JPS6040899A - Method of reliquefying and returning gas in low- temperature liquefied gas carrying ship - Google Patents

Abstract

PURPOSE:To automatically control the level of liquid in the freight tank of a low-temperature liquefied gas carrying ship, by using a control mechanism having received a detection signal of vapor or the like generated in the freight tank, to operate a control valve provided in the branch pipe of a liquid return pipe. CONSTITUTION:Gas flow rate sensors 5 are provided in the branch pipes 3' of a gas intake pipe 3, which communicate with freight tanks 1. Gas quantity detection signals produced through the measuring actions of the sensors 5 are sent to a controller 6 to cumulate the gas flow rates to determine the decreases in the quantities of liquid in the tanks 1 and the total amount of reliquefied gas. When the number of liquid-returned freight tanks is plural, flow rate sensors 7 are provided in the branch pipes 4' of a liquid return pipe 4, which communicate with the freight tanks 1. Detection signals are also sent from the sensors 7 to the controller 6 to cumulate the quantities of liquid returned to the tanks 1, to grasp the quantity of liquid in each tank. Control valves 8 provided in the branch pipes 4' of the liquid return pipe 4 are opened or closed according to instructions from the controller 6 to automatically regulate the quantity of liquid which is to be returned to each freight tank 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reliquefaction in a low-temperature liquefied gas carrier.

Figure 1 shows an example of the reliquefaction flow of a conventional low-temperature liquefied gas carrier. is led from the cargo tank (α) to the reliquefier chamber (C) via the gas suction pipe (h), reliquefied in the same chamber, and then returned to the cargo tank (C) via the liquid return pipe (d).
α).

The liquid re-liquefied in this way is not normally returned to the cargo tank where the gas was generated, but it is preferable that the gas generated from all tanks is re-liquefied and returned to one specific tank within a certain period of time. It is.

Therefore, the reliquefied liquid will flow unevenly into one cargo tank, and there is a risk that it will overflow from the same cargo tank.
It is important to control the return liquid and the liquid level in the cargo tank.

Conventionally, this management method has mainly been to measure the liquid level with a liquid level gauge installed in the tank, and to measure the liquid level with a liquid return pipe (
This is done by opening and closing one control-side valve (g) installed in d).

The disadvantage of this method is that when the ship is at sea, the liquid level in the cargo tank fluctuates, making it difficult to accurately determine the liquid level.

The present invention was proposed in order to eliminate such drawbacks11). Evaporative gas measured by the installed evaporative gas flow rate measurement sensor,
Alternatively, the control mechanism that receives the detection number 41 of the amount of evaporated gas and return liquid operates a control valve disposed in a branch pipe of the liquid return pipe connecting the reliquefaction device and the cargo tank, and This invention relates to a reliquefaction method for a low-temperature liquefied gas carrier whose characteristic is to automatically control the liquid level in the tank.

In the present invention, as mentioned above, the cargo tank of a low-temperature liquefied gas ship and the evaporative gas generated within the tank! An evaporated gas flow rate measuring sensor is installed in the branch pipe of the gas suction pipe in the liquefaction equipment, and the sensor detects the amount of evaporated gas or the amount of evaporated gas and returning liquid going from the tank to the evaporation equipment, and this detection signal is The control device that receives the information operates the control valve installed in the branch pipe of the liquid return pipe that connects the reliquefaction device and the cargo tank, and controls the reliquefied return liquid that returns to the cargo tank. This method is designed to manage the liquid level in the cargo tank, and is more effective than the conventional method by automatically controlling the liquid that returns to the cargo tank without using the liquid level side as in conventional methods. This reduces mistakes, improves safety, and contributes to labor savings in shipboard operations.

The invention will now be explained in detail with reference to the illustrated embodiments.

(1) is a plurality of cargo tanks installed on a low-temperature liquefied gas carrier, and (2) is a reliquefaction device, which is connected to the cargo tanks (], ) via a gas intake pipe (3) and a liquid return pipe (4). The gas generated in the tank (1) was transferred to the gas 19i pipe (3).
The liquid is liquefied in the reliquefier (2) through the liquid return pipe (4).
The structure is such that the tank is flushed and returned to the cargo tank (1).

A gas flow rate measuring sensor (5) is installed in the branch pipe (3') of the gas suction pipe (3) leading to the cargo tank (1), and the gas flow rate measured by the sensor (5) is detected. B. The first issue is sent to the control device (6), and by integrating the gas flow rate, the reduced liquid volume in each cargo tank (1) and the total reliquefied liquid volume are calculated. Here, the lifting platform has only one return cargo tank for the reliquefied liquid, and the liquid amount in each tank is always grasped by the above-mentioned division.

On the other hand, for JJs with multiple liquid return cargo tanks, flow rate sensors (7) are installed in the four branch pipes (4) of the liquid return pipe (4) leading to the cargo tank, and the detection signal from the sensor (7) is By adding up the amount of liquid sent to the control device (6) and returned to each tank (g), the amount of liquid in the main tank (1) is always grasped.

In this way, the amount of liquid returning to the cargo tank (1) can be controlled by opening and closing the control valve (8) provided in the branch pipe (4') of the liquid return pipe (4) by the finger pressure of the control device (6). By doing so, it is automatically controlled.

The present invention will be described below with reference to embodiments; however, the present invention is of course not limited to such embodiments.
The arrangement of the glazes may be modified without departing from the principles of the present invention.

[Brief explanation of drawings]

FIG. 1 is a reliquefaction flow diagram of a conventional low-temperature liquefied gas carrier, and FIG. 2 is a reliquefaction flow diagram of a low-temperature liquefied gas carrier to which the method of the present invention is applied. (1)...Cargo tank, (2)...Reliquefaction device, (
3)...Gas suction pipe, (3')...Branch pipe, (4)
...Liquid return pipe, (4')...Branch pipe, (5)...
Gas flow rate measurement sensor, (6)...control device.

Claims (1)

[Claims] The amount of evaporative gas, or evaporative gas and return liquid, measured by the evaporative gas flow measurement sensor installed in the branch pipe of the gas suction pipe that leads the evaporative gas generated in the multiple cargo tanks of a low-temperature liquefied gas carrier to the ladle liquefaction device. The control mechanism that receives the detection signal operates a control valve installed in a branch pipe of the liquid return pipe connecting the reliquefaction device and the cargo tank, and automatically adjusts the liquid level in the cargo tank. A method for ladle liquefaction return in a low-temperature liquefied gas carrier, which is characterized by controlling.