CN114320493B - Undisturbed switching method between 9H-cascade combined circulating unit booster units - Google Patents
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- 238000000034 method Methods 0.000 title claims abstract description 32
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 154
- 239000000872 buffer Substances 0.000 claims abstract description 117
- 239000003345 natural gas Substances 0.000 claims abstract description 77
- 239000007789 gas Substances 0.000 claims abstract description 49
- 230000006835 compression Effects 0.000 claims abstract description 30
- 238000007906 compression Methods 0.000 claims abstract description 30
- 238000002485 combustion reaction Methods 0.000 claims abstract description 28
- 239000000446 fuel Substances 0.000 claims abstract description 26
- 238000005457 optimization Methods 0.000 claims abstract description 7
- 238000002955 isolation Methods 0.000 claims description 15
- 230000008569 process Effects 0.000 claims description 11
- 230000006837 decompression Effects 0.000 claims description 4
- 238000011946 reduction process Methods 0.000 claims description 3
- 230000008859 change Effects 0.000 description 8
- 230000003139 buffering effect Effects 0.000 description 4
- 238000013461 design Methods 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000003921 oil Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000005070 sampling Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000007853 buffer solution Substances 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000498 cooling water Substances 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 230000011664 signaling Effects 0.000 description 1
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- 238000010977 unit operation Methods 0.000 description 1
- 238000009423 ventilation Methods 0.000 description 1
- 239000002918 waste heat Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
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Abstract
The invention discloses a non-interference switching method between 9H-cascade circulating unit booster units, which comprises the following steps: firstly, the pressure requirement of a gas engine inlet on natural gas and the technical parameters of a supercharger are required to be clarified; the minimum allowable pressure of the outlet of the booster is reversely pushed under the pressure condition of the lowest value or lower than the natural pressure range of the inlet of the fuel module of the combustion engine, the minimum buffer volume under the corresponding condition is calculated, and then the calculated minimum buffer volume is optimally reduced; setting a realization scheme of the buffer volume according to the buffer volume obtained after optimization; and finally, considering potential influencing factors of undisturbed switching of the supercharger and optimizing or adjusting, wherein the specific implementation scheme comprises a pipe capacity buffer scheme and a compression buffer tank scheme, the pipe capacity buffer scheme is realized by properly increasing the distance between the supercharger and a combustion engine room and properly increasing the pipe diameter to meet the requirement of minimum buffer volume, and the compression buffer tank scheme is realized by adding a compression buffer tank with a certain volume.
Description
Technical Field
The invention relates to the technical field of combined cycle power plant construction, in particular to a non-interference switching method between 9H-cascade combined cycle units and booster units.
Background
The 9H-level gas-steam combined cycle unit is the gas turbine unit with the highest capacity and highest efficiency worldwide at present. The design scale of the Bakistan certain combined cycle power station project (hereinafter referred to as the Bakistan project) is 1 set of 9H-level two-to-one gas-steam combined cycle unit, which comprises 2 sets of GE 9HA.01 gas turbine generator sets, 2 sets of three-pressure, reheat and natural circulation zone SCR waste heat boilers and 1 set of three-pressure, reheat and pure condensing steam turbine generator sets, and natural gas and light diesel dual fuel are used for combustion. The output of the gas turbine is 406.732MW, the output of the steam turbine is 418.391MW, the total output of the combined cycle is about 1.9MW, and the net efficiency of the combined cycle whole plant reaches 63.04%. The total contractual (EPC) contract of the buckstan project puts very strict demands on the performance and reliability of the main and auxiliary machines, for example, the provision of a buffer volume is required, so that the gas engine can be switched undisturbed between the natural gas superchargers under any load conditions, and the load of the gas engine is not reduced.
The power industry standard of China, namely, the design rule of a gas-steam combined cycle power plant (DL/T5174-2003) is as follows: when the supercharger needs to be arranged, one supercharger is preferably arranged for each set of gas turbines, and most of domestic power plants are not provided with the supercharger, so that the regulations are followed. The method is based on the consideration that most domestic combined cycle power plants are peak shaving units, and the reliability of a common booster is high (the availability of a common centrifugal booster in the power plant can reach more than 99.35%, the forced outage time is 29.7 hours/year, and the average time between two faults is more than 5.85 years). The foreign gas turbine power stations are required to carry basic load, and the reliability requirement of the unit is high, so that the booster is usually configured according to 2×100% of the whole plant capacity or 3×50% of the whole plant capacity, namely, the natural gas system is provided with a standby booster, and therefore, the higher requirement is put on the switching working condition of the booster. The working booster is stopped, the standby booster needs a certain time until the working booster is fully loaded, and the 'undisturbed switching' means that the combustion engine is ensured to maintain the full-load stable operation in the process of switching the working booster to the standby booster, which is still a problem which is still not considered in China. However, the requirements for realizing undisturbed switching among superchargers are met in a plurality of foreign combined cycle power station projects, and therefore, an implementation scheme for realizing undisturbed switching is needed.
Disclosure of Invention
The invention aims at solving the technical problems of the prior art, and provides the undisturbed switching method between the 9H-cascade combined cycle units, which can greatly save engineering investment, improve system reliability and effectively solve the undisturbed switching problem of the booster units.
The invention aims to accomplish the following technical scheme, and discloses a non-interference switching method between 9H-cascade circulating unit booster units, which comprises the following steps:
1) The method comprises the steps of determining the pressure requirement of a gas engine inlet on natural gas and the technical parameters of a supercharger; the natural gas pressure range of the inlet of the 9H-level gas turbine fuel module is 3.64 MPa.a-4.05 MPa.a, and the supercharger comprises a working supercharger and a standby supercharger;
2) Calculating a minimum buffer volume; the natural gas operating pressure in the pipeline is continuously reduced until the minimum pressure allowed by the natural gas at the inlet of the combustion engine is reduced in the process of stopping the working booster and starting the standby booster, and the standby booster is started to reach full load and put into use at the moment; under a certain gas storage volume of the pipeline, the pressure reduction process can enable the pipeline to release natural gas, and enable the gas turbine to maintain full-load operation in the switching time, and the minimum gas storage volume is the minimum buffer volume;
the minimum buffer volume calculation formula is as follows:
wherein: v (V) min For minimum buffer volume, m 3 The method comprises the steps of carrying out a first treatment on the surface of the Q is natural gas mass flow: kg/s; t is the time required for switching the supercharger, s; ρ 1 To natural gas density at normal operating pressure, kg/m 3 ；ρ 0 To allow natural gas density at minimum pressure kg/m 3 ；
3) At or below the lowest value of the range of natural gas pressures at the inlet of the fuel module of the combustion engine, back-pushing the lowest allowable pressure at the outlet of the supercharger and calculating the minimum buffer volume under the corresponding conditions;
4) Further optimizing and reducing the calculated minimum buffer volume;
5) Setting a realization scheme of the buffer volume according to the buffer volume obtained after optimization;
6) The potential influencing factors of the undisturbed switching of the supercharger are considered and optimized or adjusted.
Further, in step 5), the implementation scheme of the buffer volume includes a tube-volume buffer scheme and a compression buffer tank scheme, wherein the Guan Rong buffer scheme is as follows: on the premise of reasonable total plane arrangement, the distance between the supercharger and the combustion engine room is properly increased, and the pipe diameter is properly increased, so that the volume of a pipeline between the supercharger and the fuel module of the combustion engine meets the optimized minimum buffer volume requirement; the compression buffer tank scheme meets the optimized minimum buffer volume requirement by additionally installing a compression buffer tank device.
Further, the compression buffer tank scheme comprises the following contents:
a) When the unit normally operates, the front and rear isolation valves of the compressor are opened, the compressor works to compress and boost natural gas from the natural gas main pipe to a set pressure, the isolation valves are closed, and the compressor stops operating;
b) When the unit booster is required to be switched, the isolation valve behind the compression buffer tank is opened, the natural gas is decompressed to the set pressure through the decompression valve, and the natural gas is continuously supplied to the gas turbine until the unit booster completes the switching process;
since the temperature of the natural gas will rise after passing through the compressor, the minimum buffer volume calculation formula is adjusted as follows:
wherein T is 1 K is the temperature of natural gas in the compression buffer tank; t (T) 0 Temperature of 273K at standard state; the minimum buffer volume, i.e. the compressed buffer tank volume, which meets the requirements, can be calculated by equation (2).
The beneficial technical effects of the invention are as follows: according to the method, the undisturbed switching problem among the booster sets is converted into the calculation and optimization of the minimum buffer volume, and the optimal calculation of the minimum buffer volume and the research on the start-stop mode of the booster are provided, so that the undisturbed switching among the 9H-cascade combined cycle booster sets can be realized through the buffer of the pipeline volume.
Drawings
FIG. 1 is a schematic system diagram of a natural gas pressurization unit for the Bakistan project;
fig. 2 is a schematic system diagram of a natural gas compression buffer tank.
Detailed Description
The present invention will be further described with reference to the drawings and examples below in order to more clearly understand the objects, technical solutions and advantages of the present invention to those skilled in the art.
The invention discloses a non-interference switching method between 9H-cascade combined cycle units and a booster unit, which comprises the following steps:
1) The method comprises the steps of determining the pressure requirement of a gas engine inlet on natural gas and the technical parameters of a supercharger; the natural gas pressure range of the inlet of the 9H-level gas turbine fuel module is 3.64 MPa.a-4.05 MPa.a, and the supercharger comprises a working supercharger and a standby supercharger;
2) Calculating a minimum buffer volume; the natural gas operating pressure in the pipeline is continuously reduced until the minimum pressure allowed by the natural gas at the inlet of the combustion engine is reduced in the process of stopping the working booster and starting the standby booster, and the standby booster is started to reach full load and put into use at the moment; under a certain gas storage volume of the pipeline, the pressure reduction process can enable the pipeline to release natural gas, and enable the gas turbine to maintain full-load operation in the switching time, and the minimum gas storage volume is the minimum buffer volume;
the minimum buffer volume calculation formula is as follows:
wherein: v (V) min For minimum buffer volume, m 3 The method comprises the steps of carrying out a first treatment on the surface of the Q is natural gas mass flow: kg/s; t is the time required for switching the supercharger, s; ρ 1 To natural gas density at normal operating pressure, kg/m 3 ；ρ 0 To allow natural gas density at minimum pressure kg/m 3 ；
3) At or below the lowest value of the range of natural gas pressures at the inlet of the fuel module of the combustion engine, back-pushing the lowest allowable pressure at the outlet of the supercharger and calculating the minimum buffer volume under the corresponding conditions;
4) Further optimizing and reducing the calculated minimum buffer volume;
5) Setting a realization scheme of the buffer volume according to the buffer volume obtained after optimization;
6) The potential influencing factors of the undisturbed switching of the supercharger are considered and optimized or adjusted.
In step 5), the implementation scheme of the buffer volume includes a tube-volume buffer scheme and a compression buffer tank scheme, wherein the Guan Rong buffer scheme is as follows: on the premise of reasonable total plane arrangement, the distance between the supercharger and the combustion engine room is properly increased, and the pipe diameter is properly increased, so that the volume of a pipeline between the supercharger and the fuel module of the combustion engine meets the optimized minimum buffer volume requirement; the compression buffer tank scheme meets the optimized minimum buffer volume requirement by additionally installing a compression buffer tank device. The compression buffer tank scheme comprises the following contents:
a) When the unit normally operates, the front and rear isolation valves of the compressor are opened, the compressor works to compress and boost natural gas from the natural gas main pipe to a set pressure, the isolation valves are closed, and the compressor stops operating;
b) When the unit booster is required to be switched, the isolation valve behind the compression buffer tank is opened, the natural gas is decompressed to the set pressure through the decompression valve, and the natural gas is continuously supplied to the gas turbine until the unit booster completes the switching process;
since the temperature of the natural gas will rise after passing through the compressor, the minimum buffer volume calculation formula is adjusted as follows:
wherein T is 1 K is the temperature of natural gas in the compression buffer tank; t (T) 0 Temperature of 273K at standard state; the minimum buffer volume, i.e. the compressed buffer tank volume, which meets the requirements, can be calculated by equation (2).
Examples:
take a buckstan certain combined cycle plant project as an example (hereinafter referred to as buckstan project). The principle system of the supercharging unit in the natural gas pressure regulating station of the Pakistan project is shown in fig. 1, and mainly comprises 3 sets of supercharger systems corresponding to 100% of the natural gas consumption of one combustion engine, wherein #1 and #3 supercharger sets are normally operated and respectively supplied to #1 combustion engine and #2 combustion engine, the #2 supercharger sets are standby superchargers, and the branches of the 3 sets of supercharger sets are connected in parallel. Each supercharger branch is provided with a front safety cut-off valve, a rear safety cut-off valve, a front manual isolation valve and a rear manual isolation valve. The safety shut-off valve is supplied by a supercharger supplier along with a supercharger body system and used for safely shutting off when the supercharger starts and stops, the front and rear manual isolating valves are used for on-line maintenance isolation when the working supercharger fails, and the safety valve is used for protecting the supercharger and a downstream pipeline system.
And a pneumatic switching valve is also arranged between the 3 booster branch outlets. And when the #1 and #3 booster units normally operate, the pneumatic switching valve is closed. When the failure of the #1 booster unit needs to be switched to the operation of the #2 booster unit, the front and rear safety cut-off valves of the #1 booster unit are automatically closed along with the closing of the booster, the standby #2 booster is started, when the parameters meet the requirements, the pneumatic switching valve on the side of the #1 booster is opened, and natural gas at the outlet of the #2 booster is merged into the outlet branch of the original #1 booster. The fault switching mode of the #3 booster unit is the same.
Firstly, determining the pressure requirement of a fuel engine inlet on natural gas and the technical parameters of a supercharger; gas turbine inlet natural gas pressure requirement: the range and fluctuation of the natural gas pressure at the inlet of the GE company 9HA.01 are required to be certain, and if the pressure is lower than the minimum value or the pressure fluctuation speed exceeds a certain range, the gas engine can jump, and the specific requirements are as follows: (1) gas turbine fuel module inlet natural gas pressure range: 3.64 MPa.a-4.05 MPa.a; (2) transient: the maximum feed gas pressure change rate at the gas turbine inlet is limited to 1% change rate per second or 5% step. A limit of 1% change rate per second is applicable from minimum operating pressure to maximum operating pressure. The 5% step change limit applies to a range of 95% from minimum to maximum operating pressure and no more than a 5% step change can occur in 5 seconds; (3) steady state: the pressure change amplitude at any operating point at the inlet of the gas turbine fuel module should not exceed + -1% of the point pressure, and the average pressure change rate should be less than 0.25%/sec.
Supercharger technical parameters: the centrifugal supercharger has the advantages of small structure size, large exhaust gas amount, no wearing parts such as air valves, long continuous operation period, stable air supply and the like, thereby being widely applied to high-capacity gas pipelines and large-scale gas turbine power plants. The bacheltein project supercharger selects a centrifugal supercharger with 3X 50% of total plant natural gas consumption, two working and one standby. The specific selection parameters are shown in the following table:
table 1 natural gas booster selection parameters
After determining the pressure requirement of the gas engine inlet on the natural gas and the technical parameters of the supercharger, the minimum buffer volume can be calculated according to the formula (1), wherein the calculation comprises the calculation under the lowest pressure of 3.64MPa.a of the fuel module inlet and the calculation under the lowest pressure of 2.8MPa.a of the fuel module inlet.
(1) Calculation of the fuel module inlet minimum pressure at 3.64 mpa.a: the minimum allowable pressure of the outlet of the reverse booster is 4.098MPa.a, and the resistance conditions of each section are shown in the following table:
TABLE 2 resistance conditions for each section of Natural gas System
The standby booster takes 60 seconds to start from warm standby to full load operation, depending on the warranty value of the typical booster manufacturer. The minimum buffer volume calculated under this condition is shown in the following table:
TABLE 3 minimum buffer volume calculation Table-1
It is clear that substantially no pipe capacity of about 3700m3 is provided within the plant to meet the minimum buffer capacity requirements.
(2) Calculation of the minimum fuel module inlet pressure at 2.8 mpa.a: the pen managed to optimize from the "minimum pressure allowed" point of view, since the lower the "minimum pressure allowed" is, the more natural gas can be released from the existing tube volume for the fuel of the combustion engine during the turbocharger switching. According to further cooperation with a main engine plant, the 'gas engine jump pressure set value' of the inlet of the natural gas fuel module is 2.8MPa.a, and is greatly lower than the minimum pressure of 3.64MPa.a required normally. The minimum allowable pressure is 3.258MPa.a (considering the resistance 0.458 MPa) from the engine trip pressure 2.8MPa.a back-pushing booster outlet, and the minimum buffer volume is calculated under this condition as shown in the following table:
table 4 minimum buffer volume calculation table-2
Therefore, the minimum buffer volume is calculated to be 212.5m under the scheme 3 。
Further optimized reduction of minimum buffer volume:
to further reduce the minimum buffer volume and reduce the difficulty of undisturbed switching of the supercharger, we have further studied the time required for switching the supercharger. Through deep matching with a buckstan project supercharger manufacturer, the auxiliary supercharger can be started from a warm standby state to full-load operation within 30 seconds. The minimum buffer volume was further reduced to 107m3 by calculation in the same manner as in the previous section, and it was recommended that the actual buffer volume be considered to be not less than 118m3 (10% of the desired amount was considered).
After the minimum buffer volume is further optimized and reduced, the implementation scheme of considering the buffer volume can be correspondingly:
(1) Scheme one: guan Rong buffer regimen;
the distance between the outlet of the supercharger and the combustion engine room is longer, and the distance generally passes through the factory pipe frame (or the factory direct burial section), the front-mounted module of the fuel of the combustion engine and the pipeline from the front-mounted module to the fuel module of the combustion engine, so that the distance between the supercharger and the combustion engine room can be properly increased and the pipe diameter can be properly increased on the premise of reasonable total plane arrangement in the feasibility research and preliminary design stage of the power station, and the pipeline volume (including the internal volume of equipment such as a filter) between the supercharger and the fuel module of the combustion engine meets the requirement of the minimum buffer volume 118m 3.
In addition to meeting the undisturbed switching between superchargers, a suitable increase of the volume of this portion of the pipe has the following advantages:
when the gas engine is in load shedding, the natural gas flow rate is reduced from 100% to 30% within 1 second, and the pressure in the pipeline after the supercharger is possibly increased due to the delay of the action time of the supercharger and a valve thereof, so that the gas engine can be jumped. Properly increasing the tube volume contributes to stability under this condition.
The control system of the gas turbine needs to receive an online real-time signal of the heat value instrument so as to timely track the change of the heat value of the natural gas and timely perform combustion adjustment. Since the heat meter takes a while from sampling, analyzing, signaling to the engine control system, it is required that the natural gas flow time from the heat meter sampling port to the engine be as closely matched as possible to the real time signal transmission time of the heat meter. And by increasing the pipeline volume, reducing the natural gas flow rate will help the two to match in time.
2) Scheme II: compression buffer tank scheme
To meet the minimum buffer volume requirement, this can also be achieved by adding a compressed buffer tank arrangement as shown in fig. 2. When the unit normally operates, the front and rear isolation valves of the compressor are opened, the compressor works to compress and boost natural gas from the natural gas main pipe to a set pressure, the isolation valves are closed, and the compressor stops operating. When the unit booster is required to be switched, the isolation valve behind the compression buffer tank is opened, the natural gas is decompressed to the set pressure through the decompression valve, and the natural gas is continuously supplied to the gas turbine until the unit booster completes the switching process. The capacity of the compressed buffer tank of about 45m3 is calculated according to the formula (2) and can meet the requirements, and the investment estimation of the device is shown in the following table:
TABLE 5 Natural gas compression buffer tank installation investment evaluation Table
But this solution has the following drawbacks:
(1) The equipment such as a natural gas compressor unit, a buffer tank, a regulating valve group and the like is added, the design pressure of the equipment needs to be increased to the highest working pressure after the compressor unit, and the investment of the equipment, pipelines and civil engineering foundations is increased to more than 160 ten thousand yuan;
(2) The compressor unit, the roundabout buffer tank and the like are required to be added with larger installation sites (about 350m < 2 >), the total planar arrangement of practical projects is often tension, and the sites are difficult to leave;
(3) The whole natural gas system is provided with a large supercharger and a small compressor for compressing the buffer tank, so that the complexity of the system is increased, and the control difficulty is increased;
(4) The workload of overhauling and maintaining is increased.
The recommended scheme is as follows:
because the first scheme adopts pipeline volume buffering to meet the requirement of minimum buffering volume, a compression buffer tank system is canceled, engineering investment is saved, system reliability is improved, and the undisturbed switching problem of the booster unit is effectively solved. Therefore, the use of scheme one "tube buffer scheme" is preferred when the general layout is conditional. When the minimum buffer volume is calculated to be too large, the pipe capacity buffer scheme which is only realized by the scheme one is difficult to realize, and the supercharging unit arrangement site is provided with a space for installing facilities such as a compression buffer tank, a matched compressor and the like, the scheme two compression buffer tank scheme can be considered to be adopted.
Other considerations for undisturbed switching of the supercharger:
(1) The starting step of the normal booster is that the auxiliary oil pump is started and started for about 1-2 minutes, purged for about 1 minute, started and lubricated for 1 minute, started for 0.5 minute, and the loading time is about 4-5 minutes after the oil temperature reaches the loading condition, and the total time is about 10 minutes, during the starting loading process, the fuel engine jumps due to the insufficient natural gas stored in the pipeline, so as to ensure that the standby booster is not disturbed to be switched to a full-load running state, the standby booster must be in a warm standby state rather than a cold state before being switched, and the booster can be quickly started in the warm standby state without performing the starting of the auxiliary system and a series of checking procedures like the cold state starting, so that the starting time is saved to the greatest extent:
the compressed air supply and the nitrogen supply required by the supercharger are good;
the dry gas seal of the supercharger, the housing ventilation fan and the shaft seal work well;
the supercharger lubricating oil system is normally operated;
the cooling water system of the supercharger normally operates;
(2) It is suggested that the "time required for starting the supercharger from warm standby to full load" be written as performance assurance data and important bid evaluation factors into the bid file during the supercharger bid stage to promote the supercharger suppliers to perform sufficient optimization work, reduce the time required for supercharger switching, and enable the power plant to more easily achieve a non-disturbing supercharger switching.
(3) The different gas suppliers will differ with respect to the "minimum allowable pressure" (in the case of a switched state of the supercharger) required before the gas fuel module, and should negotiate as much as possible with the gas suppliers to reduce this pressure as much as possible, for example by taking the alarm pressure or the trip pressure as the minimum allowable pressure in the case of a switched state of the supercharger, and the final duct volume is guaranteed to be larger than the minimum buffer volume calculated in this way, leaving a certain amount of desire.
(4) When the working supercharger needs to be switched to the standby supercharger, the working supercharger recommends to delay for proper time to be shut down again so as to ensure the reliable completion of undisturbed switching.
(5) Because the supercharger is one of the most important auxiliary machines of the gas turbine power station, the switching process is complex, the function requirement of ' undisturbed switching ' is higher, the realization difficulty of a supercharger supplier is still higher at present, in order to avoid the risk of unnecessary check fines, the EPC bidder and a homeowner are suggested to fully negotiate in the foreign project EPC contract negotiation stage, the requirement of ' the supercharger has the undisturbed switching under the premise of maintaining the full load of the gas turbine ' is reduced to be ' the supercharger has reliable switching function ', the gas turbine is ensured not to be started to jump (the gas turbine is allowed to run in a short time in the switching process of the supercharger) ', the calculation value of the minimum buffering capacity is greatly reduced, and the supercharger supplier is easier to meet.
Conclusion: according to the invention, through calculation and optimization of the minimum buffer volume, a scheme of pipe capacity buffer or compression buffer tank buffer is adopted, so that undisturbed switching between the working booster and the standby booster of the 9H-cascade combined cycle unit is realized, and the safety and reliability of unit operation are improved. The main conclusion is as follows: (1) When the time required for starting the supercharger from the warm standby state to the full load is 30 seconds, when the natural gas pipe volume between the supercharger and the fuel module of the combustion engine is about 118m3 or more, the undisturbed switching between the supercharger sets can be realized without affecting the load of the combustion engine. (2) By adopting the scheme of pipeline volume buffering, the compression buffer tank system can be canceled, the engineering investment can be saved, the system reliability can be improved, and the undisturbed switching problem of the booster unit can be effectively solved. Therefore, the use of a "tube buffer solution" is preferred when the overall layout is conditional.
The specific embodiments described herein are merely illustrative of the principles and functions of the present invention, and are not meant to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. It is therefore intended that all equivalent modifications and changes made by those skilled in the art without departing from the spirit and technical spirit of the present invention shall be covered by the appended claims.
Claims (3)
1. A method for undisturbed switching between 9H-cascade combined circulating unit booster units is characterized in that: the method comprises the following steps:
1) The method comprises the steps of determining the pressure requirement of a gas engine inlet on natural gas and the technical parameters of a supercharger; the natural gas pressure range of the inlet of the 9H-level gas turbine fuel module is 3.64 MPa.a-4.05 MPa.a, and the supercharger comprises a working supercharger and a standby supercharger;
2) Calculating a minimum buffer volume; the natural gas operating pressure in the pipeline is continuously reduced until the minimum pressure allowed by the natural gas at the inlet of the combustion engine is reduced in the process of stopping the working booster and starting the standby booster, and the standby booster is started to reach full load and put into use at the moment; under a certain gas storage volume of the pipeline, the pressure reduction process can enable the pipeline to release natural gas, and enable the gas turbine to maintain full-load operation in the switching time, and the minimum gas storage volume is the minimum buffer volume;
the minimum buffer volume calculation formula is as follows:
wherein: v (V) min M3, the minimum buffer volume; q is natural gas mass flow: kg/s; t is the time required for switching the supercharger, s; ρ 1 The density of the natural gas is kg/m3 under normal working pressure; ρ 0 Kg/m3 to allow natural gas density at minimum pressure;
3) At or below the lowest value of the range of natural gas pressures at the inlet of the fuel module of the combustion engine, back-pushing the lowest allowable pressure at the outlet of the supercharger and calculating the minimum buffer volume under the corresponding conditions;
4) Further optimizing and reducing the calculated minimum buffer volume;
5) Setting a realization scheme of the buffer volume according to the buffer volume obtained after optimization;
6) The potential influencing factors of the undisturbed switching of the supercharger are considered and optimized or adjusted.
2. The undisturbed switching method between the 9H-cascade combined cycle units and the booster units according to claim 1, wherein the method comprises the following steps: in step 5), the implementation scheme of the buffer volume includes a tube-volume buffer scheme and a compression buffer tank scheme, wherein the Guan Rong buffer scheme is as follows: on the premise of reasonable total plane arrangement, the distance between the supercharger and the combustion engine room is properly increased, and the pipe diameter is properly increased, so that the volume of a pipeline between the supercharger and the fuel module of the combustion engine meets the optimized minimum buffer volume requirement; the compression buffer tank scheme meets the optimized minimum buffer volume requirement by additionally installing a compression buffer tank device.
3. The undisturbed switching method between the 9H-cascade combined cycle units and the booster units according to claim 2, wherein the method comprises the following steps: the compression buffer tank scheme comprises the following contents:
a) When the unit normally operates, the front and rear isolation valves of the compressor are opened, the compressor works to compress and boost natural gas from the natural gas main pipe to a set pressure, the isolation valves are closed, and the compressor stops operating;
b) When the unit booster is required to be switched, the isolation valve behind the compression buffer tank is opened, the natural gas is decompressed to the set pressure through the decompression valve, and the natural gas is continuously supplied to the gas turbine until the unit booster completes the switching process;
since the temperature of the natural gas will rise after passing through the compressor, the minimum buffer volume calculation formula is adjusted as follows:
wherein T is 1 K is the temperature of natural gas in the compression buffer tank; t (T) 0 Temperature of 273K at standard state; the minimum buffer volume, i.e. the compressed buffer tank volume, which meets the requirements, can be calculated by equation (2).
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