JP2001263592A - Method and device for vaporizing lng - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vaporizing method and a vaporizing device preventing a decrease in vaporized gas amount even if seawater temperature is lowered. SOLUTION: This LNG vaporizing method generates an LNG gas by spraying seawater to a pipe in which the LNG passes through. When the seawater temperature of a vaporizer inlet becomes not more than a specified value, vapor is supplied to the seawater to raise the supplied seawater temperature above the specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an LNG vaporization method and apparatus for vaporizing LNG with seawater.

[0002]

2. Description of the Related Art LNG is transported or stored in liquid form at low temperature (about minus 160 ° C.). When this is used, it is vaporized and sent to factories and homes as gas. Vaporization is performed by heating and evaporating LNG with the sensible heat of seawater.

FIG. 2 shows the configuration of a conventional LNG vaporizer.
A large number of heat transfer tubes 1a stand in the LNG vaporizer 1, and a spray header 2 for spraying seawater to the heat transfer tubes 1a is provided at an upper portion. An LNG supply line 3 is provided below the LNG vaporizer 1 and connected to the heat transfer tube 1a via a header, and an LNG gas line 4 is provided above. A seawater line 5 is connected to the spray header 2.

[0004] The flow controller 10 is connected to the LNG supply line 3
And a flow meter 15 and a thermometer 12 provided in the seawater line 5, and the flow rate of the LNG is controlled by the flow control valve 7 according to the temperature and the flow rate of the seawater.

[0005]

When the seawater temperature drops to 0 to 2 ° C., icing occurs on the heat transfer tube 1a. When icing occurs, the heat transfer efficiency decreases, and sufficient vaporization cannot be performed in the pipe. For this reason, the flow rate controller 10 significantly reduces the flow rate of LNG so that vaporization is sufficiently performed. This flow rate limitation may reach 50% of the maximum capacity, and there is a problem that the vaporization capacity is greatly reduced depending on the seawater temperature.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a vaporization method and apparatus which do not reduce the amount of vaporized gas even when the temperature of seawater decreases.

[0007]

In order to achieve the above object, an invention of claim 1 is an LNG vaporization method for generating LNG gas by spraying seawater on a pipe through which LNG passes, and comprising: When the seawater temperature becomes equal to or lower than a predetermined value, steam is supplied to the seawater to make the supplied seawater temperature equal to or higher than the predetermined value.

Conventionally, when the seawater temperature approaches 0 ° C., the flow rate of the supplied LNG is reduced. However, in the present invention, the LNG flow rate is not changed, and the seawater temperature is increased by steam to secure heat of vaporization. This makes it possible to supply a stable amount of LNG gas.

According to a second aspect of the present invention, there is provided an LNG vaporizer for generating LNG gas by spraying seawater into a pipe through which LNG passes, and a seawater line for supplying seawater to the LNG vaporizer, and a seawater line. A steam line connected and having a flow control valve, a thermometer provided downstream of a connection position of the steam line to the seawater line, and the flow control valve connected to the thermometer so that a measured value becomes a predetermined value or more. And a steam amount control device for controlling the pressure.

[0010] A steam line is connected to the seawater line, and a thermometer is provided downstream of the connection position to measure the temperature of the mixed seawater. This temperature is set to a temperature at which icing does not occur in the heat transfer tubes of the LNG vaporizer. The steam amount control device controls the flow rate control valve of the steam line so as to secure this temperature. The temperature to be secured is, for example, 2 to 4 ° C.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an LNG vaporizer according to an embodiment of the present invention. The LNG vaporizer is an LNG vaporizer 1
An LNG supply line 3 for supplying LNG to the LNG vaporizer 1, an LNG gas line 4 for sending LNG gas generated from the LNG vaporizer 1 to a demand location, a seawater line 5 for sending seawater to the LNG vaporizer 1, and seawater. It comprises a steam line 6 for supplying steam to the line 5.

The LNG vaporizer 1 has heat transfer tubes 1a arranged vertically and densely, and a spray header 2 for spraying seawater to the heat transfer tubes 1a is provided at an upper portion thereof. The water spray of the spray header 2 adheres to the upper part of the heat transfer tube 1a, falls along the surface, transfers heat to the internal LNG, gives heat of vaporization, and functions to promote vaporization. A header 1b is provided at a lower portion of the LNG vaporizer 1, and LNG coming from the LNG supply line 3 is uniformly distributed at a lower portion of the vaporizer 1 to each heat transfer tube 1a.
To be supplied. Also, a header 1c is provided at the top of the vaporizer 1 and generated from all the heat transfer tubes 1a.
LNG gas is collected and sent to the LNG gas line 4.

The LNG supply line 3 is provided with a flow control valve 7, a shutoff valve 8, and a flow meter 9. Seawater line 5
Is connected to the spray header 2, the shut-off valve 11 and the thermometer 12
The steam line 6 is connected to the upstream side of the thermometer 12. Thereby, the thermometer 12 measures the temperature after mixing the steam with the seawater. The steam line 6 is provided with a flow control valve 14. The vapor amount control device 13 is connected to the thermometer 12 and controls the temperature so that the measured value of the thermometer 12 becomes a predetermined value, for example, 2 ° C. or 4 ° C. or more. The flow rate controller 10 calculates the amount of heat given to the LNG at approximately minus 162 ° C. by the seawater from the temperature of the seawater after steam mixing and the flow rate of the seawater supplied at a constant amount, and calculates the flow rate of the LNG supplied to the vaporizer 1 Then, the flow control valve 7 is controlled so that the value of the flow meter 9 becomes this flow rate. When the seawater temperature is higher than a predetermined value, naturally, steam is not supplied.

Next, an example of the operation method will be described. The shutoff valve 8 of the LNG supply line 3 and the shutoff valve 11 of the seawater line 5 are closed. The flow control valve 14 of the steam line 6 is restricted to the minimum flow rate. First, the shutoff valve 12 of the seawater line 5 is opened to supply seawater. When the flow rate and the temperature of the seawater are stabilized, the shutoff valve 8 is opened in the LNG supply line 3 with the flow rate control valve 7 at the minimum flow rate. The flow controller 10 calculates the amount of heat provided by the seawater from the temperature of the seawater and the constant flow rate, calculates the amount of LNG vaporized by the amount of heat, and controls the flow control valve 7 so that the measured value of the flowmeter 9 becomes the calculated value. I do. When the temperature of the seawater falls below a predetermined value (usually 2 to 4 ° C.), it appears in the measured value of the thermometer 12.
3 operates and the supply of steam is started.

[0015]

As is apparent from the above description, according to the present invention, the steam line is connected to the seawater line so that the temperature of the seawater supplied to the LNG vaporizer becomes equal to or higher than a predetermined value.
The vaporizer can always be used at full capacity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a conventional LNG vaporizer.

[Explanation of symbols]

 1 LNG vaporizer 2 Spray header 3 LNG supply line 4 LNG gas line 5 Seawater line 6 Steam line 10 Flow controller 13 Steam control device

Claims (2)

[Claims] 1. An LNG vaporization method for generating LNG gas by spraying seawater on a pipe through which LNG passes, wherein steam is supplied to the seawater when the seawater temperature at a vaporizer inlet falls below a predetermined value. LNG vaporization method, wherein the temperature of seawater to be heated is set to a predetermined value or more. 2. An LNG vaporizer for generating LNG gas by spraying seawater on a pipe through which LNG passes.
A seawater line for supplying seawater to the NG vaporizer, a steam line connected to the seawater line and having a flow control valve, a thermometer provided downstream of a position where the steam line is connected to the seawater line, and a thermometer provided with the thermometer. An LNG vaporization device, comprising: a steam flow control device connected to the control unit for controlling the flow control valve so that a measured value is equal to or more than a predetermined value.