A device and method for cascade utilization of flue gas waste heat with simultaneous capture of carbon and sulfur

Abstract

The present invention relates to the field of carbon and sulfur capture, and specifically to a cascaded utilization device and method for flue gas waste heat that simultaneously captures carbon and sulfur. The device comprises a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger, a seventh heat exchanger, an absorption tower, a sulfur dioxide desorption tower, and a carbon dioxide desorption tower. The device utilizes heat network return water as a cold source, reducing the amount and consumption of circulating cooling water. The desorption towers at different temperatures achieve the separate removal and capture of carbon dioxide and sulfur dioxide. The cascaded cooling of the flue gas and the cascaded heating of the heat network return water lower the flue gas temperature entering the absorption tower and increase the carbon dioxide absorption capacity. Simultaneously, the cascaded utilization of flue gas waste heat is achieved, improving heat utilization efficiency and heating benefits. The cascaded cooling of the ionic liquid enables the effective recycling of the ionic liquid.

Description

Technical Field

[0001] The present invention relates to the field of carbon and sulfur capture, and in particular to a flue gas waste heat cascade utilization device and method for simultaneously capturing carbon and sulfur. Background Art

[0002] A sharp increase in carbon dioxide concentrations can trigger a severe greenhouse effect, leading to severe global warming and associated natural disasters, glacier melt, and extreme weather. The development and application of carbon dioxide capture plays an important role in mitigating global warming and has therefore attracted significant attention.

[0003] Similarly, sulfur dioxide produced by the combustion of fossil fuels poses a serious threat to human health and the ecological environment. How to effectively capture sulfur dioxide has attracted widespread attention from scholars at home and abroad. Although there is carbon dioxide capture technology, the existing technology does not involve the capture of sulfur in flue gas. Although the existing technology can achieve a certain recovery and preheating purpose, the heat recovery rate is very low and the consumption of circulating cooling water is relatively high. Summary of the Invention

[0004] The present invention proposes a flue gas waste heat cascade utilization device and method for simultaneously capturing carbon and sulfur, in order to solve the problems that the prior art does not involve the capture of sulfur in flue gas, has a low heat recovery rate, and provides low water temperature in the hot network.

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

[0006] A flue gas waste heat cascade utilization device for simultaneously capturing carbon and sulfur, comprising a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger, a seventh heat exchanger, an absorption tower, a sulfur dioxide desorption tower, and a carbon dioxide desorption tower;

[0007] The first heat exchanger is provided with a first heat exchanger flue gas inlet, a first heat exchanger flue gas outlet and a first heat exchanger hot network water inlet;

[0008] The second heat exchanger is provided with a second heat exchanger flue gas inlet, a second heat exchanger flue gas outlet, a second heat exchanger ionic liquid inlet and a second heat exchanger ionic liquid outlet;

[0009] The third heat exchanger is provided with a third heat exchanger flue gas inlet, a third heat exchanger flue gas outlet, a third heat exchanger ionic liquid inlet and a third heat exchanger ionic liquid outlet;

[0010] The fourth heat exchanger is provided with a fourth heat exchanger hot network water inlet, a fourth heat exchanger hot network water outlet, a fourth heat exchanger ionic liquid inlet and a fourth heat exchanger ionic liquid outlet;

[0011] The fifth heat exchanger is provided with a fifth heat exchanger hot network water inlet, a fifth heat exchanger hot network water outlet, a fifth heat exchanger carbon dioxide inlet and a fifth heat exchanger carbon dioxide outlet;

[0012] The sixth heat exchanger is provided with a sixth heat exchanger hot network water inlet, a sixth heat exchanger hot network water outlet, a sixth heat exchanger sulfur dioxide inlet and a sixth heat exchanger sulfur dioxide outlet.

[0013] The seventh heat exchanger is provided with a seventh heat exchanger hot network water inlet, a seventh heat exchanger hot network water outlet, a seventh heat exchanger ionic liquid inlet, and a seventh heat exchanger ionic liquid outlet;

[0014] The absorption tower is provided with an absorption tower flue gas inlet, an absorption tower flue gas outlet, an absorption tower ionic liquid inlet, and an absorption tower ionic liquid outlet;

[0015] The sulfur dioxide desorption tower is provided with a sulfur dioxide desorption tower ionic liquid inlet, a desorption tower sulfur dioxide outlet, and a sulfur dioxide desorption tower ionic liquid outlet;

[0016] The carbon dioxide desorption tower is provided with a carbon dioxide desorption tower ionic liquid inlet, a desorption tower carbon dioxide outlet, and a carbon dioxide desorption tower ionic liquid outlet;

[0017] The water inlet of the first heat exchanger is connected to the water outlet of the fourth heat exchanger, the flue gas outlet of the first heat exchanger is connected to the flue gas inlet of the second heat exchanger, the flue gas outlet of the second heat exchanger is connected to the flue gas inlet of the third heat exchanger, the flue gas outlet of the third heat exchanger is connected to the flue gas inlet of the absorption tower, the ionic liquid inlet of the absorption tower is connected to the ionic liquid outlet of the seventh heat exchanger, the ionic liquid outlet of the absorption tower is connected to the ionic liquid inlet of the third heat exchanger, the ionic liquid outlet of the third heat exchanger is connected to the ionic liquid inlet of the sulfur dioxide desorption tower, the sulfur dioxide outlet of the desorption tower is connected to the sulfur dioxide inlet of the sixth heat exchanger, and the ionic liquid inlet of the sulfur dioxide desorption tower is connected to the ionic liquid inlet of the sixth heat exchanger. The liquid outlet is connected to the ionic liquid inlet of the second heat exchanger, the ionic liquid outlet of the second heat exchanger is connected to the ionic liquid inlet of the carbon dioxide desorption tower, the carbon dioxide outlet of the desorption tower is connected to the carbon dioxide inlet of the fifth heat exchanger, the ionic liquid outlet of the carbon dioxide desorption tower is connected to the ionic liquid inlet of the fourth heat exchanger, the ionic liquid outlet of the fourth heat exchanger is connected to the ionic liquid inlet of the seventh heat exchanger, the hot network water outlet of the seventh heat exchanger is connected to the hot network water inlet of the sixth heat exchanger, the hot network water outlet of the sixth heat exchanger is connected to the hot network water inlet of the fifth heat exchanger, and the hot network water outlet of the fifth heat exchanger is connected to the hot network water inlet of the fourth heat exchanger.

[0018] Preferably, the fifth heat exchanger is provided with a fifth heat exchanger carbon dioxide outlet.

[0019] Preferably, the sixth heat exchanger is provided with a sixth heat exchanger sulfur dioxide outlet.

[0020] Preferably, the carbon dioxide outlet of the fifth heat exchanger is connected to a carbon dioxide storage tank.

[0021] Preferably, the sulfur dioxide outlet of the sixth heat exchanger is connected to a sulfur dioxide storage tank.

[0022] Preferably, the water outlet of the first heat exchanger is connected to the heating network.

[0023] Preferably, the sulfur dioxide outlet of the desorption tower is located at the top of the sulfur dioxide desorption tower, and the ionic liquid outlet of the sulfur dioxide desorption tower is located at the bottom of the sulfur dioxide desorption tower.

[0024] Preferably, the carbon dioxide outlet of the desorption tower is arranged at the top of the carbon dioxide desorption tower, and the ionic liquid outlet of the carbon dioxide desorption tower is arranged at the bottom of the carbon dioxide desorption tower.

[0025] A method for cascade utilization of flue gas waste heat with simultaneous capture of carbon and sulfur, comprising the following steps:

[0026] The flue gas enters the first heat exchanger and exchanges heat with the water in the heating network. The flue gas cools down and the water in the heating network heats up. After the flue gas cools down, it enters the second heat exchanger and exchanges heat with the ionic liquid in the second heat exchanger. The flue gas cools down and the ionic liquid heats up. After the flue gas cools down, it enters the third heat exchanger and exchanges heat with the ionic liquid in the third heat exchanger. The flue gas cools down and the ionic liquid heats up.

[0027] After the flue gas is cooled, it enters the absorption tower, where it contacts the ionic liquid. The ionic liquid absorbs carbon dioxide and sulfur dioxide in the flue gas. The ionic liquid rich in carbon dioxide and sulfur dioxide enters the third heat exchanger, and the remaining flue gas is discharged into the chimney. The ionic liquid rich in carbon dioxide and sulfur dioxide exchanges heat with the flue gas in the third heat exchanger. After the ionic liquid is heated, it enters the sulfur dioxide desorption tower. The ionic liquid rich in carbon dioxide and sulfur dioxide desorbs in the sulfur dioxide desorption tower, and the desorbed sulfur dioxide enters the sixth heat exchanger. The carbon dioxide-rich and sulfur dioxide-poor ionic liquid enters the second heat exchanger, where it exchanges heat with the flue gas. After the ionic liquid is heated, it enters the carbon dioxide desorption tower, where the ionic liquid is desorbed. The desorbed carbon dioxide enters the fifth heat exchanger. The desorbed carbon dioxide-poor and sulfur dioxide-poor ionic liquid enters the fourth heat exchanger to exchange heat with the heating network water. The ionic liquid cools down, while the heating network water heats up. The ionic liquid in the fourth heat exchanger cools down and enters the seventh heat exchanger. The heating network water heats up and enters the first heat exchanger.

[0028] The hot network water enters the seventh heat exchanger, and the hot network water in the seventh heat exchanger exchanges heat with the ionic liquid from the fourth heat exchanger. The hot network water is heated, and the ionic liquid is cooled. The cooled ionic liquid enters the absorption tower. The heated hot network water enters the sixth heat exchanger, and the sulfur dioxide in the sixth heat exchanger exchanges heat with the hot network water. The hot network water is heated, and the sulfur dioxide is cooled. The cooled sulfur dioxide enters the sulfur dioxide storage tank. The heated hot network water enters the fifth heat exchanger, and the carbon dioxide in the fifth heat exchanger exchanges heat with the hot network water. The carbon dioxide enters the carbon dioxide storage tank after cooling. The hot network water enters the fourth heat exchanger after heating.

[0029] In the first heat exchanger, the hot network water exchanges heat with the flue gas, the hot network water is heated up, the flue gas is cooled down, and the hot network water enters the hot network after being heated up.

[0030] Preferably, after the hot network water exchanges heat with the flue gas in the first heat exchanger, the temperature of the hot network water is greater than 100 degrees Celsius and less than 130 degrees Celsius.

[0031] The present invention is beneficial in that:

[0032] At the same time, carbon dioxide and sulfur dioxide in flue gas are captured.

[0033] Through the cascade cooling of flue gas and the five-stage cascade heating of heat network return water, the cascade utilization of flue gas waste heat and the full recovery and utilization of heavy heat in the desorption process are realized, thereby improving the heat utilization efficiency.

[0034] By recycling the waste heat in the flue gas, the heating income is increased and the economic benefits of the power plant are improved.

[0035] By using the return water from the heat network as the cold source, the usage and consumption of circulating cooling water is reduced, achieving a certain water-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0037] Figure 1 This is a schematic diagram of a flue gas waste heat cascade utilization device that simultaneously captures carbon and sulfur.

[0038] In the figure, 1 is the first heat exchanger, 2 is the second heat exchanger, 3 is the third heat exchanger, 4 is the fourth heat exchanger, 5 is the fifth heat exchanger, 6 is the sixth heat exchanger, 7 is the seventh heat exchanger, 8 is the absorption tower, 9 is the sulfur dioxide desorption tower, and 10 is the carbon dioxide desorption tower;

[0039] 11 is the flue gas inlet of the first heat exchanger, 12 is the flue gas outlet of the first heat exchanger, 13 is the water inlet of the hot network of the first heat exchanger, and 14 is the water outlet of the hot network of the first heat exchanger;

[0040] 21 is the flue gas inlet of the second heat exchanger, 22 is the flue gas outlet of the second heat exchanger, 23 is the ionic liquid inlet of the second heat exchanger, and 24 is the ionic liquid outlet of the second heat exchanger;

[0041] 31 is the flue gas inlet of the third heat exchanger, 32 is the flue gas outlet of the third heat exchanger, 33 is the ionic liquid inlet of the third heat exchanger, and 34 is the ionic liquid outlet of the third heat exchanger;

[0042] 41 is the water inlet of the fourth heat exchanger hot network, 42 ​​is the water outlet of the fourth heat exchanger hot network, 43 is the ionic liquid inlet of the fourth heat exchanger, and 44 is the ionic liquid outlet of the fourth heat exchanger;

[0043] 51 is the water inlet of the fifth heat exchanger, 52 is the water outlet of the fifth heat exchanger, 53 is the carbon dioxide inlet of the fifth heat exchanger, and 54 is the carbon dioxide outlet of the fifth heat exchanger;

[0044] 61 is the water inlet of the sixth heat exchanger, 62 is the water outlet of the sixth heat exchanger, 63 is the sulfur dioxide inlet of the sixth heat exchanger, and 64 is the sulfur dioxide outlet of the sixth heat exchanger;

[0045] 71 is the water inlet of the seventh heat exchanger, 72 is the water outlet of the seventh heat exchanger, 73 is the ionic liquid inlet of the seventh heat exchanger, and 74 is the ionic liquid outlet of the seventh heat exchanger;

[0046] 81 is the flue gas inlet of the absorption tower, 82 is the flue gas outlet of the absorption tower, 83 is the ionic liquid inlet of the absorption tower, and 84 is the ionic liquid outlet of the absorption tower;

[0047] 91 is the ionic liquid inlet of the sulfur dioxide desorption tower, 92 is the sulfur dioxide outlet of the desorption tower, and 93 is the ionic liquid outlet of the sulfur dioxide desorption tower;

[0048] 101 is the ionic liquid inlet of the carbon dioxide desorption tower, 102 is the carbon dioxide outlet of the desorption tower, and 103 is the ionic liquid outlet of the carbon dioxide desorption tower. DETAILED DESCRIPTION

[0049] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0050] The following detailed description is an exemplary description and is intended to provide further detailed description of the present invention. Unless otherwise indicated, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the present invention belongs. The terms used in the present invention are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention.

[0051] Example 1:

[0052] See also Figure 1 As shown, a flue gas waste heat cascade utilization device for simultaneous capture of carbon and sulfur includes a first heat exchanger 1, a second heat exchanger 2, a third heat exchanger 3, a fourth heat exchanger 4, a fifth heat exchanger 5, a sixth heat exchanger 6, a seventh heat exchanger 7, an absorption tower 8, a sulfur dioxide desorption tower 9, and a carbon dioxide desorption tower 10.

[0053] The first heat exchanger 1 is provided with a first heat exchanger flue gas inlet 11, a first heat exchanger flue gas outlet 12, a first heat exchanger hot network water inlet 13, and a first heat exchanger hot network water outlet 14; the first heat exchanger flue gas inlet 11 is connected to the first heat exchanger flue gas outlet 12, the first heat exchanger hot network water inlet 13 is connected to the first heat exchanger hot network water outlet 14, and the first heat exchanger hot network water outlet 14 is connected to the hot network.

[0054] The second heat exchanger 2 is provided with a second heat exchanger flue gas inlet 21, a second heat exchanger flue gas outlet 22, a second heat exchanger ionic liquid inlet 23, and a second heat exchanger ionic liquid outlet 24. The second heat exchanger flue gas inlet 21 is connected to the second heat exchanger flue gas outlet 22, and the second heat exchanger ionic liquid inlet 23 is connected to the second heat exchanger ionic liquid outlet 24.

[0055] The third heat exchanger 3 is provided with a third heat exchanger flue gas inlet 31, a third heat exchanger flue gas outlet 32, a third heat exchanger ionic liquid inlet 33, and a third heat exchanger ionic liquid outlet 34; the third heat exchanger flue gas inlet 31 is connected to the third heat exchanger flue gas outlet 32, and the third heat exchanger ionic liquid inlet 33 is connected to the third heat exchanger ionic liquid outlet 34.

[0056] The fourth heat exchanger 4 is provided with a fourth heat exchanger hot network water inlet 41, a fourth heat exchanger hot network water outlet 42, a fourth heat exchanger ionic liquid inlet 43, and a fourth heat exchanger ionic liquid outlet 44; the fourth heat exchanger hot network water inlet 41 is connected to the fourth heat exchanger hot network water outlet 42, and the fourth heat exchanger ionic liquid inlet 43 is connected to the fourth heat exchanger ionic liquid outlet 44.

[0057] The fifth heat exchanger 5 is provided with a fifth heat exchanger hot network water inlet 51, a fifth heat exchanger hot network water outlet 52, a fifth heat exchanger carbon dioxide inlet 53, and a fifth heat exchanger carbon dioxide outlet 54; the fifth heat exchanger hot network water inlet 51 is connected to the fifth heat exchanger hot network water outlet 52, the fifth heat exchanger carbon dioxide inlet 53 is connected to the fifth heat exchanger carbon dioxide outlet 54; the fifth heat exchanger carbon dioxide outlet 54 is connected to the carbon dioxide storage tank.

[0058] The sixth heat exchanger 6 is provided with a sixth heat exchanger hot network water inlet 61, a sixth heat exchanger hot network water outlet 62, a sixth heat exchanger sulfur dioxide inlet 63, and a sixth heat exchanger sulfur dioxide outlet 64; the sixth heat exchanger hot network water inlet 61 is connected to the sixth heat exchanger hot network water outlet 62, the sixth heat exchanger sulfur dioxide inlet 63 is connected to the sixth heat exchanger sulfur dioxide outlet 64; the sixth heat exchanger sulfur dioxide outlet 64 is connected to the sulfur dioxide storage tank.

[0059] The seventh heat exchanger 7 is provided with a seventh heat exchanger hot network water inlet 71, a seventh heat exchanger hot network water outlet 72, a seventh heat exchanger ionic liquid inlet 73, and a seventh heat exchanger ionic liquid outlet 74; the seventh heat exchanger hot network water inlet 71 is connected to the seventh heat exchanger hot network water outlet 72, and the seventh heat exchanger ionic liquid inlet 73 is connected to the seventh heat exchanger ionic liquid outlet 74.

[0060] The absorption tower 8 is provided with an absorption tower flue gas inlet 81, an absorption tower flue gas outlet 82, an absorption tower ionic liquid inlet 83, and an absorption tower ionic liquid outlet 84. The absorption tower flue gas outlet 82 is located at the top of the absorption tower 8, and the absorption tower ionic liquid outlet 84 is located at the bottom of the absorption tower 8. The absorption tower flue gas outlet 82 is connected to the chimney.

[0061] The sulfur dioxide desorption tower 9 is provided with a sulfur dioxide desorption tower ionic liquid inlet 91, a sulfur dioxide desorption tower outlet 92, and a sulfur dioxide desorption tower ionic liquid outlet 93. The sulfur dioxide desorption tower outlet 92 is located at the top of the sulfur dioxide desorption tower 9, and the sulfur dioxide desorption tower ionic liquid outlet 93 is located at the bottom of the sulfur dioxide desorption tower.

[0062] The carbon dioxide desorption tower 10 is provided with a carbon dioxide desorption tower ionic liquid inlet 101, a carbon dioxide desorption tower outlet 102, and a carbon dioxide desorption tower ionic liquid outlet 103. The carbon dioxide desorption tower outlet 102 is located at the top of the carbon dioxide desorption tower, and the carbon dioxide desorption tower ionic liquid outlet 103 is located at the bottom of the carbon dioxide desorption tower.

[0063] The first heat exchanger hot network water inlet 13 is connected to the fourth heat exchanger hot network water outlet 42, the first heat exchanger flue gas outlet 12 is connected to the second heat exchanger flue gas inlet 21, the second heat exchanger flue gas outlet 22 is connected to the third heat exchanger flue gas inlet 31, the third heat exchanger flue gas outlet 32 ​​is connected to the absorption tower flue gas inlet 81, the absorption tower ionic liquid inlet 83 is connected to the seventh heat exchanger ionic liquid outlet 74, the absorption tower ionic liquid outlet 84 is connected to the third heat exchanger ionic liquid inlet 33, the third heat exchanger ionic liquid outlet 34 is connected to the sulfur dioxide desorption tower ionic liquid inlet 91, the desorption tower sulfur dioxide outlet 92 is connected to the sixth heat exchanger sulfur dioxide inlet 63, the sulfur dioxide desorption ... The body outlet 93 is connected to the second heat exchanger ionic liquid inlet 23, the second heat exchanger ionic liquid outlet 24 is connected to the carbon dioxide desorption tower ionic liquid inlet 101, the desorption tower carbon dioxide outlet 102 is connected to the fifth heat exchanger carbon dioxide inlet 53, the carbon dioxide desorption tower ionic liquid outlet 103 is connected to the fourth heat exchanger ionic liquid inlet 43, the fourth heat exchanger ionic liquid outlet 44 is connected to the seventh heat exchanger ionic liquid inlet 73, the seventh heat exchanger hot network water outlet 72 is connected to the sixth heat exchanger hot network water inlet 61, the sixth heat exchanger hot network water outlet 62 is connected to the fifth heat exchanger hot network water inlet 51, and the fifth heat exchanger hot network water outlet 52 is connected to the fourth heat exchanger hot network water inlet 41.

[0064] Example 2:

[0065] The present invention provides a cascade utilization method for flue gas waste heat with simultaneous capture of carbon and sulfur, comprising the following steps: the flue gas enters a first heat exchanger 1 through a first heat exchanger flue gas inlet 11, exchanges heat with hot network water in the first heat exchanger 1, and after the flue gas is cooled, enters a second heat exchanger 2 through a first heat exchanger flue gas outlet 12 and a second heat exchanger flue gas inlet 21, and exchanges heat with an ionic liquid in the second heat exchanger 2. After the flue gas is cooled, it enters a third heat exchanger 3 through a second heat exchanger flue gas outlet 22 and a third heat exchanger flue gas inlet 31, and exchanges heat with the ionic liquid in the third heat exchanger 3.

[0066] After the flue gas is cooled, it enters the absorption tower 8 through the flue gas outlet 32 ​​of the third heat exchanger and the flue gas inlet 81 of the absorption tower. In the absorption tower 8, the flue gas contacts the ionic liquid, and the ionic liquid absorbs carbon dioxide and sulfur dioxide in the flue gas. The ionic liquid rich in carbon dioxide and sulfur dioxide enters the third heat exchanger 3 through the ionic liquid outlet 84 of the absorption tower and the ionic liquid inlet 33 of the third heat exchanger. The remaining flue gas is discharged into the chimney through the flue gas outlet 82 of the absorption tower. The ionic liquid rich in carbon dioxide and sulfur dioxide exchanges heat with the flue gas in the third heat exchanger 3. After the ionic liquid is heated, it enters the sulfur dioxide desorption tower 9 through the ionic liquid outlet 34 of the third heat exchanger and the ionic liquid inlet 91 of the sulfur dioxide desorption tower. The ionic liquid rich in carbon dioxide and sulfur dioxide is desorbed in the sulfur dioxide desorption tower 9. The desorbed sulfur dioxide enters the sixth heat exchanger 6 through the sulfur dioxide outlet 92 of the desorption tower and the sulfur dioxide inlet 63 of the sixth heat exchanger. The desorbed ionic liquid rich in carbon dioxide and poor in sulfur dioxide is discharged through the sulfur dioxide desorption tower 84. The ionic liquid outlet 93 of the sulfur desorption tower and the ionic liquid inlet 23 of the second heat exchanger enter the second heat exchanger 2, and the ionic liquid exchanges heat with the flue gas in the second heat exchanger 2. After the ionic liquid is heated, it enters the carbon dioxide desorption tower 10 through the ionic liquid outlet 24 of the second heat exchanger and the ionic liquid inlet 101 of the carbon dioxide desorption tower. In the carbon dioxide desorption tower 10, the ionic liquid is desorbed, and the desorbed carbon dioxide enters the fifth heat exchanger 5 through the carbon dioxide outlet 102 of the desorption tower and the carbon dioxide inlet 53 of the fifth heat exchanger. The desorbed carbon dioxide and sulfur dioxide-poor ionic liquid enters the fourth heat exchanger 4 through the ionic liquid outlet 103 of the carbon dioxide desorption tower and the ionic liquid inlet 43 of the fourth heat exchanger to exchange heat with the hot network water. The ionic liquid cools down and the hot network water heats up. After the ionic liquid in the fourth heat exchanger 4 cools down, it enters the seventh heat exchanger 7 through the ionic liquid outlet 44 of the fourth heat exchanger and the ionic liquid inlet 73 of the seventh heat exchanger. After the hot network water heats up, it enters the first heat exchanger 1.

[0067] The hot network water enters the seventh heat exchanger 7 through the hot network water inlet 71 of the seventh heat exchanger. The hot network water in the seventh heat exchanger 7 exchanges heat with the ionic liquid from the fourth heat exchanger 4. The hot network water is heated and the ionic liquid is cooled. The cooled ionic liquid enters the absorption tower 8 through the ionic liquid outlet 74 of the seventh heat exchanger and the ionic liquid inlet 83 of the absorption tower. The heated hot network water enters the sixth heat exchanger 6 through the hot network water outlet 72 of the seventh heat exchanger and the hot network water inlet 61 of the sixth heat exchanger. The sulfur dioxide in the sixth heat exchanger 6 exchanges heat with the hot network water. The water temperature rises and the sulfur dioxide temperature drops. The cooled sulfur dioxide enters the sulfur dioxide storage tank through the sulfur dioxide outlet 64 of the sixth heat exchanger. The heated hot network water enters the fifth heat exchanger 5 through the hot network water outlet 62 of the sixth heat exchanger and the hot network water inlet 51 of the fifth heat exchanger. In the fifth heat exchanger 5, carbon dioxide exchanges heat with the hot network water. After the carbon dioxide temperature drops, it enters the carbon dioxide storage tank through the carbon dioxide outlet 54 of the fifth heat exchanger. After the hot network water temperature rises, it enters the fourth heat exchanger 4 through the hot network water outlet 52 of the fifth heat exchanger and the hot network water inlet 41 of the fourth heat exchanger.

[0068] In the first heat exchanger 1 , the hot network water exchanges heat with the flue gas, the hot network water is heated up, and the flue gas is cooled down. After the heated hot network water enters the hot network through the hot network water outlet 14 of the first heat exchanger.

[0069] The present invention utilizes the characteristic of ionic liquids that their absorption of carbon dioxide and sulfur dioxide decreases with increasing temperature, with the absorption of different gases decreasing significantly with increasing temperature. By absorbing carbon dioxide and sulfur dioxide at low temperatures, releasing sulfur dioxide at medium temperatures, and carbon dioxide at high temperatures, the system simultaneously captures sulfur and carbon from flue gas and fully recycles the heat in the flue gas in a step-by-step manner. The flue gas is cooled by heat exchange in the first heat exchanger 1, the second heat exchanger 2, and the third heat exchanger 3, controlling the temperature of the flue gas entering the absorption tower and increasing the absorption of carbon dioxide and sulfur dioxide. The return water from the heating network is heated by heat exchange in the seventh heat exchanger 7, the sixth heat exchanger 6, the fifth heat exchanger 5, the fourth heat exchanger 4, and the first heat exchanger 1, respectively. This system achieves high heat utilization efficiency, and the temperature of the heating network water can ultimately reach 100-130°C, which is a high value for the heating network water at this temperature. The heat in the carbon dioxide and sulfur dioxide discharged from the top of the carbon dioxide desorption tower 8 and the sulfur dioxide desorption tower 9, and the heat in the carbon dioxide- and sulfur dioxide-poor ionic liquid discharged from the bottom of the tower are also fully recovered.

[0070] Using heat network return water as a cooling source reduces circulating cooling water usage and consumption, achieving a certain degree of water conservation. By designing desorption towers with different temperatures, carbon dioxide and sulfur dioxide are removed and captured separately. By using cascaded flue gas cooling and cascaded heating of heat network return water, the flue gas temperature entering the absorption tower is lowered, increasing carbon dioxide absorption. This also enables cascaded utilization of flue gas waste heat, improving heat utilization efficiency and heating benefits. Cascaded cooling of ionic liquids enables effective recycling of the ionic liquids.

[0071] It is understood from common technical knowledge that the present invention may be implemented by other embodiments that do not depart from its spirit or essential features. Therefore, the embodiments disclosed above are, in all respects, merely illustrative and not exclusive. All modifications within the scope of the present invention or equivalent to the scope of the present invention are intended to be encompassed by the present invention.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A flue gas waste heat cascade utilization device for simultaneous capture of carbon and sulfur, characterized in that: The heat exchanger comprises a first heat exchanger (1), a second heat exchanger (2), a third heat exchanger (3), a fourth heat exchanger (4), a fifth heat exchanger (5), a sixth heat exchanger (6), a seventh heat exchanger (7), an absorption tower (8), a sulfur dioxide desorption tower (9), and a carbon dioxide desorption tower (10); The first heat exchanger (1) is provided with a first heat exchanger flue gas inlet (11), a first heat exchanger flue gas outlet (12), and a first heat exchanger hot network water inlet (13); The second heat exchanger (2) is provided with a second heat exchanger flue gas inlet (21), a second heat exchanger flue gas outlet (22), a second heat exchanger ionic liquid inlet (23), and a second heat exchanger ionic liquid outlet (24); The third heat exchanger (3) is provided with a third heat exchanger flue gas inlet (31), a third heat exchanger flue gas outlet (32), a third heat exchanger ionic liquid inlet (33), and a third heat exchanger ionic liquid outlet (34); The fourth heat exchanger (4) is provided with a fourth heat exchanger hot network water inlet (41), a fourth heat exchanger hot network water outlet (42), a fourth heat exchanger ionic liquid inlet (43) and a fourth heat exchanger ionic liquid outlet (44); The fifth heat exchanger (5) is provided with a fifth heat exchanger hot network water inlet (51), a fifth heat exchanger hot network water outlet (52), a fifth heat exchanger carbon dioxide inlet (53) and a fifth heat exchanger carbon dioxide outlet (54); The sixth heat exchanger (6) is provided with a sixth heat exchanger hot network water inlet (61), a sixth heat exchanger hot network water outlet (62), a sixth heat exchanger sulfur dioxide inlet (63) and a sixth heat exchanger sulfur dioxide outlet (64); The seventh heat exchanger (7) is provided with a seventh heat exchanger hot network water inlet (71), a seventh heat exchanger hot network water outlet (72), a seventh heat exchanger ionic liquid inlet (73), and a seventh heat exchanger ionic liquid outlet (74); The absorption tower (8) is provided with an absorption tower flue gas inlet (81), an absorption tower flue gas outlet (82), an absorption tower ionic liquid inlet (83), and an absorption tower ionic liquid outlet (84); The sulfur dioxide desorption tower (9) is provided with a sulfur dioxide desorption tower ionic liquid inlet (91), a sulfur dioxide desorption tower outlet (92), and a sulfur dioxide desorption tower ionic liquid outlet (93); The carbon dioxide desorption tower (10) is provided with a carbon dioxide desorption tower ionic liquid inlet (101), a desorption tower carbon dioxide outlet (102), and a carbon dioxide desorption tower ionic liquid outlet (103); The first heat exchanger hot network water inlet (13) is connected to the fourth heat exchanger hot network water outlet (42), the first heat exchanger flue gas outlet (12) is connected to the second heat exchanger flue gas inlet (21), the second heat exchanger flue gas outlet (22) is connected to the third heat exchanger flue gas inlet (31), the third heat exchanger flue gas outlet (32) is connected to the absorption tower flue gas inlet (81), the absorption tower ionic liquid inlet (83) is connected to the seventh heat exchanger ionic liquid outlet (74), the absorption tower ionic liquid outlet (84) is connected to the third heat exchanger ionic liquid inlet (33), the third heat exchanger ionic liquid outlet (34) is connected to the sulfur dioxide desorption tower ionic liquid inlet (91), the desorption tower sulfur dioxide outlet (92) is connected to the sixth heat exchanger sulfur dioxide inlet (63), the sulfur dioxide desorption ... The body outlet (93) is connected to the second heat exchanger ionic liquid inlet (23), the second heat exchanger ionic liquid outlet (24) is connected to the carbon dioxide desorption tower ionic liquid inlet (101), the desorption tower carbon dioxide outlet (102) is connected to the fifth heat exchanger carbon dioxide inlet (53), the carbon dioxide desorption tower ionic liquid outlet (103) is connected to the fourth heat exchanger ionic liquid inlet (43), the fourth heat exchanger ionic liquid outlet (44) is connected to the seventh heat exchanger ionic liquid inlet (73), the seventh heat exchanger hot network water outlet (72) is connected to the sixth heat exchanger hot network water inlet (61), the sixth heat exchanger hot network water outlet (62) is connected to the fifth heat exchanger hot network water inlet (51), and the fifth heat exchanger hot network water outlet (52) is connected to the fourth heat exchanger hot network water inlet (41); The sulfur dioxide outlet (92) of the desorption tower is located at the top of the sulfur dioxide desorption tower (9), and the ionic liquid outlet (93) of the sulfur dioxide desorption tower is located at the bottom of the sulfur dioxide desorption tower (9); the carbon dioxide outlet (102) of the desorption tower is located at the top of the carbon dioxide desorption tower (10), and the ionic liquid outlet (103) of the carbon dioxide desorption tower is located at the bottom of the carbon dioxide desorption tower (10); The fifth heat exchanger (5) is provided with a fifth heat exchanger carbon dioxide outlet (54); The sixth heat exchanger (6) is provided with a sixth heat exchanger sulfur dioxide outlet (64).

2. The flue gas waste heat cascade utilization device for simultaneous capture of carbon and sulfur as claimed in claim 1, characterized in that: The carbon dioxide outlet (54) of the fifth heat exchanger is connected to a carbon dioxide storage tank.

3. The flue gas waste heat cascade utilization device for simultaneous capture of carbon and sulfur as claimed in claim 2, characterized in that: The sulfur dioxide outlet (64) of the sixth heat exchanger is connected to the sulfur dioxide storage tank.

4. The device for cascade utilization of flue gas waste heat with simultaneous capture of carbon and sulfur as claimed in claim 3, characterized in that: The first heat exchanger (1) is provided with a first heat exchanger hot network water outlet (14) communicating with the first heat exchanger hot network water inlet (13); the first heat exchanger hot network water outlet (14) is connected to the hot network.

5. A method for cascade utilization of flue gas waste heat with simultaneous capture of carbon and sulfur, characterized in that: The flue gas waste heat cascade utilization device for simultaneous capture of carbon and sulfur as described in claim 4 comprises the following steps: The flue gas enters the first heat exchanger (1) and exchanges heat with the water in the heating network, the flue gas is cooled, and the water in the heating network is heated. After the flue gas is cooled, it enters the second heat exchanger (2), and exchanges heat with the ionic liquid in the second heat exchanger (2), the flue gas is cooled, and the ionic liquid is heated. After the flue gas is cooled, it enters the third heat exchanger (3), and in the third heat exchanger (3), the flue gas exchanges heat with the ionic liquid, the flue gas is cooled, and the ionic liquid is heated. After the flue gas is cooled, it enters the absorption tower (8), where the flue gas contacts the ionic liquid. The ionic liquid absorbs carbon dioxide and sulfur dioxide in the flue gas, and the ionic liquid rich in carbon dioxide and sulfur dioxide enters the third heat exchanger (3). The remaining flue gas is discharged into the chimney. The ionic liquid rich in carbon dioxide and sulfur dioxide exchanges heat with the flue gas in the third heat exchanger (3). After the ionic liquid is heated, it enters the sulfur dioxide desorption tower (9). The ionic liquid rich in carbon dioxide and sulfur dioxide desorbs in the sulfur dioxide desorption tower (9). The desorbed sulfur dioxide enters the sixth heat exchanger (6). The desorbed carbon dioxide-rich ionic liquid is discharged into the chimney. The carbon-depleted sulfur dioxide ionic liquid enters the second heat exchanger (2), the ionic liquid exchanges heat with the flue gas in the second heat exchanger (2), and after the ionic liquid is heated, it enters the carbon dioxide desorption tower (10), the ionic liquid is desorbed in the carbon dioxide desorption tower (10), the desorbed carbon dioxide enters the fifth heat exchanger (5), the desorbed carbon dioxide-depleted sulfur dioxide ionic liquid enters the fourth heat exchanger (4) to exchange heat with the hot network water, the ionic liquid cools down, the hot network water heats up, the ionic liquid in the fourth heat exchanger (4) cools down and enters the seventh heat exchanger (7), and the hot network water heats up and enters the first heat exchanger (1); The hot network water enters the seventh heat exchanger (7), the hot network water in the seventh heat exchanger (7) exchanges heat with the ionic liquid from the fourth heat exchanger (4), the hot network water is heated, the ionic liquid is cooled, and the cooled ionic liquid enters the absorption tower (8), the heated hot network water enters the sixth heat exchanger (6), the sulfur dioxide in the sixth heat exchanger (6) exchanges heat with the hot network water, the hot network water is heated, the sulfur dioxide is cooled, and the cooled sulfur dioxide enters the sulfur dioxide storage tank, the heated hot network water enters the fifth heat exchanger (5), the carbon dioxide in the fifth heat exchanger (5) exchanges heat with the hot network water, the carbon dioxide is cooled and enters the carbon dioxide storage tank, and the hot network water enters the fourth heat exchanger (4) after heating; In the first heat exchanger (1), the hot network water exchanges heat with the flue gas, the hot network water is heated up, the flue gas is cooled down, and the hot network water enters the hot network after being heated up.

6. The method for cascade utilization of flue gas waste heat with simultaneous capture of carbon and sulfur as claimed in claim 5, characterized in that: After the heat network water exchanges heat with the flue gas in the first heat exchanger (1), the temperature of the heat network water is greater than 100 degrees Celsius and less than 130 degrees Celsius.

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