Dual-fuel switching system and switching method for IGCC (integrated gasification combined cycle) unit low-heating-value gas turbine

Abstract

The invention relates to a fuel switching technology, and provides a dual-fuel switching system for a low-calorific-value gas turbine of an IGCC (integrated gasification combined cycle) unit, which comprises a fuel front-end system, a burner, a fuel channel for connecting the fuel front-end system and the burner, a synthesis gas front-end system, a synthesis gas channel for connecting the synthesis gas front-end system and the burner, and a control system. According to the dual-fuel switching system and switching method for the IGCC unit low-calorific-value gas turbine, success of dual-fuel switching is ensured within a reasonable load fluctuation range, and the safe operation range of the gas turbine is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel switching, and in particular to a dual-fuel switching system and a switching method for a low calorific value combustion engine of an IGCC unit. Background Art

[0002] The IGCC unit uses low calorific value syngas. During normal operation, the gas turbine uses low calorific value hydrogen-rich syngas produced by the gasifier. Since the combustion of syngas under low load conditions of the gas turbine is extremely unstable, the gas turbine needs to be ignited and started by diesel. When the load rises to the fuel switching range, it switches to syngas fuel operation. Similarly, when the gas turbine is shut down or there is a combustion abnormality, it is also necessary to switch from syngas operation to fuel operation, reduce the load and shut down, or ensure that the gas turbine is operating in a safe state. The general fuel switching control method is to linearly increase and decrease the two fuels until the starting fuel drops to zero. The switching time takes about 120s.

[0003] Conventional switching control methods are not applicable to fuel switching of gas turbines burning low calorific value synthesis gas. During the switching between high calorific value fuel and low calorific value fuel, it is necessary to quickly increase the low calorific value fuel while reducing the high calorific value fuel to make up for the reduced amount of fuel. Due to the different flow response characteristics of the two fuel regulating valves, the fuel switching speed cannot be too fast, otherwise it will cause an imbalance in the fuel proportion during the switching process, and an inappropriate fuel switching speed will also increase the time of the mixed combustion condition. The simultaneous combustion of two fuels with different calorific values ​​and different combustion states will cause an increase in the hum of the combustion chamber. If the mixed combustion time is too long, it will easily cause combustion instability, and in severe cases it will cause an increase in the hum of the combustion chamber and cause the gas turbine to trip. Summary of the invention

[0004] The object of the present invention is to provide a dual fuel switching system and switching method for a low calorific value gas engine of an IGCC unit, which ensures the success of dual fuel switching within a reasonable load fluctuation range and broadens the safe operation range of the gas engine.

[0005] The embodiment of the present invention is realized by the following technical scheme: the dual-fuel switching system for the low calorific value combustion engine of the IGCC unit of the present invention comprises a fuel pre-placement system, a burner, a fuel passage for connecting the fuel pre-placement system and the burner, a syngas pre-placement system, a syngas passage for connecting the syngas pre-placement system and the burner, and a control system; the fuel pre-placement system comprises an oil supply pressure control valve connected to the oil supply pipeline, a first oil filling valve and a second oil filling valve arranged in parallel downstream of the oil supply pressure valve, a first oil supply and oil return ball valve assembly arranged downstream of the first oil filling valve, and a second oil filling valve arranged downstream of the second oil filling valve. Oil supply and return ball valve assembly; the first oil supply and return ball valve assembly and the second oil supply and return ball valve assembly are connected to the burner through the fuel channel; the synthesis gas pre-system includes an incoming gas pipeline, a synthesis gas pipeline isolation valve, a synthesis gas locking nitrogen shut-off valve, a synthesis gas locking system, a synthesis gas purge system, a synthesis gas purge nitrogen control valve, and a synthesis gas fuel control valve arranged downstream of the synthesis gas pipeline isolation valve; the inlet end of the synthesis gas purge system is connected to a nitrogen buffer tank; the downstream of the synthesis gas fuel control valve and the downstream of the synthesis gas purge nitrogen control valve are both connected to the burner through a synthesis gas channel.

[0006] Further, the fuel channel includes a left oil supply channel and a right oil supply channel connected to the oil supply port of the burner, and a left oil return channel and a right oil return channel connected to the oil return port of the burner; the left oil supply channel is connected to the oil supply end of the first oil supply and oil return ball valve assembly, and the left oil return channel is connected to the oil return end of the first oil supply and oil return ball valve assembly; the right oil supply channel is connected to the oil supply end of the second oil supply and oil return ball valve assembly, and the right oil return channel is connected to the oil return end of the second oil supply and oil return ball valve assembly.

[0007] Furthermore, the fuel front system also includes an emergency fuel supply shut-off valve disposed between the fuel supply pipeline and the fuel supply pressure control valve.

[0008] Furthermore, the fuel pre-system also includes an oil return control valve and an oil return pipeline connected to the downstream of the oil return control valve; the downstream of the first oil filling valve, the oil return end of the first oil supply and return ball valve assembly, the downstream of the second oil filling valve, and the oil return end of the second oil supply and return ball valve assembly are all connected to the oil return control valve.

[0009] Furthermore, the fuel front system also includes an oil return emergency shut-off valve arranged upstream of the oil return control valve.

[0010] Furthermore, the synthesis gas front system also includes a synthesis gas emergency shut-off valve arranged between the incoming gas pipeline and the synthesis gas pipeline isolation valve, a first relief valve arranged between the synthesis gas emergency shut-off valve and the synthesis gas pipeline isolation valve, a first flare arranged downstream of the first relief valve, a second relief valve arranged between the synthesis gas pipeline isolation valve and the synthesis gas locking nitrogen shut-off valve, and a second flare arranged downstream of the second relief valve.

[0011] Furthermore, the synthesis gas channel includes a left synthesis gas channel and a right synthesis gas channel which are arranged in parallel.

[0012] The present invention also provides a switching method based on the dual fuel switching system for the low calorific value engine of the IGCC unit, comprising the following steps:

[0013] (1) From the high-disk purge, ignition, speed increase, synchronous grid connection to the load reaching the fuel switching interval, the fuel used by the gas engine is fuel oil, which is controlled by the fuel supply pressure control valve, the first fuel supply and return ball valve assembly and the second fuel supply and return ball valve assembly, and then flows through the fuel oil channel into the burner for combustion;

[0014] (2) When the syngas channel is closed, the syngas locking system and the syngas purge system start to operate to avoid flashback and ensure complete isolation of the syngas fuel;

[0015] (3) After the load of the gas turbine reaches the fuel switching interval, the current load is kept unchanged, and the control system starts to switch from the fuel oil to the syngas fuel control. After the syngas channel is fully purged and replaced, the syngas purging system and the syngas locking system are exited, and the fuel oil return is gradually opened at a uniform speed of V1 to reduce the amount of fuel involved in combustion. At the same time, the syngas pipeline isolation valve is opened, and the syngas fuel control valve is gradually opened at a uniform speed of V1 to increase the low calorific value syngas flow rate from the minimum stable combustion flow rate, wherein the sum of the fuel oil amount ratio and the syngas amount ratio is always 100%;

[0016] (4) When the fuel flow rate drops to 30%, the switching speed is increased to V2 until the fuel flow rate drops to the minimum stable combustion flow rate, the fuel supply and fuel return are shut down, the fuel is cut off, and at the same time, under the action of the load controller, the syngas flow rate is quickly controlled by adjusting the syngas fuel control valve, the gas turbine completes the fuel switching, and then operates under the syngas condition until the basic load is reached.

[0017] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects: the dual-fuel switching system and switching method for the low calorific value gas engine of the IGCC unit of the present invention, by setting a fuel pre-system in the fuel part and a syngas pre-system in the syngas part, and controlling the fuel intake and return oil amount, and the syngas intake amount respectively through the pre-system and the syngas pre-system, and a switching control method between fuel oil and syngas fuel is proposed for the IGCC gas engine burning low calorific value syngas, which ensures the success of dual-fuel switching while ensuring a reasonable load fluctuation range, and broadens the safe operation range of the gas engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A schematic structural diagram of a dual-fuel switching system for a low calorific value combustion engine of an IGCC unit provided in an embodiment of the present invention.

[0020] Icons: 11-Oil supply emergency shut-off valve, 12-Oil supply pressure control valve, 13-First oil filling valve, 14-Second oil filling valve, 15-First oil supply and return ball valve assembly, 16-Second oil supply and return ball valve assembly, 17-Oil return emergency shut-off valve, 18-Oil return control valve, 19-Oil supply pipeline, 110-Oil return pipeline, 21-Left oil supply channel, 22-Left oil return channel, 23-Right oil supply channel, 24-Right oil return channel, 30-Burner, 41-Left Side synthesis gas channel, 42-right side synthesis gas channel, 51-incoming gas pipeline, 52-synthesis gas emergency shut-off valve, 53-synthesis gas pipeline isolation valve, 54-first relief valve, 55-first flare, 56-second relief valve, 57-second flare, 58-synthesis gas fuel control valve, 59-synthesis gas locking nitrogen shut-off valve, 510-synthesis gas locking system, 511-synthesis gas purge system, 512-nitrogen buffer tank, 513-synthesis gas purge nitrogen control valve. DETAILED DESCRIPTION

[0021] Example 1

[0022] The following is further described in conjunction with specific embodiments. Figure 1As shown, the dual-fuel switching system for a low calorific value combustion engine of an IGCC unit of the present invention comprises a fuel pre-placement system, a burner 30, a fuel passage for connecting the fuel pre-placement system and the burner 30, a syngas pre-placement system, a syngas passage for connecting the syngas pre-placement system and the burner 30, and a control system; the fuel pre-placement system comprises an oil supply pressure control valve 12 connected to an oil supply pipeline 19, a first oil filling valve 13 and a second oil filling valve 14 arranged in parallel downstream of the oil supply pressure valve, a first oil supply and oil return ball valve assembly 15 arranged downstream of the first oil filling valve 13, and a second oil supply and oil return ball valve assembly 16 arranged downstream of the second oil filling valve 14; the first oil supply The oil return ball valve assembly 15 and the second oil supply and oil return ball valve assembly 16 are connected to the burner 30 through the fuel channel; the synthesis gas pre-system includes an incoming gas pipeline 51, a synthesis gas pipeline isolation valve 53, a synthesis gas locking nitrogen shut-off valve 59, a synthesis gas locking system 510, a synthesis gas purge system 511, a synthesis gas purge nitrogen control valve 513, and a synthesis gas fuel control valve 58 arranged downstream of the synthesis gas pipeline isolation valve 53; the inlet end of the synthesis gas purge system 511 is connected to a nitrogen buffer tank 512; the downstream of the synthesis gas fuel control valve 58 and the downstream of the synthesis gas purge nitrogen control valve 513 are both connected to the burner 30 through the synthesis gas channel. Specifically, a fuel pre-system is arranged in the fuel part and a syngas pre-system is arranged in the syngas part. The fuel intake and return oil amount, and the syngas intake amount are controlled respectively by the fuel pre-system and the syngas pre-system. A switching control method between fuel oil and syngas is proposed for IGCC gas engines burning low calorific value syngas. While ensuring a reasonable load fluctuation range, the success of dual-fuel switching is ensured and the safe operation range of the gas engine is widened.

[0023] The fuel passage in this embodiment includes a left fuel supply passage 21 and a right fuel supply passage 23 connected to the fuel supply port of the burner 30, and a left fuel return passage 22 and a right fuel return passage 24 connected to the fuel return port of the burner 30; the left fuel supply passage 21 is connected to the fuel supply end of the first fuel supply and fuel return ball valve assembly 15, and the left fuel return passage 22 is connected to the fuel return end of the first fuel supply and fuel return ball valve assembly 15; the right fuel supply passage 23 is connected to the fuel supply end of the second fuel supply and fuel return ball valve assembly 16, and the right fuel return passage 24 is connected to the fuel return end of the second fuel supply and fuel return ball valve assembly 16. Specifically, each passage is relatively independent and is controlled by the first fuel supply and fuel return ball valve assembly 15 and the second fuel supply and fuel return ball valve assembly 16.

[0024] The fuel pre-system in this embodiment also includes an oil supply emergency shut-off valve disposed between the incoming oil pipeline 19 and the oil supply pressure control valve 12. The fuel pre-system also includes an oil return control valve 18, and an oil return pipeline 110 connected to the downstream of the oil return control valve 18; the downstream of the first oil filling valve 13, the oil return end of the first oil supply return ball valve assembly 15, the downstream of the second oil filling valve 14, and the oil return end of the second oil supply return ball valve assembly 16 are all connected to the oil return control valve 18. The fuel pre-system also includes an oil return emergency shut-off valve 17 disposed upstream of the oil return control valve 18. Specifically, the oil return pipeline 110, the oil return control valve 18, and the oil return emergency shut-off valve 17 are mainly used to control the oil return state of the fuel.

[0025] The synthesis gas pre-system in this embodiment also includes a synthesis gas emergency shut-off valve 52 provided between the incoming gas pipeline 51 and the synthesis gas pipeline isolation valve 53, a first relief valve 54 provided between the synthesis gas emergency shut-off valve 52 and the synthesis gas pipeline isolation valve 53, a first flare 55 provided downstream of the first relief valve 54, a second relief valve 56 provided between the synthesis gas pipeline isolation valve 53 and the synthesis gas locking nitrogen shut-off valve 59, and a second flare 57 provided downstream of the second relief valve 56. The synthesis gas channel includes a left synthesis gas channel 41 and a right synthesis gas channel 42 provided in parallel. Specifically, the fuel oil is supplied through the fuel supply pipeline 19 after being stabilized, flows through the fuel supply emergency shut-off valve, the fuel supply pressure control valve 12, the first fuel supply return ball valve assembly 15, and the second fuel supply return ball valve assembly 16 into the fuel oil fuel channel, and finally enters the burner 30; the synthesis gas is supplied through the synthesis gas pipeline after being stabilized, flows through the synthesis gas emergency shut-off valve 52, the synthesis gas pipeline isolation valve 53 and the synthesis gas fuel control valve 58 into the synthesis gas fuel channel and enters the burner 30; a synthesis gas shut-off valve is provided between the synthesis gas pipeline isolation valve 53 and the synthesis gas fuel control valve 58. The lock system 510 can lock and isolate the synthesis gas pipeline when the synthesis gas fuel channel is disabled; a synthesis gas purge system 511 is provided downstream of the synthesis gas fuel control valve 58, which can fully purge and replace the synthesis gas fuel channel before the synthesis gas fuel is put into operation and after it is withdrawn, and at the same time maintain the synthesis gas fuel channel pressure higher than the compressed air pressure in the burner 30, which effectively prevents backfire, ensures that the fuel enters the burner 30 smoothly when the synthesis gas operating condition is running, and ensures the safe operation of the gas turbine when the synthesis gas fuel is withdrawn. It should be noted that the control system includes: gas turbine combustion adjustment logic, gas turbine sequence control logic, gas turbine load control logic and valve switching control logic, and the control system is used to send control signals to each valve and receive valve position feedback information of each valve to complete the purpose of fuel switching.

[0026] Example 2

[0027] This embodiment provides a switching method for a dual fuel switching system for a low calorific value combustion engine of an IGCC unit based on Embodiment 1, comprising the following steps:

[0028] (1) From the high-disk purge, ignition, speed increase, synchronous grid connection to the load reaching the fuel switching interval, the fuel used by the gas engine is fuel oil, which is controlled by the fuel supply emergency shut-off valve, the fuel supply pressure control valve 12, the first fuel supply return ball valve assembly 15 and the second fuel supply return ball valve assembly 16, and then flows through the fuel oil channel into the burner 30 for combustion;

[0029] (2) When the syngas channel is closed, the syngas locking system 510 and the syngas purge system 511 start to operate to avoid flashback and ensure complete isolation of the syngas fuel;

[0030] (3) After the engine load reaches the fuel switching interval, the current load is kept unchanged, and the control system starts to execute the switch from oil fuel to synthesis gas fuel control, starts the synthesis gas input sequence control program, and simultaneously links the oil fuel exit sequence control program. After the synthesis gas channel is fully purged and replaced (generally set for 20 seconds), exit the synthesis gas purge system 511 and the synthesis gas locking system 510, gradually open the oil return at a uniform speed of V1 to reduce the amount of fuel involved in combustion, and at the same time open the synthesis gas pipeline isolation valve 53, and gradually open the synthesis gas fuel control valve 58 at a uniform speed of V1 to increase the low calorific value synthesis gas flow rate from the minimum stable combustion flow rate, wherein the sum of the oil fuel amount ratio and the synthesis gas fuel amount ratio is always 100%;

[0031] (4) When the fuel flow rate drops to 30%, the switching speed is increased to V2 until the fuel flow rate drops to the minimum stable combustion flow rate, the fuel supply and fuel return are closed, and the fuel fuel is cut off. At the same time, under the action of the load controller, the synthesis gas fuel control valve 58 is adjusted to quickly control the synthesis gas flow rate. The gas turbine completes the fuel switching and then operates under the synthesis gas condition until the basic load is reached.

[0032] In addition, the switching of syngas fuel back to fuel oil is exactly the opposite of the switching of fuel oil to syngas fuel. In order to shorten the switching time, V3 uniform speed switching is adopted in the early stage of switching between syngas and fuel oil. When the proportion of fuel oil exceeds 30%, the switching speed is reduced to V4. When the syngas fuel is reduced to the minimum stable combustion proportion, the syngas fuel is quickly cut off, and the fuel oil amount is quickly opened to a certain degree to compensate for the loss of heat of the syngas fuel.

[0033] Example 3

[0034] This embodiment provides a procedure for when a combustion abnormality occurs in a gas engine under a syngas working condition or the gas engine needs to be shut down:

[0035] (1) If the engine load is not within the fuel switching range, the load should be adjusted to within the fuel switching range before switching from syngas fuel to fuel oil.

[0036] (2) Control the opening of the fuel supply emergency shut-off valve, the fuel supply pressure control valve 12, the first filling valve 13 and the second filling valve 14 for 2 seconds, fill the fuel pre-system with fuel, fill the fuel to the front of the fuel channel, start the fuel injection sequence control program of the engine control, and simultaneously link the synthesis gas to exit the sequence control program, inject the synthesis gas purge system 511, open the fuel supply and return emergency shut-off valve 17, adjust the fuel supply pressure control valve 12 and the return oil control valve 18 to increase the amount of fuel participating in the combustion at a uniform speed of V3, and adjust the opening of the synthesis gas fuel control valve 58 The synthesis gas flow rate is reduced at a corresponding speed, wherein the sum of the fuel oil fuel ratio and the synthesis gas fuel ratio is always 100%. When the synthesis gas flow rate drops to 70%, the switching speed is reduced to V4 until the synthesis gas flow rate drops below the minimum stable combustion flow rate. The synthesis gas emergency shut-off valve 52 is quickly closed to cut off the synthesis gas flow rate. At the same time, the synthesis gas locking system 510 is put into operation. Under the action of the load controller, the fuel flow rate is quickly controlled by adjusting the fuel return control valve 18CV-2, and the gas turbine completes the fuel switching to ensure safe and stable operation of the gas turbine.

[0037] (3) If the engine needs to be shut down at this time, load reduction control is performed until it runs at full speed and no-load under fuel conditions, and finally the engine is shut down under the shutdown sequence control.

[0038] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dual fuel switching system for a low calorific value combustion engine of an IGCC unit, characterized in that: It comprises a fuel pre-position system, a burner (30), a fuel passage for connecting the fuel pre-position system and the burner (30), a synthesis gas pre-position system, a synthesis gas passage for connecting the synthesis gas pre-position system and the burner (30), and a control system; The fuel pre-system comprises a fuel supply pressure control valve (12) connected to the fuel supply pipeline (19), a first fuel filling valve (13) and a second fuel filling valve (14) arranged in parallel downstream of the fuel supply pressure valve, a first fuel supply and oil return ball valve assembly (15) arranged downstream of the first fuel filling valve (13), and a second fuel supply and oil return ball valve assembly (16) arranged downstream of the second fuel filling valve (14); the first fuel supply and oil return ball valve assembly (15) and the second fuel supply and oil return ball valve assembly (16) are connected to the burner (30) through the fuel passage; The synthesis gas pre-system comprises an incoming gas pipeline (51), a synthesis gas pipeline isolation valve (53), a synthesis gas locking nitrogen shut-off valve (59), a synthesis gas locking system (510), a synthesis gas purge system (511), a synthesis gas purge nitrogen control valve (513), and a synthesis gas fuel control valve (58) arranged downstream of the synthesis gas pipeline isolation valve (53); the inlet end of the synthesis gas purge system (511) is connected to a nitrogen buffer tank (512); The downstream of the synthesis gas fuel control valve (58) and the downstream of the synthesis gas purge nitrogen control valve (513) are both connected to the burner (30) through a synthesis gas channel.

2. The dual fuel switching system for a low calorific value engine of an IGCC unit according to claim 1, characterized in that: The fuel passage comprises a left fuel supply passage (21) and a right fuel supply passage (23) connected to the fuel supply port of the burner (30), and a left fuel return passage (22) and a right fuel return passage (24) connected to the fuel return port of the burner (30); The left oil supply channel (21) is connected to the oil supply end of the first oil supply and oil return ball valve assembly (15), and the left oil return channel (22) is connected to the oil return end of the first oil supply and oil return ball valve assembly (15); The right oil supply passage (23) is connected to the oil supply end of the second oil supply and oil return ball valve assembly (16), and the right oil return passage (24) is connected to the oil return end of the second oil supply and oil return ball valve assembly (16).

3. The dual fuel switching system for a low calorific value combustion engine of an IGCC unit according to claim 1, characterized in that: The fuel front system also includes an emergency fuel supply shutoff valve disposed between the fuel supply pipeline (19) and the fuel supply pressure control valve (12).

4. The dual fuel switching system for a low calorific value engine of an IGCC unit according to claim 1, characterized in that: The fuel front system further comprises an oil return control valve (18), and an oil return pipeline (110) connected downstream of the oil return control valve (18); The downstream of the first oil filling valve (13), the oil return end of the first oil supply and return ball valve assembly (15), the downstream of the second oil filling valve (14), and the oil return end of the second oil supply and return ball valve assembly (16) are all connected to the oil return control valve (18).

5. The dual fuel switching system for a low calorific value engine of an IGCC unit according to claim 4 is characterized in that: The fuel front system further comprises an oil return emergency shut-off valve (17) arranged upstream of the oil return control valve (18).

6. The dual fuel switching system for a low calorific value combustion engine of an IGCC unit according to claim 1, characterized in that: The synthesis gas pre-system also includes a synthesis gas emergency shut-off valve (52) arranged between the incoming gas pipeline (51) and the synthesis gas pipeline isolation valve (53), a first relief valve (54) arranged between the synthesis gas emergency shut-off valve (52) and the synthesis gas pipeline isolation valve (53), a first flare (55) arranged downstream of the first relief valve (54), a second relief valve (56) arranged between the synthesis gas pipeline isolation valve (53) and the synthesis gas locking nitrogen shut-off valve (59), and a second flare (57) arranged downstream of the second relief valve (56).

7. The dual fuel switching system for a low calorific value combustion engine of an IGCC unit according to claim 1, characterized in that: The synthesis gas channel comprises a left synthesis gas channel (41) and a right synthesis gas channel (42) which are arranged in parallel.

8. A switching method for a dual fuel switching system for a low calorific value engine of an IGCC unit based on any one of claims 1 to 7, characterized in that: The following steps are included: (1) From the high-disk purging, ignition, speed increase, synchronous grid connection to the load reaching the fuel switching interval of the gas engine, the fuel used by the gas engine is fuel oil, which is controlled by the fuel supply pressure control valve (12), the first fuel supply and return ball valve assembly (15) and the second fuel supply and return ball valve assembly (16), and then flows through the fuel oil channel into the burner (30) for combustion; (2) When the syngas channel is closed, the syngas locking system (510) and the syngas purge system (511) start to operate to avoid flashback and ensure complete isolation of the syngas fuel; (3) After the load of the gas turbine reaches the fuel switching interval, the current load is kept unchanged, and the control system starts to switch from the oil fuel to the synthesis gas fuel control. After the synthesis gas channel is fully purged and replaced, the synthesis gas purge system (511) and the synthesis gas locking system (510) are exited, and the oil return is gradually opened at a uniform speed of V1 to reduce the amount of fuel involved in combustion. At the same time, the synthesis gas pipeline isolation valve (53) is opened, and the synthesis gas fuel control valve (58) is gradually opened at a uniform speed of V1 to increase the low calorific value synthesis gas flow rate from the minimum stable combustion flow rate, wherein the sum of the oil fuel amount ratio and the synthesis gas fuel amount ratio is always 100%; (4) When the fuel flow rate drops to 30%, the switching speed is increased to V2 until the fuel flow rate drops to the minimum stable combustion flow rate, the fuel supply and fuel return are closed, the fuel fuel is cut off, and at the same time, under the action of the load controller, the synthesis gas fuel control valve (58) is adjusted to quickly control the synthesis gas flow rate, the gas turbine completes the fuel switching, and then operates under the synthesis gas condition until the basic load is reached.

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