Method of pre-operational cleaning of water and steam systems in combined cycle power plants and combined cycle power plant arranged therefor

Abstract

To provide a method of pre-operational cleaning of water and steam systems in combined cycle power plants.SOLUTION: Provided is a method comprising: performing a pre-operational initial flushing and chemical cleaning operation on a water and steam system of a combined cycle power plant (1); starting a gas turbine engine (2) and test-driving it; and performing a validation steam blow procedure including a steam blow operation during test-driving of the gas turbine engine, wherein steam is generated in an HRSG (3), the steam is flowed to a part of a closed flow circuit, and steam-carrying components of the HRSG and steam lines (39-51) connecting the HRSG to a steam turbine system (4) are cleaned, wherein the steam is routed to bypass the steam turbine system via operational bypass lines (52-54), without using any temporary piping, and is discharged to a condenser (6); and monitoring and validating cleanliness of selected steam-blown steam lines (39-54).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to pre - operation cleaning of new or repaired parts of a combined cycle power plant, and more particularly, to a pre - operation cleaning method for a system using water and steam in a combined cycle power plant.

Background Art

[0002] In a combined cycle power plant, a gas turbine engine and a steam turbine engine are combined and used to generate electricity. In a combined cycle power plant, the gas turbine engine is thermally connected to the steam turbine engine through a heat recovery steam generator (HRSG). The HRSG is a non - contact type heat exchanger that can heat the feed water for the steam generation process with the exhaust gas that would otherwise be wasted from the gas turbine engine. The HRSG is a large duct in which a tube bundle is arranged, and the water flowing through the tube bundle is heated by the exhaust gas flowing through the duct and turned into steam.

[0003] Current combined cycle power plants use multi - pressure HRSGs, which have three different operating pressures (high pressure, medium pressure, low pressure) and are equipped with components for generating steam at various pressures and temperatures. The HRSG includes, for example, a low - pressure section, a medium - pressure section, and a high - pressure section, and each of the low - pressure section, medium - pressure section, and high - pressure section can generally include one or more economizers, evaporators, and / or superheaters. The steam at each pressure is used as the steam supplied to the corresponding stage of the steam turbine system. The gas turbine system and the steam turbine system drive one or two generators for generating electricity.

[0004] The used steam from the steam turbine system is exhausted to a condenser, where the steam condenses, and then the condensate is returned from the condenser to the HRSG via one or more conduits by a condensate pump.

[0005] In the operation of a power plant, the purity of the steam must meet strict requirements. It is important to avoid situations where particulate debris is entrained in the steam, causing interference with the operation of the power plant or damage to the components of the power plant. For example, particulate debris can clog steam screens or narrow steam passages. Particulate debris can potentially damage stationary and rotating components of the steam turbine by erosion and impact, and can also clog or damage the inner surfaces of steam valves used to control the steam flow.

[0006] During the manufacture and construction of a combined cycle power plant, contaminants (such as welding spatter, cuttings, welding electrode residues, mud, sand, dust, etc.) may remain in the system despite all precautions. The contaminants may exist in a form that is easy to remove, or they may adhere to the inner walls of the components of the power plant.

[0007] Accordingly, in typical prior art methods of starting up newly refurbished steam turbine generator equipment, numerous methods have been employed to remove particulate contamination from the inner surfaces of steam transport equipment and piping (such as in the HRSG region, the steam lines between the HRSG and the steam turbine system, the steam lines connected to the condenser, and control valves). Generally, such steam transport components are purged or flushed of contaminants prior to the first steam pulse and prior to each subsequent steam pulse sent to the steam turbine system, and prior to commissioning the gas turbine engine, to ensure that no particulate contaminants are present before startup.

[0008] Pre - operation cleaning methods in the art include cleaning the components of the steam - water system with treated water and chemical cleaning procedures (including hot alkaline degreasing, acid cleaning, passivation, rinsing and / or air - blow cleaning), and then inspecting the drums and low - point headers and manually cleaning or rinsing the deposits in the drums and low - point headers. Only then does the gas turbine engine and the entire combined cycle power plant begin operation.

[0009] It is also known to perform a steam blow procedure to clean a steam generator and associated steam lines by using steam that is discharged to the atmosphere via a temporary pipe and a silencer installed in an isolation valve and a control valve of a steam turbine. The steam blow can be performed continuously or discontinuously (pulse blow), and is generally performed under low load and low exhaust pressure so as to reach a desired disturbance coefficient. As some other methods, there is a method of combining a steam load to the atmosphere and a condenser through a temporary pipe. Although steam is also discharged to the condenser in normal bypass operation without reaching a high disturbance coefficient and without performing target verification of components of a cleaned water-steam system, it is less efficient than required.

[0010] US2009 / 0107532A1 discloses a method for pre-operation cleaning of plant components in a power plant. This method includes continuously supplying a medium to a closed flow path circuit so that the medium flows through one or more plant components to be cleaned, and testing the medium to measure the purity of the plant components during operation. Steam is extracted from a steam boiler device, the liquid obtained from the steam in a condenser is supplied to the plant components during operation, and is sent to the closed flow path circuit to clean the plant components by the steam. In order to bypass the high-pressure stage of a steam turbine unit, a branch is provided from a high-pressure steam line to a temporary cleaning facility equipped with a temporary steam line system, a blowout insert, and a measuring device arranged between the blowout inserts. The measuring device is a polished metal baffle plate, which is installed in the steam line horizontally with respect to the flow direction, and the purity of the medium can be visually observed and determined by particle impact colliding with the baffle plate during the blowout operation. This method requires the temporary installation of a steam line system to perform the steam blow procedure. The temporary steam line system and the temporary blowout facility must be removed during the normal operation of the power plant. Therefore, the amount of work, cost, and time required for pre-operation cleaning increase.

[0011] US10612771B2 discloses a method for pre - operation cleaning of the water - steam system in a combined cycle power plant. This method performs a simple pre - operation cleaning, first releases steam into the atmosphere using temporary piping, and then blows steam into the condenser using another piping that bypasses the bypass valve on the line to the condenser, including a steam blow to the condenser. The temporary piping and equipment are designed to be able to operate at base load or up to 100% load. To monitor and confirm the cleanliness of the exhaust steam, a highly polished metal - plate - shaped target insert is inserted into and removed from the steam blow exhaust for inspection, so as to determine whether particulate contaminants in the exhaust steam continuously exist. The steam blow procedure is efficient and can be carried out during the commissioning of the gas turbine engine. However, the corresponding configuration, re - configuration workload, material requirements, and costs are significantly increased due to the temporary piping, temporary equipment, and temporary controls required for the entire verification steam blow procedure. Furthermore, since the first steam blow is discharged into the atmosphere, an atmospheric silencer must be provided and used at the exhaust point of the steam to the atmosphere to avoid excessive noise pollution.

[0012] Conventional methods for pre - operation cleaning of steam - generating devices and piping use large - scale and temporary piping, involving corresponding configuration and re - configuration workloads, required personnel, and material costs. Conventional methods require an atmospheric silencer and perform a steam blow to the atmosphere that requires a large amount of demineralized water. Conventional methods cannot be carried out in parallel with the normal commissioning of the gas turbine engine, and / or conventional methods are time - consuming and costly to implement.

[0013] The object of the present disclosure is to provide a novel pre - operation cleaning method using the effective steam blow of the water - steam system of a combined cycle power plant, and to overcome one or more of the above - mentioned multiple drawbacks of the conventional pre - operation cleaning method. This method must be able to efficiently clean the steam - water system, and preferably, by being executed at least partially in parallel with the trial operation of the gas turbine system, it is possible to reduce the ignition time, fuel consumption, and demineralized water consumption in the gas turbine system during pre - operation cleaning. Furthermore, this method must be free of safety concerns, free of visual pollution, and comply with noise and exhaust gas regulations.

[0014] Another object of the present disclosure is to provide a combined cycle power plant configured to perform such pre - operation cleaning.

Summary of the Invention

[0015] To achieve the above object, according to one aspect of the present invention, a pre - operation cleaning method for the water - steam system in a combined cycle power plant is provided. The combined cycle power plant includes a gas turbine engine, a steam turbine system, a condenser, and a heat recovery steam generator (HRSG). The method includes the following: performing initial flushing and chemical cleaning before operation on the water - steam system of the finally constructed combined power plant, burning the gas turbine engine, and performing a trial operation of the gas turbine engine; while the gas turbine engine is being trial - operated, generating steam in the HRSG, and performing a verification steam blowing procedure including a steam blowing operation of blowing steam at high speed, high temperature, and a cleaning power ratio condition through a part of a closed flow path for cleaning the steam conveyance part of the HRSG and the steam line connecting the HRSG and the steam turbine, wherein the steam is routed to bypass the steam turbine system through a permanent operation bypass line without using temporary piping and is discharged to the condenser, and monitoring and verifying the cleanliness of the selected steam blow steam line.

[0016] In the method of the present invention, the normal start-up of the gas turbine system is carried out in parallel with the verification spraying procedure. In particular, in the normal complete gas turbine commissioning operation, driving the gas turbine to the full speed no load (FSNL) state in bypass operation, performing synchronous operation and HRSG safety valve test, setting the load of the gas turbine system to the base load for combustion adjustment with the fuel gas strainer attached, and performing other general commissioning operations can be carried out. The power plant can be started up in its normal configuration without performing temporary control or manual control. Since no temporary piping or lines are required, the configuration and reconfiguration of the plant for performing pre-cleaning are minimized.

[0017] The temporary pipeline or line is understood to mean a steam pipeline or steam line that is required and installed only for the cleaning process (for example, required and installed to bypass the steam turbine system). In contrast, the permanent operating piping or operating line is required and installed for normal operation, for example, to bypass the steam turbine system under specific operating conditions (such as load shedding). In the method of the present invention, since such temporary piping, temporary compressors, temporary outflow means, and temporary controls are not required, the labor, time, and cost related to personnel and materials for performing pre-cleaning can be significantly reduced.

[0018] In addition, by means of the verification blow method for the condenser, the release of steam into the atmosphere is avoided as is done in some conventional pre-operation cleaning methods. Therefore, it is possible to maintain the cycle water quality, reduce noise, and limit the consumption of demineralized water to minimize visual pollution. Furthermore, by performing the commissioning of the gas turbine system in parallel with the verification blow procedure, the ignition time and fuel consumption of the gas turbine system can be reduced, and compliance with emission standards can be achieved during high-load steam blowing. Since the power plant is in normal operation including all normal regulatory and protective means, there are no safety concerns. By using the heat cycle and the maximum cycle temperature, efficient cleaning can be achieved. Through large-scale pre-operation cleaning with a condenser included in the steam flow path, high-quality steam can be obtained early, and the cycle is operated at high load under vacuum.

[0019] In the latest generators of gas turbine systems, the exhaust temperature of the gas turbine engine is high. This method is not restricted by the limitations of some dry steam sections of the HRSG and is not restricted by the design temperature of temporary piping that may require additional temperature adjustment. In the latest generators of gas turbine engines, the steam flow rate has increased significantly, and a significant amount of demineralized water is consumed in conventional pre-cleaning methods. As a result, in conventional systems, the temporary piping and its installation are gradually becoming larger.

[0020] In the method of the present invention, the operations of initial flushing and chemical cleaning before operation can include generally known chemical cleaning procedures (such as open flushing or closed flushing, high-temperature degreasing, pickling, passivation, and rinsing, etc.). Chemical cleaning can be performed on the entire steam-water system (including the HRSG drum, economizer, evaporator, superheater, reheater, steam lines of the balance of plant, auxiliary steam lines, feed water lines, and condensate system). In some specific cases, if the steam piping from the HRSG to the steam turbine is mechanically cleaned in another way (for example, shot blasting after prefabrication and cleaning after installation, or hydro-blasting and inspection after installation), pickling may be limited to the water-steam system of the HRSG. After the chemical cleaning is completed, extensive inspections can be carried out at various locations including the low points and HRSG collectors. These locations can be washed with high-pressure water jets to remove the solid deposits remaining from the chemical cleaning. Together with the steam blowing procedure, all the contaminants (such as sand, dust, mud, welding spatter, chips, welding electrode residues, etc.) of all the steam generating plants that may remain in the system after the manufacture and construction of the power plant can be efficiently removed before the initial startup of the power plant.

[0021] In any of the methods described above, while the gas turbine engine is operating under base load conditions or maximum load conditions, the steam blowing operation can be advantageously carried out. The steam transport part of the HRSG to be steam blown, the steam lines, and the operation bypass lines (including bypass valves) can be designed such that the cleaning force ratio (CFR) is at least 1.1, and further at least 1.2, respectively. During the trial operation, the gas turbine engine is loaded at base load to achieve the desired required CFR for efficient cleaning of the steam system.

[0022] The overall steam blow procedure and calculations can be significantly simplified if well integrated in the initial design and concept phases. During the initial engineering and procurement stages of a new combined cycle power plant construction project, engineers can calculate various steam blow cases so that the HRSG and steam lines have sufficient CFR. Examples of steam blows can be included in the bypass function specifications among other normal operating scenarios, and pipeline and bypass suppliers can appropriately size the bypass lines and bypass valves according to the examples of steam blows. Therefore, the need for specific equipment for the verification blow procedure is reduced.

[0023] To determine the steam bypass capacity for verification steam blows, when operating the gas turbine engine at base load in the steam bypass under realistic ambient conditions expected for the steam blow, it is possible to check at what pressure each piping section must be operated in order to exceed the expected CFR at the available steam flow rate. For this purpose, normal ambient conditions can usually be considered, and normal ambient conditions are generally acceptable.

[0024] In a preferred application example of the above method, the HRSG can have a plurality of pressure stages (including a high pressure (HP) stage, an intermediate pressure (IP) stage, and a low pressure (LP) stage), and a reheater. The steam turbine system can include an HP steam turbine, an IP steam turbine, and an LP steam turbine. As the steam lines to be blown, there are an HP steam line for supplying HP steam from the HP stage of the HRSG to the HP steam turbine, an IP steam line connecting the IP stage of the HRSG to the reheater, a high temperature reheater (HRH) line for supplying IP steam from the reheater to the IP steam turbine, a low temperature reheater (CRH) line that receives used HP steam from the HP steam turbine and supplies the used HP steam to the reheater, an operating HP bypass line arranged between the HP steam line and the CRH line, an operating HRH bypass line arranged between the HRH line and the condenser, and an operating LP bypass line arranged between the LP steam line and the condenser. At least the design of the permanent operating piping lines includes determining and arranging the sizes of at least the HP steam line, the IP steam line, the HRH line, the CRH line, the LP steam line, the HP bypass line, the HRH bypass line, and the LP bypass line so that the cleaning force ratio (CFR) is at least 1.1, preferably at least 1.2.

[0025] In the above embodiment, the method includes providing an adjustable sacrificial trim designed to improve the flow coefficient (CV) capacity of at least some of the bypass valves among the plurality of bypass valves of the operating HP bypass line, the operating HRH bypass line, and the operating LP bypass line in order to maintain a cleaning force ratio (CFR) of at least 1.2 in a single HRSG plant configuration and at least 1.03 in a plurality of HRSG plant configurations.

[0026] Only during the verification blow procedure, by attaching a sacrificial trim to the bypass valve, damage to the operating trim can be prevented, and the value of the flow coefficient of the bypass valve can be increased. The sacrificial trim may have reduced durability and can be removed from the bypass valve when the verification steam blow procedure is completed. The permanent trim is included in the bypass valve for normal operation, sized based on examples of maximum loads excluding examples of steam blows, and can have high strength and excellent durability.

[0027] In some embodiments, when designing the sacrificial trim, a margin of, for example, about 10% can be added to the required valve flow coefficient CV of the sacrificial trim so that the cleaning force ratio CFR required under the actual operating conditions at the site can be obtained. For the HP bypass line, a sacrificial trim can be provided that provides the maximum CV that can accommodate the valve body so that a verification blow can be performed under base load conditions. In some embodiments, the sacrificial trim is composed of a piston with an associated gasket and a cage, and the cage can, for example, increase the number of holes and / or increase the size of the holes so that the volumetric flow rate of the steam passing through the cage can be increased and the velocity of the steam can be increased.

[0028] When designing the HP bypass line and the HP bypass valve, a bypass temperature adjustment flow rate may be required, and the bypass temperature adjustment flow rate can also be considered. The set temperature for HP bypass temperature adjustment can be set based on the expected CRH pressure, similar to normal bypass temperature adjustment control, but the expected CRH pressure during steam blow is used.

[0029] The above-described embodiments of the method can further include arranging the branch connection portions of the operating HP bypass line, HRH bypass line, and LP bypass line at a position as close as possible to the steam turbine system, which is near and immediately upstream of the valve assemblies for controlling and shutting off the HP steam turbine, IP steam turbine, and LP steam turbine. "As close as possible" means that the bypass line is located as close as possible to the steam turbine system within an acceptable and admissible range so as not to be affected by factors such as the turbine building and the type of condenser. The bypass line is not installed in the HRSG area, especially the HRSG pipe rack, but is installed near the steam turbine system. The HRH bypass line and LP bypass line can be directly installed in the steam turbine area. The HP bypass line is not directly installed in the steam turbine area, but is installed as close as possible thereto within an acceptable and admissible range. The check valve of the CRH line and the downstream connection portion of the HP bypass line to the CRH line are also installed as close as possible to the HP steam turbine. In this way, the steam transport components and a certain portion of the length of the steam line can be cleaned by steam blowing.

[0030] In any of the above embodiments, the method can further include installing target inserts (preferably inserts in the form of mirror-finished steel plates or highly polished steel plates) in at least the HRH and LP steam lines. The target inserts are configured and arranged such that on-line target inspection and cleanliness monitoring can be performed under the operating conditions of steam temperature and pressure during the verification blow procedure. The target inserts can visually indicate the impact of debris carried by steam blowing.

[0031] In the above embodiments, the method can include installing steam flow meters in the relevant parts of the steam transport components, steam lines, and operating bypass lines of the HRSG during the verification steam blow procedure, and calculating the CFR (cleaning force ratio) in the relevant parts on-line based on the measured values of these steam flow meters.

[0032] The type of the steam flowmeter may be, for example, a Venturi type or a nozzle type. The calculation of CFR can be included as part of the normal plant control software for verifying the cleaning ratio during the verification blow.

[0033] The above embodiment of the present method may further include providing an inspection port / cleaning port at a portion where the steam blow of the steam line is not executed, and after the verification blow procedure is completed, inspecting and cleaning, if necessary, the portion where the steam blow is not executed. The cleaning can be carried out, for example, by rinsing with demineralized water. All important flow paths and dead legs, etc., can be ensured to be substantially free of contaminants.

[0034] In an advantageous embodiment of the method described above, at least some of the branch connection parts of the plurality of branch connection parts of the HP bypass line, the HRH bypass line, and the LP bypass line are straight with respect to their respective bypass lines, but not straight with respect to their respective steam turbine sections, in order to reduce the accumulation of debris in the dead legs upstream of the respective steam turbine sections. Thereby, the time for inspecting and cleaning the important flow paths can be saved. Also, some of the ports of the plurality of ports for inspection and cleaning that are usually required can be omitted. This technique is particularly applicable to configurations without a steam shut-off valve or configurations without a portion upstream of the steam shut-off valve. This technique is particularly important in the case of an HP steam line where it is difficult to add an inspection flange or an inspection port. In addition, recent research has shown that erosion of the steam turbine valve during long-term operation of the plant can be suppressed by providing a line straight with respect to the bypass line.

[0035] The above-described embodiments of the present method can be further applied to a combined cycle power plant including a multi-unit configuration including a single steam turbine system, a first unit including a first HRSG and a first gas turbine engine, and a second unit including a second HRSG and a second gas turbine engine. The method preferably includes performing a verification blow procedure independently between units. This can be easily achieved because there is no common part of the units. Preferably, the verification blow procedures of the first unit and the second unit are executed successively with respect to each other. In an advantageous embodiment, the verification blow procedure of one of the first unit and the second unit is executed, and at the same time, in the other unit, inspection and cleaning of the dead leg after the verification blow procedure can be executed. Thereby, the time for completing the pre-operation cleaning can be saved.

[0036] In some embodiments of a method applied to a combined cycle power plant including a multi-unit configuration, the method can include performing a verification blow in one of the first unit and the second unit and flowing verification steam using at least one bypass line and a bypass valve in the other unit. Thereby, it is possible to avoid making the size of the bypass valve of the bypass line too large.

[0037] As an alternative, the connection between the HP steam line and the HRH warming line can be used for a multi-unit power plant configuration so that the size of the HP bypass valve does not become too large. During the verification steam blow, the pressure of the HP bypass line can be reduced using both the HP bypass line and the line connecting the HP connected to the HRH warming line.

[0038] In some embodiments of the above-described method applied to a combined cycle power plant including a multi-unit configuration, if the HP bypass valve cannot achieve sufficient CFR in the HP steam line, or if the portions where HP and CRH blows are not performed cannot be suppressed to a sufficiently narrow range, a modified embodiment of the method may optionally install a temporary jumper pipe with a throttling device from the HP steam turbine valve of the HP steam turbine to the check valve of the CRH line, and size the HRH bypass valve so that at least a cleaning force ratio (CFR) of 1.03 required in the HRH steam system can be obtained. If necessary, a throttling device can be used in the temporary piping to reduce the cleaning force ratio CFR in the HP steam system to a small value. By limited use of a common temporary piping in both units of a power plant with a multi-unit configuration, the use of the HP bypass lines and valves of both units for the steam blow operation is avoided.

[0039] Furthermore, if temporary piping is used, (if the HP steam final temperature regulator exists) the HP steam final temperature regulator can be designed to adjust the temperature of the HP steam before it enters the CRH steam line under maximum steam blow conditions. If the HP final temperature regulator is not available, a specific port may be provided in the HP steam line to allow a temporary temperature regulator to be connected during the verification blow. Except for these points, in each unit of the first unit and the second unit of the multi-unit configuration of the combined cycle power plant, no temporary piping or equipment as described above is used.

[0040] According to another aspect of the present invention, to solve the above-mentioned problems, a combined cycle power plant is provided. The combined cycle power plant includes a gas turbine engine for generating power, a heat recovery steam generator (HRSG) fluidly connected to the gas turbine engine, which receives high-energy exhaust gas generated from the power generation of the gas turbine engine and is configured to generate steam from the high-energy exhaust gas; a steam turbine system fluidly connected to the HRSG through a steam line, which receives the steam generated by the HRSG and is configured to generate additional power from the steam; a condenser coupled to the steam turbine system for condensing the used steam output from the steam turbine system and coupled to a condensate system for returning the condensate from the condenser to the HRSG; an operating bypass line fluidly connected between the steam line and the condenser and arranged to bypass the steam turbine system; and a control system for controlling the normal operation of the gas turbine engine, the HRSG, the steam turbine system, and the condenser to generate power under various operating conditions. The control system is further configured to start the gas turbine engine and conduct a commissioning test on the gas turbine engine; execute a verification steam blow procedure including a steam blow operation while the gas turbine engine is undergoing the commissioning test, that is, generate steam in the HRSG and flow the steam through a part of a closed fluid circuit under high flow rate, temperature, and cleaning power ratio conditions to clean the steam transport components of the HRSG and the steam line connecting the HRSG to the steam turbine system, where the steam bypasses the steam turbine system via the operating bypass line without using temporary piping and is discharged to the condenser; and execute the verification steam blow procedure and monitor and verify the cleanliness of the selected steam-blown steam line, so as to perform pre-operation cleaning of the water-steam system of the combined cycle power plant, including a control system.

[0041] A combined cycle power plant, for example, after a power plant is newly built or repaired, in parallel with the commissioning of the gas turbine system, prepares for the normal operation of the power plant without any need for temporary piping, installation, control, and associated configurations and reconfigurations, thereby realizing the advantages described above in relation to the method of the present invention. Other embodiments of the method described above and related effects and advantages are similarly applicable to the combined cycle power plant. The most preferred embodiment of the combined cycle power plant of the present invention is as follows.

[0042] The control system can be configured to perform a steam blow operation while operating the gas turbine engine at base load (i.e., maximum load condition), and the operating bypass line including the operating piping, steam line, and bypass valve of the HRSG to be steam blown can be designed to obtain a cleaning force ratio CFR of at least 1.03, at least 1.1, and even at least 1.2, respectively.

[0043] In a preferred embodiment of the combined cycle power plant of the above type, the HRSG can have a plurality of pressure stages (including a high pressure (HP) stage, an intermediate pressure (IP) stage, and a low pressure (LP) stage), and a reheater. The steam turbine system can include an HP steam turbine, an IP steam turbine, and an LP steam turbine. The steam lines include an HP steam line for supplying HP steam from the HP stage of the HRSG to the HP steam turbine, an IP steam line connecting the IP stage of the HRSG and the reheater, a high temperature reheater (HRH) line for supplying IP steam from the reheater to the IP steam turbine, a cold reheat (CRH) line for receiving used HP steam from the HP steam turbine and supplying the used HP steam to the reheater, an operating HP bypass line disposed between the HP steam line and the CRH line, an operating HRH bypass line disposed between the HRH line and the condenser, and an operating LP bypass line disposed between the LP steam line and the condenser. At least the HP steam line, IP steam line, HRH line, CRH line, LP steam line, HP bypass line, HRH bypass line, and LP bypass line can be sized and configured such that the cleaning force ratio (CFR) is at least 1.03, at least 1.1, and preferably at least 1.2.

[0044] In a preferred embodiment of the combined cycle power plant, at least some of the bypass valves of the operating HP bypass line, operating HRH bypass line, and operating LP bypass line can be provided with adjustable sacrificial trim designed to increase the flow coefficient (CV) of the bypass valve in order to perform a verification steam blow procedure, whereby a cleaning force ratio (CFR) of at least 1.2 can be obtained in a single HRSG plant configuration and a cleaning force ratio (CFR) of at least 1.03 can be obtained in a plurality of HRSG plant configurations. The sacrificial trim is installed to prevent damage to the operating trim during the verification blow procedure and to improve the value of the flow coefficient of the bypass valve, but in some cases, there is a risk of reduced durability. The sacrificial trim can be removed from the bypass valve when the verification steam blow procedure is completed.

[0045] In the above-described embodiment of the combined cycle power plant, the branch connection portions of the operating HP bypass line, the operating HRH bypass line, and the operating LP bypass line can preferably be arranged at a position as close as possible to the steam turbine system, that is, at a position close to the steam turbine system within an acceptable and receivable range. Further, the branch connection portion is not arranged in the piping rack of the HRSG, away from the HRSG area rather than the steam turbine area, nor directly arranged within the steam turbine area, but can be arranged near the assembly of the control valves and shut-off valves of the HP steam turbine, the IP steam turbine, and the LP steam turbine, and at a position immediately upstream of the assembly. In order to enable a long portion of the operating piping to be steam blown, (if there is a shut-off valve in the CRH line), it is desirable that the downstream connection portion of the shut-off valve and the CRH line to the HP bypass line be arranged at a position as close as possible to the high-pressure steam turbine.

[0046] In the above-described embodiment of the combined cycle power plant, for the verification steam blow procedure, target inserts (preferably inserts in the form of mirror-finished steel plates or highly polished steel plates) are installed in the HRH steam line 49 and the LP steam line 41, respectively, and / or in other steam transportation components and steam transportation lines. The target inserts are preferably configured and arranged so that on-line target inspection and cleanliness monitoring can be performed under the operating conditions of the steam temperature and pressure during the verification blow procedure.

[0047] In the above-described embodiment of the combined cycle power plant, the steam flow meter can be provided in the operating piping, the steam line, and / or the relevant portion of the bypass line of the HRSG to be steam blown, and the control system can be configured to calculate the CFR of the relevant portion based on the steam flow measurement value of the steam flow meter during the verification steam blow procedure. The calculated CFR of the relevant portion is presented to the operator of the power plant on the graphic interface of the control system 9, and the operator can be enabled to confirm that the required CFR has been achieved.

[0048] In the above-described embodiment of the combined cycle power plant, inspection ports / washing ports can be provided at portions of the steam line where steam blowing is not performed so that inspection and washing of portions where steam blowing is not performed can be carried out. Such portions are pickled and washed with high-pressure water, inspected using a borescope, a robot camera, etc., and then the gas turbine engine is ignited and normal operation is performed. The dead legs around the steam turbine system can be inspected during and after the steam blowing procedure. Debris accumulated in the dead legs can be removed by flushing.

[0049] In another advantageous embodiment of the combined cycle power plant described above, at least some of the branch connection portions of the HP bypass line, the HRH bypass line, and the LP bypass line can be provided with T-connections that are straight with respect to their respective bypass lines but not straight with respect to their respective steam turbine sections in order to reduce the accumulation of debris in the dead legs upstream of the respective steam turbine sections. This can save time for inspection and cleaning of important flow paths and can omit some of the inspection / washing ports. Furthermore, erosion of the steam turbine valves during long-term plant operation can be reduced.

[0050] In a preferred application of the above-described embodiment, the combined cycle power plant can include a multi-unit configuration, and the multi-unit configuration includes a single steam turbine system, a first unit including a first HRSG and a first gas turbine engine, and a second unit including a second HRSG and a second gas turbine. In the multi-unit configuration, the control system can be configured to perform a verification blow procedure independently between the units. In particular, the control system can be configured to perform the verification blow procedure for one of the first unit and the second unit, and at the same time, in the other unit, inspection and washing of the dead legs of the other unit after the inspection blow procedure are performed.

[0051] In some embodiments of the above combined cycle power plant, in order not to make the bypass valve too large and / or to avoid installing sacrificial trim on the bypass valve, the control system can use at least one bypass line and bypass valve of the other unit in one of the first unit and the second unit to execute a verification steam blow procedure and configure the verification steam flow to flow into the said one unit.

[0052] As an alternative, in a multi-unit plant configuration, the HP steam line can be connected to the HRH warming line in order not to make the HP bypass valve too large.

[0053] In some other embodiments of the combined cycle power plant, a temporary jumper can be installed between the HP steam turbine valve of the HP steam turbine and the check valve of the CRH line. This is to send HP steam via the jumper and avoid using the HP bypass line and HP bypass valve. The HRH bypass valve can be sized such that the HP and HRH steam systems reach at least 1.1 CFR. These embodiments are particularly advantageous for applications where the HP bypass valve cannot reach sufficient CFR in the HP steam line or for applications where the non-blown parts of HP and CRH are reduced.

[0054] These advantages and features of the present invention, as well as other advantages and features, will become apparent from the following description in conjunction with the drawings.

Brief Description of the Drawings

[0055] The subject matter is regarded as the present invention and is particularly and clearly claimed in the claims. The foregoing features and advantages of the present invention, as well as other features and advantages, will be apparent from the following embodiments for carrying out the invention in conjunction with the accompanying drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0056] Referring now to the drawings, and in particular to FIG. 1, a combined cycle power plant 1 (hereinafter sometimes simply referred to as power plant 1) is shown. The power plant 1 includes a gas turbine engine 2 that generates power, a heat recovery steam generator (HRSG) 3 that is fluidly connected to the gas turbine engine 2 and configured to receive high-energy exhaust gas generated from power generation in the gas turbine engine 2 and generate steam from the high-energy exhaust gas, a steam turbine system 4 that is fluidly connected to the HRSG 3 through a steam line, configured to receive the steam generated in the HRSG, and generate additional power from the steam, a condenser 6 that is coupled to the steam turbine system 4, condenses the used steam output from the steam turbine system 4, and is coupled to a condensate system 7, and returns the condensate from the condenser 6 to the HRSG 3, a generator 8 that is driven by the steam turbine system 4 and the gas turbine engine 2 and generates power, and a control system that is only schematically shown in FIG. 1 in the form of a block 9 and is configured to control the normal operation of the gas turbine engine 2, the HRSG 3, the steam turbine system 4, and the condenser 6 to generate power under various operating conditions. As will be further described below, the control system 9 is further configured to perform a pre-operation cleaning of the water-steam system of the combined cycle power plant 1.

[0057] The gas turbine engine 2 includes a compressor 10 that receives air flowing through an inlet section 11 and compresses the air, a combustor 12 that receives compressed air from the compressor 10 and a fuel flow (e.g., natural gas) from a fuel source (not shown), mixes the compressed air and the fuel, and burns the mixture to generate high-energy exhaust gas, and a turbine section 13 that receives a high-energy exhaust gas flow from the combustor 12. In the turbine section 13, the high-energy exhaust gas expands, and the thermal energy of the exhaust gas is converted into kinetic energy that drives a shaft 14. By the mechanical power of the shaft 14, the compressor 10 and an external load (such as a generator 8) are driven. The high-energy exhaust gas flow flows from the turbine section 13 through an exhaust duct 16 and is sent to the HRSG 3. In the illustrated exemplary embodiment of the power plant 1, the gas turbine engine 2, the steam turbine system 4, and the generator 8 are arranged on a single shaft 14, but other configurations having separate shafts and external loads can also be used.

[0058] The steam turbine system 4 includes, in the illustrated exemplary embodiment of the power plant 1, a high-pressure (HP) steam turbine 17, an intermediate-pressure (IP) steam turbine 18, and a low-pressure (LP) steam turbine 19, and has a plurality of steam introduction points at different pressures. The LP steam turbine 19 is coupled to a condenser 6 and discharges the used steam that has been used for power generation into the condenser 6.

[0059] The HRSG 3 is a counterflow heat exchanger configured to heat feed water flowing through the HRSG 3 using the high-energy exhaust gas received from the gas turbine engine 2 via the exhaust duct 16. The HRSG 3 is associated with the steam turbine system 4 and includes a corresponding plurality of pressure stages (including an HP stage 21, an IP stage 22, and an LP stage 23) and a reheater 24 to generate steam at various pressures and temperatures. The steam is used as a steam supply source for each stage of the steam turbine system 4.

[0060] Each stage of the HP section 21, IP section 22, and LP section 23 of the HRSG3 can generally include one or more drums, economizers, evaporators, OT (once-through) sections, and / or superheaters. For example, the HP section 21 can include an HP drum 26, an HP economizer 27, an HP evaporator 28, and one or more HP superheaters 29. Similarly, the IP section 22 can include an IP drum 31, an IP economizer 32, an IP evaporator 33, and an IP superheater 34. The LP section 23 can include an LP drum 35, an LP economizer 36, an LP evaporator 37, and an LP superheater 38. The economizers, evaporators, and superheaters of the HP section 21, IP section 22, and LP section 23 of the HRSG3, together with the reheater 24, are arranged as tubes or tube bundles inside the HRSG3, and the high-energy exhaust gas flowing through the HRSG3 transfers heat to the fluid (feed water or steam) circulating through the tubes or tube bundles. The multi-pressure HRSG3 having the configuration shown in FIG. 1 is a preferred embodiment of the steam generation facility in the combined cycle power plant 1, but other configurations of the HRSG and other steam generation facilities (such as different types of steam boiler devices) may also be used.

[0061] As shown in FIG. 1, the power plant 1 includes a plurality of steam lines arranged to supply steam generated by the HRSG 3 to the steam turbine system 4. For example, the plurality of steam lines can include an LP steam transfer line 39 fluidly coupled between the LP drum 35 and the LP superheater 38 to supply LP steam, and an LP steam line 41 fluidly coupled between the LP superheater 38 and the LP steam turbine 19. The IP stage 22 of the HRSG 3 can include an IP steam transfer line 42 fluidly coupled between the IP drum 31 and the IP superheater 34, and an IP steam line 43 fluidly coupling the IP superheater 34 to the reheater 24. Optionally, another steam line (not labeled in FIG. 1) can be used to return the IP steam from the IP drum 31 to the LP drum 35. The HP stage 21 of the HRSG 3 can include an HP steam transfer line 44 fluidly coupling between the HP drum 26 and the HP superheater 29, an HP steam transfer line 46 fluidly coupling different portions of the HP superheater 29 if there are different portions, and an HP steam line 47 fluidly coupling between the HP superheater 29 and the HP steam turbine 17 to supply HP steam.

[0062] Furthermore, the reheater 24 can include a reheat steam transfer line 48 fluidly connecting different portions of the reheater 24 if there are different portions, a high temperature reheat (HRH) line 49 fluidly coupled between the output of the reheater 24 and the input of the IP steam turbine 18 to supply IP steam, and a low temperature reheat (CRH) line 51 having one end fluidly coupled to the input of the reheater 24 and the IP steam line 43 and the other end fluidly coupled to the output of the HP steam turbine 17 to receive the used HP steam from the HP steam turbine 17. At least some of the steam lines 39 - 51 can include shut-off valves and / or control valves for shutting off or regulating the steam flow.

[0063] Power plant 1 further includes a permanent bypass system including a plurality of permanent operation steam bypass lines that can be used during normal operation (such as during load shedding) to supply the steam generated by HRSG 3 to condenser 6 by bypassing steam turbine system 4. In particular, the plurality of operation bypass lines can include HP bypass line 52, HRH bypass line 53, and LP bypass line 54. HP bypass line 52 is fluidly coupled between HP steam line 47 and CRH line 51, and HP bypass line 52 includes HP bypass valve 55 installed in HP bypass line 52 to control the HP bypass steam flow flowing through HP bypass line 52. HRH bypass line 53 is fluidly coupled between HRH line 49 and condenser 6, and HRH bypass line 53 includes HRH bypass valve 56 installed in HRH bypass line 53 to control the IP bypass steam flow flowing through HRH bypass line 53. LP bypass line 54 is fluidly coupled between LP steam line 41 and condenser 6, and LP bypass line 54 includes LP bypass valve 57 installed in LP bypass line 54 to control the LP bypass steam flow flowing through LP bypass line 54.

[0064] The condenser 6 is coupled to the steam turbine system 4 (in particular, the LP steam turbine 19), and is a large heat exchanger that receives used steam from the steam turbine system 4, cools and condenses the used steam into water. There are several types of condensers known, but a common design includes a number of small-diameter tubes 58 through which cooling water flows. The steam condensate from the condenser falls into the hot well 59 located at the bottom of the condenser and / or is supplied to the condensate tank 60 (see Figure 2). The condensate system 7 includes a condensate pump 61 and a condensate line 62. The condensate pump 61 returns the steam condensate from the condenser 6 to the HRSG3 via the condensate line 62. On the suction side of the condensate pump 61, a strainer (not shown) can be arranged to remove particulate contamination from the steam condensate supplied from the condensate hot well 59 or the condensate tank 60 (Figure 2) to the condensate pump 61 in order to prevent damage to the condensate pump 61 and other components of the condensate system 7. Although a liquid-cooled deaerating condenser is shown in the embodiment of Figure 1, an appropriate type of condenser (e.g., the air-cooled condenser schematically shown in the embodiment of Figure 2) can be used.

[0065] In normal operation, the gas turbine engine 2 generates mechanical power, which is converted into electrical power by the generator 8. The steam turbine system 4 can generate additional power from the steam received from the HRSG 3. The used steam from the steam turbine system 4 is condensed in the condenser 6 and returned to the HRSG 3 via the condensate system 7. Depending on the load requirements, one or more of the HP steam turbine 17, IP steam turbine 18, and / or LP steam turbine 19 may not be used. In that case, the operating HP bypass line 52, operating HRH bypass line 53, and operating LP bypass line 54 can be used to bypass the respective steam turbine sections. The control valve and stop valve assemblies 63, 64, 65 are disposed at the inlets of the HP steam turbine 17, IP steam turbine 18, and LP steam turbine 19 to stop, open, and control the steam flow to the respective steam turbine stages. The shut-off valve 66 is disposed in the CRH line 51 (e.g., CRH line section 71) downstream of the outlet of the HP steam turbine 17.

[0066] During the manufacture and construction of the combined cycle power plant 1, or during the renovation or inspection of the combined cycle power plant 1, contaminants (such as mud, sand, dust, welding spatter, cuttings, welding electrode residues, debris, and other particulate contaminants) may remain in the system. To prevent contamination and damage to the components of the steam turbine during operation, all steam transport and water transport plant components of the HRSG 3, condenser 6, and condensate system 7, the steam lines connecting the HRSG 3 to the steam turbine system 4 and the condenser 6, and the operating bypass lines 52, 53, 54 must be made free of such contaminating particles. For this purpose, a pre-operation cleaning method for the water-steam system in a combined cycle power plant is provided. Hereinafter, the pre-operation cleaning method of the present disclosure will be described in relation to the combined cycle power plant 1 shown in FIG. 1, but the method can also be applied to other power plants including steam generating facilities.

[0067] As described herein, the pre-operational cleaning method begins with performing an initial flushing and chemical cleaning operation before operation on the water-steam system of the constructed combined cycle power plant 1. Substantially all components and pipelines (e.g., HRSG drum, economizer, superheater and reheater, steam line, auxiliary steam line, bypass line, feed water line, and condensate system) that transport steam or steam condensate are cleaned using treated deionized water to remove contaminants. Further, other chemical cleaning steps (e.g., one or more of hot degreasing, acid cleaning, passivation, rinsing) can be performed. The low points and HRSG collectors can be inspected as necessary and hydrolyzed to remove particulate contaminants. Finally, a preservation process with dry air can be performed.

[0068] When the chemical cleaning operation is completed, as the next step of the pre-operational cleaning method, a verification steam blow procedure is performed. According to this method, the verification steam blow procedure to the condenser is performed during the trial operation of the gas turbine engine.

[0069] Therefore, the gas turbine engine 2 is first ignited and the trial operation of the gas turbine engine 2 is started. The trial operation work of a normal gas turbine engine is performed according to a normal schedule with the gas turbine engine 2 in bypass operation. The normal schedule includes full speed no load (FSNL) operation, a safety valve test of the HRSG3, and an operation of setting the load of the gas turbine engine 2 to the base load (i.e., the maximum rated load) for combustion adjustment and performing combustion adjustment.

[0070] The steam blow procedure for verification is carried out in parallel with the commissioning of the gas turbine engine 2. The steam blow procedure for verification includes a steam blow operation. The steam is generated in the HRSG3 using the high-energy exhaust gas from the gas turbine engine 2. The steam is blown into the steam transportation part of the closed flow circuit formed by the HRSG3, the pipes connecting the HRSG3 to the steam turbine system 4, the bypass lines 52, 53, 54, the condenser 6, and the condensate system 7 under the conditions of high speed, high temperature, and high cleaning power ratio, and the steam transportation components are cleaned. By blowing the steam in this way, the verification steam is guided to bypass the steam turbine system 4 via the permanent bypass system including the permanent HP bypass line 52, the HRH bypass line 53, and the LP bypass line 54, and is discharged into the condenser 6. The condensate generated in the condenser 6 is cleaned as required and returned to the HRSG3. Therefore, a closed loop circuit is formed. The steam blow steam line of the closed loop circuit for verification steam blow is shown as a thick solid line in FIG. 1. The procedure for verification steam blow further includes monitoring and verification of the cleanliness of the steam lines being steam blown in parallel with the steam blow.

[0071] By combining the execution of a verification steam blow on the condenser with the simultaneous parallel execution of the commissioning of a normal gas turbine engine, various advantages can be obtained. The power plant 1 starts up according to its normal configuration without the need for temporary controls and temporary piping that would otherwise be required only for the verification steam blow procedure and are not used during normal operation. Here, the permanent operating HP bypass line 52, HRH bypass line 53, and LP bypass line 54 are used for the verification steam blow to the condenser 6. Since steam and water circulate in a closed circuit, the consumption of demineralized water can be suppressed. Neither noise nor visual pollution is generated, and it complies with emission standards during the steam blow procedure. Furthermore, since the commissioning of a normal gas turbine engine is carried out in parallel, the ignition time and fuel consumption for carrying out this procedure can also be suppressed. Since the power plant 1 is in normal operation, there are no safety concerns. Efficient cleaning is achieved by the heat cycle and high temperature, and the steam quality required for normal operation can be realized cost-effectively in a short time.

[0072] During the steam blow procedure, in order to avoid damage to the equipment being steam blown while achieving the required disturbance coefficient and cleaning efficiency, it is preferable that the verification steam blow process has already been integrated and considered at the initial design or conceptual stage of a project to build a new power plant. The steam blow operation is carried out while the gas turbine engine is operating at base load, and all the operating piping of the HRSG3, steam lines 39 - 51, bypass lines 52 - 54, and bypass valves 55 - 57 should be effectively steam blown, and each of the piping and lines is designed to be suitable for its operating conditions and a cleaning force ratio CFR of at least 1.1, and further at least 1.2. The cleaning force ratio CFR can be calculated as follows.

Number

[0073] To determine the capacity of the steam / water system equipment required for the steam blow procedure, when operating the gas turbine engine at base load under realistic ambient conditions expected for the steam blow, each piping section can be checked at what pressure it must be operated to exceed the expected CFR at the available steam flow rate. Generally, normal ambient conditions can be considered. In the preferred embodiment of the power plant shown in FIG. 1, at least the main bodies of the steam lines 39 to 51, the bypass lines 52 to 54, and the bypass valves 55 to 57 are sized and arranged such that the cleaning force ratio CFR is at least 1.1. More preferably, at least some of these steam lines can be sized and arranged such that the CFR is at least 1.2.

[0074] By performing several preparatory operations, the verification steam blow procedure can be carried out efficiently and safely. In particular, to prevent damage to the operating trim and, if necessary, improve the flow coefficient (CV) capacity of the bypass valves, adjustable sacrificial trim (not shown) can be installed in at least some of the bypass valves of the HP bypass line 52, the HRH bypass line 53, and the LP bypass line 54, namely the HP bypass valve 55, the HRH bypass valve 56, and the LP bypass valve 57 for operation. The permanent trim is sized based on an example of maximum load and determined to have high durability, except in the case of steam blow. In contrast, the sacrificial trim is specially designed to increase the flow coefficient CV or maximize the flow coefficient CV. Durability is a secondary role.

[0075] The sacrificial trim can be designed to support a cleaning power ratio CFR of at least 1.2 in a single HRSG plant configuration and at least 1.03 in a multi-HRSG plant configuration. The required flow coefficient CV of the disposable trim can be calculated based on the estimated conditions, and a margin, for example, 10% - 20%, can be added to the calculated CV to ensure that the required CFR meets the true operating conditions in the field. In the case of the HP bypass valve 55 that is exposed to the maximum load during the steam blow procedure, the disposable trim is preferably designed to provide the maximum CV that can accommodate the valve body.

[0076] In a preferred implementation, the adjustable disposable trim to be installed can be composed of a piston with a gasket and a cage, where the number of holes is increased or the holes are enlarged so that the volumetric flow rate and flow velocity of the steam passing through the cage are increased. The disposable trim is removed and replaced with the final operating trim after the steam blow procedure is completed.

[0077] In the steam blow achieved in bypass operation, if there is a bypass temperature regulating flow rectifier, it is necessary to consider the bypass temperature regulating flow rectifier in the plan for the verification steam blow procedure. For example, the temperature setpoint of the HP bypass line 52 can be set based on the predicted pressure of the CRH line 51 according to the control of normal bypass temperature adjustment, but the predicted pressure of the CRH line during the verification steam blow is used.

[0078] To enable cleaning of long sections of the steam transport piping, the branch points of the permanent operating HP bypass line 52, HRH bypass line 53, and LP bypass line 54 can be located as close as possible to the steam turbine system 4. This means that the branch points are located in an acceptable and receptive range close to the steam turbine system 4 such that they are near the region of the steam turbine system 4, but maintaining a sufficient distance so that the bypass lines 52, 53, 54 are not affected by the steam turbine building, the type of condenser 6, and the operation of the steam turbine building and the condenser. The branch points of the HP bypass line 52, HRH bypass line 53, and LP bypass line 54 are located immediately adjacent to and upstream of the valve assemblies 63, 64, 65 for controlling and shutting off HP, IP, and LP steam. The HP bypass line 52, HRH bypass line 53, and LP bypass line 54 shall not be installed in the area of the HRSG3 (especially the HRSG pipe rack). The HRH bypass line 53 and LP bypass line 54 are directly connected to the condenser 6 and can generally be installed near the condenser 6 in the steam turbine area. The HP bypass line 52 shall not be installed directly in the steam turbine area, but it is advisable to install it as close as possible to the steam turbine area. The check valve 66 of the CRH line 51 and the downstream connection of the HP bypass line 52 to the CRH line 51 are also located as close as possible to the HP steam turbine 17.

[0079] During the verification blow procedure, target inserts are installed in relevant parts of the steam transport piping to enable inspection of targets and monitoring of cleanliness under the operating conditions of steam temperature and pressure. In particular, a first target insert 67 is installed in the HRH line 49 slightly upstream of the HRH bypass line 53 and the valve assembly 64 for controlling and shutting off IP, and a second target insert 68 is installed in the LP steam line 41 slightly upstream of the LP bypass line 54 and the valve assembly 65 for controlling and shutting off LP.

[0080] The target inserts 67, 68 preferably use a mirror plate or a highly polished metal plate made of steel that can withstand the maximum steam conditions and forces of the steam flow in each of the HRH steam line 49 and the LP steam line 41. The target plates of the target inserts 67, 68 are impacted by debris carried by the steam flow during the verification steam blow procedure, and the impact of particles on the target (metal or mirror) plate visually indicates the presence of particle contamination carried by the steam flow.

[0081] Furthermore, in this method of verification steam blow, a steam flow meter (not shown) can be installed in the operating piping of the HRSG3, the steam lines 39 - 51, and the relevant parts of the bypass lines 52 - 54 to measure the steam blow flow rate of these parts. As the steam flow meter (not shown), for example, a Venturi type or a nozzle type can be used. Next, the cleaning force ratio CFR of the relevant parts can be calculated online based on the steam flow rate measurement values received from the steam flow meter during the verification blow procedure. In particular, the calculation of CFR can be included as part of the normal plant control software of the control system 9 to verify the cleaning force ratio during the verification steam blow procedure. The calculated CFR value can be presented to the operator of the power plant 1 through an appropriate graphical interface during the verification steam blow procedure so that it can monitor and verify that the required steam blow conditions are met.

[0082] The pre - operation cleaning method can further include providing inspection ports / cleaning ports (not shown in FIG. 1) at portions where steam blowing of the steam line is not performed, and inspecting and cleaning the portions where steam blowing is not performed after the verification blow procedure is completed. The portions where steam blowing is not performed are indicated by thick dashed lines in FIG. 1 (and other figures), and in particular, the portion 69 of the HP steam line where blowing is not performed between the branch connection of the CRH line 51 of the HP bypass line 52 and the valve assembly 63 for HP control and shut - off; the portion 70 of the HRH line where blowing is not performed between the branch connection of the HRH bypass line 53 to the condenser 6 and the valve assembly 64 for IP control and shut - off; the portion 71 of the CRH line where blowing is not performed between the downstream connection of the HP bypass line 52 to the CRH line 51 and the check valve 66 at the outlet of the HP steam turbine 17; and the portion 72 of the LP steam line where blowing is not performed between the branch connection of the LP bypass line 54 to the condenser 6 and the valve assembly 65 for LP control and shut - off.

[0083] The inspection ports / cleaning ports for the portions 69 - 72 where steam blowing is not performed are provided at appropriate positions so that inspection and cleaning can be easily carried out. The inspection can be performed using a bore scope or a robot equipped with a camera, and contaminants remaining in important parts can be removed by rinsing or other appropriate means. Other inspection ports / cleaning ports can be provided to enable easy access to other piping parts for inspection and cleaning of dead legs, drain ports, etc.

[0084] In some other embodiments of the combined cycle power plant 1, in order to efficiently perform the pre - operation cleaning method, at least some of the branch connection parts of the plurality of branch connection parts of the HP bypass line 52, the HRH bypass line 53, and the LP bypass line 54 are linear with respect to their respective bypass lines 52, 53, or 54, but are realized by T - connections (not shown) that are not linear with respect to their respective steam turbines 17, 18, or 19. With such a configuration, it is possible to reduce the accumulation of debris in the dead legs upstream of their respective steam turbines 17, 18, or 19, inspect important flow paths, and save time for cleaning the fouling of the flow paths. Inspection and cleaning ports may, in some cases, become unnecessary and can be omitted. This option is preferably applied to configurations without steam shut - off valves or configurations without the upstream part of the steam isolation valve, and is particularly important in the case of HP steam where it is difficult to add an inspection flange. By providing a line that is linear with respect to the bypass line, it has been found that, advantageously, erosion of the steam turbine valves during long - term operation of the plant can be suppressed.

[0085] Referring now to FIG. 2, a schematic diagram of a combined cycle power plant 1' including a multi - unit configuration is shown. In the exemplary embodiment shown in FIG. 2, the power plant 1' includes a single steam turbine system 4, a first unit 73 including a first HRSG 3a and a first gas turbine engine 2a, and a second unit 74 including a second HRSG 3b and a second gas turbine engine 2b. The relevant components of the first unit 73 are shown with the addition of "a" using the corresponding reference numerals in FIG. 1, and the corresponding components of the second unit 74 are shown with the addition of "b".

[0086] As can be seen from FIG. 2, the method for pre - operation cleaning of the water - steam system of the combined cycle power plant 1' can advantageously be carried out independently for each of the first unit 73 and the second unit 74 with respect to the other unit. Here too, the steam line for steam blowing is shown by a thick solid line in FIG. 2, and the parts where steam blowing is not carried out are shown by thick dashed lines. The parts where steam blowing is not carried out extend from the bypass branch to the steam turbine valve. All parts where steam blowing is not carried out need to be pre - cleaned, inspected, and verified after chemical cleaning. There is a risk that debris may accumulate in the immediate upstream part of the steam shut - off valve during the verification steam blow, and post - cleaning may be required (assuming that the steam shut - off valve is closed during the verification steam blow to avoid deposits being brought into the downstream part of the steam shut - off valve).

[0087] The inspection blow procedures for the first unit 73 and the second unit 74 may be carried out simultaneously, but are preferably carried out sequentially (i.e., one unit after the other). Also in this case, no temporary piping or temporary control is required for the verification steam blow operation of each of the first unit 73 and the second unit 74. For the steam blow procedure of the condenser 6 carried out in parallel with the normal test run of the gas turbine engines 2a, 2b, only the permanent operating steam lines including the bypass lines 52a, 52b, 53a, 53b, 54a, 54b can be used. Although the condenser 6 in FIG. 2 is shown as an air - cooled condenser, it can be understood that a water - cooled condenser or other types of condensers (e.g., a direct contact condenser (jet condenser)) may also be used.

[0088] In some preferred embodiments, the verification blow procedure is carried out for one of the first unit 73 and the second unit 74, and at the same time, in the other unit, inspection and post - cleaning of the dead legs and other important flow paths of the other unit after the verification blow procedure are carried out. Since generally no common parts are included, the procedures of steam blowing, inspection, and post - cleaning can be carried out independently for each of the first unit 73 and the second unit 74.

[0089] In the combined cycle power plant 1' with a multi-unit configuration shown in FIG. 2, the first unit 73 and the second unit 74 are fluidly coupled to each other through a communication line 76 that connects together the LP steam lines 41a, 41b, the HRH lines 49a, 49b, and the HP steam lines 47a, 47b downstream of the branch connection portions of their respective HP bypass lines 52a, 52b, HRH bypass lines 53a, 53b, and LP bypass lines 54a, 54b. The communication line 76 is not included in the steam blow procedure for verification. During the steam blow procedure for verification, shut-off valves 77a, 77b are incorporated slightly downstream of the respective branch connection portions of the bypass lines 52a, 52b, 53a, 53b, 54a, 54b to block the communication line 76, whereby the steam blow is sent to the condenser 6 via the bypass lines 52a, 52b, 53a, 53b, 54a, 54b, preventing the contamination of these connection / common lines during the steam blow for verification. After chemical cleaning and before the steam blow for verification, the piping section (including the communication line 76 and up to the steam turbines 17, 18, 19) located downstream of the shut-off valves 77a and 77b is subjected to high-pressure water injection, inspected completely (100%), and verified.

[0090] Except for providing the two units 73, 74 and the communication line 76, the configuration of the power plant 1' (particularly the configuration of the steam turbine system 4 and each unit 73, 74) corresponds to the configuration of the power plant 1 in the embodiment of FIG. 1 (particularly the steam turbine system 4 and the combination of the gas turbine engine 2 and the HRSG 3). The operation of these units and, in particular, the pre-operation cleaning method of the water / steam system in the combined cycle power plants 1, 1' also substantially correspond to each other, and the above-described configuration and pre-operation cleaning method and their related technical effects and advantages are similarly applicable to the embodiment of FIG. 2.

[0091] Referring now to FIG. 3, a schematic of a modification of the embodiment of the power plant 1' of FIG. 2 is shown. The entire description of the embodiment of FIG. 2 in combination with the description of the embodiment of FIG. 1 shall apply to the embodiment of FIG. 3 as well, except for the differences described below. The same components in the embodiments of FIGS. 2 and 3 are denoted by the same reference numerals.

[0092] The embodiment of FIG. 3 is essentially different from the embodiment of FIG. 2 in that a temporary jumper 78 is installed from the valve assembly 63 for HP control and shut-off of the HP steam turbine 17 to the check valve 79 on the common CRH line 81 upstream of the branch connection of the CRH lines 51a, 51b of the first unit 73 and the second unit 74. By means of the temporary jumper 78, without using the HP bypass lines 52a, 52b or with less use of the HP bypass lines 52a, 52b, the steam flow in the verification steam flow procedure can be sent directly from the HP steam lines 47a, 47b through the temporary jumper 78 to the CRH lines 51a, 51b. This embodiment is advantageous in applications where the HP bypass valves 55a, 55b cannot reach a sufficient CFR in the HP line or where the range of sections where the steam flow in the HP steam lines 47a, 47b and the CRH lines 51a, 51b is not executed is reduced. The HRH bypass valves 56a, 56b are sized to achieve an appropriate CFR in the HP steam line and the HRH steam line.

[0093] In order not to overheat the CRH lines 81, 51a, 51b and to control the temperature of the steam flowing through the CRH lines, an HP steam terminal temperature regulator (not shown) can be designed and arranged such that the HP steam can be temperature-adjusted before it flows into the common CRH pipe 81 under maximum steam blow conditions. If the HP terminal temperature regulator is not available, a dedicated port can be planned to be provided in the HP steam piping so that a temporary temperature regulator can be connected during the verification blow. All other aspects described above continue to be applicable.

[0094] Figures 4 and 5 show an embodiment of the combined cycle power plant 1' of FIG. 2 in a modified schematic process flow. Generally, the configuration of the power plant shown in FIGS. 4 and 5 corresponds to the configuration of the power plant 1' shown in FIG. 2. In FIGS. 4 and 5, the same reference numerals are assigned to the same components as in FIG. 2, and generally, the above description of the embodiment of FIG. 2 is equally applicable to the embodiments shown in FIGS. 4 and 5. In this plant configuration, only one of the HRSGs, either HRSG3a or 3b, is heated to generate steam, and the other HRSG is in a standby state.

[0095] In the embodiments of FIGS. 4 and 5, only a part of the verification steam blow procedure is slightly modified so that the size of the bypass valves (particularly, the HP bypass valves 55a, 55b of the first unit 73 and the second unit 74) is not too large. For this reason, while the verification steam blow procedure is being executed in one of the first unit 73 and the second unit 74, in the other unit 74 or 73, at least one bypass line and bypass valve are used to send at least a part of the verification steam flow, thereby reducing the volumetric flow rate of the steam in the bypass valve. The flow of the verification steam is shown by thick solid lines in FIGS. 4 and 5.

[0096] In the scenario shown in FIG. 4, the verification steam is supplied to the first unit 73, flows from HRSG3a through the HP superheater 29a to the branch connection of the HP bypass line 52a, and the verification steam flow is split into two parts. The first part of the verification steam flow passes through the HP bypass line 52a and the HP bypass valve 55a, and then is guided to the reheater 24a via the CRH line 51a. The second part of the verification steam flow flows through the connection line 76a that connects the HP steam lines 47a and 47b of the two units 73 and 74 among the plurality of connection lines 76, and then flows into the HP bypass line 52b of the second unit 74. Thereafter, the second part of the verification steam flow returns to the CRH line 51a of the first unit 73 through the HP bypass line 52b, the HP bypass valve 55b, the CRH line 51b, and the other common connection line 76b of the connection line 76, and is mixed with the first part of the verification steam flow and supplied to the reheater 24a of the first unit 73. In order to allow such a verification steam flow to flow, all the control valves and shut-off valves of the HP-steam line 47a, the common connection line 76a, the CRH lines 51a and 51b, and the common connection line 76b need to be open. The combined verification steam flow is then directly discharged from the reheater 24a to the condenser 6 via the HRH line 49a and the HRH bypass line 53a of the first unit 73.

[0097] Similarly, the HP steam flow applied to the second unit 74 during the verification steam flow procedure can be controlled such that the HP steam flow is split, flows through both HP bypass lines 52a and 52b, CRH lines 51a and 51b, and common connection lines 76a and 76b of both units 73 and 74, and then recombined and directly supplied to the condenser 6 through the reheater 24b and the HRH bypass line 53b of the second unit 74.

[0098] In the example shown in FIG. 4, the verification steam blow procedure is not performed independently between the first unit 73 and the second unit 74, but the requirements for the HP bypass lines 52a and 52b and the HP bypass valves 55a and 55b can be relaxed.

[0099] In the modified process flow shown in FIG. 5, the HP steam from the HRSG3a of the first unit 73 flows through the HP steam line 47a, through the HP bypass line 52a and the HP bypass valve 55a, and is sent to the reheater 24a. Next, the first portion of the verification steam flow flows from the reheater 24a through the HRH line 49a of the first unit 73, the HRH bypass line 53a, and the HRH bypass valve 56a and is directly supplied to the condenser 6. The second portion of the verification steam flow branches off at the HRH line 49a downstream of the reheater 24a, flows through the common connection line 76c of the connection line 76, and is sent to the HRH line 49b of the second unit 74. Thereafter, the second portion of the verification steam flow can be sent directly to the condenser 6 via the HRH bypass line 53b and the HRH bypass valve 56b. Thus, the verification steam flow can be split to flow through the HRH bypass lines and bypass valves of both the first and second units 73, 74, thereby relaxing the size requirements imposed on the HRH bypass lines and HRH bypass valves to achieve the required CFR.

[0100] The method for pre - operation cleaning of the water - steam system of a combined cycle power plant according to the present invention, and the technical effects and advantages of the corresponding combined cycle power plant include at least the following. The power plant can be started in its normal configuration without performing temporary control, and a simple start - up sequence is provided. During the first power plant commissioning, since the gas turbine engine is operated at full load (base load), efficient cleaning at high heat cycles and high temperatures can be achieved. High - load condenser cleaning and closed - loop circuit operation enable achieving high - speed steam quality. Generally, no temporary piping and temporary control are required to perform the verification steam blowing procedure. The ignition time can be shortened, and the consumption of natural gas or other fuel gases can be suppressed. The consumption of demineralized water can also be suppressed. The normal commissioning of the gas turbine and generator can be carried out in parallel with the verification blow, reducing the number of shutdowns for re - setting. The time required for the remaining inspection and cleaning of the critical path is minimized. Since the power plant is in normal operation, there are no safety concerns, no noise, and no visual pollution. Since the steam blow is performed with a minimum environmental load, the emissions of gas turbine exhaust gas can be reduced. The selective catalytic reduction (SCR) catalyst can be installed immediately after the verification steam blow during the steam blow stop for inspection and final cleaning. The reason is that the gas turbine engine is already operating at base load, which maximally prevents poisoning of the catalyst by grease and dust from the gas turbine engine and HRSG air ducts, eliminating the need for further stops during hot commissioning. In the multi - unit configuration of a combined cycle power plant, the verification steam blowing procedure can be carried out independently for each unit. Alternatively, the verification steam blowing procedures for both units can be carried out in combination and / or carried out using short temporary jumpers to relax the requirements of the bypass valves used.

Explanation of Signs

[0101] 1, 1’ Combined cycle power plant 2 Gas turbine engine

Claims

1. A method for cleaning a water / steam system in a combined cycle power plant (1, 1') including a gas turbine engine (2), a steam turbine system (4), a condenser (6), and a heat recovery steam generator HRSG (3) before operation, the method comprising: Performing initial flushing and chemical cleaning before operation on the water / steam system of the finally constructed combined cycle power plant (1, 1'); Starting the gas turbine engine (2) and commissioning the gas turbine engine (2); While the gas turbine engine (2) is being commissioned, performing a verification steam blow procedure including a steam blow operation, generating steam in the HRSG (3), and flowing the steam at high flow rate, temperature, and cleaning force ratio conditions through a part of a closed fluid circuit to clean the steam transport components of the HRSG (3) and the steam line (39 - 51) connecting the HRSG (3) to the steam turbine system (4), the steam bypassing the steam turbine system (4) via an operating bypass line (52 - 54) without using temporary piping and being discharged to the condenser (6), performing the verification steam blow procedure, and Monitoring and verifying the cleanliness of the selected steam blown steam line (39 - 54). A method comprising the above.

2. The method according to claim 1, wherein a steam blow operation is performed while the gas turbine engine (2) is operating at base load, and the operating bypass line (52 - 54) including the steam transport part of the HRSG (3), the steam line (39 - 51), and the bypass valves (55 - 57) to be steam blown is designed with a cleaning force ratio CFR of at least 1.

1.

3. The HRSG (3) has a plurality of pressure stages including a high pressure HP stage (21), an intermediate pressure IP stage (22), and a low pressure LP stage (23), and a reheater (24). The steam turbine system (4) includes an HP steam turbine (17), an IP steam turbine (18), and an LP steam turbine (19). The steam line (39 - 51) includes an HP steam line (47) for supplying HP steam from the HP stage (21) of the HRSG (3) to the HP steam turbine (17), an IP steam line (43) connecting the IP stage (22) of the HRSG (3) to the reheater (24), a high-temperature reheated HRH line (49) for supplying IP steam from the reheater (24) to the IP steam turbine (18), a low-temperature reheated CRH line (51) for receiving used HP steam from the HP steam turbine (17) and supplying the used HP steam to the reheater (24), an operating HP bypass line (52) arranged between the HP steam line (47) and the CRH line (51), an operating HRH bypass line (53) arranged between the HRH line (49) and the condenser (6), and an operating LP bypass line (54) arranged between the LP steam line (41) and the condenser (6). The method according to claim 1, wherein the design of the steam transport components of the HRSG (3), the steam lines (39 - 51), and the operating bypass lines (52 - 54) including the bypass valves (55 - 57) includes at least determining the sizes of at least the HP steam line, IP steam line, HRH line, CRH line, and LP steam lines (47, 43, 49, 51, 41), and the HP bypass line, HRH bypass line, and LP bypass lines (52, 53, 54), and determining the arrangement of these lines such that the cleaning force ratio CFR is at least 1.

1.

4. The method according to claim 3, further comprising providing an adjustable sacrificial trim designed to increase the performance of the flow coefficient CV of the bypass valves (55, 56, 57) for at least some of the bypass valves among the HP bypass valve, HRH bypass valve, and LP bypass valve (55, 56, 57) of the operating HP bypass line, HRH bypass line, and LP bypass line (52, 53, 54) such that a cleaning force ratio of at least 1.2 is supported in a single HRSG plant configuration and a cleaning force ratio CFR of at least 1.03 is supported in a multi-HRSG plant configuration.

5. Position the disconnect junctions of the HP bypass line, HRH bypass line, and LP bypass line (52, 53, 54) for operation as close as possible to the steam turbine system, at a location near the control and shut-off valve assemblies (63, 64, 65) of the HP steam turbine, IP steam turbine, and LP steam turbine (17, 18, 19), and at a position immediately upstream of the assemblies, and Install the check valve (66) of the CRH line (51) and the downstream connection of the HP bypass line (52) to the CRH line (51) as close as possible to the HP steam turbine (4). The method according to claim 3 or 4, further comprising the above steps.

6. The method according to any one of claims 3 to 5, further comprising installing target inserts (67, 68), preferably in the form of highly polished steel plates, in the HRH line (49) and the LP steam line (41), wherein the target inserts (67, 68) are configured and arranged such that online target inspection and monitoring of the cleanliness of the steam blown steam lines (39 - 57) can be performed under the operating conditions of the temperature and pressure of the steam during the verification blow procedure.

7. Install steam flow meters in the steam transport components of the HRSG (3), the steam lines (39 - 51), and the relevant parts of the operating bypass lines (52 - 54), and Calculate the CFR of the relevant parts based on the steam flow measurement values of the steam flow meters during the verification blow procedure. The method according to any one of claims 2 to 6, further comprising the above steps.

8. Provide inspection ports / cleaning ports in the portions (69 - 72) of the steam lines (47, 41, 49, 51) where steam blowing is not performed, and After the verification blow procedure is completed, inspect and clean the portions (69 - 72) where steam blowing is not performed. The method according to any one of claims 1 to 8, further comprising the above steps.

9. At least some of the plurality of branch connection parts of the HP bypass line, the HRH bypass line, and the LP bypass lines (52, 53, 54) further include providing a T-connection part that is straight with respect to each bypass line but not straight with respect to each steam turbine part (17, 18, 19) in order to reduce the accumulation of debris in the dead leg upstream of each steam turbine part (17, 18, 19). The method according to any one of claims 3 to 8.

10. The combined cycle power plant (1') has a multi-unit configuration including a single steam turbine system (4), a first unit (73) including a first HRSG (3a) and a first gas turbine engine (2a), and a second unit (74) including a second HRSG (3b) and a second gas turbine engine (2b). The method includes performing a verification blow procedure independently between the first and second units (73, 74). The method according to any one of claims 1 to 9.

11. Including performing the verification blow procedures of the first and second units (73, 74) sequentially with respect to each other. Preferably, performing the verification blow procedure of one of the first and second units (73, 74), and simultaneously, in the other unit (74, 73), including inspecting and cleaning the dead leg after the verification blow procedure. The method according to claim 10.

12. The combined cycle power plant (1') includes a multi-unit configuration including a single steam turbine system (4), a first unit (73) including a first HRSG (3a) and a first gas turbine engine (2a), and a second unit (74) including a second HRSG (3b) and a second gas turbine engine (2b). The method includes flowing verification steam using at least one bypass line (52 to 54) and bypass valves (55 to 57) in the other unit (74, 73) while performing the verification blow procedure in one of the first and second units (73, 74). The method according to any one of claims 1 to 9.

13. The combined cycle power plant (1') includes a first unit (73) including a single steam turbine system (4), a first HRSG (3a) and a first gas turbine engine (2a), and a second unit (74) including a second HRSG (3b) and a second gas turbine engine (2b), and includes a multi-unit configuration. A temporary jumper (78) is installed from the HP steam turbine valve (63) of the HP steam turbine (17) to the check valve (79) of the common low-temperature reheat CRH line (81), and the HRH bypass valves (56a, 56b) are sized so that a CFR of 1.1 is obtained in the HP and HRH steam systems. The method according to any one of claims 3 to 9.

14. A combined cycle power plant (1, 1'), A gas turbine engine (2) that generates electricity, A heat recovery steam generator HRSG (3) fluidly connected to the gas turbine engine (2), which receives high-energy exhaust gas generated from the power generation of the gas turbine engine (2) and is configured to generate steam from the high-energy exhaust gas. Heat recovery steam generator HRSG (3), A steam turbine system (4) fluidly connected to the HRSG (3) through a steam line (39-51), which receives the steam generated by the HRSG (3) and is configured to generate additional power from the steam. Steam turbine system (4), A condenser (6) coupled to the steam turbine system (4) to condense the used steam output from the steam turbine system (4), and coupled to a condensate system (7) to return the condensate from the condenser (6) to the HRSG (3). Condenser (6), An operating bypass line (52-54) fluidly connected between the steam line (39-51) and the condenser (6) and arranged to bypass the steam turbine system (4), A control system (9) for controlling the normal operation of the gas turbine engine (2), the HRSG (3), the steam turbine system (4), and the condenser (6) to generate power under various operating conditions. The control system (9) includes: Starting the gas turbine engine (2) and commissioning the gas turbine engine (2), While the gas turbine engine (2) is being test-run, perform a verification steam blow procedure including a steam blow operation, generating steam within the HRSG (3), and flowing the steam, under conditions of high flow rate, temperature, and cleaning power ratio, through a part of a closed fluid circuit to clean the steam transport components of the HRSG (3) and the steam line (39 - 51) connecting the HRSG (3) to the steam turbine system (4), wherein the steam bypasses the steam turbine system (4) via an operating bypass line (52 - 54) without using temporary piping and is discharged to the condenser (6), and perform the verification steam blow procedure, and monitor and verify the cleanliness of the steam line (39 - 54) through which the selected steam is blown The control system (9) is further configured to perform pre-operation cleaning of the water / steam system of the combined cycle power plant (1, 1'). A combined cycle power plant (1, 1') including the above.

15. The combined cycle power plant (1, 1') is configured as described in any one of claims 1 to 14, and the control system (9) is calibrated to perform the verification steam blow procedure described in any one of claims 1 to 14. The combined cycle power plant (1, 1') according to claim 14.

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