Ultra-low vacuum steam injection vacuum system suitable for steam turbine cylinder switching operation condition

Abstract

The invention discloses an ultralow vacuum steam jet vacuum system suitable for a steam turbine cylinder switching operation condition, which comprises a first-stage steam jet pump, a second-stage steam jet pump, a third-stage steam jet pump, a first condenser and a steam conveying main pipe which are used under a normal condition, and further comprises a cylinder switching steam jet pump and a second condenser, wherein the cylinder switching steam-jet pump is respectively communicated with the condenser and the first-stage steam-jet pump, the second-stage steam-jet pump and the third-stage steam-jet pump through connecting pipelines, and a first regulating valve is arranged between the cylinder switching steam-jet pump and the condenser; the second condenser is respectively communicated with the cylinder switching steam-jet pump and the first-stage steam-jet pump through connecting pipelines, and a first switching valve is arranged between the second condenser and the first-stage steam-jet pump; and a second switching valve is arranged between the first-stage steam-jet pump and the condenser. The vacuum of the unit can be further improved during cylinder cutting operation of the unit; free switching of different working conditions is realized; and the ultra-low load operation safety of the unit is improved.

Description

Technical Field

[0001] The invention relates to a vacuum steam jet vacuum system, in particular to an ultra-low vacuum steam jet vacuum system suitable for a turbine cylinder cutting operation condition. Background Art

[0002] With the change of the load characteristics of power grid, the country has higher and higher requirements for the flexibility and peak load regulation of thermal power units, and has put forward the requirement of operating at 20% load or even lower load. The implementation of low-pressure cylinder zero output (cylinder cutting) transformation is currently a more mature technical route for deep peak load regulation flexibility transformation of heating units on the market. However, there are also some problems with cylinder cutting technology, mainly manifested in the safety of low-pressure cylinder secondary and final blades. After the steam inlet of the low-pressure cylinder is cut off, in order to ensure the safety of the unit, a small amount of cooling steam is generally designed to be introduced, but the cooling steam flow rate is much smaller than the steam inlet volume under normal conditions. When operating under a small volume flow rate, there is a problem of overheating of the low-pressure cylinder secondary and final blades caused by the blast loss caused by blast friction. There are problems such as excessive cylinder expansion difference or cylinder overheating deformation, which cause dynamic and static friction, dynamic and static center change vibration, etc., which pose a risk to the safety of the steam turbine.

[0003] (1) Dynamic stress problem of the last stage blades. After the steam inlet to the low-pressure cylinder is cut off, only a small amount of cooling steam enters the low-pressure cylinder. The decrease in steam volume causes the internal flow field of the low-pressure flow to be turbulent, especially in the last stage, where the steam flow falls off the blade surface and forms a gathering phenomenon in the reverse flow vortex area. The vortex may cause irregular steam flow excitation, causing a sudden increase in dynamic stress on the blades, which will seriously threaten the safe operation of the blades.

[0004] (2) The problem of last-stage blade blowing. The exhaust volume of the low-pressure cylinder is insufficient, and the last-stage blade enters the blowing state. In addition, the non-condensable air brought in by the cooling steam also aggravates the blowing effect. When the blade is in the blowing state, the exhaust temperature rises sharply, which can easily cause the low-pressure cylinder to deform, resulting in changes in the low-pressure cylinder bearing elevation and the allowable stress value of the material, posing a risk of insufficient strength; the elastic modulus of the last-stage blade material changes, the dynamic frequency decreases, and there is a risk of resonance; the elongation of the last-stage blade changes, and there is a risk of dynamic and static friction.

[0005] (3) Water erosion of the last stage blades. When operating under low volume flow conditions, the flow field of the blades changes greatly, and flow is separated at the root and vortices are formed at the top. The larger water droplets in the steam flow wash the blades with the steam backflow, causing serious water erosion of the blades. Especially when the cylinder is cut, a large amount of low-pressure cylinder water is sprayed to reduce the exhaust temperature. Since the root of the blade is in the backflow area, the sprayed water is easily inhaled, causing serious water erosion in the root area of ​​the blade. If it is operated for a long time under this condition, it will bring serious safety hazards to the blades.

[0006] To this end, we designed an ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation conditions to solve the above problems. Summary of the invention

[0007] According to an embodiment of the present invention, an ultra-low vacuum steam jet vacuum system suitable for a turbine cylinder cutting operation condition is provided, comprising a primary steam jet pump, a secondary steam jet pump, a tertiary steam jet pump, a first condenser and a steam transmission main pipe used under normal conditions, wherein the above-mentioned devices are connected through a connecting pipeline, and further comprising: A cylinder cutting steam jet pump, which is connected to the condenser and the first, second and third stage steam jet pumps through connecting pipes, and a first regulating valve is arranged between the cylinder cutting steam jet pump and the condenser; A second condenser, the second condenser is connected to the cylinder cutting steam jet pump and the first-stage steam jet pump through connecting pipes, and a first switching valve is provided between the second condenser and the first-stage steam jet pump; The first-stage steam jet pump is connected to the condenser through a connecting pipe, and a second switching valve is arranged between the first-stage steam jet pump and the condenser.

[0008] Furthermore, a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger are arranged in the first condenser, and the three are connected in sequence.

[0009] Furthermore, the cooling water source of the second condenser adopts closed water or open water; the temperature of the cooling water source of the second condenser is lower than the temperature of the cooling water source of the first condenser.

[0010] Furthermore, the cylinder cutting steam jet pump adopts an adjustable steam jet pump.

[0011] Furthermore, a powered steam inlet valve is provided on the steam transmission main pipe.

[0012] Furthermore, it also includes: a second regulating valve, which is arranged on the connecting pipeline at the inlet of the cylinder cutting steam injection pump.

[0013] Furthermore, it also includes: a third regulating valve, which is arranged on the connecting pipeline at the inlet of the first-stage steam jet pump.

[0014] Furthermore, it also includes: a fourth regulating valve, which is used to adjust the steam intake of the second and third stage steam injection pumps.

[0015] The ultra-low vacuum steam jet vacuum system suitable for the turbine cylinder cutting operation condition according to the embodiment of the present invention can further improve the unit vacuum when the unit is operating in cylinder cutting operation, and improve the influence of the last stage blowing of the low-pressure cylinder of the turbine; it is combined with the conventional steam jet vacuum system used for normal operating conditions to realize free switching of different conditions; the exhaust steam temperature under the blowing condition when the low-pressure cylinder is cut off is reduced, and the ultra-low load operation safety of the unit is improved; the system is simple and the operation and maintenance workload is small.

[0016] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the technology as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 2 is a working principle diagram according to an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings to further illustrate the present invention.

[0019] First, combine Figure 1 An ultra-low vacuum steam jet vacuum system suitable for a turbine cylinder cutting operation condition according to an embodiment of the present invention is described. The system is used in a steam turbine and has a wide range of application scenarios.

[0020] like Figure 1 As shown, the ultra-low vacuum steam jet vacuum system suitable for the turbine cylinder cutting operation condition according to the embodiment of the present invention comprises a primary steam jet pump 1, a secondary steam jet pump 2, a tertiary steam jet pump 3, a first condenser 4 and a steam transmission main pipe used under normal working conditions, and the above-mentioned devices are connected through connecting pipes, and further comprises: The cylinder cutting steam jet pump 6 is connected with the condenser and the first, second and third stage steam jet pumps through connecting pipes respectively, and a first regulating valve 7 is arranged between the cylinder cutting steam jet pump 6 and the condenser; the cylinder cutting steam jet pump 6 is only used for the cylinder cutting condition; in addition, the suction pressure of the cylinder cutting steam jet pump 6 under the cylinder cutting condition can be reasonably designed to achieve the lowest possible condenser back pressure under the premise of ensuring the safety of the low-pressure cylinder, so as to further reduce the back pressure of the normal operation of the unit; A second condenser 8, the second condenser 8 is connected to the cylinder cutting steam jet pump 6 and the first-stage steam jet pump 1 through connecting pipes, and a first switching valve 9 is provided between the second condenser 8 and the first-stage steam jet pump 1; The primary steam jet pump 1 is connected to the condenser through a connecting pipe, and a second switching valve 10 is provided between the primary steam jet pump 1 and the condenser.

[0021] Further, if Figure 1As shown, in this embodiment, a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger are disposed in the first condenser 4, and the three are connected in sequence.

[0022] Further, if Figure 1 As shown, in this embodiment, the cooling water source of the second condenser 8 adopts closed water or open water; the temperature of the cooling water source of the second condenser 8 is lower than the temperature of the cooling water source of the first condenser 4.

[0023] Further, if Figure 1 As shown, in this embodiment, the cylinder cutting steam jet pump 6 adopts an ultra-low vacuum steam jet pump.

[0024] Further, if Figure 1 As shown, in this embodiment, the cylinder cutting steam jet pump 6 adopts an adjustable steam jet pump.

[0025] Further, if Figure 1 As shown, in this embodiment, a powered steam inlet valve 51 is provided on the steam transmission main pipe.

[0026] Further, if Figure 1 As shown, in this embodiment, it also includes: a second regulating valve 11, and the second regulating valve 11 is arranged on the connecting pipe of the inlet of the cylinder cutting steam injection pump 6.

[0027] Further, if Figure 1 As shown, in this embodiment, it also includes: a third regulating valve 12, and the third regulating valve 12 is arranged on the connecting pipe of the inlet of the first-stage steam jet pump 1.

[0028] Further, if Figure 1 As shown, in this embodiment, it also includes: a fourth regulating valve 13, and the fourth regulating valve 13 is used to adjust the steam intake amount of the second and third stage steam injection pumps 3.

[0029] Furthermore, in this embodiment, temperature and pressure monitoring devices are provided on each steam and cooling water pipeline of the system, and real-time measurement data is connected to the DCS system.

[0030] Working principle: When the unit is operating normally, the first switching valve 9 is closed and the second switching valve 10 is opened, the third regulating valve 12 and the fourth regulating valve 13 are opened, and the normal vacuum of the unit is maintained by the first, second and third stage steam jet pumps 1-3 under normal operating conditions.

[0031] When the unit is running in cylinder cutting mode, the first regulating valve 7 is opened, the first switching valve 9 is opened and the second switching valve 10 is closed. The cylinder cutting steam jet pump 6 cooperates with the first, second and third stage steam jet pumps 1 to 3 under normal operating conditions to work together to further improve the condenser vacuum value. By monitoring the exhaust temperature change of the turbine, the power steam intake of the cylinder cutting steam jet pump 6 and the other three steam jet pumps is controlled, and the suction capacity of each jet pump is adjusted to achieve the purpose of reducing the exhaust temperature.

[0032] Above, refer to Figure 1 An ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation conditions according to an embodiment of the present invention is described, which can further improve the unit vacuum when the unit is operating under cylinder cutting conditions, and improve the influence of the last stage blowing of the low-pressure cylinder of the turbine; it is combined with the conventional steam jet vacuum system used for normal operating conditions to achieve free switching of different conditions; the exhaust steam temperature under the blowing condition when the low-pressure cylinder is cut off is reduced, and the ultra-low load operation safety of the unit is improved; the system is simple and the operation and maintenance workload is small.

[0033] It should be noted that, in this specification, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0034] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. An ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation, comprising a primary steam jet pump, a secondary steam jet pump, a tertiary steam jet pump, a first condenser and a steam transmission main pipe used under normal working conditions, wherein the above-mentioned equipment are connected through a connecting pipeline, characterized in that: Also includes: A cylinder cutting steam jet pump, wherein the cylinder cutting steam jet pump is connected to the condenser and the first, second and third stage steam jet pumps through connecting pipes, and a first regulating valve is arranged between the cylinder cutting steam jet pump and the condenser; a second condenser, the second condenser being connected to the cylinder cutting steam jet pump and the first-stage steam jet pump through connecting pipes, and a first switching valve being arranged between the second condenser and the first-stage steam jet pump; The first-stage steam jet pump is connected to the condenser through a connecting pipe, and a second switching valve is arranged between the first-stage steam jet pump and the condenser.

2. The ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation condition according to claim 1, characterized in that: The first condenser is provided with a primary heat exchanger, a secondary heat exchanger and a tertiary heat exchanger, which are connected in sequence.

3. The ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation condition according to claim 1, characterized in that: The cooling water source of the second condenser adopts closed water or open water; the temperature of the cooling water source of the second condenser is lower than the temperature of the cooling water source of the first condenser.

4. The ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation according to claim 1, characterized in that: The cylinder cutting steam jet pump adopts an adjustable steam jet pump.

5. The ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation condition according to claim 1, characterized in that: The steam transmission main pipe is provided with a powered steam inlet valve.

6. The ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation according to claim 1, characterized in that: It also includes: a second regulating valve, which is arranged on the connecting pipeline at the inlet of the cylinder cutting steam injection pump.

7. The ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation according to claim 1, characterized in that: It also includes: a third regulating valve, which is arranged on the connecting pipeline at the inlet of the first-level steam jet pump.

8. The ultra-low vacuum steam jet vacuum system suitable for turbine cylinder cutting operation condition according to claim 1, characterized in that: It also includes: a fourth regulating valve, and the fourth regulating valve is used to adjust the steam intake amount of the second and third stage steam injection pumps.

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