KR102020970B1 - Boil-Off Gas Reliquefaction System and Method of Discharging Lubrication Oil in the Same, and Method of Supplying Fuel for Engine - Google Patents

Abstract

The boil-off gas is compressed by a first compressor, the compressed boil-off gas is cooled by heat exchange with the boil-off gas before compression in a heat exchanger, and the heat-cooled fluid is decompressed by a first pressure reducing device to reliquefy the boil-off gas. A method of draining lubricant in a system is disclosed.
The lubricating oil discharge method, 1) alarm activation step; And 2) generating the alarm, wherein the first compressor includes at least one oil-filled cylinder, and determines whether to remove condensed or solidified lubricant by the alarm.

Description

Boil-Off Gas Reliquefaction System and Method of Discharging Lubrication Oil in the Same, and Method of Supplying Fuel for Engine}

The present invention relates to a system and method for reliquefying boil-off gas (BOG) generated by natural vaporization of liquefied gas, and in particular, an evaporated gas generated inside a liquefied natural gas (LNG) storage tank. The present invention relates to a system for re-liquefying excess evaporated gas remaining in heavy engines using evaporated gas itself as a refrigerant.

Recently, the consumption of liquefied gas such as liquefied natural gas (Liquefied Natural Gas, LNG) is increasing worldwide. Liquefied gas liquefied gas at low temperature has the advantage that the storage and transport efficiency can be improved because the volume is very small compared to the gas. In addition, liquefied gas, including liquefied natural gas can remove or reduce air pollutants during the liquefaction process, it can be seen as an environmentally friendly fuel with less emissions of air pollutants during combustion.

Liquefied natural gas is a colorless and transparent liquid obtained by liquefying natural gas containing methane as a main component at about -163 ℃ and having a volume of about 1/600 compared to natural gas. Therefore, when liquefied and transported natural gas can be transported very efficiently.

However, since the liquefaction temperature of natural gas is a cryogenic temperature of -163 ℃ at normal pressure, liquefied natural gas is sensitive to temperature changes and easily evaporated. As a result, the storage tank storing the liquefied natural gas is insulated. However, since the external heat is continuously transferred to the storage tank, the natural gas is continuously vaporized in the storage tank during the transport of the liquefied natural gas. -Off Gas, BOG) occurs.

Boil-off gas is a kind of loss and is an important problem in transportation efficiency. In addition, when boil-off gas is accumulated in the storage tank, the internal pressure of the tank may be excessively increased, and there is also a risk that the tank may be damaged. Accordingly, various methods for treating the boil-off gas generated in the storage tank have been studied. In recent years, for the treatment of the boil-off gas, a method of re-liquefying the boil-off gas to return to the storage tank, and returning the boil-off gas to a fuel such as a ship engine The method used as an energy source of a consumer is used.

As a method for reliquefaction of the boil-off gas, a refrigeration cycle using a separate refrigerant is provided to re-liquefy the boil-off gas by exchanging it with the refrigerant, a method of re-liquefying the boil-off gas itself as a refrigerant without a separate refrigerant, and the like. There is this. In particular, a system employing the latter method is called a Partial Re-liquefaction System (PRS).

On the other hand, among the engines generally used in ships as a fuel that can use natural gas as a fuel gas engines such as DFDE, X-DF engine, ME-GI engine.

DFDE is composed of four strokes and adopts the Otto Cycle, which injects natural gas with a relatively low pressure of 6.5 bar into the combustion air inlet and compresses the piston as it rises.

The X-DF engine consists of two strokes, uses about 16 bar of natural gas as fuel, and employs an auto cycle.

The ME-GI engine is composed of two strokes and employs a diesel cycle that directly injects high pressure natural gas near 300 bar into the combustion chamber near the top dead center of the piston.

In this way, in particular, when pressurizing the boil gas (BOG) generated in the LNG storage tank, using the evaporated gas itself as a refrigerant without a separate refrigerant, and re-liquefy the evaporated gas by mutual heat exchange, the reliquefaction efficiency In order to compress the boil-off gas at high pressure, and to compress the boil-off gas at high pressure, a lubricating cylinder compressor should be used.

Lubrication oil is mixed in the boil-off gas compressed by the cylinder type compressor. The inventors of the present invention have found that, while the compressed boil-off gas is cooled in the heat exchanger, the lubricating oil mixed in the compressed boil-off gas is condensed or solidified before the boil-off gas to block the flow path of the heat exchanger. In particular, in the case of narrow passages (e.g., microchannel type passages), PCHEs (also called DCHEs), the passage of the heat exchanger is more frequently blocked by condensation or solidified lubricant. do.

Accordingly, the inventors of the present invention have developed various techniques for separating oil mixed in the compressed boil-off gas in order to prevent or alleviate the phenomenon that condensed or solidified lubricant blocks the flow path of the heat exchanger.

The present invention provides a system that can alleviate or improve the phenomenon that condensed or solidified lubricant blocks the flow path of the heat exchanger, and can remove condensed or solidified lubricant that blocks the heat exchanger flow path in a simple and economical manner. And a method.

According to an aspect of the present invention for achieving the above object, by compressing the boil-off gas by the first compressor, the compressed boil-off gas is cooled by heat exchange in the heat exchanger and the boil-off gas before compression, the heat-cooled fluid CLAIMS 1. A method for depressurizing by a first depressurizing device to discharge lubricating oil in a system for reliquefying boil-off gas, comprising: 1) activating an alarm; And 2) generating the alarm; wherein the first compressor includes at least one oil-filled cylinder and determines by the alarm whether to remove condensed or solidified lubricants. A method of lubricating oil is provided.

In step 1), the alarm may be activated when the system reliquefies the boil-off gas.

In the step 1), it may be determined that the system is re-liquefying the boil-off gas when the opening degree of the first decompression device is equal to or greater than the first set value.

A second decompression device may be installed in parallel with the first decompression device, and in the step 1), when the opening ratio of the first decompression device or the second decompression device is equal to or greater than a first set value, the system may evaporate. It can be determined that the gas is reliquefaction.

The plurality of first pressure reducing devices may be installed in series, and the plurality of second pressure reducing devices may be installed in series, and the plurality of second pressure reducing devices installed in series with the plurality of first pressure reducing devices installed in series. May be connected in parallel, and in the step 1), when the opening ratio of any one of the plurality of first pressure reducing devices or any one of the plurality of second pressure reducing devices is equal to or greater than a first set value, the system may be a boil-off gas. Can be determined to be reliquefaction.

Some or all of the boil-off gas compressed by the first compressor may be used as a fuel of an engine, and excess boil-off gas not used as the fuel of the engine may be liquefied.

A seventh valve may be installed on a line for sending the excess evaporated gas, which is not used as fuel of the engine, out of the boiled gas compressed by the first compressor to the heat exchanger, and in the step 1), the seventh valve is opened. In this case, it can be determined that the system is reliquefying the boil-off gas.

A second compressor may be installed in parallel with the first compressor, and part or all of the boil-off gas compressed by the second compressor is used as fuel of the engine, and excess boil-off gas not used as fuel of the engine is A tenth valve may be installed on a line for sending the excess evaporated gas, which is not used as fuel of the engine, out of the evaporated gas compressed by the second compressor to the heat exchanger, and in step 1), When the seventh valve or the tenth valve is open, it may be determined that the system is reliquefying the boil-off gas.

A gas-liquid separator is installed at the rear end of the first decompression device to separate the liquefied gas re-liquefied by the gas-liquid separator and the evaporated gas remaining in a gaseous state. In step 1), the liquefied gas inside the gas-liquid separator. It can be determined that the system is re-liquefying the boil-off gas when the level of is equal to or greater than the second set value.

A second valve may be installed on a line through which the boil-off gas used as the refrigerant in the heat exchanger is discharged, and in step 1), when the second valve further satisfies the condition of the open state, the system evaporates. It can be determined that the gas is reliquefaction.

In the step 2), the condition that the 'temperature difference of the low temperature flow' of the heat exchanger is more than normal and the state lasts for a predetermined time; A condition in which the 'temperature difference of the high temperature flow' of the heat exchanger is greater than normal and the state lasts for a predetermined time; And a condition in which the 'difference in pressure of the high temperature flow path' of the heat exchanger is greater than normal and the state lasts for a predetermined time; The alarm may be generated when one or more of the conditions are met.

In the step 2), the smaller value of the 'temperature difference of the low temperature flow' of the heat exchanger and the 'temperature difference of the high temperature flow' of the heat exchanger is longer than the third set value or longer than the first set time, or The alarm may be generated when the 'pressure difference in the high temperature flow path' is longer than or equal to the fourth set value and longer than the first set time.

According to another aspect of the present invention for achieving the above object, a first compressor for compressing the boil-off gas; A heat exchanger configured to cool the boil-off gas compressed by the first compressor by using the boil-off gas before being compressed by the first compressor as a refrigerant; A first pressure reducing device installed at a rear end of the heat exchanger to reduce the fluid cooled by the heat exchanger; And a second pressure reducing device installed at a rear end of the heat exchanger to reduce the fluid cooled by the heat exchanger, wherein the first pressure reducing device and the second pressure reducing device are installed in parallel, and the first compressor An evaporative gas reliquefaction system is provided that includes at least one oiled cylinder.

A plurality of first pressure reducing devices may be installed in series, and a plurality of second pressure reducing devices may be installed in series.

An isolation valve may be installed at the front and rear ends of the first pressure reducing device, and an isolation valve may be installed at the front and rear ends of the second pressure reducing device, respectively.

The boil-off gas reliquefaction system may further include a second compressor installed in parallel with the first compressor.

According to another aspect of the present invention for achieving the above object, in the fuel supply method of the engine using the boil-off gas as a fuel in the engine, the excess boil-off gas is re-liquefied, melted condensed or solidified lubricant or lower the viscosity A fuel supply method for an engine is provided, wherein the fuel is supplied to the engine during discharge, and the alarm is used to determine whether to remove condensed or solidified lubricant.

The fuel supply method of the engine comprises the steps of: 1) activating the alarm; And 2) generating the alarm.

In step 1), the alarm may be activated when the boil-off gas is re-liquefied.

In step 2), the condition that the temperature difference of the 'low temperature flow' of the heat exchanger is more than normal and the state lasts for a predetermined time; A condition in which the 'temperature difference of the high temperature flow' of the heat exchanger is greater than normal and the state lasts for a predetermined time; And a condition in which the 'difference in pressure of the high temperature flow path' of the heat exchanger is greater than normal and the state lasts for a predetermined time; The alarm may be generated when one or more of the conditions are met.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the evaporated gas compressed by the compressor by heat exchange using the evaporated gas before being compressed by the compressor as a refrigerant; And a decompression device installed at a rear end of the heat exchanger to depressurize the fluid cooled by the heat exchanger, and installed at a rear end of the first temperature sensor and the high temperature flow path of the heat exchanger. A fourth temperature sensor; A second temperature sensor installed at a rear end of the low temperature flow path of the heat exchanger and a third temperature sensor installed at a front end of the high temperature flow path of the heat exchanger; And a first pressure sensor installed at a front end of the high temperature flow path of the heat exchanger and a second pressure sensor installed at a rear end of the high temperature flow path of the heat exchanger. An evaporative gas reliquefaction system is provided, comprising one or more of the above, wherein the compressor comprises at least one oil-filled cylinder.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the evaporated gas compressed by the compressor by heat exchange using the evaporated gas before being compressed by the compressor as a refrigerant; And a decompression device installed at a rear end of the heat exchanger to depressurize the fluid cooled by the heat exchanger, and installed at a rear end of the first temperature sensor and the high temperature flow path of the heat exchanger. A fourth temperature sensor; A second temperature sensor installed at a rear end of the low temperature flow path of the heat exchanger and a third temperature sensor installed at a front end of the high temperature flow path of the heat exchanger; And a differential pressure sensor for measuring a pressure difference between the front and rear ends of the high temperature flow path of the heat exchanger. An evaporative gas reliquefaction system is provided, comprising one or more of the above, wherein the compressor comprises at least one oil-filled cylinder.

According to another aspect of the present invention for achieving the above object, by compressing the boil-off gas by a compressor, heat exchanged in the heat exchanger with the boil-off gas before the compressed boil-off gas is compressed, the pressure of the fluid cooled by heat exchange In a boil-off gas liquefaction system that is depressurized by a device, the compressor includes at least one oil-filled cylinder, and an boil-off gas re-liquefaction system is provided that detects an abnormality in the performance of the heat exchanger.

According to another aspect of the present invention for achieving the above object, in the method for discharging the lubricating oil in the system to re-liquefy the boil-off gas by using the boil-off gas itself as a refrigerant, evaporation in the heat exchanger at the time of re-liquefied boil-off gas A temperature difference measured by a first temperature sensor installed in front of the low temperature flow path of the heat exchanger and a fourth temperature sensor installed in a rear end of the high temperature flow path of the heat exchanger, by cooling the evaporation gas with the gas itself as a refrigerant; And a smaller value between a temperature measured by a second temperature sensor installed at a rear end of the low temperature flow path of the heat exchanger and a temperature difference measured by a third temperature sensor installed at a front of the high temperature flow path of the heat exchanger. Or a difference between the pressure measured by the first pressure sensor installed at the front of the high temperature flow path of the heat exchanger and the pressure measured by the second pressure sensor installed at the rear end of the high temperature flow path of the heat exchanger. There is provided a lubricating oil discharging method for determining whether or not it is necessary to discharge the oil.

According to another aspect of the present invention for achieving the above object, in the method for discharging the lubricating oil in the system to re-liquefy the boil-off gas by using the boil-off gas itself as a refrigerant, evaporation in the heat exchanger at the time of re-liquefied boil-off gas A temperature difference measured by a first temperature sensor installed in front of the low temperature flow path of the heat exchanger and a fourth temperature sensor installed in a rear end of the high temperature flow path of the heat exchanger, by cooling the evaporation gas with the gas itself as a refrigerant; And a smaller value between a temperature measured by a second temperature sensor installed at a rear end of the low temperature flow path of the heat exchanger and a temperature difference measured by a third temperature sensor installed at a front of the high temperature flow path of the heat exchanger. Or the pressure difference measured by the differential pressure sensor for measuring the pressure difference between the front end and the rear end of the high-temperature flow path of the heat exchanger; as an indicator, to determine whether it is necessary to discharge the condensed or solidified lubricant oil is provided do.

According to another aspect of the present invention for achieving the above object, by compressing the boil-off gas by a compressor, heat exchanged in the heat exchanger with the boil-off gas before the compressed boil-off gas is compressed, the pressure of the fluid cooled by heat exchange A method of discharging lubricating oil in a system for reducing the pressure by means of a device to reliquefy the boil-off gas, wherein the boil-off gas used as the refrigerant in the heat exchanger is supplied to the heat exchanger along a first supply line, and from the heat exchanger to the refrigerant The used boil-off gas is supplied to the compressor along a second supply line, and the boil-off gas before being used as a refrigerant in the heat exchanger can be supplied to the compressor by bypassing the heat exchanger along the bypass line, and on the bypass line Bypass valves for controlling the flow rate and opening and closing of the fluid is provided, the on the first supply line A first valve for controlling the flow and opening and closing of the fluid is installed in front of the exchanger, a second valve for controlling the flow and opening and closing of the fluid is installed at the rear end of the heat exchanger on the second supply line, the compressor is oil-filled cylinder 2) opening the bypass valve and closing the first valve and the second valve; 3) compressing the boil-off gas before being used as a refrigerant in the heat exchanger by the compressor through the bypass line; And 4) sending a part or all of the boil-off gas compressed by the compressor to the heat exchanger, and melting or lowering the viscosity of the lubricating oil condensed or solidified by the boil-off gas compressed by the compressor and having a high temperature. There is provided a lubricating oil discharging method, characterized in that the discharging is performed.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the boil-off gas compressed by the compressor by heat-exchanging the boil-off gas discharged from the storage tank with a refrigerant; A first valve installed on a first supply line for supplying evaporated gas to be used as a refrigerant in the heat exchanger to the heat exchanger, and controlling flow rate and opening / closing of the fluid; A second valve installed on a second supply line for supplying the boil-off gas used as a refrigerant in the heat exchanger to the compressor, for controlling a flow rate and opening / closing of a fluid; A bypass line for bypassing the heat exchanger and supplying boil-off gas to the compressor; And a decompression device installed at a rear end of the heat exchanger to depressurize the fluid cooled by the heat exchanger, wherein the compressor includes at least one oil-filled cylinder, and the bypass line is formed at a front end of the first valve. A boil-off gas reliquefaction system is provided that branches from the first supply line and joins the second supply line after the second valve.

According to another aspect of the present invention for achieving the above object, by compressing the boil-off gas by a compressor, heat exchanged in the heat exchanger with the boil-off gas before the compressed boil-off gas is compressed, the pressure of the fluid cooled by heat exchange A method of discharging lubricating oil in a system to depressurize by means of a device to reliquefy the boil-off gas, the compressor comprising at least one oil-filled cylinder, and passing the boil-off gas through the bypass line to the compressor after bypassing the heat exchanger. By the compressor, and supply the boil-off gas compressed by the compressor to the engine, and supply the remaining boil-off gas supplied to the engine to the heat exchanger, condensed or solidified by the boil-off gas compressed by the compressor and the temperature is high. Lubrication, characterized in that to dissolve the lubricating oil or to lower the viscosity discharged Oil discharge methods are provided.

According to another aspect of the present invention for achieving the above object, in the method for discharging the lubricating oil in the system to re-liquefy the boil-off gas by using the boil-off gas itself as a refrigerant, in the re-liquefied boil-off gas, the heat exchanger is stored The evaporated gas discharged from the tank is used as a refrigerant, and the evaporated gas compressed by the compressor is exchanged and cooled. The compressor includes at least one oil-filled cylinder, and is installed to bypass the heat exchanger to maintain the heat exchanger. By-pass lines used at the time provide a lubricating oil discharging method, which dissolves or lowers the viscosity of the condensed or solidified lubricating oil.

According to another aspect of the present invention for achieving the above object, there is provided a fuel supply method, characterized in that the fuel is supplied to the engine, even during melting or lowering the viscosity of the condensed or solidified lubricant.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the boil-off gas compressed by the compressor by heat-exchanging the boil-off gas before being compressed by the compressor with a refrigerant; A pressure reducing device installed at a rear end of the heat exchanger to reduce the pressure of the fluid cooled by the heat exchanger; And a gas-liquid separator installed at a rear end of the decompression device to separate the liquefied liquefied gas and the evaporated gas remaining in the gas state, wherein the compressor includes at least one refueling cylinder, and the gas-liquid separator includes: An evaporative gas reliquefaction system is provided, to which a lubricating oil discharge line for discharging lubricating oil collected inside the gas-liquid separator is connected.

According to another aspect of the present invention for achieving the above object, in the method for discharging the lubricating oil in the system to re-liquefy the boil-off gas using the evaporation gas itself as a refrigerant, the lubricating oil discharged in the gas-liquid separator It is discharged from the gas-liquid separator through, and the lubricating oil discharge line is provided separately from the fifth supply line for discharging the liquefied liquefied gas from the gas-liquid separator at the time of re-liquefaction of the boil-off gas is provided, .

According to another aspect of the present invention for achieving the above object, by compressing the boil-off gas by a compressor, heat exchanged in the heat exchanger with the boil-off gas before the compressed boil-off gas is compressed, the pressure of the fluid cooled by heat exchange A method of discharging lubricating oil in a system to depressurize by means of a device to reliquefy the boil-off gas, the compressor comprising at least one oil-filled cylinder, wherein the compressor at the heat exchanger front end of the boil-off gas used as refrigerant in the heat exchanger. A condition in which a temperature of and a temperature difference of the boil-off gas cooled by the heat exchanger after being compressed by the compressor (hereinafter, referred to as a 'temperature difference of low temperature flow') is equal to or greater than a first set value are maintained for a predetermined time or more; The temperature difference between the temperature of the boil-off gas used as the refrigerant in the heat exchanger and the boil-off gas sent to the heat exchanger after being compressed by the compressor (hereinafter, referred to as 'temperature difference of high temperature flow') is equal to or greater than the first set value. A condition in which the state lasts for a predetermined time; And a pressure difference at the front end of the heat exchanger of the boil-off gas sent to the heat exchanger after being compressed by the compressor and a pressure difference at the rear end of the heat exchanger of the boil-off gas cooled by the heat exchanger The condition that the difference is greater than or equal to the second set value; If one or more of the above is satisfied, a lubricating oil discharging method is provided that determines that it is a 'time to discharge condensed or solidified lubricating oil'.

According to another aspect of the present invention for achieving the above object, by compressing the boil-off gas by a compressor, heat exchanged in the heat exchanger with the boil-off gas before the compressed boil-off gas is compressed, the pressure of the fluid cooled by heat exchange A method of discharging lubricating oil in a system to depressurize by means of a device to reliquefy the boil-off gas, the compressor comprising at least one oil-filled cylinder, wherein the compressor at the heat exchanger front end of the boil-off gas used as refrigerant in the heat exchanger. The temperature difference between the temperature of and the boil-off gas cooled by the heat exchanger after being compressed by the compressor (hereinafter, referred to as 'temperature difference of low temperature flow'); And a temperature difference between the temperature of the boil-off gas used as the refrigerant in the heat exchanger and the boil-off gas sent to the heat exchanger after being compressed by the compressor (hereinafter, referred to as a 'temperature difference in high temperature flow'). The pressure at the front end of the heat exchanger of the boil-off gas sent to the heat exchanger after being compressed by the compressor or after being compressed by the compressor, If the pressure difference at the rear end of the heat exchanger (hereinafter, referred to as a 'pressure difference in the high temperature flow path') is greater than or equal to the second set value for more than a predetermined time, it is determined that it is a time to discharge the condensed or solidified lubricant. The lubricating oil discharge method is provided.

According to another aspect of the present invention for achieving the above object, in the method for discharging the lubricating oil in the system to re-liquefy the boil-off gas using the boil-off gas itself as a refrigerant, at least one of the temperature difference and the pressure difference of the equipment A lubricating oil discharging method is provided, characterized by finding out a 'time to discharge condensed or solidified lubricant' as an indicator and notifying the 'time to discharge the condensed or solidified lubricant' by an alarm.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas, heat exchange for cooling by heat-exchanging by using the boil-off gas before compressing the boil-off gas compressed by the compressor by the compressor as a refrigerant And a decompression device for reducing the fluid cooled by the heat exchanger, the evaporative gas reliquefaction system comprising: at least one of a front end and a rear end of the heat exchanger to detect whether the heat exchanger is blocked by lubricating oil. Sensing means; And an alarm informing the phenomenon that the heat exchanger detected by the sensing means is blocked by the lubricating oil. A boil-off gas reliquefaction system is provided.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the evaporated gas compressed by the compressor by heat exchange using the evaporated gas before being compressed by the compressor as a refrigerant; A pressure reducing device installed at a rear end of the heat exchanger to reduce the pressure of the fluid cooled by the heat exchanger; And a second oil filter installed at a rear end of the decompression device, wherein the compressor includes at least one oil-filled cylinder, and the second oil filter is for cryogenic use.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the evaporated gas compressed by the compressor by heat exchange using the evaporated gas before being compressed by the compressor as a refrigerant; A pressure reducing device installed at a rear end of the heat exchanger to reduce the pressure of the fluid cooled by the heat exchanger; A gas-liquid separator installed at the rear of the decompression device to separate the liquefied liquefied gas and the evaporated gas remaining in the gas state; And a second oil filter installed on a fifth supply line through which the liquefied gas separated by the gas-liquid separator is discharged, wherein the compressor includes at least one oil-filled cylinder, and the second oil filter is cryogenic. Tolerant, boil-off gas reliquefaction system is provided.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the evaporated gas compressed by the compressor by heat exchange using the evaporated gas before being compressed by the compressor as a refrigerant; A pressure reducing device installed at a rear end of the heat exchanger to reduce the pressure of the fluid cooled by the heat exchanger; A gas-liquid separator installed at the rear of the decompression device to separate the liquefied liquefied gas and the evaporated gas remaining in the gas state; And a second oil filter installed on a sixth supply line through which the vaporized gaseous gas separated by the gas-liquid separator is discharged, wherein the compressor includes at least one oil-filled cylinder and the second oil. The filter is provided with an evaporative gas reliquefaction system, for cryogenic use.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the evaporated gas compressed by the compressor by heat exchange using the evaporated gas before being compressed by the compressor as a refrigerant; A pressure reducing device installed at a rear end of the heat exchanger to reduce the pressure of the fluid cooled by the heat exchanger; A bypass line for supplying evaporated gas to be used as a refrigerant in the heat exchanger to the compressor by bypassing the heat exchanger in front of the heat exchanger; And a bypass valve installed on the bypass line to control the flow rate and opening / closing of the fluid. When the pressure of the boil-off gas supplied to the compressor is lower than a suction pressure condition required by the compressor, the bypass valve is An evaporative gas reliquefaction system is provided, which is partially or fully open.

According to another aspect of the present invention for achieving the above object, by compressing the boil-off gas by a compressor, heat exchanged in the heat exchanger with the boil-off gas before the compressed boil-off gas is compressed, the pressure of the fluid cooled by heat exchange A method of supplying fuel to an engine of a system for depressurizing by an apparatus to reliquefy boil gas, wherein the pressure of the boil gas supplied to the compressor is supplied to the compressor when the pressure of the boil gas is lower than a suction pressure condition required by the compressor. A fuel supply method is provided for bypassing the heat exchanger to supply some or all of the boil-off gas to the compressor.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the boil-off gas compressed by the compressor by heat-exchanging the boil-off gas before being compressed by the compressor with a refrigerant; A bypass line for bypassing the heat exchanger and supplying boil-off gas to the compressor; A second valve installed on a second supply line for sending the boil-off gas used as a refrigerant in the heat exchanger to the compressor to regulate flow rate and opening / closing of the fluid; And a decompression device installed at a rear end of the heat exchanger to depressurize the fluid cooled by the heat exchanger, wherein the compressor includes at least one oil-filled cylinder, and the bypass line is formed at a rear end of the second valve. An evaporated gas reliquefaction system is provided that joins the second supply line.

According to another aspect of the present invention for achieving the above object, by compressing the boil-off gas by a compressor, heat exchanged in the heat exchanger with the boil-off gas before the compressed boil-off gas is compressed, the pressure of the fluid cooled by heat exchange A method for discharging lubricating oil in a system to depressurize by means of a device to reliquefy the boil-off gas, the compressor comprising at least one oil-filled cylinder and sending the boil-off gas used as a refrigerant in the heat exchanger to the compressor. On the second supply line, a second valve for controlling the flow rate and opening and closing of the fluid is installed, and the evaporated gas is bypassed by the compressor after bypassing the heat exchanger through a bypass line, and the surplus evaporated gas remaining after supplying to the engine is Supplied to a heat exchanger, compressed by the compressor, and Sikimyeo discharge melt tarred lubricant, wherein the bypass line, wherein the, lubricant outlet method for joining the second and the second supply line of the rear end of the valve is provided.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the boil-off gas compressed by the compressor by heat-exchanging the boil-off gas before being compressed by the compressor with a refrigerant; A bypass line for bypassing the heat exchanger and supplying boil-off gas to the compressor; A first valve installed on a first supply line for supplying evaporated gas to be used as a refrigerant in the heat exchanger to the heat exchanger to control flow and opening and closing of the fluid; And a decompression device installed at a rear end of the heat exchanger to depressurize the fluid cooled by the heat exchanger, wherein the compressor includes at least one oil-filled cylinder, and the bypass line is formed at a front end of the first valve. An evaporative gas reliquefaction system is provided, branching from the first supply line.

According to another aspect of the present invention for achieving the above object, a compressor for compressing the boil-off gas; A heat exchanger for cooling the boil-off gas compressed by the compressor by heat-exchanging the boil-off gas before being compressed by the compressor with a refrigerant; A bypass line branching from the first supply line for supplying the refrigerant in the heat exchanger to the first heat exchanger and bypassing the heat exchanger to the compressor; A pressure reducing device installed at a rear end of the heat exchanger to reduce the pressure of the fluid cooled by the heat exchanger; And a gas-liquid separator installed at a rear end of the decompression device and separating the liquefied liquefied gas and the boil-off gas remaining in a gaseous state, wherein the compressor includes at least one oil-filled cylinder. The separated gaseous boil-off gas is discharged from the gas-liquid separator along a sixth supply line, and the sixth supply line is joined to the first supply line at a point preceding the branch where the bypass line branches. This is provided.

According to the present invention, it is possible to simply and economically remove condensed or solidified lubricating oil inside the heat exchanger using only existing equipment without installing additional equipment or supplying a separate fluid for lubricating oil removal.

According to the present invention, the heat exchanger can be maintained while driving the engine while the internal condensed or solidified lubricant is removed. In addition, it is possible to remove the condensed or solidified lubricating oil by using the excess boil-off gas used in the engine. In addition, there is an advantage that the lubricating oil mixed in the boil-off gas can be burned by the engine.

According to the present invention, by using the improved gas-liquid separator, there is an advantage that the melted or low viscosity lubricant oil collected in the gas-liquid separator can be efficiently discharged.

According to the present invention, the cryogenic oil filter is installed in at least one of the rear end of the decompression device, the fifth supply line through which the liquefied gas is discharged from the gas-liquid separator, and the sixth supply line through which the evaporated gas is discharged from the gas-liquid separator. The advantage is that the mixed lubricant can be effectively removed.

According to the present invention, it is possible to simply and economically use only existing equipment without installing additional equipment, while maintaining the reliquefaction performance while satisfying the suction pressure condition required by the compressor, and satisfying the fuel consumption required by the engine. Can be.

1 is a schematic diagram of a boil-off gas reliquefaction system according to a first preferred embodiment of the present invention.
2 is a schematic diagram of a boil-off gas reliquefaction system according to a second preferred embodiment of the present invention.
3 is a schematic diagram of a boil-off gas reliquefaction system according to a third preferred embodiment of the present invention.
4 is an enlarged view of a gas-liquid separator according to an embodiment of the present invention.
5 is an enlarged view of a second oil filter according to an embodiment of the present invention.
6 is an enlarged view of a second oil filter according to another embodiment of the present invention.
7 is a schematic diagram of a boil-off gas reliquefaction system according to a fourth preferred embodiment of the present invention.
8 is an enlarged view of a pressure reducing device according to an embodiment of the present invention.
9 is an enlarged view of a pressure reducing device according to another embodiment of the present invention.
10 is an enlarged view of a heat exchanger and a gas-liquid separator according to an embodiment of the present invention.
11 and 12 are graphs showing the amount of reliquefaction according to the boil-off gas pressure in a Partial Re-liquefaction System (PRS).
FIG. 13 is a plan view of the filter element illustrated in FIGS. 5 and 6.

Hereinafter, the configuration and operation of the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. The boil-off gas reliquefaction system of the present invention can be applied to various applications such as a ship equipped with an engine using natural gas as a fuel, a ship or a marine structure including a liquefied gas storage tank. In addition, the following examples may be modified in many different forms, and the scope of the present invention is not limited to the following examples.

In addition, the fluid in each line of the present invention may be in any one of a liquid state, a gas-liquid mixed state, a gas state, and a supercritical fluid state, depending on the operating conditions of the system.

1 is a schematic diagram of a boil-off gas reliquefaction system according to a first preferred embodiment of the present invention.

Referring to FIG. 1, the boil-off gas reliquefaction system of this embodiment includes a compressor 200, a heat exchanger 100, a pressure reducing device 600, a bypass line BL, and a bypass valve 590.

The compressor 200 compresses the boil-off gas discharged from the storage tank T, and the plurality of cylinders 210, 220, 230, 240, 250 and the plurality of coolers 211, 221, 231, 241, 251 are compressed. It may include. The pressure of the boil-off gas compressed by the compressor 200 may be approximately 150 to 350 bar.

The boil-off gas compressed by the compressor 200 may be partly sent to the main engine propelling the ship along the fuel supply line SL, and the remaining boil-off gas not required by the main engine is the third supply line L3. Accordingly, it may be sent to the heat exchanger 100 to undergo a reliquefaction process. The main engine may be a ME-GI engine using high pressure natural gas as a fuel having a pressure of approximately 300 bar.

The boil-off gas that has passed through only some of the cylinders 210 and 220 included in the compressor 200 may be partially branched and sent to the generator. The generator of this embodiment may be a DF engine using low pressure natural gas as a fuel having a pressure of approximately 6.5 bar.

The heat exchanger 100 uses the evaporated gas discharged from the storage tank T supplied along the first supply line L1 as a refrigerant and supplies it to the compressor 200 supplied along the third supply line L3. The compressed boil-off gas is cooled by heat exchange. The boil-off gas used as the refrigerant in the heat exchanger 100 is supplied to the compressor 200 along the second supply line L2, and the fluid cooled in the heat exchanger 100 is decompressed along the fourth supply line L4. Supplied to the device 600.

The decompression device 600 depressurizes the boil-off gas cooled by the heat exchanger 100 after being compressed by the compressor 200. The evaporated gas that has undergone the compression process by the compressor 200, the cooling process by the heat exchanger 100, and the pressure reduction process by the decompression device 600 is partially or completely reliquefied. The pressure reduction device 600 may be an expansion valve such as a Joule-Thompson valve, or may be an expander.

The boil-off gas reliquefaction system of this embodiment is installed at the rear end of the decompression device 600, and passes through the compressor 200, the heat exchanger 100, and the decompression device 600, and liquefied liquefied natural gas and gaseous state. It may further include a gas-liquid separator 700 for separating the remaining boil-off gas.

The liquefied gas separated by the gas-liquid separator 700 is sent to the storage tank T along the fifth supply line L5, and the evaporated gas separated by the gas-liquid separator 700 is discharged from the storage tank T. Joined with the boil-off gas may be sent to the heat exchanger (100).

A ninth valve 582 may be installed on the sixth supply line L6 through which the vaporized gaseous gas is discharged from the gas-liquid separator 700 to control the flow rate and opening and closing of the fluid.

When the heat exchanger 100 is not available, such as when the heat exchanger 100 is being maintained or the heat exchanger 100 is broken, the evaporated gas discharged from the storage tank T is bypassed (BL). Through the heat exchanger 100 can be bypassed. On the bypass line BL, a bypass valve 590 for opening and closing the bypass line BL is provided.

2 is a schematic diagram of a boil-off gas reliquefaction system according to a second preferred embodiment of the present invention.

Referring to FIG. 2, the boil-off gas reliquefaction system of the present embodiment includes a heat exchanger 100, a first valve 510, a second valve 520, a first temperature sensor 810, and a second temperature sensor 820. ), The compressor 200, the third temperature sensor 830, the fourth temperature sensor 840, the first pressure sensor 910, the second pressure sensor 920, the pressure reducing device 600, the bypass line BL. , And a bypass valve 590.

The heat exchanger 100 exchanges and cools the boil-off gas compressed by the compressor 200 using the boil-off gas discharged from the storage tank T as a refrigerant. After being discharged from the storage tank (T), the boil-off gas used as the refrigerant in the heat exchanger (100) is sent to the compressor (200), and the boil-off gas compressed by the compressor (200) is discharged from the storage tank (T). It is cooled by the heat exchanger 100 using the evaporated gas as a refrigerant.

The boil-off gas discharged from the storage tank T is sent to the heat exchanger 100 along the first supply line L1 and used as a refrigerant, and the boil-off gas used as the refrigerant in the heat exchanger 100 is the second supply line L2. Is sent to the compressor 200. Some or all of the boil-off gas compressed by the compressor 200 is sent to the heat exchanger 100 along the third supply line L3 to be cooled, and the fluid cooled in the heat exchanger 100 is supplied to the fourth supply line L4. Is sent to the decompression device 600.

The first valve 510 is installed on the first supply line (L1) to control the flow rate and opening and closing of the fluid, the second valve 520 is installed on the second supply line (L2) to flow and open and close the fluid Adjust

The first temperature sensor 810 is installed in front of the heat exchanger 100 on the first supply line L1 and measures the temperature of the boil-off gas discharged from the storage tank T and supplied to the heat exchanger 100. The first temperature sensor 810 is preferably installed immediately in front of the heat exchanger 100 so that the temperature of the evaporated gas immediately before being supplied to the heat exchanger 100 can be measured.

In the present invention, the front end includes the meaning upstream, and the rear end includes the downstream meaning.

The second temperature sensor 820 is installed at the rear end of the heat exchanger 100 on the second supply line L2, and discharged from the storage tank T to determine the temperature of the boil-off gas used as the refrigerant in the heat exchanger 100. Measure The second temperature sensor 820 is preferably installed immediately after the heat exchanger 100 so that the temperature of the evaporated gas immediately after being used as the refrigerant in the heat exchanger 100 can be measured.

The compressor 200 compresses the boil-off gas used as the refrigerant in the heat exchanger 100 after being discharged from the storage tank T. The boil-off gas compressed by the compressor 200 may be supplied as fuel of the high-pressure engine, and the surplus boil-off gas remaining after being supplied as the fuel of the high-pressure engine may be sent to the heat exchanger 100 to undergo a reliquefaction process.

On the fuel supply line SL which sends the boil-off gas compressed by the compressor 200 to the high pressure engine, a sixth valve 560 may be installed to control the flow rate and opening / closing of the fluid.

The sixth valve 560 serves as a safety device that completely blocks the supply of the boil-off gas sent to the high pressure engine when the gas mode operation of the high pressure engine is stopped. The gas mode refers to a mode in which an engine is operated by using natural gas as a fuel. When there is not enough boil-off gas to be used as fuel, the engine is switched to a fuel oil mode, and the fuel oil is used as a fuel of the engine.

In addition, the seventh valve 570 that controls the flow rate and opening and closing of the fluid on the line for sending the excess evaporated gas remaining after being supplied as fuel of the high-pressure engine of the boil-off gas compressed by the compressor 200 to the heat exchanger 100. Can be installed.

When the boil-off gas compressed by the compressor 200 is sent to the high-pressure engine, the compressor 200 may compress the boil-off gas to a pressure required by the high-pressure engine. The high pressure engine may be a ME-GI engine using high pressure evaporated gas as fuel.

ME-GI engines are known to use about 150 to 400 bar, preferably about 150 to 350 bar, more preferably about 300 bar of natural gas as fuel. The compressor 200 of the present invention may compress the boil-off gas to approximately 150 to 350 bar to supply the compressed boil-off gas to the ME-GI engine.

In the present invention, instead of the ME-GI engine, an X-DF engine or a DF engine using an evaporation gas of about 6 to 20 bar pressure as a fuel may be used. In this case, the engine is compressed to supply the main engine. Since the boil-off gas is low pressure, the compressed boil-off gas may be further pressurized to be reliquefied to be supplied to the main engine. The pressure of the further pressurized boil-off gas for reliquefaction may be approximately 80 to 250 bar.

11 and 12 are graphs showing the amount of reliquefaction according to the boil-off gas pressure in a Partial Re-liquefaction System (PRS). The boil-off gas to be reliquefed means an boil-off gas that is cooled and re-liquefied and named to distinguish it from the boil-off gas used as a refrigerant.

11 and 12, it can be seen that the reliquefaction amount shows a maximum value when the pressure of the boil-off gas is around 150 to 170 bar, and there is little change in the amount of liquefaction between 150 and 300 bar. Therefore, when the ME-GI engine using a boil-off gas of about 150 to 350 bar (mainly 300 bar) as the fuel is a high pressure engine, the reliquefaction system can be easily supplied to supply the fuel to the high pressure engine while maintaining a high reliquefaction amount. The advantage is that it can be controlled.

The compressor 200 includes a plurality of cylinders 210, 220, 230, 240, and 250, and a plurality of coolers 211, 221, 231, respectively installed at rear ends of the plurality of cylinders 210, 220, 230, 240, and 250. 241, 251). The coolers 211, 221, 231, 241 and 251 are compressed by the cylinders 210, 220, 230, 240 and 250 and cool the boil-off gas whose temperature as well as the pressure is increased.

When the compressor 200 includes a plurality of cylinders 210, 220, 230, 240 and 250, the boil-off gas supplied to the compressor 200 may be provided by the plurality of cylinders 210, 220, 230, 240 and 250. Compressed in multiple stages. Each cylinder 210, 220, 230, 240, 250 may have the meaning of each compression stage of the compressor 200.

In addition, the compressor 200 may include: a first recirculation line RC1 for sending a part or all of the boil-off gas passed through the first cylinder 210 and the first cooler 211 to the front end of the first cylinder 210; A second recirculation line RC2 which sends a part or all of the boil-off gas passed through the second cylinder 220 and the second cooler 221 to the front end of the second cylinder 220; A third recirculation line RC3 which sends a part or all of the boil-off gas passed through the third cylinder 230 and the third cooler 231 to the front end of the third cylinder 230; And a fourth recirculation which sends a part or all of the boil-off gas passed through the fourth cylinder 240, the fourth cooler 241, the fifth cylinder 250, and the fifth cooler 251 to the front end of the fourth cylinder 240. It may include a line RC4.

In addition, a first recirculation valve 541 is installed on the first recirculation line RC1 to control the flow rate and opening and closing of the fluid, and a second recirculation valve controlling the flow rate and opening and closing of the fluid is provided on the second recirculation line RC2. 542 is installed, a third recirculation valve 543 is installed on the third recirculation line (RC3) for adjusting the flow rate and opening and closing of the fluid, and the fourth recirculating line (RC4) is a third controlling the flow rate and opening and closing of the fluid Four recirculation valves 544 may be installed.

The recirculation lines RC1, RC2, RC3, and RC4 recirculate some or all of the boil-off gas when the suction pressure condition required by the compressor 200 is not satisfied because the internal pressure of the storage tank T is low. Protect. When the recirculation lines RC1, RC2, RC3, and RC4 are not used, the recirculation valves 541, 542, 543, and 544 are closed, and the suction pressure condition required by the compressor 200 is not satisfied. Open the recirculation valves 541, 542, 543 and 544 if it is necessary to use.

FIG. 2 illustrates a case in which the boil-off gas passing through all the cylinders 210, 220, 230, 240, and 250 included in the compressor 200 is sent to the heat exchanger 100. The boil-off gas passing through some of the cylinders 210, 220, 230, 240, and 250 may be branched in the middle of the compressor 200 and sent to the heat exchanger 100.

In addition, the boil-off gas passing through some of the plurality of cylinders (210, 220, 230, 240, 250) can be branched in the middle of the compressor 200 to be sent to the low-pressure engine to be used as fuel, and the excess boil-off gas is a gas combustion device ( It can also be sent to the GCU (Gas Combustion Unit) for combustion.

The low pressure engine may be a DF engine (eg DFDE) that uses boil-off gas at about 6 to 10 bar pressure as fuel.

The plurality of cylinders 210, 220, 230, 240, and 250 included in the compressor 200 may operate in an oil-free lubricated manner and some in an oil lubricated manner. have. In particular, in order to use the boil-off gas compressed by the compressor 200 as a fuel of a high-pressure engine, or to compress the boil-off gas to 80 bar or more, preferably 100 bar or more for reliquefaction efficiency, the compressor 200 In order to compress the boil-off gas to a high pressure it will include a lubrication type cylinder.

In the existing technology, lubricating oil for lubrication and cooling must be supplied to the reciprocating compressor 200, for example, to the piston sealing portion, in order to compress the boil-off gas to 100 bar or more.

Lubricating oil is supplied to the cylinder with oil lubrication. In the current state of the art, some of the lubricant is mixed with the boil-off gas passing through the oil lubrication cylinder. The inventors of the present invention have found that the lubricating oil mixed with the boil-off gas is compressed before the boil-off gas is condensed or solidified in the heat-exchanger 100 to block the flow path of the heat-exchanger 100.

The boil-off gas reliquefaction system of the present embodiment may further include an oil separator 300 and a first oil filter 410 installed between the compressor 200 and the heat exchanger 100 to separate oil mixed in the boil-off gas. have.

The oil separator 300 mainly separates lubricating oil in a liquid state, and the first oil filter 410 separates lubricating oil in a vapor state or a mist state. Since the oil separator 300 separates lubricating oil having a larger particle size than the first oil filter 410, the oil separator 300 is installed at the front end of the first oil filter 410 and is compressed by the compressor 200. Gas is preferably passed through the oil separator 300 and the first oil filter 410 in order to be sent to the heat exchanger (100).

2 illustrates a case in which both the oil separator 300 and the first oil filter 410 are included, the evaporation gas reliquefaction system of the present embodiment includes any of the oil separator 300 and the first oil filter 410. It may contain only one. However, it is preferable to use both the oil separator 300 and the first oil filter 410.

In addition, FIG. 2 illustrates a case in which the first oil filter 410 is installed on the second supply line L2 at the rear end of the compressor 200, but the first oil filter 410 is front of the heat exchanger 100. It may be installed on the third supply line (L3), a plurality of may be installed in parallel.

The boil-off gas reliquefaction system of this embodiment includes at least one of an oil separator 300 and a first oil filter 410, and the compressor 200 of this embodiment includes an oil-free lubrication type cylinder and an oil-lubrication lubrication type cylinder. In this case, the boil-off gas passing through the oil-lubricated lubrication cylinder is configured to be sent to the oil separator 300 and / or the first oil filter 410, and the boil-off gas passing only the oil-free lubrication cylinder is the oil separator 300. Or directly to the heat exchanger 100 without passing through the oil filter 410.

As an example, the compressor 200 of the present embodiment includes five cylinders 210, 220, 230, 240, and 250, and the three front cylinders 210, 220, and 230 are oil-free lubricated and the rear two cylinders 240. , 250 may be a lubrication type of lubrication. When branching the boil-off gas in three stages or less, the boil-off gas is sent directly to the heat exchanger 100 without passing through the oil separator 300 or the first oil filter 410. When the boil-off gas is branched at four or more stages, the boil-off gas may be sent to the first heat exchanger 100 after passing through the oil separator 300 and / or the first oil filter 410.

The first oil filter 410 may be an oil filter of a coalescer type.

The non-return valve 550 may be installed on the fuel supply line SL between the compressor 200 and the high pressure engine. The non-return valve 550 serves to prevent damage to the compressor due to backflow of the boil-off gas when the high pressure engine is stopped.

When the boil-off gas reliquefaction system of the present embodiment includes an oil separator 300 and / or a first oil filter 410, the countercurrent boil-off gas is transferred to the oil separator 300 and / or the first oil filter 410. In order not to flow, the non-return valve 550 may be installed at the rear of the oil separator 300 and / or the first oil filter 410.

In addition, since the evaporation gas may flow backward to damage the compressor 200 even when the expansion valve 600 is suddenly closed, the backflow prevention valve 550 may include a third supply line L3 and a fuel supply line SL. It is preferable that it is provided at the front end of the branch point branching from)

The third temperature sensor 830 is installed in front of the heat exchanger 100 on the third supply line L3 to measure the temperature of the boil-off gas that is compressed by the compressor 200 and then sent to the heat exchanger 100. do. The third temperature sensor 830 is preferably installed immediately in front of the heat exchanger 100 so that the temperature of the evaporated gas immediately before being supplied to the heat exchanger 100 can be measured.

The fourth temperature sensor 840 is installed at the rear end of the heat exchanger 100 on the fourth supply line L4, and compressed by the compressor 200 to adjust the temperature of the boil-off gas cooled by the heat exchanger 100. Measure The fourth temperature sensor 840 is preferably installed immediately after the heat exchanger 100 so that the temperature of the boil-off gas immediately after being cooled by the heat exchanger 100 can be measured.

The first pressure sensor 910 is installed in front of the heat exchanger 100 on the third supply line L3 and measures the pressure of the boil-off gas sent to the heat exchanger 100 after being compressed by the compressor 200. do. The first pressure sensor 910 is preferably installed immediately in front of the heat exchanger 100 so that the pressure of the boil-off gas immediately before being supplied to the heat exchanger 100 can be measured.

The second pressure sensor 920 is installed at the rear end of the heat exchanger 100 on the fourth supply line L4 to compress the pressure of the boil-off gas cooled by the heat exchanger 100 after being compressed by the compressor 200. Measure The second pressure sensor 920 is preferably installed immediately after the heat exchanger 100 so that the pressure of the boil-off gas immediately after being cooled by the heat exchanger 100 can be measured.

As shown in FIG. 2, it is preferable that all of the first to fourth temperature sensors 810 to 840, the first pressure sensor 910, and the second pressure sensor 920 are installed, but the present embodiment is limited thereto. The first temperature sensor 810 and the fourth temperature sensor 840 (hereinafter, referred to as a 'first pair') may be installed, or the second temperature sensor 820 and the third temperature sensor may be installed. 830 (hereinafter, referred to as a 'second pair') only, or a first pressure sensor 910 and a second pressure sensor 920 (hereinafter referred to as a 'third pair') only, Only two pairs of the first to third pairs may be installed.

The decompression device 600 is installed at the rear end of the heat exchanger 100, and decompresses the boil-off gas cooled by the heat exchanger 100 after being compressed by the compressor 200. The evaporated gas that has undergone the compression process by the compressor 200, the cooling process by the heat exchanger 100, and the pressure reduction process by the decompression device 600 is partially or completely reliquefied. The pressure reducing device 600 may be an expansion valve such as a Joule-Thompson valve or an expander depending on the configuration of the system.

The boil-off gas reliquefaction system of this embodiment is installed at the rear end of the decompression device 600, and passes through the compressor 200, the heat exchanger 100, and the decompression device 600, and liquefied liquefied natural gas and gaseous state. It may further include a gas-liquid separator 700 for separating the remaining boil-off gas.

The liquefied gas separated by the gas-liquid separator 700 is sent to the storage tank T along the fifth supply line (L5), and the boil-off gas separated by the gas-liquid separator 700 passes the sixth supply line (L6). Accordingly, after joining with the boil-off gas discharged from the storage tank (T) may be sent to the heat exchanger (100).

2 shows that the boil-off gas separated by the gas-liquid separator 700 is joined to the boil-off gas discharged from the storage tank T and then sent to the heat exchanger 100, but is not limited thereto. The gas 100 is composed of three flow paths and the evaporated gas separated in the gas-liquid separator 700 may be used as a refrigerant in the heat exchanger 100 along a separate flow path.

In addition, the liquid may be sent directly to the storage tank (T), which does not include the gas-liquid separator 700 and is partially or entirely re-liquefied by the decompression device 600.

An eighth valve 581 may be installed on the fifth supply line L5 to open and close the flow rate of the fluid. The level of the liquefied gas inside the gas-liquid separator 700 is adjusted by the eighth valve 581.

A ninth valve 582 may be installed on the sixth supply line L6 to adjust the flow rate and opening and closing of the fluid. The internal pressure of the gas-liquid separator 700 is adjusted by the ninth valve 582.

Figure 4 is an enlarged view of the gas-liquid separator according to an embodiment of the present invention, as shown in Figure 4, the gas-liquid separator 700 is installed at least one level sensor 940 for measuring the level of the internal liquefied gas Can be.

The boil-off gas reliquefaction system of this embodiment includes a second oil filter 420 which is installed between the sensitization device 600 and the gas-liquid separator 700 to filter the oil mixed in the pressure-reduced fluid by the pressure reduction device 600. It may include.

2 and 4, the second oil filter 420 may be installed on the fourth supply line L4 between the pressure reducing device 600 and the gas-liquid separator 700 (A position in FIG. 4). ), May be installed on the fifth supply line (L5) for liquefied liquefied gas is discharged from the gas-liquid separator 700 (B position in Figure 4), the gaseous evaporated gas is discharged from the gas-liquid separator 700 It may be installed on the sixth supply line (L6) to be (C position of FIG. 4). 2 illustrates a case in which the second oil filter 420 is installed at the A position of FIG. 4.

The gaseous evaporated gas separated by the gas-liquid separator 700 may be combined with the evaporated gas discharged from the storage tank T and supplied to the low-temperature flow path of the heat exchanger 100. Since it is collected, it is not possible to exclude the possibility that even a small amount of lubricating oil is mixed in the gaseous evaporated gas separated by the gas-liquid separator 700.

The inventors of the present invention, when the lubricating oil is mixed with the gaseous evaporated gas separated by the gas-liquid separator 700 and sent to the low-temperature flow path of the heat exchanger 100, the lubricating oil compressed by the compressor 200 and mixed with the evaporated gas is It has been found that a more difficult situation may occur than if it is fed into the hot passage of the heat exchanger 100.

Since the fluid used as the refrigerant in the heat exchanger 100 is supplied to the low-temperature flow path of the heat exchanger 100, the cryogenic evaporation gas is supplied throughout the operation of the system and high enough to melt the condensed or solidified oil. No fluid with temperature is supplied. Therefore, it is very difficult to remove condensed or solidified oil accumulated in the low temperature flow path of the heat exchanger 100.

In order to minimize the possibility that the lubricating oil is mixed with the vaporized gaseous gas separated by the gas-liquid separator 700 and sent to the low-temperature flow path of the heat exchanger 100, the second oil filter 420 may be positioned at the A position or the C position of FIG. 4. Can be installed on

When the second oil filter 420 is installed at position C of FIG. 4, most of the melted or low viscosity lubricant is collected in the liquid state in the gas-liquid separator 700, and the gas discharged along the sixth supply line L6. Since the amount of the lubricating oil in the state is small, the filtering efficiency is high and the second oil filter 420 does not need to be replaced relatively frequently.

When the second oil filter 420 is installed at position B of FIG. 4, the lubricating oil flowing into the storage tank T may be blocked, thereby preventing contamination of the liquefied gas stored in the storage tank T. There is this.

The first oil filter 410 is installed at the rear end of the compressor 200, and since the boil-off gas compressed by the compressor 200 is approximately 40 to 45 ° C., it is not necessary to use the cryogenic oil filter. However, the temperature of the fluid decompressed by the decompression device 600 is about -160 to -150 ℃ so that at least a portion of the boil-off gas can be re-liquefied, the liquefied gas and the boil-off gas separated by the gas-liquid separator 700 Since the temperature of about -160 to -150 ° C, so that the second oil filter 420 is installed in any position A, B, C of Figure 4, it should be designed for cryogenic temperatures.

In addition, since the lubricating oil mixed in the boil-off gas of about 40 to 45 ° C. compressed by the compressor 200 is mostly in a liquid state or a mist state, the oil separator 300 is suitable for separating the lubricating oil in the liquid state. The first oil filter 410 is designed to be suitable for separating a lubricating oil in a mist state (some may include a lubricating oil in a vapor state).

On the other hand, the lubricating oil mixed with the fluid depressurized by the decompression device 600, the evaporated gas separated by the gas-liquid separator 700, and the liquefied gas separated by the gas-liquid separator 700, which are cryogenic fluids, are below the pour point. Because of the solid (or solidified) state of the second oil filter 420 is designed to be suitable for separating the lubricating oil in the solid (or solidified) state.

5 is an enlarged view of a second oil filter according to an embodiment of the present invention, and FIG. 6 is an enlarged view of a second oil filter according to another embodiment of the present invention.

5 and 6, the second oil filter 420 may have a structure shown in FIG. 5 (hereinafter, referred to as a “lower discharge type”), and a structure shown in FIG. 6 (hereinafter, “ Top discharge type). Dotted lines in FIG. 5 and FIG. 6 indicate the direction of fluid flow.

5 and 6, the second oil filter 420 includes a fixing plate 425 and a filter element 421, and the second oil filter 420 includes an inlet pipe 422 and a discharge pipe 423. , And the oil discharge pipe 424 is connected.

The filter element 421 is installed on the fixed plate 425 to separate the lubricating oil mixed in the fluid flowing through the inlet pipe 422.

FIG. 13 is a plan view of the filter element 421 illustrated in FIGS. 5 and 6. Referring to FIG. 13, the filter element 421 may have a hollow cylindrical shape (Z space in FIG. 13), and a mesh. ) Layers of different sizes may be stacked in a stack. The fluid flowing through the inlet pipe 422 passes through the multi-stage layers included in the filter element 421 and the lubricant is filtered. The filter element 421 may separate the lubricant by physical adsorption.

The fluid (evaporated gas, liquefied gas, or gas-liquid mixed fluid) filtered by the filter element 421 is discharged along the discharge pipe 423, and the lubricating oil filtered by the filter element 421 is oil discharge pipe 424. Is discharged along).

The material of the components used in the second oil filter 420 is composed of a material that can withstand cryogenic temperatures to separate the lubricating oil mixed in the cryogenic fluid. The filter element 421 may be made of a metal material that can withstand cryogenic temperatures, and specifically, the filter element 421 may be made of SUS.

Referring to FIG. 5, the oil filter of the “lower discharge type” has a space formed under the fixed plate 425 after the fluid supplied through the inlet pipe 422 connected to the oil filter is passed through the filter element 421. After passing through (X of FIG. 5), it is discharged through the discharge pipe 423 connected to the lower oil filter.

Oil filter of the 'lower discharge type', the fixing plate 425 is installed under the oil filter, the filter element 421 is installed on the upper surface of the fixing plate 425, filter element 421 based on the fixed plate 425 The discharge pipe 423 is connected to the opposite side.

In addition, the oil filter of the 'lower discharge type' is supplied so that the fluid introduced through the supply pipe 422 can be filtered by the upper part of the filter element 421 (that is, to make full use of the entire filter element). Preferably, the pipe 422 is connected to the upper end of the filter element 421.

The supply pipe 422 and the discharge pipe 423 are opposite to each other (left and right with respect to the filter element 421 in Figure 5) is preferably in the flow of the fluid, the lubricating oil filtered by the filter element 421 Is collected at the bottom of the filter element 421, the oil discharge pipe 424 is preferably connected to the lower side of the filter element 421.

In the case of the 'lower discharge type' oil filter, the oil discharge pipe 424 may be directly connected to the top of the fixed plate 425.

As shown in (a) of FIG. 5, when a fluid having a large number of liquid components (for example, 90% liquid and 10% gas volume ratio) is supplied to an oil filter of a 'lower discharge type', the liquid component has a density. As a result, a proper flow occurs from the top to the bottom, and the filtering effect is excellent.

However, as shown in (b) of FIG. 5, when a fluid having a large number of gas components (for example, a volume ratio of 10% liquid and 90% gas) is supplied to an oil filter of the 'lower discharge type', Small gaseous components stay on top of the oil filter, resulting in poor fluid flow and reduced filtering effects.

Referring to Figure 6, the oil filter of the 'top discharge type', the fluid supplied through the inlet pipe 422 connected to the bottom of the oil filter, the space formed on the fixing plate 425 after passing through the filter element 421 After passing through (Y of Figure 6), it is discharged through the discharge pipe 423 connected to the upper oil filter.

The oil filter of the "top discharge type", the fixing plate 425 is installed on the upper oil filter, the filter element 421 is installed on the lower surface of the fixing plate 425, the filter element 421 based on the fixed plate 425 The discharge pipe 423 is connected to the opposite side.

In addition, the oil filter of the 'top discharge type', so that the fluid introduced through the supply pipe 422 can be filtered by the lower portion of the filter element 421 (that is, to maximize the use of the entire filter element), supply Preferably, the pipe 422 is connected to the lower end of the filter element 421.

The supply pipe 422 and the discharge pipe 423 are installed on the opposite side (left and right with respect to the filter element 421 in Figure 6) is preferable in the flow of the fluid, the lubricating oil filtered by the filter element 421 Is collected at the bottom of the filter element 421, the oil discharge pipe 424 is preferably connected to the lower side of the filter element 421.

Referring to Figure 6, the oil filter of the 'top discharge type, the fluid supplied along the pipe 422 connected to the lower portion of the oil filter passes through the filter element 421 after passing through the pipe 423 connected to the top of the oil filter Is discharged accordingly. The lubricating oil filtered by the filter element 421 is discharged to the outside along a separate pipe 424.

As shown in FIG. 6A, when a fluid having a large number of gas components (for example, a volume ratio of 10% liquid and 90% gas) is supplied to an oil filter of the “top discharge type”, the gas component may have a density. Is small, the proper flow occurs from the bottom to the top, and the filtering effect is excellent.

However, as shown in FIG. 6B, when a fluid having a large number of liquid components (for example, a volume ratio of 90% liquid and 10% gas) is supplied to the oil filter of the 'top discharge type', the density is high. As the large liquid component stays under the oil filter, the fluid flow is poor and the filtering effect is reduced.

Therefore, when installing the second oil filter 420 in the position B of FIG. 4, it is preferable to apply the second oil filter 420 of the 'lower discharge type' shown in FIG. When installing the second oil filter 420 in the position, it is preferable to apply the second oil filter 420 of the 'top discharge type' shown in FIG.

In the case where the second oil filter 420 is installed in the position A of FIG. 4, the fluid decompressed by the pressure reducing device 600 is in a gas-liquid mixed state (theoretically, 100% reliquefaction is possible). Since the ratio is higher, it is preferable to apply the second oil filter 420 of the 'top discharge type' shown in FIG.

The bypass line BL of the present invention branches from the first supply line L1 at the front end of the heat exchanger 100, bypasses the heat exchanger 100, and then, at the second end of the rear end of the heat exchanger 100. Join the supply line (L2).

Typically, the bypass line bypassing the heat exchanger is installed inside the heat exchanger to form an integral part with the heat exchanger. When the bypass line is installed inside the heat exchanger, when the valves installed at the front and / or rear ends of the heat exchanger are closed, no fluid is supplied to the bypass line at the same time as the fluid is not supplied to the heat exchanger.

However, in the present invention, the bypass line BL is installed separately from the heat exchanger 100 outside the heat exchanger 100, and the first valve 510 and / or the heat exchanger 100 installed in front of the heat exchanger 100. The bypass line BL branches from the first supply line L1 in front of the first valve 510 so that the bypass line BL can be supplied with the evaporation gas even when the second valve 520 installed at the rear end is closed. And merged into the second supply line L2 at the rear end of the second valve 520.

The bypass valve 590 is installed on the bypass line BL, and the bypass valve 590 is normally closed and opens when it is necessary to use the bypass line BL.

Basically, the bypass line BL is used when the heat exchanger 100 cannot be used, such as when the heat exchanger 100 is broken or needs maintenance. For example, when the boil-off gas reliquefaction system of this embodiment sends some or all of the boil-off gas compressed by the compressor 200 to the high-pressure engine, when the heat exchanger 100 becomes unavailable, the boil-off gas cannot be used in the high-pressure engine. After abandoning the reliquefaction of the excess boil-off gas, the boil-off gas discharged from the storage tank T is bypassed and supplied directly to the compressor 200 by bypassing the heat exchanger 100 along the bypass line BL, and then the compressor 200. By supplying the compressed boil-off gas to the high-pressure engine, the excess boil-off gas can be sent to the GCU for incineration.

As an example of using the bypass line BL for maintenance of the heat exchanger 100, when the flow path of the heat exchanger 100 is blocked by condensed or solidified lubricant, condensed or solidified using the bypass line BL. The removal of lubricating oil is mentioned.

In addition, when there is little excess evaporation gas, such as a ballast state of a ship, and it is not necessary to reliquefy the evaporation gas, all the evaporation gas discharged from the storage tank T is sent to the bypass line BL, and the evaporation gas is heat-exchanged. Bypass the machine 100 to be sent directly to the compressor 200. The boil-off gas compressed in the compressor 200 is used as a fuel of a high pressure engine. If it is determined that there is almost no excess boil-off gas and there is no need to reliquefy the boil-off gas, the bypass valve 590 may be controlled to open automatically.

The inventors of the present invention have found that a large pressure drop of the boil-off gas is generated by the heat-exchanger when the boil-off gas is supplied to the engine through the narrow heat-exchanger according to the present invention. When there is no need for reliquefaction, the engine can be smoothly supplied by bypassing the heat exchanger and compressing the boil-off gas as described above.

In addition, the bypass line BL may also be used when the amount of the boil-off gas is increased without re-liquefying the boil-off gas.

When re-liquefying the boil-off gas without re-liquefying the boil-off gas but increasing the amount of boil-off gas (that is, when the boil-off gas re-liquefaction starts or restarts), the boil-off gas discharged from the storage tank T is bypassed (BL). All of the evaporated gas may be directly supplied to the compressor 200 by bypassing the heat exchanger 100, and the evaporated gas compressed by the compressor 200 may be sent to the high temperature flow path of the heat exchanger 100. . Part of the boil-off gas compressed by the compressor 200 may be sent to the high pressure engine.

Through the above-described process, when the temperature of the heat exchanger 100 high temperature flow path is increased during the re-liquefaction start or restart of the boil-off gas, it may remain in the heat-exchanger 100, other equipment, piping, etc. in the previous boil-off gas re-liquefaction process, After removing the condensed or solidified lubricating oil or other impurities, it is possible to start the reliquefaction of the boil-off gas.

If the boil-off gas reliquefaction starts or restarts, the low-temperature boil-off gas discharged from the storage tank T is directly transferred to the heat exchanger 100 without the process of increasing the temperature of the high-temperature flow path of the heat exchanger 100 using the bypass line BL. When supplied to the heat exchanger, since the low-temperature evaporated gas discharged from the storage tank T is supplied to the low-temperature flow path of the heat exchanger 100 while the hot evaporation gas is not yet supplied to the high-temperature flow path of the heat exchanger 100. Lubricants that have not yet been condensed or solidified in 100 may also be condensed or solidified by lowering the temperature of the heat exchanger 100.

While the process of increasing the temperature of the heat exchanger 100 hot passage by using the bypass line BL, after a certain time (if it is determined that condensed or solidified lubricant or other impurities are almost removed), the closed first The valve 510 and the second valve 520 are gradually opened, and the bypass valve 590 is slowly closed to start the boil-off gas reliquefaction. After a further time, the first valve 510 and the second valve 520 are completely opened and the bypass valve 590 is completely closed, so that all the boil-off gas discharged from the storage tank T is boil-off gas in the heat exchanger 100. It is used as a refrigerant for reliquefaction.

In addition, the bypass line BL may be utilized to satisfy the suction pressure condition of the compressor 200 when the pressure inside the storage tank T is low.

In addition, when it is necessary to control the internal pressure of the storage tank (T) to a low range, a bypass line (BL) may be used to satisfy the suction pressure condition of the compressor (200) even if the pressure of the storage tank (T) is reduced. Can be.

The bypass line BL is used to satisfy the suction pressure condition of the compressor 200 when the lubricating oil is condensed or solidified using the bypass line BL and when the pressure inside the storage tank T is low. If you look at in more detail as follows.

One. Bypass line (BL)  When used to remove condensed or solidified lubricant

A predetermined lubricating oil is mixed in the evaporated gas passed through the cylinder of the oil supply lubrication type of the compressor 200, and the lubricating oil mixed in the evaporated gas is condensed or solidified before the evaporated gas in the heat exchanger 100, so that the flow path of the heat exchanger 100 is The amount of condensed or solidified lubricant accumulated in the flow path of the heat exchanger 100 increases as time passes, so that after a certain time, it is necessary to remove the condensed or solidified lubricant in the heat exchanger 100. The inventors of the present invention have found that it occurs.

In particular, the heat exchanger 100 of the present embodiment is preferably a PCHE (also referred to as a printed circuit heat exchanger, DCHE) in consideration of the pressure and / or flow rate of the evaporated gas to be reliquefied, the reliquefaction efficiency, and the like. The flow path is narrow (microchannel flow path) and is formed to be bent, so that the flow path can be easily blocked by the condensed or solidified lubricant, and particularly, the condensed or solidified lubricant is well accumulated in the curved portion of the flow path. PCHE (DCHE) is produced by companies such as Kobelko and Alfalaval.

The condensed or solidified lubricant can be removed by the following steps.

1) determining whether to remove condensed or solidified lubricant

2) opening the bypass valve 590, closing the first valve 510 and the second valve 520

3) a step in which the boil-off gas discharged from the storage tank T is compressed by the compressor 200 through the bypass line BL.

4) sending a part or all of the high temperature boil-off gas compressed by the compressor 200 to the heat exchanger 100

5) sending the evaporated gas passed through the heat exchanger 100 to the gas-liquid separator 700

6) discharging the lubricating oil collected in the gas-liquid separator 700

7) confirming that the heat exchanger 100 is normalized

1) Condensed or solidified lubricant Whether to remove  Judgment Step

When the flow path of the heat exchanger 100 is blocked by condensed or solidified lubricating oil, the cooling efficiency of the heat exchanger 100 is reduced. Therefore, when the performance of the heat exchanger 100 falls below a certain value as compared to the normal case, it can be estimated that the condensed or solidified lubricant oil accumulated in the heat exchanger 100 to some extent, for example, of the heat exchanger 100. If the performance drops to about 50 to 90% or less in a normal case, preferably about 60 to 80% or less, and more preferably about 70% or less, it is determined that lubricant condensed or solidified in the heat exchanger 100 should be removed. can do.

When the performance of the heat exchanger 100 falls, the temperature difference between the low temperature evaporated gas L1 supplied to the heat exchanger 100 and the low temperature evaporated gas L4 discharged from the heat exchanger 100 increases, and the heat exchanger 100 The temperature difference between the high temperature boil-off gas L2 discharged from the high temperature boil-off gas L3 supplied to the heat exchanger 100 also increases. In addition, when the flow path of the heat exchanger 100 is blocked by condensed or solidified lubricating oil, the flow path of the heat exchanger 100 is narrowed, so that the pressure difference between the front end L3 and the rear end L4 of the heat exchanger 100 increases. Done.

Therefore, the temperature difference 810, 840 of the low temperature fluid supplied to the heat exchanger 100 or discharged from the heat exchanger 100, the temperature difference 820 of the high temperature fluid supplied to the heat exchanger 100 or discharged from the heat exchanger 100. , 830, the pressure difference 910, 920, etc. applied to the high temperature flow path of the heat exchanger 100, may determine whether to remove the condensed or solidified lubricant.

Specifically, the temperature of the boil-off gas discharged from the storage tank T measured by the first temperature sensor 810 and sent to the heat exchanger 100, and the compressor 200 measured by the fourth temperature sensor 840. By the heat exchanger 100 after being compressed by the temperature difference (absolute value, hereinafter referred to as 'temperature difference of low temperature flow') of the boil-off gas is more than the normal case, the state for a certain time If the abnormality persists, it may be determined that heat exchange is not performed properly in the heat exchanger 100.

For example, if the temperature difference of the low temperature flow is 20 to 50 ° C. or higher, preferably 30 to 40 ° C. or higher, and more preferably approximately 35 ° C. or higher, the condensed or solidified lubricant may be replaced. It can be determined that it is time to discharge.

When the heat exchanger 100 operates normally, the boil-off gas compressed by the compressor 200 to about 300 bar is about 40 to 45 ° C., and about −160 to −140 ° C. discharged from the storage tank T. The evaporated gas may be slightly increased in temperature while being transported to the heat exchanger 100 to be about -150 to -110 ° C, preferably about -120 ° C.

The vaporization gas reliquefaction system of the present embodiment includes a gas-liquid separator 700, and the gaseous gaseous gas separated by the gas-liquid separator 700 joins the boil-off gas discharged from the storage tank T to exchange heat exchanger 100. In the case where it is sent to), the temperature of the boil-off gas supplied to the heat exchanger 100 is lower than the case of sending only the boil-off gas discharged from the storage tank T to the heat exchanger 100, by the gas-liquid separator 700 As the amount of separated gaseous boil-off gas increases, the temperature of the boil-off gas supplied to the heat exchanger 100 may be lowered.

The boil-off gas of about 40 to 45 ° C supplied to the heat exchanger 100 along the third supply line L3 is cooled by the heat exchanger 100 to be approximately -130 to -110 ° C. The temperature difference of the low temperature flow 'is preferably approximately 2 to 3 ° C.

In addition, after the discharge from the storage tank (T) measured by the second temperature sensor 820, the temperature of the boil-off gas used as the refrigerant in the heat exchanger 100, and the compressor 200 measured by the third temperature sensor 830 ) And the temperature difference of the boil-off gas sent to the heat exchanger 100 after being compressed by () means an absolute value (hereinafter, referred to as 'temperature difference of high temperature flow'). If the abnormality persists, it may be determined that heat exchange is not performed properly in the heat exchanger 100.

Condensed or solidified lubricating oil should be discharged when the temperature difference of the high temperature flow is 20 to 50 ° C. or higher, preferably 30 to 40 ° C. or higher, and more preferably approximately 35 ° C. or higher. It can be determined that the time.

When the heat exchanger 100 operates normally, the temperature of about -150 to -110 ° C (preferably about -120 ° C), which is somewhat increased in temperature while being discharged from the storage tank T and transferred to the heat exchanger 100, is preferred. The boil-off gas may be approximately −80 to 40 ° C. depending on the speed of the vessel after being used as the refrigerant in the heat exchanger 100, and the boil-off gas of approximately −80 to 40 ° C. used as the refrigerant in the heat exchanger 100. Is compressed in the compressor 200 to be approximately 40 to 45 ° C.

In addition, the pressure of the boil-off gas sent to the heat exchanger 100 after being compressed by the compressor 200 measured by the first pressure sensor 910 and the heat exchanger 100 measured by the second pressure sensor 920 When the pressure difference of the boil-off gas cooled by the following (hereinafter, referred to as the 'pressure difference in the high temperature flow path') is more than normal and the state lasts for a predetermined time, the heat exchanger 100 does not operate properly. Can be judged.

The evaporated gas discharged from the storage tank (T) does not contain oil components or is present at a very low level, and when the lubricating oil is mixed with the evaporated gas when the evaporated gas is compressed by the compressor 200, the storage tank (T) After using the evaporated gas discharged from the refrigerant as a refrigerant and condensed or solidified lubricating oil hardly accumulates in the low-temperature flow path of the heat exchanger 100 to be sent to the compressor 200, after cooling the evaporated gas compressed by the compressor 200 The condensed or solidified lubricant is accumulated in the high temperature flow path of the heat exchanger 100 that is sent to the decompression device 600.

Therefore, the phenomenon in which the flow path is blocked by the condensed or solidified lubricant and the pressure difference between the front and rear ends of the heat exchanger 100 increases rapidly in the high temperature flow path, so that the pressure applied to the high temperature flow path of the heat exchanger 100 is measured to condense or solidify. Determine whether the lubricating oil should be removed.

Determining whether to remove the condensed or solidified lubricant by the pressure difference between the front and rear ends of the heat exchanger 100, in particular, the PCHE that is formed to be narrow and curved in the heat exchanger 100 of the present embodiment can be applied. Considering this, it can be usefully utilized.

For example, if the pressure difference in the high-temperature flow path is more than twice as normal and the state lasts for 1 hour or more, it may be determined that it is time to discharge the condensed or solidified lubricant.

When the heat exchanger 100 operates normally, the boil-off gas compressed by the compressor 200 passes through the heat exchanger 100 and does not drop significantly even when cooled, and is about 0.5 to 2.5 bar, preferably about 0.7 to A pressure drop of about 1.5 bar, more preferably about 1 bar occurs. Condensation is maintained when the pressure difference in the high temperature flow path is at least a certain pressure, such as 1 to 5 bar or more, preferably 1.5 to 3 bar or more, and more preferably approximately 2 bar (200 kPa) or more. Alternatively, it may be determined that it is time to discharge the solidified lubricant.

As described above, it is possible to determine whether to remove the condensed or solidified lubricant by using any one of the 'temperature difference of the low temperature flow', 'temperature difference of the high temperature flow', and 'pressure difference of the high temperature flow path'. However, in order to improve reliability, it is necessary to determine whether to remove condensed or solidified lubricating oil by using at least two of 'temperature difference of low temperature flow', 'temperature difference of high temperature flow', and 'pressure difference of high temperature flow path'. It is desirable to.

For example, the smaller of the 'temperature difference in low temperature flow' and 'temperature difference in high temperature flow' lasts for at least 1 hour with a temperature of 35 ° C. or higher, or at least twice as long as the 'pressure difference in high temperature flow path' is normal or 200 If it lasts for more than 1 hour with kPa or more, it can be determined that it is time to remove the condensed or solidified lubricant.

The first temperature sensor 810, the second temperature sensor 820, the third temperature sensor 830, the fourth temperature sensor 840, the first pressure sensor 910, and the second pressure sensor 920, It can be seen as a kind of sensing means for detecting whether the heat exchanger 100 is blocked by lubricating oil.

In addition, the boil-off gas reliquefaction system of the present invention, the first temperature sensor 810, the second temperature sensor 820, the third temperature sensor 830, the fourth temperature sensor 840, the first pressure sensor 910. And, based on a value detected by at least one of the second pressure sensors 920, a control device (not shown) that determines whether the heat exchanger 100 is blocked by the lubricating oil. The control device can be regarded as a kind of determination means for determining whether the heat exchanger 100 is blocked by lubricating oil.

Whether to remove the condensed or solidified lubricant may be determined by the alarm, which will be described later.

2) opening the bypass valve 590, closing the first valve 510 and the second valve 520

If it is determined whether to remove the condensed or solidified lubricant in the first step, and determines to remove the condensed or solidified lubricant in the heat exchanger 100, the bypass valve 590 installed on the bypass line (BL) Is opened, and the first valve 510 provided on the first supply line L1 and the second valve 520 provided on the second supply line L2 are closed.

When the bypass valve 590 is opened and the first valve 510 and the second valve 520 are closed, the boil-off gas discharged from the storage tank T is sent to the compressor 200 through the bypass line BL and further heat exchanged. It is not sent to machine 100. Therefore, the refrigerant is not supplied to the heat exchanger 100.

3) a step in which the boil-off gas discharged from the storage tank T is compressed by the compressor 200 through the bypass line BL.

The boil-off gas discharged from the storage tank T is sent to the compressor 200 after bypassing the heat exchanger 100 through the bypass line BL. The boil-off gas sent to the compressor 200 is compressed by the compressor 200 and the temperature as well as the pressure is increased, and the temperature of the boil-off gas compressed by the compressor 200 to about 300 bar is about 40 to 45 ° C.

* 4) sending some or all of the high temperature boil-off gas compressed by the compressor 200 to the heat exchanger 100

When the evaporated gas, the temperature of which is compressed by the compressor 200, is continuously sent to the heat exchanger 100, the low-temperature evaporated gas discharged from the storage tank T used as the refrigerant in the heat exchanger 100 is the heat exchanger 100. Since only the evaporated gas having a high temperature is continuously supplied to the heat exchanger 100, the temperature of the high-temperature flow path of the heat exchanger 100 through which the evaporated gas compressed by the compressor 200 passes is gradually increased.

When the temperature of the high temperature flow path of the heat exchanger 100 is higher than the temperature at which the lubricating oil is condensed or solidified, the condensed or solidified lubricating oil accumulated in the heat exchanger 100 is gradually melted or the viscosity is lowered, the melted or the viscosity is lowered. The lubricating oil is mixed with the boil-off gas to exit the heat exchanger (100).

When removing the condensed or solidified lubricating oil by using the bypass line (BL), the high-temperature flow path of the boil-off gas (BL), the compressor 200, the heat exchanger 100 until the heat exchanger 100 is normalized Circulating the decompression device 600 and the gas-liquid separator 700.

In addition, when removing the condensed or solidified lubricating oil by using the bypass line (BL), discharged from the storage tank (T), the high-temperature flow path of the bypass line (BL), compressor 200, heat exchanger 100, and pressure reduction The boil-off gas passing through the device 600 may be sent to a tank or other recovery device installed separately from the storage tank T in a state in which the lubricating oil and the boil-off gas having melted or lowered viscosity are mixed. The boil-off gas inside the tank or other recovery device installed separately from the storage tank T can be sent back to the bypass line BL to continue the process of removing the condensed or solidified lubricant.

When the melted or low viscosity lubricating oil and the evaporated gas are mixed and sent to a tank or other recovery device installed separately from the storage tank T, the gas-liquid separator 700 may be installed even after the decompression device 600 is installed. (700) plays the same role as the conventional boil-off gas reliquefaction system and because the lubricating oil melted or the viscosity is not collected inside the gas-liquid separator 700 (the lubricating oil melted or the viscosity is lower than the storage tank (T)) As it is collected in a separate tank or other recovery device), it is not necessary to include the improved gas-liquid separator 700 to discharge the lubricating oil, thereby reducing the cost.

5) the boil-off gas passed through the heat exchanger 100 With gas-liquid separator 700  Sending steps

As the temperature of the high-temperature flow path of the heat exchanger 100 increases, the condensed or solidified lubricating oil accumulated in the heat exchanger 100 is melted or has a high viscosity and is mixed with the evaporated gas and sent to the gas-liquid separator 700. In the process of removing the condensed or solidified lubricating oil in the heat exchanger 100 using the bypass line BL, reliquefaction of the evaporated gas is not performed, so that the liquefied liquefied gas does not collect in the gas-liquid separator 700, The evaporated gas in the state and the lubricating oil having melted or lowered viscosity are collected.

The gaseous evaporated gas collected in the gas-liquid separator 700 is discharged from the gas-liquid separator 700 along the sixth supply line (L6) and sent back to the compressor 200 along the bypass line (BL). Since the first valve 510 is closed in the second step, the gaseous boil-off gas separated by the gas-liquid separator 700 joins the boil-off gas discharged from the storage tank T and moves along the bypass line BL. It is supplied to 200 and is not supplied to the low temperature flow path of the heat exchanger 100.

Therefore, supplying the gaseous evaporated gas separated by the gas-liquid separator 700 to the bypass line BL while the first valve 510 is closed, the lubricating oil partially contained in the evaporated gas is a heat exchanger (100 By preventing supply to the low temperature flow path of the), there is an advantage that the low temperature flow path of the heat exchanger 100 can be blocked.

The gaseous evaporated gas collected in the gas-liquid separator 700 is discharged from the gas-liquid separator 700 along the sixth supply line (L6) and sent back to the compressor 200 along the bypass line (BL), the heat exchange The temperature of the hot passage of the apparatus 100 is compressed until the temperature of the boil-off gas sent to the hot passage of the heat exchanger 100 after being compressed by the compressor 200 is continued. However, as a rule of thumb, the cycle may continue until enough time has passed.

While removing the condensed or solidified lubricating oil in the heat exchanger 100 by using the bypass line BL, the lubricating oil collected in the gas-liquid separator 700 is closed by the eighth valve 581 to close the fifth supply line L5. Therefore, it should not be sent to the storage tank (T). When lubricating oil is introduced into the storage tank (T), the purity of the liquefied gas stored in the storage tank (T) may be lowered, thereby reducing the value of the liquefied gas.

6) Gas-liquid separator 700  Draining the collected lubricant

The melted or low viscosity lubricating oil discharged from the heat exchanger 100 is collected in the gas-liquid separator 700. In order to process the lubricating oil collected in the gas-liquid separator 700, the gas-liquids conventionally used in the present embodiment It is possible to use the gas-liquid separator 700, which is an improvement of the separator 700.

10 is an enlarged view of a heat exchanger and a gas-liquid separator according to an embodiment of the present invention. For convenience of description, some of the devices are not shown.

Referring to FIG. 10, the gas-liquid separator 700 includes lubricating oil collected in the gas-liquid separator 700 in addition to the fifth supply line L5 that sends the liquefied gas separated by the gas-liquid separator 700 to the storage tank T. A lubricating oil discharge line OL for discharging is additionally installed. Lubricating oil discharge line (OL) is connected to the lower end of the gas-liquid separator 700, and the end of the fifth supply line (L5) is connected to the lubricating oil discharge line (OL) so that the oil collected in the lower portion of the gas-liquid separator 700 can be effectively discharged. The lower portion of the gas-liquid separator 700 is positioned higher in the gas-liquid separator 700. In order to prevent the fifth supply line L5 from being blocked by the lubricating oil, it is preferable to position the end of the fifth supply line L5 higher than the level of the lubricating oil when the amount of the lubricating oil collected in the gas-liquid separator 700 reaches the maximum. .

A third valve 530 may be installed on the lubricating oil discharge line OL to adjust the flow rate and opening and closing of the fluid, and a plurality of third valves 530 may be installed.

Since the lubricating oil collected in the gas-liquid separator 700 may not naturally discharge or may take a long time to discharge, the lubricating oil in the gas-liquid separator 700 may be discharged through nitrogen purging. When the nitrogen of about 5 to 7 bar is supplied to the gas-liquid separator 700, the pressure in the gas-liquid separator 700 increases, so that oil may be discharged quickly.

In order to discharge the lubricating oil in the gas-liquid separator 700 by nitrogen purging, a nitrogen supply line NL may be installed to join the third supply line L3 in front of the heat exchanger 100. If necessary, multiple nitrogen supply lines may be installed at different locations.

A nitrogen valve 583 is provided on the nitrogen supply line NL to control the flow rate and opening and closing of the fluid. In the case where the nitrogen supply line NL is not used, the nitrogen valve 583 is kept closed and nitrogen purged. In case of supplying nitrogen to the gas-liquid separator 700, for example, when it is necessary to use a nitrogen line NL, the nitrogen valve 583 is opened. A plurality of nitrogen valves 583 may be provided.

Nitrogen purging may be performed by injecting nitrogen directly into the gas-liquid separator 700, but if a nitrogen supply line is already installed for another use, the lubricant in the gas-liquid separator 700 may be utilized by using the nitrogen supply line already installed. It is preferable to discharge it.

Send all of the evaporated gas discharged from the storage tank (T) to the bypass line (BL) to be compressed by the compressor 200, send the boiled gas compressed by the compressor 200 to the high temperature flow path of the heat exchanger (100), After passing through the high-temperature flow path of the heat exchanger 100 sends the reduced pressure to the decompression device 600 to the gas-liquid separator 700, and sends the boil-off gas discharged from the gas-liquid separator 700 back to the bypass line (BL). When the process continues, when it is determined that most of the lubricating oil condensed or solidified with the inside of the heat exchanger 100 is collected in the gas-liquid separator 700 (that is, the heat exchanger 100 is normalized), the compressor 200 By blocking the inflow of the compressed boil-off gas into the heat exchanger 100, the nitrogen valve 583 is opened to carry out nitrogen purging.

7) The heat exchanger 100 Normalized  Step to verify

When the condensed or solidified lubricating oil in the heat exchanger 100 is discharged and it is determined that the heat exchanger 100 is normalized again, when the process of discharging the lubricating oil in the gas-liquid separator 700 is completed, the first valve 510 and The second valve 520 is opened, the bypass valve 590 is closed, and the boil-off gas reliquefaction system is normally operated again. When the boil-off gas reliquefaction system is normally operated, the boil-off gas discharged from the storage tank T is used as the refrigerant in the heat exchanger 100, and the boil-off gas used as the refrigerant in the heat exchanger 100 is supplied by the compressor 200. Some or all of the liquid is reliquefied through a compression process, a cooling process by the heat exchanger 100, and a decompression process by the decompression device 600.

The determination that the heat exchanger 100 has been normalized again is the same as when determining whether to remove condensed or solidified lubricants, such as 'temperature difference in low temperature flow', 'temperature difference in high temperature flow', and 'pressure difference in high temperature flow path'. One or more values of 'can be used as an indicator.

Through the above-described process, not only the condensed or solidified lubricant in the heat exchanger 100, but also condensed or solidified lubricants accumulated in pipes, valves, measuring instruments, and various equipments may be removed.

Conventionally, during the above-described steps of removing the condensed or solidified lubricating oil in the heat exchanger 100 from the heat exchanger 100 using the bypass line BL, a high pressure engine and / or a low pressure engine (hereinafter, ' Engine ”. When servicing a part of the equipment included in the fuel supply system or the reliquefaction system, it is common not to drive the engine because it is not possible to supply fuel to the engine or to re-liquefy the excess boil-off gas.

However, as in the present invention, if the engine is driven while removing the condensed or solidified lubricating oil in the heat exchanger 100, the heat exchanger 100 can be maintained while driving the engine, and thus the heat exchanger 100 ), It is possible to propel a ship and generate power during maintenance, and to remove condensed or solidified lubricating oil by using surplus boil-off gas used in the engine.

In addition, if the engine is driven while removing the condensed or solidified lubricating oil in the heat exchanger 100, the lubricating oil compressed by the compressor 200 and mixed in the boil-off gas may be burned by the engine. That is, the engine is not only used for the propulsion or power generation of the vessel, but also serves to remove oil mixed in the boil-off gas.

7 is a schematic diagram of a boil-off gas reliquefaction system according to a fourth preferred embodiment of the present invention.

As shown in FIG. 7, two compressors 200 and 210 of the present invention may be installed in parallel. The two compressors 200 and 210 may have the same specifications, and when one fails, the other may serve as a redundancy. In FIG. 7, for convenience of description, the illustration of the other devices shown in FIG. 2 is omitted.

Referring to FIG. 7, in the case where two compressors 200 and 210 are installed in parallel as in the present embodiment, similarly to the second embodiment, the boil-off gas discharged from the storage tank T is supplied to the first supply line L1. (Or the boil-off gas, which is sent to the first compressor 200 through the bypass line BL and the second supply line L2, and compressed by the first compressor 200, is partially supplied to the fuel supply line SL). ) Is sent to the high pressure engine, the excess evaporated gas may be sent to the heat exchanger 100 through the third supply line (L3) to undergo a reliquefaction process. In addition, on the third supply line L3 of the present embodiment, like the second embodiment, a seventh valve 570 may be installed to control the flow rate and opening and closing of the fluid.

In addition, when two compressors 200 and 210 are installed in parallel as in the present embodiment, the boil-off gas discharged from the storage tank T may include the first supply line L1 (or bypass line BL) and the seventh. The boil-off gas sent to the second compressor 210 through the supply line L22 and compressed by the second compressor 210 is partially sent to the high-pressure engine along the fuel supply line SL, and the excess boil-off gas. May be sent to the heat exchanger 100 through an eighth supply line L33 to undergo a reliquefaction process. A tenth valve 571 may be installed on the eighth supply line L33 to adjust the flow rate and the opening and closing of the fluid.

8 is an enlarged view of a pressure reducing device according to an embodiment of the present invention, and FIG. 9 is an enlarged view of a pressure reducing device according to another embodiment of the present invention.

According to the present invention, as shown in FIG. 8, two pressure reducing devices 600 and 610 may be installed in parallel. The two pressure reducing devices 600 and 610 installed in parallel may act as redundancy when one cannot be used due to failure, maintenance, etc., and two pressure reducing devices installed in parallel may be used. Isolation valves 620 may be installed at the front and rear ends of each of the devices 600, 610.

In addition, according to the present invention, as shown in Figure 9, a plurality of first pressure reducing device 600 is installed in series, a plurality of second pressure reducing device 610 is installed in series, a plurality of installed in series A plurality of second pressure reducing devices 610 installed in series with the first pressure reducing device 600 may be installed in parallel. In FIG. 9, two first pressure reducing devices 600 and two second pressure reducing devices 610 are respectively installed in series.

Depending on the manufacturer, several pressure reducing devices may be connected in series for stability of pressure reduction. In case of connecting multiple pressure reducing devices in series, the evaporation gas is decompressed through multiple stages. Compared with the case of depressurizing at a time, there is an advantage that the life of the decompression device can be prevented from being shortened by reducing the burden on each decompression device.

As shown in FIG. 9, the plurality of first pressure reducing devices 600 and the plurality of second pressure reducing devices 610 are connected in series, respectively, and the plurality of second installed in series with the plurality of first pressure reducing devices 600 installed in series. Even when the decompression devices 610 are connected in parallel, when one or more of the plurality of first decompression devices 600 installed in series have failed, the plurality of second decompression devices 610 installed in series may have redundancy. When one or more of the plurality of second pressure reducing devices 610 installed in series fail, the plurality of first pressure reducing devices 600 installed in series may serve as redundancy.

In addition, an isolation valve 620 may be installed at the front and rear ends of the plurality of first pressure reducing devices 600 installed in series, respectively, and also at the front and rear ends of the plurality of second pressure reducing devices 610 installed in series. Isolation valve 620 may be installed.

The isolation valve 620 shown in FIGS. 8 and 9 isolates the pressure reducing devices 600 and 610 when the pressure reducing devices 600 and 610 are broken, and when the maintenance of the pressure reducing devices 600 and 610 is required. Used to isolate.

Meanwhile, as described above, whether or not to remove the condensed or solidified lubricant may be determined by an alarm. The process of determining by the alarm whether to remove the condensed or solidified lubricant may be performed by: ① alarm activation step and ② alarm It may include the generation step.

① Alarm activation step

The alarm may be activated when the boil-off gas reliquefaction system of the present invention re-liquefies the boil-off gas, and the alarm may be deactivated when the boil-off gas does not re-liquefy. If all of the evaporated gas discharged from the storage tank (T) is used in the engine and there is no excess evaporated gas, or the equipment necessary for reliquefaction cannot be used for reasons such as failure or maintenance, the evaporated gas is not reliquefied.

That is, it is possible to determine whether to activate the alarm according to whether the boil-off gas reliquefaction system of the present invention is re-liquefying boil-off gas, and whether or not the boil-off gas is reliquefaction is determined as follows according to the configuration of the system can do.

■ The boil-off gas reliquefaction system of the present invention includes one compressor 200 and one decompression device 600 as shown in FIG.

Whether the opening degree of the pressure reducing device 600 is equal to or greater than the first set value, whether the seventh valve 570 is open, whether the second valve 520 is open, or the liquefied gas inside the gas-liquid separator 700 When one or more conditions of whether the water level is equal to or greater than the second set value are satisfied, it can be determined that the boil-off gas is reliquefied.

However, since the second valve 520 is opened not only to reliquefy the boil-off gas but also to supply the boil-off gas as fuel to the engine even if the boil-off gas is not liquefied, “the second valve 520 is open. It is preferable to use it as a condition for determining whether to re-liquefy the boil-off gas together with other conditions, rather than to use as a condition for judging that the boil-off gas is reliquefaction alone. The same applies to the case where the configuration of the system is different.

In addition, the liquefied gas re-liquefied through the compression process by the compressor 200, the cooling process by the heat exchanger 100, and the decompression process by the decompression device 600 is collected in the gas-liquid separator 700. For example, the level of the liquefied gas inside the gas-liquid separator 700 may be used as an indicator for determining whether the boil-off gas is reliquefied. The second set value may vary depending on the amount of liquefied gas stored in the storage tank T, the speed of the ship, and the like, hereinafter, even when the configuration of the system is changed.

In order to increase the reliability of the judgment, it is preferable to determine that the boil-off gas is reliquefied when both conditions are satisfied. For example, the opening ratio of the pressure reducing device 600 is equal to or greater than the first set value, and the seventh valve is used. When 570 is open, the second valve 520 is open, and the level of the liquefied gas inside the gas-liquid separator 700 is equal to or greater than the second set value, it can be determined that the boil-off gas is reliquefied. The alarm can be activated.

The first set value, which is the opening degree of the pressure reduction device 600, may be about 1% to 4%, preferably about 2% to 3%, and more preferably about 2%.

■ comprising a boil-off gas re-liquefaction system, with the two pressure-reducing device (600, 610) connected in parallel as shown it includes a single compressor 200, shown in Figure 8. As shown in Figure 2 of the present invention Occation

Whether the opening degree of the first pressure reducing device 600 or the second pressure reducing device 610 is equal to or greater than the first set value, whether the seventh valve 570 is open, or whether the second valve 520 is open. When the water level of the liquefied gas inside the gas-liquid separator 700 is equal to or greater than the second set value, it may be determined that the boil-off gas is reliquefied.

In order to increase the reliability of the judgment, it is preferable to determine that the evaporated gas is reliquefied when two or more conditions are satisfied. For example, the opening rate of the first decompression device 600 or the second decompression device 610 is preferable. When the water level of the liquefied gas inside the gas-liquid separator 700 is equal to or greater than the first set value, the seventh valve 570 is opened, the second valve 520 is opened, and the second level is equal to or greater than the second set value, It may be determined that the gas is reliquefying and an alarm may be activated.

The first set value, which is the opening degree of the first decompression device 600 or the second decompression device 610, may be about 1% to 4%, preferably about 2% to 3%, more preferably about May be 2%.

■ The boil-off gas reliquefaction system of the present invention includes a single compressor 200 as shown in FIG. 2 and in series with a plurality of first pressure reducing devices 600 installed in series as shown in FIG. 9. When a plurality of installed second decompression device 610 is connected in parallel

Whether the opening degree of any one of the plurality of first pressure reducing devices 600 installed in series or any of the plurality of second pressure reducing devices 610 installed in series is equal to or greater than the first set value, and the seventh valve 570 is If one or more of the following conditions are met: whether the open state, the second valve 520 is open, and whether the level of the liquefied gas inside the gas-liquid separator 700 is greater than or equal to the second set value, it is determined that the vaporized gas is reliquefied. can do.

In order to increase the reliability of the judgment, it is preferable to determine that the evaporated gas is reliquefied when two or more conditions are satisfied. For example, any one of a plurality of first pressure reducing devices 600 installed in series or in series The opening degree of any one of the plurality of installed second pressure reducing devices 610 is equal to or greater than the first set value, the seventh valve 570 is open, the second valve 520 is open, and the gas-liquid separator 700 In the case where the level of the internal liquefied gas is greater than or equal to the second set value, it can be determined that the evaporated gas is reliquefied, and the alarm can be activated.

The first set value, which is the opening degree of the first decompression device 600 or the second decompression device 610, may be about 1% to 4%, preferably about 2% to 3%, more preferably about May be 2%.

■ The boil-off gas reliquefaction system of the present invention includes two compressors 200 and 210 installed in parallel as shown in FIG. 7, and includes one decompression device 600 as shown in FIG. 2. Occation

Whether the opening degree of the pressure reduction device 600 is equal to or greater than the first set value, whether the seventh valve 570 or the tenth valve 571 is open, whether the second valve 520 is open, the gas-liquid separator (700) When one or more conditions of whether the level of the internal liquefied gas is greater than or equal to the second set value is satisfied, it may be determined that the boil-off gas is reliquefied.

When the first compressor 200 is used, the condition is whether the seventh valve 570 is open or not, and when the second compressor 210 is used, the tenth valve 571 is open. Is used as a condition.

In order to increase the reliability of the judgment, it is preferable to determine that the evaporated gas is reliquefied when two or more conditions are satisfied. For example, the opening ratio of the decompression device 600 is equal to or greater than the first set value, and the seventh When the valve 570 or the tenth valve 571 is open, the second valve 520 is open, and the level of the liquefied gas inside the gas-liquid separator 700 is equal to or greater than the second set value, the boil-off gas is reset. You can determine that you are liquefying and activate the alarm.

The first set value, which is the opening degree of the pressure reduction device 600, may be about 1% to 4%, preferably about 2% to 3%, and more preferably about 2%.

■ The boil-off gas reliquefaction system of the present invention includes two compressors 200 and 210 installed in parallel as shown in FIG. 7, and two decompression devices 600 connected in parallel as shown in FIG. 8. 610)

Whether the opening degree of the first pressure reducing device 600 or the second pressure reducing device 610 is equal to or greater than the first set value, whether the seventh valve 570 or the tenth valve 571 is open, and the second valve ( It may be determined that the liquefied gas is reliquefied if one or more of the conditions 520, the open state, and whether the level of the liquefied gas inside the gas-liquid separator 700 is equal to or greater than the second set value is satisfied.

When the first compressor 200 is used, the condition is whether the seventh valve 570 is open or not, and when the second compressor 210 is used, the tenth valve 571 is open. Is used as a condition.

In order to increase the reliability of the judgment, it is preferable to determine that the evaporated gas is reliquefied when two or more conditions are satisfied. For example, the opening rate of the first decompression device 600 or the second decompression device 610 is preferable. The first set value or more, the seventh valve 570 or the tenth valve 571 is open, the second valve 520 is open, the level of the liquefied gas in the gas-liquid separator 700 is the second In the case of more than the set value, it can be determined that the boil-off gas is reliquefied, and the alarm can be activated.

The first set value, which is the opening degree of the first decompression device 600 or the second decompression device 610, may be about 1% to 4%, preferably about 2% to 3%, more preferably about May be 2%.

■ The boil-off gas reliquefaction system of the present invention includes two compressors 200 and 210 installed in parallel as shown in FIG. 7, and a plurality of first pressure reducing devices installed in series as shown in FIG. When a plurality of second pressure reducing device 610 installed in series with 600 is connected in parallel

Whether the opening rate of any one of the plurality of first pressure reducing devices 600 installed in series or any of the plurality of second pressure reducing devices 610 installed in series is equal to or greater than the first set value, the seventh valve 570, or If one or more of the following conditions are satisfied: whether the tenth valve 571 is open, the second valve 520 is open, and the level of the liquefied gas inside the gas-liquid separator 700 is greater than or equal to the second set value, evaporation occurs. It can be determined that the gas is reliquefaction.

When the first compressor 200 is used, the condition is whether the seventh valve 570 is open or not, and when the second compressor 210 is used, the tenth valve 571 is open. Is used as a condition.

In order to increase the reliability of the judgment, it is preferable to determine that the evaporated gas is reliquefied when two or more conditions are satisfied. For example, any one of a plurality of first pressure reducing devices 600 installed in series or in series The opening ratio of any one of the plurality of installed second pressure reducing devices 610 is equal to or greater than the first set value, the seventh valve 570 or the tenth valve 571 is open, and the second valve 520 is opened. In this state, when the level of the liquefied gas inside the gas-liquid separator 700 is equal to or greater than the second set value, it can be determined that the boil-off gas is reliquefied, and the alarm can be activated.

The first set value, which is the opening degree of the first decompression device 600 or the second decompression device 610, may be about 1% to 4%, preferably about 2% to 3%, more preferably about May be 2%.

② Alarm generation stage

When the alarm is activated, an alarm is generated when the condition that can be regarded as the time to remove the lubricant is satisfied.

When it can be seen that it is time to remove the lubricating oil, as described above, if the 'temperature difference of the low temperature flow' is more than normal and the condition is maintained for a certain time, the 'temperature difference of the high temperature flow' is normal It can be regarded as a case where more than one condition is satisfied and the condition that lasts more than a certain time, and the condition that the pressure difference of the high-temperature flow path is more than normal and that the condition lasts longer than a certain time is satisfied. It is desirable to determine whether to remove condensed or solidified lubricants by using two or more of 'temperature difference in low temperature flow', 'temperature difference in high temperature flow', and 'pressure difference in high temperature flow path'. .

For example, the smaller of the 'temperature difference of the low temperature flow' and 'temperature difference of the high temperature flow' lasts for more than the first predetermined time or longer than the third set value, or the 'pressure difference of the high temperature flow path' is the fourth set value. If the above state continues for more than the first set time, an alarm may be triggered to indicate when the condensed or solidified lubricant should be removed.

The third setpoint may be 30 ° C. to 40 ° C., preferably 33 ° C. to 37 ° C., and more preferably 35 ° C. In addition, the fourth set value may be twice or more than normal, and may be 150 kPa to 250 kPa, preferably 180 kPa to 220 kPa, and more preferably 200 kPa. The first setting time may be 1 hour.

In the present invention, an abnormality in the performance of the heat exchanger, generation of an alarm, and the like may be determined by appropriate control means. As a control means for determining the abnormality of the heat exchanger, the occurrence of an alarm, the control means used in the evaporation gas reliquefaction system of the present invention, preferably a vessel to which the evaporation gas reliquefaction system of the present invention is applied or Control means that are used for offshore structures can be used, and control means installed separately to determine the abnormality of the heat exchanger, the occurrence of an alarm, or the like.

In addition, the utilization of the bypass line, the discharge of the lubricating oil, the fuel supply of the engine, the start or restart of the boil-off gas reliquefaction system, the opening and closing of various valves for them can be automatically or manually controlled by the control means.

2. Bypass line (BL)  When used to satisfy the suction pressure condition of the compressor 200 when the pressure inside the storage tank (T) is low

The storage tank (T) has a small amount of liquefied gas in the storage tank (T), or a small amount of evaporated gas generated due to a small amount of liquefied gas or a large amount of boil-off gas supplied to the engine for the propulsion of the vessel due to the speed of the vessel. In the case where the internal pressure of h) is low, a case in which the suction pressure condition at the front end of the compressor 200 required by the compressor 200 may not be satisfied may occur.

In particular, when the PCHE (DCHE) is applied to the heat exchanger 100, the PCHE has a narrow flow path, so that when the boil-off gas discharged from the storage tank T passes through the PCHE, the width of the pressure drop is large.

Conventionally, when the compressor 200 does not satisfy the suction pressure condition required, the recirculation valves 541, 542, 543, and 544 are opened to partially or all of the evaporated gas by the recirculation lines RC1, RC2, RC3, and RC4. Was recycled to protect the compressor 200.

However, if the suction pressure condition of the compressor 200 is satisfied in a manner of recirculating the boil-off gas, the amount of the boil-off gas compressed by the compressor 200 is reduced, so that the reliquefaction performance is reduced, and the engine This may not meet the required fuel consumption. In particular, if the engine does not satisfy the required fuel consumption, the operation of the ship is greatly impeded. Therefore, even when the internal pressure of the storage tank T is low, the engine is required while satisfying the suction pressure condition required by the compressor 200. There was an urgent need for a way to satisfy the fuel consumption.

According to the present invention, even if the internal pressure of the storage tank (T) is low, by utilizing the bypass line (BL) that was previously installed for the maintenance and repair of the heat exchanger (100) without installing additional additional equipment. The suction pressure condition required by the compressor 200 can be satisfied without reducing the amount of boil-off gas compressed by the 100.

According to the present invention, when the internal pressure of the storage tank (T) is a predetermined value or less, by opening the bypass valve 590, part or all of the boil-off gas discharged from the storage tank (T) is exchanged through the bypass line (BL) The machine 100 is bypassed and sent directly to the compressor 200.

The amount of the boil-off gas sent to the bypass line BL may be adjusted according to how much the pressure in the storage tank T is lower than the suction pressure condition required by the compressor 200. That is, by opening the bypass valve 590 and closing the first valve 510 and the second valve 520, all the evaporated gas discharged from the storage tank (T) may be sent to the bypass line (BL), the bypass valve ( 590, the first valve 510, and the second valve 520 are partially opened, and only a part of the boil-off gas discharged from the storage tank T is sent to the bypass line BL and the rest is sent to the heat exchanger 100. It may be. As the amount of boil-off gas bypassing the heat exchanger 100 through the bypass line BL increases, the pressure drop of the boil-off gas decreases.

By directing the evaporated gas discharged from the storage tank (T) to the compressor (200) by bypassing the heat exchanger (100), there is an advantage that the pressure drop can be minimized. Since the internal pressure of the storage tank T, the fuel consumption required by the engine, the amount of boil-off gas to be reliquefied, etc., whether the bypass line BL is used to reduce the pressure drop, and the storage tank ( How much of the boil-off gas from T) is to be sent to the bypass line BL.

For example, when the internal pressure of the storage tank (T) is below a certain value, and the vessel is operated at a certain speed or more, it may be determined that it is advantageous to reduce the pressure drop by using the bypass line BL. Specifically, when the pressure inside the storage tank (T) is 1.09 bar or less and the speed of the vessel is 17 knot or more, it may be determined that it is advantageous to reduce the pressure drop by using the bypass line (BL).

In addition, even if all the boil-off gas discharged from the storage tank (T) is sent to the compressor 200 through the bypass line BL, the suction pressure condition required by the compressor 200 may not be satisfied. Lines RC1, RC2, RC3 and RC4 are used to meet the suction pressure conditions.

That is, when the pressure in the storage tank (T) is lowered and thus the suction pressure condition required by the compressor 200 cannot be satisfied, conventionally, the compressor 200 is directly used by recirculation lines RC1, RC2, RC3, and RC4. On the other hand, according to the present invention, by utilizing the bypass line (BL) primarily to satisfy the suction pressure condition of the compressor 200, all the evaporated gas discharged from the storage tank (T) through the bypass line (BL) Recirculation lines RC1, RC2, RC3, and RC4 are used secondly when the suction pressure condition required by the compressor 200 cannot be satisfied even if it is sent to the compressor 200.

In order to meet the suction pressure condition of the compressor 200 through the recirculation lines (RC1, RC2, RC3, RC4) after utilizing the bypass line BL firstly, the recirculation valves 541, 542, 543, 544 are The pressure value that is the condition for opening the bypass valve 590 is set higher than the pressure value that is the opening condition.

Conditions for opening the recirculation valves 541, 542, 543, and 544 and opening the bypass valve 590 preferably use the shear pressure of the compressor 200 as a factor, but the internal pressure of the storage tank T is a factor. Can also be used.

The compressor 200 shear pressure may be measured by a third pressure sensor (not shown) installed in front of the compressor 200, and the pressure inside the storage tank T may be measured by a fourth pressure sensor (not shown). Can be.

On the other hand, the sixth supply line (L6) for discharging the gaseous boil-off gas separated by the gas-liquid separator 700, the first supply at the point after the bypass line (BL) branching from the first supply line (L1) In the case of joining the line L1, a part of the boil-off gas discharged from the storage tank T while preventing the pressure drop to some extent is used in the heat exchanger 100 as a refrigerant, the bypass valve 590 and the first valve. When the system is operated while both the 510 and the second valve 520 are opened, the gaseous boil-off gas separated by the gas-liquid separator 700 may be directly sent to the bypass line BL.

The temperature of the gaseous boil-off gas separated by the gas-liquid separator 700 is lower than the temperature of the boil-off gas discharged from the storage tank T and supplied to the heat exchanger 100, and separated by the gas-liquid separator 700. When the gaseous evaporated gas is directly sent to the bypass line BL, the cooling efficiency of the heat exchanger 100 may decrease, and at least a portion of the gaseous evaporated gas separated by the gas-liquid separator 700 may be a heat exchanger ( 100).

However, if the amount of boil-off gas generated in the storage tank (T) is less than the amount of boil-off gas required by the engine, it may not be necessary to reliquefy the boil-off gas, but it is necessary to re-liquefy the boil-off gas. If there is no need to supply a refrigerant to the heat exchanger 100, it is possible to send all the gaseous evaporated gas separated by the gas-liquid separator 700 to the bypass line (BL).

Therefore, in the present invention, the sixth supply line L6 is joined to the first supply line L1 at the point in front of the branch line where the bypass line BL branches from the first supply line L1. When the sixth supply line (L6) is joined to the first supply line (L1) in front of the branch point of the bypass line (BL), the gas state separated by the gas-liquid separator 700 and the evaporated gas discharged from the storage tank (T) After the boil-off gas is first joined at the front end of the branch line BL, it is sent to the bypass line BL and the heat exchanger 100 according to the opening ratio of the bypass valve 590 and the first valve 510, respectively. Since the flow rate of the boil-off gas is determined, it is easy to control the system, and it is possible to prevent the case where the gaseous boil-off gas separated by the gas-liquid separator 700 is directly sent to the bypass line BL.

Bypass valve 590, it is preferable that the reaction rate is faster than the conventional case so that the opening degree adjustment according to the pressure change of the storage tank (T) can be made quickly.

3 is a schematic diagram of a boil-off gas reliquefaction system according to a third preferred embodiment of the present invention.

The boil-off gas reliquefaction system of the third embodiment shown in FIG. 3 has a differential pressure instead of the first pressure sensor 910 and the second pressure sensor 920 compared to the boil-off gas reliquefaction system of the first embodiment shown in FIG. 1. There is a difference in that the sensor 930 is installed, the following description will be mainly focused on the difference. Detailed description of the same members as in the above-described boil-off gas reliquefaction system of the first embodiment is omitted.

The boil-off gas reliquefaction system of this embodiment, unlike the first embodiment, instead of the first pressure sensor 910 and the second pressure sensor 920, the third supply line (L3) in front of the heat exchanger (100) It includes a differential pressure sensor 930 for measuring the pressure difference between the pressure of the fourth supply line (L4) and the rear end of the heat exchanger (100).

By the differential pressure sensor 930, it is possible to find out the 'difference in pressure of the high temperature flow path', and as in the first embodiment, among the 'difference in pressure of the high flow path', 'temperature difference in low temperature flow' and 'temperature difference in high temperature flow'. One or more may be used as an indicator to determine whether to remove condensed or solidified lubricants.

The present invention is not limited to the above embodiments, and various modifications or changes may be made without departing from the technical spirit of the present invention, which will be apparent to those of ordinary skill in the art. It is.

T: Storage tank BL: Bypass line
SL: Fuel supply line OL: Lubricant discharge line
NL: nitrogen supply line 100: heat exchanger
200, 210: Compressor 300: Oil separator
410, 420: oil filter 550: non-return valve
590: bypass valve 583: nitrogen valve
600, 610: pressure reducing device 620: isolation valve
700: gas-liquid separator 910, 920: pressure sensor
930: differential pressure sensor 940: water level sensor
810, 820, 830, 840: Temperature sensor
L1, L2, L3, L4, L5, L6, L7, L8: Supply Line
RC1, RC2, RC3, RC4: Recirculation Line
541, 542, 543, 544: Recirculation Valve
210, 220, 230, 240, 250: cylinder
211, 221, 231, 241, 251: cooler
510, 520, 530, 560, 570, 571, 581, 582: valve

Claims (9)

The evaporated gas generated in the LNG storage tank is compressed by a compressor, and the compressed evaporated gas is cooled by heat exchange with the evaporated gas before being compressed in a heat exchanger, and the fluid cooled by heat exchange is decompressed by a decompression device. A method of draining lubricant in a reliquefaction system,
The heat exchanger is a microchannel heat exchanger,
The compressor includes at least one oil-filled cylinder,
The boil-off gas compressed by the compressor includes a lubricating oil, the boil-off gas containing the lubricating oil is introduced into the microchannel heat exchanger, and the lubricating oil is condensed or solidified during the reliquefaction process.
Determining whether to remove the condensed or solidified lubricant in the heat exchanger,
Alarm activation step; And
Alarm generating step; including,
And determining by the alarm whether to remove the condensed or solidified lubricant in the heat exchanger. The method according to claim 1,
In the alarm activating step, if the opening degree of the decompression device is equal to or greater than a first set value, it is determined that the system is reliquefying the boil-off gas and activates an alarm. The method according to claim 1,
The pressure reducing device is installed in plurality in series and / or parallel,
In the alarm activating step, if the opening ratio of any one or more of the plurality of pressure reducing devices is equal to or greater than a first set value, the system determines that the system is reliquefying boil-off gas and activates an alarm. The method according to claim 1,
The boil-off gas compressed by the compressor is used as the fuel of the engine, and the system re-liquefies the remaining compressed boil-off gas supplied to the engine fuel,
In the alarm activating step, it is determined that all of the compressed boil-off gas is supplied to the fuel of the engine so as not to re-liquefy the boil-off gas without excess compressed boil-off gas. The method according to claim 1,
In the alarm activation step,
If it is not possible to use the equipment of the system, it is determined that the liquefied gas is not liquefied. The method according to claim 1,
By the gas-liquid separator installed in the rear of the decompression device, the liquefied liquefied gas and the boil-off gas remaining in the gas state is separated
In the alarm activating step, if the liquefied gas level of the gas-liquid separator is greater than or equal to the second set value, the system determines that the system is re-liquefying the boil-off gas, and activates the alarm. The method according to any one of claims 1 to 6,
On the line through which the boil-off gas used as the refrigerant in the heat exchanger is discharged, a second valve is installed.
In the alarm activating step, if the second valve is open, the system determines that the system is reliquefying boil-off gas, and activates the alarm. The method according to any one of claims 1 to 6,
In the alarm generation step,
A condition in which the 'temperature difference of low temperature flow' of the heat exchanger is more than normal and the state lasts for a predetermined time;
A condition in which the 'temperature difference of the high temperature flow' of the heat exchanger is greater than normal and the state lasts for a predetermined time; And
A condition in which the 'difference in pressure of the high temperature flow path' of the heat exchanger is greater than normal and the state lasts for a predetermined time; When any one or more of the above is satisfied, an alarm is generated. The method according to claim 8,
In the alarm generation step,
The smaller value of the 'temperature difference of the low temperature flow' of the heat exchanger and the 'temperature difference of the high temperature flow' of the heat exchanger is maintained for more than a first predetermined time or more than a third set value, or the pressure difference of the high temperature flow path. And the alarm is generated when 'is equal to or greater than a fourth set value and longer than the first set time.

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