A comprehensive utilization system for waste heat of flue gas in an ammonia-based decarbonization process for industrial flue gas

Abstract

The present invention discloses a comprehensive utilization system for waste heat of flue gas in an ammonia-based decarbonization process of industrial flue gas, belonging to the technical field of waste heat utilization. The ammonia-based decarbonization and waste heat comprehensive utilization system of the present invention includes a lithium bromide refrigerating machine and a three-stage cooling heat exchanger, a booster fan, a four-stage cooling heat exchanger, an ammonia-based decarbonization tower and a heating heat exchanger that are connected in sequence; the heating heat exchanger is circularly connected to the first-stage heat exchange device of the three-stage cooling heat exchanger and the first-stage heat exchange device of the four-stage cooling heat exchanger respectively through a first-stage circulating water pipeline; the lithium bromide refrigerating machine is circularly connected to the second-stage heat exchange device of the three-stage cooling heat exchanger and the second-stage heat exchange device of the four-stage cooling heat exchanger respectively through a second-stage circulating water pipeline; the lithium bromide refrigerating machine is circularly connected to the fourth-stage heat exchange device of the four-stage cooling heat exchanger and the ammonia-based decarbonization tower respectively through a cooling circulating water pipeline.

Description

Technical Field

[0001] The present invention relates to the technical field of waste heat utilization, and particularly to a comprehensive waste heat utilization system for flue gas in an ammonia-based carbon dioxide removal process for industrial flue gas. Background Art

[0002] The production of ammonium bicarbonate by ammonia-based carbon dioxide removal is a mature process commonly used in small nitrogen fertilizer plants in the 1960s. Since ammonium bicarbonate is prone to decomposition at temperatures above 30°C, it is necessary to reduce the flue gas temperature and control the temperature of the absorption liquid in the carbonation tower below 30°C during the production process. Generally, the temperature of industrial flue gas is relatively high, about 130 - 200°C, and it needs to be cooled before entering the ammonia-based carbon dioxide removal tower. The ammonia-based carbon dioxide removal process for industrial flue gas is still in its primary stage and has not been widely applied industrially. In existing technologies, generally, the flue gas after wet desulfurization, with a temperature of about 50 - 60°C, is further cooled to below 30°C using the chilled water of a refrigeration unit; in the case of no wet desulfurization device, direct water washing is usually used to cool the flue gas directly to about 50°C, and then the chilled water of the refrigeration unit is used to further reduce the flue gas temperature to below 30°C; there is also a technology that uses a heat pump to collect the waste heat of the flue gas to produce hot water for use in the factory area.

[0003] In existing technologies, the wet desulfurization device or direct water washing process is usually used for ammonia-based carbon dioxide removal of industrial flue gas. The method is single, and the waste heat of the flue gas is not fully utilized, resulting in energy waste; while the technology of using a heat pump to produce hot water does not consider the actual needs of the enterprise, and often the produced hot water cannot be consumed, resulting in a waste. Therefore, it is still necessary to improve the waste heat utilization system for the ammonia-based carbon dioxide removal process. Summary of the Invention

[0004] The purpose of the present invention is to provide a comprehensive waste heat utilization system for flue gas in an ammonia-based carbon dioxide removal process for industrial flue gas to solve the above problems in the background art. The present invention uses a multi-stage cooling heat exchanger for stepped heat exchange. Part of the exchanged heat is used as the driving heat source for a lithium bromide refrigeration machine, and part is used to raise the temperature of the low-temperature clean flue gas discharged from the ammonia-based carbon dioxide removal tower, which is beneficial to the external discharge of the clean flue gas and thus eliminates the problem of white smoke; the chilled water produced by the lithium bromide refrigeration machine passes through the multi-stage cooling heat exchanger to further reduce the temperature of the original flue gas to below 30°C required for ammonia-based carbon dioxide removal, and the excess chilled water is used to absorb the reaction heat in the ammonia-based carbon dioxide removal tower. This system makes full use of the waste heat of the flue gas and saves the comprehensive energy consumption of the ammonia-based carbon dioxide removal process.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] One technical solution of the present invention: Provide an ammonia-based carbon dioxide removal and waste heat comprehensive utilization system for industrial flue gas, including a lithium bromide refrigeration machine and a three-stage cooling heat exchanger, a booster fan, a four-stage cooling heat exchanger, an ammonia-based carbon dioxide removal tower, and a temperature-raising heat exchanger connected in sequence;

[0007] The heating heat exchanger is circularly and communicatively connected to the first-stage heat exchange device of the third-stage cooling heat exchanger and the first-stage heat exchange device of the fourth-stage cooling heat exchanger respectively through a primary circulating water pipeline;

[0008] The lithium bromide refrigerating machine is circularly and communicatively connected to the second-stage heat exchange device of the third-stage cooling heat exchanger and the second-stage heat exchange device of the fourth-stage cooling heat exchanger respectively through a secondary circulating water pipeline;

[0009] The lithium bromide refrigerating machine is circularly and communicatively connected to the fourth-stage heat exchange device of the fourth-stage cooling heat exchanger and the ammonia method decarbonization tower respectively through a cooling circulating water pipeline.

[0010] Preferably, a primary hot water circulating pump is arranged on the primary circulating water pipeline; a secondary hot water circulating pump is arranged on the secondary circulating water pipeline; and a cold water circulating pump is arranged on the cooling circulating water pipeline.

[0011] Preferably, the shells of the third-stage cooling heat exchanger and the fourth-stage cooling heat exchanger adopt a circular tube high-pressure resistant structure, and the tube side adopts a serpentine coiled tube.

[0012] The second technical solution of the present invention: provides an industrial flue gas treatment method based on the above industrial flue gas ammonia method decarbonization and waste heat comprehensive utilization system, including the following steps:

[0013] The industrial flue gas is introduced into the third-stage cooling heat exchanger for cooling, then introduced into a booster fan for pressurization to obtain pressurized flue gas, then introduced into the fourth-stage cooling heat exchanger to obtain low-temperature flue gas, and then enters the ammonia method decarbonization tower for decarbonization; the low-temperature clean flue gas obtained after decarbonization is introduced into the heating heat exchanger for heating to obtain treated flue gas, and then discharged.

[0014] Preferably, the temperature of the industrial flue gas is 130 - 200 °C.

[0015] Preferably, the temperature rise of the pressurized flue gas is 80 - 90 °C.

[0016] More preferably, the pressure of the pressurization is 160 KPa.

[0017] Preferably, the temperature of the treated flue gas ≥ 90 °C.

[0018] Preferably, the temperature of the low-temperature flue gas ≤ 30 °C.

[0019] More preferably, the temperature of the low-temperature flue gas is 20 °C.

[0020] Preferably, the industrial flue gas treatment method further includes primary circulating water treatment; the primary circulating water treatment includes the following steps:

[0021] After the primary circulating water is heated successively through the first-stage heat exchange stage of the three-stage cooling heat exchanger and the first-stage heat exchange stage of the four-stage cooling heat exchanger, it is pumped by the primary hot water circulation pump into the heating heat exchanger to heat the clean flue gas. Then, the primary circulating water after heat release is re-introduced into the first-stage heat exchange stage of the three-stage cooling heat exchanger and the first-stage heat exchange stage of the four-stage cooling heat exchanger, and circulates reciprocally.

[0022] Preferably, the industrial flue gas treatment method further includes secondary circulating water treatment; the secondary circulating water treatment includes the following steps:

[0023] After the secondary circulating water is heated successively through the second-stage heat exchange stage of the three-stage cooling heat exchanger and the second-stage heat exchange stage of the four-stage cooling heat exchanger, it is pumped by the secondary hot water circulation pump into the lithium bromide refrigerator to serve as the driving heat source of the lithium bromide refrigerator. Then, the secondary circulating water after heat release is re-introduced into the second-stage heat exchange stage of the three-stage cooling heat exchanger and the second-stage heat exchange stage of the four-stage cooling heat exchanger, and circulates reciprocally.

[0024] Preferably, the industrial flue gas treatment method further includes circulating cooling water treatment; the circulating cooling water treatment includes the following steps:

[0025] The circulating cooling water supplied from the plant area is heat-exchanged successively through the third-stage heat exchange stage of the three-stage cooling heat exchanger and the third-stage heat exchange stage of the four-stage cooling heat exchanger, and then the return water of the circulating cooling water after temperature rise is discharged.

[0026] Preferably, the industrial flue gas treatment method further includes chilled water treatment; the chilled water treatment includes the following steps:

[0027] The chilled water produced by the lithium bromide refrigerator is pumped by the chilled water circulation pump to the fourth-stage heat exchange stage of the four-stage cooling heat exchanger to further reduce the flue gas temperature and absorb the reaction heat in the ammonia-based decarbonization tower. Then, the chilled water after heat absorption is re-introduced into the lithium bromide refrigerator, and circulates reciprocally.

[0028] The beneficial technical effects of the present invention are as follows:

[0029] The present invention adopts a stepped heat exchange of a multi-stage cooling heat exchanger. A part of the heat exchanged is used as the driving heat source of the lithium bromide refrigerator, and a part is used to raise the temperature of the low-temperature clean flue gas discharged from the ammonia-based decarbonization tower, which is beneficial to the external discharge of the clean flue gas, thus eliminating the problem of white smoke. The chilled water produced by the lithium bromide refrigerator passes through the multi-stage cooling heat exchanger to further reduce the temperature of the original flue gas to below 30°C required for ammonia-based decarbonization, and the excess chilled water is used to absorb the reaction heat in the ammonia-based decarbonization tower. This system makes full use of the waste heat of the flue gas and saves the comprehensive energy consumption of the ammonia-based decarbonization process. Description of the Drawings

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a schematic structural diagram of the industrial flue gas ammonia-based decarbonization and waste heat comprehensive utilization system for Embodiment 1. Detailed implementation manners

[0032] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention.

[0033] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0034] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention.

[0035] Regarding the use of "comprising", "including", "having", "containing", etc. in the present invention, they are all open-ended terms, meaning including but not limited to.

[0036] The present invention provides an industrial flue gas ammonia-based decarbonization and waste heat comprehensive utilization system, including a flue gas system and a waste heat comprehensive utilization system;

[0037] The flue gas system includes the following devices: a three-stage cooling heat exchanger, a booster fan, a four-stage cooling heat exchanger, an ammonia-based decarbonization tower, and a heating heat exchanger;

[0038] The waste heat comprehensive utilization system includes the following devices: a primary hot water circulation pump, a secondary hot water circulation pump, a lithium bromide refrigerator, and a cold water circulation pump;

[0039] Flue gas system: After the industrial flue gas is dust-removed by a dust collector, the dust-removed industrial flue gas obtained is introduced into a three-stage cooling heat exchanger. The cooled flue gas enters a booster fan for pressurization (after pressurization by the booster fan, the temperature of the flue gas will increase by 80 - 90 °C). Then the flue gas is introduced into a four-stage cooling heat exchanger, and then enters an ammonia-based decarbonization tower for decarbonization; the low-temperature clean flue gas obtained after decarbonization is introduced into a heating heat exchanger to heat the clean flue gas to above 90 °C, and finally is discharged through a chimney;

[0040] Primary hot water circulation system: After the primary circulating water is heated through the first heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger, it is transported to the heating heat exchanger by a primary hot water circulation pump for heating the clean flue gas. Then the primary circulating water after releasing heat is re-introduced into the first heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger for reciprocating circulation;

[0041] Secondary hot water circulation system: After the secondary circulating water is heated through the second heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger, it is transported to a lithium bromide refrigerating machine by a secondary hot water circulation pump to be used as the driving heat source of the lithium bromide refrigerating machine. Then the secondary circulating water after releasing heat is re-introduced into the second heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger for reciprocating circulation;

[0042] Circulating cooling water system: After the circulating cooling water supply from the factory area is heat-exchanged through the third heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger, the temperature of the flue gas is reduced to about 50 °C. Then the circulating cooling water return water after temperature rise is discharged and re-transported back to the factory area circulating cooling water system;

[0043] Chilled water circulation system: The chilled water produced by the lithium bromide refrigerating machine is transported to the fourth heat exchange stage of the four-stage cooling heat exchanger by a chilled water circulation pump to further reduce the temperature of the flue gas to below 30 °C and absorb the reaction heat in the ammonia-based decarbonization tower. Then the chilled water after absorbing heat is re-introduced into the lithium bromide refrigerating machine for reciprocating circulation.

[0044] The parameters of the industrial flue gas (lime kiln flue gas) used in the present invention are shown in Table 1.

[0045] Table 1

[0046]

[0047]

[0048] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0049] Example 1

[0050] An industrial flue gas ammonia-based decarbonization and waste heat comprehensive utilization system consists of a flue gas system and a waste heat comprehensive utilization system;

[0051] Among them, the flue gas system consists of the following devices: a three-stage cooling heat exchanger, a booster fan, a four-stage cooling heat exchanger, an ammonia-based decarbonization tower, and a heating heat exchanger;

[0052] The waste heat comprehensive utilization system consists of the following devices: a primary hot water circulation pump, a secondary hot water circulation pump, a lithium bromide refrigerator, and a chilled water circulation pump.

[0053] Flue gas system: After the industrial flue gas is dust-removed by the dust collector, the dust-removed industrial flue gas obtained is introduced into the three-stage cooling heat exchanger. The cooled flue gas enters the booster fan for pressurization, and then the flue gas is introduced into the four-stage cooling heat exchanger, and then enters the ammonia-based decarbonization tower for decarbonization; the low-temperature clean flue gas obtained after decarbonization is introduced into the heating heat exchanger and finally discharged through the chimney.

[0054] Primary hot water circulation system: After the primary circulating water is heated through the first-stage heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger, it is transported to the heating heat exchanger by the primary hot water circulation pump for heating the clean flue gas, and then the primary circulating water after releasing heat is re-introduced into the first-stage heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger for reciprocating circulation.

[0055] Secondary hot water circulation system: After the secondary circulating water is heated through the second-stage heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger, it is transported to the lithium bromide refrigerator by the secondary hot water circulation pump as the driving heat source of the lithium bromide refrigerator, and then the secondary circulating water after releasing heat is re-introduced into the second-stage heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger for reciprocating circulation.

[0056] Circulating cooling water system: After the circulating cooling water supply from the plant area is heat-exchanged through the third-stage heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger, the heated circulating cooling water return water is then discharged and re-transported back to the plant area circulating cooling water system.

[0057] Chilled water circulation system: The chilled water produced by the lithium bromide refrigerator is transported to the fourth-stage heat exchange stage of the four-stage cooling heat exchanger by the chilled water circulation pump to further reduce the flue gas temperature and absorb the reaction heat in the ammonia-based decarbonization tower, and then the chilled water after absorbing heat is re-introduced into the lithium bromide refrigerator for reciprocating circulation.

[0058] Among them, the relevant parameters of the three-stage cooling heat exchanger and the booster fan are shown in Table 2, the relevant parameters of the four-stage cooling heat exchanger are shown in Table 3, and the relevant parameters of the heating heat exchanger and the lithium bromide refrigerator are shown in Table 4.

[0059] Table 2

[0060]

[0061] Table 3

[0062]

[0063] Table 4

[0064]

[0065] As can be seen from Table 2-4, the primary heat exchanger can produce 40.75 t / h of hot water and heat the clean flue gas from 20°C to 97°C; the secondary heat exchanger can produce 150 t / h of hot water, which is used as the driving heat source for the lithium bromide refrigerating machine, and can produce 325 t / h of chilled water at 7°C; the produced chilled water can cool the flue gas in the fourth heat exchange stage of the fourth-stage cooling heat exchanger from 50°C to 20°C, meeting the process requirements of ammonia-based decarbonization. Compared with directly washing and cooling industrial flue gas, about 4670 KW of heat in the industrial flue gas is collected in this embodiment, achieving the purpose of energy conservation and consumption reduction.

[0066] Figure 1 It is a schematic structural diagram of the ammonia-based decarbonization and waste heat comprehensive utilization system for industrial flue gas in Embodiment 1.

[0067] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. An industrial flue gas ammonia decarbonization and waste heat comprehensive utilization system, characterized in that: It includes a lithium bromide refrigerator and a three-stage cooling heat exchanger, a booster fan, a four-stage cooling heat exchanger, an ammonia decarbonization tower and a heating heat exchanger connected in sequence; The temperature-raising heat exchanger is cyclically connected to the first-stage heat exchange device of the three-stage temperature-reducing heat exchanger and the first-stage heat exchange device of the four-stage temperature-reducing heat exchanger through a primary circulating water pipeline; The lithium bromide refrigerator is in circulation communication with the second stage heat exchange device of the three-stage cooling heat exchanger and the second stage heat exchange device of the four-stage cooling heat exchanger through a secondary circulating water pipeline; The lithium bromide refrigerator is cyclically connected to the fourth-stage heat exchange device of the four-stage cooling heat exchanger and the ammonia decarbonization tower through a cooling circulating water pipeline.

2. An industrial flue gas treatment method based on the industrial flue gas ammonia decarbonization and waste heat comprehensive utilization system according to claim 1, characterized in that: The following steps are involved: The industrial flue gas is passed through a three-stage cooling heat exchanger for cooling, then passed through a booster fan for pressurization to obtain pressurized flue gas, and then passed through a four-stage cooling heat exchanger to obtain low-temperature flue gas, and then enters an ammonia decarbonization tower for decarbonization; the low-temperature clean flue gas obtained after decarbonization is passed through a heating heat exchanger for heating to obtain treated flue gas, which is then discharged.

3. The industrial flue gas treatment method according to claim 2, characterized in that: The temperature of the industrial flue gas is 130-200°C.

4. The industrial flue gas treatment method according to claim 2, characterized in that: The temperature rise of the pressurized flue gas is 80-90°C.

5. The industrial flue gas treatment method according to claim 2, characterized in that: The temperature of the treated flue gas is ≥90°C.

6. The industrial flue gas treatment method according to claim 2, characterized in that: The temperature of the low-temperature flue gas is ≤30°C.

7. The industrial flue gas treatment method according to claim 2, characterized in that: The industrial flue gas treatment method further comprises a primary circulating water treatment; the primary circulating water treatment comprises the following steps: The primary circulating water is heated in the first heat exchange stage of the three-stage cooling heat exchanger and the first heat exchange stage of the four-stage cooling heat exchanger in turn, and then transported to the heating heat exchanger through the first hot water circulation pump to heat the clean flue gas. The heat-released primary circulating water is then re-introduced into the first heat exchange stage of the three-stage cooling heat exchanger and the first heat exchange stage of the four-stage cooling heat exchanger for a reciprocating cycle.

8. The industrial flue gas treatment method according to claim 2, characterized in that: The industrial flue gas treatment method further comprises secondary circulating water treatment; the secondary circulating water treatment comprises the following steps: The secondary circulating water is heated in the second stage heat exchange of the three-stage cooling heat exchanger and the second stage heat exchange of the four-stage cooling heat exchanger in turn, and then transported to the lithium bromide refrigerator through the secondary hot water circulation pump to be used as the driving heat source of the lithium bromide refrigerator. Then the secondary circulating water after releasing heat is re-introduced into the second stage heat exchange of the three-stage cooling heat exchanger and the second stage heat exchange of the four-stage cooling heat exchanger, and the cycle is repeated.

9. The industrial flue gas treatment method according to claim 2, characterized in that: The industrial flue gas treatment method further comprises circulating cooling water treatment; the circulating cooling water treatment comprises the following steps: The circulating cooling water feed water from the factory area is sequentially heat exchanged through the third stage heat exchange stage of the three-stage cooling heat exchanger and the third stage heat exchange stage of the four-stage cooling heat exchanger, and then the heated circulating cooling water return water is discharged.

10. The industrial flue gas treatment method according to claim 2, characterized in that: The industrial flue gas treatment method further comprises chilled water treatment; the chilled water treatment comprises the following steps: The chilled water taken from the lithium bromide refrigerator is transported to the fourth heat exchange stage of the four-stage cooling heat exchanger through a cold water circulation pump to further reduce the flue gas temperature and absorb the reaction heat in the ammonia decarbonization tower. The chilled water after absorbing heat is then re-introduced into the lithium bromide refrigerator for a reciprocating cycle.

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