WO1997001021A1

WO1997001021A1 - Method and apparatus for generating power from low temperature source

Info

Publication number: WO1997001021A1
Application number: PCT/CN1995/000075
Authority: WO
Inventors: Zhanman Huo; Yeqin Chen
Original assignee: Kong, Dexing; Zhang, Qingyun
Priority date: 1995-06-23
Filing date: 1995-09-14
Publication date: 1997-01-09
Also published as: CN1139182A; AU3469495A

Abstract

The invention relates to a method and an apparatus for generating power (shaft output and cool energy) from low temperature source. The apparatus has a system including a heater (3), turbines (4, 5, 9), condenser-evaporator (2), a heat exchanger (22), a condenser (8), a trough for storing liquid (1), a high pressure pump (6), centrifugal pumps (7, 10). The system constructs a continual return circuit together with a deep cooling pipeline system and a flash-vaporization cooling system, wherein said deep cooling working fluid is cycling in said circuit. The working fluid is heated in the heater (3) by low temperature energy of atmosphere air, then the air is cooled. The working fluid is expanded in the turbines (4, 5, 9) to generate shaft output. Vaporous working fluid is expanded and then liquefied to be deep cooling working fluid for recycle use.

Description

Method and device for generating power from low-temperature energy

The invention relates to a method and a device for generating power (shaft work and cooling capacity) by utilizing a temperature difference between the cooling capacity of cryogenic liquid nitrogen (or liquid air) and the low-temperature heat in nature.

Background of the invention

Existing methods of generating power (such as thermal power generation) use the heat generated by the combustion of fuel to turn water into steam, pushing the turbine to perform work, and driving the generator to generate electricity. In this way, the actual process of converting thermal energy into mechanical energy (shaft work) and then into electrical energy (or other power) is realized.

In the process of generating power (such as power generation), 7j steam works through the turbine, the temperature drops sharply, and a large amount of heat is consumed. Only by continuously supplying fuel and burning it to generate heat can the normal operation of thermal power generation be guaranteed. Also in the process of obtaining low-temperature cooling capacity, removing heat from the system requires work to be consumed. Therefore, the acquisition of cooling capacity should be considered as power consumption. Conversely, the generation of cold energy is, in a sense, the acquisition of power.

Summary of the invention

The object of the present invention is to propose a method and a device for generating power (shaft work and cooling capacity) by utilizing a temperature difference between the low-temperature heat existing in nature and the cooling capacity of cryogenic liquid nitrogen (or liquid air). Liquid nitrogen (or liquid air) can be recycled in its continuous loop to achieve the use of low-temperature thermal energy in nature to replace the thermal energy generated by fuel combustion. The object of the present invention can be achieved by the following measures: the air heats the working medium (liquid nitrogen or liquid air), and at the same time the air obtains cooling capacity; the working medium expands to generate work (shaft work); the working medium is cold and hot; The working fluid is a system formed by two-phase turboexpander and liquid turboexpander expanding again to generate cold output shaft work. The system includes:

-A continuous loop consisting of heaters, turbine expanders, condensation-evaporation heat exchangers, heat exchangers, condensers, liquid storage tanks, high-pressure pumps, cryogenic pipelines and flash gas refrigeration systems;

-Cryogenic liquid nitrogen (or liquid air) circulates in the circuit;

-Using natural air as a heat source, cold nitrogen (or cold air) is heated by a heater to obtain energy, and the working fluid is transposed by cold and heat, gas turbine expander, two-phase turbine expander, liquid turbine The flat expander generates external shaft work and obtains cold energy and liquefies it for circulation use;

-Flash gas entering the liquid storage tank is liquefied by the refrigeration system and returned to the liquid storage tank.

Brief description of the drawings

FIG. 1 is a schematic diagram of a system used in the present invention.

Implementation method of the present invention

The invention is described in detail below with reference to the drawings.

As shown in FIG. 1, the air fan 20 for natural air passing through the purification and drying device 19 blows it into the heater 3 through the regulating valve 16, and applies high-pressure nitrogen gas from the condensation-evaporation heat exchanger 2 and the heat exchanger 22 (or High-pressure air, pressure 6. 45-7. 45 MPa, temperature 190-195 K), heated to a temperature of 2 70-2 8 0 K, and then introduce high temperature and high pressure nitrogen (or air) into the gas turbine expander 4, It is expanded to do work under adiabatic isentropic and output shaft work. At the same time, the natural air in the heater 3 is cooled to generate a cooling capacity, which can be used as a cold source for various purposes. Use.

After the adiabatic isentropic expansion of nitrogen (or air), its pressure and temperature decrease (pressure 1.8-2.2 MPa, temperature 185-195K), and then enter the condensation-evaporation heat exchanger 2, and the nitrogen (or air) Pressured liquid storage tank 1 and high pressure pump 6 to subcooled liquid nitrogen 6.5-7.5 MPa

(Or liquefied air) under cooling (the supercooled liquid is heated and sent to heat exchanger 2 2 and heater 3), it is partially condensed into a two-phase fluid with a temperature of 116K, which is introduced into a two-phase turboexpander

5. The working fluid expands the output shaft work, and the two-phase fluid obtains cold capacity (temperature drops to 8 4-86 K, pressure 0.2- G.25MPa). The two-phase fluid is introduced into the condenser 8 to condense all of it; the cooling liquid is from the liquid storage tank 1 and is pressurized to 0.8-l. OMPa of subcooled liquid nitrogen (or liquid air) by the pump 7. Subcooled liquid nitrogen (or liquid air) is heated to 83-85 K in condenser 8, and after leaving condenser 8, it is combined with the condensate (through pump 10 and regulating valve 21) into the liquid turboexpander. 9. The working fluid expands the output shaft work in the liquid turbine expander and obtains the cooling capacity at the same time. The liquid nitrogen (or liquid air) leaving the liquid turboexpander has a temperature of 77K and a pressure of 0.1-0.12MPa. It enters the liquid storage tank for 1 cycle use. The flash gas that enters the liquid t tank at the same time as the liquid nitrogen (or liquid air) passes through the refrigeration system 1 1, 1 2, 1 3, 1 4 to be liquefied and returns to the liquid storage tank.

The whole system uses better low-temperature insulation materials to isolate it from the external environment to ensure the good operation of the system.

The characteristics of the system process and the device adopting the invention are: the low-temperature heat of natural air is used to heat the cryogenic gas nitrogen (or cryogenic air) to obtain energy, and the axial work is generated by the turbine expander to perform external work. At the same time, The heated air is cooled to generate cold energy. Achieved the use of low-temperature heat in nature to replace the heat obtained from fuel combustion to generate power (shaft work and The amount of cold). The working fluid is transposed by cold and heat, and the turbine expands to liquefy it to achieve its recycling. In terms of effect, when IKg / s of liquid nitrogen is gasified, after deducting various power consumptions in the system, the net output shaft power of the system is about 20 KW, and at the same time, the temperature of IKg / s is about 20.5 K The amount of air cooling can be used as a cold source for various purposes.

Claims

Rights request

1. A method for generating power by heating a cryogenic working medium with natural air, the method comprising the following steps:

a) Use a low-temperature heat source in nature to heat the condensing-evaporating heat exchanger from the liquid storage tank through the heater to obtain a high-pressure, high-temperature gas chemical;

b) Inject high-pressure and high-temperature gas chemicals into a gas turbine expander to expand and perform work under adiabatic isentropic conditions;

c) The gaseous working fluid that has been expanded by the turbine is input to the condensation-evaporation heat exchanger for heat exchange with the pressurized cryogenic working fluid from the liquid storage tank to partially condense it into a two-phase fluid;

d) introducing the two-phase fluid into the two-phase turboexpander, so that the working fluid expands again to perform work, and the working fluid temperature decreases;

e) The expanded two-phase fluid is conveyed into the condenser for heat exchange with the pressurized cryogenic liquid working medium from the liquid storage tank to condense the gaseous working medium, and the condensed liquid and the heated liquid working medium together When entering the liquid turbine expander, the working fluid expands and works while the temperature further decreases;

D The expanded liquid working medium is transported to the liquid storage tank, and the gas working liquid that enters the liquid storage tank with the liquid working fluid is returned to the liquid storage tank after being liquefied through a refrigeration system.

2. The method according to claim 1, characterized in that, before the cryogenic working fluid enters the heater, it is passed through a condensing-evaporating heat exchanger, the heat exchanger, and the expanded working fluid and the expanded gaseous working fluid and entering the refrigeration system. The flash gas is vaporized for heat exchange.

3. The method according to claim 2, characterized in that the pressure of the subcooled liquid working fluid entering the condensing-evaporating heat exchanger is 6.5-7.5MPa, and the temperature is about 77K; when leaving, the gaseous working temperature becomes 126-132K The inflated gaseous working medium that enters has a pressure of 1.8-

2.2 Pa, a two-phase fluid with a temperature of 185-195K and about 1 1 6 K when leaving.

4. The method according to claim 1, characterized in that the pressure of the gaseous working medium entering the heater is 6.45-7.45 MPa, the temperature is 19 0-1 9 5 K, and the temperature at the time of leaving is 2 7 0-

2 8 0 K; and the temperature of the flowing natural air is 2 9 3-2 9 8 K, and the temperature at the time of leaving is 2 0-2 0 5 K.

5. The method according to claim 1, characterized in that the pressure of the liquid working medium flowing into the condenser is 0. 8-1. 0 MP a, the temperature is about 7 7 K, and the temperature at the time of leaving is 83- 85K, and the temperature of the two-phase fluid flowing into the condenser is 8 4-8 6 K, and it leaves the condensate at this temperature.

6. Device for implementing the method according to claim 1, characterized in that the device is a liquid storage tank (1) heater (3), a gas turbine expander (4), a two-phase turbine expander (5), liquid turbine expander (9), condensation-evaporation heat exchanger (2), heat exchanger (22), condenser (8), flash gas refrigeration system (1 1, 1, 2, 1 3 , 1 4) and pump (6, 7, 10) and the circulation system composed of cryogenic pipelines.

The device according to claim 3, characterized in that the condensing-evaporating heat exchanger (2) is a plate-fin heat exchanger under low temperature conditions, which has two populations and two outlets, and one population is safe. From the pipeline of the liquid storage tank, another population is used to enter the gaseous working fluid expanded by the gas expander; one of the two outlets is a heat exchanger, and the other is a two-phase expander.

8. The device according to claim 4, wherein the heater is a plate-fin type Heater.

9. The device according to claim 5, characterized in that the condenser (8) is a plate-fin heat exchanger working under low-temperature conditions, and has two populations, one of which comes from a storage tank and passes through it. A centrifugal pump (7) pressurized cryogenic liquid working medium, the other is a two-phase fluid expanded by a two-phase expander; there are two outlets, one of which outputs condensate, and the other is heated. Liquid working fluid.

10. The device according to claim 6, characterized in that the turboexpander is an expander under low-temperature operating conditions, and they are respectively a gas turboexpander 4 and a two-phase (gas, liquid) turbine expansion机 5 and Liquid turbine expander 9. The gas working medium pressure entering the gas turbine expander is 6.4-7.4MPa, the temperature is 270-280K, the pressure when leaving is 1.8-2.2 MPa, the temperature is 185-195K; entering the two-phase (gas, liquid) permeability Two-phase fluid with a flat working expander working pressure of 1.8-2.2MPa and a temperature of 1 16 K. Two-phase fluid with a pressure of 0 · 2-0. 2 5 MPa and a temperature of 8 4-8 6 K when leaving; the working fluid entering a liquid turboexpander is 0.8- 1. 0 MPa and a temperature of 83-85 K Cold liquid nitrogen (or liquid air), liquid nitrogen (or liquid air) and flash gas with a pressure of 0.1-0.12 MPa and a temperature of 7 7 K when leaving.