JPH036332B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention uses exhaust gas energy from a system to drive a turbine, and supplies the air required by the system by a compressor installed coaxially with the turbine. The present invention relates to a method for starting a turbo compressor system.

[Conventional technology]

This type of turbo compressor aims to effectively recover energy within the system without wastefully discarding the exhaust gas energy of the system, and a typical example is a fuel cell power generation system. This fuel cell power generation system will be described below as an example.

Fuel cell power generation systems have advantages over conventional steam power generation, such as higher efficiency and better environmental protection, and have been actively developed in recent years with the aim of putting them into practical use. A fuel cell power generation system consists of a fuel cell body consisting of an air electrode, a fuel electrode, and an electrolyte layer, and a reformer that reforms hydrocarbon fuel such as natural gas and supplies hydrogen gas as fuel to the fuel cell body. , a turbo compressor that supplies air to the fuel cell main body and a reformer. The performance of the fuel cell main body tends to improve as the pressure of the reactant gas increases, and therefore the operating pressures of fuel, air, and each reactant gas are maintained at, for example, about 4 to 6 kg/cm ² g. At this time, a large amount of power is required to compress the air, but this power is provided by the turbine of the turbo compressor, which introduces the combustion exhaust gas from the reformer and excess air from the air electrode of the fuel cell main body.
In other words, this turbo compressor recovers energy from the system's exhaust gas with a turbine and supplies the necessary compressed air with a coaxial compressor, thereby recovering power within the system and improving system efficiency. It is something.

Now, in such a fuel cell power generation system, in order to start the system, it is first necessary to start the turbo compressor, but since the system exhaust gas that serves as the driving source cannot be obtained in the initial stage, some external energy must be applied. It is necessary to start up the turbo compressor.

A specific conventional method for this purpose is disclosed, for example, in Japanese Patent Application Laid-open No. 160577/1983, and the system thereof is shown in FIG. In the figure, 1 is a system including a combustion furnace consisting of a fuel cell main body, a reformer, etc., 2 is a turbine 2a that is driven by exhaust gas from system 1, and supplies the compressed air necessary for system 1; A turbo compressor 3 consisting of a turbine 2a and a compressor 2b arranged coaxially
is an air supply pipe installed on the inlet side of the compressor 2b of this turbo compressor 2, 4 is a switching valve installed on this air supply pipe 3, and 5 is an air supply pipe installed on the outlet side of the compressor 2b, from the compressor 2b. 6 is a control valve installed in the air supply pipe 5, 7 is a system exhaust gas pipe that guides the exhaust gas from the system 1 to the turbine 2a, and 8 is the air supply pipe 5 and the system. Bypass piping that bypasses the exhaust gas piping 7; 9 is an auxiliary combustion furnace installed in this bypass piping 8 that energizes the turbine power; 10 is a control valve installed in the bypass piping 8;
Adjust the amount of air supplied to the 11 is a fuel supply pipe that supplies fuel to the auxiliary combustion furnace 9, 12 is a starting compressed air supply device, and 13 is an introduction for guiding air from this starting compressed air supply device 12 to the inlet air supply pipe 3 of the compressor 2b. Piping, 14 is this introduction piping 13
This is a switching valve installed in the Although not shown in the drawings, for example, as disclosed in JP-A-58-12268, an air release pipe is provided in the air supply pipe 5, and an air release control valve is provided on this air release pipe. be. This is to adjust the discharge air pressure of the compressor 2b to a constant value in response to load fluctuations in the system 1.

Next, the startup operation of the turbo compressor in the conventional system configured as described above will be explained. First, upon starting, the switching valve 4 and the regulating valve 6 are closed, the switching valve 14 and the regulating valve 10 are opened, and compressed air is discharged from the starting compressed air supply device 12.
As a result, the compressed air passes through the compressor 2b and is guided to the auxiliary combustion furnace 9. At this time, the compressed air is heated by supplying fuel to the auxiliary combustion furnace 9 from the fuel supply pipe 11 and causing the auxiliary combustion furnace 9 to burn. It is then put into the turbine 2a as it is. As the temperature of the compressed air increases, the turbo compressor 2 starts to be activated, and at the same time the air pressure is increased. When the temperature necessary for the turbo compressor 2 to operate on its own is reached, the switching valve 4 is opened, the startup compressed air supply device 12 is stopped, and the switching valve 14 is closed, thereby allowing the turbo compressor 2 to operate on its own. Transition. This state is, so to speak, a standby state, and air can be sent out at any time as required by the system 1. That is, by opening the control valve 6, compressed air is supplied to the system 1, and at the same time, the compressed air is used for combustion and other purposes within the system 1, and is then led as exhaust gas to the turbine 2a via the system exhaust gas pipe 7.

However, in the conventional system described above, the startup compressed air supply device 12 is stopped and the turbo compressor 2 shifts to self-operation, but at this time, there is a temporary pressure drop, and this pressure drop causes the turbine power This causes the compressor power to become unbalanced, leading to a stall, and resulting in the disadvantage that stable self-operation of the turbo compressor 2 cannot be achieved. That is, an important issue has been how to smoothly shift the turbo compressor 2 to self-operation after stopping the startup compressed air supply device 5.

[Summary of the invention]

This invention was made in view of the drawbacks of the above-mentioned systems, and when the system is started, the turbo compressor is started by the startup compressed air supply device, and the power of the turbo compressor is generated as the combustion energy of the auxiliary furnace is energized. The air release control valve allows the air pressure to rise outside the system, and the pressure drop in the compressed air due to the stoppage of the start-up compressed air supply system is compensated for by the air release control valve, which allows the turbo compressor to operate on its own, resulting in stable operation. The purpose of this invention is to provide a method for starting a turbo compressor system that can realize self-operation of a turbo compressor.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIG. 2. In the figure, 1 to 14 have the same configuration as the conventional system described above. 15 is compressor 2
16 is an atmosphere release control valve provided in the atmosphere release pipe 15, and 17 is a startup bypass used, for example, when starting the system. This is a pipe that bypasses the air from the compressor 2b from the air supply pipe 5 to the system exhaust gas pipe 7, and a control valve 18 is arranged side by side.

Next, the operation will be explained. When starting the system, first close the switching valve 4, the control valves 6 and 10, and the atmospheric release control valve 16, and then close the switching valve 14 and the control valve 18.
, and start the startup compressed air supply device 12. Compressed air from the startup compressed air supply device 12 passes through the compressor 2b, and is input into the turbine 2a via the air supply pipe 5, the startup bypass pipe 17, and the system exhaust gas pipe 7. At this time, if the capacity of the starting compressed air supply device 12 is sufficient to start the turbo compressor 2, the turbo compressor 2 will start, and at the same time the pressure of the compressed air from the compressor 2b will rise. In this state, the control valve 10 is opened and the auxiliary combustion furnace 9
At the same time, air is introduced through the fuel supply pipe 11 and fuel is also introduced into the auxiliary combustion furnace 9 to start combustion. The combustion exhaust gas from the auxiliary combustion furnace 9 returns through the startup bypass piping 16 and the compressed air and the system exhaust gas piping 7
The gases are merged inside and fed into the turbine 2a. If the turbo compressor 2 is already started at the time of ignition of the auxiliary combustion furnace 9, the turbine power increases as the temperature of the gas input to the turbine 2a increases, and the discharge air pressure of the compressor 2b further increases. If the turbo compressor 2 has not yet been activated at the time of ignition of the auxiliary combustion furnace 9, the turbo compressor 2 will be activated during the process of temperature rise of the gas input into the turbine 2a. No matter at what point the turbo compressor 2 is started, the rotational speed increases quickly when the turbo compressor 2 starts, and the discharge air pressure of the compressor 2b increases rapidly in a short period of time (within a few seconds). . Therefore, in order to prevent unstable combustion in the auxiliary combustion furnace 9 due to rapid pressure fluctuations, the turbo compressor 2 is started before the auxiliary combustion furnace 9 is ignited, that is, when the startup compressed air supply device 12 is started. It is most desirable to do so. After the turbo compressor 2 is started, the pressure of the compressed air gradually increases as the temperature of the gas at the inlet of the turbine 2a rises due to combustion in the auxiliary combustion furnace 9. The atmospheric release control valve 16 begins to open from the point at which the compressed air pressure exceeds the rated pressure, and the atmospheric release control valve 16 is adjusted to gradually open in response to an increase in turbine power so that the compressed air pressure does not exceed the rated pressure. . Although not shown in the figure, for this operation, a pressure sensor is provided on the discharge side of the compressor 2b, and a pressure controller is connected to the opening adjustment mechanism (actuator) of the atmospheric release control valve 16 so that the pressure of the compressed air is constant. The control signal is output by In this way, when the turbine 2a inlet temperature reaches a temperature sufficient for the turbo compressor 2 to start self-operation, the switching valve 4 is opened, the starting compressed air supply device 12 is stopped, and the switching valve 14 is closed. This causes the turbo compressor 2 to become self-operating. At this time, the pressure at the outlet of the compressor 2b tends to drop temporarily due to the stoppage of the startup compressed air supply device 12, but the atmospheric release control valve 16 is controlled in the closing direction by the action of a pressure controller (not shown). and the compressed air pressure is kept constant. The throttle of the atmospheric release control valve 16 is completed, and the transition to self-operation of the turbo compressor 2 is completed in a state where the pressure of the compressed air is maintained at a constant rated value. Compressed air supply device 12 for startup
The combustion amount of the auxiliary combustion furnace 9 or the inlet temperature of the turbine 2a at the time of stopping the start-up compressed air supply device 12 is determined when the compressed air pressure is maintained at a constant rated value and the atmospheric release control valve 16 is fully closed. Alternatively, it is desirable to set the opening to a value that maintains the opening with some margin. After the turbo compressor 2 shifts to self-operation, the air passing through the startup bypass piping 17 is gradually switched to the system 1 by gradually opening the control valve 6 and gradually closing the control valve 18.
Compressed air from the compressor 2b is now input to the system 1.

FIG. 3 shows a comparison of changes in the flow rate, pressure, and temperature of compressed air during the startup process of the turbo compressor 2 with the conventional method. In the figure, the solid line is a startup mode diagram of the method according to the present invention, and the dotted line is a startup mode diagram of the conventional method. First, at point A, the turbo compressor 2 is started by starting the starting compressed air supply device 12. Thereafter, the auxiliary combustion furnace 9 is ignited at point B to start combustion. The pressure of the compressed air increases due to the rise in air temperature at the inlet of the turbine 2a, but after the rated pressure is exceeded, the pressure is maintained constant by opening the atmosphere release control valve 16, and the temperature at the inlet of the turbine 2a increases. The degree of opening of the atmospheric release control valve 16 also increases as the amount increases. After that, at point D, the starting compressed air supply device 12
When the compressed air is stopped, the pressure of the compressed air is maintained at a constant value by closing the atmosphere release control valve 16. In this way, even when the startup compressed air supply device 12 is stopped, pressure fluctuations in the compressed air can be suppressed,
The turbo compressor 2 can be operated stably on its own. Comparing this with the conventional method, the superiority of this invention is clear. That is, when the startup compressed air supply device 12 is stopped (point D), the pressure fluctuation of the compressed air and the stall of the turbo compressor 2, which conventionally occur, are not caused.

By the way, in the above embodiment, the case where the system is a fuel cell power generation system has been described, but it goes without saying that the present invention can be applied to other systems such as chemical plants. be able to.

〔Effect of the invention〕

As explained above, in this invention, when the system is started, the turbo compressor is started by the startup compressed air supply device, and the power increase of the turbo compressor due to the activation of combustion energy in the auxiliary combustion furnace is removed from the system by the atmosphere release control valve. The compressed air pressure drop due to the stoppage of the startup compressed air supply device is compensated for by throttling the air release control valve, allowing the turbo compressor to operate on its own, which may cause the turbo compressor to stall. This makes it possible to realize stable self-operation of the turbo compressor.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing a starting method of a conventional turbo compressor system, Fig. 2 is a system diagram showing a starting method of a turbo compressor system according to an embodiment of the present invention, and Fig. 3 is a system diagram showing a starting method of a turbo compressor system according to an embodiment of the present invention. FIG. 3 is a startup mode diagram showing process states; In the figure, 1 is the system, 2 is the turbo compressor, 2a is the turbine, 2b is the compressor, 5 is the air supply pipe, 7 is the system exhaust gas pipe, 8 is the bypass pipe, 9 is the auxiliary combustion furnace, and 12 is the compressed air for startup. A supply device, 15 is an air release pipe, and 16 is an air release control valve. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A turbo compressor consisting of a turbine driven by exhaust gas from the system and a compressor that is directly connected coaxially with the turbine and supplies the compressed air necessary for the system, and a system on the inlet side of the turbine of this turbo compressor. an auxiliary combustion furnace installed on the bypass piping that bypasses and supplies a part of the air from the compressor to supplement the insufficient power of the turbine; and a starter furnace installed in the inlet side system or the outlet side system of the compressor. In a turbo compressor system equipped with a compressed air supply device, an atmosphere release piping branched to the outlet side system of the compressor, and an atmosphere release control valve provided on this atmosphere release piping, when the system is started up, , the turbo compressor is started by the start-up compressed air supply device, and the increase in power of the turbo compressor caused by energizing the combustion energy of the auxiliary combustion furnace is released to the outside of the system by the atmosphere release control valve; A method for starting a turbo compressor system, characterized in that the turbo compressor is operated on its own by compensating for a pressure drop in compressed air due to the stoppage of a compressed air supply device by throttling the atmosphere release control valve.