KR100726290B1 - Process and apparatus for recycling of boil off gas - Google Patents

Abstract

A process and an apparatus for recycling evaporation gas are provided to minimize waste of surplus evaporation gas by controlling liquefaction, re-liquefaction, or usage of the evaporation gas. A process and an apparatus for recycling evaporation gas includes the steps of liquefying the evaporation gas(S10), selectively retrieving liquefied gas including the evaporation gas to a gas storing tank or selectively supplying the liquefied gas to a liquefied gas evaporator by first and second control valves(S11), evaporating a determined amount of the liquefied gas in the liquefied gas evaporator suitable for supplying fuel by controlling temperature, pressure and flux regularly(S12), supplying the evaporated gas as the fuel of a propulsion system(S13), and retrieving the liquefied evaporation gas or opening/closing first, second, third, and forth valves for burning a little amount of the evaporation gas(S14).

Description

Process and apparatus for recycling of boil off gas}

1 is a block diagram of an apparatus for treating boil-off gas in a gas carrier using a general internal combustion engine propulsion system according to the first conventional technology.

2 is a block diagram of a boil-off gas treatment system according to the second conventional technology.

3 is a block diagram of a fuel supply and boil-off gas emergency treatment system in a ship using a dual fuel engine electric propulsion system according to the third conventional technology.

4 is a block diagram of an evaporative gas recycling apparatus according to a first embodiment of the present invention.

FIG. 5 is a block diagram of a boil-off gas recycling method realized by the boil-off gas recycling apparatus shown in FIG. 4.

6 is a graph of the liquid gas flow rate and the evaporation gas conversion ratio corresponding to the liquid gas.

7 is a block diagram of a boil-off gas recycling method according to a second embodiment of the present invention.

8 is a block diagram of an evaporative gas recycling apparatus according to a third embodiment of the present invention.

FIG. 9 is a block diagram of an evaporative gas recycling method realized by the evaporative gas recycling apparatus shown in FIG. 8.

<Description of the symbols for the main parts of the drawings>

100: gas storage tank 110: low pressure compressor

130: liquid gas vaporizer 180: boil-off gas sending line

181: liquid gas recovery line 182: liquid gas transfer line

183: vaporized gas supply line 184: gas emergency treatment line

185: liquid gas delivery line 189: boil-off gas bypass line

191-196: Control valve 200: Evaporative gas liquefier

300: propulsion system 301: boiler and steam turbine system

302: dual fuel engine electric propulsion system 303: gas turbine electric propulsion system

The present invention relates to a method and apparatus for recycling boil-off gas, and more particularly, to a ship such as a gas carrier carrying a liquefied natural gas, or a synthesis for mining, storing, purifying, liquefying and vaporizing a gas in a floating state on the sea. The present invention relates to a method and apparatus for recycling boil-off gas for boiled off gas (BOG) generated from a floating or stationary gas treatment plant equipped with a plant.

In general, liquefied natural gas (Liquefied Natural Gas) is known to be a clean fuel and abundant reserves than petroleum, and its use is rapidly increasing with the development of mining and transport technology.

LNG is a liquid that is produced when the temperature of methane, the main component of natural gas, is lowered below -162 degrees Celsius under 1 atmosphere. The volume of liquefied methane is about one-sixth of the volume of gaseous methane in the standard state. 0.42, about one-half of the oil share.

Because of this, LNG has the advantage of being easy to transport and store, while having a very low temperature and very dangerous in case of leakage, a separate gas storage tank made of insulation (insulation material) in ships or floating or fixed gas treatment facilities. Will be transported or stored.

In particular, LNG carriers are different from crude oil carriers because they are transported in a cryogenic liquid state at -162 ° C. Since the vaporization point of LNG is extremely low at -162 ° C, thorough insulation is required to prevent vaporization.

However, full insulation is practically impossible and the LNG in liquefied state is changing to gaseous evaporated gas at a rate of about 0.15% per day while the ship is in operation.

For this reason, ships have been used as a fuel of a propulsion engine naturally, or as a fuel such as a thermal oxidizer, which is a kind of simple incinerator that simply burns off excess evaporated gas.

For example, the propulsion engine generates high pressure steam from a boiler by using boil-off gas as a fuel, and the steam drives a steam turbine to obtain propulsion force.

In recent years, the dual fuel engine electric propulsion method and gas turbine electric propulsion method have been reviewed, or the dual fuel engine electric propulsion type ship is under construction and is expected to be expanded.

On the other hand, the evaporation gas in the ship is a problem that occurs constantly even when the ship does not need to operate or operate at a lower load.

For example, when a ship enters a terminal from the mountain, it should lower the operating speed to less than 7 knots and about 10 hours to wait for unloading at the terminal.

In this process, there is a problem in the way to handle the continuously generated evaporation gas. In addition, since the vessel in the atmosphere can not be connected to the terminal, there is no way to send out the excess boil-off gas or use the boil-off gas to energy.

Therefore, in ships using existing steam turbines, the steam is burned and the steam is generated in the boiler, and the generated steam is an ointment that cannot be used in the steam turbine. Process.

On the other hand, in case of using dual fuel engine electric propulsion method and gas turbine electric propulsion method, the surplus evaporation gas has to be treated in dual fuel engine or gas turbine, not boiler, but in this case, it also generates unnecessary electricity and several tens of megawatts. Using or dealing with surplus power is a very difficult problem.

With this condensed fuel, the excess boil-off gas is forcibly combusted by a thermal oxidizer and discharged to the atmosphere. In this process, flames and incompletely burned exhaust gases are released into the atmosphere, causing environmental problems and energy waste that emit carbon dioxide and nitrogen gas.

Referring to a specific example of such a conventional technology as follows.

1 shows an apparatus for treating boil-off gas in a gas carrier using a general internal combustion engine propulsion system according to the first conventional technology. Some of the LNG loaded in the cargo tank (1) (cargo tank) is naturally vaporized by the temperature change is converted into boil-off gas.

During the operation of the vessel, the boil-off gas is transferred to the boiler 3 through the low density compressor 2, and the boiler 3 vaporizes the cooling water in the steam state by using the heat of combustion generated while burning the boil-off gas.

The high temperature steam generated by the boiler 3 is supplied to the steam turbine 4 through the steam pipe to generate power required for the operation of the vessel, and is converted into low temperature steam while passing through the steam turbine 4. The low temperature steam is transferred to the condenser 5 to phase change into a low temperature liquid state, that is, condensate.

The condensate is transferred to the pump 6 through a pipe, and is re-supplied to the boiler 3 by pressurization of the pump 6 and regasified by the heat of combustion of the boil-off gas.

However, powering them all through the steam turbine 4 at the time of mooring or anchoring of a ship causes many problems.

Therefore, even though the boil-off gas is supplied to the boiler 3 and vaporized into hot steam, most of the hot steam except the amount of steam required for the idle operation of the steam turbine 4 is discharged from the main dump system 7. The temperature of the steam is reduced and then fed to the condenser 5.

Here, the main dump system 7 is a system for reducing the condensation load of the condenser 5, the structure to reduce the temperature of the steam by spraying the coolant directly to the steam transported through the pipe.

The condensed water phase-changed into a liquid state while passing through the condenser 5 is transferred to the pump 6, pressurized by the pump 6, and supplied again to the boiler 3.

The boil-off gas treatment apparatus of the gas carrier of the first conventional technology has a disadvantage that only a part of the boil-off gas can be used as the power of the vessel when the vessel is mooring or anchored in a port, and the rest is forcibly consumed in the boiler.

Figure 2 discloses a boil-off gas treatment system according to the second conventional technology.

The ship's boil-off gas treatment system includes an internal combustion engine including a fuel gas compressor 8, a gas turbine 12, and a dual fuel engine 11 connected to a bog vent hole at the top of the cargo tank 1. (10) and the like.

Here, the thermal oxidizer 9 is connected between the fuel gas compressor 8 and the internal combustion engine 10, and the evaporated gas delivered through the fuel gas compressor 8 is transferred by a predetermined pipe change means. It is coupled to be transferred to either the thermal oxidizer 9 or the internal combustion engine 10.

During operation of the vessel, the boil-off gas is sent to the internal combustion engine 10 to be used for propulsion, while if the vessel is not propelled by the internal combustion engine 10, the excess boil-off gas generated in the cargo tank 1 It is sent to the thermal oxidizer 9 so that it can be burned directly.

This boil-off gas treatment system of the second prior art also has the disadvantage of simply consuming excess boil-off gas in the thermal oxidizer 9.

FIG. 3 discloses a fuel supply and boil-off gas emergency treatment system in a ship using the dual fuel engine electric propulsion system according to the third conventional technology.

The vessel using the dual fuel engine electric propulsion system uses the pressurized gas by the pressurizing device 15 on the boil-off gas discharge line 14 as the fuel of the dual fuel engine electric propulsion system 11 '. At this time, the insufficient fuel during operation is directly supplied with LNG in the cargo tank (1 ').

To this end, the ship using the dual fuel engine electric propulsion system is a fuel discharge pipe 13 coupled to the cargo tank (1 '), and the first heater 17 is coupled to such a fuel discharge pipe 13 to receive the liquid gas And a vaporization gas supply line 19 that receives LNG vaporized by the first heater 17 through a vaporization gas discharge line 18 connected to the outlet side of the first heater 17. The dual fuel engine electric propulsion system 11 ′ is coupled to the vaporization gas supply line 19.

In addition, between the pressurization device 15 and the vaporization gas supply line 19, the combustion line 16, the second heater 20 and the thermal oxidizer 9 are connected.

When the vessel enters the terminal or is in the process of mooring, the boil-off gas is heated in the second heater 20 to increase the temperature suitable for combustion, and then forced combustion treatment is performed in the thermal oxidizer 9.

However, the above-described first, second, and third conventional technologies all have a problem that only a part of the boil-off gas naturally generated when the vessel is moored or anchored in a port can be used as the power of the vessel.

That is, a forced treatment that must be consumed through a boiler or a thermal oxidizer without forcibly reusing the surplus evaporated gas that cannot be used as fuel or power of a vessel among naturally occurring evaporated gases is required.

In this case, additional equipment is required according to the forced treatment, when forced consumption of the boil-off gas causes environmental problems such as exhaust gas emissions, there is also a problem that economic losses due to the consumption of energy of the boil-off gas.

The object of the present invention devised to solve these problems is to liquefy the boil-off gas and to process the liquid gas in the liquid gas vaporizer of the liquid gas transfer line, fuel pressure by maintaining a constant pressure, temperature and flow rate The present invention aims to provide an evaporative gas recycling method capable of efficiently supplying evaporated gas for use as a propellant fuel and solving energy waste problems such as simple consumption of surplus evaporated gas.

In addition, another object of the present invention is to efficiently remove excess evaporation gas when the propulsion force is lowered or not promoted, regardless of the temperature or amount of the evaporation gas that changes according to external environmental changes in the case of a vessel using the evaporation gas as fuel. To provide a boil-off gas recycling apparatus that can be controlled and processed by the present invention.

In addition, another object of the present invention, while operating at low load or terminal mooring of the vessel, does not incinerate the surplus evaporated gas to the forced combustion equipment, while instead of using an external additional cooling means, instead of using the liquid gas as its own cooling medium By performing a "temporary evaporative gas reliquefaction system control" that can be utilized for the reliquefaction of the boil-off gas, to provide an evaporative gas recycling method and recycling apparatus that can solve the energy waste problem during the operation or temporary mooring of the vessel.

In the present invention, the term "temporary evaporative gas liquefaction system control" means a process performed by a systematic system that can be temporarily applied only when the vessel enters a terminal or the like, or when low load propulsion.

In other words, after about 20 hours, the ship will return to normal operating conditions, and at this time, it will become a condition where the boil-off gas can be fully used as fuel, or LNG can be unloaded at the terminal. none. If LNG can be unloaded at the terminal, the boil-off gas will be sent to the terminal.

An object of the present invention as described above, in the evaporation gas recycling method for treating the evaporation gas generated in the gas storage tank, compressing the evaporation gas to liquefy by the liquid gas of the gas storage tank in the evaporation gas liquefier Liquefaction of the boil-off gas; Recovering the liquid gas containing the boil-off gas by the liquefaction step to the gas storage tank or selectively supplied to the gas storage tank corresponding to the full opening or closing size ratio of the first and second control valve Determining a fuel supply amount; Adjusting a vaporization factor for vaporizing the liquid gas of the amount determined by the determining step in a constant gas, vapor pressure, and flow rate so as to be suitable for fuel supply from the liquid gas vaporizer; A fuel supplying step of supplying the vaporized gas vaporized by the adjusting step to the fuel of the propulsion system; It is achieved by the method of recycling the boil-off gas, characterized in that it comprises an emergency response step of opening and closing the first to fourth control valve to liquefy all the boil-off gas to recover or incinerate a small amount.

In addition, another object of the present invention in the evaporation gas recycling apparatus for treating the evaporated gas generated in the gas storage tank, the liquid gas is supplied through the liquid gas sending line of the gas storage tank receiving the evaporated gas sending line of the gas storage tank A boil-off gas liquefier coupled to receive boil-off gas through; A liquid gas vaporizer coupled to the liquid gas conveying line to receive the liquid gas containing the boil off gas through the liquid gas conveying line of the boil off gas liquefier; It includes a liquid gas recovery line coupled between the liquid gas transfer line and the gas storage tank to recover the liquid gas of the boil-off gas liquefier, and evaporated to the vaporized gas, or vaporized gas through the vaporization gas supply line of the liquid gas vaporizer It is achieved by a boil-off gas recycling apparatus characterized in that to supply the mixed gas mixed gas to the propulsion system.

In addition, according to the present invention, the boil-off gas bypass line is further piped between the boil-off gas delivery line and the liquid-phase gas transfer line, and the fifth control valve of the boil-off gas delivery line and the sixth regulation of the boil-off gas bypass line According to the selective opening and closing of the valve, the boil-off gas is preferably supplied to the liquid gas transfer line.

In addition, in the description of the present invention, the boil-off gas will be described in two ways. Firstly, what is naturally generated inside the gas storage tank is called 'natural evaporation gas', and secondly,' compresses that the natural evaporated gas has a predetermined pressure (for example, about 5 to 10 atmospheres) while passing through the low pressure compressor. It can be referred to as 'evaporated gas,' and since all natural or compressed boil-off gas is boil-off gas, it can be understood simply as boil-off gas.

On the other hand, in the summary and the detailed description and the claims of the present invention, 'liquid gas' is to be understood as referring to liquid LNG, which is inherently liquid LNG, or liquefied evaporated gas in a state of supercooled below -162 degrees Celsius. will be.

In addition, various transfer lines are pipe members such as connecting pipes, tubes, large pipes, and the like, and the coupling of these transfer lines will be understood as a pipe and connected state penetrating for fluid transfer.

In addition, the fuel supplied to the propulsion system in the present invention is very diverse. For example, the fuel of the first embodiment is vaporized gas obtained by liquefying boil-off gas into liquid gas and vaporizing the remainder except liquid recovered gas in the liquid gas vaporizer.

In addition, the fuel of the second embodiment is a vaporized gas in which the liquid gas vaporizer 130 vaporizes the vaporized gas and the fuel supply liquid gas that simply pass through the vaporized gas liquefier so as not to liquefy.

The fuel of the third embodiment is a vaporized gas obtained by vaporizing a cold mixed gas obtained by mixing the liquid gas of the boil-off gas liquefier and the boil-off gas directly supplied through the boil-off gas bypass line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific and practical preferred embodiments of the present invention will be described with reference to the accompanying drawings.

First embodiment

4 is a block diagram of an evaporative gas recycling apparatus according to a first embodiment of the present invention, FIG. 5 is a block diagram of an evaporative gas recycling method realized by the evaporative gas recycling apparatus shown in FIG. 6 is a graph of the liquid gas flow rate and the evaporation gas conversion ratio corresponding to the liquid gas.

As shown in FIG. 4, the evaporative gas recycling apparatus according to the present invention is provided in a floating or stationary gas treatment facility having a comprehensive facility for mining, storing, purifying, liquefying and vaporizing a gas in a floating state on a ship or at sea. do.

The gas storage tank 100 of the evaporative gas recycling apparatus is a structure for storing LNG (hereinafter referred to as 'gas') to be transported in a ship, or mining, storing, purifying, liquefying and vaporizing gas in a floating state on the sea It is a structure for storing fluid in a floating or stationary gas treatment facility with a comprehensive facility.

The liquid gas delivery line 185 is a line for transmitting the liquid LNG (hereinafter referred to as 'liquid gas') from the gas storage tank 100 to the boil-off gas liquefier 200 in a state of supercooled below -162 degrees Celsius.

The liquid gas delivery line 185 is used for liquefying or reliquefying natural boil-off gas (BOG) as a self-cooling liquid gas in the gas storage tank 100 without using an additional cooling means. Liquid gas flows.

The liquid gas traveling in the liquid gas delivery line 185 is a self-cooling medium means used to liquefy the natural boil-off gas in the boil-off gas liquefier 200, or is a fuel required for operation of the vessel.

An extrusion pump 102 is coupled to the liquid gas sending line 185 so that the liquid gas stored in the gas storage tank 100 is pumped from the liquid gas sending line 185 to be sent to the boil-off gas liquefier 200.

One end corresponding to the suction port of the liquid gas delivery line 185 is disposed at an internal position of the gas storage tank 100 capable of sucking the liquid gas of the gas storage tank 100.

The other end of the liquid gas delivery line 185 is connected to the inlet side of the multi-pipe header 186 disposed in the inner space of the upper side of the boil-off gas liquefier 200 through the outer wall of the boil-off gas liquefier 200. A plurality of injection holes 187 are formed at the outlet side of the multi-pipe header 186.

The gas storage tank 100 is formed with an evaporation gas discharge hole 101 for discharging natural evaporation gas, and one end of the evaporation gas discharge line 180 is connected to the evaporation gas discharge hole 101.

The low pressure compressor 110 is installed in the boil-off gas sending line 180. The low pressure compressor 110 refers to a low pressure compression device for discharging the boil-off gas compressed to 5 to 10 atm after receiving the natural boil-off gas.

The other end of the boil-off gas sending line 180 having such a low pressure compressor 110 is connected to allow the compressed boil-off gas to flow into the boil-off gas liquefier 200.

The boil-off gas liquefier 200 has a space for mixing and heat-exchanging the liquid gas sent from the gas storage tank 100 and the boil-off gas compressed through the low pressure compressor 110 so as to liquefy the boil-off gas.

Liquid gas recovery line 181 means a return line for returning the remaining portion, except as necessary for the fuel supply to the gas storage tank (100).

Liquid gas recovery line 181 is branched from the liquid gas recovery line 182 is connected to recover the liquid gas to the gas storage tank (100).

The liquid gas transfer line 182 connected to the boil-off gas liquefier 200 corresponds to a line in which the liquid gas is transferred to the next step (eg, liquid gas recovery line or liquid gas vaporizer).

The first control valve 191 is piped to the liquid gas recovery line 181, the second control valve 192 is piped to the liquid gas transfer line 182. The first and second control valves 191 and 192 select a supply direction of the liquid gas flow amount (eg, the liquid gas recovery line direction or the liquid gas vaporizer direction) as necessary, or adjust the distribution ratio of the liquid gas flow rate. Each valve opening and closing is controlled by a conventional valve control logic circuit that performs the operation.

That is, when the first control valve 191 is opened and the second control valve 192 is closed, the liquid gas liquefied in the boil-off gas liquefier 200 is the gas storage tank 100 through the liquid gas recovery line 181 ) Is recovered.

On the other hand, when the first control valve 191 is closed and the second control valve 192 is opened, the liquid gas liquefied in the boil-off gas liquefier 200 through the liquid gas transfer line 182 through the liquid gas vaporizer ( 130).

The third and fourth control valves 193 and 194, including the first and second control valves 191 and 192, have an electromagnetic valve type.

The first to fourth control valves 191 to 194 are predetermined condition values stored in a conventional electronic system control circuit (not shown), such as whether the vessel is mooring or anchoring, whether the gas treatment facility is abnormally operated, or excessive evaporation gas is generated. The valve opening and closing is performed or the valve opening / closing size ratio is adjusted based on the presence or absence of the gas-gas emergency treatment.

To this end, the first to fourth control valves 191 to 194 are electrically and electronically coupled to an input / output interface of an electronic system control circuit (not shown).

The electronic system control circuit also receives the precise measurement values of the temperature, pressure, and flow rate of the input flow rate and the output flow rate to vaporize the liquid gas by following a predetermined design value in the liquid gas vaporizer 130 to control temperature and pressure. It is desirable to have an algorithm that performs flow control.

To this end, the analog thermometer 131 with a digital or A / D converter installed in the liquid gas vaporizer 130, the pressure gauge 132, the flow meter 133 is a signal input terminal (not shown) of the electronic system control circuit Is preferably connected to

Liquid gas vaporizer 130 is a conventional vaporization device that serves to vaporize using an external heat source in order to use the liquid gas as a fuel.

A gaseous gas supply line 183 is connected to the gas outlet of the liquid gas vaporizer 130.

The vaporization gas supply line 183 plays a role of supplying the vaporized gas vaporized in the liquid gas vaporizer 130 to the propulsion system 300 or the gas emergency treatment line 184.

To this end, a third control valve 193 is piped to the vaporization gas supply line 183 at the front position of the propulsion system 300, and the gas emergency treatment line 184 is positioned at the front position of the third control valve 193. Branched.

The gas emergency treatment line 184 is responsible for transferring the surplus evaporated gas to the emergency incinerator 150.

Here, the emergency incineration apparatus 150 is an incineration apparatus for forced combustion only in an emergency using surplus evaporated gas supplied through the gas emergency treatment line 184 as a fuel, and a conventional ignition nozzle connected to the gas emergency treatment line 184. It is desirable to further have an electronically controlled ignition device (not shown) disposed around such a ignition nozzle.

In addition, the gas emergency treatment line 184 is provided with a fourth control valve 194, and an emergency incineration device 150 is connected to the rear of the fourth control valve 194.

The third and fourth control valves 193 and 194 also serve to control the valve opening and closing by the conventional logic circuit mentioned above.

For example, the opening or closing size of the third control valve 193 and the fourth control valve 194 is adjusted according to the presence or absence of the vaporization gas emergency treatment request.

If there is a request for vaporization gas emergency treatment, the opening ratio of the fourth control valve 193 may be adjusted to adjust the liquefaction amount of the boiled gas based on a predetermined flow rate value or vaporization gas conversion ratio for the vaporization gas emergency treatment. Adjust

Accordingly, while the emergency treatment flow rate corresponding to the vaporization gas emergency treatment passes through the fourth control valve 194 of the vaporization gas exiting the liquid gas vaporizer 130, the remaining gasification gas except for the emergency treatment flow rate is adjusted to the third. The valve 193 is supplied to the propulsion system 300.

On the other hand, when there is no request for vaporization gas emergency treatment, the third control valve 193 is opened while the fourth control valve 194 is closed, so that all of the vaporized gas passes through the third control valve 193 to provide a propulsion system ( 300).

The propulsion system 300 is the propulsion system of the ship. The propulsion system 300 selects one or more of the boiler and steam turbine system 301, the dual fuel engine electric propulsion system 302, and the gas turbine electric propulsion system 303 described below.

The boiler and steam turbine system 301 is a propulsion method of a ship that generates steam by using evaporation or vaporization gas of a fluid such as LNG as fuel of a boiler, and supplies such steam to a steam turbine to generate propulsion force.

The dual fuel engine electric propulsion system 302 operates an internal combustion engine using evaporation or vaporization gas of a fluid, such as LNG, as a fuel, and uses a mechanical energy generated from this to generate electricity to drive a motor and obtain propulsion. That's the way.

The gas turbine electric propulsion system 303 is a propulsion method of a ship in which a gas turbine is operated by using an evaporation or vaporization gas of a fluid, such as LNG, as a fuel to operate a gas turbine, and generate electric power using mechanical energy from the gas turbine. .

Hereinafter, the evaporative gas recycling method of the present invention will be described with reference to FIGS. 4 and 5.

Liquefaction step of boil-off gas (S10)

The natural boil-off gas sent from the gas storage tank 100 becomes the boil-off gas compressed at 5 to 10 atmospheres through the low pressure compressor 110, and then enters the boil-off gas liquefier 200 through the boil-off gas sending line 180. .

On the other hand, the liquid gas forcibly sent from the gas storage tank 100 through the liquid gas delivery line 185 enters the boil-off gas liquefier 200.

The evaporated gas having 5 to 10 atmospheres of pressure introduced into the boil-off gas liquefier 200 undergoes heat exchange when mixed with the liquid gas, and as a result, is re-liquefied into the liquid gas containing the boil-off gas.

The liquid gas is forced out through the liquid gas sending line 185 and is in a supercooled state.

The relationship between the liquefied amount and pressure of the boil-off gas and the liquid gas flow forced out through the liquid-gas sending line 185 and in the supercooled state is shown in the graph of the liquid-gas flow rate and the boil-off gas conversion ratio shown in FIG. 6.

For example, the liquefaction of the boil-off gas is adjusted based on the boil-off gas conversion ratio corresponding to the liquid gas flow rate. That is, when liquefied only about 70% of the evaporated gas, the liquid gas flow rate 20000 kg / h may be injected from the injection port 187 of the evaporative gas liquefier 200, liquefied all the evaporated gas (for example, 100%) What is necessary is just to inject | pour the liquid gas flow volume 24000-2500 kg / h in the injection port 187 of the evaporative gas liquefier 200.

Recovery of the liquid gas and determination of the fuel supply amount (S11)

The liquid gas from which the boil-off gas is liquefied in the boil-off gas liquefier 200 is the first and second control valves based on the above-mentioned predetermined conditions (e.g., mooring or anchoring of the vessel, and the need for gas-gas emergency treatment) The gas may be flowed to the gas storage tank 100 or the liquid gas vaporizer 130 selectively to correspond to the full opening / closing of the 191 and 192 or a predetermined opening / closing size ratio.

The condition value is managed as a data value of a predetermined recovery and fuel supply operation program (not shown) so as to correlate with the predetermined fuel supply amount and recovery amount ratio.

For example, a portion of the liquid gas enters the liquid gas vaporizer 130 through the liquid gas transfer line 182 to correspond to a predetermined opening / closing size ratio of the second control valve 192, and the remaining portion of the liquid gas except for the portion. Is recovered to the gas storage tank 100 through the liquid gas recovery line 181 to correspond to the opening and closing size ratio of the first control valve 191.

Control step of vaporization factor (S12)

In the liquid gas vaporizer 130, it is very important to vaporize the 'liquid gas including the reliquefaction of the evaporation gas' to suit the fuel supply, but to maintain a constant temperature, pressure and flow rate corresponding to the vaporization factor. Do. Accordingly, the liquid gas vaporizer 130 follows the measurement values measured by the thermometer 131, the pressure gauge 132, and the flow meter 133 to a predetermined design value, so that the temperature and the pressure are kept constant as a result. Adjust

The heat source for vaporization in the liquid gas vaporizer 130 is usually heated above the outside combustion air temperature by steam or electric heaters produced by the auxiliary boiler in the ship.

Supply step of fuel (S13)

The vaporized gas produced in the liquid gas vaporizer 130 with the conditions (eg, temperature, pressure, and flow rate corresponding to the designed value) for combustion is the boiler and steam turbine system 301 described above through the vaporized gas supply line 183, The fuel is supplied to the fuel of the propulsion system 300 including at least one selected from the fuel engine electric propulsion system 302 and the gas turbine electric propulsion system 303.

Emergency Steps (S14)

When a ship enters the terminal, it usually maintains about 30% of the load in normal operation or 20% of the normal load in mooring, so there is an emergency to deal with the natural boil-off gas.

In the case of the present invention can be divided into two ways to deal with emergencies.

First, there is a method of liquefying and recovering natural boil-off gas through the liquefaction step of the boil-off gas (S10), the recovery of the liquid gas and the determination of the fuel supply amount (S11).

To this end, the first control valve 191 is open, the second control valve 192 is preferably closed. In this case, however, it is preferable to use it in the case of normal 20 hours or so when the mooring or berthing time of the ship is not lengthened due to special reasons.

Second, only a part of the natural boil-off gas is liquefied and recovered, and the remaining amount is transferred to the emergency incinerator 150 through the gas emergency treatment line 184.

To this end, the first control valve 191 is fully open, the second control valve 192 is able to pass a limited amount of liquid gas or a non-reliquefied evaporated gas to 10 to 30% of the total amount of generated boil-off gas. Some are open enough.

Through this, in the case of the present invention, since the amount of boil-off gas transferred to the emergency incinerator 150 can be limited to 10-30% of the total amount of boil-off gas, 70-90% of the natural boil-off gas is not consumed in vain. With this, it is possible to significantly reduce the processing capacity of the emergency incinerator 150 through this, or to have a feature that can be equipped with a small size emergency incinerator 150.

Second embodiment

The method and apparatus for recycling the boil-off gas of the present invention described in this embodiment is the same as that of the first embodiment except that the boil-off gas liquefier functions as a simple passage without the function of the liquefier as the ship operates normally. same. Thus, the same or similar reference numerals will be given to the same or corresponding components in FIGS. 4 to 7, and the description thereof will be omitted here.

7 is a block diagram of a method for recycling boil-off gas according to a second embodiment of the present invention.

4 and 7 related to the present invention recycling apparatus described above, when the evaporative gas liquefier 200 serves as a simple passage of the liquid gas for fuel supply, the liquid gas delivery line 185 is a liquid phase In the gas vaporizer 130, only the liquid gas for supplying the fuel to be forcibly vaporized is used as a flowing line.

At this time, the liquid gas for fuel supply is simply passed through the liquid gas delivery line 185 and the boil-off gas liquefier 200 as a passage to be vaporized in the boil-off gas liquefier 200 to be used as the fuel required for the propulsion system 300. .

That is, another method of recycling the boil-off gas as shown in FIG. 7 consists of the following steps.

Inflow stage of boil-off gas (S20)

In this step, as disclosed in the first embodiment, the natural evaporated gas of the gas storage tank 100 becomes the evaporated gas compressed to 5 to 10 atm, and then enters the evaporated gas liquefier 200.

Liquid gas transfer step (S21) for fuel supply

However, unlike the first embodiment, the liquid gas for fuel supply forcedly sent or supplied from the gas storage tank 100 through the liquid gas delivery line 185 is for fuel supply only, not for liquefaction of boiled gas. It is to be supplied only the necessary amount from the propulsion system (300).

To this end, the size of the transport flow rate of the extrusion pump 102 is also determined in accordance with the requirements of the propulsion system 300 in consideration of the flow rate of the boil-off gas. Of course, the extrusion pump 102 is also controlled to operate in response to the requirements of the propulsion system (300).

Here, the required value of the propulsion system 300 is based on the fuel consumption required according to the operating conditions of the vessel or gas treatment facility.

That is, the liquid supply gas for fuel supplied from the extrusion pump 102 to the boil-off gas liquefier 200 does not have a transport flow rate as its own cooling medium for liquefying or re-liquefying natural boil-off gas, and instead, the propulsion system 300 Only the amount minus the amount of boil-off gas is used to supply the inside of the boil-off gas liquefier 200.

That is, when the amount of boil-off gas increases, the extrusion pump 102 is operated so that the flow rate of the liquid gas for fuel supply is small.

Evaporative gas liquefaction pass step of the boil-off gas and liquid gas for fuel supply (S22)

The boil-off gas and the liquid gas for fuel supply pass while using the boil-off gas liquefier 200 simply as a passage, and then flow into the liquid-gas vaporizer 130.

That is, the function of the liquefier in the boil-off gas liquefier 200 is not important. For example, as can be seen in the graph of the conversion rate of the evaporation gas corresponding to the flow rate of the liquid gas in FIG. 6, when the evaporation gas liquefier 200 passes the fuel supplying liquid gas at 15000 kg / h or less, the liquefaction is almost performed in the evaporation gas. It won't happen.

Then, the step of adjusting the vaporization factor (S12), the fuel supply step (S13) and the emergency response step (S14) described in the first embodiment.

Third embodiment

Evaporation gas recycling method and apparatus of the present invention described in the present embodiment is the same as the first and second embodiments, except that the evaporation gas bypass line is provided. Thus, the same or similar reference numerals will be given to the same or corresponding components in FIGS. 4 to 9, and the description thereof will be omitted here.

8 is a block diagram of the boil-off gas recycling apparatus according to the third embodiment of the present invention, Figure 9 is a block diagram of the boil-off gas recycling method realized by the boil-off gas recycling apparatus shown in FIG.

Referring to Fig. 8, the evaporative gas recycling apparatus, the liquid gas delivery line 185 is forcibly vaporized in the liquid gas vaporizer 130 when using the evaporative gas bypass line 189 as the features of the third embodiment It is a line through which a quantity of liquid gas for fuel supply flows.

One end of the boil-off gas bypass line 189 is coupled to the boil-off gas sending line 180 corresponding to the low pressure compressor 110 and the boil-off gas liquefier 200, and the boil-off gas bypass line 189. The other end of the) is connected to the liquid gas transfer line 182 on the basis of the point connected to the liquid gas vaporizer (130).

It is preferable that a conventional fluid mixer (eg, a fixed linear mixer) is further provided at a point connected to the liquid gas vaporizer 130.

The low-temperature, low-pressure evaporated gas passing through the low pressure compressor 110 flows into the liquid gas transfer line 182 through the evaporation gas bypass line 189, and then the liquid gas escaped from the boil-off gas liquefier 200 side. It mixes into a cold mixed gas.

The fifth control valve 195 is piped to the boil-off gas sending line 180 corresponding to one end of the boil-off gas bypass line 189 and the boil-off gas liquefier 200, and the sixth control valve 196 is connected thereto. Is piped to the boil-off gas bypass line 189 to perform the opening and closing operation.

For example, when bypass of the boil-off gas is required, the fifth regulating valve 195 is closed and the sixth regulating valve 196 is opened.

When the bypass of the boil-off gas is not required and the same operation as that of the second embodiment described above is required, the fifth regulating valve 195 is opened and the sixth regulating valve 196 is closed.

On the other hand, the liquid gas for fuel supply flowing in the liquid gas delivery line 185 can simply pass through the boil-off gas liquefier 200 as a passage, it is then used as the fuel required for the propulsion system 300.

The reason for using the boil-off gas bypass line 189 is that there is no problem of handling excess boil-off gas when the vessel is normally operated, so that the boil-off gas and the fuel gas for fuel supply do not mix with each other in the boil-off gas liquefier 200. Instead, the fuel supplying liquid gas and the boil-off gas to be mixed in the liquid gas transfer line 182 in front of the liquid gas vaporizer 130, and then pass through the liquid gas vaporizer 130 to properly process the fuel of the ship For sake.

That is, the boil-off gas bypass line 189 is used for supplying boil-off gas to the boil-off gas liquefier 200.

The boil-off gas supplied by bypassing the boil-off gas bypass line 189 is mixed with the liquefied gas of the boil-off gas liquefier 200 in front of the liquid-gas vaporizer 130, and then passes through the gas-liquid gas vaporizer 130 while mixing gas. Becomes

The opening or closing of the third control valve 193 and the fourth control valve 194 is controlled by a predetermined condition value such as whether or not the gas gas emergency treatment is required.

For example, when there is a request for vaporization gas emergency treatment, the opening ratio of the fourth control valve 193 is adjusted based on the flow rate value for vaporization gas emergency treatment. Accordingly, while the emergency treatment flow rate corresponding to the vaporization gas emergency treatment of the mixed gas passes through the fourth control valve 194, the remaining mixed gas flow rate except the emergency treatment flow rate passes through the third control valve 193. It is to be supplied to the propulsion system (300).

On the other hand, when there is no request for vaporization gas emergency treatment, the third control valve 193 is opened while the fourth control valve 194 is closed, so that all the flow rates of the mixed gas pass through the third control valve 193. It is to be supplied to the propulsion system (300).

With reference to FIG. 8 and FIG. 9 at the same time, another evaporative gas recycling method is demonstrated.

Bypass step of the boil-off gas (S30)

When the vessel is normally operated, there is no problem of processing the surplus evaporated gas, after compressing the natural evaporated gas to have a pressure of 5 to 10 atm by the low pressure compressor 110 to make the evaporated gas, bypassed the evaporative gas liquefier 200 That is, the bypassed boil-off gas is supplied to the vaporization gas supply line 183 through the boil-off gas sending line 180, the boil-off gas bypass line 189, and the liquid gas vaporizer 130. However, the supply pressure may be added or subtracted within 5 atm according to the specification of the emergency incinerator 150 or the propulsion system 300 which performs the same role as the thermal oxidizer.

In order to bypass the boil-off gas, the fifth regulating valve 195 is closed and the sixth regulating valve 196 is opened.

Inflow stage of fuel gas supply (S31)

The liquid gas for fuel supply forced out from the gas storage tank 100 through the liquid gas sending line 185 passes through the boil-off gas liquefier 200. In this case, the boil-off gas liquefier 200 does not function as a liquefier and serves as a simple passage.

Mixing step of the boil-off gas and liquid gas (S32)

In the liquid gas transfer line 182, the 'fuel gas liquid supply gas forcibly passed from the gas storage tank 100 through the liquid gas delivery line 185 and then passed through the evaporative gas liquefier 200 as a passage' and evaporates. The boil-off gas that is bypassed through the gas bypass line 189 and supplied to the liquid gas transfer line 182 is mixed.

Generation step of gaseous gas (S33)

The liquid gas vaporizer 130 vaporizes the mixed gas so as to be suitable for supplying fuel, and at this time, it is very important that the temperature, pressure, and flow rate of the predetermined size of the liquid gas remain constant corresponding to a predetermined value.

The mixed gas is made of vaporized gas in the liquid gas vaporizer 130 and then supplied to the vaporized gas supply line 183.

Then, the fuel supply step S13 and the emergency response step S14 described in the first embodiment are performed.

The method for recycling the boil-off gas according to the present invention configured as described above has an advantage of minimizing the waste of excess boil-off gas by adjusting the liquefaction or re-liquefaction and use of the boil-off gas to correspond to the operation of the vessel.

In addition, the boil-off gas recycling apparatus according to the present invention is forcibly burned during the mooring or anchoring of the boil off gas of the vessel to prevent environmental problems such as waste of energy and carbon dioxide, nitrogen gas emissions.

In addition, the method and apparatus for recycling the boil-off gas of the present invention can substantially increase the competitiveness of future products by improving the technology of the ship, and have the effect of eliminating the emergency incineration device, which is the forced-burning gas, or minimizing the capacity. have.

In addition, preferred embodiments of the present invention are disclosed for the purpose of illustration, those skilled in the art will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications and modifications belong to the scope of the claims You will have to look.

Claims (9)

In the boil-off gas recycling method for treating the boil-off gas generated in the gas storage tank, A liquefaction step of the boil-off gas for compressing the boil-off gas to liquefy by the liquid gas of the gas storage tank in the boil-off gas liquefier (S10); Recovering the liquid gas containing the boil-off gas by the liquefaction step to the gas storage tank or selectively supplied to the gas storage tank corresponding to the full opening or closing size ratio of the first and second control valve Determining the fuel supply amount (S11); A step (S12) of controlling the vaporization factor to vaporize the liquid gas of the amount determined by the determining step by constantly adjusting temperature, pressure, and flow rate to be suitable for fuel supply from the liquid gas vaporizer; A fuel supply step (S13) for supplying the vaporized gas vaporized by the adjusting step to the fuel of the propulsion system; Emergency countermeasure step (S14) of opening and closing the first to fourth control valves to recover the total amount of the evaporated gas or to incinerate a small amount, Evaporative gas recycling method comprising a. The method of claim 1, In the liquefaction step of the boil-off gas (S10), the boil-off gas recycling method characterized in that the boil-off gas compressed to 5 to 10 atm pressure is introduced into the boil-off gas liquefier. The method of claim 1, In the liquefaction step of the boil-off gas (S10), the liquefied amount of the boil-off gas is controlled on the basis of the conversion rate of the boil-off gas corresponding to the liquid gas flow rate. The method of claim 2, Evaporation gas recycling method characterized in that it further comprises the step of passing through the boil-off gas liquefier (S22) characterized in that the boil-off gas and the liquid gas using the boil-off gas liquefier as a passage. The method of claim 2, Evaporation gas recycling method further comprises a bypass step (S30) for the boil-off gas is supplied to the vaporization gas supply line through the boil-off gas bypass line and the liquid gas transfer line and the liquid gas vaporizer connected to the boil-off gas sending line . The method of claim 5, In the liquid gas transfer line, the bypass boil-off gas is mixed with the liquid gas of the boil-off gas liquefier by a fluid mixer. In the boil-off gas recycling apparatus for treating the boil-off gas generated in the gas storage tank, An evaporating gas liquefier coupled to receive a liquid gas through a liquid gas sending line of the gas storage tank and to receive an evaporation gas through an evaporating gas sending line of the gas storage tank; A liquid gas vaporizer coupled to the liquid gas conveying line to receive the liquid gas containing the evaporated gas through the liquid gas conveying line of the boil-off gas liquefier; It includes a liquid gas recovery line coupled between the liquid gas transfer line and the gas storage tank to recover the liquid gas of the boil-off gas liquefier, Evaporation gas recycling apparatus characterized in that performed on the basis of the conversion rate of the evaporation gas when supplying a gas or a mixed gas of the evaporation gas mixed with the evaporation gas through the vaporization gas supply line of the liquid gas vaporizer. The method of claim 7, wherein And an extrusion pump is installed in the liquid gas delivery line to supply liquid gas to the inside of the boil-off gas liquefier. The method of claim 7, wherein The boil-off gas bypass line is further piped between the boil-off gas delivery line and the liquid-phase gas transfer line, and selectively opens and closes the fifth control valve of the boil-off gas delivery line and the sixth control valve of the boil-off gas bypass line. In accordance with the boil-off gas recycling apparatus, characterized in that for supplying the liquid gas transfer line.

Images