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THERMOELECTRIC SOURCES OF CURRENT
INVENTION
Patent of the Russian Federation RU2117884

METHOD AND DEVICE FOR PRODUCING ELECTRICITY BY USING LOW-POTENTIAL HEAT-SUPPLYERS

METHOD AND DEVICE FOR PRODUCING ELECTRICITY BY USING LOW-POTENTIAL HEAT-SUPPLYERS

The name of the inventor: Samhan Igor Isaakovich
The name of the patent holder: Samhan Igor Isaakovich
Address for correspondence:
Date of commencement of the patent: 1995.06.14

The method and apparatus for generating electricity can be used in power engineering. In a method including a direct energy cycle in which the liquid working medium is compressed, then heated and evaporated, the resulting vapors are expanded in a turbine with power generation and condensed, and the reverse energy cycle in which the coolant is compressed in the compressor is cooled with heat transfer to the working fluid and Expansion in the expander, condensation of the working fluid is carried out at a temperature below ambient temperature, the temperature of the refrigerant before compression in the compressor is lowered below ambient temperature, the coolant in the expander is cooled to a temperature below the condensation temperature of the working fluid and fed to a condenser for heat removal, and heating and evaporation Working fluid in front of the turbine is carried out using a low-potential heat carrier. In the device including a steam-powered circuit with a series-connected pump, heater, turbo-generator and condenser, and a heat pump with an expander and a compressor connected to the heater, the steam-powered circuit after the heater is equipped with a heat exchanger for cooling the coolant included in the heat pump circuit in front of the compressor, the expander is connected to Condenser, and the steam-cycle loop before the turbine has an additional heater connected to an external source of thermal energy. The invention provides an increase in the efficiency of converting the energy of low-potential thermal sources into electrical energy, reducing fuel consumption and flue gas emissions into the environment.

DESCRIPTION OF THE INVENTION

The invention relates to power engineering, in particular, to the conversion of low-potential thermal energy into electrical energy.

A method for producing electric energy using a low-potential heat carrier (1), for example, exhaust gases of a heat engine, is known. In this method, the working medium - precompressed natural gas coming from the gas main - is heated by a low-potential heat source (heat carrier) to a temperature of 50-90 ° C, then expanded in a turbine with electricity generation. After the turbine, the working fluid is discharged at a temperature from 0 ° C to -10 ° C. In this method, 450 kcal (0.523 kWh) of thermal energy is expended for 1 kW-h of energy received.

The disadvantage of the method is the need for a gas main high pressure.

The method closest to the invention according to the technical essence (2) is known.

The method includes a direct energy cycle in which the liquid working medium is compressed, then heated and evaporated to produce heat from the heat source, the resulting vapor is expanded in the turbine to generate electricity and condensed after the turbine to transfer the heat of condensation to the heat receiver and a reverse energy cycle in which the refrigerant Compressed in a compressor, cooled after the compressor in a heat exchanger and fed to an expander, followed by expansion. In this method, air is used as the refrigerant, which is introduced into the compressor at ambient temperature, expansion of the air in the expander is carried out to a temperature close to the ambient temperature, after the expander, air is discharged to the atmosphere (the environment). As a heat source, the heat of compressed air in the compressor is used, the compressor is driven by a heat engine consuming organic fuel. Condensation of the vapors of the working fluid (low-boiling liquid) is carried out at ambient temperature.

The drawback of the method is the comparatively high costs of organic fuels and the pollution of the environment by flue gases. An apparatus for producing electric power is known which is closest in technical essence to the invention (2), including a forward-cycle steam cycle circuit for circulating a working fluid in which a pump, heater, turbo-generator and condenser are connected in series, and a circuit of a reverse cycle (heat pump) for circulating refrigerant , In which there is a compressor and an expander connected to each other through a heater. In this method, the reverse cycle is open, the pipelines for introducing air into the compressor and exiting the expander communicate with the atmosphere.

The device works as follows. The refrigerant (which uses air), which has an ambient temperature, is compressed in the compressor, while its temperature increases significantly, in the heater, the heated refrigerant gives away some of its thermal energy of the light-boiling liquid of the steam-powered circuit. Then the compressed refrigerant enters the expander, where it expands to perform an external job and is cooled to ambient temperature. Due to the operation of the expander, the energy consumption in the compressor is largely covered.

The disadvantage of this device is the insufficient efficiency of conversion of thermal energy into electrical energy and pollution of the environment.

The purpose of the present invention is to increase the efficiency of converting the energy of low-potential heat sources into electrical energy, reducing fuel consumption and flue gas emissions into the environment.

This goal is achieved in that in a known method of generating electric power, including a direct energy cycle in which the liquid working medium is compressed, then heated and evaporated, the resulting vapors are expanded in the turbine to generate electricity and condense after the turbine, and a reverse energy cycle in which the refrigerant Compressed in the compressor, cooled after the compressor with heat transfer to the working fluid and expansion in the expander to obtain external work, condensation of the working medium is carried out at a temperature lower than ambient temperature, the temperature of the refrigerant before compression in the compressor is reduced below ambient temperature by recuperative heat exchange, refrigerant in the expander Cooled to a temperature below the condensation temperature of the working fluid and fed to a condenser where it is used as a heat sink and the working fluid in front of the turbine is further heated using a low-potential heat source.

Another difference is that the heat source is a coolant-a liquid or a gas with a temperature of 50-150 ° C.

In addition, the refrigerant leaving the compressor is further cooled by a coolant exiting the condenser.

Another difference is that the compression and expansion of the refrigerant is carried out in several stages.

Another difference is the additional increase in the refrigerant pressure after the expander with the help of an additional compressor.

There are also other differences, consisting in the fact that cooling of the refrigerant before the compressor is carried out by the working body of the direct cycle;

Cooling of the refrigerant before the compressor is additionally carried out by the refrigerant leaving the condenser;

Cooling of the refrigerant before the compressor is carried out to the condensation temperature of the working fluid;

Condensation of the vapors of the working substance is carried out at a temperature of 70 - 120 K;

As a working fluid, light hydrocarbons containing 2 to 4 carbon atoms in the molecule and having a critical temperature above the ambient temperature are used;

The working medium after the condenser is compressed to pressures 2-4 times higher than the critical pressure;

Before evaporation the working medium is throttled, reducing its pressure;

Air is used as a coolant.

In an apparatus for generating electric power including a forward cycle loop for circulating a working fluid in which a pump, heater, turbine with an electric generator and a capacitor are connected in series, and a reverse cycle circuit for circulating the refrigerant in which the compressor is connected to the expander through a heater, a forward cycle loop after The heater is additionally equipped with a heat exchanger for cooling the refrigerant, included in the reverse cycle circuit before the compressor, the expander is connected to the condenser, and the forward cycle circuit in front of the turbine has an additional heater connected to an external source of thermal energy.

Another difference of the device is that the reverse cycle loop contains an additional compressor communicating with the condenser and the heat exchanger for cooling the refrigerant.

Another difference of the device is that an intermediate heat exchanger is connected in the loop loop, connected to the compressor and expander on one side, and to the condenser and an additional compressor on the other.

A further difference is that the return circuit is provided with a regenerative heat exchanger communicating on one side with a heat exchanger for cooling the refrigerant and a compressor, and on the other with an intermediate heat exchanger and an additional compressor.

In addition, the distinguishing feature of the device is that the expander contains several stages connected to the capacitor.

Another difference of the device is that the loop of the forward cycle before the additional heater contains a choke.

The conditions of interaction of the forward and reverse cycles proposed in this method are essential for achieving the objectives of the invention. In particular, as a direct cycle it is expedient to use the Rankine steam-cycle, approaching in efficiency to the Carnot cycle. At the same time, a decrease in the condensation temperature to values ​​of 70-120 K significantly improves the thermodynamic efficiency. A direct cycle in comparison with traditional steam power plants with a condensation temperature of about 300 K.

For a heat pump that removes the heat of condensation, the proposed method uses an inverse triangular Lorentz cycle with a constant temperature of the heat source (working medium in the condenser) and a variable temperature of the heat receiver (the working medium compressed by the pump after the condenser). Thermodynamic efficiency. The triangular Lorentz cycle in the temperature range 100-300 K is almost three times higher than the efficiency An ideal Carnot cycle [3, 4]. As the temperature range increases, this ratio increases to 10 or more times / 3 /.

To carry out a reverse cycle with minimal energy losses (i.e., to reduce the external and internal irreversibility of the actual cycle), the proposed method provides for a number of operations, including: 1 - cooling the refrigerant before compression in the compressor; 2 - application for cooling the refrigerant of the reverse cycle of the working body of the direct cycle; 3 - cooling of the refrigerant before and after compression in the compressor to the temperatures of the working fluid; 4 - increase of the refrigerant pressure in the condenser with the use of an additional compressor increasing the pressure difference in the expander and matching the temperatures of the working fluid and refrigerant; 5 - multistage compression and expansion of the refrigerant.

The energy efficiency of the proposed method and device can be relatively high, and the generation of electricity in the forward cycle can significantly exceed the energy costs in the reverse cycle. This is facilitated by the choice of a working fluid with a relatively high critical temperature and an increase in the degree of compression of the working fluid in the pump. These factors allow many times to increase the heat capacity of the working fluid after the condenser and, consequently, to lower the refrigerant temperatures in the reverse cycle of Lorentz, which determine its cooling coefficient. In particular, for a liquid propane (C 3 H 8 ) having a critical pressure P cr = 4.21 MPa, the critical temperature T cr = 369.9 K, the evaporation heat Q to 480 kJ / kg at T 100-150 K , The average heat capacity at constant pressure C p in the temperature range 100-200 K at a pressure of P / P cr 3 is according to / 5 / 6.7 kJ / kg · K.

The amount of heat that can be transferred to the working propane in this temperature range (100 K) is Q 1 = C p · T = 6.7 kJ / (kg · K) · 100K = 670 kJ / kg. .

The cooling coefficient of the triangular Lorentz cycle for this temperature range T 1 = 100 K and T 2 = 200 K can be calculated as / 3, 4 /.



The work consumed in the reverse cycle, taking into account even a low efficiency. A real process = 0.7, can be estimated by the value of A equal to A = Q k / ( G · ) = 480 / (3,259 · 0,7) = 210 kJ / kg. .

In this case, the amount of heat Q 2 transferred by the heat pump (reverse cycle) to the working fluid is Q 2 = Q k + A = 480 + 210 = 690 kJ / kg, practically equal to the value Q 1 necessary for heating the liquid propane stream from 100 K to 200 K.

Electricity generation in the direct cycle with expansion of propane vapor having an average heat capacity C p = 1.5 kJ / kg · K, in the temperature range 400-100 K, taking into account the efficiency Turbogenerator M = 0.75 can be estimated by the value A m = 1.5 · (400-100) · 0.75 = 337.5 kJ / kg.

Thus, the generation of electricity in the direct cycle (337.5 kJ / kg) can exceed the energy consumption in the reverse cycle (210 kJ / kg) by a practically significant amount.

To drive the compressors in the reverse cycle, it is possible to use a heat engine, and the energy of the exhaust gases to be used to heat the working fluid. In this case, the amount of useful energy generated can be increased, and the degree of conversion of fuel energy into electrical energy can be 80 - 90%.

In Fig. 1 is a schematic diagram of an apparatus for implementing the method, and FIG. 2 - TS diagram of the forward and reverse cycles of the proposed method, where T is the absolute temperature, S is the absolute entropy.

The device includes a forward cycle circuit 1 containing a pump 2, a heater 3, a heat exchanger 4, a throttle 5, an auxiliary heater 6, a turbine 7 with a generator 8, a condenser 9 and a reverse cycle circuit (heat pump) 10 comprising a compressor 11 with stages 12, an expander 13 with steps 14, intermediate heat exchanger 15, regenerative heat exchanger 16 additional compressor 17 with drive 18.

To implement the method as a working fluid, it is expedient to use mixtures of hydrocarbons with a content of 2 to 4 carbon atoms in the molecule, and as a coolant - air or nitrogen.

The method can be carried out as follows. A liquid working medium with a temperature lower than the ambient temperature, for example 100 K (-173 ° C) after the condenser 9, is compressed by the pump 2 to pressures above the critical pressure and transported along the forward cycle 1, where it is subsequently heated in the heater 3, Temperature of 140 K (-133 o C), heat exchanger 4, for example, to a temperature of 220 K (-53 o C), the working medium is throttled with a decrease in its pressure to values ​​close to the critical value in the throttle 5.

With this throttling, the heat capacity of the liquid working fluid decreases, accompanied by an increase in its temperature. Further, the working medium is heated, evaporated and superheated in the additional heater 6 using an external heat source, and the superheated vapor formed, for example, at a temperature of 400 K (+127 ° C), is expanded in the turbine 7 to generate electricity by a generator 8. Passing Turbine, the steam expands and is cooled to a condensation temperature of, for example, 100 K. After the turbine 6, the steam is fed to the condenser 9, which is cooled by the reverse cycle refrigerant.

The refrigerant circulates in the reverse cycle circuit 10. The refrigerant enters the compressor 11, cooled to a temperature close to the condensation temperature, for example. 110 K. In the stages of the compressor 12, the compression ratio of the working fluid is increased, for example by 2 to 8 times, with intermediate cooling of the coolant by the working medium in the heater 3. After the compressor, the refrigerant is further cooled to a condensation temperature of, for example, 100 K, in the intermediate heat exchanger 15 by a refrigerant , Emerging from the condenser. The refrigerant cooled after the compressor is then fed to the expander 13, where it is subsequently expanded and cooled in stages 14 with intermediate heating of the refrigerant in the condenser 9. The work released in the expander is consumed to drive the compressor. Further, the refrigerant is heated in series in the intermediate heat exchanger 15, for example, to a temperature of 108 K, the regenerative heat exchanger 16, for example, to a temperature of 135 K, and compressed by an additional compressor 17 with an increase in the refrigerant pressure, for example 2-10 times, and temperatures, for example, 200 K - 220 K. Then, the refrigerant is cooled, for example, to a temperature of 140 K - 150 K, the working medium in the heat exchanger 4, the coolant in the regenerative heat exchanger 16 and returned to the compressor at a temperature close to the condensation temperature of the working fluid.

The FIG. 2, the TS diagram of the direct-steam-power and reverse-refrigeration cycles explains their interaction with each other.

In Fig. 2 - it is indicated: T - absolute temperature of the refrigerant; S is the absolute value of entropy; T n , T oc and T k are, respectively, the absolute temperature of the heating of the vapors of the working fluid, the surrounding medium, and the condensation temperature of the vapors of the working fluid.

In an ideal direct steam-power cycle in FIG. 2 shows the following processes:

1-2 - adiabatic compression of the liquid working medium by a pump;

2-3 - heating of the working fluid in the heater 3;

3-4 - heating of the working fluid in the heat exchanger 4;

4-5 - throttling of the working fluid by a throttle 5;

5-6, 6-7, 7-8 - respectively, heating, evaporation and superheating of the vapors of the working fluid in the additional heater 6;

8-9 - expansion of the vapors of a working fluid in a turbine with generation of electric power in an electric generator 8;

9-1 - condensation of the vapors of the working fluid in the condenser 9.

In the reverse refrigeration cycle of FIG. 2 shows the following processes:

10-11-12 - multi-stage compression of the refrigerant in the compressor 11 with intermediate cooling in the heater 3;

12-13 - Cooling of the coolant in the intermediate heat exchanger 15;

13-14 is a multi-stage expansion of the refrigerant in expander 13 with intermediate heating in condenser 9;

14-15 - heating of the coolant in the intermediate heat exchanger 15;

15-16 - heating of the coolant in the regenerative heat exchanger 16;

16-17 - compression of the refrigerant in the additional compressor 17;

17-18 - cooling of the refrigerant in the heat exchanger 4;

18-10 - Refrigerant cooling in the regenerative heat exchanger 16.

To further explain the effects of the combination of cycles in FIG. 2 diagrams of the following Carnot cycles equivalent in degree of thermodynamic perfection;

19 - direct steam-power cycle of the proposed method;

20 - the Lorenz refrigeration cycle of the proposed method;

21 - the traditional conventional refrigeration cycle with the output of heat of low level to the level of the environment;

22 - the direct power cycle, which is a combination of a forward cycle with the number 19 and a reverse cycle with the number 20.

The shaded section of cycle number 22 characterizes the additional energy effect of the proposed method.

In addition, the broken line in Fig. 2 characterizes the multistage process of compression and expansion of the refrigerant.

Thus, it follows from the submitted materials that the proposed method is new, has an inventive step and can be effectively applied in industry.

USED ​​BOOKS

1. E. Grechneva, I. Gritsevich. The project of introduction of ecologically clean technology of JSC "Cryocor", "Energy efficiency", M., Center for Effective Energy Use (CENEf), No. 5, p. 12 to 13.

2. Shelest P. A half-century anniversary of one idea. - "Science and Life", 1993, N 2, p. 152-153.

3. VS Martynovsky. Cycles, schemes and characteristics of thermotransformers, - M., Energia, 1979, p. 50 - 55.

4. G. Heinrich, H. Nyork, V. Nestler. Heat pump systems for heating and hot water supply. - M., Stroiizdat, 1985, p. 37 - 45.

5. N.L. Staskevich, D.Ya. Wigdorczyk. Handbook of liquefied gases. - L., Nedra, 1986, p. 24 - 93.

CLAIM

A method for producing electric power, comprising a direct energy cycle in which the liquid working medium is compressed, then heated and evaporated, the resulting vapors are expanded in the turbine to generate electricity and condense after the turbine, and a reverse energy cycle in which the coolant is compressed in the compressor with increasing pressure Cooled after the compressor by the transfer of heat to the working fluid and expansion in the expander with a decrease in the refrigerant pressure, characterized in that the condensation of the working fluid is carried out at a temperature lower than ambient temperature, the temperature of the refrigerant before compression in the compressor is reduced below ambient temperature by recuperative heat exchange, The expander is cooled to a temperature below the condensation temperature of the working fluid and fed to the condenser to drain the heat of condensation, and heating and evaporation of the working fluid in front of the turbine is carried out using an additional heat source.

2. A method according to claim 1, characterized in that a heat source (liquid or gas) with a temperature of 50 ° -150 ° C. is used as an additional heat source.

3. The method according to claim 1 and 2, characterized in that the condensation of the vapors of the working fluid is carried out at 70-120 K.

4. A method according to claims 1 to 3, characterized in that the refrigerant before the compression in the compressor is cooled to the condensation temperature of the working fluid.

5. Method according to claims 1 to 3, characterized in that cooling of the refrigerant before the compressor is carried out by a compressed working body.

6. A method according to claims 1-5, characterized in that the cooling of the refrigerant before the compressor is additionally carried out with a coolant exiting the condenser.

7. The method according to claims 1-6, characterized in that the cooling of the refrigerant after the compressor is additionally carried out by a coolant exiting the condenser.

8. A method according to claims 1-7, characterized in that the refrigerant pressure after the expander is increased by an additional compressor.

9. A method according to claims 1-8, characterized in that the compression and expansion of the refrigerant are carried out in several stages.

10. Method according to claims 1-9, characterized in that light hydrocarbons having a content of 2 to 4 carbon atoms in a molecule whose critical temperature is higher than ambient temperature are used as the working fluid.

11. The method according to claims 1-10, characterized in that the working body after the condenser is compressed to a pressure 2 to 4 times higher than the critical one.

12. The method of claim 1. 1 to 11, characterized in that air is used as the refrigerant.

13. An apparatus for generating electric power, comprising: a forward cycle circuit for circulating a working fluid in which a pump, heater, turbine with an electric generator and a capacitor are connected in series, and a reverse cycle circuit for circulating the refrigerant in which the compressor is connected to the expander through a heater, That the circuit of the forward cycle after the heater is equipped with a heat exchanger for cooling the refrigerant included in the reverse cycle circuit before the compressor, the expander is connected to the condenser, and the forward cycle circuit in front of the turbine has an additional heater connected to an external source of thermal energy.

14. The device of claim 13, wherein the reverse cycle circuit comprises an additional compressor in communication with the condenser and the heat exchanger.

15. The device according to claims 13 and 14, characterized in that an intermediate heat exchanger is connected in the reverse cycle circuit, connected to the compressor and expander on one side, and to the condenser and an additional compressor on the other.

16. The device according to claims 13-15, characterized in that the reverse cycle loop is provided with a regenerative heat exchanger communicating on one side with a heat exchanger and a compressor, and on the other with an intermediate heat exchanger and an additional compressor.

17. The device according to claims 13 to 16, characterized in that the expander comprises several stages connected to the condenser.

18. Apparatus according to claims 13-17, characterized in that the forward cycle circuit in front of the additional heater comprises a throttle.

print version
Published on February 13, 2007