Steam inlet structure for low-pressure waste heat steam turbine unit and control method of steam inlet structure

Abstract

The invention relates to a steam turbine set technology, and particularly discloses a steam inlet structure for a low-pressure waste heat steam turbine and a control method of the steam inlet structure. The steam inlet structure comprises a steam inlet pipe, the steam inlet pipe is divided into a steam inlet upstream pipe section and a steam inlet downstream pipe section which are matched in a spaced mode according to the steam flowing direction, and a switch type butterfly valve is connected to the steam inlet upstream pipe section. A first steam inlet adjusting branch pipe and a second steam inlet adjusting branch pipe are connected between the steam inlet upstream pipe section and the steam inlet downstream pipe section in parallel, the first steam inlet adjusting branch pipe is connected with a pneumatic adjusting valve, and the second steam inlet adjusting branch pipe is connected with an adjusting type butterfly valve. The high-precision adjusting control performance is achieved, forming is achieved by means of complementary matching of the pneumatic adjusting valve and the adjusting type butterfly valve, the large-steam-inlet-flow working condition environment of a low-pressure waste heat steam turbine unit is effectively met, the steam inlet structure is simplified, the manufacturing cost of the unit is greatly reduced, and the working efficiency of the unit is improved. And particularly, the method has good popularization value and technical significance in a low-pressure large-flow waste heat generator set in isolated network operation.

Description

Technical Field

[0001] The present invention relates to steam turbine technology, in particular to a steam inlet structure for a low-pressure waste heat steam turbine unit, and a control method based on the steam inlet structure, which is particularly suitable for a low-pressure waste heat steam turbine unit in an isolated network operation mode. Background Art

[0002] A low-pressure waste heat steam turbine unit is a device that uses low-pressure waste heat steam generated in industrial production processes to generate electricity, and is usually in an isolated grid operation mode.

[0003] Since the steam inlet pressure of the low-pressure waste heat steam turbine unit is low, it has the technical characteristics of large steam inlet specific volume (i.e., large volume occupied by a given mass of steam). In order to meet the requirements of the low-pressure waste heat steam turbine unit to form a large steam inlet flow rate and to reduce the steam inlet pressure loss as much as possible, the inlet valve diameter of its steam inlet structure is often designed to be larger, so the valve configuration of the unit is usually dominated by a large-diameter hydraulic lift type integral valve structure. This large-diameter hydraulic lift type integral valve structure is based on the large size of the valve shell and the large number of valve core parts of the casting structure, which makes its molding structure complex and the overall weight large. The matching hydraulic system has the characteristics of many control components and complex structure, which ultimately leads to the high cost of the molded integral valve structure.

[0004] At present, no effective technical means to reduce the construction cost of the steam inlet valve structure suitable for the low-pressure waste heat steam turbine unit has been disclosed.

[0005] Although the sleeve-type control valve has the technical characteristics of good regulating performance, it is limited by the technical characteristics that the valve diameter generally does not exceed DN500, and is only suitable for steam turbine units with small steam inlet flow conditions, that is, it cannot be used for low-pressure waste heat steam turbine units with large steam inlet flow.

[0006] Although the three-eccentric butterfly valve can be used in large steam inlet flow conditions, it is limited by the working characteristics of the specific molding structure, and the flow characteristics and regulation control accuracy are poor. Specifically, the commonly used three-eccentric butterfly valve can maintain a high linear proportional regulation within the opening range of 10-90%, but the regulation accuracy is poor within the opening range of 0-10% and 90-100%, which shows that it is not conducive to achieving the technical purpose of accurate turbine speed control by flow regulation.

[0007] Therefore, the currently commonly used sleeve-type regulating valve or three-eccentric butterfly valve is not suitable for direct use in low-pressure waste heat steam turbine units with large steam inlet flow. In order to improve the technical problems of large size, heavy weight and high cost of the steam inlet valve structure used in low-pressure waste heat steam turbine units, it is necessary to carry out targeted steam inlet structure design based on the operating characteristics of low-pressure waste heat steam turbine units. Summary of the invention

[0008] The technical purpose of the present invention is to provide a steam inlet structure for a low-pressure waste heat steam turbine unit that can achieve high-precision regulation and control, meet the operating environment of large steam inlet flow, simplify the molding structure and reduce the construction cost, as well as a control method based on the steam inlet structure in view of the particularity of the above-mentioned low-pressure waste heat steam turbine unit and the shortcomings of the prior art.

[0009] The technical purpose of the present invention is achieved by the following technical solution: a steam inlet structure for a low-pressure waste heat steam turbine unit, comprising a steam inlet pipe; The steam inlet pipe is divided into an upstream steam inlet pipe section and a downstream steam inlet pipe section with matching spacing according to the steam flow direction, and the upstream steam inlet pipe section is connected to a switch type butterfly valve; A steam inlet regulating branch pipe 1 and a steam inlet regulating branch pipe 2 are connected in parallel between the steam inlet upstream pipe section and the steam inlet downstream pipe section. The steam inlet regulating branch pipe 1 is connected to a pneumatic regulating valve, and the steam inlet regulating branch pipe 2 is connected to a regulating butterfly valve.

[0010] As one of the preferred technical solutions, the maximum flow rate Q1 of the upstream steam inlet pipe section is equal to the maximum flow rate Q2 of the downstream steam inlet pipe section; The maximum flow rate Q1 of the upstream steam inlet pipe section is the sum of the maximum flow rate Q3 of the steam inlet regulating branch pipe one and the maximum flow rate Q4 of the steam inlet regulating branch pipe two.

[0011] As one of the preferred technical solutions, the valve design diameter of the switch type butterfly valve on the upstream steam inlet pipe section is designed to have a 1:1 matching relationship between the maximum flow Q1 of the upstream steam inlet pipe section and the maximum flow of the switch type butterfly valve.

[0012] As one of the preferred technical solutions, the switch type butterfly valve is a switch type hydraulic or pneumatic three-eccentric butterfly valve structure with hard seal.

[0013] As one of the preferred technical solutions, the valve design diameter of the pneumatic control valve on the steam inlet regulating branch pipe 1 is designed to have a 1:1 matching relationship between the steam inlet capacity when the unit is transferred to an initial 10% load state and the maximum flow of the pneumatic control valve.

[0014] As one of the preferred technical solutions, the pneumatic regulating valve is a sleeve-type pneumatic regulating valve.

[0015] As one of the preferred technical solutions, the valve design diameter of the regulating butterfly valve of the steam inlet regulating branch pipe 2 is designed to be 1 to 1.1 times the difference between the maximum flow rate Q1 of the steam inlet upstream pipe section and the maximum flow rate Q3 of the steam inlet regulating branch pipe 1.

[0016] As one of the preferred technical solutions, the regulating butterfly valve is a regulating hydraulic or pneumatic three-eccentric butterfly valve structure with hard seal.

[0017] As one of the preferred technical solutions, the low-pressure waste heat steam turbine is an isolated-grid operated low-pressure waste heat steam turbine.

[0018] A control method for the steam inlet structure of the low-pressure waste heat steam turbine unit, the control method comprising the following technical means: When the unit is started, the on-off butterfly valve on the upstream steam inlet pipe section is first opened, and then the opening of the pneumatic regulating valve on the first steam inlet regulating branch pipe is gradually increased, and the steam inlet flow of the steam turbine is adjusted by the regulating characteristics of the pneumatic regulating valve; After the unit stabilizes to the rated speed, the opening of the regulating butterfly valve on the second steam inlet regulating branch pipe is gradually increased to 10%, and the pneumatic regulating valve is in a fully open state at this time, and the steam inlet flow of the steam turbine is adjusted by gradually increasing the opening of the regulating butterfly valve until the regulating butterfly valve is in a fully open state; When the unit needs to be shut down, the regulating butterfly valve on the second steam inlet regulating branch pipe is first reduced, and then the pneumatic regulating valve on the first steam inlet regulating branch pipe is reduced, and the regulating butterfly valve and the pneumatic regulating valve are gradually reduced in sequence until they are all closed.

[0019] The beneficial technical effect of the present invention is: the above-mentioned technical measures are aimed at the particularity of the above-mentioned low-pressure waste heat steam turbine unit, and two regulating branches are formed on the steam inlet pipe in a parallel arrangement relationship. One regulating branch is used to connect a pneumatic regulating valve with excellent regulating performance used in a small steam inlet flow operating environment, and the other regulating branch is used to connect a regulating butterfly valve that can adapt to a large steam inlet flow operating environment, so that the pneumatic regulating valve and the regulating butterfly valve with regulating function are coordinated with the upstream on-off butterfly valve serving as the steam inlet main valve, and the pneumatic regulating valves and the regulating butterfly valves on the two regulating branches form a complementary coordination. That is to say, in the above technical measures, the pneumatic control valve and the regulating butterfly valve arranged in parallel form a complementary match, so that the sleeve-type pneumatic control valve with excellent regulating performance used in the working environment of small steam inlet flow rate can supplement the regulating performance of the regulating butterfly valve with poor regulating accuracy in the opening range of 0-10% and 90-100% used in the working environment of large steam inlet flow rate. In this way, the function of the regulating butterfly valve used in the working environment of large steam inlet flow rate to maintain a relatively high linear proportional regulating characteristic in the opening range of 10-90% is utilized, and the function of the excellent regulating performance of the pneumatic control valve used in the working environment of small steam inlet flow rate is utilized to supplement and improve the regulating accuracy of the regulating butterfly valve in the opening range of 0-10% and 90-100%. Through the above-mentioned technical measures, the high-precision regulation and control performance of the original large hydraulic valve is achieved, and it is formed with the help of the complementary cooperation of conventional pneumatic regulating valves and regulating butterfly valves, which effectively meets the large steam inlet flow operating conditions of low-pressure waste heat steam turbine units, simplifies the steam inlet structure, and greatly reduces the cost of the unit. It has good promotion value and technical significance, especially in low-pressure and large-flow waste heat power generation units operating in isolated grids. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A structural schematic diagram of the present invention.

[0021] Figure 2 for Figure 1 Schematic diagram of the structure of the three-eccentric butterfly valve with hard seal used in.

[0022] Figure 3 for Figure 1 Schematic diagram of the structure of the sleeve type pneumatic control valve used in.

[0023] The meaning of the codes in the figure are as follows: 1—upstream section of the steam inlet pipe; 2—downstream section of the steam inlet pipe; 3—on-off butterfly valve; 4—steam inlet regulating branch pipe 1; 5—pneumatic regulating valve; 6—steam inlet regulating branch pipe 2; 7—regulating butterfly valve; A1—valve body; A2—butterfly plate; A3—valve stem; A4—bracket; A5—driving device; B1—valve body; B2—valve seat; B3—sleeve; B4—valve plug; B5—valve stem; B6—valve cover. DETAILED DESCRIPTION

[0024] The present invention relates to a steam turbine unit technology, specifically a steam inlet structure for a low-pressure waste heat steam turbine unit, and a control method based on the steam inlet structure, which is particularly suitable for a low-pressure waste heat steam turbine unit in an isolated grid operation mode. Figure 1 , Figure 2 and Figure 3 The technical solution of the present invention is explained clearly and in detail.

[0025] It should be noted that the drawings of the present invention are schematic, and unnecessary details have been simplified to clarify the technical purpose of the present invention, so as to avoid blurring the technical solution of the present invention that contributes to the prior art. In addition, the expressions "approximately", "substantially" and the like regarding quantity or matching relationship in the following text mean that reasonable assembly errors and processing errors in the industry are allowed to exist, and do not literally express absolute quantities or matching relationships.

[0026] See also Figure 1 As shown, the present invention is a steam inlet structure for a low-pressure waste heat steam turbine unit in an isolated network operation mode, comprising a steam inlet pipe composed of an upstream steam inlet pipe section 1 and a downstream steam inlet pipe section 2. The upstream steam inlet pipe section 1 and the downstream steam inlet pipe section 2 are matched according to the steam flow direction spacing, the upstream end of the upstream steam inlet pipe section 1 is used for sealing connection with the steam source, and the downstream end of the downstream steam inlet pipe section 2 is used for sealing connection with the cylinder, and the upstream steam inlet pipe section 1 is connected with a switch-type butterfly valve 3 as a steam inlet main valve for opening / closing. Between the upstream steam inlet pipe section 1 and the downstream steam inlet pipe section 2, a steam inlet regulating branch pipe 1 4 and a steam inlet regulating branch pipe 2 6 are connected in parallel, that is, the upstream steam inlet pipe section 1 and the downstream steam inlet pipe section 2 are bifurcated to form a steam inlet regulating branch pipe 1 4 and a steam inlet regulating branch pipe 2 6, a pneumatic regulating valve 5 for regulation is connected to the steam inlet regulating branch pipe 1 4, and a regulating butterfly valve 7 for regulation is connected to the steam inlet regulating branch pipe 2 6.

[0027] In the above steam inlet structure, the following flow coordination relationship needs to be formed: - The maximum flow rate Q1 of the upstream steam inlet pipe section 1 is equal to the maximum flow rate Q2 of the downstream steam inlet pipe section 2, that is, the two are in a 1:1 matching relationship; - The maximum flow rate Q1 of the upstream steam inlet pipe section 1 is the sum of the maximum flow rate Q3 of the steam inlet regulating branch pipe 1 4 and the maximum flow rate Q4 of the steam inlet regulating branch pipe 2 6, that is, Q1 = Q3 + Q4; - The valve design diameter (DN) of the on-off butterfly valve 3 on the upstream steam inlet pipe section 1 is designed to have a 1:1 matching relationship between the maximum flow Q1 of the upstream steam inlet pipe section 1 and the maximum flow of the on-off butterfly valve 3; - The valve design diameter (DN) of the pneumatic control valve 5 on the steam inlet regulating branch pipe 1 4 is designed to have a 1:1 matching relationship between the steam inlet capacity when the unit is rushed to the initial 10% load state and the maximum flow of the pneumatic control valve 5; -The valve design diameter (DN) of the regulating butterfly valve 7 of the steam inlet regulating branch pipe 2 6 is designed to be 1.1 times the difference between the maximum flow rate Q1 of the steam inlet upstream pipe section 1 and the maximum flow rate Q3 of the steam inlet regulating branch pipe 1 4, that is, 1.1*(Q1-Q3), forming a certain redundant design.

[0028] The above-mentioned switch type butterfly valve 3 and the above-mentioned regulating type butterfly valve 7 have the same structure, and both adopt a hydraulic or pneumatic three-eccentric butterfly valve structure with hard sealing. When the unit is shut down, the switch type butterfly valve 3 and the regulating type butterfly valve 7 can both realize fast closing and sealing functions to quickly isolate the external steam from the turbine. Of course, during the operation of the unit, the regulating type butterfly valve 7 needs to assume the function of regulating the steam inlet flow.

[0029] See also Figure 2 As shown, the three-eccentric butterfly valve with hard seal has a valve body A1, a flow channel with a straight cylindrical structure in the valve body A1, a valve plate A2 installed in the valve body A1 and located on the flow channel, a valve stem A3 with one end inserted into the valve body A1 and connected to the valve plate A2 in the valve body A1 and the other end extending out of the valve body A1, a bracket A4 connected to the part where the valve stem A3 extends out of the valve body A1 and used to support the driving device A5, and a driving device A5 on the bracket A4 used to connect the valve stem A3 and generate a rotational drive for the valve stem A3. The aforementioned driving device A5 is a hydraulic structure or a pneumatic structure. The three-eccentric butterfly valve with hard seal itself is a conventional structure.

[0030] The pneumatic regulating valve 5 is a sleeve-type pneumatic regulating valve.

[0031] See also Figure 3 As shown, the sleeve-type pneumatic control valve has a valve body B1, a streamlined curved flow channel in the valve body B1, a valve seat B2 located in the middle of the flow channel and in the valve body B1, a sleeve B3 surrounding the valve seat B2 and separating the flow channel to form a valve cavity, a plurality of throttling holes around the sleeve B3, a valve cover B6 connected to the valve body B1 to block the valve cavity in the valve body B1, a valve plug B4 located in the valve cavity of the valve body B1 and forming a telescopic fit with the sleeve B3, and a valve stem B5 with one end inserted into the valve cavity of the valve body B1 and connected to the valve plug B4 and the other end extending out of the valve body B1. The valve stem B5 is used to connect to the actuator outside the valve body B1. The sleeve-type pneumatic control valve itself is a conventional structure.

[0032] The control method of the above-mentioned low-pressure waste heat steam turbine unit with steam inlet structure includes the following technical means: When the unit is started, the on-off butterfly valve 3 on the upstream steam inlet pipe section 1 is first opened, and then the opening of the pneumatic regulating valve 5 on the steam inlet regulating branch pipe 1 4 is gradually increased, and the excellent regulating characteristics of the pneumatic regulating valve 5 are used to adjust the steam inlet flow of the steam turbine, so as to achieve the function of controlling the speed of the steam turbine unit; After the unit stabilizes to the rated speed, the opening of the regulating butterfly valve 7 on the steam inlet regulating branch pipe 2 6 is gradually increased to 10%, and the pneumatic regulating valve 5 is in a fully open state at this time. The steam inlet flow of the steam turbine is adjusted by gradually increasing the opening of the regulating butterfly valve 7 until the regulating butterfly valve 7 is in a fully open state, reaching the maximum steam inlet of the steam turbine unit, and the unit is running at full load; When the unit needs to be shut down, the regulating butterfly valve 7 on the steam inlet regulating branch pipe 2 6 is firstly reduced, and then the pneumatic regulating valve 5 on the steam inlet regulating branch pipe 1 4 is reduced. The regulating butterfly valve 7 and the pneumatic regulating valve 5 are gradually reduced in sequence until they are all closed. When the unit is shut down, the switch butterfly valve 3 and the regulating butterfly valve 7 can both realize the fast closing and sealing functions to quickly isolate the external steam from the turbine.

[0033] As mentioned above, conventional pneumatic control valves and regulating butterfly valves are used to form a parallel arrangement at the steam inlet of the low-pressure waste heat steam turbine unit. The two valves form a complementary cooperation in the parallel arrangement relationship, effectively meeting the large steam inlet flow operating conditions of the low-pressure waste heat steam turbine unit, with high regulation accuracy, simplifying the steam inlet structure, and greatly reducing the cost of the unit.

[0034] The above specific technical solutions are only used to illustrate the present invention rather than to limit it.

[0035] Although the present invention is described in detail with reference to the above specific technical solutions, those skilled in the art should understand that they can still modify the above specific technical solutions or replace some of the technical features therein by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the present invention.

Claims

1. A steam inlet structure for a low-pressure waste heat steam turbine unit, comprising a steam inlet pipe; Features: The steam inlet pipe is divided into a steam inlet upstream pipe section (1) and a steam inlet downstream pipe section (2) with matching spacing according to the steam flow direction, and the steam inlet upstream pipe section (1) is connected to an on-off butterfly valve (3); A steam inlet regulating branch pipe 1 (4) and a steam inlet regulating branch pipe 2 (6) are connected in parallel between the steam inlet upstream pipe section (1) and the steam inlet downstream pipe section (2); a pneumatic regulating valve (5) is connected to the steam inlet regulating branch pipe 1 (4), and a regulating butterfly valve (7) is connected to the steam inlet regulating branch pipe 2 (6).

2. According to claim 1, the steam inlet structure for the low-pressure waste heat steam turbine unit, Features: The maximum flow rate Q1 of the upstream steam inlet pipe section (1) is equal to the maximum flow rate Q2 of the downstream steam inlet pipe section (2); The maximum flow rate Q1 of the steam inlet upstream pipe section (1) is the sum of the maximum flow rate Q3 of the steam inlet regulating branch pipe 1 (4) and the maximum flow rate Q4 of the steam inlet regulating branch pipe 2 (6).

3. According to claim 1, the steam inlet structure for the low-pressure waste heat steam turbine unit, Features: The valve design caliber of the on-off butterfly valve (3) on the upstream steam inlet pipe section (1) is designed so that the maximum flow rate Q1 of the upstream steam inlet pipe section (1) and the maximum flow rate of the on-off butterfly valve (3) form a 1:1 matching relationship.

4. The steam inlet structure for a low-pressure waste heat steam turbine unit according to claim 1 or 3, Features: The on-off butterfly valve (3) is an on-off hydraulic or pneumatic three-eccentric butterfly valve structure with a hard seal.

5. According to claim 1, the steam inlet structure for the low-pressure waste heat steam turbine unit, Features: The valve design diameter of the pneumatic control valve (5) on the steam inlet control branch pipe 1 (4) is designed so that the steam inlet capacity when the unit is switched to an initial 10% load state and the maximum flow rate of the pneumatic control valve (5) are in a 1:1 matching relationship.

6. The steam inlet structure for a low-pressure waste heat steam turbine unit according to claim 1 or 5, Features: The pneumatic regulating valve (5) is a sleeve-type pneumatic regulating valve.

7. The steam inlet structure for a low-pressure waste heat steam turbine unit according to claim 1, Features: The valve design diameter of the regulating butterfly valve (7) of the second steam inlet regulating branch pipe (6) is designed to be 1 to 1.1 times the difference between the maximum flow rate Q1 of the upstream steam inlet pipe section (1) and the maximum flow rate Q3 of the first steam inlet regulating branch pipe (4).

8. The steam inlet structure for a low-pressure waste heat steam turbine unit according to claim 1 or 7, Features: The regulating butterfly valve (7) is a regulating hydraulic or pneumatic three-eccentric butterfly valve structure with a hard seal.

9. The steam inlet structure for a low-pressure waste heat steam turbine unit according to claim 1, Features: The low-pressure waste heat steam turbine is an isolated grid-operated low-pressure waste heat steam turbine.

10. A method for controlling a steam inlet structure for a low-pressure waste heat steam turbine unit according to any one of claims 1 to 9, It is characterized in that The control method includes the following technical means: When the unit is started up, the on-off butterfly valve (3) on the upstream steam inlet pipe section (1) is first opened, and then the opening of the pneumatic control valve (5) on the first steam inlet regulating branch pipe (4) is gradually increased, and the steam inlet flow rate of the steam turbine is adjusted according to the regulating characteristics of the pneumatic control valve (5); After the unit stabilizes at the rated speed, the opening of the regulating butterfly valve (7) on the second steam inlet regulating branch pipe (6) is gradually increased to 10%, and the pneumatic regulating valve (5) is in a fully open state at this time, and the steam inlet flow rate of the steam turbine is adjusted by gradually increasing the opening of the regulating butterfly valve (7) until the regulating butterfly valve (7) is in a fully open state; When the unit needs to be shut down, the regulating butterfly valve (7) on the second steam inlet regulating branch pipe (6) is first reduced, and then the pneumatic regulating valve (5) on the first steam inlet regulating branch pipe (4) is reduced, and the regulating butterfly valve (7) and the pneumatic regulating valve (5) are gradually reduced in sequence until they are all closed.

Images