Boiler-borrowing heating system of alkali recovery boiler

Abstract

The utility model belongs to the technical field of steam generation and power generation in the papermaking industry, and discloses a furnace-borrowing heating system of an alkali recovery boiler, which comprises an alkali recovery furnace, an auxiliary furnace and a first steam turbine, the alkali recovery furnace comprises a first furnace body, a first conveying pipeline and a first steam pocket, and the first conveying pipeline comprises a first water supply pipeline, a connecting pipe and a first output pipe; the first water supply pipeline and the connecting pipe are both connected with the first furnace body, the output end of the connecting pipe is provided with a furnace-borrowing heating surface, the input end of the first output pipe is connected with the output end of the furnace-borrowing heating surface, and the first steam pocket is located in the first furnace body and connected with the first water supply pipeline and the connecting pipe; the auxiliary furnace comprises a second furnace body, and the furnace temperature rise heating surface is arranged in the second furnace body; the first turbine is connected with the output end of the first output pipe. Therefore, heat exchange can be carried out between the furnace heating surface and the interior of the second furnace body, the steam is further heated, and the temperature of the steam entering the first steam turbine and the steam cycle power generation efficiency are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of steam generation and power generation in the papermaking industry, in particular to a boiler heating system for an alkali recovery boiler. Background Art

[0002] Papermaking is a process of making paper or paperboard using pulp as the main raw material through processes such as beating, pulping, screening and purification, dehydration and forming, pressing and drying.

[0003] During the pulping process, the raw materials used are primarily fibrous materials such as wood, grass, and reeds. Some of the organic matter in the pulp is converted into paper products, while the remaining portion, along with chemicals, enters the cooking liquor to form black liquor. To meet environmental protection requirements, this black liquor is typically treated using an alkali recovery process. The black liquor is transported to an alkali recovery furnace (also known as an alkali recovery furnace) and burned there. This process removes the sodium salts in the black liquor, allowing it to be recycled. The steam generated during the combustion process is then fed into a steam turbine for power generation and plant steam supply.

[0004] Since black liquor contains a lot of water, a low calorific value, and 30%-40% of alkali metal compounds with low melting points, high volatility, and strong corrosiveness, it will cause serious corrosion to the water-cooled walls and the heating surfaces of the alkali recovery furnace. The higher the wall temperature, the more severe the corrosion. Therefore, it is difficult to increase the pressure and temperature of the alkali recovery furnace. The typical pressure value based on existing process parameters is about 8.5MPa, and the temperature at the outlet of the alkali recovery furnace is also around 480℃. As a result, the steam parameters entering the steam turbine for power generation are relatively low, and the efficiency of steam cycle power generation will be relatively low. Utility Model Content

[0005] The purpose of the utility model is to provide a boiler heating system for an alkali recovery boiler, which solves the problem of low efficiency of steam cycle power generation output by the alkali recovery boiler on the basis of ensuring the safety of the alkali recovery boiler.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] A furnace heating system for an alkali recovery boiler comprises: an alkali recovery furnace, the alkali recovery furnace comprising a first furnace body, a first conveying pipeline and a first steam drum, the first conveying pipeline comprising a first water supply pipeline, a connecting pipe and a first output pipe, the first water supply pipeline and the connecting pipe being both connected to the first furnace body, the output end of the connecting pipe being provided with a furnace heating heating surface, the input end of the first output pipe being connected to the output end of the furnace heating heating surface, the first steam drum being located inside the first furnace body and connected to both the first water supply pipeline and the connecting pipe; an auxiliary furnace comprising a second furnace body, the furnace heating heating surface being provided inside the second furnace body for heat exchange with the interior of the second furnace body; and a first steam turbine, the first steam turbine being connected to the output end of the first output pipe.

[0008] Preferably, the alkali recovery furnace further includes a first economizer and a first superheater, wherein the first economizer is arranged between the first feed water pipe and the first steam drum, and the first superheater is arranged downstream of the first steam drum.

[0009] Preferably, the alkali recovery furnace includes a first water-cooled wall, which is arranged in the first steam drum, and the output end and the input end of the first water-cooled wall are both connected to the first steam drum.

[0010] Preferably, the auxiliary furnace further includes a second delivery pipeline, and the second delivery pipeline includes a second water supply pipe and a second output pipe provided in the second furnace body.

[0011] Preferably, the auxiliary furnace includes a second steam drum and a second water-cooled wall, the second steam drum is arranged between the second water supply pipe and the second output pipe and inside the second furnace body, the second water-cooled wall is arranged in the second steam drum, and the heating surface for heating by the furnace is arranged toward the second output pipe.

[0012] Preferably, the auxiliary furnace includes a second water-cooled wall and a separator, the separator is arranged between the second water supply pipe and the second output pipe and is located inside the second furnace body, the second water-cooled wall is arranged upstream of the separator, and the heating surface for heating by the furnace is arranged toward the second output pipe.

[0013] Preferably, the alkali recovery boiler's heating system further includes a second steam turbine, and the second steam turbine is connected to the output end of the second output pipe.

[0014] Preferably, the second steam turbine includes at least two cylinders, a reheater is provided in the auxiliary furnace, and an output end of the reheater is connected to the cylinders.

[0015] Preferably, the temperature difference between the output end and the input end of the heating surface heated by the furnace is not less than 15°C.

[0016] Preferably, the auxiliary boiler is one of a natural circulation boiler, a forced circulation boiler, and a direct current boiler.

[0017] Beneficial effects of the utility model:

[0018] A furnace heating system for an alkali recovery boiler comprises an alkali recovery furnace, an auxiliary furnace and a first steam turbine. The alkali recovery furnace comprises a first furnace body, a first delivery pipeline and a first steam drum. The first delivery pipeline comprises a first water supply pipeline, a connecting pipe and a first output pipe. The first water supply pipeline and the connecting pipe are both connected to the first furnace body. A heating surface for heating by furnace heating is provided at the output end of the connecting pipe. The input end of the first output pipe is connected to the output end of the heating surface for heating by furnace heating. The first steam drum is located inside the alkali recovery furnace and is connected to both the first water supply pipeline and the connecting pipe. The auxiliary furnace comprises a second furnace body. The heating surface for heating by furnace heating is provided inside the second furnace body for heat exchange with the interior of the second furnace body. The first steam turbine is connected to the output end of the first output pipe.

[0019] In this way, when the steam output from the first steam drum passes through the borrowed furnace heating surface, since the borrowed furnace heating surface is arranged inside the second furnace body, the borrowed furnace heating surface can exchange heat with the inside of the second furnace body and increase the steam temperature inside the borrowed furnace heating surface, thereby making the steam temperature entering the first steam turbine higher than the steam temperature that can be generated by the first furnace body, avoiding corrosion of the inner wall of the alkali recovery furnace due to excessive temperature, extending the service life of the alkali recovery furnace, and greatly improving the steam cycle power generation efficiency and energy utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of the heating system of the alkali recovery boiler in the first embodiment of the present invention;

[0021] Figure 2 This is a structural diagram of the heating system of the alkali recovery boiler in the second embodiment of the present invention;

[0022] Figure 3 It is a structural diagram of the borrowed furnace heating system of the alkali recovery boiler in the third embodiment of the present utility model.

[0023] In the picture:

[0024] 1. Alkali recovery furnace; 11. First furnace body; 12. First delivery pipeline; 121. First water supply pipeline; 122. Connecting pipe; 1221. Heating surface heated by the furnace; 123. First output pipe; 13. First steam drum; 14. First economizer; 15. First superheater; 16. First water-cooled wall; 17. Boiling tube screen; 2. Auxiliary furnace; 21. Second furnace body; 22. Second delivery pipeline; 221. Second water supply pipeline; 222. Second output pipe; 23. Second steam drum; 24. Second water-cooled wall; 25. Separator; 26. Second superheater; 27. Second economizer; 28. Reheater; 3. First steam turbine; 4. Second steam turbine; 41. Cylinder. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all of its components.

[0026] In the description of this utility model, unless otherwise specified or limited, the terms "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0027] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0028] In the description of this embodiment, the terms "upper," "lower," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0029] Example 1

[0030] See Figure 1 The utility model provides a furnace heating system for an alkali recovery boiler, comprising an alkali recovery furnace 1, an auxiliary furnace 2 and a first steam turbine 3. The alkali recovery furnace 1 comprises a first furnace body 11, a first conveying pipeline 12 and a first steam drum 13. The first conveying pipeline 12 comprises a first water supply pipeline 121, a connecting pipe 122 and a first output pipe 123. The first water supply pipeline 121 and the connecting pipe 122 are both connected to the first furnace body 11. The output end of the connecting pipe 122 is provided with a furnace heating heating surface 1221. The input end of the first output pipe 123 is connected to the output end of the furnace heating heating surface 1221. The first steam drum 13 is located inside the first furnace body 11 and is connected to both the output end of the first water supply pipeline 121 and the input end of the connecting pipe 122. The auxiliary furnace 2 comprises a second furnace body 21. The furnace heating heating surface 1221 is provided inside the second furnace body 21 for heat exchange with the inside of the second furnace body 21. The first steam turbine 3 is connected to the output end of the first output pipe 123. In this embodiment, the alkali recovery furnace 1 is a natural circulation boiler, and the auxiliary furnace 2 can be a circulating fluidized bed boiler, a coal-fired π-type boiler, or a coal-fired tower boiler.

[0031] In this way, the first steam drum 13 can separate the steam and transport it to the first steam turbine 3 through the connecting pipe 122 and the first output pipe 123 to generate electricity. By arranging the heating surface 1221 for heating by using the furnace inside the second furnace body 21, the steam transported to the connecting pipe 122 can be further heated under the action of the high temperature inside the second furnace body 21, so that the temperature of the steam entering the first steam turbine 3 is higher, thereby improving the steam cycle power generation efficiency and energy utilization rate, and avoiding corrosion of the inner wall of the alkali recovery furnace 1 due to excessive temperature, thereby extending the service life of the alkali recovery furnace 1. Since the heating surface 1221 for heating by using the furnace is heated inside the second furnace body 21, the inside of the first furnace body 11 can be kept at a suitable temperature.

[0032] See Figure 1In some embodiments, the alkali recovery furnace 1 further includes a first economizer 14 and a first superheater 15. The first economizer 14 is disposed between the first water supply pipe 121 and the first steam drum 13. That is, the output end of the first water supply pipe 121 is connected to the input end of the first economizer 14, and the input end of the first steam drum 13 is connected to the output end of the first economizer 14. The first superheater 15 is disposed downstream of the first steam drum 13. In this embodiment, the heating surface 1221 for heating by the furnace is disposed downstream of the first superheater 15.

[0033] In this way, the first economizer 14 can preheat the water transported to the first steam drum 13 by the first water supply pipe 121, so that the water forms steam inside the first steam drum 13, and the first superheater 15 can heat the steam output from the first steam drum 13. The superheated steam heated by the first superheater 15 exchanges heat with the inside of the second furnace body 21 through the heating surface 1221 for heating, thereby further heating the steam, which can increase the temperature of the steam entering the first steam turbine 3, so that the maximum temperature of the steam (that is, the temperature of the steam entering the first steam turbine 3) is not limited by the first furnace body 11, thereby improving the steam cycle power generation efficiency. Since the heating surface 1221 for heating is located outside the first furnace body 11, the process of steam heating at the heating surface 1221 will not affect the internal environment of the first furnace body 11, thereby avoiding corrosion or damage caused by excessive temperature inside the first furnace body 11, and extending the service life of the alkali recovery furnace 1.

[0034] It can be understood that the heating surface 1221 for heating by borrowing the furnace can be a light tube structure, or a membrane wall structure, a fin tube structure or other structure that can increase the heat exchange area of ​​the heating surface 1221 for heating by borrowing the furnace. The specific shape and setting position of the heating surface 1221 for heating by borrowing the furnace can be flexibly adjusted to achieve sufficient heat exchange between the steam located in the heating surface 1221 for heating by borrowing the furnace and the interior of the second furnace body 21. No more examples are given here.

[0035] See Figure 1 In some embodiments, the alkali recovery furnace 1 includes a first water-cooled wall 16, which is disposed on the first steam drum 13, and the input and output ends of the first water-cooled wall 16 are both connected to the first steam drum 13. In this embodiment, the alkali recovery furnace 1 further includes a boiling tube panel 17, which is connected in parallel with the first water-cooled wall 16, and the input and output ends of the boiling tube panel 17 are both connected to the first steam drum 13. The auxiliary furnace 2 is disposed on one side of the alkali recovery furnace 1.

[0036] It should be noted that the water in the first water-cooled wall 16 can absorb the heat inside the first furnace body 11 and has a certain dryness. The water with a certain dryness enters the first steam drum 13 for gas-liquid separation. The separated liquid water returns to the first water-cooled wall 16 to continue circulating. The steam separated in the first steam drum 13 enters the connecting pipe 122. When the steam passes through the heating surface 1221 heated by the furnace, it can continue to be heated by the high temperature inside the second furnace body 21 and enter the first output pipe 123 and the first steam turbine 3.

[0037] In this way, the first water-cooled wall 16 can absorb the radiant heat inside the first furnace body 11, and the water in the boiling tube panel 17 can be heated by the convection of the flue gas to generate steam, thereby increasing the area of ​​the evaporation heating surface, reducing the flue gas temperature, and improving the steam production efficiency.

[0038] It is understandable that the locations of the first water-cooled wall 16 and the boiling tube panel 17 can be flexibly adjusted according to actual needs, and this embodiment does not limit this.

[0039] See Figure 1 In some embodiments, the auxiliary furnace 2 further includes a second delivery pipeline 22, which includes a second water supply pipeline 221 and a second output pipe 222 provided in the second furnace body 21. The second water supply pipeline 221 and the second output pipe 222 are both connected to the interior of the second furnace body 21.

[0040] In this way, during the combustion of the fuel inside the second furnace body 21, as the temperature inside the second furnace body 21 increases, the feed water entering the second furnace body 21 through the second water supply pipe 221 is heated, and the steam located on the heating surface 1221 for heating by the furnace can achieve the effect of heating through heat exchange with the inside of the second furnace body 21, so that the temperature of the steam entering the first steam turbine 3 is higher, thereby improving the efficiency of steam cycle power generation.

[0041] It is understandable that the locations of the second water supply pipe 221 and the second output pipe 222 can be flexibly adjusted according to actual needs, and this embodiment does not limit this.

[0042] See Figure 1 In some embodiments, the auxiliary furnace 2 includes a second steam drum 23 and a second water-cooled wall 24. The second steam drum 23 is arranged between the second water supply pipe 221 and the second output pipe 222 and is arranged inside the second furnace body 21. The second water-cooled wall 24 is arranged inside the second steam drum 23, and the heating surface 1221 is arranged toward the second output pipe 222 when the furnace is heated.

[0043] Among them, the input end and the output end of the second water-cooled wall 24 are both connected to the second steam drum 23, the furnace heating heating surface 1221 extends into the interior of the second furnace body 21, and is arranged on the side of the second output pipe 222. Furthermore, the furnace heating heating surface 1221 is arranged in an area inside the second furnace body 21 where the flue gas temperature is greater than 600°C; the auxiliary furnace 2 also includes a second economizer 27, which is arranged between the second water supply pipe 221 and the second steam drum 23, that is, upstream of the second steam drum 23.

[0044] In this way, the water inside the second water-cooled wall 24 can absorb the heat inside the second furnace body 21 and has a certain dryness. The second steam drum 23 can perform gas-liquid separation on the water with a certain dryness, so that the steam output by the second steam drum 23 enters the second superheater 26 and forms superheated steam. The water output by the second steam drum 23 is recirculated to the inside of the second water-cooled wall 24. Since the steam temperature in the second output pipe 222 is relatively high, the heating surface 1221 for heating by using the furnace is set in the area where the flue gas temperature inside the second furnace body 21 is greater than 600°C. This can improve the steam heating efficiency in the heating surface 1221 for heating by using the furnace, thereby increasing the steam temperature entering the first steam turbine 3, thereby improving the steam cycle power generation efficiency and effectively utilizing thermal energy; the second economizer 27 can further preheat the feed water so that it can be quickly converted into steam.

[0045] It is understandable that the circulation form of the second water-cooled wall 24 can be a natural circulation or a forced circulation drum boiler. The specific structure and size of the second water-cooled wall 24 can be adjusted according to actual needs and will not be listed in detail here.

[0046] See Figure 1 In some embodiments, the auxiliary furnace 2 further includes a second superheater 26 , which is connected to the second output pipe 222 , and the furnace heating heating surface 1221 is arranged on the output end side of the second superheater 26 , that is, downstream of the second superheater 26 .

[0047] In this way, the second superheater 26 can further heat the steam in the second output pipe 222, so that the steam temperature in the heating surface 1221 located on the output end side of the second superheater 26 is higher, so as to improve the steam cycle power generation efficiency, and can prevent the alkali metal compounds in the first furnace body 11 from corroding the inner wall of the first furnace body 11 at high temperature, thereby extending the service life of the first furnace body 11.

[0048] It can be understood that the heating surface 1221 for heating by using the furnace can also be set on the side of the input end of the second superheater 26 or at other positions. In this embodiment, the heating surface 1221 for heating by using the furnace is set at the output end of the second superheater 26, the purpose of which is to improve the heating efficiency of the heating surface 1221 for heating by using the furnace.

[0049] See Figure 1In some embodiments, the alkali recovery boiler's heating system further includes a second steam turbine 4 , which is connected to the output end of the second output pipe 222 .

[0050] In this embodiment, the second steam turbine 4 includes a cylinder 41 , and the input end of the second steam turbine 4 is connected to the output end of the second superheater 26 through a second output pipe 222 so that the steam heated by the second superheater 26 enters the cylinder 41 of the second steam turbine 4 .

[0051] It should be noted that the feed water enters the second steam drum 23 after passing through the second economizer 27, the unsaturated water in the second steam drum 23 enters the second water-cooled wall 24 to absorb the heat in the second furnace body 21, and the steam separated from the second steam drum 23 enters the second superheater 26 for heating and then enters the second steam turbine 4.

[0052] In some embodiments, the temperature difference between the output end and the input end of the heating surface 1221 heated by the auxiliary furnace is not less than 15°C, that is, the steam temperature delivered to the first steam turbine 3 after being heated by the auxiliary furnace 2 is more than 15°C higher than the steam temperature delivered to the inside of the auxiliary furnace 2.

[0053] Furthermore, the steam parameters at the outlet of the first superheater 15 are 800t / h, 8.8MPa, and 480℃, and the steam parameters after entering the auxiliary furnace 2 for heating are 800t / h and 8.4MPa. The steam temperature at the output end after heating by the auxiliary furnace 2 is greater than 510℃, and the steam heated by the auxiliary furnace 2 enters the first steam turbine 3; the steam parameters at the outlet of the second superheater 26 are 630t / h, 13.7MPa, and 540℃, and the steam heated by the second superheater 26 enters the second steam turbine 4; the steam pressure level at the outlet of the second superheater 26 can be high pressure (8MPa-10MPa), ultra-high pressure (11.5MPa-14MPa), subcritical (16MPa-18.5MPa), supercritical (24MPa-26MPa), and ultra-supercritical (27MPa-33MPa).

[0054] In this way, the steam output by the second output pipe 222 can participate in power generation under the action of the second steam turbine 4, thereby improving energy utilization and steam cycle power generation efficiency. Since the interior of the second furnace body 21 is not affected by alkali metal compounds, the temperature inside the second furnace body 21 can be made higher than the temperature inside the first furnace body 11, thereby increasing the steam temperature, so that it further heats the air in the heating surface 1221 of the furnace, so that the steam temperature entering the first steam turbine 3 is higher.

[0055] It is understandable that the first output pipe 123 can also be connected to the second steam turbine 4, or the second output pipe 222 can also be connected to the first steam turbine 3, that is, the steam output by the first output pipe 123 and the second output pipe 222 enters the same steam turbine for power generation, which will not be elaborated here.

[0056] Example 2

[0057] See Figure 2 , which differs from the first embodiment in that the second steam turbine 4 includes at least two cylinders 41, a reheater 28 is provided in the auxiliary furnace 2, and the output end of the reheater 28 is connected to the cylinders 41. In this embodiment, the second steam turbine 4 includes two cylinders 41, the reheater 28 is connected to the upstream cylinder 41, the auxiliary furnace 2 is a subcritical natural circulation boiler or a forced circulation boiler, the steam parameters at the outlet of the second superheater 26 are 980 t / h, 17.3 MPa, and 540°C, and the steam parameters at the outlet of the reheater 28 are 800 t / h, 3.8 MPa, and 540°C.

[0058] In this way, by setting up at least two cylinders, the reheater 28 heats the cold steam output by the cylinder 41 located upstream after work, so that the steam output by the second output pipe 222 can be further utilized to generate more electricity and improve the steam cycle power generation efficiency.

[0059] It can be understood that the number of the second steam turbine 4 and the reheater 28 can be flexibly adjusted according to actual needs, and no further details will be given here; the cylinder 41 can be set to three, four, or five. When there are three or fewer cylinders 41, the reheater 28 may not be set in the auxiliary furnace 2. When there are two or more cylinders 41, the reheater 28 may be set in the auxiliary furnace 2. The number of cylinders 41 and the setting of the reheater can be flexibly adjusted according to actual needs, and no further details will be given here.

[0060] See Figure 2 In some embodiments, the heating surface 1221 and the reheater 28 are respectively arranged on both sides of the second output pipe 222.

[0061] In this embodiment, the heating surface 1221 is arranged on the side of the second output pipe 222 facing the first furnace body 11 , and the reheater 28 is arranged on the side of the second output pipe 222 facing away from the heating surface 1221 .

[0062] In this way, the heating surface 1221 for heating by using the furnace and the reheater 28 are respectively arranged on both sides of the second output pipe 222, which can effectively utilize the steam heat in the second output pipe 222 on the output end side of the second superheater 26, and increase the temperature of the steam in the heating surface 1221 for heating by using the furnace and the steam in the reheater 28, thereby improving the steam cycle power generation efficiency entering the first steam turbine 3 and the second steam turbine 4, avoiding damage to the inside of the first furnace body 11 due to excessive temperature, and reasonably utilizing thermal energy.

[0063] Example 3

[0064] See Figure 3 The difference from Example 2 is that the auxiliary furnace 2 includes a second water-cooled wall 24 and a separator 25. The separator 25 is arranged between the second water supply pipe 221 and the second output pipe 222 and is located inside the second furnace body 21. The second water-cooled wall 24 is arranged upstream of the separator 25, and the heating surface 1221 is arranged toward the second output pipe 222 when the furnace is heated.

[0065] Among them, the auxiliary furnace 2 is a supercritical once-through boiler, the outlet steam parameters of the second superheater 26 are 1860t / h, 25.4MPa, and 571°C, and the outlet parameters of the reheater 28 are 1550t / h, 4.3MPa, and 569°C.

[0066] In this way, the feed water enters the second water-cooled wall 24 after passing through the second economizer 27, and enters the separator 25 after being heated inside the second furnace body 21, where the steam can be separated and transported to the second superheater 26. The separated steam enters the second superheater 26 to be heated into superheated steam and enters the second steam turbine 4. The cold reheated steam after doing work enters the reheater 28 to be heated and then enters the next-stage second steam turbine 4, thereby improving the steam cycle power generation efficiency.

[0067] Obviously, the above-described embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the manner in which the present invention is to be implemented. A person skilled in the art would be able to make various obvious changes, readjustments, and substitutions without departing from the scope of protection of the present invention. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A heating system for an alkali recovery boiler, characterized in that: include: An alkali recovery furnace (1), the alkali recovery furnace (1) comprising a first furnace body (11), a first delivery pipeline (12) and a first steam drum (13); the first delivery pipeline (12) comprising a first water supply pipeline (121), a connecting pipe (122) and a first output pipe (123); the first water supply pipeline (121) and the connecting pipe (122) are both connected to the first furnace body (11); the output end of the connecting pipe (122) is provided with a heating surface (1221) for heating by using the furnace; the input end of the first output pipe (123) is connected to the output end of the heating surface (1221) for heating by using the furnace; the first steam drum (13) is located inside the first furnace body (11) and is connected to the first water supply pipeline (121) and the connecting pipe (122); An auxiliary furnace (2), the auxiliary furnace (2) comprising a second furnace body (21), the heating surface (1221) for heating by using the furnace to heat up being arranged inside the second furnace body (21) and used for heat exchange with the interior of the second furnace body (21); A first steam turbine (3) is connected to the output end of the first output pipe (123).

2. The alkali recovery boiler heating system according to claim 1, characterized in that: The alkali recovery furnace (1) further comprises a first economizer (14) and a first superheater (15), wherein the first economizer (14) is arranged between the first water supply pipe (121) and the first steam drum (13), and the first superheater (15) is arranged downstream of the first steam drum (13).

3. The alkali recovery boiler heating system according to claim 1, characterized in that: The alkali recovery furnace (1) comprises a first water-cooled wall (16), the first water-cooled wall (16) is arranged on the first steam drum (13), and the output end and the input end of the first water-cooled wall (16) are both connected to the first steam drum (13).

4. The alkali recovery boiler heating system according to claim 1, characterized in that: The auxiliary furnace (2) further comprises a second delivery pipeline (22), wherein the second delivery pipeline (22) comprises a second water supply pipe (221) and a second output pipe (222) provided on the second furnace body (21).

5. The alkali recovery boiler heating system according to claim 4, characterized in that: The auxiliary furnace (2) includes a second steam drum (23) and a second water-cooled wall (24); the second steam drum (23) is arranged between the second water supply pipe (221) and the second output pipe (222) and is arranged inside the second furnace body (21); the second water-cooled wall (24) is arranged in the second steam drum (23); and the heating surface (1221) for heating by the furnace is arranged toward the second output pipe (222).

6. The alkali recovery boiler heating system according to claim 4, characterized in that: The auxiliary furnace (2) includes a second water-cooled wall (24) and a separator (25). The separator (25) is arranged between the second water supply pipe (221) and the second output pipe (222) and is located inside the second furnace body (21). The second water-cooled wall (24) is arranged upstream of the separator (25). The heating surface (1221) for heating by the auxiliary furnace is arranged toward the second output pipe (222).

7. The alkali recovery boiler heating system according to claim 4, characterized in that: The alkali recovery boiler's heating system further comprises a second steam turbine (4), and the second steam turbine (4) is connected to the output end of the second output pipe (222).

8. The alkali recovery boiler heating system according to claim 7, characterized in that: The second steam turbine (4) includes at least two cylinders (41), a reheater (28) is provided in the auxiliary furnace (2), and an output end of the reheater (28) is connected to the cylinders (41).

9. The alkali recovery boiler heating system according to claim 1, characterized in that: The temperature difference between the output end and the input end of the heating surface (1221) heated by the furnace is not less than 15°C.

10. The alkali recovery boiler heating system according to claim 1, characterized in that: The auxiliary boiler (2) is one of a natural circulation boiler, a forced circulation boiler, and a direct current boiler.

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