Method for liquid air and gas energy storage

Abstract

A method for liquid air and gas energy storage (LAGES) which integrates the processes of liquid air energy storage (LAES) and regasification of liquefied natural gas (LNG) at the Floating Storage, Regasification and Power (FSRP) facilities through the exchange of thermal energy between the streams of air and natural gas (NG) in their gaseous and liquid states and includes recovering a compression heat from air liquefier and low-grade waste heat of power train for LNG regasification with use of an intermediate heat carrier between the air and LNG streams and utilizing a cold thermal energy of liquid air being regasified for increase in LAGES operation efficiency through using a semi-closed CO.sub.2 bottoming cycle.

Claims

1. A method for a liquid air and gas energy storage (LACES) comprising in combination: pumping a liquefied natural gas (LNG) from an LNG storage tank of an LNG terminal into a co-located liquid air energy storage (LAES) facility and continuous re-gasifying the LNG in said LAES facility, resulting in injection of a formed send-out natural gas (NG) into gas networks; continuous consuming a required power by an air liquefier of the LAES facility and interchanging a waste thermal energy between a re-gasified LNG and a compressed air in said air liquefier, resulting in round-the-clock producing of a low-pressure (LP) liquid air from a part of said compressed air; storing at least a part of the LP liquid air from the air liquefier only in the off-peak hours in an electric grid; consuming a fuel and the LP liquid air for producing an on-demand power by a power train comprising at least one fueled and supercharged reciprocating gas engine integrated with an upstream installed high-pressure (HP) air expander and a down-stream installed low-pressure (LP) exhaust gas expander; recovering a cold thermal energy of a re-gasified liquid air for operating the LAES facility in one of the modes selected from a group comprising: re-liquefaction of a part of the send-out NG, cryogenic capture of a CO.sub.2 component from an exhaust of the power train and integration of the power train with a semi-closed CO.sub.2 bottoming cycle; and wherein the improvement comprises in combination: using at least a part of the on-demand power produced by the power train for supplying the air liquefier with the required power in the off-peak hours; using a part of the on-demand power produced by the power train for supplying the air liquefier with the required power in the on-peak and mid-peak hours; delivering a rest of the on-demand power produced by the power train to the electric grid; recovering a part of a cold thermal energy of the LP liquid air for a liquefaction of a process air in the air liquefier at a top charge cycle pressure; and recovering a cold thermal energy of a re-gasified LNG for cooling the compressed air in the air liquefier using a closed cooling loop with an intermediate cold carrier between the LNG and the compressed air.

2. The method as in claim 1, wherein production of the LP liquid air further combines the following processes in said air liquefier: pressurizing a feed air up to a bottom charge cycle pressure in a two-stage stage feed air compressor with cleaning the feed air from the atmospheric CO.sub.2 and H.sub.2O components between the stages of said feed air compressor and cooling the feed air, as the compressed air, by the intermediate cold carrier after each stage of the feed air compressor; forming a stream of the process air at the bottom charge cycle pressure as a mixture of the feed air and a recirculating air from a liquid air separator of the air liquefier; pressurizing the process air up to a top charge cycle pressure in a two-stage process air compressor with cooling the process air, as the compressed air, by the intermediate cold carrier after each stage of said process air compressor; cooling the process air in a second heat exchanger by the LNG from a first heat exchanger and subsequent said liquefaction of the process air at the top charge cycle pressure through recovering a part of the cold thermal energy of the LP liquid air; further cooling a liquid process air in the first heat exchanger by the LNG from the LNG storage tank; final cooling the liquid process air by the recirculating air from the liquid air separator; depressurizing the liquid process air in a liquid air expander, resulting in formation of a deeply cooled two-phase process air at a bottom charge cycle temperature and the bottom charge cycle pressure; separating said deeply cooled two-phase process air in the liquid air separator, resulting in formation of the outgoing streams of a liquid air and the recirculating air at the bottom charge cycle pressure; pressurizing the liquid air from the liquid air separator up to the LP and recovering a part of the cold thermal energy of the LP liquid air for said liquefaction of the process air; delivering the LP liquid air in the off-peak hours from the air liquefier both into a storage tank and into the power train of the LASS facility; and delivering the LP liquid air both from the air liquefier and from the storage tank into the power train of the LAES facility in the on-peak and mid-peak hours.

3. The method as in claim 2, wherein cooling the compressed air in the air liquefier comprises the following processes: using a compressed air cooler installed after each stage of the feed and process air compressors as a device for transferring a compression heat from the compressed air to the intermediate cold carrier; collecting the compression heat by the streams of the intermediate cold carrier passing through a set of said compressed air coolers installed in parallel at the outlet of an intermediate cold carrier pump; pooling all said steams of the intermediate cold carrier at the outlet of the compressed air coolers, resulting in forming the closed cooling loop; collecting a low-grade waste heat of at least one fueled and supercharged reciprocating gas engine by a pooled stream of the intermediate cold carrier passing through a main cooler of the said gas engine; and re-gasifying the LNG from the second heat exchanger through recovering a heat collected by the intermediate cold carrier in the compressed air coolers and the main cooler of the gas engine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments will hereinafter be described in detail below with reference to the accompanying drawings, wherein lie reference numerals represent like elements. The accompanying drawings have not necessarily been drawn to scale. Where applicable, some features may not be illustrated to assist in the description of underlying features.

(2) FIG. 1 is a schematic view of the first embodiment of the LAGES facility which may be designed for production of a liquid air in the air liquefier train, according to the invented method.

(3) FIG. 2 is a schematic view of the second embodiment of the LAGES facility which may be designed for operation of power block with use of produced liquid air.

(4) FIG. 3 is a diagram showing a fuel-to-power conversion efficiency of the LAGES facility vs. a number of its operation hours daily used for liquid air production only, according to the invented method.

DETAILED DESCRIPTION OF THE INVENTION

(5) The practical realization of the proposed method for liquid air and gas energy storage (LAGES) may be performed through the integration between the LNGSR terminal and LAES system into combined LAGES facility. At such facility the interchanging of a waste thermal energy between the LNG being regasified and the process air being liquefied and regasified provide a drastic increase in performance of the LAES system and a marked decrease in the LAGES capital costs. The invented method may be especially promising for design of the Floating LNGSR units integrated with the barge-mounted Power Generation units, making such integrated facility capable to highly efficient operate both in the base-load and load-following modes.

(6) The FIG. 1 is a schematic view of the air liquefier of the LAGES facility designed for continuous production of liquid air. A power required for driving the compressors of air liquefier is produced by one of the turbocharged reciprocating engine 1 installed in the power block of facility and supplied with fuel 2. During off-peak hours a charging of the gas engine with combustion air is performed by the standard turbocharger 3, whereas during mid and on-peak hours a regasified liquid air 4 delivered from the power block is used for this purpose. In its turn, exhaust gases 5 are directed to power block, wherein their energy is used to perform an additional work.

(7) The LNG stream is continuously delivered from the storage 6 by the LP and HP pumps 7 and 8 into air liquefier of the LAGES facility, wherein it is initially heated in the first air-to-LNG heat exchanger 9 by a stream of highly pressurized liquefied process air and thereafter in the second air-to-LNG heat exchanger 10 by a stream of highly pressurized process air. The further evaporation and final reheating of LNG is going in the LNG regasifier 11 at the expense of heat transfer with an intermediate heat carrier. The regasified LNG is injected into pipeline 12 of gas network.

(8) The atmospheric feed air 13 is pressurized in the first stage 14 of feed air compressor, cooled in the first feed air cooler 15, dried and freed from atmospheric CO.sub.2 contaminants in the adsorber 16, additionally cooled in the second feed air cooler 17, pressurized in the second compressor stage 18 up to a bottom charge cycle pressure and aftercooled in the third feed air cooler 19.

(9) At the inlet of process air compressor 20 the pressurized and aftercooled feed air is mixed with the boil-off air 21 recirculating from the air separator at the same bottom charge cycle pressure. The process air, as a mixture of feed and boil-off air streams, is pressurized in the first stage 20 of process air compressor, intercooled in the first process air cooler 21, further pressurized in the second compressor stage 22 up to a top charge cycle pressure and aftercooled in the second process air cooler 23.

(10) Further deep cooling a highly pressurized process air is performed in the said second air-to-LNG heat exchanger 10 by the LNG stream, after which the air is liquefied in the process air liquefier 24 through its cooling by a stream of liquid air escaping the air separator. A temperature of the pressurized liquefied process air is additionally reduced in two heat exchangers installed in tandem: in the said first air-to-LNG heat exchanger 9 by the LNG stream and in the air-to-air heat exchanger 25 by the recirculating stream of boil-off air escaping the air separator. The following depressurizing the liquefied process air in the liquid air expander 26 leads to formation of deeply cooled two-phase process air escaping the said expander at a bottom charge cycle temperature and a bottom charge cycle pressure.

(11) The liquid and boil-off phases of process air are separated in the separator 27 with a said recirculation of boil-off air stream through heat exchanger 25 into inlet of process air compressor 20. In its turn, a pressure of liquid air stream escaping a separator is increased by a pump 28 up to a low value required for its following storage or direct use in the power block, after which this stream is directed to air liquefier 24, wherein a part of its cold thermal energy is used for the said liquefying a process air. The LP liquid air escaping the liquefier 24 is directed through a control valve 29 into a liquid air storage 30 during off-peak hours or to the power block for production of on-demand power over the mid-peak and on-peak hours.

(12) Collection of compression heat and its recovery for LNG regasification is performed with use of intermediate heat carrier circulating in the closed loop and directed by the pump 31 through a set of said air coolers 15, 17, 19, 21 and 23 placed in parallel at the outlet of said pump. To reach a temperature required for injection of regasified LNG into NG network, a pooled stream of the intermediate heat carrier streams escaped the said air coolers is additionally heated in the heat exchanger 32 by a low-grade waste heat extracted from the cooling system of the gas engine 1 being used for driving the compressors of air liquefier. In the said LNG regasifier 11 the collected compression heat of air liquefier and low-grade heat of gas engine cooling system are transferred from an intermediate heat carrier to the LNG, resulting in its regasification and superheating.

(13) The described above mode of air liquefier operation is applied to storage of excessive power produced by the BMPP facility integrated with SRGU. However the invented method may be also adapted to storage of excessive energy in the grid. For this purposes, an excessive power from the grid is consumed during off-peak hours for driving the compressors of air liquefier, whereas a gas engine 1 is taken out of service for this time-period and is put into operation during mid and on-peak hours. A low-grade waste heat of its cooling system is accumulated in this time interval and used in the heat exchanger 32 for an additional heating of the intermediate heat carrier during off-peak hours.

(14) The improvements in operation of the power block of the LAGES facility are not subject of the present invention. Because of this its schematic view in the FIG. 2 is shown only for illustration of the possible methods for its operation developed and described previously in the U.S. patent application Ser. No. 16/109,884, published U.S. Patent Application No. US 20180221807 and provisional U.S. Patent Application No. 62/554,053. By and large a power block of any LAESfacility comprises a system 33 intended for regasification of discharged liquid air with recovery of its cold thermal energy and one or several power trains intended for harnessing the regasified discharged air in the power generation processes. The designer can select any configuration and method of operation for the system 33 from among the described in the mentioned patent applications using a power train configuration identical for all applications. During mid-peak hours the discharged liquid air is delivered into this system by high-pressure pump 34 directly from air liquefier via pipe 35, whereas during on-peak hours the discharged liquid air stream from the storage 30 is added via pipe 36 to total amount of liquid air consumed by the system 33.

(15) In the FIG. 2 a power block is exemplified by two power trains 37 and 38. Both trains have an identical configuration, making possible to charge their gas engines with combustion air via pipe 4 without use of the turbochargers during on-peak and mid-peak hours. At the same time a gas engine 1 of the train 37 is additionally equipped with a standard turbocharger 3 (see FIG. 1), providing its operation during off-peak hours. The regasified air escaping the system 33 via pipe 39 at the top discharge cycle pressure is delivered into hot recuperator 40, wherein a thermal energy of exhaust gases escaping the train 37 is used for superheating the delivered discharged air. The following expansion of this air in the high-pressure expander 41 leads to reduction in its pressure down to an intermediate level, at which it is delivered into reciprocating engine 1 via pipe 4. Here the delivered air is used for combustion of fuel supplied via pipe 2. The exhaust gases escaping the engine 1 via pipe 5 at the enhanced pressure and temperature are additionally heated in the duct burner 42 and directed to the inlet of low-pressure expander 43. Here their pressure is reduced down to a practically atmospheric level, whereas outlet temperature is high enough for said superheating the regasified air in hot recuperator 40. A total power produced by the HP expander, gas engine and LP expander is delivered into grid during mid-peak and on-peak hours. The exhaust gases are removed to atmosphere via pipe 44 or optionally subjected to cryogenic treatment in the system 33.

INDUSTRIAL APPLICABILITY

(16) The performances of liquid air and gas energy storage (LAGES) facility using the proposed method of operation are tabulated below for the case of a possible send-out capacity of FSRU at a level of 0.5 MTPA. At such LAGES facility production of a liquid air in the LAESsystem is performed during 24 h per day and on condition that relationship between the flow-rates of LNG (pure methane) and liquid air streams is equal to 1.1:1. The production of power in the LAESsystem may be also performed both in the base-load operation mode during 24 h/d and in the load-following regime. In the las case the durations of off-peak and on-peak hours have been selected identical, but may be varied from 0 to 12 hours per day with operation during rest of daily hours in mid-peak regime. At the duration equal to 0 h/d, the LAGES facility is operated in base-load mode. For each operation mode a sought value of facility fuel-to-power conversion efficiency is determined.

(17) In calculation performed the top charge cycle pressure of process air stream and the top discharge cycle pressure of pumped liquid air stream are set at a level of 67 barA and 140 barA correspondingly. The power block of the LAESsystem comprises a set of two power trains with reciprocating gas engines and expanders. The first engine operated continuously is equipped with the standard turbocharger being used only during off-peak hours at 65% of engine nominal output. The second engine is operated only during on-peak hours. A charging of the reciprocating engines with combustion air is performed at a pressure of 4 barA, whereas the discharging of exhaust gases is performed at a pressure of 3.5 barA and a temperature of 570 C. The mentioned temperature of engine exhaust gases and an amount of fuel combusted in the duct burner of the power train provide the maximum admissible temperatures of 540 C. and 760 C. for regasified air at the inlets of the modified steam turbine being used as HP expander and power turbine being used as LP expander. The general data of equipment installed in the Air Liquefier (AL) train and Power Production (PP) train are listed in Table 1.

(18) For regasification of discharged liquid air with recovery of its cold thermal energy a system providing integration of the power trains with the semi-closed CO.sub.2 bottoming cycle has been selected, because such system makes possible to reach a highest level of fuel efficiency of the LAGES facility. As an intermediate heat carrier in the air liquefier the propane has been selected. The main results of performed calculations are presented in the Tables 2.-4 They have clearly demonstrated a very high daily fuel efficiency of the LAGES facility which is equal to 59.7% during facility operation in base-load regime and 57.3-58.8% during its operation in load-following regime with storage of excessive power produced by facility.

(19) TABLE-US-00001 TABLE 1 POWER CONSUMED by AL TRAIN POWER PRODUCED by 1 PP TRAIN LP Feed air compressor kWe 1,176 Gas engine kWe 9,730 HP Feed air compressor kWe 1,486 LP exhaust expander kWe 4,579 LP Main air compressor kWe 1,796 HP air/CO2 expander kWe 8,597 HP Main air compressor kWe 1,957 HP liquid air pump kWe 357 Liquid air expander kWe 122 Bypass mix expander kWe 38 LP Liquid air pump kWe 15 CO2 liquid pump kWe 63 Propane pump kWe 12 Total discharge power kWe 22,524 Total charge power kWe 6,319 GAS ENGINE and DUCT BURNER DATA LNG REGASIFIED & AIR LIQUEFID DATA Type of prime mover GE Gas LNG mass flow-rate kg/s 16.5 engine NG send-out pressure bara 80 GE charge air flow-rate kg/s 15.1 NG send-out temperature C. 10 GE charge air pressure barA 3.9 LAIR mass flow-rate kg/s 15.1 GE nominal power kWe 9,730 LAIR storage pressure barA 12 Efficiency at 100% SMCR % 46.3 LAIR high pressure barA 140 Heat input with fuel in GE kWth 21,015 Propane low temperature C. 74 Heat input with fuel in DB kWth 3,618 Propane high temperature C. 29 Total heat input kWth 24,633

(20) TABLE-US-00002 TABLE 2 Parameters Unit Alternative 1 Alternative 2 Facility operation mode Base-load Load-following Facility train in operation AL + PP AL AL + PP Duration h/d 24 12 12 Load of GE with cold TCH SMCR 1 100% 2 100% Load of GE with standard SMCR 1 65% TCH Total power produced MWe 22.5 45.0 Power self-consumed MWe 6.3 6.3 6.3 Power delivered to grid MWe 16.2 38.7 Heat input with fuel MWth 27.1 13.4 54.2 Plant fuel efficiency % 59.7 57.3

(21) TABLE-US-00003 TABLE 3 Parameters Unit Alternative 3 Facility operation mode Load-following Facility train in operation AL AL + PP Duration h/d 8 8 8 Load of GE with cold TCH SMCR 1 100% 2 100% Load of GE with standard SMCR 1 65% TCH Total power produced MWe 22.5 45.0 Power self-consumed MWe 6.3 6.3 6.3 Power delivered to grid MWe 16.2 38.7 Heat input with fuel MWth 13.4 27.1 54.2 Plant fuel efficiency % 58.0

(22) TABLE-US-00004 TABLE 4 Parameters Unit Alternative 4 Facility operation mode Load-following Facility train in operation AL AL + PP Duration h/d 4 16 4 Load of GE with cold TCH SMCR 1 100% 2 100% Load of GE with standard SMCR 1 65% TCH Total power produced MWe 22.5 45.0 Power self-consumed MWe 6.3 6.3 6.3 Power delivered to grid MWe 16.2 38.7 Heat input with fuel MWth 13.4 27.1 54.2 Plant fuel efficiency % 58.8

(23) It should be noted that the term comprising does not exclude other elements or steps and a or an do not exclude a plurality. It should also be noted that reference signs in the claims should not apparent to one of skill in the art that many changes and modifications can be effected to the above embodiments while remaining within the spirit and scope of the present invention. For example, the invented method may be applied to design and operation of the near-shore Floating Storage, Regasification and Power Units (FSRPU) connected with the national electric and natural gas networks and intended for storage of excessive grid power.