KR20210023570A - Electricity generating system for ships - Google Patents

Abstract

Disclosed is a power generation system for a ship capable of operating a regasification facility without a large generator. According to an embodiment of the present invention, a power generation system for a ship may comprise: organic Rankine cycles in which the cycle is configured in the order of an evaporator, an expansion turbine, a vaporizer, a heat medium tank, and a pump on a heat medium circulation line in which a heat medium for vaporizing the liquefied gas is circulated; a generator for providing the necessary starting power when one of the organic Rankine cycles is operated; and a switchboard for controlling the amount of power generation of the generator according to the power production according to the operation of the organic Rankine cycle.

Description

Electricity generating system for ships

In the present invention, a small generator and a turbine for cooling and heat generation are connected to the main power system in the FSRU to which the direct propulsion engine is applied, and the power generation of a ship that can control the generation of the turbine for cooling and heat generation and the small generator in consideration of the amount of generation of each equipment monitoring and the total load of the ship. It's about the system.

Liquefied natural gas is a colorless, transparent, cryogenic liquid whose volume is reduced to 1/600 by cooling the natural gas collected from the gas field to a cryogenic temperature of about -162 degrees Celsius. Liquefied natural gas is transported and unloaded over a long distance from the production site to the customer by a liquefied natural gas carrier. The unloaded liquefied natural gas is regasified by the liquefied natural gas regasification facility installed at the onshore terminal, and then supplied to consumers such as homes and industrial complexes.

An onshore terminal equipped with such a regasification facility can be economically advantageous if it is constructed in a place where the natural gas market and demand are stably formed. However, in the case of demanders where the demand for natural gas is limited seasonally, short-term or periodically, the construction of an onshore terminal is uneconomical due to high installation and management costs.

Accordingly, in recent years, a liquefied natural gas regasification vessel (LNG RV, LNG Regasification Vessel) or a floating liquefied liquefied liquefied liquefied liquefied liquefied liquefied vessel (LNG RV, LNG Regasification Vessel) that has installed a regasification system on the liquefied natural gas carrier in order to regasify liquefied natural gas from the sea and supply natural gas directly to the customer. Natural gas storage and regasification facilities (FSRU, Floating Storage and Regasification Unit) have been developed and are being operated.

FSRU vessels use the same as LNG carriers when not operating regasification equipment, and operate regasification equipment by anchoring when operating regasification. When operating regasification equipment on FSRU ships, the electric propulsion method using the large generator is used even when propulsion because the electricity consumption is large, so a large generator must be used.

Since the electric propulsion method is less efficient than the direct gas propulsion method, when the LNG carrier mode does not operate regasification equipment, the fuel consumption is relatively higher than that of the direct propulsion type LNG carrier, which is disadvantageous in operation.

The present invention provides a power generation system for a ship capable of operating a regasification facility without a large generator.

The present invention provides a ship power generation system useful for a ship to which a direct propulsion engine is applied.

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

According to an aspect of the present invention, organic Rankine cycles consisting of cycles in the order of an evaporator, an expansion turbine, a vaporizer, a heat medium tank, and a pump on a heat medium circulation line through which a heat medium for vaporizing liquefied gas is circulated; A generator for providing starting power required when one of the organic Rankine cycles is operated; And a power generation system for a ship including a switchboard for controlling the amount of power generation of the generator according to power generation according to the operation of the organic Rankine cycle may be provided.

In addition, while the organic Rankine cycle operates, power generated from the expansion turbine is supplied to the switchboard, and the switchboard detects the amount of power supplied from the expansion turbine to reduce the load of the generator.

In addition, the organic Rankine cycles may be sequentially operated by receiving starting power from the generator one by one.

In addition, when the organic Rankine cycle is operated for a second time or more, starting power is provided from the generator during initial startup, and the entire power load may be adjusted by the switchboard while the organic Rankine cycle is normalized.

In addition, the maximum power generation amount of the generator may be greater than the sum of the power consumption of the ship and the starting power of one organic Rankine cycle, and less than the sum of the power consumption of the ship and the starting power of two organic Rankine cycles.

In addition, the switchboard is connected to a power plant on the land, and may transmit some of the power produced in the organic Rankine cycles to the power plant on the land.

In addition, the organic Rankine cycle further includes a first heat exchanger for heating the liquefied gas regasified by the vaporizer to a temperature required by the customer; The first heat exchanger receives a part of the heat medium vaporized by the evaporator through a first heat source supply line, and the first heat source supply line is branched from the front end of the expansion turbine to pass through the first heat exchanger and then the vaporizer Can be connected to.

In addition, the organic Rankine cycle may further include a pressure differential power generation turbine that generates power using the pressure of the vaporized liquefied gas discharged from the first heat exchanger.

In addition, it may further include a second heat exchanger for heating the vaporized liquefied gas discharged from the pressure difference power generation turbine to a temperature required by the customer.

According to the implementation of the present invention, it is possible to efficiently operate the regasification facility only with a small generator without a large generator.

According to an embodiment of the present invention, it is a power generation system suitable for converting an LNG carrier to which a direct propulsion engine is applied to an FSRU.

According to the practice of the present invention, it is useful for ships to which a direct propulsion engine is applied.

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

1 is a block diagram of a power generation system of a ship according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a control concept of a small generator and an expansion turbine in FIG. 1.
3 is a block diagram of a power generation system of a ship according to another embodiment of the present invention.
4 is a block diagram of a power generation system of a ship according to another embodiment of the present invention.
5 is a graph showing a temperature change according to a heat flow amount of a mixed refrigerant used in a liquefied gas regasification facility according to an embodiment of the present invention.
6 is a diagram showing the safety class classification criteria of refrigerant.
7 is a graph showing the temperature change characteristics according to the heat flow amount of the mixed refrigerant for each mixing ratio of the mixed refrigerant used in the liquefied gas regasification and cold heat power generation facilities.
8 is a graph illustrating a refrigerant characteristic curve showing the state of the heat medium according to the enthalpy and pressure of the heat medium.

Other advantages and features of the present invention, and a method of achieving them will become apparent with reference to embodiments to be described later in detail together 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 universal 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 subject matter 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 configurations. In order to help the understanding of the present invention, some configurations in the drawings may be somewhat exaggerated or reduced.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise", "have" or "have" are intended to designate the existence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification. It is to be understood that the possibility of the presence or addition of other features, numbers, steps, actions, components, parts, or combinations thereof, or any further features, is not preliminarily excluded.

1 is a block diagram of a power generation system of a ship according to an embodiment of the present invention, and FIG. 2 is a view showing a control concept of a small generator and an expansion turbine in FIG. 1.

The power generation system 10 of a ship according to an embodiment of the present invention regasifies liquefied gas such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG) to regasify natural gas (NG; Natural). A turbine for cooling and heating power generation by combining the power produced by using the cold heat of the liquefied gas and the power of a small generator in the heat exchange process of regasifying the liquefied gas while supplying fuel gas such as gas) and petroleum gas to the customer. It is a system that controls the amount of power generation and small generator.

1 and 2, the power generation system 10 of a ship according to the present embodiment includes organic Rankine cycles 100, gas generators 20, and a switchboard 30 (power management system). Can include.

In one embodiment, the organic Rankine cycle 100 is a liquefied gas transfer line 112, a vaporizer 120, a heat medium circulation line 130, a pump 140, a heat medium tank 150, an evaporator 160, an expansion turbine Includes 170. Here, on the heat medium circulation line 130 through which the heat medium is circulated, the evaporator 160, the expansion turbine 170, the carburetor 120, the heat medium tank 150, and the pump 140 are in the order of liquefied gas regasification and cold heat power generation. It can be called a system.

In the present embodiment, it is shown that three organic Rankine cycles 100 are provided, but the present invention is not limited thereto.

The generator 20 provides the required starting power whenever one of the organic Rankine cycles 100 is operated. The generator 20 may be provided as a set of two as a small generator. For example, the small generator may be, for example, a 3,700KW class generator.

The switchboard 30 may control the amount of power generation of the generator 20 according to power generation according to the operation of the organic Rankine cycle 100.

That is, while one organic Rankine cycle 100 operates, the power produced from the expansion turbine 170 is supplied to the switchboard 30, and the switchboard 30 senses the amount of power supplied from the expansion turbine 170, 20) reduce the load.

In the power generation system 10 of the ship, the three organic Rankine cycles may be sequentially operated to be operated by receiving starting power from the generator 20 one by one.

Referring to Figures 1 and 2, looking at the power operation in the power generation system 10 of the ship, the load of equipment, power consumption, and power generation are sensed by the switchboard 30, and the first organic Rankine cycle 100 is operated. In this case, the power consumption of the ship and the starting power of the organic Rankine cycle 100 are procured with the power generation amount of two small generators 20. At this time, a load control device (auto transformer, VFD, soft starter, etc.) may be used to protect the power system when major equipment such as a pump is used.

As the organic Rankine cycle 100 operates, the organic Rankine cycle 100 generates electric power from an expansion turbine (cooling and heat generating turbine) 170 therein, and this electric power is supplied to the switchboard 30. Power is supplied to the switchboard 30 and the load of the small generator 20 in operation is minimized by sensing the amount of power. When the second organic Rankine cycle 100 is operated, the amount of power used increases. At this time, the amount of power change is sensed, the load of the small generator 20 is increased again through the switchboard 30, and the second organic Rankine is increased through the increased amount of power. Run cycle 100. When the second organic Rankine cycle 100 is normally operated, the amount of power produced through the expansion turbine 170 of the second organic Rankine cycle 100 is sensed to minimize the load of the small generator 20 in the power operation system.

3 is a block diagram of a power generation system of a ship according to another embodiment of the present invention.

In describing the embodiment of FIG. 3, duplicate descriptions of components that are the same as or corresponding to the above-described embodiment may be omitted.

The power generation system 10a of the ship according to the embodiment of FIG. 3 further includes a first heat exchanger 180, a pressure differential power turbine 260, and a second heat exchanger 240. There is a difference.

In the organic Rankine cycle of the power generation system 10a of the ship (100a), it is necessary to raise the heat medium to the maximum pressure in consideration of the characteristic that the higher the temperature of the heat medium, the higher the pressure that can be operated while maintaining the gaseous state. However, there is a limitation in that the temperature of the liquefied gas vaporized by heat exchange with the heat medium in the vaporizer 120 must be adjusted to a temperature required by the customer. Because of this, there may be restrictions on the pressure conditions of the heating medium. In order to solve this limitation, as shown in FIG. 3, by additionally providing the first heat exchanger 180, the pressure drop of the heating medium is changed to the maximum to reduce the amount of cold heat generation. At the same time, it is possible to meet the gas temperature required by the customer.

The first heat exchanger 180 may receive a part of the heat medium vaporized by the evaporator 160 through a first heat source supply line (not shown). The first heat source supply line may be branched from the front end of the expansion turbine 170 to pass through the first heat exchanger 180 and then connected to the carburetor 120.

The first heat exchanger 180 is configured to receive the heat medium vaporized by the evaporator 160 through the first heat source supply line, and heat the vaporized liquefied gas by exchanging heat with the liquefied gas vaporized by the vaporizer 120 do.

The heat medium supplied through the first heat source supply line may be designed to be liquefied by heat exchange with the liquefied gas vaporized in the first heat exchanger 180 and supplied to the front end (or the rear end) of the vaporizer 120.

The pressure difference power generation turbine 260 may be an expansion turbine that generates power by directly using the pressure of the vaporized liquefied gas discharged from the first heat exchanger 180. The second heat exchanger 240 may heat the vaporized liquefied gas discharged from the pressure difference power generation turbine 260 to a temperature required by a customer.

The second heat exchanger 240 receives a portion of the heat medium vaporized by the evaporator 160 through a second heat source supply line (not shown), and the second heat source supply line is branched from the front end of the expansion turbine 170 After passing through the second heat exchanger 240, it is connected to the vaporizer 120.

According to the embodiment of FIG. 3, additional power generation is possible using the pressure of the gas at the rear end of the first heat exchanger 180 according to the pressure required by the customer. At this time, since the temperature drop also occurs according to the pressure drop of the gas in the pressure difference power generation turbine 260, the second heat exchanger 240 heats NG using seawater, steam, atmosphere, and waste heat in the ship to the customer. Supply. The turbine of the pressure differential power generation turbine 260 may be connected coaxially with the expansion turbine 170 used for cold and heat power generation of liquefied gas. Electric power generated from the pressure difference power generation turbine 260 may be provided to a switchboard.

4 is a block diagram of a power generation system of a ship according to another embodiment of the present invention.

In describing the embodiment of FIG. 4, duplicate descriptions of components that are the same as or corresponding to the above-described embodiment may be omitted.

The power generation system 10b of the ship according to the embodiment of FIG. 4 is different from the embodiment described above in that it is a configuration in which the onshore generator 50 is combined.

Referring back to FIG. 1, the organic Rankine cycle 100 (liquefied gas regasification and cold heat power generation facility) of the power generation system 10 of the ship according to the embodiment of the present invention is a mixture of refrigerants having a boiling point difference of at least 20°C or more. The liquefied gas is vaporized using the mixed refrigerant and the difference between the dew point temperature and the boiling point temperature is 10℃ or more in the pressure section of 10 ~ 20 barg, so that the temperature is increased in the phase change process in which the mixed refrigerant is vaporized in the evaporator. It can be increased, and the gasification efficiency of the liquefied gas can be increased.

The liquefied gas transfer line 112 of the organic Rankine cycle 100 according to this embodiment is provided to receive liquefied gas from an LNG storage tank (not shown), vaporize the supplied liquefied gas, and send it to a demander on land. Can be.

For example, a heat medium (mixed refrigerant) in which two or more non-combustible refrigerants are mixed may be circulated in the heat medium circulation line 130. In an embodiment, the ship's liquefied gas regasification system 100 may be configured with a single heat medium circulation line 130.

The heat medium circulates the pump 140, the evaporator 160, the expansion turbine 170, and the carburetor 120 through the heat medium circulation line 130. In order to increase the temperature of the mixed refrigerant in the process of vaporizing the mixed refrigerant in the evaporator 160 and changing the phase from liquid to gas, the heating medium is provided as a refrigerant mixed with refrigerants having a boiling point difference of at least 20°C, and mixed at the same time. The mixing ratio of the refrigerants may be set so that the difference between the dew point temperature and the boiling point temperature of the mixed refrigerant is 10°C or more in the 10 ~ 20 barg pressure (vapor pressure) section of the refrigerant.

The high-pressure booster pump 110 may pressurize and supply cryogenic liquefied gas from a liquefied gas storage tank or a buffer tank to the liquefied gas transfer line 112 in consideration of the pressure required at the place of use. The liquefied gas pressurized by the high-pressure booster pump 110 may be vaporized and heated through the vaporizer 120 to be supplied to a customer on land.

A heat medium for vaporizing liquefied gas is circulated in the heat medium circulation line 130. The heat medium may be, for example, a fluid and/or a mixture thereof shown in Table 1 below.

ethane Propane I-butane N-butane R13B1 R143a R134a R152a R22 R12 R13 R125 R500 R502 R507 R114 R14 R23 R744

The heat medium circulates through the heat medium tank 150, the pump 140, the evaporator 160, the expansion turbine 170, and the carburetor 120 in sequence along the heat medium circulation line 130. The vaporizer 120 regasifies the liquefied gas of the liquefied gas transfer line using the thermal energy and latent heat of the heating medium.

The heat medium tank 150 stores the heat medium discharged from the vaporizer 120. The heat medium tank 150 absorbs the pressure change of the heat medium according to the operating conditions, and maintains the heat medium in a set temperature range so that the heat medium can be operated in a predetermined pressure range. The heat medium tank 150 may be provided as an expansion tank. The heat medium tank 150 absorbs the pressure change of the heat medium according to the operating conditions, and maintains the heat medium recovered to the heat medium tank 150 in a set temperature range so that the heat medium tank 150 can be operated in a predetermined pressure range. Two or more types of liquefied refrigerants may be stored in the heat medium tank 150.

The pump 140 pressurizes the heat medium discharged from the heat medium tank 150 and circulates it in the heat medium circulation line 130. The pump 140 may be installed at a rear end of the heat medium tank 150 and a front end of the evaporator 160, and may be configured to pressurize the heat medium and supply it to the evaporator 160.

A first pressure sensor and a first temperature sensor are installed in the heat medium circulation line 130 between the vaporizer 120 and the pump 140. The first pressure sensor and the first temperature sensor measure the pressure and temperature of the liquid heat medium discharged from the vaporizer 120.

The evaporator 160 vaporizes the liquid heat medium discharged from the vaporizer 120 and circulating through heat exchange with a heat source. The heat source may be provided by seawater, steam, waste heat from an engine in a ship, or the like. For example, the evaporator 160 may evaporate the heat medium by heat exchange with a heat source supplied through a seawater line. The heat source may be supplied to the evaporator 160 through a seawater line by a seawater pressure pump (not shown). The inlet temperature of the evaporator of the heat source may be about 14° C., and the discharge temperature may be about 7 to 8° C. The evaporator 160 may be manufactured to withstand the pressure of the heating medium (eg, 10 to 20 barg vapor pressure).

When the evaporator 160 is made of, for example, a plate type heat exchanger (PHE) made of titanium, in order to use titanium with a thickness of 0.6 mm or less as a heat exchange plate, the design pressure (vapor pressure) of the heat medium is 16. It should be less than or equal to barg. If a titanium plate having a thickness of 0.7mm or more is used to increase the design pressure, the cost of equipment is greatly increased because the price increases by more than 10 times compared to a plate having a thickness of 0.6mm.

In the case of the mixed refrigerant, the dew point and the boiling point of the mixed refrigerant are changed according to the type of the mixed refrigerants and the mixing ratio of the refrigerants, thereby affecting the temperature change characteristics of the mixed refrigerant when the phase changes, as well as in the evaporator 160. During the phase change process, the pressure (vapor pressure) of the mixed refrigerant also changes. Accordingly, it is necessary to select the types of refrigerants and set the mixing ratio (weight ratio) so that desirable temperature change characteristics can be realized in the phase change section of the mixed refrigerant while minimizing the equipment cost of the evaporator 160.

In an embodiment of the present invention, in order to increase the temperature of the mixed refrigerant during the phase change of the heat medium in the evaporator 160, the liquefied gas may be regasified using a heat medium in which refrigerants having a boiling point difference of 20° C. or more are mixed. In addition, at a pressure of about 10 to 20 barg, the difference between the dew point temperature and the boiling point temperature of the heating medium is at least 10°C, while the pressure of the heating medium is about 20 barg or less (more preferably Is 16 barg or less), the mixing ratio (weight ratio) of the refrigerants may be set.

For example, the heating medium may include a first refrigerant and a second refrigerant having a boiling point lower than that of the first refrigerant by 20° C. or more. From the viewpoint of increasing the effect of increasing the temperature of the heating medium during the phase change of the heating medium in the evaporator 160, the boiling point of the second refrigerant is preferably 30° C. or more lower than the boiling point of the first refrigerant. 2 The difference in boiling point of the refrigerant is more preferably 50°C or higher.

The expansion turbine 170 is a device that generates electricity from the generator 174 by rotating the turbine 172 when a high-pressure fluid (vaporized heat medium) expands. For example, the expansion turbine 170 is installed between the evaporator 160 and the carburetor 120. The expansion turbine 170 generates power by the power of the heat medium vaporized by the evaporator 160.

A second pressure sensor and a second temperature sensor are installed between the evaporator 160 and the turbine 170. The second pressure sensor and the second temperature sensor measure the pressure and temperature of the heat medium vaporized in the evaporator 160.

A third temperature sensor is installed at the rear end of the vaporizer 120. The third temperature sensor measures the temperature of the liquefied gas vaporized by the vaporizer 120.

The flow rate of the heating medium may be controlled according to measured values of the first temperature sensor, the first pressure sensor, the second temperature sensor, the second pressure sensor, and the third temperature sensor.

Rankine cycle is applied to the cycle for recovering the cold heat of the liquefied gas. That is, the low temperature liquid heat medium is pressurized through the pump 140, and then vaporized and heated in the evaporator 160 through a heat source. Thereafter, a pressure drop occurs through the expansion turbine 170 for power generation, and thereafter, the low-pressure refrigerant is liquefied again through the vaporizer 120 and circulated.

When the Rankine cycle is applied, since there is a restriction to satisfy the gas temperature and pressure conditions required by the customer, the cold heat that can be recovered from the liquefied gas may be significantly reduced. Since the efficiency of cooling and heat generation depends on the type, pressure and flow rate of the heating medium, it is necessary to maximize the efficiency of cooling and heat generation by optimizing the pressure and flow rate of the pressurized heating medium.

The flow rate and pressure of the heat medium may be determined based on the temperature and pressure of the heat medium discharged from the vaporizer 120, the temperature of the heat source used in the evaporator 160, the pressure point of the heat medium, and the temperature of the gas sent to the customer.

5 is a graph showing the temperature change according to the heat flow amount of the mixed refrigerant used in the regasification of liquefied gas and the cold heat power generation system of a ship according to an embodiment of the present invention.

In FIG. 5, the horizontal axis represents the heat flow amount of fluids (seawater, LNG, mixed refrigerant), and the vertical axis represents the temperature of the fluids. The line marked'SW' is a graph of temperature change according to the heat flow of seawater, and the line marked'LNG' is a graph of temperature change according to the heat flow of liquefied natural gas.

According to the present embodiment, refrigerants having a large difference in boiling point are used as the mixed refrigerant, and in the temperature change graph according to the heat flow amount of the mixed refrigerant, the temperature gliding section in which the temperature increases when the phase change vaporized in the liquid state (A) appears, thereby satisfying the condition of the minimum temperature difference (ΔT) compared to the temperature of the liquefied natural gas, and heat exchange between the mixed refrigerant and the liquefied natural gas.

In the case of a single refrigerant, the temperature is constant or the temperature decreases while the phase change occurs, but when refrigerants having a boiling point difference of more than a set value are mixed, the temperature of the mixed refrigerant gradually increases while the phase change of the mixed refrigerant occurs in the evaporator 140. As it rises, a temperature gliding effect occurs at which the mixed refrigerant vaporizes.

When the phase change of the mixed refrigerant, the amount of temperature increase is 2 to 3°C or higher, preferably 10°C or higher, so that refrigerants having a large difference in boiling point are used, and the mixing ratio of the refrigerant having a low boiling point is at least a certain level (mixed refrigerant It is preferable to mix at least 5% by weight). Therefore, it is possible to implement a regasification system that satisfies the condition that the minimum temperature difference between natural gas and the mixed refrigerant is secured, and there is no need to install a trim heater at the rear end of the carburetor, and the thermal energy and latent heat of the mixed refrigerant are sufficiently utilized. Liquefied gas can be vaporized efficiently.

In addition, even when the temperature of the heat source is relatively low, such as seawater, efficient heat transfer to the liquefied gas is possible by using the latent heat of the mixed refrigerant, and the liquefied gas regasification and cold heat power generation system can be simplified and the operation efficiency can be increased. It is possible to increase safety compared to a system using a highly flammable heat transfer medium such as propane by comprising non-flammable refrigerants.

The conventional liquefied gas regasification system is operated by a vaporizer and a trim heater, and in order to operate the refrigerant in a liquid state in the trim heater, the regasifier must be operated at a high pressure to prevent vaporization of the refrigerant. There is a large difference in the operating pressure of the refrigerant between the and trim heaters.

However, according to the present embodiment, the pressure difference in the circulation loop of the heat medium circulation line 130 is small, and since the refrigerant circulates only a single heat exchange loop, it is only necessary to pressurize the pressure consumed in circulation and the head loss to recover the liquefied gas. Energy consumption for fire can be reduced.

As described above, according to the present embodiment, it is possible to maximize the effect of using latent heat of the mixed refrigerant to improve the liquefied gas vaporization performance, to reduce the amount of refrigerant used in the liquefied gas regasification and cold heat power generation system, and also, a trim heater is provided. There is no need to install, and the liquefied gas can be vaporized with a single vaporizer, thus simplifying the system configuration.

In addition, liquefied gas can be regasified by a single heat exchange process without going through two-stage heat exchange, and energy required for the pump and pipe size can be reduced by reducing the circulation flow rate of the mixed refrigerant. The cost can also be reduced.

In addition, according to an embodiment of the present invention, it is possible to implement a liquefied gas regasification system that efficiently utilizes the latent heat of the mixed refrigerant while changing the phase of the mixed refrigerant even in a low seawater design temperature range. In the case of using the evaporative mixed refrigerant, since the latent heat is much greater than the sensible heat, the flow rate of the circulating mixed refrigerant can be reduced, and thus the energy required for circulation of the mixed refrigerant is also reduced.

In order to maximize the temperature increase effect during the phase change of the mixed refrigerant as described above, the mixed refrigerant includes a first refrigerant having a boiling point of -40 to -10°C, and a second refrigerant having a boiling point of -60 to -90°C. Can include. A more preferable difference in boiling point between the first refrigerant and the second refrigerant is 50° C. or more.

In order to control the pressure of the mixed refrigerant below the design pressure of the evaporator 160 and at the same time obtain a temperature increase effect when the mixed refrigerant phase changes in the evaporator 160, the second refrigerant has a boiling point lower than that of the first refrigerant. The refrigerant may be mixed with the first refrigerant to have a weight ratio of 0.05 to 0.15 based on the weight of the mixed refrigerant.

The mixed refrigerant may be composed of refrigerants having a non-flammable property, an ozone depletion index of 0, and a global warming index of less than 2000. 3 is a diagram showing the safety class classification criteria for refrigerants. As shown in FIG. 6, the refrigerant is classified into safety grades according to toxicity and flammability.

In an embodiment, the refrigerants of the mixed refrigerant may be selected from refrigerants having a safety class of A1, except for refrigerants having a safety group of B1 to B3 or A2 to A3. That is, a mixed refrigerant can be formed in consideration of only refrigerants having a safety grade having low toxicity and low flammability. In addition, the refrigerants of the mixed refrigerant are preferably selected from eco-friendly refrigerants having an ozone depletion index of 0 and a global warming index of less than 2000 (more preferably less than 1500).

In an embodiment, the mixed refrigerant is tetrafluoroethane (1,1,1,2-tetrafluoroethane, R134a; CH ₂ FCF ₃ ) corresponding to the first refrigerant and carbon dioxide (R744; CO _{2) corresponding to the second refrigerant.} ), including at least two or more refrigerants. Two refrigerants (R134a, R744) are refrigerants classified as safety grades corresponding to A1, are non-toxic and non-flammable, and have an Ozone Depletion Potential (ODP) of 0. In addition, R744 refrigerant has a Global Warming Potential (GWP) of 1, and R134a refrigerant has a GWP of 1430, which is higher than R744 refrigerant, but has a lower value than the GWP standard suggested by various regulations and classification so that it satisfies the regulations. It is suitable for use.

Because R744 is more volatile than R134a, its boiling point is about 50°C or more. R134a has a boiling point of about -26℃, and R744 has a boiling point of about -78℃. Accordingly, when a mixed refrigerant in which two refrigerants R134a and R744 are mixed is used, a temperature gliding effect in which a temperature increases during a phase change due to a large difference in boiling point of the two refrigerants can be sufficiently obtained.

The mixed refrigerant may contain tetrafluoroethane (CH ₂ FCF ₃ , R134a) and carbon dioxide (CO ₂ , R744) in a weight ratio of 85 to 95% and 5 to 15% by weight, respectively. When the R744 refrigerant is contained in an amount of less than 5% by weight, it is difficult to obtain a temperature increase effect when the phase change of the mixed refrigerant due to the high boiling point difference between R744 and R134a.

Conversely, when the mixing ratio of the R744 refrigerant exceeds 15% by weight, the pressure of the mixed refrigerant in the evaporator 160 exceeds 20 barg due to the high content of R744 having high volatility, and withstands a high pressure of 20 barg or more. In order to be able to do so, there may be a problem in that the design thickness of the evaporator 160 must be increased.

7 is a graph showing temperature change characteristics according to the heat flow amount of the mixed refrigerant for each mixing ratio of the mixed refrigerant used in the liquefied gas regasification system of a ship according to an embodiment of the present invention. A mixed refrigerant mixed with CH ₂ FCF ₃ (R134a) and CO ₂ (R744) was used, and the temperature change characteristics of the mixed refrigerant while changing the weight ratio of R744 to 0.05, 0.1, and 0.15, the minimum between the mixed refrigerant and seawater (SW). The proximity temperature, the saturated vapor pressure of the mixed refrigerant in the evaporator, and the mixed refrigerant flow rate were measured.

Table 2 shows the minimum proximity temperature (minimum temperature between the mixed refrigerant and seawater) of the mixed refrigerant according to the weight ratio of _{CH 2} FCF ₃ (R134a) and CO _{2 (R744) constituting the mixed refrigerant, and the saturated vapor pressure of the mixed refrigerant (based on 50℃)} And changes in the flow rate of the mixed refrigerant. From Table 1, it can be seen that as the weight ratio of R744 increases, the saturated vapor pressure of the mixed refrigerant in the evaporator increases.

The more volatile of R134a and R744 is R744. The more R744 is mixed, the greater the temperature gliding effect during phase change of the mixed refrigerant, so that the refrigerant circulation flow rate decreases.However, the vapor pressure of the mixed refrigerant in the evaporator 140 increases, making a heat exchanger. May not satisfy the design pressure.

In the offshore platform or ship, there is a limitation that the system must be configured with a limited space compared to the onshore plant. On land, an open-rack vaporizer that vaporizes fluid using air or seawater can be used, but there are restrictions on installing and operating such a large-scale system on a ship. Accordingly, compact equipment such as a plate heat exchanger (PHE) and a printed circuit heat exchanger (PCHE) must be operated, and such equipment has limitations in manufacturing size and price.

In the evaporator 160 used in the circulation cycle of the mixed refrigerant, the performance, price, design pressure, etc. of the heat exchanger are determined according to the thickness of the plate, which is an internal component. In the refrigerant system, the system is operated by setting the system design pressure to the vapor saturation pressure at a specific temperature. Since R744 is more volatile than R134a, the design pressure increases as the mixing composition ratio of R744 increases.

Therefore, in order to satisfy the design pressure of the mixed refrigerant in consideration of the performance and price of the evaporator 160 used in the ship, it is preferable to control the mixing composition ratio of R744 to 15% by weight or less. Therefore, in order to obtain a temperature increase effect during phase change of the mixed refrigerant and to control the pressure of the mixed refrigerant below the design pressure, the mixing ratio of R744 is controlled so that 5 to 15% by weight of R744 is contained in the mixed refrigerant. It is desirable to do it.

When the evaporator is provided as a plate heat exchanger made of a 0.6mm thick tungsten plate to withstand the pressure of the mixed refrigerant (saturated vapor pressure) of 16 barg, the pressure of the mixed refrigerant in the evaporator (saturated vapor pressure) is 16 at an outside temperature of 50°. In order to satisfy the condition of barg or less, it is preferable that the mixing ratio of the second refrigerant R744 having a low boiling point among the mixed refrigerants is 10% by weight or less.

Table 3 shows the change in boiling point temperature and dew point temperature of the mixed refrigerant according to the pressure of the mixed refrigerant when the weight ratio of R134a and R744 is 0.95:0.05 and 0.85:0.15. When the ratio of R744 is high (when the weight ratio of R744 is 15%), the difference between the dew point temperature and the bubble point temperature of the mixed refrigerant increases, and the temperature increase effect increases when the mixed refrigerant phase changes. In addition, it becomes advantageous to use a mixed refrigerant within the limited temperature conditions of seawater and LNG.

When the ratio of R744 is low (when the weight ratio of R744 is 5%), the difference between the dew point temperature and the boiling point temperature of the mixed refrigerant decreases. When the weight ratio of R744 is less than 5%, the difference between the dew point temperature and the boiling point temperature of the mixed refrigerant at a vapor pressure of 10 to 20 barg decreases to less than about 10°C, resulting in a temperature increase effect when the phase change of the mixed refrigerant in the evaporator 140 May decrease. Therefore, it is desirable to keep R744 above 5% by weight.

8 is a graph illustrating a refrigerant characteristic curve showing the state of the heat medium according to the enthalpy and pressure of the heat medium.

1 and 8, the flow rate and pressure of the heat medium flowing into the expansion turbine 170 is such that the heat medium flowing into the expansion turbine 170 does not deviate from the gas-liquid mixing section in which the expansion turbine 170 can be operated normally. In addition, the heat medium discharged from the vaporizer 120 may be controlled to become a liquid. That is, when the heat medium introduced into the expansion turbine 170 is discharged, the pressure applied to the expansion turbine 170 may be limited so that it does not go beyond the operating gas-liquid mixing section.

It is to be understood that the above embodiments have been presented to aid understanding of the present invention, do not limit the scope of the present invention, and various deformable embodiments from this also fall within the scope of the present invention. The technical protection scope of the present invention should be determined by the technical idea of the claims, and the technical protection scope of the present invention is not limited to the literal description of the claims itself, but a scope that has substantially equal technical value. It should be understood that it extends to the invention of

10: power generation system of the ship 20: generator
30: switchboard 100: organic ranking cycle
110: high pressure booster pump 112: liquefied gas transfer line
120: carburetor 130: heat medium circulation line
140: pump 150: heat medium tank
160: evaporator 170: expansion turbine

Claims (9)

Organic Rankine cycles consisting of cycles in the order of an evaporator, an expansion turbine, a vaporizer, a heat medium tank, and a pump on a heat medium circulation line through which a heat medium for vaporizing liquefied gas is circulated;
A generator for providing starting power required when one of the organic Rankine cycles is operated; And
Power generation system of a ship comprising a switchboard for controlling the power generation amount of the generator according to the power generation according to the operation of the organic Rankine cycle. The method of claim 1,
While the organic Rankine cycle is operating, power generated from the expansion turbine is supplied to the switchboard,
The switchboard is a power generation system of a ship to reduce the load of the generator by sensing the amount of power supplied from the expansion turbine. The method according to claim 1 or 2,
The organic Rankine cycles are a power generation system of a ship that is sequentially operated by receiving starting power from the generator one by one. The method according to claim 1 or 2,
Second or more, when the organic Rankine cycle is operated, starting power is supplied from the generator at the initial start-up, and the total power load is adjusted by the switchboard while the organic Rankine cycle is normalized. The method of claim 1,
The maximum power generation amount of the generator is greater than the sum of the power consumption of the ship and the starting power of one organic Rankine cycle, and less than the sum of the power consumption of the ship and the starting power of two organic Rankine cycles. The method of claim 1,
The switchboard is connected to an onshore power plant,
A power generation system of a ship that transmits some of the power produced in the organic Rankine cycles to the onshore power plant. The method of claim 1,
The organic Rankine cycle
Further comprising a first heat exchanger for heating the liquefied gas regasified by the vaporizer to a temperature required by the customer;
The first heat exchanger receives a part of the heat medium vaporized by the evaporator through a first heat source supply line, and the first heat source supply line is branched from the front end of the expansion turbine to pass through the first heat exchanger and then the vaporizer The ship's power generation system that is connected to. The method of claim 7,
The organic Rankine cycle
Power generation system of a ship further comprising a pressure difference power generation turbine for power generation using the pressure of the vaporized liquefied gas discharged from the first heat exchanger. The method of claim 8,
Power generation system of a ship further comprising a second heat exchanger for heating the vaporized liquefied gas discharged from the pressure difference power generation turbine to a temperature required by the customer.

Images