Patent Publication Number: US-2016238321-A1

Title: Condenser and method of condensing vapour

Description:
The present invention relates to a condenser for condensing a vapour, and to a method of condensing a vapour, and is concerned particularly, although not exclusively, with a condenser and a method of condensing, for use with steam from a turbine. 
     Electrical power generation stations heat water to produce steam, which then drives turbines that turn a generator to generate electrical power. 
     In particular, a heat source, which may be derived from the burning of fossil fuels, is used to heat water in a boiler to produce steam at high pressure. The steam then expands through turbine stages in which the turbine is made to spin, to drive a generator. The steam reduces in pressure and loses thermal energy as it passes through the turbine stages. In one application, steam typically enters the turbine at a temperature of 400 Celsius and 4×10̂6 Pa (40 bar) pressure and leaves the turbine at a temperature of 60 Celsius and −0.9 bar pressure. Since steam cannot be pumped effectively it must be condensed back to liquid water for recirculation, in what is a closed system. Condensing of the steam is typically achieved by cooling it. Thermal energy is removed from the steam as it passes through a heat exchanger by a supply of cooling water from an external source. The considerable latent heat is dissipated and released into the cooling water to achieve the low temperatures required to condense the turbine&#39;s exhausted steam, in the presence of a vacuum. The cooling water in the heat exchanger will typically be at a temperature of around 40 Celsius, which is of very little viable or practical use. The energy in this water is therefore nearly always lost to atmosphere. The condensate, now warm boiler water, is then collected in a hot well and is directed back to the boiler via a de-aerator to be re-heated to produce steam. Purified make-up water is also introduced at this point to the cycle to replace any losses in the system. 
     Larger systems increase the temperature and pressure of steam as high as possible to increase efficiency, but at greatly elevated costs and with complications for manufacture and maintenance. 
     The need to remove thermal energy from the steam to condense it is a cause of great inefficiency, as this energy is mostly lost to the environment. 
     Embodiments of the present invention aim to address these problems. 
     The present invention is defined in the attached independent claims to which reference should now be made. Further, preferred features may be found in the sub claims appended thereto. 
     According to one aspect of the present invention, there is provided a condenser for condensing a vapour, the condenser comprising a condensing vessel having an inlet for the introduction of vapour and an outlet for the removal of liquid, wherein the condenser further comprises a rotating portion that is arranged in use to create a rotating body of liquid within the vessel. 
     The rotating portion may comprise a first impeller. 
     Alternatively, or in addition, the rotating portion may comprise a rotating inner chamber within a non-rotating outer chamber. 
     In a preferred arrangement, the condenser comprises a condensing vessel having a non-rotating outer chamber and a rotating inner chamber, the inner chamber having a first impeller. 
     The condenser may comprise a second impeller. The second impeller may be arranged in use to rotate in a contrary direction to the direction of rotation of the first impeller. 
     Preferably, in use, the vessel is arranged to form a water seal between the inner chamber and the outer chamber. 
     In a preferred arrangement the water seal is arranged to be formed in use between an annular plate portion of the inner chamber and an annular flange portion of the outer chamber. 
     The vessel may be provided with a liquid-level sensor arranged in use to sense a level of liquid in the vessel. 
     The condenser may be arranged in use to condense steam and the outlet may be arranged for the removal of water. 
     Preferably the rotating portion is arranged in use to create a rotating body of liquid that comprises a vortex having a substantially central void and may be at least partly substantially cylindrical in shape having a substantially central void. In a preferred arrangement the vapour is introduced through the inlet into the void so as to become entrained in the rotating body of liquid, into which it condenses. 
     In a preferred arrangement the inlet comprises a vortex finder preferably arranged to direct the incoming vapour to swirl in the manner of a vortex. The condenser may also comprise a vacuum pump for removal of non-condensable gases from the chamber. 
     The invention also comprises a method of condensing vapour, the method comprising introducing vapour into an inlet of a vessel and removing liquid from an outlet of a vessel, wherein the method further comprises creating a rotating body of liquid within the vessel. 
     The method may comprise a method of condensing steam. 
     Preferably the method comprises creating a rotating body of liquid comprising a vortex having a substantially central void, which body may be at least partly substantially cylindrical in shape having a substantially central void. In a preferred arrangement the method comprises introducing vapour through the inlet into the void so that the vapour becomes entrained in the rotating body of liquid, into which it condenses. 
     The invention also includes a power generation system, station or plant comprising a condenser according to any statement herein or in which vapour is condensed by a method according to any statement herein. 
     The invention may include any combination of the features or limitations disclosed herein, except such a combination of features as are mutually exclusive. 
    
    
     
       A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: 
         FIG. 1  shows, in schematic sectional view, a condenser according to a preferred embodiment of the present invention; and 
         FIG. 2  shows an alternative embodiment of condenser, in accordance with the present invention. 
     
    
    
     The apparatus, shown generally at  10 , comprises a generally cylindrical condensing vessel  12  of steel, having an upper chamber portion  12   a  and a lower chamber portion  12   b,  which have, respectively, a steam inlet  14  and a water outlet  16 . A rotating portion, in the form of an impeller  18  is driven to rotate by an electric motor  20 . Temperature gauges  22  and  24  and water pressure gauge  26  communicate with the interior of the vessel  12 , whilst a vacuum pressure gauge  28  measures the pressure of the steam entering the inlet  14 . A water level indicator  30  provides a visual indication of the level of water in the vessel  12  in use. A vacuum pump (not shown) removes non-condensable gases in use through a conduit  32  at the top of the vessel. 
     Water is drawn from the lower chamber portion  12   b  through outlet  16  by a pump  34 , which is driven by an electric motor  36 . Water from the outlet  16  is either re-circulated to the vessel through secondary inlet  38  or drawn out to a de-aerating hot well (not shown) via outlet  44 , dependent upon the condition of valve  42  which is controlled according to a detected water level in the vessel, in order to maintain a minimum level in the vessel. The hot well is connected to the boiler water supply (not shown). 
     In use, steam from the exhaust of the steam turbine is introduced into the vessel through the inlet  14 . Inside the vessel  12  is a body of rotating water, driven by the impeller  18  to form a cylindrical wall of water which follows the cylindrical walls of the vessel and is at relatively high pressure. The rotating water is represented by line A. A pressure of 2 to 6×10̂5 Pa (2 to 6 bar) should normally be adequate, but this would depend on the requirements of the system. The steam begins to swirl with the aid of a vortex finder  46  in a space formed within the rotating body of water at a much lower pressure of around 9×10̂4 Pa (0.9 bar) (this also depends on application requirements). The swirling steam is represented by line B in the drawing, and its separation from the water is exaggerated for illustration purposes. As the steam swirls, it comes into contact with the water at higher pressure where it condenses into the water. The latent energy of the steam is now held in the water and retained at pressure to be used within the system, rather than to be dissipated to atmosphere by cooling. 
     The water level is monitored and as it rises due to the condensing steam the condensate is drawn off through the outlet to the aerator/hot well from which it is recirculated to the boiler. 
       FIG. 2  shows an alternative embodiment of condenser in accordance with the invention. 
     A condensing vessel is shown generally at  100 , and comprises a stationary outer chamber  102 , and a rotating portion in the form of an inner rotating drum or chamber  104 , both of which are generally cylindrical, and arranged concentrically. The inner chamber  104  has a base  106  and a cylindrical sidewall  108  having an open top  110  around which is attached an annular plate  112 . 
     Approximately one fifth of the way down the sidewall  108  from the top  110  is a first impeller  114  which is attached to the sidewall  108 . The inner chamber  104  and impeller  114  are driven to rotate about a spindle  116  by a first motor  118 . An optional second impeller  120 , mounted on concentric spindle  122 , is driven to rotate in an opposite sense by a second motor  124 . 
     The first stationary chamber  102  surrounds the rotating chamber  104 . Annular flange  126  extends radially inwards from an inner cylindrical wall  102   a  of the chamber  102 , and extends downwardly beyond plate  112  of the inner chamber  104 , returning below the plate  112  radially outwardly towards the cylindrical wall  108  of the inner chamber. 
     A steam inlet  128  is provided to the inner chamber  104 , and a water outlet  130  is provided from the outer chamber  102 . Water level sensors  132  are provided on the outer chamber  102  to provide a control signal to a water pump (not shown). The water pump withdraws water to a de-aerator, prior to returning the water to a hot well (not shown). The pump is regulated by a three-way valve which determines how much (if any) water is returned to chamber  102  and how much is directed to the de-aerator, in dependence upon the water level in chamber  102 . 
     The condenser  100  is supported at its base on a series of legs  134 . 
     In use, steam enters the inlet  128  from an exhaust of a steam turbine (not shown). The inner chamber  104  is rotating at a speed of several thousand rpm, such as perhaps 3-4000 rpm—dependent at least upon the diameter—and contains a body of water  134  that rotates with the chamber  104  in the form of a rotating cylindrical wall of water. The first impeller  114  forces the steam down into the chamber  104  where it condenses into droplets of water and is thrown radially outwards towards the wall  108 . It condenses into liquid water at a pressure dependent upon the temperature at which the steam is to be condensed and joins the cylindrical wall of water  134  at the periphery of the chamber  104 . As more steam condenses in the chamber, water passes out of the inner chamber between the annular plate  112  and the flange  126  of the outer chamber to fall to the base of the outer chamber where it exits through  130 . Increasing the rotation speed of the inner chamber tends to increase the pressure of the water inside the chamber  104  and the rate at which the water exits the inner chamber. Uncondensed steam cannot exit the inner chamber as to do so it would first have to pass through the water to be able to enter a gap, labelled G, between the annular plate  112  and the return flange  126 . In effect the water in this gap acts as a self-regulating, high-pressure water seal. 
     The optional contra-rotating impeller  120  helps to increase the force with which the steam is urged against impeller  114 , which promotes the formation of water droplets. 
     The steam is made to condense by the high pressure in the condenser. A partial vacuum is created and maintained in the central void, whilst the latent heat released is retained and returned back to the feed water system at an elevated temperature of 90 Celsius or above. This could conceivably be much higher, depending upon practical constraints, thereby reducing the use of steam and energy to re-heat and/or to utilize it as useful heat in other applications, such as low temperature power generation, thermal refrigeration or district heating systems. 
     The thermal input-to-electrical-output efficiencies of a typical steam cycle power station range from 10% to 40%. Efficiencies in excess of 80% could conceivably be achieved by effectively utilizing the latent heat of steam otherwise lost in conventional condensing methods used at present. 
     Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features referred to herein, and/or shown in the drawings, whether or not particular emphasis has been placed thereon.