JPS6035105A - Lng based generating equipment by rankine cycle - Google Patents

Abstract

PURPOSE:To obtain supply of refrigerant with high density of lubricating oil to an oil separator by installing a weir in a Rankine-Cycle-type refrigerant operator and introducing a part of the regrigerant, which flows over the weir because of its raised boiling foam level due to lubricating oil density exceeding the predetermined density. CONSTITUTION:Through a conduit 18, LNG is sent to a LNG vaporizer 4, in which it is evaporated by condensation heat of refrigerant like fleon from a conduit 13. Further, it is sent to a NG heater 5, in which it is heated by sea water to become natural gas at 0 deg.C or higher temperature and delivered to consumers. Refrigerant that has been condensed in the vaporizer 4 is supplied to a refrigerant evaporator 1 by a pump 6 and heated by sea water from a conduit 21. And the gas generated thereby is sent to a turbine 7 through a conduit 12 in order to have the gas do work in the turbine 7 to drive a generator 8. And a refrigerant evaporator 1 containing a weir 3 installed therein sends refrigerant with high density of lubricating oil to an oil separator 9, taking advantage of a rise of a boiling boundary surface in the evaporator 1, which takes places because of mixing of lubricating oil into the refrigerant.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a Rankine cycle system that uses a fluorocarbon-based cycle medium to generate electricity by recovering cold heat when liquefied natural gas (LNG) is vaporized as power through the Rankine cycle. [Background of the Invention] This invention relates to cold power generation equipment, and in particular to equipment configuration for obtaining stable long-term continuous operation of a Rankine cycle medium turbine. It is known that Rankine cycle type LNG cryogenic power generation equipment is suitable for generating electricity. As this Rankine cycle medium,
For example, in such equipment where fluorocarbon-based media such as Freon R-22 and Freon R-13B1 are used and circulated in a closed cycle, it is necessary to prevent the medium gas from leaking into the atmosphere from the shaft seal of the medium turbine. To prevent this, a shaft seal mechanism such as an oil film seal or a mechanical seal is adopted for the shaft seal part, but as the operation continues, the shaft seal part of the media turbine is replaced by a mechanical seal or a shaft seal mechanism such as a mechanical seal.
) The lubricating oil used in the engine normally leaks into the Rankine cycle system, albeit in small amounts. Furthermore, due to problems such as damage to the shaft seal, a large amount of lubricating oil may temporarily enter the Rankine cycle system. Most of the lubricating oil leaked into the system accumulates in the medium evaporator because its boiling point is higher than that of the Rankine medium. That is, as shown in FIG. 1, the height of the foam increases almost in proportion to the amount of oil introduced. For this reason, when the concentration of lubricating oil becomes high, the height of the boiling surface foam exceeds the demister of the medium evaporator, causing mist to scatter, and the amount of liquid medium entrained in the steam medium flowing into the medium turbine increases. Vibrations and abnormal noises occur in the media turbine, making it impossible to continue operation, which not only poses problems in terms of reliability, but in the past, when such a situation occurs, Rankine media It was known that operation could be continued by replacing the Rankine media, but this was economically inconvenient because Rankine media are expensive and replacing them requires a large amount of money.

[Purpose of the invention]

An object of the present invention is to prevent an increase in the height of boiling surface foam due to lubricating oil contamination, and to enable continuous supply of a medium liquid with a high lubricating oil concentration to an oil separator.

[Summary of the invention]

The present invention uses liquefied natural gas (T,
In a Rankine cycle LNG cryothermal power generation facility that generates electricity using the cold heat generated during vaporization of N G ), an oil separator is installed in parallel to continuously remove lubricating oil that has leaked from the medium turbine and mixed into the Rankine medium. Or, by using a method of intermittently separating and discharging the oil to keep the oil content in the medium evaporator below the value allowed by the equipment, and installing a weir inside the medium evaporator, the lubricating oil was mixed into the cycle medium. The system is characterized in that the Rankine medium with high lubricating oil concentration is supplied to the oil separator to separate the oil by utilizing the rise of the boiling interface within the medium evaporator that occurs in the medium evaporator.

[Embodiments of the invention]

An embodiment according to the present invention will be explained with reference to FIG.

The LNG enters the T,NG evaporator 4 through conduit 18, where the LNG enters the T,NG evaporator 4 from conduit 13, e.g.
After being evaporated by the heat of condensation, it enters the NG heater 5 through the conduit 19, becomes natural gas at 0° C. or higher with seawater from the conduit, and is supplied as fuel gas from the conduit. On the other hand, in the Rankine cycle system, LNGg generator 4
Freon R-13B1 (hereinafter abbreviated as Freon) is condensed at near atmospheric pressure by the cold energy of N G, and the liquid at around -60°C is pressurized to a predetermined pressure by the Freon pump 6 from the conduit 17, and then the conduit 11 is supplied to the medium evaporator 1 from In the medium evaporator 1, the seawater from the conduit 21 heats the fluorocarbon to about 8°C. This gas is in conduit 1
2 enters the freon turbine 7, where it expands to almost atmospheric pressure, and the energy at the time of expansion is recovered as electric power by the generator 8. The fluorocarbon gas at near atmospheric pressure that exits the fluorocarbon turbine 7 is expanded and its temperature drops to about -60° C., enters the LNG evaporator 4 through the conduit 13, and is circulated.

In this embodiment, lubricating oil is used in the front turbine 7 for mechanical seals and bearings, but it is structurally difficult to reduce the amount of lubricating oil leaking into the Rankine cycle to zero. Have difficulty. The leaked lubricating oil flows into the conduit 13 and flows into the T, NG evaporator 4. It flows into the medium evaporator 1 through the freon pump 6 together with the freon. Freon is evaporated by the heat of the seawater in the medium evaporator 1, but only the fluorocarbon, which has a lower boiling point than the lubricating oil, is evaporated, and the lubricating oil leaked from the fluorocarbon turbine 7 into the Rankine cycle becomes the fluorocarbon liquid in the medium evaporator 1. The lubricating oil concentration in the Freon fluid gradually increases. When the lubricating oil concentration increases to a certain level or higher, there is a noticeable difference in the height of the boiling surface foam compared to when no lubricating oil is mixed in, regardless of the type of medium, and as shown in Figure 1, the lubricating oil amount increases. The foam height increases almost proportionally. When the height of the foam exceeds the demister 2, the fluorocarbon liquid along with the fluorocarbon gas enters the fluorocarbon turbine 7 through the conduit 12 in the form of a mist, colliding with the impeller of the fluorocarbon turbine 7 and causing erosion and vibration. , the front turbine 7 becomes unable to operate.

FIG. 1 shows that this phenomenon can be prevented by making the liquid level in the medium evaporator 1 lower than the height of the demister 2. Therefore, a weir 3 is created in the medium evaporator 1 so that when the lubricating oil reaches a certain concentration and the boiling surface foam height increases, it overflows over the weir 3. In this way, even if the height of the foam increases, it will only rise to the height of the weir 3 and will not exceed the demister 2, and no mist will be generated.

In addition, since lubricating oil has a lower specific gravity than CFC, the lubricating oil concentration on the boiling surface is higher than the lubricating oil concentration in the medium evaporator (it also has the effect of concentrating it). The fluorocarbon liquid is continuously sent to the oil separator 9, the fluorocarbon is evaporated by a heating source from the conduit n, and the remaining lubricating oil is extracted from the valve 31.According to this embodiment, a weir 3 is installed in the medium evaporator 1. By providing this, it is possible to constantly keep the liquid level constant and to continuously supply Freon liquid with a high lubricating oil concentration to the oil separator.

〔Effect of the invention〕

According to the invention, by creating a weir in the medium evaporator,
By monitoring the rise in boiling surface foam height due to lubricating oil contamination, it is possible to prevent such an increase.Furthermore, it is possible to continuously supply a medium liquid with high lubricant concentration to the oil separator, thereby improving the oil separator's performance. It has the effect of reducing the load.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the characteristic that the boiling liquid direction increases due to the mixing of turbine lubricating oil at the time of boiling when turbine oil is mixed in a fluorocarbon-based Rankine medium. It is a system diagram showing one example of cold power generation equipment. 1...Medium evaporator, 2...Demister
53...Weir, 4...LNG evaporator, 5...NG heater, 6...Freon pump, 7... Front turbine, 8... Generator, 9... Oil separator, 31... Valve, 11
~24... Conduit・8

Claims (1)

[Claims] 1. The Rankine cycle is used to generate electricity using the cold heat generated during the vaporization of liquefied natural gas, and an oil separator is installed in parallel to continuously or intermittently separate lubricating oil mixed into the cycle medium. This problem occurred because lubricating oil got mixed into the cycle medium when a weir was installed in the medium evaporator in LNG cryogenic power generation equipment, which was designed to maintain the oil content in the medium evaporator below the allowable value for the equipment. A Rankine cycle type LNG cryothermal power generation facility characterized in that a fluorocarbon-based medium having a high lubricating oil content is supplied to an oil separator by utilizing the rise of a boiling interface in a medium evaporator.