Double-machine back pressure control thermal system of small steam turbine and control method thereof

Abstract

The present application relates to the technical field of steam turbine, especially to a back pressure control thermodynamic system of double-machine regenerative small steam turbine, which comprises a main steam turbine, a small steam turbine, a first heater, a second heater, a working mechanism connected with the small steam turbine, a water outlet of the second heater connected with a water inlet of the first heater, an exhaust port of the small steam turbine connected with the first heater through an exhaust pipeline, the first heater connected with a first bypass in parallel, a first adjusting valve group arranged on the first bypass, a first steam extraction port arranged on the main steam turbine, the first steam extraction port connected with the second heater through a first steam extraction pipeline, the exhaust pipeline and the first steam extraction pipeline connected through an overflow pipeline, and an overflow adjusting valve group arranged on the overflow pipeline. The present application also relates to a control method of the system, which mainly controls the back pressure of the small steam turbine by adjusting the opening of the first adjusting valve group and / or the overflow adjusting valve group. The present application increases the means of back pressure adjustment of the small steam turbine and improves the flexibility and reliability of the system.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, and in particular to a back pressure control thermodynamic system and control method for a dual-unit regenerative small steam turbine. Background Technology

[0002] As the parameters of thermal power turbine units increase, the superheat of high-pressure regenerative extraction steam also increases. In order to address the resulting decrease in energy efficiency, increase in irreversible losses, and increase in the cost of high-pressure extraction steam pipelines and high-pressure heaters, a dual-unit regenerative system has been proposed. This system can significantly reduce the superheat of high-pressure regenerative extraction steam, thereby improving the economic efficiency of the unit and reducing the cost of the unit.

[0003] The dual-turbine regenerative system includes a main steam turbine and a small steam turbine. The main steam turbine provides steam for part of the high-pressure heater, the small steam turbine, and part of the low-pressure heater. The small steam turbine is an extraction back-pressure steam turbine. The intermediate extraction and exhaust steam of the small steam turbine are supplied to the regenerative heater. The rotor of the small steam turbine is connected to the working mechanism and provides power to the working mechanism.

[0004] The dual-unit regenerative small steam turbine differs from the feedwater pump turbine in conventional thermal power units. While driving the working mechanism, it is also coupled with multi-stage regenerative steam extraction, which increases the difficulty of control and places higher demands on the control. The flexible and reliable operation of the small steam turbine is the foundation for ensuring the safety and economy of the entire unit. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a thermodynamic system for back pressure control of a dual-unit regenerative small steam turbine and its control method, which can meet the back pressure control requirements of the small steam turbine while improving the flexibility and reliability of the system, so as to overcome the above-mentioned defects of the prior art.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] This invention provides a thermal system for controlling back pressure of a dual-unit regenerative small steam turbine, comprising a main steam turbine, a small steam turbine, a first heater, a second heater, and a working mechanism connected to the small steam turbine. The outlet of the second heater is connected to the inlet of the first heater. The exhaust port of the small steam turbine is connected to the first heater via an exhaust pipe. The first heater is connected in parallel with a first bypass, and a first regulating valve group is provided on the first bypass. The main steam turbine is provided with a first extraction port, which is connected to the second heater via a first extraction pipe. The exhaust pipe and the first extraction pipe are connected via an overflow pipe, and an overflow regulating valve group is provided on the overflow pipe. The back pressure of the small steam turbine is controlled by adjusting the opening of the first regulating valve group and / or the overflow regulating valve group.

[0008] Preferably, the outlet of the first heater is connected to the inlet of the deaerator, and the small turbine is provided with a first small turbine extraction port, which is connected to the deaerator through the first small turbine extraction pipeline.

[0009] Preferably, the second heater is connected in parallel with the second bypass, and the second bypass is provided with a second regulating valve group.

[0010] Preferably, it also includes a third heater, the outlet of the third heater is connected to the inlet of the second heater, a second steam extraction port is provided downstream of the first steam extraction port on the main steam turbine, the second steam extraction port is connected to the third heater through a second steam extraction pipeline, the third heater is connected in parallel with a third bypass, and a third regulating valve group is provided on the third bypass.

[0011] Preferably, it also includes a high-pressure heater, the outlet of the deaerator is connected to the inlet of the high-pressure heater, the main steam turbine is provided with a third steam extraction port upstream of the first steam extraction port, the small steam turbine is provided with a second small steam extraction port upstream of the first small steam extraction port, and the third steam extraction port and the second small steam extraction port are respectively connected to the high-pressure heater through the third steam extraction pipeline and the second small steam extraction pipeline.

[0012] Preferably, it also includes a low-pressure heater, the outlet of which is connected to the inlet of the third heater, and a fourth steam extraction port is provided on the main steam turbine downstream of the second steam extraction port, which is connected to the low-pressure heater through a fourth steam extraction pipeline.

[0013] The present invention also provides a control method for the back pressure control thermal system of a dual-unit regenerative small steam turbine as described above, comprising: control measure one, adjusting the opening of the first regulating valve group to increase or decrease, thereby increasing or decreasing the back pressure of the small steam turbine; control measure two, adjusting the opening of the overflow regulating valve group to increase or decrease, thereby decreasing or increasing the back pressure of the small steam turbine; and, according to the back pressure control requirements of the small steam turbine, adopting control measure one and / or control measure two to achieve the back pressure control requirements of the small steam turbine.

[0014] Preferably, the second heater is connected in parallel with the second bypass, and the second bypass is provided with a second regulating valve group; the control method of the back pressure control thermal system of the dual-unit regenerative small steam turbine also includes: control measure three, adjusting the opening of the second regulating valve group to increase or decrease, so that the back pressure of the small steam turbine decreases or increases; according to the back pressure control requirements of the small steam turbine, one or more combinations of control measure one, control measure two and control measure three are adopted to achieve the back pressure control requirements of the small steam turbine.

[0015] Preferably, the back pressure control thermal system for the dual-unit regenerative small steam turbine further includes a third heater. The outlet of the third heater is connected to the inlet of the second heater. A second extraction port is provided downstream of the first extraction port on the main steam turbine. The second extraction port is connected to the third heater through a second extraction pipe. The third heater is connected in parallel with a third bypass, and a third regulating valve group is provided on the third bypass. The control method of the back pressure control thermal system for the dual-unit regenerative small steam turbine further includes: control measure four, adjusting the opening of the third regulating valve group to increase or decrease, so that the back pressure of the small steam turbine decreases or increases; according to the back pressure control requirements of the small steam turbine, one or more combinations of control measure one, control measure two, control measure three and control measure four are adopted to achieve the back pressure control requirements of the small steam turbine.

[0016] Compared with the prior art, the present invention has significant progress:

[0017] By setting a first bypass and a first regulating valve group for the first heater, and installing an overflow regulating valve group on the overflow pipe connecting the exhaust pipe and the first extraction pipe, the first regulating valve group can cooperate with the overflow regulating valve group to coordinate the control of the back pressure of the small steam turbine. Individual adjustment of the first regulating valve group and the overflow regulating valve group can each form a control measure. By employing one or a combination of these two control measures, multiple methods for controlling the back pressure of the small steam turbine can be achieved, increasing the means of regulating the back pressure of the small steam turbine. Due to the combination of multiple control measures, compared with the control method of simply adjusting the overflow pipe regulating valve group, this invention can respond more quickly to the demand for changes in the back pressure of the small steam turbine, improving the system's flexibility and reliability, and reducing the design capacity requirements for the overflow pipe and the overflow regulating valve group. Furthermore, the control measures in this invention are independent and do not affect each other. Even if one control pipe fails during field operation, the other control pipes can still operate in combination to control the back pressure of the small steam turbine. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the back pressure control thermodynamic system of the dual-unit regenerative small steam turbine according to an embodiment of the present invention.

[0019] The reference numerals in the attached figures are explained as follows:

[0020] 1. Main steam turbine

[0021] 101 First extraction steam pipeline

[0022] 102 Second extraction steam pipeline

[0023] 103 Third extraction steam pipeline

[0024] 104 Fourth extraction steam pipeline

[0025] 2 Small steam turbines

[0026] 201 Steam Inlet Pipeline

[0027] 202 Exhaust Pipeline

[0028] 203 The first small machine extraction pipeline

[0029] 204 Second small machine extraction pipeline

[0030] 31 First heater

[0031] 301 First Bypass

[0032] 32 Second heater

[0033] 302 Second Bypass

[0034] 33 Third heater

[0035] 303 Third Bypass

[0036] 34 Deaerator

[0037] 35 High-pressure heater

[0038] 36 Low-pressure heater

[0039] 4. Working Organization

[0040] 51 First regulating valve group

[0041] 52 Second regulating valve group

[0042] 53 Third regulating valve group

[0043] 6. Overflow pipe

[0044] 61 Overflow regulating valve assembly Detailed Implementation

[0045] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0046] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0047] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0048] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0049] It should be noted that the term "downstream" in this article refers to the downstream direction along the steam flow direction of the main steam turbine, while "upstream" refers to the upstream direction along the steam flow direction of the main steam turbine.

[0050] like Figure 1 As shown, this is one embodiment of the dual-turbine regenerative small steam turbine back pressure control thermodynamic system of the present invention. The dual-turbine regenerative small steam turbine back pressure control thermodynamic system of this embodiment includes a main steam turbine 1, a small steam turbine 2, a first heater 31, a second heater 32, and a working mechanism 4.

[0051] Steam enters the main turbine 1 through its inlet, passes through the high-pressure zone, intermediate-pressure zone, and low-pressure zone in sequence, and then exits through its exhaust port. The arrangement of the main turbine 1 in this embodiment is not limited; it can be a single-shaft arrangement or a split-shaft arrangement.

[0052] In this embodiment, the small steam turbine 2 is an extraction back-pressure steam turbine. The steam inlet of the small steam turbine 2 is connected to the steam inlet pipe 201, from which steam is supplied to the small steam turbine 2. The steam source for the steam inlet pipe 201 is not limited; it can be provided by the main steam turbine 1, the boiler system, or other main steam turbines in the same power plant. Preferably, in this embodiment, the steam inlet pipe 201 is connected to the main steam turbine 1, which supplies steam to the small steam turbine 2. The working mechanism 4 is connected to the rotor of the small steam turbine 2. When the steam flows within the small steam turbine 2, it drives the rotor to rotate, providing power to the working mechanism 4 and driving its operation. In this embodiment, the working mechanism 4 is primarily a feedwater pump, but may also include other driven equipment.

[0053] The first heater 31 and the second heater 32 are used to recover heat from the small steam turbine 2 and the main steam turbine 1 to heat the working fluid (such as feedwater or condensate) of the thermodynamic cycle, thereby improving the cycle efficiency. The outlet of the second heater 32 is connected to the inlet of the first heater 31, meaning the second heater 32 is the upstream of the first heater 31. The exhaust port of the small steam turbine 2 is connected to the first heater 31 through the exhaust pipe 202, and the exhaust steam from the small steam turbine 2 enters the first heater 31 through the exhaust pipe 202. The first heater 31 is connected in parallel with the first bypass 301, and the first bypass 301 is equipped with a first regulating valve group 51. The main steam turbine 1 is equipped with a first extraction port, which is connected to the second heater 32 through the first extraction pipe 101. Steam is extracted from the first extraction port of the main steam turbine 1 through the first extraction pipe 101 and sent to the second heater 32. The exhaust pipe 202 and the first extraction pipe 101 are connected by an overflow pipe 6, and an overflow regulating valve group 61 is provided on the overflow pipe 6.

[0054] Since the first heater 31 is connected to the exhaust port of the small steam turbine 2 through the exhaust pipe 202, if the pressure loss of the exhaust pipe 202 is ignored, the exhaust pressure of the small steam turbine 2 is equal to the pressure of the first heater 31. That is, the back pressure of the small steam turbine 2 is equal to the pressure of the first heater 31. Therefore, controlling the pressure of the first heater 31 can achieve back pressure control of the small steam turbine 2. The pressure of the first heater 31 is determined by two sets of parameters. One set is the condensate flow rate, condensate pressure, and condensate temperature at the inlet of the first heater 31. The other set is the flow rate of the regenerative extraction steam. In this embodiment, under the same operating conditions, the condensate pressure at the inlet of the first heater 31 remains basically constant. Therefore, the pressure of the first heater 31 is mainly related to the condensate flow rate, condensate temperature, and regenerative extraction steam flow rate of the first heater 31.

[0055] The condensate from the outlet of the first heater 31 mixes with the condensate in the first bypass 301 and enters the lower stage (deaerator 34) of the first heater 31. If the pressure loss and heat dissipation of the first bypass 301 are ignored, the condensate temperature in the first bypass 301 is equal to, and lower than, the condensate temperature at the outlet of the second heater 32. As the opening of the first regulating valve group 51 gradually increases, the temperature of the condensate entering the lower stage (deaerator 34) of the first heater 31 will gradually decrease, and the condensate flow rate entering the first heater 31 will also decrease. Therefore, by adjusting the opening of the first regulating valve group 51, the condensate flow rate at the inlet of the first heater 31 can be adjusted, thereby regulating the pressure of the first heater 31. As the opening of the first regulating valve group 51 gradually increases, the condensate flow rate entering the first heater 31 decreases, causing the pressure of the first heater 31 to increase. Therefore, increasing the opening of the first regulating valve group 51 can increase the back pressure of the small turbine 2. Conversely, as the opening of the first regulating valve group 51 gradually decreases, the condensate flow rate entering the first heater 31 increases, causing the pressure of the first heater 31 to decrease. Therefore, adjusting the opening of the first regulating valve group 51 to decrease can reduce the back pressure of the small steam turbine 2.

[0056] Since the exhaust pipe 202 and the first extraction pipe 101 are connected by the overflow pipe 6, as the opening of the overflow regulating valve group 61 on the overflow pipe 6 gradually increases, the steam flow rate entering the first heater 31 will gradually decrease. Therefore, by adjusting the opening of the overflow regulating valve group 61, the flow rate of regenerative extraction steam entering the first heater 31 can be adjusted, thereby adjusting the pressure of the first heater 31. As the opening of the overflow regulating valve group 61 gradually increases, the steam flow rate entering the first heater 31 decreases, causing the pressure of the first heater 31 to decrease. Therefore, increasing the opening of the overflow regulating valve group 61 can reduce the back pressure of the small turbine 2. Conversely, as the opening of the overflow regulating valve group 61 gradually decreases, the steam flow rate entering the first heater 31 increases, causing the pressure of the first heater 31 to increase. Therefore, decreasing the opening of the overflow regulating valve group 61 can increase the back pressure of the small turbine 2.

[0057] Therefore, the back pressure control thermodynamic system of the dual-unit regenerative small steam turbine in this embodiment can control the back pressure of the small steam turbine 2 by adjusting the opening of the first regulating valve group 51 and / or the overflow regulating valve group 61.

[0058] Based on this, this embodiment also provides a control method for the back pressure control thermodynamic system of the dual-unit regenerative small steam turbine described above. The control method for the back pressure control thermodynamic system of the dual-unit regenerative small steam turbine in this embodiment includes control measure one and control measure two. Control measure one is: increasing the opening of the first regulating valve group 51 to raise the back pressure of the small steam turbine 2; or decreasing the opening of the first regulating valve group 51 to lower the back pressure of the small steam turbine 2. Control measure two is: increasing the opening of the overflow regulating valve group 61 to lower the back pressure of the small steam turbine 2; or decreasing the opening of the overflow regulating valve group 61 to raise the back pressure of the small steam turbine 2. According to the back pressure control requirements of the small steam turbine 2, control measure one and / or control measure two are adopted to achieve the back pressure control requirements of the small steam turbine 2.

[0059] The dual-unit regenerative small steam turbine back pressure control thermodynamic system and its control method in this embodiment, by setting a first bypass 301 and a first regulating valve group 51 for the first heater 31, and setting an overflow regulating valve group 61 on the overflow pipe 6 connecting the exhaust pipe 202 and the first extraction pipe 101, can coordinate the operation of the first regulating valve group 51 and the overflow regulating valve group 61 to control the back pressure of the small steam turbine 2. The individual adjustment of the first regulating valve group 51 and the overflow regulating valve group 61 can each form a control measure. By using one or a combination of the two control measures, multiple control methods for the back pressure of the small steam turbine 2 can be realized, increasing the means of regulating the back pressure of the small steam turbine 2. Due to the combination of multiple control measures, compared with the control method of simply adjusting the overflow pipe regulating valve group, this embodiment can respond more quickly to the demand for changes in the back pressure of the small steam turbine 2, improve the flexibility and reliability of the system, and reduce the design capacity requirements of the overflow pipe 6 and the overflow regulating valve group 61. Meanwhile, the control measures in this embodiment are independent of each other and do not affect each other. Even if a certain control pipeline fails during on-site operation, other control pipelines can still be combined to achieve control of the back pressure of the small steam turbine 2.

[0060] In this embodiment, the outlet of the first heater 31 is connected to the inlet of the deaerator 34, meaning the deaerator 34 is the downstream stage of the first heater 31. The small turbine 2 is equipped with a first small turbine extraction port, which is connected to the deaerator 34 via a first small turbine extraction pipeline 203. Steam is extracted from the first small turbine extraction port on the small turbine 2 by the first small turbine extraction pipeline 203 and sent into the deaerator 34.

[0061] In this embodiment, control measure one can also reduce the range of pressure variation of deaerator 34 with the back pressure of small turbine 2, which is beneficial for deaerator 34 to operate within a reasonable pressure range. Control scheme one is defined as using control measure two alone, and control scheme two is defined as using a combination of control measure two and control measure one. The comparative analysis of the two control schemes is as follows.

[0062] When the back pressure of small steam turbine 2 is P, and the target pressure for back pressure control of small steam turbine 2 is P+ΔP, two control schemes are adopted to achieve the target pressure of back pressure control of small steam turbine 2, P+ΔP. The relevant parameters are compared as follows: the condensate temperature entering deaerator 34 is greater in control scheme 1 than in control scheme 2; the extraction steam flow rate of deaerator 34 is less in control scheme 1 than in control scheme 2; the flow rate of the last stage of small steam turbine 2 is greater in control scheme 1 than in control scheme 2; the back pressure of small steam turbine 2 is equal to that of control scheme 1 and control scheme 2; the pressure of deaerator 34 is greater in control scheme 1 than in control scheme 2, as shown in Table 1 below.

[0063] Table 1

[0064]

[0065] It is evident that when the back pressure of the small steam turbine 2 is increased, the implementation of control measure one can reduce the magnitude of the pressure rise in the deaerator 34, thus preventing the pressure of the deaerator 34 from rising above its allowable range as the back pressure of the small steam turbine 2 increases.

[0066] When the back pressure of small steam turbine 2 is P, and the target pressure for back pressure control of small steam turbine 2 is P-ΔP, two control schemes are adopted to achieve the target pressure of back pressure control of small steam turbine 2, P-ΔP. The relevant parameters are compared as follows: the condensate temperature entering deaerator 34 is less than that of control scheme 2 in control scheme 1; the extraction steam flow rate of deaerator 34 is greater than that of control scheme 2 in control scheme 1; the flow rate of the last stage of small steam turbine 2 is less than that of control scheme 2 in control scheme 1; the back pressure of small steam turbine 2 is equal to that of control scheme 2 in control scheme 1; and the pressure of deaerator 34 is less than that of control scheme 2 in control scheme 1. See Table 2 below.

[0067] Table 2

[0068]

[0069] It is evident that when the back pressure of the small steam turbine 2 is reduced, the implementation of control measure one can reduce the magnitude of the pressure drop in the deaerator 34, thus preventing the pressure of the deaerator 34 from falling below its allowable range as the back pressure of the small steam turbine 2 decreases.

[0070] To expand the adjustable control range of the back pressure of the small steam turbine 2 and achieve the target pressure of the back pressure control of the small steam turbine 2 more quickly, preferably, in the dual-unit regenerative small steam turbine back pressure control thermodynamic system of this embodiment, a second bypass 302 can be provided for the second heater 32. The second heater 32 and the second bypass 302 are connected in parallel, and a second regulating valve group 52 is provided on the second bypass 302. The condensate from the outlet of the second heater 32 and the condensate in the second bypass 302 are mixed and then enter the first heater 31. If the pressure loss and heat dissipation loss of the second bypass 302 are ignored, the temperature of the condensate in the second bypass 302 is equal to the temperature of the condensate at the outlet of the upper stage (third heater 33) of the second heater 32, and lower than the temperature of the condensate at the outlet of the second heater 32. As the opening of the second regulating valve group 52 gradually increases, the temperature of the condensate entering the first heater 31 will gradually decrease, and at the same time, the flow rate of the condensate entering the second heater 32 will decrease. Therefore, by adjusting the opening of the second regulating valve group 52, the condensate temperature at the inlet of the first heater 31 can be adjusted, thereby regulating the pressure of the first heater 31. As the opening of the second regulating valve group 52 gradually increases, the temperature of the condensate entering the first heater 31 decreases, causing the pressure of the first heater 31 to decrease. Therefore, increasing the opening of the second regulating valve group 52 can reduce the back pressure of the small steam turbine 2. Conversely, as the opening of the second regulating valve group 52 gradually decreases, the temperature of the condensate entering the first heater 31 increases, causing the pressure of the first heater 31 to increase. Therefore, decreasing the opening of the second regulating valve group 52 can increase the back pressure of the small steam turbine 2.

[0071] Therefore, the back pressure control thermodynamic system of the dual-unit regenerative small steam turbine in this embodiment can control the back pressure of the small steam turbine 2 by adjusting the opening degree of one or more of the first regulating valve group 51, the overflow regulating valve group 61, and the second regulating valve group 52.

[0072] Based on this, the control method of the back pressure control thermodynamic system of the dual-unit regenerative small steam turbine in this embodiment further includes control measure three, which is: increasing the opening of the second regulating valve group 52 to reduce the back pressure of the small steam turbine 2; or decreasing the opening of the second regulating valve group 52 to increase the back pressure of the small steam turbine 2. According to the back pressure control requirements of the small steam turbine 2, one or more combinations of control measure one, control measure two, and control measure three are used to achieve the back pressure control requirements of the small steam turbine 2.

[0073] To further expand the adjustable control range of the back pressure of the small steam turbine 2 and achieve the target pressure for back pressure control of the small steam turbine 2 more quickly, preferably, the dual-unit regenerative small steam turbine back pressure control thermodynamic system of this embodiment may also include a third heater 33. The outlet of the third heater 33 is connected to the inlet of the second heater 32, that is, the third heater 33 is the upper stage of the second heater 32. A second steam extraction port is provided downstream of the first steam extraction port on the main steam turbine 1. The second steam extraction port is connected to the third heater 33 through the second steam extraction pipeline 102. Steam is extracted from the second steam extraction port on the main steam turbine 1 by the second steam extraction pipeline 102 and sent to the third heater 33. The third heater 33 is connected in parallel with the third bypass 303, and a third regulating valve group 53 is provided on the third bypass 303. The condensate from the outlet of the third heater 33 mixes with the condensate in the third bypass 303 and enters the second heater 32. If pressure loss and heat dissipation in the third bypass 303 are ignored, the condensate temperature in the third bypass 303 is equal to, and lower than, the condensate temperature at the outlet of the upstream unit (low-pressure heater 36) of the third heater 33. As the opening of the third regulating valve group 53 gradually increases, the temperature of the condensate entering the second heater 32 will gradually decrease, and the flow rate of the condensate entering the third heater 33 will also decrease. Therefore, by adjusting the opening of the third regulating valve group 53, the condensate temperature at the inlet of the second heater 32 can be adjusted, thereby affecting the condensate temperature at the inlet of the first heater 31, and thus regulating the pressure of the first heater 31. As the opening of the third regulating valve group 53 gradually increases, the condensate temperature at the inlet of the second heater 32 decreases, resulting in an increase in the regenerative extraction steam flow rate and a decrease in the regenerative extraction steam pressure of the second heater 32. This, in turn, lowers the condensate temperature at the outlet of the second heater 32, consequently lowering the condensate temperature entering the first heater 31 and reducing the pressure of the first heater 31. Therefore, increasing the opening of the third regulating valve group 53 can reduce the back pressure of the small turbine 2. Conversely, as the opening of the third regulating valve group 53 gradually decreases, the condensate temperature at the inlet of the second heater 32 increases, resulting in a decrease in the regenerative extraction steam flow rate and an increase in the regenerative extraction steam pressure of the second heater 32. This, in turn, raises the condensate temperature at the outlet of the second heater 32, consequently raising the condensate temperature entering the first heater 31 and increasing the pressure of the first heater 31. Therefore, decreasing the opening of the third regulating valve group 53 can increase the back pressure of the small turbine 2.

[0074] Therefore, the back pressure control thermodynamic system of the dual-unit regenerative small steam turbine in this embodiment can control the back pressure of the small steam turbine 2 by adjusting the opening degree of one or more of the first regulating valve group 51, the overflow regulating valve group 61, the second regulating valve group 52 and the third regulating valve group 53.

[0075] Based on this, the control method of the back pressure control thermodynamic system of the dual-unit regenerative small steam turbine in this embodiment also includes control measure four, which is: increasing the opening of the third regulating valve group 53 to reduce the back pressure of the small steam turbine 2; or decreasing the opening of the third regulating valve group 53 to increase the back pressure of the small steam turbine 2. According to the back pressure control requirements of the small steam turbine 2, one or more combinations of control measure one, control measure two, control measure three, and control measure four are used to achieve the back pressure control requirements of the small steam turbine 2.

[0076] Preferably, the back pressure control thermal system of the dual-unit regenerative small steam turbine in this embodiment may further include a high-pressure heater 35. The outlet of the deaerator 34 is connected to the inlet of the high-pressure heater 35, that is, the high-pressure heater 35 is the lower stage of the deaerator 34. A third extraction port is provided on the main steam turbine 1 upstream of the first extraction port. In this embodiment, the steam inlet pipe 201 is connected to the main steam turbine 1, and the third extraction port on the main steam turbine 1 is located upstream of the steam inlet pipe 201. The third extraction port is connected to the high-pressure heater 35 through the third extraction pipe 103, and steam is extracted from the third extraction port of the main steam turbine 1 by the third extraction pipe 103 and sent into the high-pressure heater 35. The small steam turbine 2 has a second small steam extraction port upstream of the first small steam extraction port. The second small steam extraction port is connected to the high-pressure heater 35 through the second small steam extraction pipeline 204. Steam is drawn from the second small steam extraction port of the small steam turbine 2 by the second small steam extraction pipeline 204 and sent into the high-pressure heater 35. In this embodiment, multiple high-pressure heaters 35 can be arranged in series.

[0077] Preferably, the back pressure control thermal system of the dual-unit regenerative small steam turbine in this embodiment may further include a low-pressure heater 36, the outlet of which is connected to the inlet of the third heater 33, i.e., the low-pressure heater 36 is the upper stage of the third heater 33. A fourth extraction port is provided downstream of the second extraction port on the main steam turbine 1. The fourth extraction port is connected to the low-pressure heater 36 through a fourth extraction pipe 104, and steam is extracted from the fourth extraction port of the main steam turbine 1 through the fourth extraction pipe 104 and sent to the low-pressure heater 36. In this embodiment, multiple low-pressure heaters 36 may be connected in series.

[0078] Therefore, in this embodiment, a regenerative unit is formed by multiple low-pressure heaters 36, a third heater 33, a third bypass 303, a third regulating valve group 53, a second heater 32, a second bypass 302, a second regulating valve group 52, a first heater 31, a first bypass 301, a first regulating valve group 51, a deaerator 34, and multiple high-pressure heaters 35. The regenerative extraction steam is provided to the regenerative unit by the extraction steam from the main turbine 1, the extraction steam from the small turbine 2, and the exhaust steam from the small turbine 2. The condensate passes sequentially through the low-pressure heater 36, the third heater 33 (the third heater 33 and the third bypass 303), the second heater 32 (the second heater 32 and the second bypass 302), and the first heater 31 (the first heater 31 and the first bypass 301) into the deaerator 34, and is finally heated in the high-pressure heater 35 to meet the requirements for feedwater.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A dual-turbine regenerative small steam turbine back pressure control thermal system, comprising a main steam turbine (1), a small steam turbine (2), a first heater (31), a second heater (32), and a working mechanism (4) connected to the small steam turbine (2), wherein the outlet of the second heater (32) is connected to the inlet of the first heater (31), characterized in that, The exhaust port of the small steam turbine (2) is connected to the first heater (31) through the exhaust pipe (202). The first heater (31) is connected in parallel with the first bypass (301), and the first bypass (301) is equipped with a first regulating valve group (51). The main steam turbine (1) is equipped with a first extraction port, which is connected to the second heater (32) through the first extraction pipe (101). The exhaust pipe (202) and the first extraction pipe (101) are connected by a... The overflow pipe (6) is connected to the small steam turbine (2), and the overflow pipe (6) is provided with an overflow regulating valve group (61). The back pressure of the small steam turbine (2) is controlled by the opening of the first regulating valve group (51) and / or the overflow regulating valve group (61). The outlet of the first heater (31) is connected to the inlet of the deaerator (34). The small steam turbine (2) is provided with a first small turbine extraction port, and the first small turbine extraction port is connected to the deaerator (34) through the first small turbine extraction pipe (203).

2. The dual-unit regenerative small steam turbine back pressure control thermodynamic system according to claim 1, characterized in that, The second heater (32) is connected in parallel with the second bypass (302), and the second bypass (302) is provided with a second regulating valve group (52).

3. The dual-unit regenerative small steam turbine back pressure control thermodynamic system according to claim 2, characterized in that, It also includes a third heater (33), the outlet of which is connected to the inlet of the second heater (32). The main steam turbine (1) has a second steam extraction port downstream of the first steam extraction port. The second steam extraction port is connected to the third heater (33) through a second steam extraction pipeline (102). The third heater (33) is connected in parallel with the third bypass (303). The third bypass (303) is equipped with a third regulating valve group (53).

4. The dual-unit regenerative small steam turbine back pressure control thermodynamic system according to claim 1, characterized in that, It also includes a high-pressure heater (35), the outlet of the deaerator (34) is connected to the inlet of the high-pressure heater (35), the main steam turbine (1) is provided with a third steam extraction port upstream of the first steam extraction port, the small steam turbine (2) is provided with a second small steam extraction port upstream of the first small steam extraction port, the third steam extraction port and the second small steam extraction port are respectively connected to the high-pressure heater (35) through the third steam extraction pipeline (103) and the second small steam extraction pipeline (204).

5. The dual-unit regenerative small steam turbine back pressure control thermodynamic system according to claim 3, characterized in that, It also includes a low-pressure heater (36), the outlet of which is connected to the inlet of the third heater (33), and a fourth steam extraction port is provided on the main steam turbine (1) downstream of the second steam extraction port. The fourth steam extraction port is connected to the low-pressure heater (36) through the fourth steam extraction pipeline (104).

6. A control method for a dual-unit regenerative small steam turbine back pressure control thermodynamic system as described in any one of claims 1 to 5, characterized in that, include: Control measure 1: Adjust the opening of the first regulating valve group (51) to increase or decrease, so that the back pressure of the small steam turbine (2) increases or decreases. Control measure 2: Adjust the opening of the overflow regulating valve group (61) to increase or decrease, so that the back pressure of the small steam turbine (2) decreases or increases; According to the back pressure control requirements of the small steam turbine (2), the control measures one and / or the control measures two are adopted to achieve the back pressure control requirements of the small steam turbine (2).

7. The control method for the back pressure control thermodynamic system of a dual-unit regenerative small steam turbine according to claim 6, characterized in that, The second heater (32) is connected in parallel with the second bypass (302), and the second bypass (302) is provided with a second regulating valve group (52); the control method of the dual-unit regenerative small steam turbine back pressure control thermodynamic system further includes: Control measure three: Adjust the opening of the second regulating valve group (52) to increase or decrease, so that the back pressure of the small steam turbine (2) decreases or increases; According to the back pressure control requirements of the small steam turbine (2), one or more of the control measures one, control measures two and control measures three are adopted to achieve the back pressure control requirements of the small steam turbine (2).

8. The control method for the back pressure control thermodynamic system of a dual-unit regenerative small steam turbine according to claim 7, characterized in that, The dual-unit regenerative small steam turbine back pressure control thermal system further includes a third heater (33), the outlet of which is connected to the inlet of the second heater (32). The main steam turbine (1) has a second extraction port downstream of the first extraction port. The second extraction port is connected to the third heater (33) through a second extraction pipe (102). The third heater (33) is connected in parallel with a third bypass (303). A third regulating valve group (53) is provided on the third bypass (303). The control method of the dual-unit regenerative small steam turbine back pressure control thermal system further includes: Control measure four: Adjust the opening of the third regulating valve group (53) to increase or decrease, so that the back pressure of the small steam turbine (2) decreases or increases; According to the back pressure control requirements of the small steam turbine (2), one or more of the control measures one, two, three and four are adopted to achieve the back pressure control requirements of the small steam turbine (2).

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