KR20220068208A - Liquefied gas re-gasification system - Google Patents

Abstract

Disclosed is a liquefied gas re-gasification system using mixed refrigerant. The liquefied gas re-gasification system according to an embodiment of the present invention comprises: a liquefied gas transfer line gasifying the liquefied gas to deliver the same to a place of demand; a heat medium circulation line provided to transfer heat for gasifying the liquefied gas from a heat source, where a mixed refrigerant obtained by mixing two or more refrigerants is circulated; a pump installed on the heat medium circulation line to allow the mixed refrigerant to circulate through the heat medium circulation line; an evaporator installed on the heat medium circulation line to gasify the mixed refrigerant by exchanging heat with the heat source; a gasifier installed on the heat medium circulation line and using thermal energy and latent heat of the gasified mixed refrigerant to re-gasify the liquefied gas in the liquefied gas transfer line; and an expansion tank installed on the heat medium circulation line to store the mixed refrigerant liquefied in a process of heat exchange with the liquefied gas and absorb a change in pressure of the mixed refrigerant. Accordingly, the mixed refrigerant is used to re-gasify the liquefied gas with high efficiency.

Description

Liquefied gas regasification system {LIQUEFIED GAS RE-GASIFICATION SYSTEM}

The present invention relates to a liquefied gas regasification system, and more particularly, to a liquefied gas regasification system for regasifying liquefied gas using a mixed refrigerant.

Recently, as environmental regulations are intensified, the demand for fuels such as natural gas, which emits less environmental pollutants, is increasing. In order to supply natural gas to demand, a system for regasifying liquefied natural gas stored in a liquefied state in a liquefied gas storage tank is required. The conventional liquefied gas regasification system mainly uses an evaporative heating medium such as propane to receive heat from seawater and transfer the heat to liquefied natural gas (LNG) to regasify the liquefied natural gas into natural gas. are making

When designing to vaporize liquefied natural gas by one-time heat exchange treatment using propane, the size of the heat exchanger must be very large, so economical efficiency is reduced, the temperature condition of propane must be controlled in a very limited range, and the pressure drop in the heat exchanger And when the seawater temperature changes, there is a disadvantage in that it becomes difficult to supply natural gas at the temperature required by the consumer. For this reason, the conventional regasification system for liquefied natural gas is generally divided into a revaporizer for vaporizing the liquefied natural gas and a trim heater for heating the natural gas vaporized by the regasifier.

Propane circulates through the circulation pump, receives heat from seawater, and is cooled by primary heat exchange with natural gas in the first heat exchanger (trim heater). ), it is secondarily liquefied by heat exchange with liquefied natural gas. At this time, in the trim heater, heating is performed using the sensible heat of propane in a liquid state. In the case of such a liquefied gas regasification system, while the amount of heat required for LNG vaporization in the regasifier is larger than the amount of heat required for natural gas heating in the trim heater, the trim heater is heated using the sensible heat of propane in the liquid state. Due to this relationship, a larger refrigerant flow rate is required in the trim heater than in the regasifier. Therefore, since the conventional liquefied gas regasification system needs to circulate a refrigerant of an unnecessarily large flow rate with an excessive pressure difference, there is a problem in that the operating cost is increased and the efficiency is lowered.

The present invention provides a liquefied gas regasification system capable of regasifying the liquefied gas with high efficiency using a mixed refrigerant.

The problems to be solved by the present invention are not limited to the problems mentioned above. Other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description.

A liquefied gas regasification system according to an aspect of the present invention is a liquefied gas regasification system for regasifying liquefied gas, comprising: a liquefied gas transfer line for vaporizing the liquefied gas and sending it to a consumer; a heat medium circulation line that is provided to transfer heat for vaporizing the liquefied gas from a heat source and circulates a mixed refrigerant in which two or more refrigerants are mixed; a pump installed in the heating medium circulation line and circulating the mixed refrigerant in the heating medium circulation line; an evaporator installed in the heating medium circulation line and vaporizing the mixed refrigerant by heat exchange with the heat source; a vaporizer installed in the heating medium circulation line and re-vaporizing the liquefied gas of the liquefied gas transfer line using thermal energy and latent heat of the vaporized mixed refrigerant; and an expansion tank installed in the heating medium circulation line, storing the mixed refrigerant liquefied in the heat exchange process with the liquefied gas, and absorbing the pressure change of the mixed refrigerant.

A liquefied gas regasification system according to an embodiment of the present invention includes a temperature measuring unit for measuring the temperature of the mixed refrigerant returned to the expansion tank, and a temperature range in which the mixed refrigerant installed in the heat medium circulation line and recovered to the expansion tank is set. It may further include a pressure control valve controlled to maintain.

The liquefied gas regasification system according to an embodiment of the present invention supplies the refrigerant of the two or more components to the expansion tank, and when the operating temperature and pressure of the mixed refrigerant are out of a set range, adjusting the composition of the refrigerant of the two or more components It may further include a refrigerant charging line.

A liquefied gas regasification system according to an embodiment of the present invention includes: a bypass line installed to bypass the evaporator in the heating medium circulation line to control the temperature of the gas vaporized by the vaporizer; and a flow rate control valve installed in the bypass line to control a flow rate of the mixed refrigerant bypassing the evaporator according to the temperature of the vaporized gas.

The liquefied gas regasification system according to an embodiment of the present invention further includes an in-line mixer that mixes the mixed refrigerant in a liquid state that bypasses the evaporator through the bypass line and the mixed refrigerant vaporized in the evaporator and supplies it to the vaporizer can do.

A liquefied gas regasification system according to an embodiment of the present invention includes a temperature measuring unit for measuring the temperature of the gas vaporized by the vaporizer, and is installed in the heating medium circulation line to maintain the temperature range of the vaporized gas in a set temperature range. It may further include a controlled pressure regulating valve.

The liquefied gas regasification system according to an embodiment of the present invention may further include an auxiliary heater installed at the rear end of the evaporator in the heating medium circulation line, and supplementing the amount of heat when the heat source of the evaporator is insufficient.

The liquefied gas regasification system according to an embodiment of the present invention further includes a bypass line installed in the heating medium circulation line to bypass the auxiliary heater, and a valve installed in the bypass line to control the heating temperature of the mixed refrigerant. can do.

The liquefied gas regasification system according to an embodiment of the present invention further comprises a gas-liquid separator installed at the rear end of the evaporator in the heating medium circulation line and separating the mixed refrigerant into liquid and gas at the rear end of the evaporator, the gas-liquid The separator may supply the non-vaporized liquid mixed refrigerant to the auxiliary heater, and the vaporized mixed refrigerant may be supplied to the vaporizer by bypassing the auxiliary heater.

In the liquefied gas regasification system according to an embodiment of the present invention, seawater may be used as the heat source.

According to an embodiment of the present invention, a liquefied gas regasification system capable of regasifying the liquefied gas with high efficiency using a mixed refrigerant is provided.

The effects of the present invention are not limited to the effects described above. Effects not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention pertains from this specification and the accompanying drawings.

1 is a block diagram of a liquefied gas regasification system 100 according to an embodiment of the present invention.
2 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention.
3 to 10 are block diagrams of a liquefied gas regasification system according to still other embodiments of the present invention.

Other advantages and features of the present invention, and a method of achieving them, will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and the present invention is only defined by the scope of the claims. Even if not defined, all terms (including technical or scientific terms) used herein have the same meaning as commonly accepted by common technology in the prior art to which this invention belongs. A general description of known configurations may be omitted so as not to obscure the gist of the present invention. In the drawings of the present invention, the same reference numerals are used as much as possible for the same or corresponding components. In order to help the understanding of the present invention, some components in the drawings may be shown exaggerated or reduced to some extent.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In the present application, terms such as "comprise", "have" or "include" are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one It should be understood that it does not preclude the possibility of the presence or addition of or more other features or numbers, steps, operations, components, parts, or combinations thereof.

1 is a block diagram of a liquefied gas regasification system 100 according to an embodiment of the present invention. Referring to Figure 1, the liquefied gas regasification system 100 according to the present embodiment is a liquefied natural gas (LNG; Liquefied Natural Gas), liquefied petroleum gas (LPG; Liquefied Petroleum Gas), such as natural gas by regasification It may be provided in order to supply fuel gas, such as natural gas (NG) and petroleum gas (Petroleum Gas) to the demand.

In one embodiment, the liquefied gas regasification system 100 includes a liquefied gas transfer line 110 , a heat medium circulation line 120 , a pump 130 , an evaporator 140 , a pressure control valve 150 , and a vaporizer 160 . and an expansion tank 170 .

The liquefied gas transfer line 110 may be provided to receive liquefied gas from a liquefied gas storage tank, vaporize the supplied liquefied gas, and send it to a consumer.

The heating medium circulation line 120 may be provided to transfer heat for vaporizing the liquefied gas from the heat source. A mixed refrigerant in which two or more non-explosive refrigerants are mixed may be circulated in the heating medium circulation line 120 .

The pump 130 is installed at the front end of the evaporator 140 and the rear end of the vaporizer 160 in the heat medium circulation line 120 , and transfers the liquid mixed refrigerant stored in the expansion tank 170 through the heat medium circulation line 120 . It may be configured to be supplied to the evaporator 140 by pressing.

The evaporator 140 may be installed in the heat medium circulation line 120 and vaporize the mixed refrigerant by heat exchange with a heat source. In one embodiment, seawater may be used as the heat source.

The pressure control valve 150 is installed in the heat medium circulation line 120 , and may be provided to control the pressure (flow rate) of the mixed refrigerant supplied to the vaporizer 160 .

The vaporizer 160 is installed in the heating medium circulation line 120 , and may regasify the liquefied gas of the liquefied gas transfer line 110 by using the thermal energy and latent heat of the mixed refrigerant vaporized by the evaporator 140 .

The expansion tank 170 is installed in the heating medium circulation line 120, stores the mixed refrigerant liquefied in the heat exchange process with the liquefied gas in the vaporizer 160, and adjusts the pressure change of the mixed refrigerant according to the operating conditions. The mixed refrigerant that is absorbed and returned to the expansion tank maintains a set temperature range so that it can be operated within a set pressure range. Two or more types of liquefied refrigerants may be stored in the expansion tank 170 .

According to this embodiment, it is possible to efficiently vaporize the liquefied gas by using the thermal energy and latent heat of the mixed refrigerant. In addition, according to this embodiment, even when the temperature of the heat source is relatively low, such as seawater, efficient heat transfer to the liquefied gas is possible using the latent heat of vaporization of the mixed refrigerant, simplifying the liquefied gas regasification system, and increasing operating efficiency. can In addition, the liquefied gas can be regasified by a single heat exchange process without undergoing two-step heat exchange, and by using the latent heat of vaporization of the mixed refrigerant, the circulating flow rate of the mixed refrigerant can be significantly reduced, thereby reducing the process cost.

In addition, the conventional liquefied gas regasification system is operated as a regasifier (Vaporizer) and a trim heater (Trimheater), and in order to operate the refrigerant in a liquid state in the trim heater, it must be operated at a high pressure to prevent vaporization of the refrigerant. Although there is a large difference in the operating pressure of the refrigerant between the furnace regasifier and the trim heater, in the present invention, the pressure difference in the circulation loop is small and the refrigerant circulates only in a single heat exchange loop, so it pressurizes as much as the pressure consumed in circulation and the head loss This can reduce energy consumption for liquefied gas regasification.

2 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention. In the description of the embodiment of FIG. 2 , descriptions that overlap with the same or corresponding components as in the above-described embodiment may be omitted. The embodiment of FIG. 2 further includes a temperature measuring unit 180 that measures the temperature of the mixed refrigerant returned to the expansion tank 170 , and the pressure control valve 150 controls the mixed refrigerant returned to the expansion tank 170 . It is different from the embodiment described above in that the opening or closing degree is controlled to maintain a set temperature range.

3 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention. In the description of the embodiment of FIG. 3 , descriptions that overlap with the same or corresponding components as in the above-described embodiments may be omitted. The embodiment of FIG. 3 is different from the embodiments described above in that it further includes a refrigerant charging line 190 , a temperature gauge 200 , and a pressure gauge 210 .

The temperature measuring device 200 and the pressure measuring device 210 may measure the temperature and pressure of the mixed refrigerant in the expansion tank 170 or the temperature and pressure of the mixed refrigerant supplied from the expansion tank 170 .

The refrigerant charging line 190 supplies the refrigerant of two or more components to the expansion tank 170, and when the operating temperature and pressure of the mixed refrigerant are out of the set range, the composition of the refrigerant of the two or more components can be adjusted.

In an embodiment, the refrigerant charging line 190 may include a first refrigerant supply unit 192 , a second refrigerant supply unit 194 , and a controller 196 . The first refrigerant supply unit 192 supplies the first refrigerant to the expansion tank 170 . The second refrigerant supply unit 194 supplies the second refrigerant to the expansion tank 170 . The first refrigerant supply unit 192 and the second refrigerant supply unit 194 may each include a tank for storing refrigerant and a valve for controlling the amount of refrigerant supplied from the tank to the expansion tank 170 .

The controller 196 may control the first refrigerant supply unit 192 and the second refrigerant supply unit 194 based on the measured values of the temperature measuring instrument 200 and the pressure measuring instrument 210 . In one embodiment, the controller 196 stores in advance information on the optimum refrigerant mixing ratio that maximizes the regasification efficiency according to various process conditions such as temperature and pressure of the mixed refrigerant, and the optimum refrigerant mixing ratio according to the process condition of the mixed refrigerant. Thus, the first refrigerant supply unit 192 and the second refrigerant supply unit 194 may be controlled to supply the refrigerants to the expansion tank 170 .

Therefore, according to the present embodiment, by maintaining the temperature and pressure of the mixed refrigerant constant, it is possible to prevent a decrease in heat exchange efficiency due to a change in the vaporization temperature of the mixed refrigerant. For example, when the pressure of the mixed refrigerant increases, the vaporization temperature rises and when the pressure decreases, the vaporization temperature decreases, and when a difference from the initial design value occurs, the heat exchange efficiency decreases. According to the present embodiment, the composition ratio of the mixed refrigerant is adaptively adjusted in real time to prevent temperature and pressure changes of the mixed refrigerant, thereby preventing a decrease in heat exchange efficiency due to changes in temperature, pressure, and the like.

According to the mixing ratio of the mixed refrigerant, the gradient of the temperature change with respect to the vaporization flow of the liquefied gas is changed. The change in the slope of the mixed refrigerant is closely related to the change in flow rate and affects the operation efficiency. In extreme cases, the process may not operate normally or the liquefied gas regasification system may enter an area where it is not feasible due to the limitations of the heat exchanger performance.

Therefore, the controller simulates in advance the change in the temperature gradient of the mixed refrigerant according to the mixing ratio of the mixed refrigerant, and based on the simulation result, it is determined that there is a possibility that the regasification system may fail or enter the regasification impossible state. In this case, control such as maintaining the mixing ratio of the mixed refrigerant within a limited range or adjusting the flow rate of the mixed refrigerant may be performed.

4 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention. In the description of the embodiment of FIG. 4 , descriptions that overlap with the same or corresponding components as in the above-described embodiments may be omitted. The embodiment of FIG. 4 is different from the embodiments described above in that it further includes a bypass line 220 , a flow control valve 230 , and a temperature sensor 240 .

The bypass line 220 may be installed to bypass the evaporator 140 in the heating medium circulation line 120 in order to control the temperature of the gas vaporized by the vaporizer 160 . The flow rate control valve 230 is installed in the bypass line 220 , and may adjust the flow rate of the mixed refrigerant bypassing the evaporator 140 according to the temperature of the gas vaporized by the vaporizer 160 .

The temperature sensor 240 may measure the temperature of the gas vaporized by the vaporizer 160 . In one embodiment, when the temperature of the gas vaporized by the vaporizer 160 exceeds the set range, the opening degree of the flow control valve 230 may be increased to increase the flow rate of the mixed refrigerant bypassing the evaporator 140 . have. Conversely, when the temperature of the gas vaporized by the vaporizer 160 is less than the set range, the opening degree of the flow control valve 230 may be reduced to reduce the flow rate of the mixed refrigerant bypassing the evaporator 140 .

5 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention. In the description of the embodiment of FIG. 5 , descriptions that overlap with the same or corresponding components as in the above-described embodiments may be omitted. The embodiment of FIG. 5 is different from the embodiments described above in that it further includes an inline mixer 250 . The inline mixer 250 may mix the liquid mixed refrigerant bypassing the evaporator 140 through the bypass line 220 and the mixed refrigerant vaporized in the evaporator 140 and supply it to the vaporizer 160 .

6 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention. In the description of the embodiment of FIG. 6 , descriptions that overlap with the same or corresponding components as in the above-described embodiments may be omitted. The embodiment of FIG. 6 is different from the embodiments described above in that the pressure regulating valve 150 is configured to control the temperature of the gas vaporized by the vaporizer 160 to maintain a set temperature range.

7 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention. In the description of the embodiment of FIG. 7 , descriptions that overlap with the same or corresponding components as in the above-described embodiments may be omitted. The embodiment of FIG. 7 is different from the embodiments described above in that it further includes an auxiliary heater 260 . The auxiliary heater 260 is installed at the rear end of the evaporator 140 in the heating medium circulation line 120 , and may supplement the amount of heat when the heat source of the evaporator 140 is insufficient.

8 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention. In describing the embodiment of FIG. 8 , descriptions that overlap with the same or corresponding components as in the above-described embodiments may be omitted. The embodiment of FIG. 8 is different from the embodiments described above in that it further includes a bypass line 270 and a valve 280 . The bypass line 270 is installed to bypass the auxiliary heater 260 in the heat medium circulation line 120 . The valve 280 may be installed in the bypass line 270 to adjust the heating temperature of the mixed refrigerant supplied to the vaporizer 160 according to the opening/closing amount.

9 is a block diagram of a liquefied gas regasification system according to another embodiment of the present invention. In the description of the embodiment of FIG. 9 , descriptions of components identical to or corresponding to those of the above-described embodiments may be omitted. The embodiment of FIG. 9 is different from the embodiments described above in that it further includes a gas-liquid separator 290 . The gas-liquid separator 290 is installed at the rear end of the evaporator 140 in the heating medium circulation line 120 , and phase-separates the mixed refrigerant into liquid and gas at the rear end of the evaporator 140 . The gas-liquid separator 290 supplies the liquid mixed refrigerant not vaporized by the evaporator 140 to the auxiliary heater 260 through the first supply line 292, and the mixed refrigerant vaporized in the evaporator 140 is the second The auxiliary heater 260 is bypassed through the supply line 294 to be supplied to the vaporizer 160 .

It should be understood that the above embodiments are presented to help the understanding of the present invention, and do not limit the scope of the present invention, and various modified embodiments therefrom also fall within the scope of the present invention. The technical protection scope of the present invention should be determined by the technical spirit of the claims, and the technical protection scope of the present invention is not limited to the literal description of the claims itself, but is substantially equivalent to the technical value. It should be understood that it extends to the invention of

100: liquefied gas regasification system 110: liquefied gas transfer line
120: heat medium circulation line 130: pump
140: evaporator 150: pressure control valve
160: carburetor 170: expansion tank
180: temperature measuring unit 190: refrigerant charging line
192: first refrigerant supply 194: second refrigerant supply
196: controller 200: temperature meter
210: pressure gauge 220: bypass line
230: flow control valve 240: temperature sensor
250: inline mixer 260: auxiliary heater
270: bypass line 280: valve
290: gas-liquid separator 292: first supply line
294: second supply line

Claims (1)

In the liquefied gas regasification system for regasifying liquefied gas,
a liquefied gas transfer line for vaporizing the liquefied gas and sending it to a consumer;
a heat medium circulation line that is provided to transfer heat for vaporizing the liquefied gas from a heat source and circulates a mixed refrigerant in which two or more refrigerants are mixed;
a pump installed in the heating medium circulation line and circulating the mixed refrigerant in the heating medium circulation line;
an evaporator installed in the heat medium circulation line and vaporizing the mixed refrigerant by heat exchange with the heat source;
a vaporizer installed in the heating medium circulation line and re-vaporizing the liquefied gas of the liquefied gas transfer line using thermal energy and latent heat of the vaporized mixed refrigerant;
a flow rate control valve installed in the heating medium circulation line and controlling the flow rate of the mixed refrigerant;
an expansion tank installed in the heating medium circulation line, storing the mixed refrigerant liquefied in the heat exchange process with the liquefied gas, and absorbing the pressure change of the mixed refrigerant;
an auxiliary heater installed at the rear end of the evaporator in the heating medium circulation line and supplementing the amount of heat when the heat source of the evaporator is insufficient;
and a gas-liquid separator installed at the rear end of the evaporator in the heat medium circulation line and separating the mixed refrigerant into liquid and gas at the rear end of the evaporator,
The gas-liquid separator is a liquefied gas regasification system for supplying the non-vaporized liquid mixed refrigerant to the auxiliary heater, and supplying the vaporized mixed refrigerant to the vaporizer by bypassing the auxiliary heater.

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