Afterburning waste heat utilization system and method matched with floating liquefied natural gas carrier and provided with fresh air device

Abstract

According to the afterburning waste heat utilization system and method matched with the floating type liquefied natural gas ship and provided with the fresh air device, the afterburning device provided with the fresh air device is adopted for additionally providing heat for the gas turbine waste heat utilization system, and when a waste heat boiler needs to improve heat output in the gas turbine shutdown state or the gas turbine working state, the afterburning device provided with the fresh air device is used for additionally providing heat for the afterburning waste heat utilization system; the afterburning device is used for providing extra high-temperature flue gas to exchange heat with the waste heat boiler, and the heat output requirements of users on the waste heat boiler under different gas turbine working conditions are met. Different requirements of users on heat output of the waste heat boiler under different working conditions of the system can be met, the application range of combined circulation can be widened, different requirements of more users are met, and the market of combined circulation is expanded.

Description

Technical Field

[0001] The present invention belongs to the field of boiler waste heat utilization, and in particular relates to a system and method for utilizing waste heat from supplementary combustion with a fresh air device for a floating liquefied natural gas ship. Background Art

[0002] Floating liquefied natural gas (FLNG) is a floating liquefied natural gas processing platform. The application of FLNG in deep waters effectively avoids the technical difficulties faced by deep-water pipeline laying, and also provides an economical and effective solution for the development of offshore marginal oil and gas fields. Conventional offshore natural gas development, including the construction of a series of subsequent supporting facilities such as the construction of offshore platforms, requires large investments and a long construction period. In view of the above shortcomings, FLNG has the characteristics of fast commissioning and high efficiency, and integrates the production, storage and unloading of liquefied natural gas.

[0003] The gas-fired combined waste heat recovery unit has the characteristics of high thermal efficiency, short construction period, less pollution, and rapid equipment start and stop, and is suitable as a power generation equipment for FLNG. Waste heat boiler is one of the important equipment in the gas-fired combined cycle system. At present, customers have diverse requirements for the operation time of waste heat boiler and the heat exchange capacity of heat medium. The operation of waste heat boiler in conventional combined cycle depends entirely on the exhaust gas of the gas turbine, and its operation time and heat exchange capacity depend entirely on the operating conditions of the gas turbine. If you need to maintain continuous heat output of the waste heat boiler when the gas turbine is not working or if you need to obtain more heat when the gas turbine is running, you must use a waste heat boiler with a supplementary combustion device. Equipped with a fresh air system to provide air for the supplementary combustion device can improve the thermal efficiency of the supplementary combustion device. Summary of the invention

[0004] The object of the present invention is to provide a system and method for utilizing waste heat from supplementary combustion with a fresh air device for a floating liquefied natural gas ship, which can enable the waste heat boiler to continue working by putting the supplementary combustion device into operation when the gas turbine is shut down, or can increase the heat exchange capacity when the gas turbine is working.

[0005] A post-combustion waste heat utilization system with a fresh air device for a floating liquefied natural gas ship includes a waste heat recovery unit module and a post-combustion module equipped with a fresh air system; the post-combustion module equipped with a fresh air system includes a post-combustion device, a post-combustion ignition device, a post-combustion fan and an ambient air damper; the ambient air damper controls whether the post-combustion fan provides air to the post-combustion device when the post-combustion device is working; the waste heat recovery unit module includes a waste heat boiler inlet flue, a transition flue section, a main flue, a bypass flue, a transition flue The high-temperature flue gas is provided by the supplementary combustion device in the inlet flue of the gas turbine or the waste heat boiler, and after passing through the first section of the transition flue, the ratio of the flue gas entering the main flue and the bypass flue is controlled by the opening and closing of the main flue inlet baffle and the bypass flue inlet baffle, and is discharged through the bypass flue or through the outlet flue of the waste heat boiler after heat exchange between the main flue and the waste heat boiler.

[0006] Furthermore, the main flue inlet baffle and the bypass flue inlet baffle are connected via a mechanical structure and will not be in a closed state at the same time.

[0007] Furthermore, the post-combustion waste heat utilization system also includes a main fan and a backup fan; the main fan and the backup fan are connected to the post-combustion waste heat utilization system to provide sealing air for the entire waste heat recovery system.

[0008] A method for equipping a floating liquefied natural gas ship with a post-combustion waste heat utilization system with a fresh air device comprises the following steps:

[0009] When the gas turbine is in operation, the damper at the inlet flue of the waste heat boiler is opened, and the exhaust gas of the gas turbine enters the first transition flue through the inlet flue of the waste heat boiler. The flow rate of high-temperature flue gas passing through the waste heat boiler is controlled by controlling the opening angle of the damper at the inlet of the main flue. When the damper at the inlet of the main flue is fully opened, if the heat output of the waste heat boiler still needs to be increased, the supplementary combustion device is started through the supplementary combustion ignition device, and the ambient air damper is in a closed state. The additional heat provided by the supplementary combustion device can further increase the heat output of the waste heat boiler. After the flue gas passes through the main flue or the bypass flue, it is discharged to the atmosphere through the second transition flue and the outlet flue of the waste heat boiler;

[0010] When the gas turbine is shut down, the damper on the inlet flue of the waste heat boiler is closed, and the corresponding pneumatic valve remains open to seal the damper on the inlet flue of the waste heat boiler. The damper on the inlet of the main flue is opened, and the supplementary combustion device is started through the supplementary combustion ignition device as the heat source of the waste heat boiler. The ambient air damper is opened to introduce air from the supplementary combustion fan to assist combustion. The supplementary combustion device in the first section of the transition flue generates high-temperature flue gas that enters the main flue, exchanges heat with the waste heat boiler, and the waste heat boiler outputs heat to the outside. The flue gas then enters the second section of the transition flue and the outlet flue of the waste heat boiler in turn, and is finally discharged into the atmosphere.

[0011] The beneficial effects of the present invention are: the present invention can meet the different needs of users for the heat output of the waste heat boiler under different system operating conditions, and can improve the application scope of the combined cycle, cater to the different needs of more users, and expand the market of the combined cycle. In the present invention, the fresh air device is arranged outside the supplementary combustion device to provide air for the supplementary combustion device, and the supplementary combustion device is installed in the boiler inlet flue, and the internal space of the inlet flue or the transition section is used as the supplementary combustion chamber. The system is simple, the equipment investment is small, and the operation and maintenance are convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0013] The present invention is further described below in conjunction with the accompanying drawings.

[0014] like Figure 1 As shown, a post-combustion waste heat utilization system with a fresh air device for a floating liquefied natural gas ship of the present invention comprises a waste heat recovery unit module and a post-combustion module equipped with a fresh air system; the post-combustion module equipped with a fresh air system comprises a post-combustion device 8, a post-combustion ignition device 9, a post-combustion fan 14 and an ambient air damper 17; the ambient air damper 17 controls whether the post-combustion fan 14 provides air to the post-combustion device 8 when the post-combustion device is working; the waste heat recovery unit module comprises a waste heat boiler inlet flue 1, a transition flue section 1 2, a main flue 3, a bypass flue 4, a transition flue section 2 5 , waste heat boiler outlet flue 6, waste heat boiler inlet flue baffle 7, main flue inlet baffle 10, bypass flue inlet baffle 11, waste heat boiler 12 and main flue outlet baffle 13; high-temperature flue gas is provided by the supplementary combustion device 8 in the gas turbine or waste heat boiler inlet flue 1, and after passing through a transition flue section 2, the ratio of flue gas entering the main flue 3 and the bypass flue 4 is controlled by the opening and closing of the main flue inlet baffle 10 and the bypass flue inlet baffle 11, and is discharged through the bypass flue 4 or through the waste heat boiler outlet flue 6 after heat exchange between the main flue 3 and the waste heat boiler 12.

[0015] The working status of the waste heat boiler is classified according to the working conditions of the gas turbine as follows:

[0016] 1. When the gas turbine is in operation, the flue damper 7 at the inlet of the waste heat boiler is opened, and the exhaust gas of the gas turbine enters the first section of the transition flue 2 through the inlet flue 1 of the waste heat boiler. At this time, the flow rate of high-temperature flue gas passing through the waste heat boiler 12 can be controlled by controlling the opening angle of the main flue inlet damper 10. When the main flue inlet damper 10 is fully opened, if the heat output of the waste heat boiler still needs to be increased, the supplementary combustion device 8 can be started by the supplementary combustion ignition device 9, and the ambient air damper 17 is in the closed state. The additional heat provided by the supplementary combustion device 8 can further increase the heat output of the waste heat boiler. After passing through the main flue 3 or the bypass flue 4, the flue gas is discharged to the atmosphere through the second section of the transition flue 5 and the outlet flue 6 of the waste heat boiler.

[0017] 2. When the gas turbine is shut down, the damper 7 of the flue inlet of the waste heat boiler is closed, and the corresponding pneumatic valve is kept open to seal the damper 7 of the flue inlet of the waste heat boiler, and the damper 10 of the main flue inlet is opened, and the supplementary combustion device 8 is started as the heat source of the waste heat boiler through the supplementary combustion ignition device 9. The ambient air damper 17 is opened to introduce air from the supplementary combustion fan 14 to assist combustion, and the supplementary combustion device 8 in the first stage of the transition flue generates high-temperature flue gas that enters the main flue 3 and exchanges heat with the waste heat boiler 12. The waste heat boiler 12 outputs heat to the outside, and the flue gas then enters the second stage of the transition flue 5 and the outlet flue 6 of the waste heat boiler in turn, and is finally discharged into the atmosphere.

[0018] In summary, there are four operating conditions for the waste heat boiler of the fresh air supplementary combustion device, namely:

[0019] 1. When the gas turbine is shut down, the supplementary combustion device does not work and the waste heat boiler is shut down.

[0020] 2. When the gas turbine is shut down, the supplementary combustion device and the waste heat boiler work.

[0021] 3. When the gas turbine is working, the supplementary combustion device does not work, and the waste heat boiler works.

[0022] 4. When the gas turbine is working, the supplementary combustion device is working and the waste heat boiler is working.

[0023] The above four operating conditions affect the flow of flue gas in the flue by controlling the opening and closing of the damper, thereby changing the heat output of the waste heat boiler, allowing users to select the waste heat boiler operating conditions according to their needs.

[0024] The waste heat recovery unit of the gas combined cycle has the advantages of short construction period, rapid equipment start and stop, and high thermal efficiency, which is consistent with the advantages of short construction period and flexible development of FLNG. The heat output of the waste heat boiler on FLNG is mostly used for living needs. The supplementary combustion waste heat boiler equipped with a fresh air device allows the waste heat boiler to continue to provide heat output when the gas turbine is shut down, which is of great significance to improving the practicality of the waste heat boiler. The supplementary combustion device installed inside the boiler flue is more suitable for the offshore application scenario of FLNG. Its fuel is directly sprayed into the flue and mixed with the air introduced by the fresh air system for combustion. The internal space of the boiler flue is used as the supplementary combustion chamber. Its system is simple, light in weight, and saves space on board.

[0025] The above description is only a preferred embodiment of the present invention and is 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 post-combustion waste heat utilization system with a fresh air device for a floating liquefied natural gas ship, characterized in that: The invention comprises a waste heat recovery unit module and a supplementary combustion module configured with a fresh air system; the supplementary combustion module configured with a fresh air system comprises a supplementary combustion device (8), a supplementary combustion ignition device (9), a supplementary combustion fan (14) and an ambient air damper (17); the ambient air damper (17) controls whether the supplementary combustion fan (14) provides air to the supplementary combustion device (8) when the supplementary combustion device is working; the waste heat recovery unit module comprises a waste heat boiler inlet flue (1), a transition flue section (2), a main flue (3), a bypass flue (4), a transition flue section (5), a waste heat boiler outlet flue (6), a waste heat boiler inlet flue (7), a waste heat boiler outlet flue (8), a waste heat boiler outlet flue (9), a waste heat boiler outlet flue (11), a waste heat boiler outlet flue (12), a waste heat boiler outlet flue (13), a waste heat boiler outlet flue (14), a waste heat boiler outlet flue (15), a waste heat boiler outlet flue (16), a waste heat boiler outlet flue (17), a waste heat boiler outlet flue (18), a waste heat boiler outlet flue (19), a waste heat boiler outlet flue (20), a waste heat boiler outlet flue (21), a waste heat boiler outlet flue (22), a waste heat boiler outlet flue (23), a waste heat boiler outlet flue (24), a waste heat boiler outlet flue (25), a waste heat boiler outlet flue (26), a waste heat boiler outlet flue (27), a waste heat boiler outlet flue (28), a waste heat boiler outlet flue (29), a waste heat boiler outlet flue (30), a waste heat boiler outlet flue (31), a waste heat boiler outlet flue (32), a waste heat boiler outlet flue (33), a waste heat boiler outlet flue (34), a waste heat boiler outlet flue (35), a waste heat boiler outlet flue (36), a waste heat boiler outlet flue (37), a waste heat boiler outlet flue (38), a waste A flue baffle (7), a main flue inlet baffle (10), a bypass flue inlet baffle (11), a waste heat boiler (12) and a main flue outlet baffle (13); the high-temperature flue gas is provided by a supplementary combustion device (8) in the inlet flue (1) of a combustion engine or a waste heat boiler, and after passing through a transition flue section (2), the ratio of flue gas entering the main flue (3) and the bypass flue (4) is controlled by opening and closing the main flue inlet baffle (10) and the bypass flue inlet baffle (11), and the flue gas is discharged through the outlet flue (6) of the waste heat boiler after heat exchange between the bypass flue (4) or the main flue (3) and the waste heat boiler (12).

2. The post-combustion waste heat utilization system with a fresh air device for a floating liquefied natural gas vessel according to claim 1 is characterized in that: The main flue inlet baffle (10) and the bypass flue inlet baffle (11) are connected via a mechanical structure and will not be in a closed state at the same time.

3. The post-combustion waste heat utilization system with a fresh air device for a floating liquefied natural gas vessel according to claim 1 is characterized in that: The post-combustion waste heat utilization system further comprises a main fan (15) and a standby fan (16); the main fan (15) and the standby fan (16) are connected to the post-combustion waste heat utilization system and are used to provide sealing air for the entire waste heat recovery system.

4. A method for utilizing the residual heat from post-combustion combustion of a floating liquefied natural gas vessel equipped with a fresh air device according to claim 1, characterized in that: The following steps are involved: When the engine is in operation, the flue damper (7) at the inlet of the waste heat boiler is opened, and the exhaust gas of the engine enters the first transition flue (2) through the inlet flue (1) of the waste heat boiler. The flow rate of high-temperature flue gas passing through the waste heat boiler (12) is controlled by controlling the opening angle of the main flue inlet damper (10). When the main flue inlet damper (10) is fully opened, if the heat output of the waste heat boiler still needs to be increased, the supplementary combustion device (8) is started by the supplementary combustion ignition device (9), and the ambient air damper (17) is in a closed state. The additional heat provided by the supplementary combustion device (8) can further increase the heat output of the waste heat boiler. After the flue gas passes through the main flue (3) or the bypass flue (4), it is discharged to the atmosphere through the second transition flue (5) and the outlet flue (6) of the waste heat boiler; When the gas turbine is in shutdown state, the damper (7) at the inlet flue of the waste heat boiler is closed, and the corresponding pneumatic valve remains open to seal the damper (7) at the inlet flue of the waste heat boiler, and the damper (10) at the inlet of the main flue is opened, and the supplementary combustion device (8) is started as the heat source of the waste heat boiler through the supplementary combustion ignition device (9), and the ambient air damper (17) is opened to introduce air from the supplementary combustion fan (14) to assist combustion, and the supplementary combustion device (8) in the first section of the transition flue generates high-temperature flue gas that enters the main flue (3), exchanges heat with the waste heat boiler (12), and the waste heat boiler (12) outputs heat to the outside, and the flue gas then enters the second section of the transition flue (5) and the outlet flue (6) of the waste heat boiler in sequence, and is finally discharged into the atmosphere.

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