KR102305886B1 - A Treatment System of Gas - Google Patents

Abstract

A gas processing system according to an embodiment of the present invention includes: a hold unit for accommodating a liquefied gas storage tank; and an insulation line for supplying boil-off gas generated from the liquefied gas storage tank to the inside of the hold part.

Description

A Treatment System of Gas

The present invention relates to a gas treatment system.

According to recent technology development, liquefied gas such as liquefied natural gas (Liquefied Natural Gas) and liquefied petroleum gas (Liquefied Petroleum Gas) is widely used to replace gasoline or diesel.

Liquefied natural gas is liquefied by cooling and liquefying methane obtained by refining natural gas collected from a gas field. It is a colorless and transparent liquid with few pollutants and high calorific value. On the other hand, liquefied petroleum gas is a fuel made into a liquid by compressing the gas containing propane (C3H8) and butane (C4H10) together with petroleum from oil fields at room temperature. Liquefied petroleum gas, like liquefied natural gas, is colorless and odorless and is widely used as fuel for household, business, industrial, and automobile use.

Such liquefied gas is stored in a liquefied gas storage tank installed on the ground or stored in a liquefied gas storage tank provided in a ship that is a means of transportation to navigate the ocean. The volume of liquefied petroleum gas is reduced to 1/260 of propane and 1/230 of butane by liquefaction, which has the advantage of high storage efficiency.

Such liquefied gas is supplied and used by various sources of demand. Recently, an LNG fuel supply method in which LNG is used as a fuel in an LNG carrier that transports liquefied natural gas to drive an engine has been developed. The method used is being applied to ships other than LNG carriers.

However, the temperature and pressure of the liquefied gas required by a consumer such as an engine may be different from the state of the liquefied gas stored in the liquefied gas storage tank. Therefore, in recent years, continuous research and development has been made on a technology for supplying a liquefied gas to a customer by controlling the temperature and pressure of the liquefied gas stored in a liquid state.

In particular, the liquefied gas stored in the liquefied gas storage tank is not supplied to the liquefied gas demander but can be transported simply stored in a liquefied gas carrier. If it accumulates inside the tank, there is a risk that the internal pressure of the tank may rise, so there is a risk of an increase in the manufacturing cost of a ship by installing an expensive tank that can withstand high pressure. It is necessary to reduce the amount of generation of

The present invention was created to improve the prior art, and an object of the present invention is to control the boil-off gas generated in a liquefied gas storage tank, and use the boil-off gas as an insulating gas to reduce the load on the re-liquefaction apparatus. to provide a system.

A gas processing system according to an embodiment of the present invention includes: a hold unit for accommodating a liquefied gas storage tank; and an insulation line for supplying boil-off gas generated from the liquefied gas storage tank to the inside of the hold part.

Specifically, it may further include a boil-off gas line discharged from the liquefied gas storage tank and connected to be introduced into the liquefied gas storage tank.

Specifically, a boil-off gas compressor provided on the boil-off gas line to pressurize the boil-off gas discharged from the liquefied gas storage tank; and a re-liquefaction device for liquefying the boil-off gas discharged from the boil-off gas compressor.

Specifically, the heat insulation line may be branched from the boil-off gas line and connected to the hold part.

Specifically, it may further include a heat insulating gas supply unit for supplying the heat insulating gas to the heat insulating space.

Specifically, a first BOG sensing unit for detecting the amount of BOG discharged from the liquefied gas storage tank; a second boil-off gas detection unit for detecting a ratio of the boil-off gas introduced into the insulating space; and adjusting the opening degree of the boil-off gas line or the insulation line according to the amount of boil-off gas detected by the first boil-off gas detection unit, and the ratio of the boil-off gas detected by the second boil-off gas detection unit is less than or equal to the explosive concentration. It may further include a control unit for adjusting the opening degree of the insulation line so as to be.

The gas treatment system according to the present invention can reduce the manufacturing cost of the liquefied gas storage tank by controlling the boil-off gas generated in the liquefied gas storage tank and preventing the pressure of the liquefied gas storage tank from rising by re-liquefying the boil-off gas. have.

In addition, the present invention can increase the insulation efficiency through the boil-off gas that forms a cryogenic temperature in comparison with nitrogen by introducing the boil-off gas naturally generated in the liquefied gas storage tank into the insulation space and using it as a heat insulating gas.

In addition, the present invention can reduce the load on the re-liquefaction apparatus because the BOG can be diverted to the adiabatic space without introducing all of the BOG into the re-liquefaction apparatus. Since it can be introduced into the space, fuel wastage can be prevented.

1 is a view showing a ship installed with a gas processing system according to an embodiment of the present invention.
2 is a diagram conceptually illustrating a gas processing system according to an embodiment of the present invention.
3 is a diagram illustrating a path through which BOG is re-liquefied and recovered in the gas processing system according to an embodiment of the present invention.
4 is a diagram illustrating a path through which boil-off gas is supplied to an insulating space in the gas processing system according to an embodiment of the present invention.
5 is a flowchart illustrating a gas processing method according to an embodiment of the present invention.

The objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments taken in conjunction with the accompanying drawings. In the present specification, in adding reference numbers to the components of each drawing, it should be noted that only the same components are given the same number as possible even though they are indicated on different drawings. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a view showing a ship in which a gas processing system according to an embodiment of the present invention is installed, FIG. 2 is a diagram conceptually showing a gas processing system according to an embodiment of the present invention, and FIG. 3 is the present invention is a view showing a path through which BOG is re-liquefied and recovered in the gas treatment system according to an embodiment of the present invention, and FIG. It is the drawing shown.

1 to 4 , the gas treatment system 100 according to an embodiment of the present invention includes a liquefied gas storage tank 110 , a boil-off gas line 120 , a boil-off gas compressor 130 , and a re-liquefaction apparatus ( 140 ), a holding unit 150 , a heat insulating line 160 , a heat insulating gas supply unit 170 , and a control unit 180 .

The liquefied gas storage tank 110 may be provided in the hull 11 forming a double-bottom structure, and may store liquid cargo. Here, the liquid cargo may be a liquefied gas such as liquefied natural gas (Liquefied Natural Gas), liquefied petroleum gas (Liquefied Petroleum Gas), and the like.

Hereinafter, in the present specification, liquefied gas, which is a liquid cargo, may be used to encompass all gas fuels that are generally stored in a liquid state, such as LNG or LPG, ethylene, ammonia, etc. For convenience, it can be expressed as liquefied gas. This can be applied to boil-off gas as well. In addition, for convenience, LNG can be used to encompass both NG (Natural Gas) in a liquid state as well as NG in a supercritical state. have.

The liquefied gas storage tank 110 should store the liquid cargo in a liquid state. In this case, the liquefied gas storage tank 110 may have a pressure tank shape. The internal pressure of the liquefied gas storage tank 110 may be adjusted by discharging BOG through the BOG line 120 and re-liquefying the discharged BOG or using it as an insulating gas, which will be described later.

And the liquid cargo stored in the liquefied gas storage tank 110 may be a transport or fuel to be supplied to a liquefied gas demand (not shown). Here, the liquefied gas demander may be driven through the boil-off gas and flash gas supplied from the liquefied gas storage tank 110 to generate power. In this case, the liquefied gas demand is a high-pressure engine, and may be a gas fuel engine (eg, MEGI). Alternatively, the liquefied gas demander may be a dual fuel engine in which boil-off gas or oil is selectively supplied without mixing and supplying boil-off gas and oil.

In this embodiment, a general technique for supplying liquefied gas from the liquefied gas storage tank 110 to a liquefied gas demander may be applied, and detailed description thereof is replaced with a known technique and detailed description thereof will be omitted.

And the support 20 may be provided at the lower portion of the liquefied gas storage tank 110 so that the liquefied gas storage tank 110 can be supported inside the hull 11 . Such a support 20 can reduce the horizontal and vertical movement of the liquefied gas storage tank 110 .

In addition, a general bunkering line 111 is provided in the liquefied gas storage tank 110 to supply liquefied gas to the liquefied gas storage tank 110 , and the bunkering line 111 is directly connected to the liquefied gas storage tank 110 . Or it may be provided by being joined to the boil-off gas line 120 . In addition, a vent line 112 may be provided in the liquefied gas storage tank 110 to vent the boil-off gas in an emergency. A valve may be provided in each of the bunkering line 111 and the vent line 112 to control the flow rates of liquefied gas and boil-off gas.

In addition to the supply of liquefied gas from the liquefied gas storage tank 110 to the liquefied gas demanding destination, the boil-off gas generated in the liquefied gas storage tank 110 of this embodiment may be recovered to the liquefied gas storage tank 110, and recovery Reliquefaction may occur during the process.

The liquefied gas stored in the liquefied gas storage tank 110 may not be supplied to a liquefied gas demander, but may be transported in a simply stored state in a liquefied gas carrier. At this time, the liquefied gas inside the liquefied gas storage tank 110 is naturally evaporated, so that the boil-off gas is accumulated in the liquefied gas storage tank 110 , thereby increasing the internal pressure of the tank.

Unlike the case where liquefied gas is supplied to liquefied gas demanders, if there is no discharge path, an expensive tank must be used to achieve a stable structure of the liquefied gas storage tank 110 due to the rise in internal pressure of the liquefied gas storage tank 110, but this In the embodiment, the boil-off gas is re-liquefied through the configuration of the boil-off gas line 120 and the insulation line 160 or used as a heat insulating gas to prevent the internal pressure of the liquefied gas storage tank 110 from rising while reducing the boil-off gas. By reducing the amount of venting to the outside, it is possible to reduce fuel wastage.

In addition, when liquefied gas stored in a separate liquefied gas storage tank (not shown) is used as fuel, the liquefied gas is moved from the liquefied gas storage tank 110 to a separate liquefied gas storage tank in consideration of the operation logic. liquefied gas can be redistributed.

The BOG line 120 is a line through which BOG is recovered, and BOG is discharged from the liquefied gas storage tank 110 and is connected to be introduced into the liquefied gas storage tank 110 . That is, the outlet through which BOG is discharged from the liquefied gas storage tank 110 is formed at one end of the BOG line 120 , and the inlet through which the BOG is recovered and flows into the liquefied gas storage tank 110 is BOG. The other end of the line 120 is formed.

Here, the boil-off gas line 120 is formed to extend toward the bottom of the liquefied gas storage tank 110 , and may include a plurality of outlets 121 . The plurality of outlets 121 are provided to be immersed in the liquefied gas stored in the liquefied gas storage tank 110, so that the recovered BOG is mixed with the liquefied gas, so that the BOG may be partially liquefied by the liquefied gas.

In addition, a plurality of valves (not shown) may be provided in the boil-off gas line 120 so that the amount of boil-off gas emission can be adjusted according to the control of the opening degree of the valves. At this time, the valve diverts or reduces the flow rate of BOG flowing to the reliquefaction device 140 so that the reliquefaction device 140 to be described later fails or a driving load can be reduced. can be adjusted

A boil-off gas compressor 130 is provided on the boil-off gas line 120 , and the boil-off gas compressor 130 pressurizes the boil-off gas discharged from the liquefied gas storage tank 110 . Here, the BOG compressor 130 does not pressurize BOG to supply BOG to a liquefied gas demanding destination, but pressurizes BOG for the ease of re-liquefaction of BOG. It does not have to be tailored to the state demanded by the consumer.

In addition, a reliquefaction device 140 may be provided downstream of the BOG compressor 130 on the BOG line 120 , and the reliquefaction device 140 liquefies BOG discharged from the BOG compressor 130 . can do it

Referring to FIG. 3 (refer to the solid line indicated by the boil-off gas line), the boil-off gas discharged from the liquefied gas storage tank 110 passes through the boil-off gas line 120 to the boil-off gas compressor 130 and the re-liquefaction device 140 . After being reliquefied via gas, it is recovered to the liquefied gas storage tank 110, and the reliquefied fuel may be in a state of reduced pressure as the state is changed from gas to liquid.

The holding unit 150 accommodates the liquefied gas storage tank 110 and forms an insulating space 151 surrounding the liquefied gas storage tank 110 to reduce the temperature transfer of the outside air.

For example, the hold part 150 forms a space in which the liquefied gas storage tank 110 is accommodated in the hull 11, and an insulating space ( 151), the inner surface of the hold part 150 and the liquefied gas storage tank 110 may be spaced apart.

The insulation line 160 supplies the boil-off gas generated from the liquefied gas storage tank 110 to the insulation space 151 . For example, the insulation line 160 may be branched from the boil-off gas line 120 and connected to the hold part 150 . Here, the thermal insulation line 160 may be branched upstream of the boil-off gas compressor 130 , and thus the boil-off gas may be supplied to the heat insulation space 151 without a change in the pressure of the boil-off gas.

Referring to FIG. 4 (refer to the solid line indicated by the insulation line), the boil-off gas discharged from the liquefied gas storage tank 110 is supplied to the insulation space 151 through the insulation line 160, and the boil-off gas is at a cryogenic temperature. Insulation efficiency can be improved, and since the boil-off gas in the gaseous state is not recovered to the liquefied gas storage tank 110 , it is possible to prevent the internal pressure of the liquefied gas storage tank 110 from rising.

The insulating gas supply unit 170 may supply the insulating gas to the insulating space 151 . Here, the insulating gas supplied from the insulating gas supply unit 170 may be, for example, nitrogen as an inert gas.

The insulating gas supply unit 170 may additionally supply insulating gas, such as when the temperature of the insulating space 151 is increased or the insulating gas is insufficient. 151 can be supplied, so that the inert gas storage capacity of the insulating gas supply unit 170 can be reduced, as well as the boil-off gas is at a cryogenic temperature, so that the thermal insulation efficiency can be improved.

The controller 180 can control the opening degree of the boil-off gas line 120 as well as the amount of heat insulating gas supplied from the heat insulating gas supply unit 170 and the degree of opening of the heat insulating line 160 , and control the opening degree of the discharge line 190 . can be adjusted

Here, a first BOG detection unit capable of detecting the amount of BOG discharged from the liquefied gas storage tank 110 so that the controller 180 can select and control the re-liquefaction or use of BOG as a heat insulating gas. (181) may be provided. For example, the first boil-off gas detection unit 181 is provided on the boil-off gas line 120 , and the controller 180 controls the re-liquefaction apparatus 140 according to the amount of boil-off gas discharged from the liquefied gas storage tank 110 . It is possible to selectively control the use of the reliquefaction or heat insulating gas in consideration of the load of the BOG line 120 or the opening degree of the heat insulating line 160 .

That is, by the controller 180 , the BOG may pass through the BOG compressor 130 or may be introduced into the adiabatic space 151 , and may be distributed to be simultaneously supplied to the BOG compressor 130 and the adiabatic space 151 . may be Here, the controller 180 may adjust the opening degree of the insulation line 160 so that the ratio of the boil-off gas detected by the second boil-off gas detection unit 182 is equal to or less than the explosive concentration. The control unit 180 allows the BOG to be introduced into the heat insulating space 151 to use the BOG as a heat insulating gas, but by limiting the amount of BOG mixed with the inert gas, it can be controlled to be less than the upper explosive limit concentration.

Here, the inert gas is not used as a fire source for generating an explosion, but the additionally supplied boil-off gas may be used as a fire source. However, when the inert gas and the boil-off gas are mixed in the adiabatic space 151 , the boil-off gas is scattered and thus the room for an explosion may be reduced.

And a pressure gauge 183 for sensing the pressure inside the insulating space 151 is provided, so that the controller 180 determines that the pressure value transmitted from the pressure gauge 183 is greater than or equal to the set pressure (which may be a preset pressure that the hold part withstands). can be prevented from forming. The controller 180 may discharge the gas inside the heat insulating space 151 through the discharge line 190 so that the pressure of the heat insulating space 151 is not formed above a set pressure.

Here, the gas discharged from the insulating space 151 through the discharge line 190 may be in a state in which inert gas and BOG are mixed, and the gas discharged in this way is vented to the outside, or nitrogen and BOG are separated. After that, it can be supplied to the consumer.

And the second BOG detection unit 182, which is not described, is configured to detect the ratio of BOG introduced into the heat insulating space 151, and the pressure gauge 183 detects the pressure inside the heat insulating space 151. configuration can be made.

As such, in this embodiment, by controlling the boil-off gas generated in the liquefied gas storage tank 110 and re-liquefying the boil-off gas, the pressure of the liquefied gas storage tank 110 can be limited to a pressure range that can be tolerated. In addition, by introducing the boil-off gas into the insulation space 151 and using it as an insulation gas, the insulation efficiency can be increased through the boil-off gas that forms a cryogenic temperature in preparation for nitrogen.

Hereinafter, a gas processing method for controlling the concentration of the holding unit 150 through the gas processing system 100 as described above will be described. The overlapping description of the same functions and actions according to the configuration of the above-described embodiments will be omitted.

5 is a flowchart illustrating a gas processing method according to an embodiment of the present invention.

As shown in FIG. 5 , in the gas processing method according to an embodiment of the present invention, the holding unit 150 is filled with an inert gas ( S10 ), and the concentration of fuel accumulated in the holding unit 150 is detected. and a step (S30) of supplying an inert gas when the fuel concentration inside the holding unit 150 rises (S20).

In step S10, the holding unit 150 is filled with an inert gas. As described above, the holding unit 150 is a configuration for insulating the liquefied gas storage tank 110 , and may reduce evaporation of fuel inside the liquefied gas storage tank 110 due to external temperature.

To this end, the holding unit 150 may be filled with a gas such as an inert gas having a low or no risk of explosion while having a low temperature. Gas filling in the holding unit 150 may be performed by the insulating gas supply unit 170 .

Here, the filling of the holding unit 150 so as not to cause a problem in the internal pressure increase of the holding unit 150 by the fuel leaking from the liquefied gas storage tank 110 or supplied with the boil-off gas from the liquefied gas storage tank 110 . The degree may be around 80% to 95%. However, the filling of the inert gas of the hold unit 150 is not limited thereto, and even when the inert gas is filled with 95% or more of the inert gas, when fuel or the like is introduced, the discharge line 190 may be opened through the control unit 180 . Various embodiments are possible as there are.

In step S20, the concentration of fuel accumulated in the holding unit 150 is sensed.

The ratio and concentration of the inert gas and fuel inside the holding unit 150 may be sensed in real time by the second BOG detection unit 182 , and the ratio and concentration of the BOG supplied through the insulation line 160 . In addition to the concentration ratio due to the increase of .

At this time, the second BOG detection unit 182 may detect a ratio of fuel and inert gas in the heat insulating space 151 of the hold unit 150 and transmit a signal to the control unit 180 , and the control unit 180 . can determine the crack of the liquefied gas storage tank 110 by excluding the amount of BOG supplied through the insulation line 160 from the increase in the concentration of fuel detected by the second BOG detection unit 182 .

Here, the control unit 180 may perform the steps described below to reduce the possibility of explosion, and may, of course, warn the crew or the like of fuel leakage.

In step S30 , an inert gas is supplied when the fuel concentration inside the holding unit 150 increases.

In order to reduce the risk of explosion by the boil-off gas supplied to the hold unit 150 or leaked, the control unit 180 controls the insulating gas supply unit 170 so that the fuel concentration below the upper explosive limit concentration is achieved with the hold unit 150 . Inert gas can be additionally supplied by controlling.

As such, this embodiment detects the crack of the liquefied gas storage tank 110 through the fuel concentration ratio inside the hold part 150, and controls the environment in which there is a possibility of explosion by additional supply of inert gas, so that the operator can use the liquefied gas It is possible to reduce the risk of work for treating the cracks of the storage tank 110, and to improve the insulation effect by using the fuel as an insulation gas.

Although the present invention has been described in detail through specific examples, this is for the purpose of describing the present invention in detail, and the present invention is not limited thereto, and by those of ordinary skill in the art within the technical spirit of the present invention. It will be clear that the transformation or improvement is possible.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

10: Ship 11: Hull
20: support 100: gas treatment system
110: liquefied gas storage tank 111: bunkering line
112: vent line 120: boil off gas line
121: outlet 130: boil-off gas compressor
140: re-liquefaction device 150: hold part
151: insulation space 160: insulation line
170: insulating gas supply unit 180: control unit
181: first boil-off gas detection unit 182: second boil-off gas detection unit
183: pressure gauge 190: discharge line

Claims (6)

a holding unit for accommodating the liquefied gas storage tank; and
and an insulating line for supplying boil-off gas generated from the liquefied gas storage tank to an insulating space formed between the liquefied gas storage tank and the hold part,
When the BOG naturally evaporated inside the liquefied gas storage tank is accumulated and the internal pressure of the liquefied gas storage tank is increased, the BOG is discharged to the outside to lower the internal pressure of the liquefied gas storage tank to a preset pressure range, Gas treatment system, characterized in that for injecting at least a portion of the boil-off gas to the heat insulation space through the insulation line. According to claim 1,
The gas treatment system further comprising a boil-off gas line discharged from the liquefied gas storage tank and connected to be introduced into the liquefied gas storage tank. 3. The method of claim 2,
a boil-off gas compressor provided on the boil-off gas line to pressurize the boil-off gas discharged from the liquefied gas storage tank; and
The gas treatment system further comprising a re-liquefaction device for liquefying the boil-off gas discharged from the boil-off gas compressor. According to claim 2, wherein the insulating line,
The gas processing system, characterized in that branched from the boil-off gas line and connected to the insulating space. 5. The method of claim 4,
Gas processing system, characterized in that it further comprises a heat insulating gas supply unit for supplying the heat insulating gas to the heat insulating space. 6. The method of claim 5,
Further comprising a control unit for adjusting the opening degree of the insulation line,
The control unit is
Insulating gas, which is an inert gas that is not used as a fire source for explosion, and BOG, which can be used as a fire source, are introduced into the heat insulation space, but limit the amount of BOG mixed with the inert gas to explode the heat insulation space. A gas processing system, characterized in that it is controlled below the upper limit concentration.

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