Liquid air method and apparatus

Abstract

A method and apparatus in which air is liquefied and stored for later energy recovery during which the liquid air is pumped to high pressure, heated and then expanded to recover the energy. During the recovery of energy, the pumped liquid air is heated within a regenerator that stores the refrigeration within the liquid air. During the liquefaction of the air, part of the refrigeration required is obtained from the refrigeration stored in the regenerator.

1 . A liquid air storage and energy recovery method comprising:
 during an energy recovery phase, recovering energy from liquid air stored in a storage tank by pumping a stream of the liquid air to produce a pumped air stream, passing the pumped air stream through a regenerator such that refrigeration contained in the pumped air stream is stored within the regenerator and the pumped air stream warms within the regenerator to produce a pressurized air stream and expanding the pressurized air stream to produce power;   during a liquid air storage phase, liquefying air to produce a liquid air stream and introducing the liquid air stream into the storage tank to produce the liquid air stored in the storage tank; and   providing part of a refrigeration requirement for liquefying the air with the refrigeration stored in the regenerator, and providing another part of refrigeration by means of a liquefier.   
     
     
         2 . The liquid air storage and energy recovery method of  claim 1 , wherein:
 an air stream is compressed to produce a compressed air stream;   a first subsidiary compressed stream and a second subsidiary compressed stream are formed at least in part by dividing the compressed air stream into two portions;   the first subsidiary stream is introduced into the liquefier to produce a first cooled, high pressure air stream;   the second subsidiary stream is introduced into the regenerator to produce a second cooled high cooled high pressure air stream;   a vapor phase stream indirectly exchanges heat with the second cooled high pressure air stream to further cool the second cooled high pressure cooled high pressure air stream;   the first and second high pressure air streams are expanded and introduced into a phase separator to produce a liquid phase and a vapor phase;   the vapor phase stream is composed of the vapor phase and after the indirect exchange of the heat with the second high cooled high pressure air stream, the vapor phase stream is introduced into the liquefier and indirectly exchanges heat with the air cooling within the liquefier that forms the first cooled high pressure air stream; and   the liquid air stream is composed of the liquid phase and is expanded to a lower pressure and introduced into the storage tank;   whereby, the part of the refrigeration requirement for liquefying the air is provided by cooling the second subsidiary stream within the regenerator, indirectly exchanging heat from the second high pressure air stream to the vapor phase stream and the indirect heat exchange of the vapor phase stream within the liquefier.   
     
     
         3 . The liquid air storage and energy recovery method of  claim 2 , wherein:
 the air stream is compressed in a feed compressor along with a first recycle stream to form a first combined stream;   the first combined stream is compressed in a recycle compressor along with a second recycle stream to form a second combined stream;   the second combined stream is divided into the first subsidiary stream and the second subsidiary stream;   the first subsidiary stream is expanded at two temperature levels within the liquefier to generate first and second exhaust streams that indirectly exchange heat with the air cooling within the liquefier;   the first exhaust stream results from expansion at a lower of the two temperature levels and the second exhaust stream results from expansion at a higher of the two levels;   the first exhaust stream forms the first recycle stream after having been fully warmed within the liquefier; and   the second exhaust stream forms the second recycle stream after having been fully warmed within the liquefier.   
     
     
         4 . The method of  claim 3 , wherein the vapor phase stream after having exchanged heat with the air cooling within the liquefier is recycled back to the inlet of the feed compressor. 
     
     
         5 . The liquid air storage and energy recovery method of  claim 1 , wherein:
 the pressurized air stream is heated in a heat recuperator; and   the pressurized air stream is expanded in at least two expanders, serially connected, with re-heat within the heat recuperator between the at least two expanders.   
     
     
         6 . The liquid air storage and energy recovery method of  claim 5 , wherein:
 the pressurized air stream is heated in a heat recuperator; and   the pressurized air stream is expanded in at least two expanders, serially connected, with re-heat within the heat recuperator between the at least two expanders;   a high temperature exhaust stream is produced as a result of the expansion of the pressurized air stream;   the first combined stream is purified within a pre-purification unit; and   adsorbent within the pre-purification unit is regenerated with the high temperature exhaust stream.   
     
     
         7 . The liquid air storage and energy recovery method of  claim 1 , wherein:
 the pressurized air stream is heated within a recuperator to form a heated stream;   the heated stream is expanded in a first expander to produce a first exhaust stream;   the first exhaust stream is introduced into a combustor to produce a flue gas stream;   the flue gas stream is expanded in a second expander operating at a higher temperature than the first expander to produce a second exhaust stream; and   the second exhaust stream is introduced into the recuperator to heat the pressurized air stream.   
     
     
         8 . The liquid air storage and energy recovery method of  claim 1 , wherein:
 an air stream is compressed to produce a compressed air stream;   a first subsidiary compressed stream and a second subsidiary compressed stream are formed at least in part by dividing the compressed air stream into two portions;   the first subsidiary stream is introduced into the liquefier to produce a first cooled high pressure air stream;   the second subsidiary stream is introduced into the regenerator to produce a second cooled high pressure air stream;   the first subsidiary air stream and the second subsidiary air stream are expanded and introduced into a phase separator to produce a liquid phase and a vapor phase;   a vapor phase stream composed of the vapor phase is introduced into the liquefier and indirectly exchanges heat with the air cooling within the liquefier that forms the first cooled high pressure air stream; and   the liquid air stream is composed of the liquid phase, is expanded to a lower pressure and introduced into the storage tank;   whereby, the part of the refrigeration requirement for liquefying the air is provided by liquefying the second subsidiary stream within the regenerator and the indirect heat exchange of the vapor phase stream within the liquefier.   
     
     
         9 . The liquid air storage and energy recovery method of  claim 2 , wherein the vapor phase stream indirectly exchanges heat with the first cooled high pressure air stream and the second cooled high pressure air stream to subcool the first high pressure air stream and the second cooled high pressure air stream. 
     
     
         10 . The liquid air storage and energy recovery method of  claim 1 , wherein the pressurized air stream is expanded by introducing the pressurized air stream into a combustor and expanding resulting flue gases in an expander. 
     
     
         11 . The liquid air storage and energy recovery method of  claim 1 , wherein at least air that is introduced into the liquefier is purified of higher boiling contaminants comprising hydrocarbons, carbon dioxide and water vapor. 
     
     
         12 . The method of  claim 2  or  claim 3 , wherein the air stream is compressed to a supercritical pressure and the stream of the liquid air is pumped to a supercritical pressure. 
     
     
         13 . A regenerator comprising two or more pipe bundles, said bundles connected to each other through one or more conduits with a higher thermal resistance than the thermal resistance of each bundle as a whole so that heat will not be conducted through the one or more conduits between bundles, the pipe bundles being located within a thermal storage medium. 
     
     
         14 . The regenerator of  claim 13 , wherein the thermal storage medium is water, and the pipe bundles are submerged within a pool of the water either in solid or liquid form. 
     
     
         15 . The regenerator of  claim 13 , where each pipe bundle is embedded in a thermal storage medium, the thermal storage medium is composed of a mixture of substances that will change phase during the storage and production phases. 
     
     
         16 . The regenerator of  claim 13 , wherein the thermal storage medium is cement, gravel, ceramic, or a mineral matrix. 
     
     
         17 . A liquid air storage and energy recovery apparatus comprising:
 a storage tank for storing liquid air;   a pump connected to the storage tank to pump a stream of the liquid air during an energy recovery phase of operation, thereby to produce a pumped liquid air stream;   a regenerator connected to the pump, the regenerator configured such that refrigeration contained in the pumped liquid air stream is stored within the regenerator and the pumped liquid air stream vaporizes within the regenerator to produce a pressurized air stream;   at least one expansion device connected to the regenerator configured to expand the pressurized air stream and thereby to produce power;   a liquefier integrated with the regenerator such that during a liquid air storage phase, an air stream is liquefied to produce a liquid air stream through the refrigeration stored in the regenerator during the energy recovery phase and additional refrigeration produced by the liquefier; and   the storage tank in flow communication with the liquefier and the regenerator such that the liquid air stream is introduced into the storage tank to produce the liquid air stored in the storage tank.   
     
     
         18 . The liquid air storage and energy recovery apparatus of  claim 17 , wherein:
 at least one compressor compresses an air stream and thereby produces a compressed air stream;   the liquefier and the regenerator are in flow communication with the at least one compressor such that a first subsidiary compressed stream and a second subsidiary compressed stream are formed at least in part from the compressed air stream, the first subsidiary compressed stream is introduced into the liquefier to produce a first cooled high pressure air stream and the second subsidiary stream is introduced into the regenerator to produce a second cooled high pressure air stream;   two expansion valves are positioned between the regenerator and the liquefier and a phase separator such that the first cooled high pressure air stream and the second cooled high pressure air stream are expanded and introduced into the phase separator to produce a liquid phase and a vapor phase;   a heat exchanger is positioned between the phase separator and the liquefier and is configured such that a vapor phase stream composed of the vapor phase indirectly exchanges heat with the second cooled high pressure air stream to subcool the second cooled high pressure air stream and the vapor phase stream is introduced into the liquefier;   the liquefier is configured such that the vapor phase stream indirectly exchanges heat with the air cooling within the liquefier that forms the first cooled high pressure air stream; and   the storage tank is in flow communication with the phase separator and another expansion valve is positioned between the phase separator and the storage tank such that a liquid air stream, composed of the liquid phase, is expanded to a lower pressure and introduced into the storage tank;   whereby, the part of the refrigeration requirement for liquefying the air is provided by liquefying the second subsidiary stream within the regenerator, indirectly exchanging heat from the second cooled high pressure air stream to the vapor phase stream and the indirectly heat exchange of the vapor phase stream within the liquefier.   
     
     
         19 . The liquid air storage and energy recovery apparatus of  claim 18 , wherein:
 the at least one compressor comprises a feed compressor and a recycle compressor, the feed compressor compressing the air stream along with a first recycle stream to form a first combined stream and the recycle compressor connected to the feed compressor such that the first combined stream is compressed along with a second recycle stream to form a second combined stream;   the liquefier and the regenerator are connected to the recycle compressor so that the second combined stream is divided into the first subsidiary stream and the second subsidiary stream;   the liquefier has two expanders positioned at two temperatures levels within the liquefier such that the first subsidiary stream is expanded at two temperature levels within the liquefier to generate first and second exhaust streams, the first exhaust stream resulting from expansion at a lower of the two temperature levels and the second exhaust stream resulting from expansion at a higher of the two levels and a heat exchange network positioned within the liquefier such that the first and second exhaust streams indirectly exchange heat with the air cooling within the liquefier;   the feed compressor is connected to the liquefier so that the first exhaust stream forms the first recycle stream after having been fully warmed within the liquefier; and   the recycle compressor is connected to the liquefier so that second exhaust stream forms the second recycle stream after having been fully warmed within the liquefier.   
     
     
         20 . The liquid air storage and energy recovery apparatus of  claim 18 , wherein the liquefier is connected to the feed compressor such that the vapor phase stream is recycled back to the inlet of the feed compressor. 
     
     
         21 . The liquid air storage and energy recovery apparatus of  claim 17 , wherein:
 the at least one expansion device comprises at least two expanders, serially connected, to expand the pressurized air stream; and   a heat recuperator positioned between the at least two expanders to reheat the pressurized air stream.   
     
     
         22 . The liquid air storage and energy recovery method of  claim 21 , wherein:
 the at least two expanders produce a heated exhaust stream;   a pre-purification unit having an adsorbent purifies air of contaminants;   the pre-purification is positioned between the feed compressor and the recycle compressor so that the first combined stream is purified within the pre-purification unit; and   the pre-purification unit is connected to the at least two expanders to receive a part of the heated exhaust stream to regenerate adsorbent within the pre-purification unit.   
     
     
         23 . The liquid air storage and energy recovery apparatus of  claim 17 , wherein:
 The at least one expansion device is a first expander and a second expander;   a recuperator heats the pressurized air stream and thereby to form a heated stream;   the first expander is connected to the recuperator to expand the heated stream and thereby to produce a first exhaust stream;   a combustor is connected to the first expander to expand the first exhaust stream and thereby to produce a flue gas stream;   the second expander is connected to the combustor to expand the flue gas stream at a higher temperature than the first expander to produce a second exhaust stream; and   the recuperator is also connected to the second expander so that the second exhaust stream is introduced into the recuperator to heat the pressurized air stream.   
     
     
         24 . The liquid air storage and energy recovery apparatus of  claim 17 , wherein:
 at least one compressor compresses an air stream and thereby produces a compressed air stream;   the liquefier and the regenerator are in flow communication with the at least one compressor such that a first subsidiary compressed stream and a second subsidiary compressed stream are formed at least in part from the compressed air stream, the first subsidiary compressed stream is introduced into the liquefier to produce a first cooled high pressure air stream and the second subsidiary stream is introduced into the regenerator to produce a second cooled high pressure air stream;   two expansion valves are positioned between the regenerator and the liquefier and a phase separator such that the first cooled high pressure air stream and the second cooled high pressure air stream are expanded and introduced into the phase separator to produce a liquid phase and a vapor phase;   the liquefier is connected to the phase separator and is configured such that a vapor phase stream composed of the vapor phase indirectly exchanges heat with the air cooling within the liquefier that forms the first cooled high pressure air stream; and   the storage tank in flow communication with the phase separator and another expansion valve positioned between the phase separator and the storage tank such that a liquid air stream, composed of the liquid phase, is expanded to a lower pressure and introduced into the storage tank;   the liquid air stream is composed of the liquid phase, is expanded to a lower pressure and introduced into the storage tank;   whereby, the part of the refrigeration requirement for liquefying the air is provided by liquefying the second subsidiary stream within the regenerator and the indirect heat exchange of the vapor phase stream within the liquefier.   
     
     
         25 . The liquid air storage and energy recovery apparatus of  claim 18 , wherein the heat exchanger is also configured such that the vapor phase stream also indirectly exchanges heat with the first cooled high pressure air stream to subcool the first cooled high pressure air stream. 
     
     
         26 . The liquid air storage and energy recovery apparatus of  claim 17 , wherein a combustor is positioned between the at least one expansion device and the regenerator such that the pressurized air stream supports combustion within the combustor to generate a flue gas stream and the flue gas stream is expanded within the at least one expansion device. 
     
     
         27 . The liquid air storage and energy recovery apparatus of  claim 18 , further comprising a pre-purification unit containing molecular sieve adsorbent, the pre-purification unit is connected to the at least one compressor so that at least part of the compressed air is purified within the pre-purification unit.