JPS602487B2 - Low boiling point medium turbine plant - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a plant that generates electricity by transferring heat from a heat source to a low-boiling point medium and driving a turbine with the steam of the medium, wherein the temperature level of the heat source is The present invention relates to a power generation plant that can be suitably used to utilize relatively low energy sources.

[Background of the invention]

Conventional power plants using low-quality energy of this kind include a method of generating electricity using a turbine using a low-boiling point medium with a high heat source recovery rate.

Since this method uses a medium with a low boiling point, it has better heat energy recovery efficiency from the heat source than when using a conventional thermal power working medium such as water. In comparison, using a low boiling point medium has the advantage of being able to obtain more power output. However, if the temperature of the heat source is high, thermal decomposition of the medium may occur and highly corrosive decomposition products may be produced, so there is a temperature limit in which the heat medium can be used. In general, power generation efficiency increases as the heat medium steam temperature increases and as the turbine outlet condensate temperature decreases. As a conventional method for improving the heat resistance of a heat medium, there is a method using a mixed fluid of a front, which is a type of low boiling point medium, and oil having a low vapor pressure. Figure 1 shows a system diagram of this method. In this conventional example, a waste heat fluid 1 is used as a heat source, and heat is thereby transferred to a mixture of oil and fluorocarbons in an oil-fluorocarbon evaporator 2, and a portion of the fluorocarbons in the mixture is evaporated. It becomes a boiling two-phase flow, and in the gas-liquid separation drum 4, it becomes steam mainly composed of fluorocarbon steam, which flows through the fluorocarbon steam line 7 into the turbine 8, which drives the turbine 8 and rotates the generator 9. to obtain electricity.

The steam that has done work in the turbine 8 is cooled by cooling water 11 in a fluorocarbon condenser 10, becomes a fluorocarbon liquid 6, and is sent into a fluorocarbon preheater 3 by a fluorocarbon pump 12.
After the enthalpy of the fluorocarbon liquid increases by recovering heat on the low-temperature side of the waste heat, it is fed into the gas-liquid separation drum 4 and mixed into the oil-fluorocarbon mixture in the oil-fluorocarbon recirculation system 5. In the above conventional example, the heat resistance of the medium in the part where heat is exchanged with the high-temperature waste heat source is excellent, so the thermal decomposition of the fluorocarbon is suppressed, and the heat capacity of the oil-fluorocarbon mixture is larger than that of the fluorocarbon alone. Although it has advantages such as load characteristics that are resistant to fluctuations in waste heat, the power generation efficiency is equivalent to the conventional Rankine cycle using only fluorocarbons, so it is necessary to improve the efficiency.

Furthermore, it is necessary to suppress the thermal decomposition of fluorocarbons alone in the fluorocarbon preheater 3. It is an object of the present invention to provide a low boiling point medium turbine plant suitable for reducing the thermal decomposition rate and effectively utilizing heat sources such as medium and low temperature waste heat.

[Summary of the invention]

The present invention is characterized in that a mixture of a certain type of low-boiling point medium and oil has better heat resistance and heat transport properties than the low-boiling point medium alone, and that the vapor pressure of the mixture is lower than that of the low-boiling point medium. It was confirmed through experiments that the vapor pressure was lower than that of the mixture alone, and a vaporized low-boiling medium obtained by heating this mixture was introduced into the turbine as a working medium. Supplying the mixed liquid with a low concentration of a low boiling point medium used as a heating medium of a heat exchanger for preheating the liquid to reduce the pressure inside the condenser,
This aims to increase the turbine output and suppress the thermal decomposition of the low boiling point medium.

[Embodiments of the invention]

A fluorocarbon turbine plant that is an embodiment of the present invention will be described with reference to the drawings.

Here, a mixture of fluorocarbon and oil is used as the circulating fluid in the plant. For example, Freon R-11 as Freon
3. The mixture can be prepared using polyolester oil as the oil. In FIG. 2, an oil-fluorocarbon mixture is heated in an oil-fluorocarbon evaporator 2 using a high-temperature waste heat fluid 1 as a heat source, and the oil-fluorocarbon mixture is transferred to a gas-liquid separation drum 4 in a gas-liquid two-phase flow due to boiling of the freon. After gas-liquid separation in the drum 4, the fluid whose main component is fluorocarbon vapor flows through the fluorocarbon vapor line 7 to the turbine 8, and the oil-fluorocarbon mixture with a high oil concentration is converted into oil-fluorocarbon. It descends in the recirculation system 5 and enters the evaporator 2 from below, forming a natural circulation flow that rises in the evaporator 2.

The fluorocarbon vapor that has flowed into the turbine 8 rotates the turbine 8 to perform work, and then flows into the fluorocarbon condenser 10 . On the other hand, a part of the oil-fluorocarbon mixture is extracted from the gas-liquid separation drum 4 through the oil-fluorocarbon extraction line 21, and the pressure reducing valve 2
2, some of the fluorocarbons flash from the oil-fluorocarbon liquid and become steam.The steam is separated into gas and liquid in the flash tank 13, and the steam passes through the low-pressure fluorocarbon steam line 29 to the low-pressure stage of the turbine 8. flow into and do work. The oil-fluorocarbon mixture separated into gas and liquid in the flash tank 13 passes through the oil-fluorocarbon mixing line 14 and is cooled in the regenerative heat exchanger 15, and then cooled in the cooler 16 to a temperature effective for absorbing the fluorocarbon vapor. The cooled fluorocarbon flows into the fluorocarbon condenser 0, where it is atomized by the spray nozzle 17 to increase the surface area of contact with the fluorocarbon vapor and effectively absorb the fluorocarbon vapor. Freon condenser 01
It is cooled by cooling water 11, and the pressure is the saturated vapor pressure of the oil-fluorocarbon mixture. The pressure of the oil-fluorocarbon mixture 18 mixed in the freon condenser 0 is increased by the pump 12, and part of it is heated in the regenerative heat exchanger 15 through the line 23 and sent into the recirculation system 5 of the oil-fluorocarbon evaporator 2. A part of it is sent under pressure into the fluorocarbon subheater 3 through the line 24 to recover waste heat, and then sent into the gas-liquid separation drum 4 again where it exchanges heat with the high temperature oil and fluorocarbons and becomes steam. It flows into the turbine 8 through the , and is designed to do work.

According to the above-mentioned front turbine power generation plant, the following effects are produced. That is, in general, the conversion of thermal energy into electrical energy in a Rankine suncle is based on the following equation.
P=rimG.

-il). GfGfkoQ/(jo-i3) Here, P is the generating end output, and m is the reciprocal of the ratio between the ideal mechanical power obtained by isentropic expansion and the actual power considering various losses. Gf is the flow rate of the working medium that rotates the turbine, Q is the amount of heat recovered from waste heat, io is the enthalpy of the working medium at the turbine front pressure, i, is the enthalpy of the working medium on the isentropic line at the turbine exhaust pressure, and i3 is the enthalpy of the working medium on the isentropic line at the turbine exhaust pressure. This is the enthalpy of the oil-fluorocarbon mixture at the temperature of the fluorocarbon condenser liquid.

From this formula, i. It can be seen that the smaller the , and therefore the lower the turbine exhaust pressure, the larger the power generation end output can be obtained.

Figure 3 shows this in a diagram, with the enthalpy of the working medium (in this example, fluorocarbon alone) on the mechanical axis, and the pressure on the vertical axis. The work obtained by adiabatic expansion in the turbine from the turbine front pressure Po is △h when the turbine exhaust side pressure is P, and △h2 when the exhaust side pressure is P2, P, >P2, △h, △h2, and the thermal drop is large. However, the vapor pressure of the oil-fluorocarbon mixture exhibits the characteristics shown in FIG. In the figure, the axis is the temperature, and the vertical axis is the saturated vapor pressure at that temperature. Fourth
From the figure, it can be seen that the vapor pressure of the carbon-fluorocarbon mixture D is lower than that of the single fluorocarbon 1 at the same temperature. In the conventional system shown in FIG.
, the system leading to the pump 12 and the subheater 3 circulates a mixture with a very high concentration of fluorocarbons, which is essentially the same as fluorocarbons alone, so if the concentration in the condenser 10 is T, then The pressure inside the capacitor 10 is P, (see Fig. 4), whereas in the system shown in Fig. 2, the pressure inside the capacitor 1 is P, (see Fig. 4).
Since a mixed liquid with a very high concentration of oil is supplied within 0,
Even if the pressure inside the condenser 0 is the same temperature T as described above, it becomes P2, which is lower than P, so the output of the turbine 8 can be increased by the lowered amount. If the temperature of the oil that is fed to the condenser 101 through the mixing line 14 is high, the temperature inside the condenser 10 will eventually become high and a large amount of cooling water 11 will be consumed. A regenerative heat exchanger 15 is installed to perform heat exchange between the oil flowing through the mixing line 14 and the mixed liquid sent to the evaporator 2 by the freon pump 12, and the temperature of the oil supplied to the condenser 101 is This reduces the amount of heat wasted outside the system by recovering heat to the mixed liquid.

When the oil temperature cannot be lowered sufficiently by the regenerative heat exchanger 15 alone, as shown in FIG. be able to. In order to improve the absorption efficiency of fluorocarbons in the condenser 10, it is desirable to reduce the amount of fluorocarbons mixed in the liquid sent to the condenser via the mixing line 14. It is effective to provide a flash tank 13 at

Since the mixed liquid is flashed in the flash tank 13, fluorocarbons having a low saturated vapor pressure are evaporated and separated there. The separated fluorocarbon vapor flows into the low pressure stage of the turbine 8 via the low pressure fluorocarbon vapor line 29 . therefore,
The energy of the fluorocarbon vapor separated in the flash tank 13 is also effectively recovered. Furthermore, since an oil-fluorocarbon mixture is used as the heat medium in waste heat recovery heat exchangers such as the evaporator 2 and the subheater 3, instead of the conventional single fluorocarbon, the heat resistance of the fluorocarbon is improved and the oil ratio is reduced. Bigger than Freon,
Because of these properties, good heat recovery can be performed.

In addition, the conventional Freon pump 12 uses NPS to prevent cavitation on the absorption side due to the high vapor pressure of Freon.
Although it was necessary to increase H (net suction head), according to this embodiment, since the vapor pressure is low, NPSH may be small, and there is an advantage that there are fewer restrictions on equipment arrangement. Fifth
The figure shows another embodiment of the present invention, in which a regenerative heat exchanger 15 and a pressure reducing valve 22 are connected to the oil-fluorocarbon mixing line 14.
It has been established.

Although this embodiment has the advantage of simplifying the system compared to the embodiment shown in FIG. 2, it is difficult to optimize the temperature of the oil supplied to the condenser 10 via the mixing line 14, making it less efficient. Although the improvement effect is inferior to that shown in FIG. 2, the efficiency is improved since the pressure inside the capacitor 10 can be lowered compared to the conventional example shown in FIG.

〔Effect of the invention〕

According to the present invention, it is possible to realize a low boiling point medium turbine plant that reduces the thermal decomposition rate of the low boiling point medium and improves the efficiency of the turbine plant.

[Brief explanation of drawings]

Figure 1 is a system diagram of a conventional low boiling point medium turbine system.
Fig. 2 is a system diagram of a low boiling point medium turbine system which is an embodiment of the present invention, and Fig. 3 is a system diagram of a low boiling point medium turbine system which is an embodiment of the present invention.
FIG. 4 is an enthalpy diagram, FIG. 4 is a vapor pressure diagram of fluorocarbons and an oil-fluorocarbon mixture, and FIG. 5 is a system diagram of a low boiling point medium turbine system according to another embodiment of the present invention. 1... Waste heat fluid, 2... Oil-Freon evaporator, 4... Gas-liquid separation drum, 8... Turbine, ID... Freon condenser, 11... Oil-Freon mixing line, 13... Flash Tank, 15... Regenerative heat exchanger, 18...
Oil-1 CFC mixture. Younger brother l figure 2 country figure 3 figure 4 cause of effort

Claims (1)

[Scope of Claims] 1. An evaporator that vaporizes a heat medium by exchanging heat with a heat source, a gas-liquid separation drum that separates the heat medium heated by the evaporator into vapor and liquid; A turbine plant comprising: a turbine driven by steam that has passed through the turbine; a condenser that condenses the steam that has passed through the turbine; and a pump that supplies the heat medium condensed in the condenser to the evaporator. The medium and the low-boiling point medium are a mixture of substances with different vapor pressures, and the low-boiling point medium is introduced into the turbine and is condensed through the condenser. A regenerative heat exchanger for heating the medium liquid is installed, and the mixed liquid having a low concentration of the low boiling point medium in the gas-liquid separation drum is drawn out from the gas-liquid separation drum and used as a heat source for the regenerative heat exchanger. . A low boiling point medium turbine plant, wherein the mixed liquid after being used as a heat source for the regenerative heat exchanger is introduced into the condenser. 2. A flash tank is installed in a path leading the mixed liquid from the gas-liquid separation tank to the regenerative heat exchanger, and the low boiling point medium evaporated in the flash tank is introduced into the turbine. A low boiling point medium turbine plant according to scope 1. 3. The low boiling point medium turbine plant according to claim 1 or 2, wherein a mixed fluid of fluorocarbon and oil is used as the mixture.