Comprehensive utilization system for flue gas waste heat of industrial flue gas ammonia decarburization process

Abstract

The invention discloses a flue gas waste heat comprehensive utilization system for an industrial flue gas ammonia decarburization process, and belongs to the technical field of waste heat utilization. The invention discloses an industrial flue gas ammonia process decarburization and waste heat comprehensive utilization system. The system comprises a lithium bromide refrigerator, and a three-stage cooling heat exchanger, a booster fan, a four-stage cooling heat exchanger, an ammonia process decarburization tower and a heating heat exchanger which are communicated in sequence, the heating heat exchanger is respectively and circularly communicated with a first-stage heat exchange device of the third-stage cooling heat exchanger and a first-stage heat exchange device of the fourth-stage cooling heat exchanger through a first-stage circulating water pipeline; the lithium bromide refrigerator is respectively and circularly communicated with a second-stage heat exchange device of the third-stage cooling heat exchanger and a second-stage heat exchange device of the fourth-stage cooling heat exchanger through a second-stage circulating water pipeline; and the lithium bromide refrigerator is respectively and circularly communicated with a fourth-stage stage heat exchange device of the four-stage cooling heat exchanger and the ammonia process decarburization tower through a cooling circulating water pipeline.

Description

Technical Field

[0001] The invention relates to the technical field of waste heat utilization, and in particular to a system for comprehensively utilizing waste heat from flue gas in an industrial flue gas ammonia decarbonization process. Background Art

[0002] The ammonia decarbonization process to produce ammonium bicarbonate was a mature process commonly used by small nitrogen fertilizer plants in the 1960s. Since ammonium bicarbonate is easily decomposed when the temperature is greater than 30°C, it is necessary to reduce the flue gas temperature and control the temperature of the carbonization tower absorption liquid 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 decarbonization tower. The ammonia decarbonization process for industrial flue gas is still in its early stages and has no large-scale industrial application. The existing technology generally selects the flue gas after wet desulfurization, with a temperature of about 50-60°C, and then further uses the cold water of the refrigeration unit to cool it down to below 30°C; when there is no wet desulfurization device, water washing is usually used to directly cool it down to about 50°C, and then the chilled water of the refrigeration unit is further used to reduce the flue gas temperature to below 30°C; there are also heat pump technology to collect the waste heat of the flue gas to produce hot water for domestic water in the factory area.

[0003] The existing technology usually adopts wet desulfurization device or direct water washing process to carry out industrial flue gas ammonia decarbonization. The method is single and does not make full use of the waste heat of flue gas, resulting in energy waste; while the technology of using heat pump to produce hot water does not consider the actual needs of the enterprise, and the produced hot water is often not consumed and wasted. Therefore, there is still a need to improve the waste heat utilization system of the ammonia decarbonization process. Summary of the invention

[0004] The purpose of the present invention is to provide a system for comprehensive utilization of flue gas waste heat in the ammonia decarbonization process of industrial flue gas, so as to solve the above-mentioned problems in the background technology. The present invention adopts a multi-stage cooling heat exchanger for step-by-step heat exchange. Part of the heat exchanged is used as the driving heat source of the lithium bromide refrigerator, and part of it is used to heat the low-temperature clean flue gas discharged from the ammonia decarbonization tower, which is beneficial to the discharge of clean flue gas, thereby eliminating the problem of white smoke; the chilled water taken by the lithium bromide refrigerator passes through the multi-stage cooling heat exchanger to further reduce the original flue gas temperature to below 30°C required for ammonia decarbonization, and the excess chilled water is used to absorb the reaction heat in the ammonia decarbonization tower. The system makes full use of the waste heat of the flue gas and saves the comprehensive energy consumption of the ammonia decarbonization process.

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

[0006] One of the technical solutions of the present invention is to provide an industrial flue gas ammonia decarbonization and waste heat comprehensive utilization system, including 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;

[0007] 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;

[0008] 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;

[0009] 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.

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

[0011] Preferably, the shells of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger adopt a round tube high-pressure resistant structure, and the tube pass adopts a serpentine coil.

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

[0013] 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.

[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 pressurized pressure is 160 KPa.

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

[0018] Preferably, the temperature of the low-temperature flue gas is ≤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 comprises a primary circulating water treatment; the primary circulating water treatment comprises the following steps:

[0021] 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.

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

[0023] 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.

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

[0025] 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.

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

[0027] 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.

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

[0029] The present invention adopts a multi-stage cooling heat exchanger for step-by-step heat exchange. Part of the heat exchanged is used as the driving heat source of the lithium bromide refrigerator, and part is used to heat the low-temperature clean flue gas discharged from the ammonia decarbonization tower, which is conducive to the discharge of clean flue gas, thereby eliminating the problem of white smoke; the chilled water taken by the lithium bromide refrigerator passes through the multi-stage cooling heat exchanger to further reduce the original flue gas temperature to below 30°C required for ammonia decarbonization, and the excess chilled water is used to absorb the reaction heat in the ammonia decarbonization tower. The system makes full use of the waste heat of the flue gas and saves the comprehensive energy consumption of the ammonia decarbonization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments 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 work.

[0031] Figure 1 This is a schematic diagram of the structure of the industrial flue gas ammonia decarbonization and waste heat comprehensive utilization system of Example 1. DETAILED DESCRIPTION

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

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

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

[0035] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0036] The present invention provides an industrial flue gas ammonia 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 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 dedusted by the dust collector, the dedusted industrial flue gas is passed into the three-stage cooling heat exchanger, and the cooled flue gas enters the booster fan for pressurization (after pressurization by the booster fan, the temperature of the flue gas will increase by 80-90°C), and then the flue gas is passed into the four-stage cooling heat exchanger, and then enters the ammonia decarbonization tower for decarbonization; the low-temperature clean flue gas obtained after decarbonization is passed into the heating heat exchanger to heat the clean flue gas to above 90°C, and finally passed into the chimney for discharge;

[0040] Primary hot water circulation system: After the primary circulating water is heated in 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 through the primary hot water circulation pump to heat the clean flue gas, and then the primary circulating water after heat release is re-introduced into the first heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger, and the cycle is repeated;

[0041] Secondary hot water circulation system: After the secondary circulating water is heated in the second stage heat exchange of the third stage cooling heat exchanger and the fourth stage cooling heat exchanger, it is 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 heat release is re-introduced into the second stage heat exchange of the third stage cooling heat exchanger and the fourth stage cooling heat exchanger, and the cycle is repeated;

[0042] Circulating cooling water system: The circulating cooling water from the plant area is heat exchanged in the third stage of the three-stage cooling heat exchanger and the fourth-stage cooling heat exchanger to reduce the flue gas temperature to about 50°C, and then the heated circulating cooling water return water is discharged and re-transported to the circulating cooling water system of the plant area;

[0043] Chilled water circulation system: 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, further reducing the flue gas temperature to below 30°C and absorbing the reaction heat in the ammonia decarbonization tower. The heat-absorbed chilled water is then re-introduced into the lithium bromide refrigerator for a reciprocating cycle.

[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 decarbonization and waste heat comprehensive utilization system, consisting of a flue gas system and a waste heat comprehensive utilization system;

[0051] Among them, the flue gas system consists of the following devices: three-stage cooling heat exchanger, booster fan, four-stage cooling heat exchanger, ammonia decarbonization tower and 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 cold water circulation pump.

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

[0054] Primary hot water circulation system: After the primary circulating water is heated in 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 through the primary hot water circulation pump to heat the clean flue gas, and then the primary circulating water after heat release is re-introduced into the first heat exchange stage of the three-stage cooling heat exchanger and the four-stage cooling heat exchanger, and the cycle is repeated.

[0055] Secondary hot water circulation system: After the secondary circulating water is heated in the second stage of heat exchange of the tertiary cooling heat exchanger and the quaternary cooling heat exchanger, it is 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. The secondary circulating water after heat release is then re-introduced into the second stage of heat exchange of the tertiary cooling heat exchanger and the quaternary cooling heat exchanger for a reciprocating cycle.

[0056] Circulating cooling water system: The circulating cooling water supply from the factory is passed through the third stage of heat exchange of the three-stage cooling heat exchanger and the fourth-stage cooling heat exchanger, and then the heated circulating cooling water return water is discharged and re-introduced into the factory circulating cooling water system.

[0057] Chilled water circulation system: 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 heat-absorbed chilled water is then re-introduced into the lithium bromide refrigerator for a reciprocating cycle.

[0058] 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 lithium bromide refrigerator are shown in Table 4.

[0059] Table 2

[0060]

[0061] Table 3

[0062]

[0063] Table 4

[0064]

[0065] As shown in Table 2-4, the first-stage heat exchanger can produce 40.75t / h of hot water, which can heat the clean flue gas from 20℃ to 97℃; the second-stage heat exchanger can produce 150t / h of hot water, which is used as the driving heat source of the lithium bromide refrigerator, and can produce 325t / h of chilled water at 7℃; the produced chilled water can reduce the flue gas in the fourth stage of the heat exchange stage of the four-stage cooling heat exchanger from 50℃ to 20℃, meeting the process requirements of ammonia decarbonization. Compared with direct water washing and cooling of industrial flue gas, this embodiment collects a total of about 4670KW of heat in the industrial flue gas, achieving the purpose of energy saving and consumption reduction.

[0066] Figure 1 This is a schematic diagram of the structure of the industrial flue gas ammonia decarbonization and waste heat comprehensive utilization system of Example 1.

[0067] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all 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 a 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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