JPH0566485B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an interlock system for cooperative operation between liquefied gas supply equipment and power generation equipment in a thermal power plant that uses liquefied gas as fuel.

<Prior art> In a power generation plant that uses liquefied gas as fuel, when the power generation equipment is operated at an intermediate load, when the power generation equipment load drops below a certain level, the load on the liquefied gas vaporizer falls below the minimum stable load. , there was a risk that the fuel gas main pipe pressure could not be well controlled. Therefore, in the past, an interlock was provided to prevent the load on the power generation equipment from dropping below a certain level.

<Problems to be solved by the invention> However, although the main pipe pressure is well controlled when the lower limit of the power generation equipment load is set in this way, it is necessary to set the lower limit of the power generation equipment load in order to cope with various conditions. It had to be set quite large, which had the disadvantage of narrowing the operational range of the power generation equipment.

In view of these shortcomings of the prior art, the main purpose of the present invention is to set the lower limit of the power generation equipment load as low as possible in response to changes in various conditions, thereby increasing the operational range of the power generation equipment. The objective is to provide an interlock system that can be expanded.

<Means for Solving the Problems> According to the present invention, such an object is an interlock system between liquefied gas supply equipment and power generation equipment in a thermal power plant that uses liquefied gas as fuel. , an interlock that limits the lower limit level of the load of the power generation equipment based on a minimum fuel gas output amount signal calculated from the amount of boil-off gas generated that fluctuates depending on natural and artificial conditions and the minimum stable load of the carburetor during operation. This is achieved by providing a method.

<Effect> The amount of BOG generated fluctuates depending on natural conditions such as temperature and atmospheric pressure, and artificial conditions such as acceptance of liquefied gas, but if the amount of BOG generated is accurately predicted, the lower limit of the power generation equipment load can be determined. Since the value can be kept sufficiently low, the main pipe pressure can be well controlled and the operable range of the power generation equipment can be widened.

<Embodiments> Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a simplified configuration diagram of a thermal power plant using liquefied natural gas (hereinafter referred to as LNG) as fuel, to which a fuel gas main pipe pressure control device according to the present invention is applied. LNG 9 stored in the LNG storage tank 1 is sent to a vaporizer, for example, an open rack vaporizer 4, by a primary pump 2 and a secondary pump 3, and the liquefied gas is vaporized by seawater or the like serving as a heat source. The vaporized gas is supplied as fuel gas to the power generation equipment 7 via the fuel gas main pipe 5.

In the power generation equipment 7, so-called combined cycle power generation is performed in which a gas turbine is operated using fuel gas and steam generated from waste heat of the gas turbine is used to drive the steam turbine.

On the other hand, boil-off gas (BOG) is generated from the LNG 9 stored in the LNG storage tank 1 due to external heat input, and remains in the gas phase section 10. The amount increases as the temperature rises, and also temporarily increases when LNG is received into tank 1 from the ocean tanker. BOG is compressed by the compressor 6 and sent to the fuel gas main pipe 5.

Generally, a plurality of vaporizers 4 are used, but the vaporizers 4 are stopped so that they can be restarted smoothly. (to maintain cooling state), for example, 1.5ton/hour.
It is necessary to maintain a gas flow rate of, for example, 5.6 tons/in order to stably control the load on the carburetor.
It is necessary to secure a flow rate of 1 hour. Furthermore, since the amount of BOG generated is usually controlled by natural conditions, the amount of BOG generated under given natural conditions can be estimated by computer simulation or the like. In addition, as an artificial condition, LNG
When receiving into storage tank 1, the amount of BOG generated is, for example,
This will increase to 52.9ton/hour.

The flow rate of fuel gas supplied to power generation equipment 7 is
It is given as the sum of the flow rate of BOG gas sent out by the BOG compressor 6 and the flow rate of vaporized gas sent out from the vaporizer 4, and in the power generation equipment 7, the fuel consumption is determined by the flow rate of the liquefied gas supplied. The lower limit of the power generation equipment load can be kept low within the range that does not fall below. If the fuel consumption of the power generation equipment falls below the flow rate of the supplied fuel, the pressure in the main gas pipe 5 cannot be stably controlled.

Figure 2 is a block diagram showing the process of creating the minimum fuel gas output signal that provides the lower limit of the power generation equipment load. A signal corresponding to the estimated amount of BOG generation at the time is generated and transmitted to the adder 16. Also adder 16
The flow rate for automatic cooling maintenance of the vaporizer is
Signal corresponding to the flow rate of 1.5ton/hour multiplied by the number of vaporizers, 1.5nton/hour (block 12)
Or minimum stable load of vaporizer 5.6ton/hour and n-
The sum of the flow rate of 1.5 (n-1) ton/hour required to keep one vaporizer automatically cooled, {5.6 + 1.5 (n-
1) A signal corresponding to either ton/hour (block 13) is given. The switching logic of switch 15 for switching which signal from block 12 or block 13 is supplied to adder 16 will be explained in detail later.

The signal from the adder 16 and the signal from the block 14 are transmitted to the switch 17.
7 selects one of these signals and supplies it to the rate limiter 18. From block 14,
{Amount of BOG generated when receiving liquefied gas, e.g. 52.9 ton/hour} + {Minimum stable load on the vaporizer, e.g. 5.6 ton/hour} + {Liquification required to keep n-1 vaporizers cool Gas flow rate, e.g. 1.5 (n-
1) A signal corresponding to ton/hour} is transmitted.
The switch 17 normally selects the adder 16 side, but selects the block 14 side when receiving liquefied gas.

Rate limiter 18 limits the rate of rise of the minimum fuel gas delivery signal and is activated only when block 14 is selected. rate limiter 1
The output signal 19 of 8 becomes the final fuel gas output minimum amount signal. For example, if two lines of power generation equipment are used, the distribution units 20 and 21 may appropriately adjust the fuel gas output minimum amount signal. The power generation equipment of each system will be interlocked by distribution.

FIG. 3 shows the switching logic of switch 15 in FIG. 2. Switch 15 selects block 12 when BOG independent operation is selected or when the carburetor is not automatically operated.
However, if carburetor operation is selected and the automatic operation load of the carburetor exceeds a certain level,
Switch 15 will select block 13. Block 13 is also selected when the BOG compressor trips or the like causes a transition from BOG independent operation to carburetor operation.

Next, the state of change in the above-mentioned minimum fuel gas delivery amount signal will be explained based on FIGS. 4 to 6.

Figure 4 shows the process when receiving liquefied gas into storage tank 1.
The figure shows changes in the minimum fuel gas delivery signal as the amount of BOG generation increases. Before the start of liquefied gas reception, a minimum fuel gas sending amount signal is sent out from block 11, which takes into account some allowance for the amount of BOG generated according to natural conditions, and is transmitted as it is to the power generation equipment side. When 45 minutes have passed since the start of receiving liquefied gas, the switch 17 is switched to the block 14 side and the rate limiter 18 is activated at the same time.
The minimum fuel gas delivery amount signal increases linearly for about 45 minutes, but after reaching a certain value, this value remains constant. When the reception of liquefied gas is completed, the switch 17 is switched to the adder 16 side, and the state is returned to the state before the start of reception of liquefied gas.

FIG. 5 shows the case of switching from carburetor operation to BOG independent operation and then returning to carburetor operation. If the carburetor operation is selected, the carburetor is throttled to the automatic cooling maintenance state, and the automatic operation load of the carburetor is above a certain level, the switch 15 is switched to the block 13 side, and the minimum fuel gas delivery amount signal is output. is at a certain level. When switched to BOG independent operation,
The switch 15 is moved to the side of the block 12, and the minimum fuel gas delivery amount signal is held at a level lower than the above-mentioned level, and remains at a level slightly higher than the BOG generation amount mainly due to natural conditions. Meanwhile, the vaporizer is reduced to all cold-hold operating conditions. When the vaporizer is restarted, the liquefied gas flow rate at the vaporizer inlet gradually increases until it reaches a certain level.
For example, when setting the value to 5.6+1.5 (n-1) ton/hour, the switch 15 is moved to the block 13 side, and the level of the minimum fuel gas delivery amount signal is increased.

FIG. 6 shows a case where the BOG compressor is tripped during BOG independent operation and shifts to carburetor operation. Before the BOG compressor trips, the minimum fuel gas sending amount signal is held at a level slightly higher than the actual amount of BOG generated, but when the BOG compressor trips, the signal is supplied to the main fuel pipe.
Since the BOG flow rate suddenly decreases, the carburetor is started to compensate for this, the switch 15 is forced to the side of the block 13, and the level of the minimum fuel gas delivery signal increases.

In this way, at the liquefied gas supply equipment side,
Predicted BOG generation amount, liquefied gas vaporizer operating status,
A minimum fuel gas sending amount signal is created from data such as whether liquefied gas is accepted or not, and this signal is sent to the power generation equipment. On the power generation equipment side, if the amount of fuel gas exceeds the value indicated by this signal is consumed, the carburetor operating load will not fall below the minimum stable load.
The fuel gas main pipe pressure can be well controlled.

<Effects of the Invention> In this way, by operating the power generation equipment and the liquefied gas supply equipment in a coordinated manner, the operable range of the power generation equipment can be widened, and moreover, all fuel gas main pipe pressures can be reduced. Automatic control enables efficient operation of thermal power plants and eliminates the need for operator effort to coordinate between power generation equipment and liquefied gas supply equipment. Because it can be done, the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a thermal power plant to which the present invention can be applied. FIG. 2 is an explanatory diagram showing the flow of the configuration for generating the minimum fuel gas delivery amount signal. FIG. 3 is a flow diagram illustrating the switching logic of switch 15 of FIG. Fourth
6 through 6 are graphs showing changes in the minimum fuel gas delivery amount signal. 1... LNG storage tank, 2... Primary pump,
3... Secondary pump, 4... Carburetor, 5...
Fuel gas main pipe, 6... BOG compressor, 7... Power generation equipment, 8... Fuel gas supply equipment, 9... LNG,
10... Gas phase part in storage tank, 11-14... Block, 15... Switch, 16... Adder, 17...
...Switch, 18...Rate limiter, 19...
Output signal, 20, 21...distribution unit.

Claims (1)

[Claims] 1 This is an interlock system between liquefied gas supply equipment and power generation equipment in a thermal power plant that uses liquefied gas as fuel, and is an interlock system that controls the amount of boil-off gas generated and the vaporizer during operation, which fluctuates depending on natural and artificial conditions. An interlock system that limits the lower limit level of the load of the power generation equipment based on the minimum fuel gas delivery amount signal calculated from the minimum stable load.