KR101257937B1 - System for handling boil-off-gas and handling method thereof - Google Patents

Abstract

An evaporative gas treatment system and a treatment method thereof are disclosed. The present invention includes a storage unit for storing gas; and a compression unit for compressing the gas generated in the storage unit and having at least two temperature ranges; and a processing unit for supplying the gas passing through the compression unit. By using a plurality of compressors that can operate in different temperature ranges, it is possible to use a compressor in a wide temperature range, and improve the operating efficiency of the compressor.

Description

System for handling boil-off-gas and handling method

The present invention relates to a boil-off gas treatment system, and more particularly to a boil-off gas treatment system for operating the gas vaporized from the storage tank using a multi-stage compressor operating in different temperature ranges, and a treatment method thereof.

Typically, a liquid natural gas (Liquid Natural Gas, LNG) supply system refers to a system using natural gas mainly composed of methane as an energy source. In the case of a liquefied natural gas carrier, the liquefied natural gas is stored in a liquid state at -162 ° C in a storage tank and transported.

At this time, during transportation of the liquefied natural gas carrier, the liquefied natural gas in the storage tank is continuously vaporized due to the heat applied from the outside. This vaporized gas is called BOG (Bog-Off Gas). If the vaporized gas is left unattended, the pressure of the storage tank due to the expansion of the vaporized gas becomes high, and there is a risk that the storage tank is damaged. Thus, the vaporized gas is used as a power generation fuel for the propulsion of the liquefied natural gas carrier or is re-liquefied and returned to the storage tank.

In a conventional liquefied natural gas supply system, the vaporized gas from the storage tank is sprayed with a liquefied natural gas in a pre-cooler to give a desired temperature, for example, about -120 ° C. It is then cooled and then supplied. However, during cooling of the vaporized gas in the precooler, excessive vaporized gas is further generated while exchanging heat with the liquefied natural gas to be injected.

On the other hand, the liquefied natural gas carriers are transported in a laden state filled with liquefied natural gas inside the storage tank, or after liquefied natural gas is transported from the production site to the demand site, the liquefied natural gas is left in the storage tank with a minimum amount of fuel. It is operated.

In some cases, however, the liquefied gas inside the storage tank must be transported to the terminal as much as possible and operated in a condition where there is a minimum of heel remaining, that is, in a heel out condition. impossible to use. Therefore, since the compressor cannot be operated and the vaporized gas present in the storage tank continuously raises the pressure of the storage tank, the vaporized gas is burned in the gas combustion unit (GCU) or released into the atmosphere. In order to use such vaporized gas, it is necessary to improve the compressor operating range.

This invention makes it a main subject to provide the evaporative gas processing system which reduced the excess vaporization gas by not using a precooler, and its processing method.

Another object of the present invention is to provide an evaporative gas treatment system and a method of treating the same, which improve the operating efficiency of the compressor so that the compressor can be used even at a high temperature.

Evaporative gas treatment system according to an aspect of the present invention,

A storage unit for storing gas;

A compression unit compressing the gas generated in the storage unit and having at least two temperature ranges;

And a processing unit to supply gas passing through the compression unit.

In addition, the compression unit is composed of at least two compressors for compressing the gas vaporized from the storage unit,

The processing unit includes a dual fuel engine supplied with gaseous gas from the compression unit, and a gas combustion unit branched from a pipe supplied to the dual fuel engine,

It is further connected to the reservoir, and further comprises a vent mast for emitting the atmosphere of the vaporized gas.

In addition, the compression unit includes a first compressor and a second compressor operating in operating zones of different temperatures,

The first compressor is a compressor operating in a low temperature operating region,

The second compressor is a compressor operating in a high temperature operating region,

In front of the first compressor and the second compressor, a switching valve for selectively switching the supply path of the vaporized gas is installed according to the operating conditions.

In addition, each of the first compressor and the second compressor is a multi-stage compressor that is compressed in at least two stages.

Furthermore, the second compressor includes at least one inter cooler.

Moreover, an after cooler is further installed at the rear of the compression unit.

According to another aspect of the present invention, there is provided a treatment method of an evaporative gas treatment system.

Supplying vaporized gas from the liquefied natural gas storage tank to a compressor having a first compressor and a second compressor operating in operating zones of different temperatures;

Selectively supplying the vaporized gas to a first compressor or a second compressor; And

Supplied to the first compressor or the second compressor according to whether the first compressor is broken when supplied to the first compressor, and supplied to the dual fuel engine, and whether the second compressor is broken when supplied to the second compressor. And supplying it to the first compressor or the second compressor to supply the dual fuel engine or the gas combustion unit.

In addition, the first compressor is a compressor operated in a low temperature operating region,

The second compressor is a compressor operating in a high temperature operating region,

A switching valve provided in front of the first compressor and the second compressor selectively switches the supply path of the vaporized gas to the first compressor or the second compressor according to the operating conditions of the compressor.

In addition, the first compressor is operated under a suitable navigational operating condition,

The second compressor is operated under collinear navigational operating conditions.

As described above, the evaporative gas treatment system of the present invention and its treatment method can obtain the following effects.

First, the use of a compressor in a wide temperature range is possible by using a plurality of compressors that can operate in different temperature ranges.

Second, since a plurality of compressors in different temperature ranges are used, the operating efficiency of the compressor can be improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

1 is a block diagram showing an evaporative gas treatment system according to an embodiment of the present invention,
2 is a block diagram showing a multi-stage compressor according to an embodiment of the present invention,
3 is a flow chart illustrating a process of compression of the evaporative gas treatment system of FIG.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The terms first, second, etc. may be used to describe various elements, but the elements should not be limited by terms. The terms are used only to distinguish one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a component, Should not be construed to preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

Hereinafter, an embodiment of according to the present invention will be described in detail with reference to the accompanying drawings, in the description with reference to the accompanying drawings, the same or corresponding components are given the same reference numerals and duplicate description thereof It will be omitted.

1 illustrates a liquefied natural gas supply system 100 according to an embodiment of the present invention.

The evaporative gas treatment system of the present embodiment will be described with reference to the liquefied natural gas supply system 100 by way of example.

Referring to the drawings, the liquefied natural gas supply system compresses the gas generated in the liquefied natural gas storage tank 101, the liquefied natural gas storage tank 101, the storage unit for storing gas, and at least two temperature ranges The branch includes a multi-stage compressor (102), a forced evaporator (103), a processing unit in which the gas passing through the compression unit is processed, a pipe (106), and a vent mast (113). The gas treatment unit includes a dual fuel diesel engine DFDE 104 and a gas combustion unit GCU 105.

The said storage tank 101 is a tank which stores the liquefied natural gas 107 cooled at -162 degreeC, and is provided in multiple numbers. The storage tank 101 provided in the liquefied natural gas supply system 100 may be a membrane type storage tank in addition to a plurality of independent storage tank methods as in the present embodiment. Each bottom of the storage tank 101 is provided with a pump 108 for discharging the liquefied natural gas 107 to the outside.

The compressor 102 is a device in which the vaporized gas generated from the storage tank 101 is supplied through the pipe 106 and compressed. The compressor 102 is a multi-stage compressor capable of compressing at least two stages or more depending on the temperature and the gas amount of the vaporized gas. The compressor 102 includes a first compressor 109 and a second compressor 110 operated in operating zones of different temperatures. The gas vaporized from the storage tank 101 can be selectively supplied to the first compressor 109 or the second compressor 110 by switching the switching valve 111.

The dual fuel engine 104 may pass through the multi-stage compressor 102 to allow vaporized gas having a desired pressure and temperature to flow through the pipe 106. The dual fuel engine 104 provides an energy source to propel a liquefied natural gas carrier using gas vaporized from the storage tank 101. The dual fuel engine 104 is an engine capable of driving a steam turbine by burning vaporized gas to generate steam, or selectively using fossil fuel and vaporized gas as fuel.

The gas combustion unit 105 is a device that burns the remaining vaporized gas when the vaporized gas is excessively supplied while the vaporized gas is supplied to the dual fuel engine 104.

The vent mast 113 discharges vaporized gas directly into the atmosphere in addition to the multi-stage compressor 102, the dual fuel engine 104, or the gas combustion unit 105 used to adjust the pressure in the storage tank 101. It is a device that can.

Meanwhile, the forced evaporator 103 is a device for forcibly vaporizing liquefied natural gas to supply the dual fuel engine 104 when there is less vaporization gas in the storage tank 101.

Here, the multi-stage compressor 102 includes at least two compressors, for example, a first compressor 109 operating in a low temperature operating region and a second compressor 110 operating in a high temperature operating region.

This will be described in more detail as follows.

The gas vaporized from the storage tank 101 can be selectively supplied to the first compressor 109 or the second compressor 110 by switching the switching valve 111. In this case, the vaporized gas includes a gas in which methane (CH 4) gas: nitrogen (N 2) is mixed in a predetermined component ratio.

The inlet temperature flowing into the multi-stage compressor 102 is about −140 ° C. to 40 ° C., and may be selectively supplied to the first compressor 109 or the second compressor 110 according to the incoming temperature. The inlet pressure of the multistage compressor 102 is about 103 kPa, but may be higher depending on whether the forced evaporator 103 is in operation. The discharge flow rate and the discharge pressure must satisfy the pressure condition and the required flow rate that can be injected into the dual fuel engine 104 and combust it.

On the other hand, the discharge temperature is changed according to the inlet conditions, in some cases it may be further installed after cooler (After Cooler, 112). The after cooler 112 is required to cool the vaporized gas that has passed through the first compressor 109 or the second compressor 110 in multiple stages to a desired temperature for entering the dual fuel engine 104. .

In this case, the first compressor 109 is operated in a Laden Voyage condition. The first compressor 109 is operable when the inlet temperature range is -140 ° C to -20 ° C, and the optimum temperature range is a multi-stage compressor operating in a low temperature operating range of -90 ° C.

The second compressor 110 is operated in a ballast voyage condition. The second compressor 110 may be driven when the inlet temperature range is -120 ° C to 40 ° C, and the optimum temperature range is a multistage compressor operating in a high temperature operating range of -60 ° C.

The first compressor 109 and the second compressor 110 may be selectively used by switching the switching valve 111 when there is an abnormality during driving.

The first compressor 109 and the second compressor 110 may be configured in at least two stages for each compressor according to the temperature and gas amount of the vaporized gas to be compressed. For example, referring to FIG. 2, the compressor 200 according to an embodiment of the present invention is a three stage compressor including three compression units 201 to 203.

The three compression units 201 to 203 may include a first compression unit 201 and a first compression unit configured to compress the gas vaporized from a storage tank (see 101 in FIG. 1) into a first stage, and the first compression unit. A second compression unit 202 installed downstream of 201 and compressed in two stages; and a third compression unit 203 installed downstream of the second compression unit 202 and compressed in three stages. Include. Of course, the first to third compression units 201 to 203 include an impeller and a diffuser.

Downstream of the second compression section 202, a control valve 204 is provided. The control valve 204 is a valve for controlling the flow of vaporized gas by determining whether or not intercooling (Intercooling) according to the temperature discharged from the second compression unit 202.

An inter cooler 205, which is a temperature control device, is installed between the second compression unit 202 and the third compression unit 203, and fresh water may be used as the cooling water. The inter cooler 205 may be selectively installed.

For example, the intercooler is not installed in the first compressor 109 operating in the low temperature region of FIG. 1, but is installed in the second compressor 110 operated at a relatively higher temperature than the first compressor 109. Can be installed. In particular, the second compressor 110 requires an inter cooler in case the vaporized gas is 0 ° C. or more.

Alternatively, an inter cooler may be installed in each of the first and second compressors 110 or one inter cooler may be connected and installed to be common to the first and second compressors 109 and 110. have.

Returning to FIG. 2 again, the introduced vaporized gas is compressed through the first compression unit 201 in one stage, and the compressed vaporized gas is introduced into the second compression unit 202 in two stages. The vaporized gas passing through the second compression unit 202 is cooled through the inter cooler 205 according to the discharge temperature and flows into the third compression unit 203 in three stages, or directly without passing through the inter cooler 205. It may flow into the third compression unit 203.

On the other hand, the first compressor 109 and the second compressor 110 can be operated at the same time, the vaporized gas compressed from the first compressor 109 and the second compressor 110 is individually a dual fuel engine ( 104 and the gas combustion unit 105 are connected to each other.

In this case, the first compressor 109 supplies the gas to the dual fuel engine 104, the second compressor 110 is configured to supply the gas to the gas combustion unit 105, or the first compressor 109 Supplies gas to the gas combustion unit 105, and the second compressor 110 is configured to supply gas to the dual fuel engine 110.

In addition, the multi-stage compressor 102 may be set to only the first compressor 109. In this case, it is for use as a low temperature high efficiency compressor system which ignores normal temperature operation. In addition, the multi-stage compressor 102 may be set to only the second compressor 110. In this case, it is to use as a stand-by system for widening the operation range, ignoring high efficiency operation.

Referring to FIGS. 1 to 3, a multi-stage compression process of vaporized gas using the liquefied natural gas supply system 100 according to an exemplary embodiment having the above configuration will be described below.

First, when vaporized gas is generated from the storage tank 101 (S10), the generated vaporized gas is introduced into the multi-stage compressor 102 through the pipe 106. (S20) In front of the multi-stage compressor 102 Since the switching valve 111 is provided, it can supply to the 1st compressor 109 and the 2nd compressor 110 selectively.

At this time, the first compressor 109 is operated in a suitable sailing conditions, the inlet temperature range is -140 ℃ to -20 ℃, the optimum temperature range is a compressor driven in the low temperature operating range of -90 ℃, The second compressor 110 is operated under collinear navigational conditions and is driven in a high temperature operating region where the inlet temperature range is -120 ° C to 40 ° C.

It is determined whether the operation condition of the compressor 102 is a ship navigation operation condition or a collaborative navigation operation condition.

When the compressor 102 is driven under the ship navigation condition, the switching valve 111 is switched so that the first compressor 109 is driven. When the compressor 102 is driven under the air navigation condition, the compressor 102 is operated. 2, the switching valve 111 is switched so that the compressor 110 is driven. In the present embodiment, the first compressor 109 is set to be driven basically.

When the compressor 102 is driven under the appropriate sailing condition, it is determined whether the first compressor 109 is broken or not. (S40) At this time, the operating conditions of the first compressor 109 The temperature of the incoming gaseous gas cannot exceed -20 ° C. This is because the temperature range in which the first compressor 109 is operated is -140 ° C to -20 ° C.

If the first compressor 109 is not a failure, the first compressor 109 is driven to compress the vaporized gas into multiple stages (S50), and the vaporized gas cooled to a desired temperature is supplied to the dual fuel engine 104. ) Will flow into (S70).

On the other hand, if the first compressor 109 fails, the switching valve 111 is switched to stop the operation of the first compressor 109, and the second compressor 110 is driven to discharge the vaporized gas. Compressed in multiple stages (S60), and the vaporized gas cooled to the desired temperature is introduced into the dual fuel engine 104 (S70).

On the other hand, when the compressor 102 is driven under collinear navigation conditions, the switching valve 111 is switched to drive the second compressor 110. At this time, it is determined whether the second compressor 110 is a failure or not.

If the second compressor 110 is not in a malfunction, the second compressor 110 is driven to compress the vaporized gas into multiple stages (S90), and the vaporized gas cooled to a desired temperature is supplied to the dual fuel engine 130. ) Will flow into (S130).

On the other hand, when the second compressor 110 is broken, it is determined whether the vaporized gas is above or below -20 ° C.

When the vaporized gas is below -20 ° C, the first compressor 109 is driven to compress the vaporized gas into multiple stages (S110), and the vaporized gas cooled to a desired temperature is transferred to the dual fuel engine 104. It will be introduced. (S130)

On the contrary, when the vaporized gas is above -20 ° C, the vaporized gas is burned through the gas combustion unit 105 or discharged to the atmosphere.

As such, the compressor 102 drives the second compressor 110 when the first compressor 109 fails in the appropriate navigation condition. In addition, when the second compressor 110 fails under collinear navigational conditions in which the liquefied natural gas is present in the storage tank 101, the first compressor 10 is driven.

100 ... liquefied natural gas supply system
101 liquefied natural gas storage tank 102 multi-stage compressor
103 ... Force evaporator 104 ... Dual fuel engine
105 ... plastic combustion unit 106 ... piping
107 .. Liquefied natural gas 109 ... first compressor
110..2nd compressor 111 ... switching valve
112 ... after cooler 113 ... vent mast

Claims (18)

A storage unit for storing gas;
A compressor including a first compressor configured to compress the gas generated in the storage unit, a first compressor operated within a first temperature range, and a second compressor operated within a second temperature range set higher than the first temperature range;
A processing unit to supply gas passing through the compression unit; And
In front of the first compressor and the second compressor, the vaporized gas is supplied to the first compressor under the ship navigation operating conditions and the supply of the vaporized gas to the second compressor is cut off, and the air is supplied to the second compressor under the collinear navigation operating conditions. A switching valve for supplying vaporized gas and for shutting off the supply of vaporized gas to the first compressor,
The switch valve,
An evaporative gas treatment system for supplying the vaporized gas to the second compressor when the first compressor fails in a ship operating condition, and for supplying the vaporized gas to the first compressor when the second compressor fails in a collinear operation condition . The method of claim 1,
The processing unit includes a dual fuel engine supplied with gaseous gas from the compression unit, and a gas combustion unit branched from a pipe supplied to the dual fuel engine,
And a vent mast connected to the reservoir and configured to discharge the vaporized gas into the atmosphere. delete The method of claim 1,
The first compressor is a low temperature compressor operating in a temperature range of -140 ℃ to -20 ℃,
The second compressor is an evaporative gas treatment system, characterized in that the high temperature compressor operating in a temperature range of -120 ℃ to 40 ℃. The method of claim 1,
Wherein said first and second compressors are multistage compressors, each being compressed in at least two stages or more. The method of claim 1,
And the second compressor comprises at least one inter cooler. The method according to claim 6,
The intercooler is connected in common with the first compressor. The method of claim 1,
Evaporative gas treatment system, characterized in that the after cooler is further installed behind the compression unit. The method of claim 1,
The first compressor and the second compressor are operated simultaneously, and the compressed gas in each compressor is individually connected to supply the dual fuel engine and the plastic combustion unit. The method of claim 9,
The first compressor supplies gas to the dual fuel engine,
Said second compressor being connected to supply gas to a gas combustion unit. The method of claim 9,
The first compressor supplies gas to a gas combustion unit,
And the second compressor is connected to supply gas to the dual fuel engine. Supplying vaporized gas from the liquefied natural gas storage tank to a compressor having a first compressor and a second compressor operating in operating zones of different temperatures;
Selectively supplying the vaporized gas to a first compressor or a second compressor; And
Supplied to the first compressor or the second compressor according to whether or not the first compressor is broken when supplied to the first compressor, and supplied to the dual fuel engine, and whether or not the second compressor is broken when supplied to the second compressor. And supplying the fuel to the first compressor or the second compressor and supplying the fuel to the dual fuel engine or the gas combustion unit.
The inlet temperature range of the second compressor is higher than the inlet temperature range of the first compressor,
Selectively supplying the vaporized gas to a first compressor or a second compressor,
Supply the vaporized gas to the first compressor and stop supply of the vaporized gas to the second compressor in a suitable ship operating condition, and in the collinear operation condition, supply the vaporized gas to the second compressor and supply the first compressor A method of treating an evaporative gas treatment system, the step of interrupting the supply of vaporized gas to a furnace. delete delete 13. The method of claim 12,
The first compressor is operated in the inlet temperature range of -140 ℃ to -20 ℃ temperature range,
The second compressor is a method of treating an evaporative gas treatment system, characterized in that the inlet temperature range is operated within a temperature range of -120 ℃ to 40 ℃. 13. The method of claim 12,
When supplied to the first compressor,
In case of failure of the first compressor, the first compressor is supplied to the second compressor, thereby supplying the cooled gaseous gas to the dual fuel engine.
When the first compressor is not a failure, it is supplied to the first compressor, through which the cooled vaporization gas is supplied to the dual fuel engine, the processing method of the evaporative gas treatment system. 13. The method of claim 12,
When supplied to the second compressor,
When the second compressor is broken, the vaporized gas is supplied to the dual fuel engine or the gas combustion unit by comparing the vaporized gas temperature with the set temperature.
If the second compressor is not a failure, it is supplied to the second compressor, through which the cooled vaporization gas is supplied to the dual fuel engine processing method characterized in that the. The method of claim 17,
When the vaporization gas temperature is higher than the set temperature, it is sent to a gas combustion unit to burn the vaporization gas or discharge it to the atmosphere,
And when the temperature of the vaporized gas is less than or equal to the set temperature, supplying the vaporized gas cooled through the first compressor to the dual fuel engine.

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