JPS5928725B2 - power plant - Google Patents

Description

[Detailed description of the invention] The present invention relates to power plants.

In particular, it is a plant that generates electricity by transferring heat from a heat source to a working medium and driving a turbine with the steam of the working medium, and is suitable for power generation that can be used to utilize medium-low temperature energy at a temperature level of 200 to 400 degrees Celsius. Regarding plants.

Conventional power generation plants using medium- and low-temperature energy include:
For a heat source with a temperature of 200°C or less, there is a method that uses a heat source to evaporate a low-boiling point medium such as fluorocarbons to generate electricity using a turbine.On the other hand, for a heat source with a temperature of 200 to 400°C, water,
There is a method in which heat is recovered in an intermediate heat medium such as oil, and the heat is used to evaporate fluorocarbons and the like to generate electricity through a turbine.

However, due to the heat resistance problem of the low boiling point medium, the former is
It is difficult to use for a heat source of 0° C. or higher, and it is unsuitable for a power generation plant that uses medium-low temperature energy.

On the other hand, in the latter case, the system becomes a double cycle of a working medium (such as fluorocarbons) and an intermediate heat medium (such as water or oil), which reduces the usable heat drop and reduces efficiency.

Furthermore, since the circulation flow rate of the intermediate heat medium is large, a large amount of internal power is required, and there is also the problem that the output at the power transmission end becomes small.

FIG. 1 shows a flow diagram of a conventional plant using the latter method, which is closest to the present invention.

This uses oil as the intermediate heat medium and fluorocarbon as the turbine working medium.

In this conventional example, waste heat fluid 1 is used as a heat source,
As a result, heat is transferred to the oil, which is an intermediate heat medium, flowing through the circulation system 5 in the oil heater 3.

In the figure, 4 is a pump that circulates this oil, and 2 is an outlet for the heat-exchanged waste heat fluid.

The heated oil (intermediate heat medium) gives heat to the fluorocarbon liquid in the fluorocarbon steam generator 6, and the fluorocarbon vapor 8 generated here
drives the turbine 9 to do work, which is converted into electrical energy by the generator 10.

The freon vapor expanded in the turbine 9 is sent to the condenser (condenser) 1
At step 5, it is cooled with cooling water 14 and liquefied to become a fluorocarbon liquid, which is supplied by a fluorocarbon pump 12 through a system 13, and is forced into the fluorocarbon steam generator 6 via a fluorocarbon liquid preheater T.

Note that 11 in the figure is a lubricating oil system.

However, as already outlined, some of these prior art techniques include:
This method has the following problems.

0) Intermediate cycles for intermediate heat carriers intervene, so
The heat drop becomes smaller, and it is necessary to make the heat exchanger (such as the Freon steam generator 6) thicker.

(b) Since it is a double cycle, in order to generate fluorocarbon vapor, not only the generator 6 but also an intermediate heat medium heater (oil heater 3, etc.) is required, and a double heat exchanger is required. Is required.

(c) The oil used as the intermediate heat medium must have a high flash point due to safety requirements in the event of a leakage accident, and therefore the unit price of the heat medium is high.

Since there is an upper limit to the heat resistance temperature of the intermediate heat medium, it is necessary to increase the circulation flow rate of the intermediate heat medium. The power of the pump 4) must be increased excessively, resulting in poor efficiency.

(e) The physical properties (vapor pressure, etc.) and properties as a heat medium of the intermediate heat medium and working medium are fixed depending on the type of substance used, and it is extremely difficult to adjust them arbitrarily.

An object of the present invention is to eliminate the need for a circulation cycle of an intermediate heat medium interposed between a heat source and a turbine working medium, thereby reducing the size of a power generation plant that uses medium-low temperature energy.

The present invention is characterized by a heat exchanger that exchanges heat from a heat source with a working medium (both consisting of a mixture of two types of substances) having different vapor pressures; A steam header equipped with a gas-liquid separator that separates the heated working medium into a mixture of gas and liquid phases, and the vapor-phase working medium vapor separated by the gas-liquid separator is guided to perform work. a turbine; a circulation system for supplying a liquid-phase working medium separated by the gas-liquid separation device to the heat exchanger; It consists of a circulation system or a supply system that supplies the steam to the steam tank.

With the above configuration, in the present invention, the mixture of two types of substances exchanges heat in the liquid phase, and the vaporized portion thereof becomes the turbine working medium, so that there is an intermediate between the heat source and the turbine working medium. Since there is no need for a heat medium to intervene (and the heat drop of the heat exchanger can be increased), the power generation plant can be made smaller.

In addition, according to the embodiment of the present invention, two types of substances with different vapor pressures are mixed to form the working medium, so if an appropriate substance is selected, physical properties such as vapor pressure can be arbitrarily determined depending on the mixing ratio. It is truly advantageous because it can be adjusted and its properties as a heat medium can be appropriately selected.

For example, in one embodiment of the present invention, a mixture of fluorocarbon and oil can be used as the working medium.

According to this embodiment, the mixture of oil and fluorocarbons has properties that are uniquely determined by the fluorocarbon concentration, temperature, and pressure in the mixture, and by appropriately controlling the fluorocarbon concentration, it can be used as an excellent heat transfer medium. Since it has been experimentally confirmed that the mixture can be made to have the following properties, the present invention can be preferably achieved by using this mixture as a heating medium.

The features of this embodiment are listed below.

■ Physical properties can be adjusted over a wide range at the same temperature.

That is, since the vapor pressure can be changed by changing the fluorocarbon concentration, the pressure can be adjusted appropriately within the operating temperature range.

(B) By controlling the fluorocarbon concentration, it can be used as a material with excellent properties as a heat medium.

(By lowering the O-fluorocarbon concentration, it can be provided with excellent properties as a lubricant, making it possible to abolish the lubricating oil system.

0 Excellent heat resistance and corrosion resistance.

In particular, when the mixture is heated, nonflammable chlorofluorocarbons evaporate, so the temperature of the mixture itself does not rise above its boiling point, and it can be handled as a nonflammable heat medium, which is advantageous for safety.

Hereinafter, an example of implementation of the present invention will be described with reference to the drawings.

This example uses a mixture of fluorocarbon and oil as the working medium.

For example, a mixture can be prepared using Freon R-113 as the Freon and polyol ester oil as the oil.

In this example, the liquid mixture is heated in the heat exchanger 3 using the high temperature waste heat fluid 1 as a heat source.

In the figure, 5 is a circulation system for the liquid portion of the mixture, and 4 is a circulation pump therefor.

The heated liquid mixture becomes a gas-liquid two-phase mixture,
It is sent to a gas-liquid separator 61.

Here, the gas phase steam, that is, the gas phase mixture, passes from the upper part of the steam ladder 71 through the steam system 8 to serve as a working fluid that drives the turbine 9, and the energy of the turbine 9 is converted into electrical energy by the generator 10. converted.

On the other hand, the liquid portion separated from the two-phase flow by the gas-liquid separator 61, that is, the liquid mixture, is recirculated from the lower part of the steam header 71, through the circulation system 5, to the heat exchanger 3 by the pump 4, and mixed. It constitutes the body's recirculation system.

On the other hand, the gaseous vapor of the mixture that has done work in the turbine 9 is cooled by cooling water 14 in the condenser 15 and liquefied, becoming a liquid mixture 11.

This liquid mixture 11 is pumped through a system 13 to a steam header 71 by a mixture supply pump 12 .

゛Here, in the header 71, the liquid phase part of the mixture separated from the gas phase and this condensed liquid mixture 11 are mixed and enter the circulation system 5 as a liquid mixture. be.

Note that the former, that is, the mixed liquid phase separated by the gas-liquid separator, has a low concentration of fluorocarbons due to its high temperature, but the latter, that is, the liquid mixture 11 liquefied in the condenser 15, has a high concentration of fluorocarbons. Therefore, by mixing the two in the header 71, the mass balance of the liquid mixture circulation system 5 can be achieved as a result.

In this embodiment, the thermofluidic properties of the mixture vary widely depending on the fluorocarbon concentration in the mixture, so various physical properties can be selected depending on the situation.

For example, when a mixture of Freon R-113 and polyol ester oil is used, the viscosity coefficient μ (Figure 3), vapor pressure P (Figure 4), and specific weight γ (Figure 4) depend on the Freon concentration. Figure 5), specific heat CP (Figure 6), thermal conductivity λ (Figure 7)
Figure) changes over a wide range, as is clear from the graphs in each figure.

Therefore, by arbitrarily adjusting the fluorocarbon concentration in the mixture, the above-mentioned viscosity coefficient μ, vapor pressure P, specific weight γ, and specific heat C can be adjusted.
p and thermal conductivity λ can be appropriately selected, and these various quantities can be changed appropriately according to the operating conditions of the plant.

This also makes it possible to increase the heat flow through the heat exchanger and reduce the recirculation flow rate.

Further, in the above configuration, since the heat exchanger 3 is configured as an evaporator of the mixture, the temperature change of the mixture as a heat medium is as shown in FIG. 8 or 9.

Figure 8 shows the case of a counter-current heat exchanger, and Figure 9 shows the case of a parallel-flow type heat exchanger. The temperature of the oil when is used is the temperature of the waste gas (waste heat fluid) which is the heat source.

As is clear from this graph, in this configuration, the temperature difference between the heat medium and the waste heat fluid is larger (therefore, the heat drop is larger) than when oil alone is used as the heat medium without phase change. It's advantageous.

In addition, with this configuration, the heat exchange performance is improved because the heat transfer accompanied by boiling is higher than the thermal conductivity of single-phase flow.

As a result, the heat exchanger can be made smaller and economically inexpensive.

Furthermore, since the temperature of the mixture of fluorocarbon and oil can only rise to a temperature close to the saturation temperature determined by the pressure of the steam header 11, the heat resistance of the mixture is limited by the use of oil alone. It's much less of a problem than it was.

Therefore, there is less risk of performance deterioration due to heat (therefore, the life of the heat medium can be significantly extended).

In addition, in the above configuration, in order to smooth out fluctuations in turbine output due to temperature fluctuations, it is sufficient to control the concentration of the mixture.

Therefore, smooth output control of waste heat can be easily realized.

Further, even when the mixture serving as the working medium is heated, the temperature of the mixture does not rise above its boiling point because the fluorocarbon evaporates at that time.

Moreover, since fluorocarbons are nonflammable, there is no flash point that would make them dangerous.

Therefore, it can be handled as a nonflammable heat medium, which is extremely advantageous in terms of safety.

FIG. 10 shows a modification of the above embodiment.

In the example shown in FIG. 2, the gaseous phase steam used to drive the turbine is condensed and liquefied and joins the separated liquid phase portion in the steam header T1. In this example, this confluence point is at the outlet of the pump 4 for circulating the liquid mixture.

The other configurations are the same as those in the example shown in FIG. 2, and are therefore designated by corresponding reference numerals.

According to this embodiment, the circulation force of the mixed medium can be increased by the pump 12, so there is an advantage that the power of the pump 4 can be reduced.

However, in this example, since the liquid high-temperature mixture and the low-temperature mixture come into contact with each other at the confluence point 41, there is a possibility that a transient two-phase flow will occur and the flow of this circulation system will become slightly unstable. be.

FIG. 11 shows another modification.

In this example, another heat exchanger 16 is provided to exchange heat between the liquid phase portion of the mixture separated here and the steam after being used to drive the turbine.

The heat exchange is configured to exchange heat between the liquid mixture at the inlet of the recirculation pump 4 and the steam at the outlet of the turbine 9.

According to this configuration, the steam after driving the turbine 9 is cooled in advance by the heat exchanger 16 and then enters the condenser 15.
The heat transfer area of the condenser 15 can be reduced, and plant efficiency can be increased.

Furthermore, since the NPSH required to prevent pump cavitation due to a decrease in the temperature of the inlet fluid of the recirculation pump 4 can be reduced, there is an effect that the degree of freedom in equipment arrangement is increased.

(However, in this example, the problem of price increase due to the addition of the heat exchanger 16 naturally arises).

Both FIG. 12 and FIG. 13 are modified examples in which the heat exchanger 3, ie, the evaporator for the mixture, is of a natural circulation type.

FIG. 12 shows a case in which waste heat fluid (waste gas) 1 serving as a heat source is flowed outside the heat transfer tube, and FIG. 13 shows a case in which waste heat fluid 1 is flowed into the heat transfer tube.

According to the embodiment shown in FIGS. 12 and 13, since the pump 4 can be made unnecessary, the internal power can be reduced, and there is an advantage that the efficiency is improved accordingly.

In the figure, 81 is the gas phase vapor of the mixture, and 51 is the liquid mixture.

As detailed above, since the present invention uses a mixture of two types of substances with different vapor pressures as the working medium, heat exchange with the heating source is done in one step of heating the mixture.
Therefore, although it can be used for general purpose use of medium and low temperature energy for heat sources of 200℃ to 400℃, it is a compact power generation plant because it does not require a circulation cycle of an intermediate heat medium between the heat source and the turbine working medium. This has the effect that it can be realized.

Further, the following effects can be mentioned as effects of the embodiments of the present invention.

That is, since the working medium is a mixture, its physical properties and properties as a heat medium can be arbitrarily adjusted by adjusting the mixing ratio, and it is extremely advantageous because it can be adjusted to the plant operating conditions or the operating conditions can be changed.

Although each of the embodiments described above has a number of effects and advantages depending on its specific configuration, the present invention is not limited only to these embodiments.

[Brief explanation of drawings]

FIG. 1 is a conventional route map. FIG. 2 is a flow diagram showing an example of implementation of the present invention. Figures 3 to 7 are graphs showing the relationship between fluorocarbon concentration and physical property values of an example of a mixture that can be used in the same example, and show the relationship between the winter wilt coefficient, vapor pressure, specific weight, specific heat, and thermal conductivity. This shows CFC concentration dependence. FIGS. 8 and 9 are graphs showing temperature distributions when the same mixture is used in a countercurrent heat exchanger and a cocurrent heat exchanger, respectively. 10 and 11 are flow diagrams of modifications of the above example, respectively. FIG. 12 and FIG. 13 are diagrams showing modified examples of the heat exchanger. 1... Heat source (waste heat fluid), 3... Heat exchanger, 61.
- Gas-liquid separator (gas-liquid separator), 9...turbine.

Claims (1)

[Claims] 1. A heat exchanger that exchanges heat from a heat source with a working medium consisting of a mixture of two substances having different vapor pressures, and a working medium heated by the heat exchanger. a steam header equipped with a gas-liquid separator that separates the mixture into a gas phase and a liquid phase;
a turbine that conducts work by guiding the gas-phase working medium vapor separated by the gas-liquid separator; a circulation system that supplies the liquid-phase working medium separated by the gas-liquid separator to the heat exchanger;
A power generation plant comprising a supply system for supplying a working medium that has been worked by the turbine and condensed in the condenser to a circulation system of the heat exchanger or a lag to the steam. 2. The power generation plant according to claim 1, wherein the working medium is a mixture of fluorocarbon and oil.