particular relates to a system and a method for improving the heat recovery rate of an acid-making system. Background Art

[0002] At present, the degree of waste heat recovery and utilization in acid-making systems such as flue gas acid-making, sulfuric acid-making or pyrite acid-making has become an important indicator for measuring the acid-making industry technology, and it has become a consensus to regard the acid-making system as a green energy plant that does not emit carbon dioxide. In today's increasingly tight energy situation, how to reasonably develop and utilize the low-temperature waste heat recovery technology in the acid-making system, when the high and medium temperature heat energy of the acid-making system is generally recovered and utilized, has great practical significance.

[0003] In the low-temperature waste heat recovery device in the existing acid production system, such as Figure 1 As shown, the high-temperature and high-concentration acid produced by the low-temperature waste heat recovery device and the flue gas output by the flue gas purification device enter the flue gas drying device to dilute the high-concentration acid and then enter the low-temperature waste heat recovery device. Because the water in the low-temperature waste heat recovery device is in a balanced state, that is, the water added from the desalted water heater and the water added from the flue gas drying device to the diluter are in a balanced state, so that the water added from the desalted water heater cannot be too much. In actual operation, when the amount of SO2 in the flue gas and the primary conversion rate are constant, the amount of water that needs to be added to the low-temperature waste heat recovery device is also fixed. When the amount of water in the flue gas at the outlet of the flue gas purification device and the heat generated by the low-temperature waste heat recovery device are constant, because the water added to the desalted water heater is also in a fixed state, the heat that can be absorbed by the desalted water is also fixed, that is, the amount of steam generated is also fixed, resulting in the acid temperature after being treated with desalted water is still very high; at present, this part of the acid is directly connected to the flue gas drying device, and then the heat is removed by the circulating water of the flue gas drying device, resulting in the waste of this part of the low-temperature waste heat and increasing the amount of circulating water.

[0004] Therefore, how to solve the technical problems of low recovery rate of low-temperature waste heat and difficulty in increasing the amount of steam generated in the low-temperature waste heat recovery device of the prior art has become a difficult problem to be solved urgently in the acid making industry. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a system and method for improving the heat recovery rate of an acid production system, by adding a hot water heat exchanger, a refrigeration unit, and a chilled water heat exchanger between a low-temperature waste heat recovery device and a flue gas purification device, so as to reduce the amount of water replenishment of the flue gas treated by the flue gas purification device entering the low-temperature waste heat recovery device, and increase the amount of water replenishment entering the low-temperature waste heat recovery device through the desalted water heat exchanger, thereby achieving the goal of improving the recovery rate of heat in the high-temperature and high-concentration acid output by the low-temperature waste heat recovery device, and increasing the amount of steam produced by the low-temperature waste heat recovery device.

[0006] On the one hand, the invention provides a system for improving the heat recovery rate of an acid production system, comprising a low-temperature waste heat recovery device, a flue gas purification device, and a flue gas drying device, wherein the liquid phase output end of the low-temperature waste heat recovery device is connected to the acid liquid input end of the flue gas drying device, the gas output end of the flue gas purification device is connected to the gas input end of the flue gas drying device, and the liquid phase output end of the flue gas drying device is connected to the acid liquid input end of the low-temperature waste heat recovery device to form a first replenishment water source for the low-temperature waste heat recovery device; the system also comprises a first acid pipeline, a second acid pipeline, and a hot water heat exchanger, a refrigeration unit, and a chilled water heat exchanger arranged between the first acid pipeline and the second acid pipeline;

[0007] Wherein, both ends of the second acid pipeline are connected to the flue gas purification device, and the chilled water heat exchanger is arranged on the second acid pipeline to recover the heat of the high-temperature dilute acid flowing in the second acid pipeline, and indirectly reduce the high-temperature flue gas temperature of the flue gas purification device, and reduce the water content in the flue gas output by the flue gas purification device so as to reduce the water replenishment amount of the first replenishment water source entering the low-temperature waste heat recovery device through the flue gas drying device;

[0008] The low-temperature waste heat recovery device includes a desalted water heater, which is provided with two channels, namely a high-temperature and high-concentration acid output channel and a desalted water input channel; the first acid pipeline is connected to the high-temperature and high-concentration acid output channel, and the hot water heat exchanger is arranged on the first acid pipeline to recover the heat of the high-temperature and high-concentration acid output by the low-temperature waste heat recovery device through the first acid pipeline. The desalted water input channel forms a second water replenishment source for the low-temperature waste heat recovery device, so that when the water replenishment amount of the first water replenishment source is reduced, the water replenishment amount of the second water replenishment source is increased to maintain the water balance of the low-temperature waste heat recovery device.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows: by connecting the first acid pipeline to the output channel of the high-temperature and high-concentration acid of the low-temperature waste heat recovery device, and connecting the second acid pipeline to the flue gas purification device, and arranging a hot water heat exchanger on the first acid pipeline, and arranging a chilled water heat exchanger on the second acid pipeline, and the water inlet and outlet ends of the hot water heat exchanger and the chilled water heat exchanger are respectively connected to the refrigeration unit, so that part of the moisture in the high-temperature flue gas cooled by the chilled water heat exchanger is condensed and retained in the flue gas purification device, so that the amount of water replenished by the flue gas and the high-temperature and high-concentration acid entering the low-temperature waste heat recovery device after entering the flue gas drying device is reduced. Because the low-temperature waste heat recovery device in operation is in a water balance requirement, the amount of water replenished by the low-temperature waste heat recovery device can be increased through the desalted water input channel, which means that the amount of desalted water entering the low-temperature waste heat recovery device at this time is increased, which can improve the heat recovery rate of heat exchange with the high-temperature and high-concentration acid, and increase the amount of steam produced by the low-temperature waste heat recovery device.

[0010] Preferably, the water inlet and outlet ends of the hot water heat exchanger and the chilled water heat exchanger are respectively connected to the refrigeration unit, so that the hot water produced by the hot water heat exchanger is converted into chilled water required by the chilled water heat exchanger.

[0011] Preferably, the low-temperature waste heat recovery device also includes a diluter, a high-temperature absorption tower, a high-temperature circulation tank with a built-in circulation pump, and an evaporator which are connected in sequence; the output end of the flue gas drying device is connected to the liquid phase input end of the diluter, and the output end of the circulation pump is connected to the evaporator, so that the heat of the acid liquid in the high-temperature absorption tower evaporates the water in the evaporator to produce steam, and outputs high-temperature and high-concentration acid through the first acid pipeline.

[0012] Preferably, the flue gas purification device includes a gas cooling tower, the liquid inlet end of the second acid pipeline is connected to the lower end of the gas cooling tower, and the liquid outlet end of the second acid pipeline is connected to the upper end of the gas cooling tower, so that the high-temperature dilute acid in the gas cooling tower can flow in an orderly manner in the second acid pipeline.

[0013] Preferably, the flue gas purification device further comprises a dilute acid cooler arranged on the second acid pipeline, and the dilute acid cooler is located between the gas cooling tower and the chilled water heat exchanger.

[0014] On the other hand, the invention provides a method for improving the heat recovery rate of an acid production system, using the above-mentioned system for improving the heat recovery rate of an acid production system; the method comprises the following steps:

[0015] The high-concentration acid outputted from the low-temperature waste heat recovery device and the flue gas treated by the flue gas purification device enter the flue gas drying device, and the high-concentration acid absorbs moisture in the flue gas and enters the diluter of the low-temperature waste heat recovery device to serve as the first water replenishment source of the low-temperature waste heat recovery device;

[0016] The acid liquid in the diluter enters the high-temperature absorption tower and reacts with the SO3 in the high-temperature absorption tower to generate high-temperature and high-concentration acid. The generated high-temperature and high-concentration acid is collected at the bottom of the high-temperature absorption tower and enters the high-temperature circulation tank. After being pressurized by the circulation pump, it is sent to the evaporator to obtain low-pressure steam and high-temperature and high-concentration acid. The obtained low-pressure steam is output through pipelines;

[0017] The high-temperature and high-concentration acid is first cooled by the deoxygenated water heater and the desalted water heater to reduce the acid temperature to a first preset temperature range, and then heat is exchanged by the hot water heat exchanger to reduce the acid temperature to a second preset temperature range. At this time, the water in the hot water heat exchanger is heated to a third preset temperature range to produce hot water;

[0018] After the hot water is sent to the refrigeration unit to produce chilled water, the chilled water is sent to the chilled water heat exchanger to cool the high-temperature dilute acid in the second acid pipeline, so as to indirectly reduce the high-temperature flue gas temperature of the flue gas purification device and reduce the moisture in the flue gas output by the flue gas purification device, so as to achieve a reduction in the amount of water replenishment as the first water replenishment source of the low-temperature waste heat recovery device;

[0019] When the water supply from the first water supply source decreases, in order to maintain the water balance of the low-temperature waste heat recovery device, the water supply from the second water supply source of the low-temperature waste heat recovery device needs to be increased through the desalted water input channel, so as to enhance the heat recovery of high-temperature and high-concentration acid by the hot water heat exchanger and increase the steam production of the evaporator.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: by adopting a system to improve the heat recovery rate of the acid production system, part of the moisture in the high-temperature flue gas cooled by the chilled water heat exchanger is condensed and retained in the flue gas purification device, so that the flue gas and the high-temperature and high-concentration acid entering the flue gas drying device and the amount of water added to the low-temperature waste heat recovery device is reduced. Since the operating low-temperature waste heat recovery device is in water balance requirements, the amount of water added to the low-temperature waste heat recovery device can be increased through the desalted water input channel, which means that the amount of desalted water entering the low-temperature waste heat recovery device at this time increases, which can improve the heat recovery rate of the heat exchange with the high-temperature and high-concentration acid, and can also increase the amount of steam produced by the low-temperature waste heat recovery device.

[0021] Preferably, the first preset temperature range is 105°C to 130°C, the second preset temperature range is 60°C to 110°C, and the third preset temperature range is 60°C to 100°C.

[0022] Preferably, the method further comprises:

[0023] The high-temperature flue gas enters the lower part of the gas cooling tower, and the high-temperature dilute acid is cooled to a fourth preset temperature range for the first time through the dilution cooler via the second series of acid pipelines;

[0024] After the first cooling, the dilute acid is cooled for the second time to the fifth preset temperature range by the chilled water heat exchanger, and then enters the upper end of the gas cooling tower to exchange heat with the gas in the gas cooling tower. The cooled gas enters the flue gas drying device through the gas output end of the gas cooling tower. At this time, part of the moisture in the high-temperature flue gas is condensed and retained in the gas cooling tower.

[0025] Preferably, the fourth preset temperature range is 30°C to 80°C, and the fifth preset temperature range is 5°C to 40°C.

[0026] Preferably, the method further comprises:

[0027] After the water in the hot water heat exchanger exchanges heat with the high-temperature and high-concentration acid, it enters the refrigeration unit for refrigeration;

[0028] The chilled water formed by the refrigeration unit enters the chilled water heat exchanger, exchanges heat from the dilute acid in the second acid pipeline, and then re-enters the hot water heat exchanger to convert the hot water produced by the hot water heat exchanger into the chilled water required by the chilled water heat exchanger. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0030] Figure 1 The figure is a flow chart of an acid-making system in the prior art.

[0031] Figure 2 A flow chart of a system for improving the heat recovery rate of an acid-making system provided in an embodiment of the present invention.

[0032] Description of reference numerals:

[0033] 10- low temperature waste heat recovery device, 101- first string of acid pipeline, 11- diluter, 12- high temperature absorption tower, 13- circulation pump, 14- high temperature circulation tank, 15- evaporator, 16- deoxygenated water heater, 17- deaerator, 18- desalted water heater;

[0034] 20- flue gas purification device, 201- second string of acid pipeline, 21- gas cooling tower, 22- dilute acid cooler;

[0035] 30-Flue gas drying device;

[0036] 40-hot water heat exchanger;

[0037] 50-refrigeration unit;

[0038] 60- Chilled water heat exchanger. DETAILED DESCRIPTION

[0039] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the embodiments of the present invention, and should not be construed as limiting the present invention.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0041] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0042] In one embodiment of the present invention, Figure 2 As shown, a system for improving the heat recovery rate of an acid-making system is provided, comprising a low-temperature waste heat recovery device 10, a flue gas purification device 20, and a flue gas drying device 30. In this embodiment, the liquid phase output end of the low-temperature waste heat recovery device 10 is connected to the acid liquid input end of the flue gas drying device 30, the gas output end of the flue gas purification device 20 is connected to the gas input end of the flue gas drying device 30, and the liquid phase output end of the flue gas drying device 30 is connected to the acid liquid input end of the low-temperature waste heat recovery device 10 through a pipeline to form a first water replenishment source for the low-temperature waste heat recovery device 10. Specifically, the liquid phase output end of the low-temperature waste heat recovery device 10 outputs high-temperature and high-concentration acid, and the gas output end of the flue gas purification device 20 outputs purified flue gas, wherein the flue gas contains a certain amount of moisture. When the flue gas and the high-temperature and high-concentration acid enter the flue gas drying device 30, the high-temperature and high-concentration acid adsorbs the moisture in the flue gas and plays a certain dilution role. The diluted high-temperature and high-concentration acid enters the low-temperature waste heat recovery device 10, plays the role of providing supplementary water to the low-temperature waste heat recovery device 10, and can serve as the first supplementary water source of the low-temperature waste heat recovery device 10.

[0043] Furthermore, the low-temperature waste heat recovery device 10 includes a diluter 11, a high-temperature absorption tower 12, a high-temperature circulation tank 14 with a built-in circulation pump 13, and an evaporator 15, which are connected in sequence. In this embodiment, the liquid phase output end of the flue gas drying device 30 is connected to the liquid phase input end of the diluter 11, and the output end of the circulation pump 13 is connected to the evaporator 15, so that the heat of the acid liquid in the high-temperature absorption tower 12 evaporates the water in the evaporator 15 to produce steam, and outputs high-temperature and high-concentration acid through the first acid pipeline 101. In specific practice, the high-temperature and high-concentration acid that absorbs moisture in the flue gas first enters the diluter 11, then enters the high-temperature absorption tower 12, and reacts with SO3 in the high-temperature absorption tower 12 to generate high-concentration acid. The generated high-concentration acid is collected at the bottom of the high-temperature absorption tower 12 and enters the high-temperature circulation tank 14. After being pressurized by the circulation pump 13, it is sent to the evaporator 15. At this time, low-pressure steam and high-temperature and high-concentration acid are respectively obtained. The obtained low-pressure steam is output through a pipeline, and the high-temperature and high-concentration acid is output through the output end of the low-temperature waste heat recovery device 10.

[0044] Furthermore, the low-temperature waste heat recovery device 10 also includes a desalted water heater 16, a deaerator 17 and a deoxygenated water heater 18. In this embodiment, the desalted water heater 18 is provided with two channels, namely, a high-temperature and high-concentration acid output channel and a desalted water input channel; wherein, the desalted water input channel forms a second water replenishment source for the low-temperature waste heat recovery device 10. In specific practice, desalted water is input through the desalted water input channel, and after being heated by the desalted water heater 16, it is sent to the deaerator 17 for thermal deoxygenation to obtain deoxygenated water with a higher temperature. The deoxygenated water is pressurized and pumped to the deoxygenated water heater 16 by a low-pressure pump to increase the temperature. After being heated, it is sent to the evaporator 15, and the obtained low-pressure steam is output through a pipeline.

[0045] Furthermore, the system for improving the heat recovery rate of the acid production system further includes a first acid pipeline 101, a second acid pipeline 201, and a hot water heat exchanger 40, a refrigeration unit 50, and a chilled water heat exchanger 60 disposed between the first acid pipeline 101 and the second acid pipeline 201. In this embodiment, the first acid pipeline 101 is connected to the high-temperature and high-concentration acid output channel, and the hot water heat exchanger 40 is disposed on the first acid pipeline 101, and is used to heat the heat of the high-temperature and high-concentration acid output by the low-temperature waste heat recovery device 10 through the first acid pipeline 101, thereby recovering heat.

[0046] Furthermore, the water inlet and outlet ends of the hot water heat exchanger 40 and the chilled water heat exchanger 60 are respectively connected to the refrigeration unit 50, so that the hot water produced by the hot water heat exchanger 40 is converted into chilled water required by the chilled water heat exchanger 60, so that the hot water heat exchanger 40 exchanges the heat of the high-temperature and high-concentration acid output by the low-temperature waste heat recovery device 10, and the chilled water heat exchanger 60 exchanges the heat of the high-temperature flue gas of the flue gas purification device 20 through the circulating water of the refrigeration unit 50, thereby improving the recovery rate of the low-temperature waste heat of the low-temperature waste heat recovery device 10, and because the water for recovering heat is recycled, the water consumption of the entire system is reduced.

[0047] Further, the flue gas purification device 20 includes a gas cooling tower 21, the liquid inlet end of the second acid pipeline 201 is connected to the lower end of the gas cooling tower 21, and the liquid outlet end of the second acid pipeline 201 is connected to the upper end of the gas cooling tower 21, so that the high-temperature flue gas in the gas cooling tower 21 flows orderly in the second acid pipeline 201. In this embodiment, the chilled water heat exchanger 60 is arranged on the second acid pipeline 21 to exchange heat of the high-temperature dilute acid flowing in the second acid pipeline 201, so as to recover heat.

[0048] Furthermore, the flue gas purification device 20 also includes a dilute acid cooler 22 arranged on the second acid string pipeline 201, and the dilute acid cooler 22 is located between the gas cooling tower 21 and the chilled water heat exchanger 60. Its purpose is to allow the high-temperature dilute acid of the gas cooling tower 21 to be cooled once through the dilute acid cooler 22 before heat exchange in the chilled water heat exchanger 60, and then cooled a second time through the chilled water heat exchanger 60, so as to further condense the moisture contained in the flue gas and retain it in the gas cooling tower, thereby reducing the water content in the flue gas discharged from the flue gas purification device 20.

[0049] To summarize, in this embodiment, the water content in the flue gas discharged by the flue gas purification device is further retained in the flue gas purification device through the additional chilled water heat exchanger. When the diluted high-concentration acid from the flue gas drying device enters the diluter, it can be used as the first water supply source for the low-temperature waste heat recovery device, thereby reducing the amount of water supplied by the first water supply source. Due to the water balance requirement of the low-temperature waste heat recovery device, the amount of water supplied by the second water supply source can be increased by increasing the amount of water supplied by the second water supply source, that is, by increasing the desalted water through the desalted water input channel, thereby increasing the amount of water supplied by the second water supply source of the low-temperature waste heat recovery device. This means that the amount of desalted water entering the low-temperature waste heat recovery device increases at this time, which can improve the heat recovery rate of heat exchange with high-temperature and high-concentration acid on the one hand, and increase the amount of steam produced by the low-temperature waste heat recovery device on the other hand, thereby effectively solving the technical problems of low recovery rate of low-temperature waste heat and difficulty in increasing the amount of steam generated in the low-temperature waste heat recovery device in the prior art.

[0050] Furthermore, the method for improving the heat recovery rate of the acid production system of the system of this embodiment comprises the following steps:

[0051] Step 1: The high-concentration acid output by the low-temperature waste heat recovery device and the flue gas treated by the flue gas purification device enter the flue gas drying device, and the high-concentration acid absorbs moisture in the flue gas and enters the diluter of the low-temperature waste heat recovery device to serve as the first water replenishment source of the low-temperature waste heat recovery device.

[0052] Step 2: The acid liquid in the diluter enters the high-temperature absorption tower and reacts with the SO3 in the high-temperature absorption tower to generate high-temperature and high-concentration acid. The generated high-temperature and high-concentration acid is collected at the bottom of the high-temperature absorption tower and enters the high-temperature circulation tank. After being pressurized by the circulation pump, it is sent to the evaporator to obtain low-pressure steam and high-temperature and high-concentration acid. The obtained low-pressure steam is output through a pipeline;

[0053] Among them, desalted water is input through the desalted water input channel, and after being heated by the desalted water heater, it is sent to the deaerator for thermal deoxygenation to obtain deoxygenated water with a higher temperature. The deoxygenated water is pressurized and pumped to the deoxygenated water heater by a low-pressure pump to increase the temperature. After being heated, it is sent to the evaporator, and the obtained low-pressure steam is output through a pipeline.

[0054] Step 3: The high-temperature and high-concentration acid is first cooled by the deoxygenated water heater and the desalted water heater to reduce the acid temperature to 105°C to 130°C, and then heat is exchanged through the hot water heat exchanger to reduce the acid temperature to 60°C to 110°C. At this time, the water in the hot water heat exchanger is heated to 60°C to 100°C to produce hot water;

[0055] Among them, the water in the hot water heat exchanger exchanges heat with the high-temperature and high-concentration acid and then enters the refrigeration unit for refrigeration;

[0056] The chilled water formed by the refrigeration unit enters the chilled water heat exchanger, exchanges heat with the flue gas in the second acid pipeline, and then re-enters the hot water heat exchanger to convert the hot water produced by the hot water heat exchanger into the chilled water required by the chilled water heat exchanger.

[0057] Step 4: After the hot water is sent to the refrigeration unit to produce chilled water, the chilled water is sent to the chilled water heat exchanger to cool the high-temperature dilute acid in the second acid pipeline to reduce the moisture in the flue gas output by the flue gas purification device, so as to reduce the amount of water replenishment as the first water replenishment source of the low-temperature waste heat recovery device;

[0058] Among them, the high-temperature flue gas enters the lower part of the gas cooling tower, and the high-temperature flue gas passes through the second series of acid pipelines and the dilution cooler to be cooled to 30℃~80℃ for the first time;

[0059] After the first cooling, the flue gas is cooled to 5℃~40℃ for the second time by the chilled water heat exchanger, enters the upper end of the gas cooling tower, and enters the flue gas drying device through the output end of the gas cooling tower. At this time, part of the moisture in the high-temperature flue gas is condensed and retained in the gas cooling tower.

[0060] Step 5: When the water replenishment amount of the first water replenishment source decreases, in order to maintain the water balance of the low-temperature waste heat recovery device, the water replenishment amount of the second water replenishment source of the low-temperature waste heat recovery device needs to be increased through the desalted water input channel.

[0061] In summary, through the system for improving the heat recovery rate of the acid production system in this embodiment, the reduction of the first make-up water source is reduced, so that the make-up water amount of the second make-up water source can be increased, and the make-up water amount of the second make-up water source of the low-temperature waste heat recovery device is increased, which means that the amount of desalted water entering the low-temperature waste heat recovery device at this time increases. On the one hand, the heat recovery rate of heat exchange with high-temperature and high-concentration acid can be improved, and on the other hand, the amount of steam produced by the low-temperature waste heat recovery device can be increased, thereby effectively solving the technical problems of low recovery rate of low-temperature waste heat and difficulty in increasing the amount of steam generated in the low-temperature waste heat recovery device in the prior art.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for improving the heat recovery rate of an acid-making system, comprising a low-temperature waste heat recovery device, a flue gas purification device, and a flue gas drying device, wherein the liquid phase output end of the low-temperature waste heat recovery device is connected to the acid liquid input end of the flue gas drying device, the gas output end of the flue gas purification device is connected to the gas input end of the flue gas drying device, and the liquid phase output end of the flue gas drying device is connected to the acid liquid input end of the low-temperature waste heat recovery device to form a first water replenishment source for the low-temperature waste heat recovery device; characterized in that, The system also includes a first string of acid pipelines, a second string of acid pipelines, and a hot water heat exchanger, a refrigeration unit, and a chilled water heat exchanger disposed between the first string of acid pipelines and the second string of acid pipelines; Wherein, both ends of the second acid pipeline are connected to the flue gas purification device, and the chilled water heat exchanger is arranged on the second acid pipeline to recover the heat of the high-temperature dilute acid flowing in the second acid pipeline, and indirectly reduce the high-temperature flue gas temperature of the flue gas purification device, and reduce the water content in the flue gas output by the flue gas purification device, so as to reduce the water replenishment amount of the first water replenishment source entering the low-temperature waste heat recovery device through the flue gas drying device; The low-temperature waste heat recovery device comprises a desalted water heater, and the desalted water heater is provided with two channels, namely, a high-temperature and high-concentration acid output channel and a desalted water input channel; the first acid pipeline is connected to the high-temperature and high-concentration acid output channel, and the hot water heat exchanger is provided on the first acid pipeline to recover the heat of the high-temperature and high-concentration acid outputted by the low-temperature waste heat recovery device through the first acid pipeline, and the desalted water input channel forms a second water replenishment source for the low-temperature waste heat recovery device, so that when the water replenishment amount of the first water replenishment source is reduced, the water replenishment amount of the second water replenishment source is increased to maintain the water balance of the low-temperature waste heat recovery device; The flue gas purification device includes a gas cooling tower, the liquid inlet end of the second acid pipeline is connected to the lower end of the gas cooling tower, and the liquid outlet end of the second acid pipeline is connected to the upper end of the gas cooling tower, so that the high-temperature dilute acid in the gas cooling tower can flow in the second acid pipeline in an orderly manner.

2. The system for improving heat recovery rate of an acid production system according to claim 1, characterized in that: The water inlet and outlet ends of the hot water heat exchanger and the chilled water heat exchanger are respectively connected to the refrigeration unit, so that the hot water produced by the hot water heat exchanger is converted into chilled water required by the chilled water heat exchanger.

3. The system for improving heat recovery rate of an acid production system according to claim 1, characterized in that: The low-temperature waste heat recovery device also includes a diluter, a high-temperature absorption tower, a high-temperature circulation tank with a built-in circulation pump, and an evaporator that are connected in sequence; the liquid phase output end of the flue gas drying device is connected to the liquid phase input end of the diluter, and the output end of the circulation pump is connected to the evaporator, so that the heat of the acid liquid in the high-temperature absorption tower evaporates the water in the evaporator to produce steam, and outputs high-temperature and high-concentration acid through the first acid pipeline.

4. The system for improving heat recovery rate of an acid production system according to claim 1, characterized in that: The flue gas purification device also includes a dilute acid cooler arranged on the second acid pipeline, and the dilute acid cooler is located between the gas cooling tower and the chilled water heat exchanger.

5. A method for improving the heat recovery rate of an acid production system, characterized in that: The system for improving the heat recovery rate of the acid production system according to claim 4 is used; the method comprises the following steps: The high-concentration acid outputted from the low-temperature waste heat recovery device and the flue gas treated by the flue gas purification device enter the flue gas drying device, and the high-concentration acid absorbs moisture in the flue gas and enters the diluter of the low-temperature waste heat recovery device to serve as the first water replenishment source of the low-temperature waste heat recovery device; The acid liquid in the diluter enters the high-temperature absorption tower and reacts with the SO3 in the high-temperature absorption tower to generate high-temperature and high-concentration acid. The generated high-temperature and high-concentration acid is collected at the bottom of the high-temperature absorption tower and enters the high-temperature circulation tank. After being pressurized by the circulation pump, it is sent to the evaporator to obtain low-pressure steam and high-temperature and high-concentration acid. The obtained low-pressure steam is output through pipelines; The high-temperature and high-concentration acid is first cooled by the deoxygenated water heater and the desalted water heater to reduce the acid temperature to a first preset temperature range, and then heat is exchanged by the hot water heat exchanger to reduce the acid temperature to a second preset temperature range. At this time, the water in the hot water heat exchanger is heated to a third preset temperature range to produce hot water; After the hot water is sent to the refrigeration unit to produce chilled water, the chilled water is sent to the chilled water heat exchanger to cool the high-temperature dilute acid in the second acid pipeline, so as to indirectly reduce the high-temperature flue gas temperature of the flue gas purification device and reduce the moisture in the flue gas output by the flue gas purification device, so as to achieve a reduction in the amount of water replenishment as the first water replenishment source of the low-temperature waste heat recovery device; When the water supply from the first water supply source decreases, in order to maintain the water balance of the low-temperature waste heat recovery device, the water supply from the second water supply source of the low-temperature waste heat recovery device needs to be increased through the desalted water input channel, so as to enhance the heat recovery of high-temperature and high-concentration acid by the hot water heat exchanger and increase the steam production of the evaporator.

6. The method for improving heat recovery rate of an acid production system according to claim 5, characterized in that: The first preset temperature range is 105°C to 130°C, the second preset temperature range is 60°C to 110°C, and the third preset temperature range is 60°C to 100°C.

7. The method for improving heat recovery rate of an acid production system according to claim 5, characterized in that: The method further comprises: The high-temperature flue gas enters the lower part of the gas cooling tower, and the high-temperature dilute acid is cooled to a fourth preset temperature range for the first time through the dilution cooler via the second series of acid pipelines; After the first cooling, the dilute acid is cooled for the second time to the fifth preset temperature range by the chilled water heat exchanger, and then enters the upper end of the gas cooling tower to exchange heat with the gas in the gas cooling tower. The cooled gas enters the flue gas drying device through the gas output end of the gas cooling tower. At this time, part of the moisture in the high-temperature flue gas is condensed and retained in the gas cooling tower.

8. The method for improving heat recovery rate of an acid production system according to claim 7, characterized in that: The fourth preset temperature range is 30°C to 80°C, and the fifth preset temperature range is 5°C to 40°C.

9. The method for improving heat recovery rate of an acid production system according to claim 5, characterized in that: The method further comprises: After the water in the hot water heat exchanger exchanges heat with the high-temperature and high-concentration acid, it enters the refrigeration unit for refrigeration; The chilled water formed by the refrigeration unit enters the chilled water heat exchanger, exchanges heat from the dilute acid in the second acid pipeline, and then re-enters the hot water heat exchanger to convert the hot water produced by the hot water heat exchanger into the chilled water required by the chilled water heat exchanger.

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