KR20160096564A - Apparatus for retreating boil off gas - Google Patents

Abstract

Disclosed is an apparatus for treating a boil-off gas. The apparatus for treating the boil-off gas according to an embodiment of the present invention includes: a boil-off gas supply line providing the boil-off gas in a storage tank to a boil-off gas consuming unit; a compression part which is comprised in the boil-off gas supply line, and pressurizes the boil-off gas; a re-liquefaction line which is branched from the boil-off gas supply line, and re-liquefies the boil-off gas flowing by being branched; a re-liquefaction expansion part which expands the boil-off gas flowing into the re-liquefaction line while being comprised in the re-liquefaction line; and a heat exchanging part which exchanges heat between the boil-off gas passing through the re-liquefaction expansion part and the boil-off gas at a front of the compression part of the boil-off supply line. The re-liquefaction expansion part is prepared to make different expansion of the boil-off gas flowing by being branched from the boil-off gas supply line, and is prepared to control pressure of the boil-off gas entering the heat exchanging part.

Description

[0001] APPARATUS FOR RETREATING BOIL OFF GAS [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative gas processing apparatus, and more particularly, to an evaporative gas processing apparatus for re-liquefying evaporative gas generated in a storage tank.

* Due to the strengthening of IMO regulations on the emission of greenhouse gases and various air pollutants, shipbuilding and marine industries have replaced natural fuels such as heavy oil and diesel as natural fuels, Gas is used more often.

Natural gas, which is widely used and regarded as an important resource in fuel gas, is mainly composed of methane. Natural gas is cooled to about -162 degrees Celsius for ease of storage and transportation, and its volume is reduced to 1 (Liquefied Natural Gas), which is a colorless transparent cryogenic liquid reduced to 600/600.

Such liquefied natural gas is contained in a storage tank installed in an insulated manner on the hull and stored and transported. However, since it is virtually impossible to completely contain the liquefied natural gas, the external heat is continuously transferred to the inside of the storage tank, so that the evaporated gas generated by the vaporization of the liquefied natural gas is accumulated inside the storage tank.

Such evaporated gas may increase the internal pressure of the storage tank to cause deformation and destruction of the storage tank, so that it is necessary to suppress the generation of evaporated gas or to treat and remove the evaporated gas.

Conventionally, evaporation gas is flowed into a vent mast provided on the upper side of a storage tank, or a method of burning evaporation gas by using a GCU (Gas Combustion Unit) has been used. However, this is undesirable from the viewpoint of energy efficiency, and there is a risk of fire and explosion in burning the evaporative gas.

Therefore, there is a need for a method that can efficiently utilize and process the evaporated gas, and easily supply the evaporated gas to the fuel gas of the ship.

Published Patent Publication No. 10-2014-0027233 (published on April 03,

An embodiment of the present invention is intended to provide an evaporative gas processing apparatus capable of effectively re-liquefying evaporated gas.

According to an aspect of the present invention, there is provided an evaporation gas supply system comprising: an evaporation gas supply line for supplying evaporation gas in a storage tank to evaporation gas consumption means; A compression unit provided in the evaporation gas supply line and pressurizing the evaporation gas; A re-liquefaction line for re-liquefying the evaporated gas which branches off from the evaporation gas supply line and is branched and flows; A heat exchange unit for exchanging heat between the redistribution line and the evaporation gas supply line; A re-liquefied expansion part provided in the re-liquefaction line to expand the evaporation gas before entering the high-temperature liquefaction line; And a heat exchange unit for exchanging heat between the evaporative gas passing through the re-liquefied expansion unit and the evaporation gas at the upstream side of the compression unit of the evaporation gas supply line, wherein the re-liquefied expansion unit has a degree of expansion So that the pressure of the evaporating gas entering the heat exchanging unit can be adjusted.

An expansion valve for reducing the pressure of the evaporated gas passing through the heat exchanger, and a gas-liquid separator for separating the evaporated gas, which has been re-liquefied through the expansion valve, into a gas component and a liquid component.

Liquid separator; a recovery line for supplying an evaporation gas of the liquid component separated from the gas-liquid separator to the storage tank; and a recovery line for separating the evaporation gas of the gas component separated from the gas- And may further be provided with a recirculation line for supplying to the supply line.

The re-liquefied expansion part may be provided to reduce the evaporation gas flowing from the evaporation gas supply line to 50 to 160 bar.

The evaporation gas processing apparatus according to the embodiment of the present invention can reduce the temperature range to be cooled by the heat exchanging unit and reduce the size of the heat exchanging unit by reducing the pressure and cooling the evaporating gas entering the heat exchanging unit.

Further, by reducing the pressure difference between the two fluids exchanging heat in the heat exchange unit, the heat exchanger can be manufactured at a lower cost.

Also, by reducing the flow rate of the flash gas generated due to the non-re-liquefaction, it is possible to reduce the flow rate of the fluid flowing through the heat exchanging unit, thereby reducing the size of the heat exchanging unit.

For this reason, the flow rate of the fluid flowing through the compression section can be reduced to reduce the size of the compression section.

For this reason, the energy consumed by the compression unit can be reduced.

On the other hand, the liquefaction rate does not decrease in spite of the above effect.

Therefore, a more compact and economical evaporative gas processing apparatus can be provided.

1 is a conceptual diagram showing an evaporative gas processing apparatus according to a first embodiment of the present invention.
2 is a conceptual diagram showing an evaporative gas processing apparatus according to a second embodiment of the present invention.
3 is a graph showing a correlation between the mass flow rate of the evaporating gas entering the compression section and the energy required in the compression section according to the pressure of the evaporation gas entering the heat exchange section.
4 is a graph showing a correlation between the mass flow rate of evaporative gas re-liquefied according to the mass flow rate of the evaporative gas required in the evaporative gas consumption means.
5 is a graph showing a correlation between the mass flow rate of the evaporation gas flowing into the compression section and the mass flow rate of the evaporation gas flowing into the compression section according to the mass flow rate of the evaporation gas consumed in the evaporation gas consumption means.
6 is a graph showing a correlation between energy required in the compression unit according to the mass flow rate of the evaporation gas required in the evaporation gas consumption means.
FIGS. 7 and 8 are graphs showing the correlation of the mass flow rate of the flash gas with the pressure of the evaporating gas entering the heat exchanger.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided to fully convey the spirit of the present invention to a person having ordinary skill in the art to which the present invention belongs. The present invention is not limited to the embodiments shown herein but may be embodied in other forms. For the sake of clarity, the drawings are not drawn to scale, and the size of the elements may be slightly exaggerated to facilitate understanding.

An evaporative gas treating apparatus according to an embodiment of the present invention can be used in an offshore structure. Offshore structures include liquefied gas transporting liquefied gas, as well as various vessels capable of propelling or developing liquefied gas as fuel. Also, any type of liquefied gas that can be used as fuel can be included in the offshore structure of the present invention. Examples include ships such as LNG carriers, LNG RVs, and offshore plants such as LNG FPSO and LNG FSRU.

In addition, the offshore structure according to the embodiment of the present invention can use liquefied gas having reduced volume by pressurizing and cooling natural gas. Natural gas is mainly composed of methane, and may include ethane, propane, butane, and the like. The composition of natural gas may vary depending on the place of production.

1 is a conceptual diagram showing an evaporative gas processing apparatus 100 according to a first embodiment of the present invention.

Referring to FIG. 1, an evaporative gas processing apparatus 100 according to a first embodiment of the present invention includes an evaporation gas supply line (not shown) for supplying evaporation gas generated from a storage tank 110 to evaporation gas consumption means 11 and 12, A liquefaction line 130 for re-liquefying a part of the evaporation gas passing through the evaporation gas supply line 120 and a liquefaction line 130 for supplying liquefied gas of the storage tank 110 to the evaporation gas consumption means 11, And a gas supply line 140.

In the following examples, liquefied natural gas and evaporation gas generated therefrom are used as an example to help understand the present invention. However, the present invention is not limited thereto, and various liquefied gases such as liquefied ethane gas and liquefied hydrocarbon gas, The same technical idea should be understood in the same way.

The evaporation gas supply line 120 is a flow path for supplying the evaporation gas generated from the storage tank 110 to the evaporation gas consumption means 11 and 12.

One end of the evaporation gas supply line 120 is connected to the inside of the storage tank 110 and the other end thereof is connected to the liquefied gas supply line 140 to be described later and connected to the evaporation gas consumption means 11 and 12 do. The evaporation gas supply line 120 may be disposed on the upper side of the interior of the storage tank 110 so that the inlet side end thereof can be supplied with the evaporation gas inside the storage tank 110.

The storage tank 110 is provided to receive or store the liquefied natural gas and the evaporated gas. The storage tank 110 may be provided with a membrane-type cargo hold that is heat-treated to minimize vaporization of liquefied natural gas due to external heat penetration. The storage tank 110 stores the liquefied natural gas and the evaporation gas in a stable manner until the liquefied natural gas is received from the production site of the natural gas, The power generation engine of the present invention can be used as a fuel gas.

The storage tank 110 can be maintained at an internal pressure of 1 bar to maintain the liquefied natural gas in a liquid state or at a pressure higher than that in view of fuel supply conditions and to maintain the internal temperature at -163 degrees or less .

Since the storage tank 110 is generally installed in a heat-treated state, it is practically difficult to shut off the intrusion of external heat completely. Therefore, there is an evaporative gas generated by naturally vaporizing the liquefied natural gas in the storage tank 110 do. Such evaporated gas may raise the internal pressure of the storage tank 110 and may damage or destroy the storage tank 110. Therefore, there is a need to remove or treat the evaporated gas from the storage tank 110. [

The evaporation gas generated in the storage tank 110 is consumed by the evaporation gas consumption means 11 and 12 by the evaporation gas supply line 120 as in the embodiment of the present invention or by the evaporation gas consumption means 11 and 12 by the refueling line 130 Re-liquefied and re-supplied to the storage tank 110.

Alternatively, although not shown in the drawings, the evaporation gas may be additionally treated or consumed by supplying evaporation gas to a vent mast (not shown) or a gas-combus- tion unit (GCU) (not shown) provided at an upper portion of the storage tank 110 have. However, in the offshore structure according to the embodiment of the present invention, instead of consuming the evaporation gas, the evaporation gas is supplied to the evaporation gas consumption means 11 and 12 to efficiently use the evaporation gas, while the excess evaporation gas is remelted to the storage tank 110 Can be returned.

Although one storage tank 110 is shown in the figure, this is merely for convenience, and the number and types of storage tanks 110 may be variously provided.

The evaporation gas consumption means 11 and 12 include an engine, a generator, a turbine, and the like. The evaporation gas can be used as a raw material or can be used to produce energy or the like. The engine using the evaporation gas as a raw material can receive the fuel such as the liquefied natural gas and / or the evaporated gas stored in the storage tank 110 to generate the propulsion force of the ship or generate the electric power for power generation such as internal equipment of the ship .

For example, the engine may include a DFDE engine capable of generating an output at low pressure (about 5-8 bar), an X-DF engine capable of generating output at medium pressure fuel gas (about 15-20 bar) An ME-GI engine capable of generating an output with fuel gas (about 150 to 300 bar), and the like. However, the present invention is not limited thereto, and it should be equally understood that various numbers of engines and various kinds of engines are used.

The evaporation gas consumption means 11 and 12 shown in the first embodiment of the present invention include a first consumption means 11 using high pressure natural gas and a second consumption means 12 using a middle pressure or low pressure natural gas . In one example, the first consumption means 11 may be an ME-GI engine and the second consumption means 12 may be a DFDE engine.

The evaporation gas processing apparatus 100 according to the first embodiment of the present invention includes a compression unit 121 provided in the evaporation gas supply 120 to pressurize and cool the evaporation gas. The compression unit 121 may be provided on the evaporation gas supply line 120 at a position upstream of the branch point of the re-liquefaction line 130, which will be described later, to pressurize the evaporation gas. However, if necessary, the compression unit 121 may be provided at the rear end of the point where the liquid refilling line 130 is branched.

The compression unit 121 may include a compressor 121a for compressing the evaporated gas and a cooler 121b for cooling the evaporated gas whose temperature has risen during the compression process.

At this time, the compression unit 121 may be provided in multiple stages. That is, it may include a multi-stage compressor 121a and a cooler 121b provided between the compressors 121a. On the other hand, some of the coolers 121b may be omitted, and include a cooler 121b provided after the last compressor 121a.

1, the compression unit 121 is composed of the three-stage compressor 121a and the condenser 121b. However, this is merely an example, and the pressure conditions required by the evaporation gas consumption means 11, The configuration of the compressor 121a and / or the cooler 121b constituting the compression unit 121 may vary depending on the temperature of the compressor 121a.

On the other hand, as described above, the first consuming means 11 to the second consuming means 12 may require different fuel conditions. For example, the first consumption means 11 may use natural gas of high pressure as a raw material and the second consumption means 12 may use a natural gas of low pressure as a raw material. At this time, the compression section 121 provided in a multi-stage can pressurize and cool the evaporation gas and adjust the pressure and temperature conditions required by the consumption means 11, 12.

Further, a heat exchanging unit 132 of a re-liquefaction line 130, which will be described later, may be installed at a front end of the compression unit 121 on the evaporation gas supply line 120, and a detailed description thereof will be described later.

The evaporation gas supply line 120 may include a high pressure evaporation gas supply line 122 and a low pressure evaporation gas supply line 123. The high-pressure evaporation gas supply line 122 is connected to the downstream end of the compression section 121 and connected to the first consumption means 11. [ Since the evaporation gas supplied to the first consumption means 11 through the high pressure evaporation gas supply line 122 is in a state of being compressed at a high pressure while passing through the compression section 121 having the multi stage compressor 121a, It is possible to provide the evaporation gas in a state required by the first consumption means 11 using as a raw material.

The low-pressure evaporation gas supply line 123 is branched at the middle of the compression section 121 and connected to the second consumption means 12. [ Since the evaporation gas supplied to the second consumption means 12 through the low pressure evaporation gas supply line 123 passes only a part of the compressor 121a, the evaporation gas is branched from the low pressure state required by the second consumption means 12 .

On the other hand, the point where the low-pressure evaporation gas supply line 123 is branched may be provided differently from the drawing. That is, depending on the pressure and temperature conditions of the evaporation gas required by the second consumption means 12, the low-pressure evaporation gas supply line 123 may be branched at a middle point of the compression section 121 provided in multiple stages .

On the other hand, the high-pressure evaporation gas supply line 122 may include a first opening / closing valve 122a, and the low-pressure evaporation gas supply line 123 may include a second opening / closing valve 123a. The first on-off valve 122a can regulate opening and closing of the high-pressure evaporation gas supply line 122 so as to be opened when the first consumption means 11 is operated. The second on-off valve 123a can control the opening and closing of the low-pressure evaporation gas supply line 123 so as to be opened when the second consumption means 12 is operated.

The re-liquefaction line (130) includes a re-liquefied expansion part (131) for expanding the high-pressure evaporation gas branched from the evaporation gas supply line (120), a heat exchanging part Liquid separator 134 that receives the re-liquefied evaporated gas passing through the evaporator 132, the heat exchanger 132, and the vaporized gas of the liquid component separated from the gas-liquid separator 134 is supplied again to the storage tank 110 Liquid separator 134 and a recycle line 136 for supplying the vaporized gas of the gaseous component separated in the recovery line 135 and the gas-liquid separator 134 to the storage tank 110 or the evaporation gas supply line 120.

The re-liquefaction line 130 can return the remaining evaporation gas that has not been consumed by the first consumption means 11 and the second consumption means 12 to the storage tank 110 after re-liquefaction. That is, the evaporated gas may be decompressed and cooled through the re-liquefaction line 130 to be phase-changed into liquefied gas, and then returned to the storage tank 110.

The redistribution line 130 may be branched from the evaporation gas supply line 120. For example, between the rear end of the compression section 121 and the first opening / closing valve 122a.

A three-way valve (not shown) may be provided at a point where the liquid refill line 130 and the evaporation gas supply line 120 are branched and the three-way valve may be supplied to the first consumption means 11 or the liquid refining line 130 It is possible to control the supply amount of the evaporating gas. The three-way valve may be manually operated by the operator to adjust the opening / closing degree and the opening / closing degree, or may be automatically implemented by a control unit (not shown).

On the other hand, unlike the drawing, the re-liquefaction line 130 may be branched from the middle of the compression section 121. Alternatively, the re-liquefaction line 130 may include a first re-liquefaction line (not shown) that branches from the rear end of the compression section 121 and a second re-liquefaction line (not shown) that branches from the middle of the compression section 121 . On the other hand, the first redistribution line and the second redistribution line may be introduced into the storage tank 110 or may be introduced into the storage tank 110 after merging into one flow path. In the latter case, since the pressures of the evaporative gases passing through the first re-liquefaction line and the second re-liquefaction line are different from each other, the pressure of the evaporation gas passing through each re-liquefaction line can be adjusted equally (Not shown) may be further provided.

The re-liquefied expansion part (131) can reduce the pressure by expanding the evaporated gas compressed at the high pressure by the compression part (121). Although the expansion valve is shown as an example of the re-liquefied expansion part 131 in the drawing, the re-liquefied expansion part 131 may be provided by various devices capable of reducing the pressure of the evaporation gas.

The heat exchanging unit 132 may be provided to exchange heat between the evaporated gas passing through the re-liquefied expansion unit 131 and the decompressed gas and the evaporated gas before the compressed unit 121 passing through the evaporated gas supply line 120. The evaporated gas that has passed through the re-liquefied expansion part 131 is pressurized as it passes through the compression part 121 and the temperature rises. Therefore, the low-temperature evaporation gas before passing through the compression part 121 of the evaporation gas supply line 120 The evaporation gas passing through the refueling line 130 can be cooled by heat exchange with each other.

In this way, since the evaporated gas that has passed through the re-liquefied expansion portion 131 and is decompressed can be cooled by heat exchange with the evaporated gas passing through the evaporated gas supply line 120 without any additional cooling device, unnecessary waste of power can be prevented The facility operation efficiency can be improved.

The heat exchanging unit 132 exchanges the evaporation gas passing through the re-liquefaction line 130 with the evaporation gas of the evaporation gas supply line 120, The device may also be cooled. As an example, a cooling device using liquefied nitrogen may be used to cool the evaporative gas passing through the refueling line 130.

The heat exchanging unit 132 may further utilize a separate cooling unit in addition to heat exchange with the evaporating gas in the evaporating gas supplying line 120 to cool the evaporating gas passing through the refilling line 130.

The evaporation gas flowing along the re-liquefaction line 130 can be re-liquefied while passing through the re-liquefied expansion part 131 and the heat exchange part 132. [ At this time, the re-liquefaction of the evaporation gas includes the re-liquefaction of the whole amount and the re-liquefaction of only part of the evaporation gas.

The evaporation gas is re-liquefied as the temperature falls, and some evaporation occurs in the decompression process of the re-liquefied evaporation gas. In order to inject the gas into the storage tank 110, the evaporation gas must be depressurized. However, when the evaporation gas is liquefied and then decompressed, the amount of vaporization of the liquefied evaporation gas may increase. Therefore, it is preferable to perform both the decompression and the cooling in accordance with appropriate temperature and pressure conditions.

Since the evaporation gas flowing along the re-liquefaction line 130 is reduced while passing through the re-liquefied expansion part 131 and is cooled while passing through the heat exchange part 132, the re-liquefaction occurs.

The gas-liquid separator 134 receives the partially re-liquefied evaporated gas while passing through the re-liquefied expansion part 131 and the heat exchanging part 132 to separate the liquid component and the gas component of the re-liquefied evaporated gas. Most of the evaporated gas is re-liquidified while the pressurized evaporated gas is decompressed and cooled. In this process, flash gas is generated, and gas components of the re-liquefied evaporated gas may be generated.

The liquid component of the re-liquefied evaporated gas separated by the gas-liquid separator 134 is supplied again to the storage tank 110 by the recovery line 135 to be described later, and the gas component of the separated re- And may be provided to the storage tank 110 or the evaporation gas supply line 120 by the recycle line 136.

The recovery line 135 may connect the gas-liquid separator 134 and the storage tank 110 so as to re-supply the liquid component of the evaporated gas separated by the gas-liquid separator 134 to the storage tank 110. The recovery line 135 may be provided with an inlet side end connected to the lower side of the gas-liquid separator 134 and an outlet side end connected to the inside of the storage tank 110. The recovery line 135 may be provided with an on-off valve (not shown) for regulating the supply amount of the re-liquefied evaporated gas recovered to the storage tank 110.

The recycle line 136 is connected to the gas-liquid separator 134 and the storage tank (not shown) so as to re-supply the gaseous components of the re-liquefied evaporated gas separated by the gas-liquid separator 134 to the storage tank 110 or the evaporation gas supply line 120 110 or the gas-liquid separator 134 and the evaporation gas supply line 120, as shown in FIG. Although the recirculation line 136 is shown to re-supply the gas component in the gas-liquid separator 134 to the upstream side of the compression section 121 on the evaporation gas supply line 120, the recirculation line 136 is also connected to the gas- The gas component in the separator 134 is supplied again from the gas-liquid separator 134 to the storage tank 110 or is supplied to the evaporation gas supply line 120 and the storage tank 110 together.

The liquefied gas supply line 140 may be provided to supply liquefied natural gas stored in or stored in the storage tank 110 to an engine, a generator, and / or a turbine.

The figure shows the liquefied gas supply line 140 supplying liquefied natural gas to the evaporation gas consumption means 11, 12. However, this is an example, and the liquefied gas supply line 140 may be provided to supply liquefied natural gas to a device separate from the evaporation gas consumption means 11, 12.

Hereinafter, the liquefied gas supply line 140 is connected to the first consumption means 11 and the second consumption means 12, respectively. At this time, the first consumption means 11 and the second consumption means 12 will be described by taking the engine as an example.

One end of the liquefied gas supply line 140 is connected to the inside of the storage tank 110 and the other end of the liquefied gas supply line 140 is joined to the evaporation gas supply line 120 to be connected to the engines 11 and 12 . The inlet side end of the liquefied gas supply line 140 may be disposed below the interior of the storage tank 110 and a delivery pump 141 may be provided to supply liquefied natural gas to the engines 11 and 12 .

As described above, the engines 11 and 12 include a first engine 11 for generating a relatively high-pressure fuel gas and generating an output, and a second engine 12 for generating an output by receiving a relatively low- The liquefied gas supply line 140 is connected to the second liquefied gas supply line 140b and the first liquefied gas supply line 140b so as to process the liquefied natural gas in accordance with the fuel gas requirements of the respective engines 11 and 12, (140a).

The first liquefied gas supply line 140a can supply the liquefied natural gas delivered by the delivery pump 141 to the first engine 11 that receives the relatively high-pressure fuel gas and generates an output. To this end, the first liquefied gas supply line 140a may be provided with a pressurizing pump 142 for compressing liquefied natural gas. The pressurizing pump 142 may compress the liquefied natural gas according to the pressure condition of the fuel gas required by the first engine 11. For example, when the first engine 11 is an ME-GI engine, The liquefied natural gas 142 can be supplied by compressing the liquefied natural gas under a pressure of about 250-300 bar. The liquefied natural gas compressed by the pressurizing pump 142 may be supplied as fuel gas to the first engine 11 after being forcedly vaporized through the vaporizer 143 and then joined with the evaporation gas supply line 120.

On the other hand, when the maintenance of the pressurizing pump 142 is required, or when the power is shut off due to the load being applied to the pressurizing pump 142, when the power supply of the pressurizing pump 142 is shut off at once, There is a possibility that the pressure pump 142 may be damaged or a safety accident may occur due to the influence of the pump 142 or other components. Further, there may be a case where maintenance of the pressurizing pump 142 is required, or the pressurizing pump 142 is required to shut off the power by increasing the load, but the continuous operation of the engine may be required.

For this purpose, a bypass line 140c may be provided in the first liquefied gas supply line 140a. The inlet side end of the bypass line 140c is connected to the front end of the pressurizing pump 142 on the first liquefied gas supply line 140a and the outlet end is connected to the pressurizing pump 142 on the first liquefied gas supply line 140a. And a separate pressurization pump 142 may be additionally provided so that the pressurization pump 142 may be connected in parallel.

Since the plurality of pressurizing pumps 142 are provided in parallel on the first liquefied gas supply line 140a by the bypass line 140c having the separate pressurizing pump 142, ) And other constitutional failures and safety accidents can be prevented, and the engine can be operated continuously for a long time.

The second liquefied gas supply line 140b can supply the liquefied natural gas delivered by the delivery pump 141 to the second engine 12 that receives the relatively low-pressure fuel gas and generates an output. The liquefied natural gas is compressed to a low pressure (about 3 bar to 5 bar) in the process of delivering the liquefied natural gas. Therefore, when the second engine 12 is a DFDE engine, The vaporizer 144 can forcibly vaporize the liquefied natural gas sent by the feed pump 141 and supply the fuel gas to the fuel condition required by the second engine 12. [

A vapor-liquid separator 145 may be provided at the downstream of the vaporizer 144. When the second engine 12 is a DFDE engine, the fuel gas must be supplied in a gaseous state to generate a normal output and to prevent engine failure. The liquid natural gas that has passed through the vaporizer 144 is supplied to the gas-liquid separator 145 and only the gaseous fuel gas is supplied from the gas-liquid separator 145 to the second engine 12, It is possible to improve the reliability.

The apparatus 100 for treating an evaporative gas according to an embodiment of the present invention having such a structure can effectively treat and manage the evaporative gas and can have an effect of improving the energy efficiency by making efficient use of the evaporative gas.

2 is a conceptual diagram showing an evaporative gas processing apparatus 101 according to a second embodiment of the present invention.

2, the evaporation gas processing apparatus 101 according to the second embodiment of the present invention includes an expansion valve (not shown) provided on the liquid refining line 130 and configured to reduce the pressure of the evaporation gas that has passed through the heat exchanging unit 132 133). The same reference numerals as those shown in FIG. 1 denote the same components as those of the evaporative gas processing apparatus 100 according to the first embodiment, and a duplicate description will be omitted.

The expansion valve 133 may be provided at the rear end of the heat exchanging part 132. The expansion valve 133 can further cool and expand the evaporation gas that has passed through the re-liquefied expansion portion 131 and the heat exchange portion 132 to improve the re-liquefaction efficiency. As an example, the expansion valve 133 may use a Joule-Thomson valve. The Thomson-Thomson valve refers to a valve that uses a throttling effect when the fluid is expanded when there is no production or heat transfer. Thus, the evaporated gas cooled while passing through the heat exchanging part 132 is adiabatically expanded and cooled while passing through the expansion valve 133, in which re-circulation of the whole or part of the evaporated gas may occur.

Hereinafter, efficiency of the evaporative gas processing apparatuses 100 and 101 according to the embodiment of the present invention will be described with reference to FIGS. 3 to 8. FIG.

3 shows the mass flow rate (Mc) of the evaporating gas entering the compression unit 121 according to the pressure Pb (pressure before BOG) of the evaporating gas entering the heat exchanging unit 132 and the mass flow rate (Energy: Energy Compressor) that is required in the present invention.

3, the mass flow rate Mc of the evaporation gas entering the compression section 121 and the energy (amount of energy) supplied from the compression section 121 Ec) is changed. At this time, when the pressure Pb of the evaporating gas entering the heat exchanging unit 132 is the optimum pressure Pb1, the mass flow rate Mc of the evaporating gas entering the compressing unit 121 and the mass flow rate The energy Ec required is minimized. That is, when the pressure Pb of the evaporating gas entering the heat exchanging unit 132 is smaller than the optimal pressure Pb1, the mass flow rate Mc of the evaporating gas entering the compressing unit 121 and the energy When the pressure Pb of the evaporating gas entering the heat exchanging unit 132 is larger than the optimum pressure Pb1, the mass flow rate Mc of the evaporating gas entering the compressing unit 121 and the mass flow rate The energy Ec consumed by the heat exchanger 121 becomes large.

The pressure Pb of the evaporating gas entering the heat exchanging unit 132 is adjusted to the optimal pressure Pb1 to reduce the mass flow rate Mc of the evaporating gas entering the compressing unit 121, It is possible to reduce the size of the heat exchanger 121b and lower the cost of the facility. Therefore, a more compact and economical evaporative gas processing apparatus can be manufactured.

The efficiency of the evaporative gas processing apparatus can be improved by adjusting the pressure Pb of the evaporating gas entering the heat exchanging unit 132 to the optimum pressure Pb1 to lower the energy Ec required in the compressing unit 121 . That is, the energy used for compressing the evaporation gas can be lowered while maintaining the same pressure at the downstream end of the compression section 121.

4 to 6, the effect of reducing the pressure Pb of the evaporating gas entering the heat exchanging unit 132 will be described.

4 is a view showing a mass flow of a re-liquefied BOG (Mr) to be re-liquefied according to a mass flow of the evaporation gas (Mf) consumed in the evaporation gas consumption means (11, 12) In the graph of FIG.

Referring to FIG. 4, the mass flow rate Mr of the evaporative gas re-liquefied according to the mass flow rate Mf of the evaporation gas consumed by the consumption means 11, 12 is changed. At this time, the mass flow rate Mf of the evaporation gas consumed in the consuming means 11 and 12 is in inverse proportion to the mass flow rate Mr of the evaporation gas re-liquefied. That is, as the mass flow rate Mf of the evaporation gas consumed in the consumption means 11, 12 increases, the mass flow rate Mr of the evaporation gas to be re-liquefied decreases.

On the other hand, the pressure Pb of the evaporating gas entering the heat exchanging part 132 is reduced through the re-liquefying expansion part 131. The pressure at the front end of the re-liquefying expansion part 131 is Pb1, And the pressure at the rear end of the pipe 131 is Pb2, the relationship of Pb1 > Pb2 is established.

Referring again to FIG. 4, it can be seen that the mass flow rate Mr of the evaporative gas to be re-liquefied is constant regardless of the depressurization of the evaporative gas at the re-liquefied expansion part 131. That is, lowering the pressure Pb of the evaporating gas entering the heat exchanging unit 132 through the re-liquefied expansion unit 131 does not lower the re-liquefaction rate.

5 is a graph showing the correlation between the mass flow rate Mc of the evaporation gas entering the compression section 121 and the mass flow rate Mf of the evaporation gas consumed in the evaporation gas consumption means 11 and 12.

5, the mass flow rate Mc of the evaporating gas entering the compression section 121 varies depending on the mass flow rate Mf of the evaporation gas consumed by the consumption means 11, 12. At this time, the mass flow rate Mf of the evaporation gas consumed in the consuming means 11, 12 is in inverse proportion to the mass flow rate Mc of the evaporation gas entering the compression section 121. That is, as the mass flow rate Mf of the evaporation gas consumed by the consumption means 11, 12 increases, the mass flow rate Mc of the evaporation gas entering the compression portion 121 decreases.

5, the pressure Pb of the evaporating gas entering the heat exchanging unit 132 is reduced from P1 to P2, and the mass flow rate Mc of the evaporating gas entering the compressing unit 121 decreases. . That is, by reducing the pressure Pb of the evaporation gas by using the re-liquefied expansion portion 131 and reducing the mass flow rate Mc of the evaporation gas entering the compression portion 121, the compressor 121a and the cooler 121b It is possible to reduce the size of the apparatus and lower the cost of the equipment. Therefore, a more compact and economical evaporative gas processing apparatus can be manufactured.

6 is a graph showing a correlation between energy (Ec) consumed in the compression section 121 according to the mass flow rate Mf of the evaporation gas required in the evaporation gas consumption means (11, 12).

Referring to FIG. 6, the energy Ec consumed by the compression unit 121 varies according to the mass flow rate Mf of the evaporation gas consumed by the consumption means 11, 12. At this time, the mass flow rate Mf of the evaporation gas consumed by the consuming means 11 and 12 and the energy Ec consumed by the compression unit 121 are in inverse proportion to each other. That is, as the mass flow rate Mf of the evaporation gas consumed by the consumption means 11, 12 increases, the energy Ec consumed by the compression unit 121 decreases.

Referring again to FIG. 6, it can be seen that the pressure (Pb) of the evaporating gas entering the heat exchanging part 132 is reduced from P1 to P2, and the energy (Ec) consumed by the compressing part 121 decreases. That is, the efficiency of the evaporative gas processing apparatus can be improved by reducing the pressure Pb of the evaporation gas by using the re-liquefied expansion unit 131 and lowering the energy Ec consumed by the compression unit 121. That is, the energy used for compressing the evaporation gas can be lowered while maintaining the same pressure at the downstream end of the compression section 121.

7 and 8 are graphs showing the correlation of the mass flow of flash gas (Mg) according to the pressure Pb of the evaporating gas entering the heat exchanging unit 132. The graph of FIG. 7 shows the case where the content of N2 contained in the evaporated gas is a mole%, and the graph of FIG. 8 shows the case where the content of N2 contained in the evaporated gas is b%. At this time, a relationship of a < b is established.

As the mass flow rate Mg of the flash gas decreases, the mass flow rate Mc of the evaporation gas entering the compression section 121 decreases. Therefore, the size of the compression unit 121 can be reduced, and the energy Ec consumed by the compression unit 121 can be reduced.

The mass flow rate (Mg) of the flash gas depends on the pressure (Pb) of the evaporating gas entering the heat exchanging part (132). At this time, the mass flow rate Mg of the flash gas generated when the pressure Pb of the evaporating gas entering the heat exchanging unit 132 is the optimum pressure Pb1 is minimized. That is, the mass flow rate Mg of the flash gas generated when the pressure Pb of the evaporating gas entering the heat exchanging unit 132 is smaller than the optimum pressure Pb1 increases, and the evaporation gas entering the heat exchanging unit 132 Even when the pressure Pb of the gas is greater than the optimum pressure Pb1, the mass flow rate Mg of the flash gas is increased.

Accordingly, the mass flow rate Mg of the flash gas generated by adjusting the pressure Pb of the evaporating gas entering the heat exchanging unit 132 to the optimum pressure Pb1 can be reduced.

The amount of flash gas generated depends not only on the pressure but also on the temperature. That is, as the pressure drops, the liquefied gas is vaporized to form a flash gas, and as the temperature rises, the liquefied gas vaporizes to form a flash gas.

If the pressure Pb of the evaporating gas entering the heat exchanging part 132 is smaller than the optimum pressure Pb1, the amount of flash gas generated by the reduced pressure is reduced. On the contrary, the temperature lowering degree of the heat exchanging part 132 is reduced So that the amount of generated flash gas is increased. Since the temperature lowering of the heat exchanging part 132 occurs simultaneously with the pressure reducing process, the temperature lowering degree also decreases when the degree of pressure reduction is small.

On the other hand, if the pressure Pb of the evaporating gas entering the heat exchanging part 132 is larger than the optimal pressure Pb1, the temperature is lowered considerably because the degree of vacuum is sufficient. However, So that the total amount of generated flash gas is increased.

7 and 8, it can be seen that the optimum pressure Pb1 that minimizes the mass flow rate Mg of the flash gas varies with the content of N2. That is, as the component content of N2 becomes larger (a <b), the optimum pressure Pb1 also becomes larger.

The N2 component content of the evaporative gas is related to the amount of liquefied natural gas stored in the storage tank 110. [ The content of N2 is large in the case of a high-speed voyage in which the amount of stored liquefied natural gas stored in the storage tank 110 is large.

However, the evaporation gas is continuously generated over time, and the consumption amount of evaporative gas or liquefied natural gas consumed by the evaporative gas consumption means 11, 12 also increases, so that the storage amount of the liquefied natural gas stored in the storage tank 110 . In the case of such a colliery navigation, the content of N2 becomes smaller.

On the other hand, the content of N2 decreases sharply in the early stage of the generation of the evaporation gas but decreases to a gentle slope after the evaporation gas is generated to some extent. The component content of N2 is generally between 0 mole% and 10 mole%. The pressure (about 300 bar) at the front end of the re-liquefaction expansion part 131 is adjusted to a value between a minimum of 50 bar and a maximum of 160 bar according to the content of N 2.

For example, when the content of N2 is 10 mole%, the optimum pressure Pb1 is about 140 to 160 bar. Accordingly, the pressure (about 300 bar) at the front end of the re-liquefied expansion part 131 is adjusted to about 150 bar. Also, when the content of N2 is 0 mole%, the optimum pressure Pb1 is about 50 bar to 70 bar. Accordingly, the pressure (about 300 bar) at the front end of the re-liquefied expansion part 131 is adjusted to about 60 bar.

As described above, the storage amount of the liquefied natural gas stored in the storage tank 110 varies, and the optimal pressure Pb1 that can minimize the generation amount of the flash gas fluctuates. Therefore, it is necessary to adjust the degree of depressurization by the re-liquefied expansion part 131 to meet the fluctuating optimum pressure Pb1.

The evaporation gas processing apparatuses 100 and 101 according to the embodiment of the present invention include a sensor 141 installed in the evaporation gas supply line 120 to measure the flow rate of the evaporation gas entering the compression unit 121, A sensor 142 installed in the evaporation gas supply line 120 so as to measure the flow rate of the evaporation gas generated in the storage tank 110 and entering the heat exchange unit 132; And a sensor 143 installed in the recycle line 136 to measure the flow rate of the flash gas joining the gas supply line 120. The positions of the sensors 141, 142, and 143 may be different from those of the drawings.

The flow rate of the flash gas can be measured not only by the sensor 143 installed in the recirculation line 136 but also by the sensors 141 and 142 installed in the evaporation gas supply line 120. It can be determined that the amount of flash gas generated is increased when the measured amount of any one of the sensors 141, 142, and 143 increases.

The re-liquefied expansion part (131) may be provided to adjust the degree of decompression. That is, when the evaporation gas of the same pressure is introduced, the pressure of the evaporation gas flowing into the heat exchange unit 132 through the re-liquefaction expansion unit 131 may be different. Therefore, the flow rate of the flash gas can be adjusted by controlling the pressure of the evaporative gas that has passed through the re-liquefied expander 131. [

Specifically, if the flow rate of any one of the sensors 141, 142, and 143 increases when the degree of depressurization of the re-liquefied expansion part 131 is increased, the pressure Pb of the evaporated gas entering the heat exchange part 132, It is judged that the direction has been changed to a direction away from the optimum pressure Pb1 and the degree of decompression of the re-liquefied expansion part 131 is reduced. Conversely, if the flow rate of one of the sensors 141, 142, and 143 decreases when the degree of depressurization of the re-liquefied expansion part 131 is increased, the pressure Pb of the evaporative gas entering the heat exchanging part 132 becomes optimum It is determined that the direction has been changed to a direction approaching the pressure Pb1 and the degree of pressure reduction of the re-liquefied expansion portion 131 is continuously increased.

This control method can be similarly applied when the degree of decompression of the re-liquefied expansion part 131 is reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, You will understand. Accordingly, the true scope of the invention should be determined only by the appended claims.

100: Evaporative gas treatment device, 110: Storage tank,
120: evaporation gas supply line, 121: compression section,
130: Re-liquefaction line, 131: Re-liquefied expansion part,
132: heat exchanger, 133: expansion valve,
134: gas-liquid separator, 135: recovery line,
136: recirculation line, 140: liquefied gas supply line,
141: delivery pump, 142: pressure pump,
143: Carburetor.

Claims (4)

An evaporation gas supply line for supplying evaporation gas in the storage tank to evaporation gas consumption means;
A compression unit provided in the evaporation gas supply line and pressurizing the evaporation gas;
A re-liquefaction line for re-liquefying the evaporated gas which branches off from the evaporation gas supply line and is branched and flows;
A heat exchange unit for exchanging heat between the redistribution line and the evaporation gas supply line;
A re-liquefied expansion part provided in the re-liquefaction line to expand the evaporation gas before entering the high-temperature liquefaction line; And
And a heat exchange unit for exchanging heat between the evaporated gas passing through the re-liquefied expansion unit and the evaporation gas before the compression unit of the evaporation gas supply line,
Wherein the re-liquefied expansion unit is provided to vary the degree of expansion of the evaporation gas that branches off from the evaporation gas supply line and is capable of controlling the pressure of the evaporation gas entering the heat exchange unit. The method according to claim 1,
An expansion valve for reducing the pressure of the evaporation gas passing through the heat exchange unit; and a gas-liquid separator for separating the vaporized gas passed through the expansion valve and re-liquefied into a gas component and a liquid component. 3. The method of claim 2,
Liquid separator; a recovery line for supplying an evaporation gas of the liquid component separated from the gas-liquid separator to the storage tank; and a recovery line for separating the evaporation gas of the gas component separated from the gas- Further comprising a recirculation line for supplying the feed gas to the feed line. The method according to claim 1,
Wherein the re-liquefied expansion portion is provided to reduce the evaporation gas flowing from the evaporation gas supply line to 50 to 160 bar.

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