JPS63277809A - Cryogenic power generating installation making use of lng - Google Patents

Abstract

PURPOSE:To improve reliability by employing a sliding pressure operation system allowing a governor opening to be constant, providing a control device establishing the amount of LNG vaporization, providing a control circuit connecting a flow regulating valve with a LNG pump, and relaxing thereby service conditions. CONSTITUTION:A LNG pump 1 is connected with an expansion turbine 5 via a flow regulating valve 2, a LNG evaporator 3 and a governor 4. A control device 30, an operation device 31 and a pump control device 32 are connected with each other through an operation signal lines 40, 41 and 42 between LNG pump 1 and a flow regulating valve 2. Operations are carried out by a requesting command for the amount of LNG vaporization from the control device 30 for computing the necessary delivery pressure value of the pump so as to allow the pump control device 32 to control the revolving speed of LNG pump 1. Power consumption can thereby be maintained at the minimum required amount for attempting the improvement of reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an LNG cold energy power generation facility suitable for vaporizing and supplying LNG and having equipment for generating power by utilizing the cold energy possessed by LNG.

[Conventional technology]

FIG. 3 shows a system diagram of an example of a conventional LNG cold energy power generation facility. In the figure, LNG is supplied from a conduit 10 at a temperature of about 1160'C, is pressurized to a predetermined pressure by an n% LNG pump 1, and the required LNG vaporization amount is controlled by a flow rate control valve 2, and an LNG evaporator 3 Sent to. By supplying seawater, etc., which serves as a heating source, through conduit 4, LNG is constantly heated! The gas is vaporized and becomes a high-pressure gas (hereinafter referred to as natural gas), which enters the expansion turbine 5I from the conduit 13 via the control valve 4.

Here, the natural gas operates the expansion turbine 5 and drives the connected generator 6 to generate electricity and power. On the other hand, the natural gas expanded in the expansion turbine 5 to a low pressure and low temperature is heated to room temperature by a heating source (seawater, etc.) supplied from a conduit in a heater 7, and then sent as fuel to a power plant, etc. through a conduit 15. Supplied as gas. In order to maintain the pressure of the natural gas in the conduit 15 at a constant pressure required at a 3M power station, etc., the outlet pressure of the expansion turbine 5 is operated at a substantially constant pressure.
Ru.

The regulating valve 4 at the inlet of the expansion turbine 5 uses a so-called variable pressure operation method, in which the opening is set at a point where the efficiency of the expansion turbine 5 is high, and the opening is kept constant during normal operation. It performs highly efficient power generation over a wide range from low to high loads. Figure 4 shows the characteristics of equipment using the variable voltage operation method. In the figure, the expansion turbine front pressure characteristic line is L
The characteristic is that the pressure increases as the amount of NG vaporized increases. In other words, the rotation speed of the expansion turbine is constant and the passage area is small, so if the natural gas flow rate increases, the old pressure of the expansion turbine will inevitably increase due to variable pressure turbine operation. becomes.

On the other hand, the pump outlet pressure characteristics in Fig. 4 are as follows: First, the expansion turbine front pressure characteristics 2
The capacity is determined by using 23 points, which are the 4 points plus the pressure loss required for the flow rate control valve and the pressure loss of equipment piping etc. up to the expansion turbine 5, as the rated design point of the LNG pump I. Since a centrifugal submerged pump is usually used as an LNG pump, the pump outlet pressure characteristic curve shown in Fig. 4 is
, the pressure increases as the amount of LNG vaporized decreases. Note that related devices of the second type include, for example, JP-A-56-104105JiiJ.

[Problem that the invention seeks to solve]

In the prior art described above, as shown in FIG. 4, the pump outlet pressure and the expansion turbine front pressure exhibit opposite pressure characteristics due to changes in the LNG vaporization amount. This means that, for example, in Figure 4, at point A, the difference between the pump outlet pressure P1 and the expansion turbine P2 is reduced by the flow control valve 2 (see Figure 3). Therefore, as the LNG vaporization amount decreases, the pressure difference (
PIP2) shows an increasing tendency. That is, Ps P2
The pressure difference causes a loss of power in the LNG pump 1, and the pressure difference in the tiL quantity control valve 2 increases, so it is assumed that the flow rate control valve may vibrate, make noise, and cavitate due to liquefied gas. However, there was a problem in that the usage conditions were harsh and reliability deteriorated.

The purpose of the present invention is to obtain a pump outlet pressure characteristic curve that has the same tendency as the expansion turbine front pressure characteristic curve depending on the amount of LNG vaporization, to minimize the pump power, and as a result, to reduce the difference in the flow rate control valve. Since the pressure can also be minimized, the usage conditions can be relaxed and reliability can be improved.

A control device is provided, and the control device controls the flow rate control valve, and also controls the LN through a calculation device and a pump control device.
This is achieved by controlling the G pump.

〔Example〕

An embodiment of the present invention will be described below with reference to the system diagram shown in FIG.

In the figure, the LNG pump 1 is connected to the flow xm regulating valve 2°LNG evaporator 3. The expansion turbine 5 and the conduit 11 through the regulator valve 4.
12. Connect at 13. A control device 30. An arithmetic unit [31] and a pump control device are provided with a control circuit connected via operation signal lines 40, 41 and 42. 5@[a6 is directly connected to the expansion turbine 5, and a warmer 7 is provided from the outlet of the expansion turbine 5 via a conduit 14. The LNG evaporator 3 and warmer 7 are
A conduit field 21 serving as a heating source is provided. A conduit 10 is provided on the inlet side of the LNG pump 1 to supply LNG, and a conduit 15 is provided on the outlet side of the warmer 7 to supply natural gas to the outside. In FIG. 1, a control device for setting the amount of LNG vaporization controls the flow control valve 2 to adjust the amount of LNG vaporization, and at the same time sends a signal from the control value [30 to the calculation device 131. , stores the front pressure characteristics of the expansion turbine 5 and the outlet pressure characteristics of the LNG pump l with respect to the LNG vaporization amount, performs calculations based on the LNG vaporization amount request command from the control value [30, calculates the required pump outlet pressure value, and controls the pump. LNG pump 1 by device 132
control the rotation speed. According to this embodiment, as shown in FIG.

Since it is possible to obtain a pump outlet pressure characteristic curve with the same tendency as the expansion turbine front pressure characteristic curve depending on the amount of LNG vaporized, it is possible to set the pump power consumption to the minimum necessary commensurate with the amount of LNG vaporized. The differential pressure across the flow rate control valve 2 is also minimized, which eases usage conditions and improves reliability.

In addition to the embodiment according to the present invention, similar effects can be obtained in a method of controlling the rotation speed of the LNG pump l by detecting the pressure before the expansion turbine or by detecting the differential pressure of the LNG flow rate control valve 2. is obtained.

In addition, for natural gas consumed in thermal power plants, etc., the required load g (LNG vaporization amount) constantly fluctuates (power consumption drops sharply around noon and at night), so The average load operation rate is about 60-70%. In facilities where the amount of LNG vaporized changes in this way, the power of the pump is also reduced in proportion to changes in operational conditions.

This has the effect of reducing operating costs and improving the reliability of the entire facility by preventing problems such as vibration, noise, and cavity scenes caused by lowering the differential pressure of the LNG flow rate regulating valve.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a pump outlet pressure characteristic curve that has the same tendency as the expansion turbine front pressure characteristic curve depending on the amount of LNG vaporized, so that the pump power consumption can be kept to the minimum necessary commensurate with the amount of LNG vaporized. Can be done. As a result, the differential pressure of the fijl control valve is also reduced to the necessary minimum, which has the effect of easing usage conditions and improving reliability.

[Brief explanation of the drawing]

Figure 9E1 is a system diagram showing an example of LNG cold energy power generation equipment according to the present invention, Figure 2 is a line diagram showing the characteristics of the equipment according to the invention, Figure vg3 is a system diagram according to the conventional method, and Figure 4 is a diagram showing the conventional method. It is a diagram showing the characteristics of equipment. 1...LNG pump, 2...Flow rate control valve, 3...LNG evaporator, 4...Adjustment valve, 5
...Expansion turbine, 6... Generator, 7
...Warmer, 10~15.20゜B...
・Conduit, (9)... Control *iil, 31...
...Arithmetic device, Figure A4

Claims (1)

[Claims] 1. Pressurize LNG with a pump, evaporate it with a heat exchanger, send the vaporized natural gas to an expansion turbine, operate it, and generate electricity with a generator connected to the expansion turbine. In LNG cold energy power generation equipment that reheats the gas to room temperature in a heat exchanger and supplies natural gas as fuel, we have adopted a variable pressure operation method in which the opening of the control valve installed at the inlet of the expansion turbine is constant. , a control device for setting the amount of LNG vaporization is provided between the LNG pump and the flow rate control valve, and a control circuit connected to the flow rate control valve via an operation signal line; L
A power generation facility using LNG cold energy, characterized in that it is equipped with a control circuit connected to an NG pump via an operation signal line.