KR102670766B1 - System and Method for Controlling Pressure of Liquefied Gas Carrier - Google Patents

Abstract

In treating the boil-off gas generated from the liquefied gas storage tank of the liquefied gas carrier of the present invention, the pressure control system and method of the liquefied gas carrier for effectively controlling the pressure change of the boil-off gas according to the change in the load of the boil-off gas demander. will be.
The pressure control system of a liquefied gas carrier according to the present invention includes one or more liquefied gas storage tanks that store liquefied gas; In the liquefied gas carrier comprising: a boil-off gas processing unit that includes an engine that uses the boil-off gas generated in the liquefied gas storage tank as fuel and processes the boil-off gas discharged from the liquefied gas storage tank, the liquefied gas carrier and A movable reformer having a detachable connection and generating hydrogen by reforming the boil-off gas; And a control means provided on the liquefied gas carrier, detecting a change in pressure of the boil-off gas supplied to the boil-off gas processing unit, and controlling the flow rate of the boil-off gas supplied to the mobile reforming unit.

Description

{System and Method for Controlling Pressure of Liquefied Gas Carrier}

In treating the boil-off gas generated from the liquefied gas storage tank of the liquefied gas carrier of the present invention, the pressure control system and method of the liquefied gas carrier for effectively controlling the pressure change of the boil-off gas according to the change in the load of the boil-off gas demander. will be.

The liquefied gas supplier unloads the liquefied gas into the liquefied gas storage tank provided on the liquefied gas carrier, and the liquefied gas carrier loaded with liquefied gas in the liquefied gas storage tank sails at sea and moves to the liquefied gas demand place. The liquefied gas carrier anchors at the terminal and unloads the liquefied gas stored in the liquefied gas storage tank to the liquefied gas consumer.

In this way, liquefied gas carriers must dock and wait at the terminal for as little as half a day to as long as a week while unloading the liquefied gas stored in the liquefied gas storage tank at the supply or demand site. While unloading liquefied gas, a large amount of boil-off gas is generated, and the boil-off gas generated at this time must be discharged from the liquefied gas storage tank and treated to safely maintain the pressure of the liquefied gas storage tank.

Conventionally, when a ship is in operation, boil-off gas is used as fuel for propulsion engines and power generation engines, while while a liquefied gas carrier is at anchor, the propulsion engine does not operate, so boil-off gas is used as fuel for power generation engines (DFGE; Dual Fuel). It could only be supplied as fuel for the generator engine.

In addition, boil-off gas in an amount exceeding the fuel requirement of the engine was recovered by re-liquefaction using a re-liquefaction device mounted on the ship. However, if the amount of boil-off gas is large and exceeds the capacity of the reliquefaction device, the entire amount cannot be reliquefied and processed. In this case, the evaporative gas was wasted as it had no choice but to be disposed of by combustion in the GCU (Gas Combustion Unit).

As an alternative to effectively use the amount of boil-off gas that cannot be processed by engines and reliquefaction devices, an environmentally friendly method of treating boil-off gas by reforming the boil-off gas to generate hydrogen can be considered. However, it is very inefficient to carry a reforming device on a ship in preparation for reforming and processing boil-off gas.

Therefore, the present invention aims to improve the above-mentioned problems, and in particular, the boil-off gas is efficiently processed by reforming the boil-off gas generated from a liquefied gas carrier to generate and store hydrogen, and the boil-off gas is supplied to consumers. The aim is to provide a pressure control system and method for a liquefied gas carrier that can safely control pressure fluctuations of boil-off gas.

According to one aspect of the present invention for achieving the above-described object, there is provided at least one liquefied gas storage tank for storing liquefied gas; In the liquefied gas carrier comprising: a boil-off gas processing unit that includes an engine that uses the boil-off gas generated in the liquefied gas storage tank as fuel and processes the boil-off gas discharged from the liquefied gas storage tank, the liquefied gas carrier and A movable reformer having a detachable connection and generating hydrogen by reforming the boil-off gas; And a control means provided on the liquefied gas carrier, detecting a change in pressure of the boil-off gas supplied to the boil-off gas treatment unit, and controlling the flow rate of the boil-off gas supplied to the mobile reformer. A pressure control system is provided.

Preferably, the boil-off gas processing unit includes a compressor that compresses and supplies boil-off gas to a pressure required by the engine; and a re-liquefaction unit that re-liquefies the boil-off gas and returns it to the liquefied gas storage tank, wherein the control means transfers the compressed boil-off gas compressed in the compressor to one or more of the engine, the re-liquefaction unit, and the mobile reformer. It may include a control unit that distributes and supplies.

Preferably, the mobile reforming unit includes a reformer that recovers waste heat of exhaust gas discharged from the engine and generates hydrogen by reforming the boil-off gas; And as a means for assisting the waste heat of the exhaust gas, it may include a combustor that burns the boil-off gas to generate combustion gas and supplies combustion heat of the combustion gas to a reformer.

Preferably, the control means includes: a combustion flow rate control valve capable of controlling the flow rate of boil-off gas supplied to the combustor; a pressure measuring unit that measures pressure changes in evaporative gas supplied to the engine; a temperature measuring unit that measures the temperature of exhaust gas discharged from the engine; a first signal unit that calculates a flow rate of boil-off gas that can be supplied to the combustor according to the measured value of the pressure measurement unit and generates an opening rate control signal of the combustion flow rate control valve; a fourth signal unit that calculates a flow rate of boil-off gas necessary to produce heat to replenish the reformer according to the measured value of the temperature measurement unit and generates an opening rate control signal of the combustion flow rate control valve; and a control unit that determines and controls the opening rate of the combustion flow rate control valve by comparing the opening rate control signals of the first signal section and the fourth signal section.

Preferably, the control means includes: a re-liquid flow rate control valve for controlling the flow rate of boil-off gas supplied to the re-liquefaction unit; a pressure measuring unit that measures pressure changes in evaporative gas supplied to the engine; and a second signal unit that calculates the flow rate of boil-off gas to be supplied to the re-liquefaction unit according to the measured value of the pressure measurement unit and generates an opening rate control signal of the re-liquefaction flow rate control valve.

Preferably, the control means includes: a reforming flow rate control valve that controls the flow rate of boil-off gas supplied to the reformer; a pressure measuring unit that measures pressure changes in evaporative gas supplied to the engine; and a third signal unit that calculates a flow rate of boil-off gas to be supplied to the reformer according to the measured value of the pressure measurement unit and calculates an opening rate control signal of the reforming flow rate control valve.

According to another aspect of the present invention for achieving the above-described object, it includes the step of treating boil-off gas discharged from a liquefied gas storage tank, and the step of treating the boil-off gas includes converting the boil-off gas into fuel for the engine. supplying to; And supplying the boil-off gas to a mobile reformer connected to a liquefied gas carrier on which the liquefied gas storage tank and the engine are provided, thereby generating hydrogen through a reforming reaction. In the step of supplying the fuel, the engine Measuring the pressure change of the boil-off gas supplied to; And controlling the flow rate of boil-off gas supplied to the mobile reformer according to the pressure change measured in the step of measuring the pressure change. A method of controlling the pressure of a liquefied gas carrier is provided, further comprising a.

Preferably, the step of treating the boil-off gas includes: compressing the boil-off gas to a pressure required by the engine; A re-liquefaction step of re-liquefying the compressed boil-off gas and returning it to the liquefied gas storage tank; And it may include distributing and supplying the compressed boil-off gas to one or more of the step of supplying the fuel, the step of reliquefaction, and the step of generating the hydrogen.

Preferably, the step of generating hydrogen includes: supplying waste heat of exhaust gas discharged from the engine; And as a means for assisting the waste heat of the exhaust gas, it may include a combustion step of burning the boil-off gas to generate combustion gas and supplying combustion heat of the combustion gas.

Preferably, the step of controlling the flow rate includes: a pressure measuring step of measuring a change in pressure of the boil-off gas supplied to the step of supplying the fuel; A temperature measurement step of measuring the temperature of exhaust gas discharged from the engine; A first signal step for calculating the flow rate of boil-off gas that can be supplied to the combustion step according to the measured value in the pressure measurement step; A fourth signal step for calculating the flow rate of boil-off gas necessary to produce the amount of heat to supplement the waste heat of the exhaust gas supplied to the hydrogen generating step, according to the measured value in the temperature measuring step; And it may include a step of comparing the flow rate of the boil-off gas calculated in the first signal step and the fourth signal step to determine and control the flow rate of the boil-off gas to be supplied to the combustion step.

Preferably, the step of controlling the flow rate includes: a pressure measuring step of measuring a change in pressure of the boil-off gas supplied to the step of supplying the fuel; A second signal step for calculating the flow rate of boil-off gas to be supplied to the reliquefaction step according to the measured value in the pressure measurement step; And a third signal step of calculating the flow rate of the boil-off gas to be supplied to the hydrogen generating step according to the measured value in the pressure measuring step.

The pressure control system and method of a liquefied gas carrier according to the present invention includes equipping a mobile reforming system unit at the terminal where the ship is anchored while unloading liquefied gas, or mounting a reforming device at the terminal. By anchoring a barge dedicated to reforming and connecting it to a liquefied gas carrier while it is docked at the terminal, an amount of boil-off gas exceeding the capacity that can be handled by the liquefied gas carrier can be reformed to generate hydrogen, a clean energy source. .

The conventional mobile reformer includes a device in which the combustor (burner) moves vertically according to the temperature of the reformer combustion chamber in response to changes in engine load, and only controls the amount of heat supplied to the reformer through movement of the burner. It was possible.

However, according to the present invention, even if the flow rate of the boil-off gas supplied to the reliquefaction unit and the reformer (i.e., load variation) changes due to changes in the load of the engine, the pressure of the entire system can be stably controlled. , the flow rate of boil-off gas supplied to each boil-off gas consumer, such as the engine, reliquefaction unit, reformer, and combustor, can be optimized.

In particular, by considering the engine exhaust gas temperature and the pressure upstream of the engine, the optimal flow rate of evaporative gas is supplied to the reformer and combustor, so that the system is stable even under abnormal conditions such as initial operation of the engine, engine trip, or load fluctuation. can drive.

In addition, if the amount of heat required by the reformer is insufficient from the heat of the exhaust gas alone, the insufficient amount of heat can be compensated for by burning regasification gas. In order to generate the insufficient amount of heat, the temperature of the exhaust gas of the engine and the pressure upstream of the engine can be adjusted. Considering this, ensure that the optimal flow rate of evaporative gas can be used to generate combustion heat.

Figure 1 is a diagram briefly illustrating the configuration of a pressure control system for a liquefied gas carrier according to an embodiment of the present invention.

In order to fully understand the operational advantages of the present invention and the objectives achieved by practicing the present invention, reference should be made to the accompanying drawings illustrating preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, the structure and operation of a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. Here, in adding reference numerals to components in each drawing, it should be noted that identical components are indicated with the same reference numerals as much as possible, even if they are shown in different drawings. Additionally, the following examples may be modified into various other forms, and the scope of the present invention is not limited to the following examples.

In the embodiments of the present invention described later, the liquefied gas is LNG (Liquefied Natural Gas), LEG (Liquefied Ethane Gas), LPG (Liquefied Petroleum Gas), Liquefied Ethylene Gas, and Liquefied Propylene Gas. It may be a hydrocarbon series or a compound containing hydrogen, for example, a liquefied gas such as ammonia (NH ₃ ). In the embodiments described later, the liquefied gas will be LNG as an example.

Additionally, in the embodiments of the present invention described later, the ship may be any type of ship provided with a storage tank for storing liquefied gas. Representative examples include ships with self-propulsion capabilities such as LNG carriers, liquid hydrogen carriers, and LNG RVs (Regasification Vessels), as well as LNG FPSOs (Floating Production Storage Offloading) and LNG FSRUs (Floating Storage Regasification Units). Marine structures that do not have capabilities but are floating at sea may also be included.

In addition, in an embodiment of the present invention described later, the ship is equipped with an engine that can use liquefied gas and boil-off gas generated from the liquefied gas as fuel, or is equipped with any type of engine that uses liquefied gas or boil-off gas as fuel for the ship's engine. It may be a liquefied gas fueled ship (LFS).

Hereinafter, in explaining the present invention, an LNG carrier that can use LNG as engine fuel will be described as an example.

In addition, in an embodiment of the present invention described later, the engine can selectively use fuel oil such as MGO (Marine Gas Oil) and natural gas or boil-off gas obtained by vaporizing LNG as fuel, and if necessary, It may be a dual-fuel engine that can be used as fuel by mixing fuel oil and natural gas or boil-off gas.

The dual fuel engine may include any one or more of a high-pressure gas injection engine, a medium-pressure gas injection engine, and a low-pressure gas injection engine.

The high-pressure gas injection engine will be described as an engine using gas fuel of about 100 bar to 400 bar, or about 150 bar or more, preferably about 300 bar, for example, a ME-GI engine. In addition, the medium pressure gas injection engine may be an engine using gas fuel of about 10 bar to 20 bar, preferably about 16 bar, for example, an X-DF engine, and the low pressure gas injection engine may be an engine using gas fuel of about 5 bar to 10 bar. , preferably an engine using gaseous fuel at about 6.5 bar, for example, a DF engine, a DFDG engine, or a DFGE engine.

In an embodiment of the present invention described later, the engine includes a main engine for propulsion and an engine for power generation, and the ME-GI engine is applied as the main engine for propulsion and the DFGE is applied as an engine for power generation. Do this.

Hereinafter, with reference to FIG. 1, a pressure control system and method for a liquefied gas carrier according to an embodiment of the present invention will be described.

The pressure control system of a liquefied gas carrier according to an embodiment of the present invention is provided with one or more LNG storage tanks 100 that store LNG as cargo, an engine 120 that uses LNG as fuel, and an engine 120 ) and an exhaust gas line (EL) that releases exhaust gas into the atmosphere, and a boil-off gas processing unit that recovers and processes boil-off gas (BOG; Boil-Off Gas) discharged from the LNG storage tank 100 as effective energy. .

The boil-off gas processing unit of this embodiment includes a compressor 110 that compresses the boil-off gas to the pressure required by the engine 120 and supplies it to the engine 120, and a compressor 110 that re-liquefies the boil-off gas and returns it to the LNG storage tank 100. It includes a re-liquefaction unit 200 and a mobile reforming unit 500 that reforms boil-off gas to generate hydrogen.

The LNG storage tank 100, engine 120, compressor 110, reliquefaction unit 200, and control means described later may be mounted on the liquefied gas carrier according to this embodiment, and the mobile reformer ( 500) may be provided at a terminal where a liquefied gas carrier is moored, or may be provided on a barge that can move near the sea or terminal where a liquefied gas carrier is moored.

That is, the mobile reforming unit 500 according to this embodiment has a plurality of connections that can be connected to the liquefied gas carrier according to this embodiment, and the liquefied gas carrier according to this embodiment has a number of connections that can be connected to the mobile reforming unit 500. It has a number of connections that can be used, and when the liquefied gas carrier is moored or anchored, the connection of the liquefied gas carrier and the connection of the mobile reformer 500 are connected to each other to process the boil-off gas generated from the liquefied gas carrier by using the mobile reformer ( 500) for support.

In this embodiment, the description will be based on the state in which the liquefied gas carrier and the mobile reformer 500 are connected. Therefore, the liquefied gas carrier is in an anchored or moored state in which the main propulsion engine is not operating and only the power generation engine is operating. Hereinafter, the engine 120 refers to the power generation engine.

According to this embodiment, the boil-off gas line (BL) connecting the LNG storage tank 100 and the compressor 110 so that the boil-off gas discharged from the LNG storage tank 100 is supplied to the compressor 110, and the compressor 110 ), a fuel supply line (FL) connecting the compressor 110 and the engine 120 so that the compressed boil-off gas is supplied to the engine 120, and the compressed boil-off gas compressed in the compressor 110 is supplied to the re-liquefaction unit 200. ), a re-liquefaction line (LL) connecting the compressor 110 and the re-liquefaction unit 200 to be supplied to the compressor 110 and the re-liquefaction unit 200 so that the compressed boil-off gas compressed in the compressor 110 is supplied to the mobile reforming unit 500. It includes a reforming line (RL) and a combustion line (CL) connecting the mobile reforming unit 500.

In this embodiment, the boil-off gas is discharged from the LNG storage tank 100 through the boil-off gas line (BL) and supplied to the compressor 110, and is compressed in the compressor 110, followed by the fuel supply line (FL) and the re-liquefaction line. It is branched and supplied to one or more of the (LL), reforming line (RL), and combustion line (CL), and the flow rate of the boil-off gas branched and supplied to each line is controlled by a control means described later.

The reliquefaction unit 200 of this embodiment exchanges heat with the compressed boil-off gas compressed in the compressor 110 with the pre-compression boil-off gas supplied from the LNG storage tank 100 to the compressor 110 through the boil-off gas line (BL). It further includes a heat exchanger 210 for cooling, and a separator 220 for separating gas and liquid from the compressed boil-off gas cooled in the heat exchanger 210.

In addition, the reliquefaction unit 200 may further include a reliquefaction flow control valve 230 that expands the compressed boil-off gas cooled in the heat exchanger 210 to supercool it. The liquid flow control valve 230 is a Joule-Thompson valve, and can expand compressed boil-off gas by the Joule-Thomson effect to lower the pressure and temperature at the same time.

The ash flow rate control valve 230 is a part of the control means to be described later, and the opening degree of the ash flow rate control valve 230 depends on the change in the flow rate of the boil-off gas flowing into the engine 120, that is, the flow rate flowing into the reliquefaction unit 200. The rate can be controlled so that the reliquefaction flow rate can be adjusted.

The liquid flow control valve 230 is disposed between the heat exchanger 210 and the separator 220. Accordingly, the separator 220 can separate the vapor-liquid gas supercooled by the liquid-liquid flow rate control valve 230.

The compressed boil-off gas cooled while exchanging heat in the heat exchanger 210 is supplied to the separator 220 through the re-liquefaction line (LL), and while the compressed boil-off gas is cooled by heat exchange in the heat exchanger 210, the cold heat is recovered and the temperature The boil-off gas before compression, which has risen, is supplied to the compressor 110 through the boil-off gas line (BL).

The re-liquefied evaporation gas in the liquid state separated from the gas-liquid in the separator 220 can be recovered to the LNG storage tank 100 through the re-liquefaction line LL, and the uncondensed evaporation gas in the gas-liquid state separated in the separator 220 The gas may join the boil-off gas flow before compression supplied to the heat exchanger 210 through the flash gas line LL1 connecting the separator 220 and the boil-off gas line BL upstream of the heat exchanger 210.

The mobile reformer 500 of this embodiment is connected to a hydrogen line (HL) having a detachable connection to the reforming line (RL) of a liquefied gas carrier at one end, and the other end of the hydrogen line (HL), and is connected to the hydrogen line (HL) ) a reformer 510 that produces hydrogen through a reforming reaction by reforming the boil-off gas transferred through the evaporation gas, and an adsorber 520 that selectively separates only hydrogen gas from the product of the reforming reaction discharged from the reformer 510. It includes a hydrogen storage container 530 that stores the hydrogen separated in the adsorber 520, and a combustor 540 that supplies heat energy necessary for the reforming reaction to the reformer 510.

The adsorber 520 of this embodiment may be a device that separates hydrogen gas from the reforming reactant using a PSA (Pressure Swing Adsorption) method or a TSA (Temperature Swing Adsorption) method.

The combustor 540 of this embodiment generates combustion heat through a combustion reaction of air supplied through the air line AL and boil-off gas supplied from a liquefied gas carrier.

In addition, the mobile reformer 500 according to this embodiment is provided with a detachable connection with an exhaust gas branch line (EL1) branching from the exhaust gas line (EL) of the liquefied gas carrier at one end, and a reformer ( The first heat source line (ML1) is connected to the exhaust gas branch line (EL1) and supplies the waste heat of the exhaust gas transferred through the exhaust gas branch line (EL1) to the reformer (510), and the combustion line (CL) of the liquefied gas carrier at one end is detachable. This possible connection is provided, and the other end is connected to the combustor 540 to supply boil-off gas transferred through the combustion line (CL) as fuel to the combustor 540, and extends to the reformer 510 to be used in the combustor 540. It further includes a second heat source line ML2 that supplies combustion heat of the generated combustion gas to the reformer 510.

That is, the reformer 510 of this embodiment can receive heat energy from the combustion heat generated in the combustor 540 and the waste heat of the exhaust gas of the engine 120 and use it for a reforming reaction.

Exhaust gas or combustion gas whose temperature has been lowered as it is used as heat energy required for the reforming reaction in the reformer 510 may be released into the atmosphere.

The reformer 510 of this embodiment preferentially uses the waste heat of the exhaust gas supplied through the first heat source line ML1, but the waste heat of the exhaust gas is not sufficient for the reforming reaction, such as when the load of the engine 120 is low. If not, combustion gas can be supplied from the combustor 540, and the combustion gas can supplement the insufficient heat energy of the exhaust gas.

The combustor 540 of this embodiment is an auxiliary means of the engine 120 that supplies heat energy to the reformer 510, and can operate only when the heat energy of the reforming reaction is insufficient only from the exhaust gas waste heat of the engine 120.

That is, according to this embodiment, in normal times, boil-off gas is not supplied to the combustor 540, but is distributed and supplied to the engine 120, the reliquefaction unit 200, and the reformer 510, and the boil-off gas demand in the combustor 540 If this occurs, there is a possibility that the flow rate of the boil-off gas supplied to the engine 120 and the re-liquefaction unit 200 may change, that is, a pressure change may occur or the appropriate flow rate may not be supplied, resulting in a trip of the equipment.

Therefore, pressure control is required according to load changes in the engine 120, reliquefaction unit 200, reformer 510, and combustor 540, which are the demand sources for evaporation gas. In order to minimize pressure fluctuations, evaporation gas is evaporated in the combustor 540. When demand for gas occurs, the evaporation gas at the minimum flow rate required by the combustor 540 must be controlled to be supplied to the combustor 540.

According to this embodiment, it further includes control means for stably controlling pressure fluctuations in the system according to load fluctuations of the boil-off gas demand source.

The control means of this embodiment is provided in the re-liquefaction line (LL) and includes a re-liquefaction flow rate control valve 230 capable of controlling the flow rate of boil-off gas supplied to the re-liquefaction unit 200 by opening and closing control, and a reforming line (RL). A reforming flow rate control valve 330 is provided and can control the flow rate of boil-off gas supplied to the reformer 510 by opening and closing control, and a reforming flow rate control valve 330 is provided in the combustion line CL and can control the flow rate of boil-off gas supplied to the combustor 540. It includes a combustion flow control valve 340 that can control .

In addition, the control means of this embodiment is provided in the fuel supply line (FL) and includes a pressure measuring unit 310 that measures the pressure or pressure change of the evaporative gas supplied to the engine 120, and an exhaust gas line (EL). It is provided and further includes a temperature measuring unit 320 that measures the temperature of the exhaust gas discharged from the engine 120.

According to this embodiment, the change in the flow rate of the boil-off gas consumed by the engine 120 is measured according to the measurement value measured by the pressure measuring unit 310, and the change in the flow rate of the boil-off gas supplied to the engine 120 is measured. By controlling the opening degrees of the flow control valve 230, reforming flow control valve 330, and combustion flow control valve 340, the flow rate of boil-off gas supplied to the reliquefaction unit 200, reformer 510, and combustor 540 can be adjusted.

In addition, the control means of this embodiment calculates the flow rate of boil-off gas that can be supplied to the combustor 540 according to the measured value of the pressure measuring unit 310 and generates an opening rate control signal of the combustion flow rate control valve 340. 1 A system that calculates the flow rate of boil-off gas that can be supplied to the reliquefaction unit 200 according to the measured values of the signal unit 410 and the pressure measurement unit 310 and generates an opening rate control signal of the reliquefaction flow rate control valve 230. 2 A system for calculating the opening rate control signal of the reforming flow control valve 330 by calculating the flow rate of boil-off gas that can be supplied to the reformer 510 according to the pressure measurement values of the signal unit 420 and the pressure measuring unit 310. It includes 3 signal units 430.

In addition, the control means of this embodiment calculates the flow rate of the boil-off gas to be supplied to the combustor 540 according to the temperature measurement value of the temperature measuring unit 320 and generates an opening rate control signal of the combustion flow rate control valve 340. By receiving the control signals of the fourth signal unit 440, the first signal unit 410, and the fourth signal unit 440, the optimal amount of boil-off gas to be supplied to the combustor 540 is calculated and the combustion flow rate control valve ( It includes a control unit 400 that controls the opening rate of 340.

In this way, the control unit 400 of this embodiment calculates the boil-off gas flow rate that can be supplied to the combustor 540 based on the change in boil-off gas consumption of the engine 120 measured by the pressure measuring unit 310, and calculates the temperature Calculate the flow rate of boil-off gas to be supplied to the combustor 540 by estimating the amount of heat that cannot be satisfied by the waste heat of the exhaust gas in the reformer 510 based on the temperature measurement value of the exhaust gas measured by the measuring unit 320. Thus, the optimal evaporative gas flow rate to be supplied to the combustor 540 is calculated, and the opening rate of the combustion flow control valve 340 is controlled accordingly.

In this way, according to the present invention, while the liquefied gas carrier is moored or anchored, an amount of boil-off gas exceeding the amount of boil-off gas that can be processed by the engine 120 and the re-liquefaction unit 200 is generated using the mobile reformer 500. Hydrogen can be generated using

In addition, in the process of generating hydrogen using the mobile reformer 500, problems such as the possibility of equipment tripping caused by pressure fluctuations due to load fluctuations of boil-off gas demand sources such as the engine 120 or reformer 510 are avoided. Control measures are provided to solve the problem.

By optimizing the amount of boil-off gas supplied to the engine 120, re-liquefaction unit 200, reformer 510, and combustor 540 using control means, smooth operation of the engine 120 is possible and liquefied gas The carrier can smoothly interface with the mobile reformer 500.

In particular, the above-mentioned control means and control logic allow the system to be operated stably even during initial operation of the system or when a trip of the engine 120 occurs.

In addition, evaporative gas at an optimal flow rate can be supplied to the combustor 540 by using the control unit 400 based on the pressure measurement value upstream of the engine 120 and the exhaust gas temperature measurement value of the engine 120.

In addition, the pressure or pressure change upstream of the engine 120 is measured and the opening rate of the reforming flow control valve 330 is controlled according to the change in the boil-off gas flow rate supplied to the engine 120 based on the measured value, thereby controlling the reformer 510. ) and prevent tripping of the engine 120 by controlling the flow rate and pressure of the boil-off gas supplied to the reformer 510 and controlling the opening rate of the liquid flow control valve 230 according to the change in the flow rate of the boil-off gas supplied to the reformer 510. You can.

The present invention is not limited to the above-mentioned embodiments, and it is obvious to those skilled in the art that the present invention can be implemented with various modifications or variations without departing from the technical gist of the present invention. It was done.

100: LNG storage tank BL: Boil-off gas line
110: Compressor FL: Fuel supply line
120: Engine LL: Reliquefaction line
200: Reliquefaction unit LL1: Flash gas line
210: Heat exchanger RL: Reforming line
220: Separator CL: Combustion line
230: Ash liquid flow control valve EL: Exhaust gas line
310: Pressure measuring unit EL1: Exhaust gas branch line
320: Temperature measuring unit HL: Hydrogen line
330: Reforming flow control valve ML1: First heat source line
340: Combustion flow control valve ML2: Second heat source line
400: Control unit AL: Air line
410: 1st signal unit
420: 2nd signal unit
430: Third signal unit
440: 4th signal unit
500: Mobile reformer
510: reformer
520: adsorber
530: Hydrogen storage container
540: Combustor (burner)

Claims (11)

One or more liquefied gas storage tanks provided to store liquefied gas;
In a liquefied gas carrier including an engine that uses the boil-off gas generated in the liquefied gas storage tank as fuel, and a boil-off gas processing unit that processes the boil-off gas discharged from the liquefied gas storage tank,
A movable reformer having a detachable connection to the liquefied gas carrier and generating hydrogen by reforming the boil-off gas; and
A control means provided on the liquefied gas carrier, detecting a change in the pressure of the boil-off gas supplied to the boil-off gas treatment unit, and controlling the flow rate of the boil-off gas supplied to the mobile reformer;
The control means is,
A combustion flow rate control valve capable of controlling the flow rate of boil-off gas supplied to the mobile reformer;
a pressure measuring unit that measures pressure changes in evaporative gas supplied to the engine;
a first signal unit that calculates a flow rate of boil-off gas that can be supplied to the mobile reformer according to the measured value of the pressure measurement unit and generates an opening rate control signal of the combustion flow rate control valve;
a temperature measuring unit that measures the temperature of exhaust gas discharged from the engine;
a fourth signal unit that calculates a flow rate of boil-off gas necessary to produce heat to be replenished in the mobile reformer according to the measured value of the temperature measurement unit and generates an opening rate control signal of the combustion flow rate control valve; and
A control unit that determines and controls the opening rate of the combustion flow control valve by comparing the opening rate control signals of the first signal section and the fourth signal section. In claim 1,
The evaporation gas processing unit,
A compressor that compresses and supplies evaporative gas to the pressure required by the engine; and
It includes a re-liquefaction unit that re-liquefies the boil-off gas and returns it to the liquefied gas storage tank,
The control means is,
A pressure control system for a liquefied gas carrier comprising: a control unit that distributes and supplies the compressed boil-off gas compressed in the compressor to one or more of the engine, the re-liquefaction unit, and the mobile reformer. In claim 1,
The mobile reforming unit,
A reformer that recovers waste heat from exhaust gas discharged from the engine and generates hydrogen by reforming the boil-off gas; and
As a means for assisting the exhaust gas waste heat, a combustor that burns the boil-off gas to generate combustion gas and supplies combustion heat of the combustion gas to a reformer. A pressure control system for a liquefied gas carrier. delete In claim 2,
The control means is,
A re-liquid flow rate control valve that controls the flow rate of boil-off gas supplied to the re-liquefaction unit;
a pressure measuring unit that measures pressure changes in evaporative gas supplied to the engine; and
A pressure control system for a liquefied gas carrier, including a second signal unit that calculates the flow rate of boil-off gas to be supplied to the re-liquefaction unit according to the measured value of the pressure measurement unit and generates an opening rate control signal of the re-liquefaction flow rate control valve. . In claim 3,
The control means is,
A reforming flow rate control valve that controls the flow rate of boil-off gas supplied to the reformer;
a pressure measuring unit that measures pressure changes in evaporative gas supplied to the engine; and
A pressure control system for a liquefied gas carrier comprising; a third signal unit that calculates the flow rate of boil-off gas to be supplied to the reformer according to the measured value of the pressure measurement unit and calculates an opening rate control signal of the reforming flow rate control valve. It includes the step of treating boil-off gas discharged from the liquefied gas storage tank,
The step of processing the boil-off gas is,
Supplying the evaporative gas as fuel for the engine;
supplying the boil-off gas to a mobile reformer connected to a liquefied gas carrier equipped with the liquefied gas storage tank and an engine, thereby producing hydrogen through a reforming reaction;
Measuring the pressure change of evaporative gas supplied to the engine in the step of supplying the fuel; and
Comprising: controlling the flow rate of boil-off gas supplied to the mobile reformer according to the pressure change measured in the step of measuring the pressure change,
The step of controlling the flow rate is,
A pressure measuring step of measuring the pressure change of the boil-off gas supplied to the step of supplying the fuel;
A temperature measurement step of measuring the temperature of exhaust gas discharged from the engine;
A first signal step for calculating the flow rate of boil-off gas that can be supplied to the hydrogen generating step according to the measured value in the pressure measuring step;
A fourth signal step for calculating the flow rate of boil-off gas necessary to produce the amount of heat to supplement the waste heat of the exhaust gas supplied to the hydrogen generating step, according to the measured value in the temperature measuring step; and
A pressure control method of a liquefied gas carrier further comprising; comparing the flow rate of the boil-off gas calculated in the first signal step and the fourth signal step to determine and control the flow rate of the boil-off gas to be supplied to the hydrogen generating step. . In claim 7,
The step of processing the boil-off gas is,
Compressing the evaporative gas to the pressure required by the engine;
A re-liquefaction step of re-liquefying the compressed boil-off gas and returning it to the liquefied gas storage tank; and
A method of controlling the pressure of a liquefied gas carrier comprising: distributing and supplying the compressed boil-off gas to one or more of the step of supplying the fuel, the step of re-liquefaction, and the step of generating the hydrogen. In claim 7,
The step of generating hydrogen is,
supplying waste heat from exhaust gas discharged from the engine; and
As a means of assisting the waste heat of the exhaust gas, a combustion step of burning the boil-off gas to generate combustion gas and supplying combustion heat of the combustion gas; A pressure control method of a liquefied gas carrier comprising a. delete In claim 8,
The step of controlling the flow rate is,
A pressure measuring step of measuring the pressure change of the boil-off gas supplied to the step of supplying the fuel;
A second signal step for calculating the flow rate of boil-off gas to be supplied to the reliquefaction step according to the measured value in the pressure measurement step; and
A third signal step of calculating the flow rate of boil-off gas to be supplied to the hydrogen generating step according to the measured value in the pressure measuring step. A method of controlling the pressure of a liquefied gas carrier comprising a.

Images