JP2016008042A - Binary power generation system for lng ship - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binary power generation system in which cold with ultra low temperature which LNG has, is collected for using the cold as a cold source, and a binary cycle in which the cold is combined with other heat source with high temperature, is assembled.SOLUTION: Alternative flon or the like is employed as a working fluid, and ultra low temperature of LNG is utilized for performing cooling and liquifaction of the flon to low temperature about minus dozens of °C and low pressure in a vacuum area. After pressure is raised by a pump 2, the alternative flon is subjected to vaporization and heating by sea water and a high temperature heat source related to a main machine, for making overheated gas. A turbine 14 is driven for rotating a power generator 15 directly connected thereto, for taking out power. On a condenser 21 in the vacuum area, air immersion is prevented by a double structure of the condenser in which the working fluid is filled in the surrounding. The working fluid with low temperature is temperature raised by sea water in advance, for preventing condensation and creation of moisture and sulfur oxide. The LNG fluid is compressed and then serves as a cooling source of the working fluid of the binary system, and at the same time, the LNG fluid is subjected to vaporization and heating by the heat source related to the main machine, for making overheated gas, for rotating a turbine 42 for generating power, similarly.

Description

  The present invention relates to a binary power generation system for a ship that uses both cold heat of LNG and a high-temperature source of a main engine as both heat sources.

Use drawings.

  This application collects the cold heat of LNG in the ship as a cooling source, uses exhaust gas from the main engine of the ship, scavenging or cooling water as the heating source, while working fluid has less impact on ozone layer destruction and global warming It uses a medium to disclose power generation system technology that is excellent in energy saving and global environmental compatibility.

  In a conventional ship LNG fuel system, LNG is vaporized and heated by steam, seawater, or air in order to obtain LNG gas at room temperature necessary for fuel supply to the main engine. Although the heater is provided, the cold heat obtained at that time is wasted to the atmosphere via the above-described heating medium. That is, no cold energy is recovered.

  In the power generation system that drives the turbine by pressurizing, evaporating, and overheating the LNG liquid in the ship's fuel system, the process of cooling and condensing the working fluid of the other binary power generation system is combined with the process of evaporating and overheating the LNG. Heat exchange between the working fluids of the LNG and the binary power generation system can be efficiently performed by exchanging both media directly with a heat exchanger, or by exchanging heat through a brine having a low freezing temperature. There is no system for extracting output by serial operation of the LNG Rankine cycle to be used and a binary cycle such as Freon.

  Water or air is used as a cooling source for conventional binary power generation systems, and the working fluid is directly heat-exchanged with ultra-low-temperature liquefied gas, or heat is exchanged via a brine having a low freezing temperature. Therefore, there is no system that cools to minus tens of degrees Celsius. Alternatively, when the working fluid is cooled through an intermediate medium such as water, a system for cooling to minus several tens of degrees Celsius cannot be established. In other words, there is no system that extends the operating range to the freezing temperature range of the working fluid or the intermediate heating medium.

  Since the condensing temperature of the conventional working fluid condenser is at most in the range of 10 ° C. to 30 ° C., the condensing pressure of the working fluid is maintained at a pressure higher than the atmospheric pressure. There is no fear of intrusion. That is, in the conventional system, the following three items are not taken into consideration: (1) The pressure of the condenser becomes a vacuum pressure below the atmospheric pressure, and there is a risk of air leakage from the surroundings; (2) The working fluid There is a risk of pump gas suction due to a decrease in the suction pressure of the booster pump. (3) Consideration of the structure of the condenser corresponding to the condensation temperature of minus tens of degrees Celsius.

  During the process of vaporization and overheating of the working fluid, the exhaust gas and scavenging of the main engine, which is the heating medium, is cooled, the moisture contained in it is condensed, and further solidified to adhere to the outer surface of the heat exchanger to improve heat transfer efficiency. No consideration has been given to the deterioration of the heat exchange efficiency due to the deterioration and further the corrosion of the wall surface of the heat exchanger caused by the dissolution of the sulfur oxide SOx component in the condensed water.

  Generally, in a binary system of a ship, exhaust gas, scavenging, or cooling water is used as a heating source, and after LNG is used as a cooling source, the LNG as a cooling source is consumed in its entirety after consumption of the equivalent amount of both heat sources. There is a margin and a residue is generated. A double series binary power generation system in which a binary system is provided as a new system using the remainder as a heating source and seawater or the like as a cooling source is not seen.

JP2009-221961A (P2009-221961A) Japanese Laid-Open Patent Publication No. 11-148428

  In order to preserve the global environment and prevent air pollution in the sea area by the international organization related to maritime affairs, the IMO emissions from the components contained in the exhaust gas during fuel combustion of the main engine for all ships of any ship type As a result, it is obliged to use LNG with a low global environmental load as fuel in a wide range of sea areas. Responding to changes in the marine transportation environment such as the rapid increase in the number of LNG fueled ships, it is possible to save energy by effectively using the cold heat of the ultra-low temperature LNG released into the atmosphere when converting LNG into fuel gas for the main engine. The significance of the corresponding ship is great.

  Production of shale gas, mainly in the United States, has been started, and the natural superiority of natural gas is being established by receiving abundant supply of natural gas. On the other hand, coupled with the increasing demand for clean energy sources in each country, an increase in the amount of LNG transported by the sea and the number of LNG transporters built are becoming prominent worldwide. In connection with this, LNG transport ships can recover the cold heat of LNG's natural vapor from tanks that had previously been thrown away into the atmosphere, and convert it into energy production in another form. It is also meaningful from the viewpoint of contributing to the global environment.

  Energy conservation in ships is an indispensable requirement for improving operational profitability, and one direction is to improve the energy efficiency of the equipment currently installed, with the main engine at the top, and the shipbuilding industry There is a fierce development competition. However, there is another way of thinking, which is to create new power by effectively utilizing the thermal energy that existing equipment has or releases without consuming new energy resources such as fossil energy. It is an idea of energy.

  From the viewpoint of the thermal energy of a ship, there are various existing ones that are released from the main engine. On the other hand, LNG has emerged as a propulsion energy source for ships as described above. The number of LNG transport ships is also increasing. What is common to both is that an unprecedented ultra-low temperature cold heat source has been added to the ship. That is, in recent years, existing high-temperature heat sources centering on the main engine and new ultra-low temperature cold heat sources by LNG have come to coexist on ships. From the viewpoint of thermal energy, the existence of the high-temperature heat source and the low-temperature heat source can be worked by assembling a Rankine cycle (steam-driven prime mover cycle) between them, and from there, it is possible to extract power and power.

  However, the heat source on the high temperature side is mainly the exhaust gas after combustion, scavenging or cooling water in the main engine, and the temperature level is not high. When LNG is used as a cooling source, heat exchange with ultra-low temperature is performed. For this reason, the working fluid when the Rankine cycle is configured between the two heat sources must be suitable for those temperatures, and at the same time, there is no ozone layer destruction and a low global warming potential from the viewpoint of the global environment. There is a need to. Also, conventional water is not suitable due to the condition of using a cryogenic cooling source. Therefore, the refrigerant used in the refrigeration cycle is selected, but considering the global environment, there is no need to destroy the ozone layer and the global warming potential should be small. The

  Since the cooling source is an ultra-low temperature LNG, the temperature of the working fluid cooled by the recovered cold heat is minus several tens of degrees Celsius, and the pressure is a negative vacuum. Conventional heat exchanger structure suitable for both, selection of equipment materials, measures against gas leakage from the surroundings, smooth liquid suction and discharge function of the pump, lubrication means of the rotary bearing and freezing of the working fluid It is necessary to take measures that are not present.

  In general, in the case of a ship, the amount of heat of the LNG serving as a cold heat source and the amount of the heat source such as the amount of exhaust gas, the amount of scavenging and the amount of cooling water of the main engine serving as the heat source are larger for the high temperature heat source, and the amount of LNG of the cold heat source After consuming an equivalent amount of heat source, an excess heat source remains. If this is thrown away, the effective energy is wasted. By configuring a separate binary power generation system that uses a surplus heat source and seawater as a cooling source and connecting them in series, it is possible to extract more output.

  In the case of an LNG fuel ship, the high-pressure LNG liquid pumped from the LNG tank is currently sent to the main engine as it is after vaporization and temperature rise. If the degree of pressure increase of the LNG liquid is increased and further vaporization, temperature rise and overheating, the differential pressure from the gas pressure required in the main engine can be taken out as work. Furthermore, if the heat released during the cooling and condensation of the binary system working fluid is used to vaporize and raise the temperature of the LNG liquid, the two systems of the LNG liquid and the binary system working fluid can be used thermally and effectively. It is.

  When exhaust gas or scavenging gas is used as a heat source for vaporizing and raising the temperature of a low-temperature low-temperature working fluid, moisture and sulfur oxide contained in these gases can condense and solidify in a low-temperature heat exchanger. There is sex. These cause deterioration of the heat exchange efficiency, and further cause corrosion of the heat exchanger tube by the sulfur oxide solution in the exhaust gas. It is necessary to take measures against this.

  In order to solve the above problems, in the invention according to claim 1, a binary power generation system that is one form of Rankine cycle is used as a form of power generation. A closed loop that circulates the working fluid using exhaust gas, scavenging, or cooling water from the main engine as a high heat source and LNG and seawater as a cold heat source is configured. As a cooling system for the working fluid, the discharge gas from the turbine is first cooled with seawater, further cooled with a regenerator, then cooled and condensed in a condenser using LNG, which is ultra-low temperature, and the condensate is pumped by a pump. Boost and circulate. The working fluid after pump discharge is heated with seawater after exchanging heat with the turbine discharge gas in the regenerator, further heated with exhaust gas, scavenging or cooling water and sent to the turbine as superheated gas. Power is generated by turning a directly connected generator. As a working fluid of a binary power generation system, a material that is compatible with the above-mentioned high heat source temperature and cold heat source temperature and at the same time has little influence on the global environment is targeted. That is, it does not cause thermal decomposition at high temperature, does not cause freezing at low temperature, does not cause destruction of the ozone layer, and has little influence on global warming.

  In the invention according to claim 2, in the case of an LNG fuel ship, the pressure of the LNG liquid is once increased by a pump, and further, the working fluid of the binary power generation system is vaporized while being cooled in the condenser, and then heated and heated by the superheater. The power is generated through the work and then supplied as fuel for the main engine. At this time, the working fluid of the binary power generation system is cooled / condensed by the latent heat generated in the process of vaporizing / heating the LNG liquid and the cold by sensible heat. That is, binary power generation is performed by utilizing the cold energy of the LNG liquid main body, and at the same time, the LNG liquid is generated by the high-pressure gas obtained after vaporization, and both systems are coexisted and simultaneously operated to increase the power generation output.

  In the invention according to claim 3, when LNG is used as a cooling source in the condenser of the working fluid, the temperature is a low temperature of minus several tens of degrees Celsius, and the pressure is a negative vacuum. In this state, when the air around the condenser leaks into the condenser, the saturation pressure rises because the air is a non-condensable gas, and the condensation temperature becomes lower. It becomes impossible. Therefore, in the present invention, the condenser has a double structure having a space in the middle, the outer surface of the inner tank is insulated, and the inner space is connected by a pipe from a separate working fluid liquid tank via a pressure regulating valve. The working fluid gas is supplied to maintain the space at a slight positive pressure. This pressure regulating valve automatically opens and closes according to the pressure in the double structure space of the condenser.

  In the invention according to claim 4, the condenser is provided with a liquid pool portion or a working fluid liquid tank connected to the condenser, the pump body is submerged type submerged in the working fluid, and the rotating shaft is lubricated. Self-lubricating with the working fluid itself. The discharge amount of the pump is controlled according to the depth of the liquid level, or positive NPSH is always maintained as operation at a certain liquid level or higher.

  In the invention according to claim 5, in order to prevent condensation and solidification of moisture in the exhaust gas or scavenging used for the heat source of the working fluid or LNG, and the superheater, and further generation of a sulfur oxide solution by the condensed water Then, a vaporizer or heater made of seawater is provided upstream of the working fluid or LNG superheater, and the working fluid or LNG temperature is raised to room temperature. This prevents moisture condensation and solidification and the formation of a sulfur oxide solution.

  In the invention according to claim 6, there is provided an automatic flow rate adjusting valve for detecting the temperature of the working fluid in the condenser cooled by LNG and reducing the flow rate of LNG when the temperature falls below the solidification temperature of the working fluid. The reduced amount of LNG flows into the bypass circuit, and the temperature of the entire amount of LNG is raised by another means such as a steam heater provided in the downstream.

  In the invention according to claim 7, in order to effectively use the surplus high heat source, a subordinate independent binary power generation system using the surplus high heat source and seawater as both heat sources is installed downstream of the main binary power generation system.

  In the invention according to claim 1, the condensation temperature is conventionally increased by using a heat source related to the main engine that can be obtained abundantly as a heat source, using ultra-low temperature LNG as a cold heat source, and selecting a low-boiling working fluid. Compared to water, the temperature can be lowered by several tens of degrees Celsius, and the discharge pressure of the turbine determined by the condensation temperature can be lowered, and the heat drop and pressure difference in the turbine can be increased. The turbine output can be increased. By appropriately selecting the working fluid, it is possible to circulate in the system without disassembly or freezing at the temperature of the high heat source and the cold heat source, and smooth operation is achieved. At the same time, the ozone layer is not destroyed by the working fluid, and at the same time, adverse effects on the global environment related to global warming can be minimized.

  In the invention according to claim 2, the Rankine cycle is configured using the LNG main body, which is the fuel of the LNG fuel ship, as the working fluid, and the turbine is driven by effectively using the high-temperature and high-pressure steam after the LNG liquid is vaporized. Power is generated by a generator directly connected to Furthermore, the cold energy generated in the process of vaporizing and raising the temperature of the LNG liquid is used for cooling and liquefying the working fluid in a separate binary power generation system, thereby generating power in the binary power generation system. Thus, both the LNG power generation system and the binary power generation system are connected to each other by effective mutual use and sharing of the heat source, and the power generation output is increased.

  In the invention according to claim 3, the inside of the condenser is in a low temperature and vacuum state, but even when leakage occurs in the condenser, only the same gas as the working fluid enters, and there is no invasion of air which is a non-condensable gas. Therefore, the condensation function is not impaired. Since the internal space of the double structure is kept at room temperature by heat insulation applied to the outer surface of the inner wall of the double structure, the gas existing in the space is not liquefied. Gas is automatically supplied from an external working fluid tank by a pressure regulating valve so that the space is maintained at a constant pressure.

  In the invention according to claim 4, the working fluid cooled and liquefied by LNG has a low temperature of minus several tens of degrees Celsius, and normal lubricating oil does not function. Accordingly, the working fluid pump is a submerged type submerged in the working fluid liquid, and the rotating shaft is lubricated by the self-lubricating type performed by the working fluid itself, so that a smooth rotating function is maintained. On the other hand, by controlling the liquid level in the condenser, the number of revolutions of the pump is automatically controlled according to the liquid level of the working fluid, so that the suction pressure of the pump is always NPSH (net positive suction pressure). In order to be maintained, the pump operates normally without inhaling gas.

  In the invention according to claim 5, since the low-temperature working fluid or LNG is heated to normal temperature by seawater before it comes into contact with the exhaust gas or scavenging gas containing moisture and sulfur oxide through the heat exchanger, There is no condensation and solidification of moisture in the exhaust gas or scavenging in the exchanger, or the generation of the resulting sulfur oxide solution. Operation becomes possible.

  In the invention according to claim 6, the flow rate of the ultra-low temperature LNG that is a cooling source flowing to the binary power generation system is reduced to prevent freezing of the working fluid in the condenser, and the reduced amount of LNG is heated separately. Maintaining normal operation of the main engine fuel system of the ship by raising the temperature by means.

  In the invention according to claim 7, the conventional high-temperature heat source exists in excess of the LNG system cold heat source, and the conventional binary power generation system using seawater as the cold heat source by utilizing the surplus high heat source is replaced with LNG. It is configured by connecting in series with the main binary power generation system as a cooling source, aiming to increase output and create energy by effectively using the heat source as a whole ship.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
As a working fluid, an alternative chlorofluorocarbon-based HFC134a will be described as an example. The same applies to the case of using other refrigerants.

  FIG. 1 shows a main LNG fuel system in an LNG fuel ship and an LNG transport ship. FIG. 1A shows a fuel system of an LNG fuel ship, and FIG. 1B shows a fuel system of an LNG transport ship. In either case, the LNG is heated from the LNG tank to the superheated steam at room temperature with an evaporator and a heater using steam as a heating source, and is supplied to the main machine as it is. That is, LNG cold recovery and utilization are not made. Similarly, the exhaust gas, the scavenging air and the cooling water from the main engine are discarded without being used for the heat medium at the 100 ° C. to 200 ° C. level.

  FIG. 2 shows a system in which a closed circuit is formed by the working fluid of the power generation system in the LNG transport ship according to the present embodiment. First, as for the high heat source, the working fluid is heated using the exhaust gas, scavenging gas or cooling water of the main engine to produce superheated gas and the turbine is rotated, and the working fluid is condensed using ultra-low temperature vaporized vapor from the LNG tank. For the vaporization and cooling of the working fluid, seawater is also used to save energy. The outside of the condenser to be evacuated is filled with a working fluid gas in the double structure to prevent air from entering.

  FIG. 3 shows a system in which a closed circuit is formed by a working fluid in the power generation system in the LNG fuel ship according to the present embodiment. The high temperature source is the same as that of the LNG transport ship in FIG. For the cold heat source, the latent heat of the LNG liquid pumped from the LNG tank and the total cold heat of sensible heat are used. The cooling method of the working fluid using seawater and the mechanism of the vacuum condenser are the same as in FIG. The LNG steam after recovering the cold heat forms a Rankine cycle with superheated steam obtained using a high-temperature source such as seawater, exhaust gas, or cooling water, and drives the turbine to generate power.

  FIG. 4 shows three types of cycles when the HFC-134a according to the present embodiment is used as a working fluid, represented by a solid line, a chain line, and a dotted line on a diagram in which the vertical axis represents pressure p and the horizontal axis represents enthalpy h. Thus, the working fluid circulates in the direction of the arrow and functions in the closed circuit system as indicated by the solid line.

  FIG. 5 shows two types of cycles when the HFC-134a according to the present embodiment is used as a working fluid on a diagram in which the vertical axis indicates temperature T and the horizontal axis indicates entropy s. This is essentially the same as FIG. 4 except that the physical quantity index expressed as the vertical axis and the horizontal axis is different.

  FIG. 6 shows the Rankine cycle flow using LNG of the LNG fuel ship according to the present embodiment as a working fluid on a diagram in which the vertical axis represents pressure p and the horizontal axis represents enthalpy h, and the working fluid is opened. It functions by flowing in the direction of the arrow on the solid line in the system that becomes the circuit, and finally used as the main engine fuel.

A conventional LNG fuel ship and an LNG fuel system in an LNG transport ship will be described with reference to FIG.
FIG. 1A shows a fuel system in a conventional LNG fuel ship. LNG is pumped directly from a tank 01 and flows in a liquid state through a supply pipe 02 to an LNG evaporator 03, where it is heated by hot steam 04. After being heated and further vaporized, it enters the LNG heater 05 where it is heated again by the water vapor 04 and supplied to the main machine as a normal temperature gas 06. That is, the vaporization of LNG, the latent heat of the low-temperature gas and the total sensible heat of sensible heat are not used effectively but are discarded to the atmosphere. In addition, new high-temperature steam is required to take away the total cooling heat of LNG.
FIG. 1B shows a fuel system of a conventional LNG transport ship. LNG is supplied as low-temperature steam evaporated from a tank 01 and enters a LNG heater 05 through a supply pipe 07, where it is heated to room temperature by high-temperature steam 04, Supplied to the main machine as room temperature gas 06. That is, here too, there is no use of the cold heat of ultra-low temperature LNG, and high-temperature steam is consumed to raise the temperature of the steam. Various high-temperature heat sources released from one main engine are discarded without being used.

  An LNG cold recovery system in the case of the LNG transport ship according to this embodiment, that is, a working fluid condensing system of the binary power generation system will be described with reference to FIG. LNG, which is a cold heat source, is taken out from the LNG tank 30 as evaporating vapor, is pressurized by the compressor 31b, and then led to the condenser 21 through the gas supply pipe 32b. In the condenser 21, the low-temperature LNG evaporating vapor liquefies the working fluid at a predetermined condensation temperature by cooling the working fluid through the tube wall, and is stored as the working fluid liquid 1 at the bottom of the condenser. When the condenser temperature falls below the freezing temperature of the working fluid, it is detected by the temperature regulator 33, the gas bypass valve 34b is opened, and the low-temperature LNG vaporized vapor bypasses the condenser 21 and remains as it is in the gas heater 35. Sent to. The LNG gas that has exited the condenser 21 and the gas bypass valve 34 b is heated to room temperature by the gas heater 35 and guided to the main machine 36.

Hereinafter, in FIG. 2 and FIG. 3, devices having common functions are denoted by the same reference numerals and common description will be given.
First, referring to FIG. 2 and FIG. 3, the pressurization and delivery of the working fluid from the condenser according to the present embodiment common to the LNG transport ship and the LNG fuel ship will be described.
The working fluid is maintained at the liquid level by the pump 2 so that the NPSH (net positive suction pressure) necessary for the normal operation of the pump 2 is obtained from the condenser 21 by the liquid level controller 28 and the flow control valve 29. The pressure is increased and pumped, and the high pressure working fluid 3 is guided to the regenerator 4. The pump 2 is a self-lubricating type in which the working fluid itself is used for lubricating the rotating shaft, and is a submerged type in the working fluid.

  With reference to FIGS. 2 and 3, the regeneration function of the working fluid according to this embodiment common to the LNG transport ship and the LNG fuel ship will be described. The discharge gas 16 of the turbine 14 is cooled to room temperature in a gas cooler 18 by a seawater line 17, and then is transported to the regenerator 4 to be heat-exchanged with the low-temperature high-pressure working fluid 3 and further cooled to form a low-temperature gas 20. It is condensed after being led to the condenser 21. One high-pressure working fluid 3 is heated in the regenerator 4. Thus, the regenerator 4 has a function of increasing the overall thermal efficiency by performing mutual heat exchange between the two fluids.

  The function of vaporizing and heating the working fluid according to this embodiment common to the LNG transport ship and the LNG fuel ship will be described with reference to FIGS. The working fluid exiting the regenerator 4 enters the vaporizer 5 and is vaporized by being given latent heat by the seawater supply 6. The flow rate of the seawater to be applied is determined from the viewpoint of preventing freezing of the seawater on the surface of the pipe through which the working fluid flows. The working fluid after vaporization similarly enters the heater 7 by the seawater supply 8, where it is heated to room temperature and becomes room temperature gas 9. The vaporizer 5 and the heater 7 can be combined as one device. In this case, the working fluid is vaporized and the temperature is raised to room temperature by seawater in one device.

  The function of overheating the working fluid according to this embodiment common to the LNG transport ship and the LNG fuel ship will be described with reference to FIGS. The room temperature gas 9 enters the superheater 10 and is heated to the superheated region 12 by the exhaust gas, scavenging or cooling water heating source supply 11 to become the superheated gas 12.

  The work extraction by the working fluid according to the present embodiment common to the LNG transport ship and the LNG fuel ship will be described with reference to FIGS. The superheated gas 12 enters the turbine 14 through the gas pressure regulating valve 13 and performs rotational work by the expansion process of the gas. The generator 15 located on the same axis is rotated, and the output is taken out as electric power. The working fluid that has worked in the turbine is depressurized and cooled and flows as discharge gas 16 to the gas cooler 18 where it is further cooled by seawater supply 17 and led to the regenerator 4 as room temperature gas 19.

  An LNG cold recovery system in the case of the LNG fuel ship according to the present embodiment, that is, a working fluid condensing system of the binary power generation system will be described with reference to FIG. LNG, which is a cold heat source, is boosted and pumped from the LNG tank 30 by the LNG pump 31a, and led to the condenser 21 through the LNG supply pipe 32a. In the condenser 21, the low-temperature LNG evaporating vapor liquefies the working fluid at a predetermined condensation temperature by cooling the working fluid through the tube wall, and is stored as the working fluid liquid 1 at the bottom of the condenser. When the condenser temperature falls below the freezing temperature of the working fluid, it is detected by the temperature regulator 33, the LNG bypass valve 34a is opened, and the LNG liquid bypasses the condenser 21 and is sent to the vaporization heater 37 as it is. .

  A turbine power generation system using LNG gas in the case of the LNG fuel ship according to the present embodiment will be described with reference to FIG. The LNG gas vaporized and heated in the process of cooling and liquefying the working fluid through the tube wall in the condenser 21 or the LNG liquid passing through the LNG bypass valve 34a is vaporized by the seawater supply 38 in the vaporization heater 37, Further, the temperature is raised to room temperature and led to the superheater 39. As a heat medium for the superheat source supply 40 of the superheater 39, exhaust gas, scavenging air or cooling water is used. The high-pressure superheated gas is led to the LNG turbine 42 through the gas pressure regulating valve 41 to perform rotational work by the gas expansion stroke, and the coaxial generator 43 is rotated to extract the output as electric power. The LNG gas that has worked in the turbine is depressurized to a pressure necessary for the main engine, and is heated by the LNG heater 44 using steam or the like as needed, and is guided to the main engine 45.

  FIG. 4 illustrates the flow of LNG and brine when the cold heat of LNG according to the present invention is indirectly transferred to the working fluid via the brine. First, the LNG liquid or the LNG vapor 46 flows to the brine / LNG heat exchanger 47 where the latent heat and sensible heat of the LNG are transferred to the brine to cool the brine. The LNG main body is vaporized by receiving heat from the brine, and further heated to be led to a heater. The cooled low-temperature brine flows to the condenser 21 by the brine pump 48, cools and liquefies the working fluid in the condenser, and then returns to the original heat exchanger 47 for circulation. The function for preventing freezing of the working fluid in the condenser is the same as in the case of direct cooling by LNG.

The flow in the cycle of the working fluid according to the present invention and the effect in each device will be described with reference to FIG. FIG. 5 is a ph diagram quantitatively showing the relationship between the pressure p in the case of HFC-134a as an example of the working fluid and the enthalpy h as the horizontal axis. The flow in a closed circuit cycle of working fluid formed by the invention is illustrated for three cases. Each line has the specifications shown in the following table.
In the case of the solid line, the function of the working fluid is shown in the clockwise direction, starting with cooling and liquefaction by LNG first, then by pressurization by pump, further by vaporization and heating / overheating by seawater, exhaust gas, scavenging etc., and finally by turbine It becomes work and power generation, and finally power is taken out. The amount of thermal change and work in each process are represented by the amount of change in enthalpy in the same process.

FIG. 6 is a Ts diagram that quantitatively shows the relationship between the temperature T in the case of HFC-134a as an example of the working fluid and the entropy s as the horizontal axis. The flow in the working fluid cycle according to the invention is shown for two cases. FIG. 5 and FIG. 6 are the same except that the displayed physical quantity indicators are different. Which one to use depends on the designer's preference and practice. Each line in the figure has the specifications shown in the following table.

In the case of an LNG fuel ship, the high pressure LNG liquid generated by boosting the pump is used for cooling and condensing the binary working fluid, and then the turbine is driven as superheated gas by heating with exhaust gas, etc. A cycle example of an open circuit flowing toward the direction of methane gas is represented by a solid line on the ph diagram of methane gas. The following table shows the specifications for the case shown in this figure.

Represents the LNG fuel system of the current LNG fueled ship and LNG transport ship, both of which are not recovered from the cold heat of LNG, and LNG is flowed to the main engine as gas at normal temperature due to vaporization and heating by external high-temperature steam Indicates. The system of the binary power generation of a closed circuit using the cooling function by the cold heat recovery of LNG of the LNG transport ship by this embodiment is shown. A closed circuit binary power generation system using a cooling function by LNG cold recovery of an LNG fuel ship according to the present embodiment, and an open circuit Rankine cycle power generation system by the LNG itself after recovering the cold energy and fuel to the main engine Indicates supply. The flow of LNG and a brine in the case of transferring the cold heat of LNG by this embodiment to a working fluid indirectly through a brine is shown. As an example common to the LNG fuel ship and the LNG transport ship according to the present embodiment, changes in the pressure p and enthalpy h of the working fluid in three types of binary power generation cycles are shown on the ph diagram. As an example common to the LNG fuel ship and the LNG transport ship according to the present embodiment, changes in the temperature T and entropy s of the working fluid in two types of binary power generation cycles are shown on the Ts diagram. As an example of the power generation cycle by the Rankine cycle of the open circuit by the LNG main body of the LNG fuel ship by this embodiment, the change of the pressure p of LNG gas and the enthalpy h is shown on a ph diagram.

A: Fuel supply system of current LNG fuel ship B: Fuel supply system of current LNG transport ship 01: LNG tank 02: LNG liquid supply 03: LNG evaporator 04: Steam for heating 05: LNG heater 06: LNG room temperature gas 1: Working fluid liquid 2: Pump 3: High pressure working fluid 4: Regenerator 5: Vaporizer 6: Seawater supply 7: Heater 8: Seawater supply 9: Room temperature gas 10: Superheater 11: Heating source supply 12: Superheated gas 13: Gas pressure regulating valve 14: Turbine 15: Generator 16: Discharge gas 17: Seawater supply 18: Gas cooler 19: Normal temperature gas 20: Low temperature gas 21: Condenser 22: Heat insulation 23: Double structure 24: Working fluid Tank 25: Pressure regulator 26: Pressure regulation valve 27: Gas supply pipe 28: Liquid level regulator 29: Flow control valve 30: LNG tank 31a: LNG pump 31b: Compressor 32a: LNG supply pipe 32b: Gas supply pipe 33: Temperature regulator 34a: LNG bypass valve 34b: Gas bypass valve 34c: LNG liquid or LNG gas bypass valve 35: Gas heater 36: To main engine 37: Vaporization heater 38: Seawater supply 39: Superheater 40 : Superheat source supply 41: Gas pressure regulating valve 42: LNG turbine 43: Generator 44: LNG heater 45: To main engine 46: LNG liquid or LNG gas 47: Brine / LNG heat exchanger 48: Brine pump 49: Brine line

Claims (7)

  In a ship using liquefied natural gas (hereinafter referred to as LNG) as a fuel (hereinafter referred to as LNG fuel ship) or a ship transporting LNG as cargo (hereinafter referred to as LNG transport ship), a propulsion engine (hereinafter referred to as LNG) from an LNG tank. After cooling or liquefying the working fluid refrigerant gas (hereinafter referred to as working fluid) directly using LNG ultra-low temperature liquid or ultra-low temperature steam sent to the main engine) or indirectly through brine having a low freezing temperature The working fluid liquid is heated to a high temperature exhaust gas (hereinafter referred to as exhaust gas) from the main engine of the ship, high-temperature scavenging air (hereinafter referred to as scavenging) from the main engine, or high-temperature cooling water of the main engine. (Hereinafter referred to as “cooling water”) and the like, and the binary is generated by rotating the turbine with the gas of the high-temperature and high-pressure working fluid obtained by evaporation and further overheating. Power generation system.   The ultra-low temperature LNG after boosting the fuel LNG of the LNG fuel ship with a pump is directly used, or indirectly through a brine having a low freezing temperature, the discharge gas of the turbine of the binary power generation system is cooled and liquefied. The turbine is driven by a high-temperature and high-pressure LNG gas obtained by heating with exhaust gas, scavenging or cooling water, and at the same time, the working fluid cooled and liquefied by one binary power generation system is pressurized with a pump, and the working fluid A binary power generation system combined with a power generation system of LNG gas that generates power by rotating a turbine with a high-temperature and high-pressure working fluid gas obtained by evaporating the gas using exhaust gas, scavenging, or cooling water, and further overheating.   The condenser that liquefies the working fluid is strong enough to withstand the vacuum pressure generated during the cooling process, has a double-structured space, heat-insulates the outer surface of the inner tank, and separates it from the space consisting of the inner and outer tanks. This can occur due to the vacuum pressure in the condenser by being connected by a pressure tank with a working fluid liquid tank, a gas supply pipe, and a pressure control valve, and filled with refrigerant gas that is always maintained at a slight positive pressure from atmospheric pressure. 3. The binary power generation system according to claim 1, wherein the binary power generation system has a structure that prevents intrusion of air, which is a non-condensable gas, and sucks only the same working fluid gas in the event of leakage.   When the working fluid liquefied in the condenser and further cooled down is transferred to the evaporator by the liquid phase pump, NPSH (net positive) is used to ensure that the suction side pressure of the pump is more positive than the evaporation pressure of the working fluid. In order to ensure the (side suction pressure), the liquid level above a certain level is maintained or controlled, or the rotational speed of the pump is controlled by the liquid level. 3. The binary power generation system according to claim 1, wherein the pump is a submerged self-lubricating system (submerged type) installed in the condenser or in a working fluid liquid tank connected to the condenser.   When exhaust gas or scavenging gas is used as a high-temperature heat source, to prevent deterioration of heat transfer efficiency due to condensation or freezing of moisture contained in the exhaust gas or scavenging gas on the evaporator and superheater surfaces, and in the case of LNG transport vessels, condensed water droplets Keep the surface temperature of the evaporator and superheater below the dew point of the moisture to prevent corrosion of the evaporator and superheater by strong acid solution due to the dissolution of sulfur oxides contained in the exhaust gas LNG transport ship and LNG fuel ship working fluid liquid superheater, and LNG fuel ship LNG superheater upstream of seawater vaporizer and heater to provide working fluid gas and LNG vaporized gas The binary power generation system according to claim 1 or 2, wherein the temperature is raised to room temperature.   A temperature detection sensor for detecting the temperature of the working fluid inside the condenser is provided, and when the working fluid temperature drops below the freezing temperature, the working fluid is prevented from freezing by restricting the LNG flow rate with the LNG flow rate control valve. The binary power generation system according to claim 1 and claim 2.   When exhaust gas, scavenging and cooling water that are high-temperature sources are excessive, surplus high-temperature sources are used as heat sources, seawater is used as cooling sources, and surplus using working fluid such as chlorofluorocarbons that are compatible with both heat-source temperatures. 3. The binary power generation system according to claim 1, wherein the binary power generation system has an independent tandem type binary power generation system that effectively uses a heat source.

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