US20140123643A1

US20140123643A1 - Equipment and method to generate electricity by drawing high temperature geothermal

Info

Publication number: US20140123643A1
Application number: US13/885,212
Authority: US
Inventors: Ming Lu
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-07-25
Filing date: 2012-07-14
Publication date: 2014-05-08
Also published as: CN102269534A; CN102269534B; WO2013013645A1; WO2013013582A1; US9508041B2; US20140129501A1

Abstract

This invention is to give an applicable and effective equipment and method to generate electricity by drawing high temperature geothermal based on principle of heatpipe. It includes an evaporator (1), a condenser (2), a discharge valve (21), a vapor line (19), an electronically controlled throttle valve for gas (18), a main returning line (22), an electronically controlled throttle valve for liquid (23), an inter-returning line (24), a steam turbine (7).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to the equipment of geothermal power generation. The invention particularly concerns an equipment and method to generate electricity by using high temperature geothermal transferred to ground through continuous gas-liquid phase transition.
Description of Prior Developments
The geothermal resource is a new clean energy in the earth. It generally refers to the geothermal buried within 10 km depth of underground and has the economic value of development and utilization under the current technology. The geothermal with temperature lower than 150 C° is called the low-medium temperature geothermal, which can be used directly; while that higher than 150 C° is called the high temperature one, which mainly is used to generate electricity. Based on the thermodynamics cycle theory, the higher temperature differential exists, the higher thermo efficiency happens.
Geothermal power generation refers to several modern scientific and technological domains, such as geology, earth physics, chemistry, drilling, materials science, power engineering, etc. Like the basic principle of other thermal power generation, based on the energy transfer, the geothermal power generation starts from transferring the geothermal to the mechanical energy, then to the electricity. Currently, the underground thermal water and fry steam with temperature higher than 200 C° is used to power generation. For the underground dry steam, it needs to lead the dry steam from underground into the steam turbine to work, but the dry steam needs to be purified firstly. For the underground hot water, it needs to use underground hot water to heat working substances with low boiling point, such as chlorine ethane, Freon, to produce steam, and then leads the steam into the steam turbine to work, which is also known as the double cycle geothermal power generation. The FIG. 1 shows the principle scheme for the double cycle system of geothermal power generation, where the high temperature underground water (4) is drawn from the geothermal well (3) by the pump (5) and conducted into the evaporator (1) for purpose of heating. At the other aspect, the working substance with low boiling point (6) is led by working substance pump (8) into another evaporator and is vaporized into the high temperature steam, which comes into the steam turbine (7) to generate power output (10). After then, the vaporized working substance becomes the liquid again in the condenser (2). After heating the working substance (6), the high temperature underground water (4) flows out of the evaporator (1) and back into ground through the water returning system (9).
For the geothermal power system mentioned above, it needs a large heat transfer area of evaporator (1) and condenser (2) due to the low heat transfer capacity of the low boiling working substances (6), which increases the manufacture cost and difficulty. The low boiling working substances are of unstable, flammable, toxic, and prone to leak to contaminate environment. In others, the water returning system, which is necessary to prevent falling of water table and land subsidence, increase the cost of geothermal power exploitations and utilizations. Moreover, a lot of corrosive and scaling substances, such as hydrogen sulfide, carbon dioxide, and other in the compound of the calcium carbonate or silica, in the underground water and steam could severely corrode the turbine, pipes and other equipments. All aspects mentioned above adversely affect the geothermal power.
In short, the current geothermal power technology has the unfavorable factors on high cost of construction and maintenance, low efficiency and reliability of working substances. To overcome those malpractices to utilize the geothermal power more efficiently, it needs to develop the new simple, practical, low-cost, efficient, reliable and durable equipment and method.
To finish the purpose above, firstly, the traditional method drawing water to the ground like in the FIG. 1 is banished. Instead, the evaporator (1) can be set underground and directly heated by the high temperature geothermal. The working substance in the evaporator is vaporized into steam and is conducted into the turbine on ground through an adiabatic pipe to work. After the condenser (2), the liquefied working substance is sent back to underground to vaporize. This loop cycle carries on continually. The principle of transferring heat to ground using continuous gas-liquid phase transition of working substance is classified as that of using heatpipe. This method has several favorable aspects. Firstly, its heat transfer efficiency is as a few ten times as general metals, and it can conduct heat far with less heat losing. In addition, it can modify the heat flux density by changing heating area. For example, it is possible to input heat with less heat area, while output that with larger cooling area, vice versa. The principle of heatpipe can be designed into several practical schemes in the engineering applications. The FIG. 2, as the scheme on drawing high-temperature geothermal to power based on the principle of heatpipe, shows that the evaporator (1) is set at the bottom, where is the high temperature zone, and is connected with the condenser (2) set upper on the ground through the adiabatic vapor pipe (12) conducting vapor flow (13) and returning pipe (15) conducting liquid flow (14) of working substance. When the heat source (11) is added to the evaporator (1), the liquid working substance is vaporized into high pressure vapor and flows up toward the condenser (2) with low temperature and pressure. The adiabatic connecting pipe (12,15) prevents the heat losing. In the condenser (2), the working substance releases the latent heat (16) and condenses into liquid. Since the condenser (2) is on upper, there is a pressure head to make the liquid working substance automatically flow back to the evaporator (1) at bottom. The heat transfer on the phase changing is carried out at the heat and cool ends and the process can keep on and comes to a steady state if the added and released heat is equal. The principle, method and relative equipment shown in FIG. 2 is simple and practical, avoiding to pumping the geothermal water or steam into any pipe equipment and reducing the construction and maintenance cost.
There are some technical problem required to solve for the application of this method. Firstly, it needs to use the high boiling point working substances with high heat transfer coefficient, such as water, methanol, etc., to guarantee heat transfer capacity to make the evaporator volume as small as possible. Secondly, those working substances being liquid under normal temperature may form the vapor films under high environment temperature on the inner wall of the evaporator. A lot of vapor bubbles are formed on the wall replacing the liquid away from the wall, which reduces the heat transfer capacity of heatpipe since the heat transfer coefficient of gas is much lower than that of liquid. This is why any heatpipe works worse under high temperature. Besides that, both liquid and vapor flows in opposite directions. The shear force occurring at the liquid-vapor interfaces may inhibit some liquid back to the evaporator. When it occurs, a further increase in the heat input to the evaporator leads to liquid droplets being entrained in the vapor flow and carried to the condenser, eventually causing dry out of the evaporator. It can make the equipment damaged.

SUMMARY OF THE INVENTION

The purpose of this invention is to give an applicable and effective equipment and method to generate electricity by drawing high temperature geothermal. The working principle is based on that of heatpipe. The originality of this invention is that methodically directly drawing high temperature geothermal through the evaporator located underground using the working substance with high heat transfer coefficient; structurally rotating the two phase flows in the matched inter wall of the evaporator through the inter-returning line to cancel the vapor film; directly inserting the inter-returning line into the bottom of the evaporator to avoid the liquid droplet entrainment.
Those properties make the device work safely and reliably under high temperature environment.

The Technical Scheme of the Invention

The FIG. 3, the schematics of about an equipment and method to generate electricity by drawing high temperature geothermal according this to invention, shows that It includes an evaporator (1), a condenser (2), a discharge valve (21), a vapor line (19), an electronically controlled throttle valve for gas (18), a main returning line (22), an electronically controlled throttle valve for liquid (23), an inter-returning line (24), a steam turbine (7); and
there is a vapor outlet and a liquid inlet on the top of the evaporator (1);
there is a vapor inlet and a vapor outlet on the steam turbine (7);
there is a vapor inlet and a liquid outlet on the condenser (2);
the vapor outlet on the evaporator (1) is connected with the vapor inlet on the steam turbine (7) through a vapor connecting line (20), which makes the vapor come into the steam turbine (7);
an electronically controlled valve for gas (18) is installed in the vapor line (19) to adjust the vapor flow (13);
the vapor outlet on the steam turbine (7) is connected with the vapor inlet on the condenser (2), which makes the vapor come into the condenser (2) after working in the steam turbine (7);
there is a discharge valve (21) in the upper of the condenser (2);
one end of a main returning line (22) is connected with the liquid outlet of the condenser (2);
the other end of the main returning line (22) is connected with one end of an inter-returning line (24);
an electronically controlled valve for liquid (23) is installed in the main returning line (22) to control the liquid flow (14) into the condenser (2);
the other end of the inter-returning line (24) is inserted from the liquid inlet up to the bottom of the evaporator (1).
The evaporator (1) is located underground zone with high temperature geothermal, while the condenser (2) and the steam turbine (7) are done on the ground. The evaporator (1) is made of metal and cylinder- or truncated right cone-shaped. The shape of the evaporator cavity is truncated conical or cylindrical. All the lines are covered with the adiabatic materials.
The liquefied working substance is conduct into the bottom of the evaporator (1) through the main returning line (22) and inter-returning line (24), which avoids the evaporator drying out due to the liquid droplets entrainment that is caused by the shear force from the liquid and vapor flows in opposite directions.
The FIG. 4 describes the structure details of inter-returning line and evaporator presented in the FIG. 3. There are several rifling lines (25) on the inner surface and screw threads (26) on the outer surface of the inter-returning line (24) and the rotational directions of the rifling lines (25) and screw threads (26) are identical. Since the condenser (2) is higher than the evaporator (1) with a liquid head, the liquefied working substances flowing down in the inter-returning line (24) begin to rotate through the rifling lines (25) conduction. The liquid with some momentum of inertia, coming into the evaporator cavity and being vaporized gradually in the high temperature environment, becomes the vapor-liquid droplet two-phase flow (17). With the increasing of the pressure in the evaporator (1), the two-phase flows start to rotationally move upward with the centrifugal force through the conduction of the screw threads (26) on the outer surface of the inter-returning line (24). Under high environment temperature, the vapor films generally form on the inner wall of the evaporator (1). A lot of vapor bubbles are accumulated on the wall replacing the liquid away from the wall, which reduces the heat transfer capacity of the wall. However, the density of the liquid droplet is larger than that of vapor, the liquid droplets under the centrifugal force fly towards the wall of the evaporator (1) to smash the vapor bubbles and replace with liquid films. This movement recovers the heat transfer capacity of the wall of the evaporator (1) locally.
The FIG. 5 shows the force analysis of a liquid droplet on the wall of the evaporator with truncated right angle conical shape. It shows that the landing liquid droplet (29) on the inclined wall (27) takes resultant of forces (32) from gravity (28), wall reflection (30), results of (31) and centrifugal, centrifugal force (33) moves upward, which results the liquid film fully contacting to the heated wall, which is good for the liquid film vaporized. The larger diameter of the upper of evaporator (1) with truncated right angle conical shape makes the centrifugal force (33) less, which could make the flying liquid droplets cannot reach and cannot form the liquid film on the wall (27) of the evaporator (1). In this situation, the evaporator (1) with cylindrical shape has to be used to keep the centrifugal force. The selection of different shapes of the evaporator is based on the liquid head (height differential) between the evaporator (1) and the condenser (2). For the large liquid head, it is better to use the truncated right angle conical shape, since the large moment of inertial exists; while, on the contrary, the cylindrical shape is better.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIG. 1 is the principle scheme for the double cycle system of geothermal power generation

The FIG. 2 is the scheme on drawing high-temperature geothermal to power based on the principle of heatpipe

The FIG. 3 is the schematics of about an equipment to produce electricity by drawing high temperature geothermal according this to invention

The FIG. 4 is the structure details of inter-returning line and evaporator

The FIG. 5 is the force analysis of a liquid droplet on the wall of the evaporator

The FIG. 6 is the schematics of an equipment to generate electricity by drawing high temperature geothermal in the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principle and structure of the present invention will be more particularly described by an embodiment. The FIG. 6 is the schematics of an equipment and method to generate electricity by drawing high temperature geothermal in the embodiment according to this invention.
It includes an evaporator (1), a condenser (2), a discharge valve (21), a vapor line (19), an electronically controlled throttle valve for gas (18), a main returning line (22), an electronically controlled throttle valve for liquid (23), an inter-returning line (24), a steam turbine (7).
Water, as the working substance with a large heat transfer coefficient, is atoxic, low cost and resourceful. The evaporator (1), condenser (2), and all connecting lines (19), (20), (22), (24) are made of the high temperature resistant stainless steel, since it has a large heat conduction and has strong resistance to oxidation and deformation. The lines (19) and (22) are covered with the adiabatic materials and put into a protecting cover (34) with anti-corrosion and impact resistance.
There is a vapor outlet and a liquid inlet on the top of the evaporator (1); there is a vapor inlet and a vapor outlet on the steam turbine (7); there is a vapor inlet and a liquid outlet on the condenser (2); the vapor outlet on the evaporator (1) is connected with the vapor inlet on the steam turbine (7) through a vapor connecting line (20), which makes the vapor come into the steam turbine (7); an electronically controlled valve for gas (18) is installed in the vapor line (19) to adjust the vapor flow (13); the vapor outlet on the steam turbine (7) is connected with the vapor inlet on the condenser (2), which makes the vapor come into the condenser (2) after working in the steam turbine (7); there is a discharge valve (21) in the upper of the condenser (2); one end of a main returning line (22) is connected with the liquid outlet of the condenser (2); the other end of the main returning line (22) is connected with one end of an inter-returning line (24); an electronically controlled valve for liquid (23) is installed in the main returning line (22) to control the liquid flow (14) into the condenser (2); the other end of the inter-returning line (24) is inserted from the liquid inlet up to the bottom of the evaporator (1).
The evaporator (1) is located in the 2000-3000 meter deep in underground thermal water and fry steam with temperature higher than 200 C°. The condenser (2) and steam turbine (7) are located on the ground. The shape of the evaporator cavity is truncated right angle conical.
The inter-returning line (24) is insert into the bottom of the evaporator (1), which avoids the evaporator (1) drying out due to the liquid droplets entrainment that is caused by the shear force from the liquid and vapor flows in opposite directions.
The FIG. 4 describes the structural details of inter-returning line in the embodiment. There are 6 rifling lines (25) with 0.01 m deep on the inner surface and there are screw threads (26) with 0.01 m deep and the same rotation direction on the outer surface of the inter-returning line with 0.3 m outer diameter and 0.2 m inner diameter. Since the condenser (2) is 2000-3000 meter higher than the evaporator (1) with a liquid head, the water flowing down in the inter-returning line (24) begins to rotate through the rifling lines (25) conduction. The water with some momentum of inertia, coming into the evaporator (1) and being vaporized gradually in the high temperature environment, becomes the water vapor-droplet two-phase flow. With the increasing of the pressure in the evaporator (1), the two-phase flow starts to rotationally move upward with the centrifugal force through the conduction of the screw threads (26) on the outer surface of the inter-returning line (24). Some momentum of inertia loss because of the friction and viscosity of the water vapor-droplet two-phase flow.
The evaporator with the truncated right angle conical shape has the sloped wall. Referring the FIG. 5, where shows that the landing water droplet on the sloped wall taking resultant of forces moves upward to result the water film fully contacting to the heated wall, which is good for the water film vaporized. The diameter of the upper of evaporator (1) with truncated right angle conical shape is 1 meter, the height of it is 1.5 meter and the coning angle is 15°.
The water vapor with high temperature and high pressure comes into the steam turbine (7) and pushes the rotor rotating to generate electricity (10). The condenser (2) releases the heat to change the water vapor to liquid water. Inside the condenser (2), there is a cooling system (35) based on cycling water. The cycling water absorbs the heat of the water vapor to make it reduce temperature of vapor to a liquid water state, which comes back into evaporator (1) again.
The present invention creates the equipment and method to generate electricity by using high temperature geothermal transferred to ground through continuous gas-liquid phase transition based on principle of heatpipe. Particularly, directly locate the evaporator in underground geothermal, use water as working substance, and design unique components, which makes the equipment work in highly thermal efficient, structurally simple, low costly, and reliable.

Claims

1. An equipment and method to generate electricity by drawing high temperature geothermal includes an evaporator (1), a condenser (2), a discharge valve (21), a vapor line (19), an electronically controlled throttle valve for gas (18), a main returning line (22), an electronically controlled throttle valve for liquid (23), an inter-returning line (24), a steam turbine (7); and

there is a vapor outlet and a liquid inlet on the top of the evaporator (1);

there is a vapor inlet and a vapor outlet on the steam turbine (7);

there is a vapor inlet and a liquid outlet on the condenser (2);

the vapor outlet on the evaporator (1) is connected with the vapor inlet on the steam turbine (7) through a vapor connecting line (20), which makes the vapor come into the steam turbine (7);

an electronically controlled valve for gas (18) is installed in the vapor line (19) to adjust the vapor flow (13);

the vapor outlet on the steam turbine (7) is connected with the vapor inlet on the condenser (2), which makes the vapor come into the condenser (2) after working in the steam turbine (7);

there is a discharge valve (21) in the upper of the condenser (2);

one end of a main returning line (22) is connected with the liquid outlet of the condenser (2);

the other end of the main returning line (22) is connected with one end of an inter-returning line (24);

an electronically controlled valve for liquid (23) is installed in the main returning line (22) to control the liquid flow (14) into the condenser (2);

the other end of the inter-returning line (24) is inserted from the liquid inlet up to the bottom of the evaporator (1).

2. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said evaporator (1) is made of metal and cylinder- or truncated right cone-shaped and is located underground zone with high temperature geothermal.

3. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said condenser (2) and steam turbine (7) are done on the ground.

4. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said the lines (19), (22) and (24)are covered with the adiabatic materials.

5. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said inter-returning line (24) is insert into the bottom of the evaporator (1).

6. An equipment and method to generate electricity by drawing high temperature geothermal according to claim 1 wherein said inter-returning line (24) bears with several rifling lines (25) on the inner surface and screw threads (26) on the outer surface, and the rotational directions of the rifling lines (25) and screw threads (26) are identical.