US20090188254A1

US20090188254A1 - Kinetic steam condenser

Info

Publication number: US20090188254A1
Application number: US12/010,583
Authority: US
Inventors: Muhamed Osman
Original assignee: Miracom Israel 2006 Ltd
Priority date: 2008-01-28
Filing date: 2008-01-28
Publication date: 2009-07-30

Abstract

Method and system for condensing steam at any temperature, the steam being in contact with a large water surface, whereby the relative temperatures of the steam and water are regulated so that the steam is kept at under-saturation pressure and the water temperature is kept at up to 100° C.

Description

FIELD OF THE INVENTION

The present invention relates to steam condensing and more specifically to a steam condensing apparatus and method that save energy and increase efficiency.

BACKGROUND OF THE INVENTION

In power plants, on ships and in industrial plants, steam condensers are used to condense the exhaust steam from a steam turbine to obtain maximum efficiency and also to convert the turbine exhaust steam into pure water (referred to as steam condensate) so that it may be reused in the steam generator or boiler as boiler feed water.
The most prevailing type of steam condenser are surface condensers comprising a water cooled shell and a tube heat exchanger installed on the exhaust steam from a steam turbine in thermal power stations. These condensers are heat exchangers which convert steam from its gaseous to its liquid state at a pressure below atmospheric pressure. Where cooling water is in short supply, an air-cooled condenser is often used.
Most of the heat liberated due to condensation of the exhaust steam in surface condensers is carried away by the cooling medium (water or air) used by the surface condenser. This heat is known to be a significant contributor to global warming and is wasted as a source of energy. Moreover, the energy required to operate surface condensers is considerable.
There is need for an energy saving steam condenser, which will reduce the adverse ecological effects of surface condensers and increase the efficiency of the condensing process.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method of condensing steam at any temperature, the steam being in contact with a large water surface, whereby the relative temperatures of the steam and water are regulated so that the steam is kept at under-saturation pressure and the water temperature is kept at up to 100° C.
According to a first embodiment, the temperature difference between the steam and the water is kept below 10° C.
According to a second embodiment, the temperature difference between the steam and the water is kept below 5° C.
According to a third embodiment, the steam is exhaust steam from a power plant turbine and the condensate is reused as boiler feed water.
According to a fourth embodiment, the temperature regulation comprises heating the steam using hot gases discharged from the power plant's chimney.
According to a fifth embodiment, the temperature regulation comprises heating the steam using fuel burning.
According to a sixth embodiment, the temperature regulation comprises recycling water through cooling means.
According to a second aspect of the present invention there is provided a steam condenser comprising: a steam inlet; a water inlet; a plurality of water receiving surfaces; heating means for heating the steam; control means for maintaining a predefined temperature difference between the steam and the water and for maintaining the water temperature below 100° C.; and a condensate outlet.
According to a first embodiment, the water receiving surfaces comprise a plurality of trays, installed at various heights.
According to a second embodiment, the water receiving surfaces comprise a plurality of trays installed at various heights, each tray comprising a vertical bracket for holding water in the tray and a draining pipe for draining excess water into a lower tray.
According to a third embodiment, the steam heating means comprise pipes leading hot gases.
According to a fourth embodiment, the hot gases are gases discharged from the power plant's chimney.
According to a fifth embodiment, the hot gases are gases produced from burned fuel.
According to a sixth embodiment, the control means comprise: means for measuring the steam temperature in the condenser; and means for controlling the heating means accordingly.
According to a seventh embodiment, the control means comprise: means for measuring the water temperature in the condenser; and means for recycling water through cooling means.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding of the invention and to show how the same may be put into effect, reference will now be made, purely by way of example, to the accompanying drawings.

It is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the accompanying drawings:

FIG. 1 is a schematic diagram of the kinetic steam condenser according to the present invention;

FIG. 2 is a schematic horizontal section along line 2-2 (FIG. 1) of the kinetic steam condenser according to the present invention; and

FIG. 3 is a schematic three-dimensional view of the kinetic steam condenser according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.
The present invention provides a novel approach to steam condensing, whereby the steam is condensed in high temperature, as opposed to condensing by cooling.
The kinetic steam condenser of the present invention is designed for condensing steam discharged from power stations turbines at the end of the electricity production process, or for any industrial plant or ship that use steam for operating their systems.
The kinetic steam condenser of the present invention may be operated in power stations using fuel oil, kerosene, coal, or any other heating means.
The kinetic steam condenser of the present invention uses hot steam discharged from the turbines, thus reducing significantly the energy loss.
FIG. 1 is a schematic diagram of the kinetic steam condenser, according to an embodiment of present invention. The condenser (100) comprises an external housing (110) and an internal housing (115), with an isolation layer (120) therebetween. External housing (110) may be constructed of any suitable material such as concrete or metal. Internal housing (115) may be constructed of any suitable metal such as steel. Isolation layer (120) may comprise any thermal insulating material known in the art and serves to prevent heat loss and to maintain the temperature in the internal housing.
According to one embodiment of the present invention, a combustion chamber (125) at the bottom of condenser (100) serves as heat source for the condenser's operation, where the heat may result from burning fuel oil, kerosene, coal, or any other suitable material in the combustion chamber (125).
According to another embodiment of the present invention, hot gases discharged from power station's chimney may be channeled through combustion chamber (125).
The hot gas from combustion chamber (125) flows through pipes (130), preferably mounted at the center of condenser (100) and spanning it from bottom to top. Pipes (130) may be constructed of any metal, such as steel or copper. The number of pipes and their diameters are adapted to the specific application, taking into consideration the size of the condenser and the required duty cycle.
The gas flows from the pipes (130) upper ends into chamber (135), from which it is released via an exhaust pipe (140) into the atmosphere.
A plurality of water trays (145) are attached to internal housing (115) at different levels, surrounding the pipes (130). Each tray (145) comprises a horizontal platform (150), a vertical bracket (155) on the inner side of the platform (150) and at least one draining pipe (160) drilled through the platform (150). Draining pipes (160) serve to cascade excess water from each tray to the tray below it.
A water temperature regulating system is attached to the condenser, including a suction pipe 165, a radiator (170) for reducing the water's temperature, a pump (175) for pumping water from the radiator (170) and a pipe (180) through which the water is returned to the condenser at the desired temperature. The water temperature regulating system is operated periodically, when the water temperature in the condenser needs to be decreased by a few degrees, as will be explained in detail below.
A steam inlet (185) on the upper part of condenser (100) allows steam from the power plant turbines to flow into the condenser, where it flows freely and is heated by the hot pipes (130).
A distilled water inlet (190) on the upper part of condenser (100) serves for inserting distilled water into condenser (100) before operating it. The water inserted through inlet (190) cascades to the lower trays.
A condensate draining pipe (195) at the bottom of condenser (100) drains the condensed steam which is flown back to the turbine.
Thermometers (205, 210), installed inside the condenser (100), serve for monitoring the temperatures of the steam and the water, respectively, throughout the condensing process.
Air exhaust valve (215), at the upper side of condenser (100), serves for releasing air, repelled by the incoming steam, from the internal housing.
FIG. 2 is a schematic horizontal section of the kinetic steam condenser (100) of FIG. 1, showing the internal housing (115) and a tray (145) surrounding the central pipes (130) and having a vertical bracket (155) and drilled draining pipes (160).
The operation of the kinetic steam condenser of the present invention will now be explained.
The condensing process begins with distilled hot water being inserted into the condenser (100) via water inlet (190). The water is preferably inserted at a temperature below 90° C. The water cascades to the lower trays, so that each tray holds a certain quantity of water.
The steam emerging from the turbines during the electricity production process is at a temperature of less than 100° C. and therefore has pressure of less than 1 atm. and is on the verge of saturation.
The steam is inserted into the condenser (100) through steam inlet (185) and repels the air from within the condenser, through air exhaust valve (215).
Next, the burning chamber (125) is operated, either by burning fuel oil, kerosene, coal, or any other suitable material in it, or by channeling hot gases discharged from power station's chimney into it. The hot gas emanating from the burning chamber (125) flows into pipes (130) and heats the steam in the condenser by a few degrees.
Vapor-liquid equilibrium is a condition where a liquid and its vapor (gas phase) are in equilibrium with each other, a condition or state where the rate of evaporation (liquid changing to vapor) equals the rate of condensation (vapor changing to liquid) on a molecular level, such that there is no net (overall) vapor-liquid interconversion.
The pressure of vapors in a vapor-liquid equilibrium is called saturation pressure, and is constant at any given temperature.
The temperature of the water in the trays (145) is lower by a few degrees than that of the steam, causing the steam, which aspires to a state of saturation pressure at any given temperature, to start condensing into the water. The condensation releases heat into the water and raises their temperature.
The condensation creates vacuum in the condenser, which induces additional flow of steam into the condenser.
This process continues as long as there is a temperature difference between the steam and the water in the condenser, so that saturation pressure is never attained.
Thermometer (205) continuously monitors the steam temperature and the burning rate at the burning chamber (125) is adjusted accordingly, so as to prevent the steam temperature from reaching a predefined temperature. In a preferred embodiment, the steam temperature is kept below 100° C.
Thermometer (210) continuously monitors the water temperature. If the water temperature rises above a predefined temperature, e.g. 90° C., the water temperature regulating system is operated, whereby water from the bottom of the condenser are being pumped into radiator (170), where it is cooled by a few degrees and flows back into the condenser, via pipe (180), at a suitable temperature.
When the water/condensate level in each tray reaches the opening of the drilled pipe (160), it flows into the tray below, and so forth. The excess water accumulates at the bottom of the condenser, where it flows out via draining pipe (195) into an intermediate vessel (200), or directly into pipes leading to the turbine.
The large number of trays (145) result in large contact surfaces between the water and the steam, thus enabling the condensation of large steam quantities. The larger the contact surface, the higher is the condensation efficiency at any give temperature.
The method of the present invention is applicable as long as the water temperature is kept equal to or lower than 100° C.

EXAMPLE

A power station that produces 1400 MW/hour produces 1100 Tons of steam per hour, i.e. about 306 Kg of steam per second.
If we choose to have a water surface of 30 m²for every Kg of steam per second, we need a total water surface of 9180 m²to condense 1100 Tons of steam per hour.
An exemplar condenser could comprise a 10 m diameter and 20 m height. 160 trays may be built, at height differences of about 12 cm, surrounding the heating pipes, each tray having a surface of 60 m², so that the total surface of the trays, which is the total water surface to be in contact with the steam, equals 9600 m².
The kinetic steam condenser of the present invention is operable in any temperature.
If the steam discharged from the power plant's turbines is at 80° C., the highest efficiency will be attained by condensing it into water at 80° C. Therefore, the steam will be heated by 3-5° C., and when the water in the trays reaches 80° C., the water temperature regulating system is operated so as to keep the water at that temperature.
Conversely, in conventional power stations using cooling condensers, the steam discharged from the turbines at approximately 80° C. and 0.46 Atm. is cooled to 30° C., a process which uses huge quantities of energy. In the example above, the power station that produces 1400 MW/hour and 1100 Tons of steam per hour would require about 160,000 m³of cooling water per hour.
The amount of heat lost in cooling 1100 Tons of steam from t₂=80° C. to t₁=30° C. is given by the formula: Q=mc(t₂-t₁), where c=1 is the specific heat of water.
Q=1,100,000×1(80−30)=55,000,000 Kcal
It is well known that the burning heat of 1 Kg petroleum is 10,000 Kcal, resulting in the cooling process requiring 5,500 Kg petroleum/hour, which amounts to 132,000 Kg/24 hours or 48,180,000 Kg petroleum/year. This is on top of the huge amount of water required for the cooling process and a significant part of the condensing heat mK, where m is the amount of steam and K is is the amount of condensing heat per 1 Kg of steam.
The majority of power stations work in less than 50% efficiency, resulting in a net saving that is essentially a double of the quantity calculated above, in the kinetic steam condenser of the present invention.
The amount of energy required for the operation of the condenser according to the present invention is approximately 550 Kg petroleum per hour, i.e. 5,500,000 Kcal/hour.
Unless otherwise defined, all technical and scientific terms used herein have the same meanings as are commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods are described herein. In addition, the methods, and examples are illustrative only and not intended to be limiting.
It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined by the appended claims and includes both combinations and sub-combinations of the various features described hereinabove as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description.

Claims

1. A method of condensing steam, the steam being in contact with a large water surface, whereby the relative temperatures of the steam and water are regulated so that the steam is kept at under-saturation pressure and the water temperature is kept at up to 100° C.

2. The method of claim 1, wherein the temperature difference between the steam and the water is kept below 10° C.

3. The method of claim 2, wherein the temperature difference between the steam and the water is kept below 5° C.

4. The method of claim 1, wherein the steam is exhaust steam from a power plant turbine and the condensate is reused as boiler feed water.

5. The method of claim 4, wherein the temperature regulation comprises heating the steam using hot gases discharged from the power plant's chimney.

6. The method of claim 1, wherein the temperature regulation comprises heating the steam using fuel burning.

7. The method of claim 1, wherein the temperature regulation comprises recycling water through cooling means.

8. A steam condenser comprising:

a steam inlet;

a water inlet;

a plurality of water receiving surfaces;

heating means for heating the steam;

control means for maintaining a predefined temperature difference between the steam and the water and for maintaining the water temperature below 100° C.; and

a condensate outlet.

9. The steam condenser of claim 8, wherein the water receiving surfaces comprise a plurality of trays, installed at various heights.

10. The steam condenser of claim 9, wherein each tray comprises a vertical bracket for holding water in the tray and a draining pipe for draining excess water into a lower tray.

11. The steam condenser of claim 8, wherein the steam heating means comprise pipes leading hot gases.

12. The steam condenser of claim 11, wherein the hot gases are gases discharged from the power plant's chimney.

13. The steam condenser of claim 11, wherein the hot gases are gases produced from burned fuel.

14. The steam condenser of claim 8, wherein the control means comprise:

means for measuring the steam temperature in the condenser; and

means for controlling the heating means accordingly.

15. The steam condenser of claim 8, wherein the control means comprise:

means for measuring the water temperature in the condenser; and

means for recycling water through cooling means.