Method and apparatus for separating air by cryogenic distillation

Abstract

In a method for separating air by cryogenic distillation, in response to the requirement of reducing power consumption, at least a portion of the power required by the method is provided by at least one electrochemical energy storage device (A) so as to enable a rapid reduction in the power consumed by the method obtained from the power grid (R).

Description

[0001] This invention relates to a method and apparatus for separating air by cryogenic distillation.

[0002] Equipment used to separate air through cryogenic distillation provides a large amount of high-voltage and / or medium-voltage electricity to the motors of air compressors and, possibly, product compressors.

[0003] WO 2012056245 describes a method for operating a power plant supplying an air separator, wherein the power sent to the compressor of the air separator varies according to the power demand on the grid. This document specifies the application of load shedding to the air separator when the power demand on the grid is high.

[0004] Load shedding refers to cutting off the power supply to equipment connected to the power grid in order to reduce the total load on the grid. Load shedding can consist of completely cutting off the power supply to the equipment or reducing its consumption; the latter is called partial load shedding.

[0005] Known practices include supplying power to air separation equipment from power plants or nuclear power plants.

[0006] To cope with fluctuating electricity demand, aggregators may ask customers to reduce their consumption. In situations of imbalance between electricity supply and demand, load shedding involves temporarily reducing actual consumption at a given location (relative to its "normal" consumption). Load shedding is triggered by external stimuli, typically during peak daily or seasonal electricity consumption periods. It can simply eliminate electricity demand or, in extreme cases, prevent power supply disruptions.

[0007] This invention relates to a method for separating air by cryogenic distillation, which can rapidly reduce its power consumption from the power grid.

[0008] To date, the use of accumulators to supply power to the motor of the main compressor of such a device is unprecedented.

[0009] The purpose of this invention is not to reduce the maximum power consumption of the separation equipment. Nor is it necessarily to consume less power when electricity is expensive (as this can be achieved with lower investment without the need for an energy storage device).

[0010] The main purpose of this invention is to provide services to the power grid by rapidly (within seconds) reducing load when power production capacity is insufficient.

[0011] When electricity consumption exceeds production, there are three types of reserves to deal with the situation: Level 1, Level 2, and Level 3 reserves.

[0012] In fact, for the secondary reserve (automatically activated by the grid manager) and the tertiary reserve (manually activated by the air separation equipment operator upon receiving a phone call from the grid manager), this invention enables the rapid reduction of the power required by the separation equipment at critical moments (due to the use of an energy storage device that allows power regulation within a time period ranging from 2 to 15 minutes).

[0013] Return on investment is based on the service provided to the power grid (in terms of...) / rapid reduction in MW), rather than based on electricity cost (unit: / MW h ).

[0014] The known practice is to store electricity in electrochemical accumulators, like batteries, by converting it into electrochemical energy. However, storing electricity in electrochemical accumulators is much more expensive than reducing the power consumption of air separation equipment. On the other hand, the reaction time of electrochemical accumulators is much faster (a few seconds) than that of air separation equipment.

[0015] This invention relates to a method for separating air by cryogenic distillation, wherein the power consumption from the power grid can be reduced by using an electrochemical energy storage system such as an electrochemical accumulator. This method enables a faster reduction in the power consumption of the air separation equipment. The method preferably uses at least one cryogenic liquid storage device, which can be an air storage device, a liquid oxygen storage device, or a liquid nitrogen storage device.

[0016] This concept can easily be extended to the liquefaction of cryogenic fluids (O2, N2, Ar, CH4, CO, H2, He, CO2, etc.) or other types of separation by distillation.

[0017] The electricity supplied to the air-gas separation equipment can be used for three purposes:

[0018] ●Oxygen / nitrogen and possibly argon separation.

[0019] ●In contrast to condensing air under high pressure, the product is compressed internally by evaporation of oxygen and / or nitrogen and / or argon under high pressure and / or externally by using an oxygen and / or nitrogen and / or argon compressor.

[0020] ●Liquefy air gases such as oxygen and / or nitrogen and / or argon using integrated air circulation or external nitrogen circulation.

[0021] To reduce the power consumption of the pump, this invention proposes, in addition to using at least one accumulator, the use of a liquid oxygen storage device and a liquid air or possibly liquid nitrogen storage device, as described in FR 2924203 and FR 3066809. Figure 5 of FR 3066809 depicts a configuration where liquid oxygen is stored in a storage device upstream of the pump and liquefied air is stored in a liquefied air storage device.

[0022] To reduce internal compression power, this invention proposes, in addition to using at least one accumulator, a thermal storage device consisting of an inexpensive medium (e.g., quartz sand, iron ore pellets, or encapsulated solid and / or liquid water) with high heat capacity by mass and / or volume. More expensive but more efficient devices can also be used, as they are based on liquid-solid phase change of pure substances or mixtures. WO 2010 / 093400 lists many molecules that can be used as phase change materials.

[0023] To reduce liquefied electricity, the present invention proposes, in addition to using at least one accumulator, to reduce or stop air compression associated with air circulation and / or reduce or stop nitrogen compression associated with nitrogen circulation.

[0024] This method of unloading in the air-gas separation unit enables rapid changes in power consumption:

[0025] ●Regarding reductions (e.g., in response to grid managers' requirements to balance supply and demand: Level 1, Level 2, or Level 3 reserves), such as using batteries to supply energy to the unit, rapidly reducing the power consumed by the unit from the grid's perspective, the reduction in the unit's power consumption is slower compared to the combined power consumed by the battery and the unit.

[0026] ● Regarding increases, for example, using batteries to store electricity can rapidly increase the power consumed by the unit from the perspective of the power grid. Compared to the combined power stored by the battery and the unit, the increase in the unit's power consumption is slower.

[0027] Therefore, it is possible to have a system with two consumption levels that can operate rapidly on changing gradients.

[0028] WO 2015 / 003809 describes a method for separating air by cryogenic distillation, but does not propose a solution for minimizing the increase in power consumption from the grid when operating with increased consumption.

[0029] According to one aspect, the subject of the invention is a method for separating air by cryogenic distillation, wherein, during a first operation, a first flow rate of air is compressed in at least one compressor, cooled, and separated in a column system to produce a first flow rate of a first distillation product, and the high-pressure or medium-pressure power requirements of the one or more compressors of the method are met by the power grid; during a second operation, a second flow rate of air, lower than the first flow rate, is compressed in the at least one compressor, the second flow rate is cooled, and separated in the column system to produce a first distillation product, lower than the first flow rate of the first product, from the column system; the high-pressure or medium-pressure power requirements of the compressors are lower than during the first operation; and during an intermediate operation following the first operation and preceding the second operation, the power consumption of the one or more compressors from the power grid is lower than the power consumption during the first operation and greater than or equal to the power consumption during the second operation; characterized in that, during the intermediate operation, at least a portion of the power requirements of the method operating during the intermediate operation is met by at least one electrochemical accumulator.

[0030] According to other optional aspects:

[0031] ● During intermediate operation, the method reduces high-voltage and / or medium-voltage power consumption, preferably once the supply from the energy storage unit begins;

[0032] ● During the first and second runs, at least one electrochemical accumulator does not supply medium- and / or high-voltage power to the method;

[0033] ● At the end of the intermediate operation, at least one electrochemical accumulator will no longer supply medium- and / or high-voltage power to the method;

[0034] ● The electrochemical energy storage device supplies the method with a decreasing amount of electricity over time during intermediate operation;

[0035] ●The power grid supplies this method with electricity that decreases over time during the intermediate operation period;

[0036] ● The amount of electricity supplied by the power grid during the intermediate operation period is equal to the amount of electricity supplied during the second operation period;

[0037] ● The difference between the power consumption of the air separation method in the first operation and the power consumption in the second operation is X MW, where X is a number greater than zero and the maximum power supplied during the intermediate operation is at least 0.9X MW, preferably at least X MW;

[0038] ● At least one electrochemical energy storage device and one or more compressors of the method are powered by the same power grid;

[0039] ● Charge the electrochemical energy storage device when the electricity price is below a threshold and / or when the power consumption is below a threshold and / or at night;

[0040] ● In cases where the amount of electricity available on the power grid decreases, at least a portion of the power demand of this method is met by an electrochemical energy storage device;

[0041] ●The method includes the step of pressurizing purified air in a motor-driven booster, the pressurized air being used to evaporate distilled liquid products, wherein the pressurized flow rate is the same in at least two of three runs;

[0042] ●The method includes the step of stopping the pressurization of air; the total air flow rate is reduced (to between 20% and 30% of the air due to the reduction of the air booster), but the flow rate of the column operating at higher pressure remains relatively constant;

[0043] ●During the first operation, liquefied air and / or liquid products from the air separation unit are stored;

[0044] ●During the second run and / or intermediate run, liquefied air is delivered from the storage unit to the separation unit;

[0045] ●Liquid products from the storage unit are evaporated during the second run and / or during intermediate runs to supply gaseous products;

[0046] ● During the initial operation and / or intermediate operation, liquefied air was not delivered from the storage unit to the separation unit;

[0047] ●Liquid products from the storage unit were not evaporated during the first run to supply gaseous products;

[0048] ● During intermediate operation, the amount of liquefied air delivered from the storage unit to the separation unit increases;

[0049] ● The amount of liquid product evaporated from the storage unit is increased during intermediate operation to supply gaseous products;

[0050] ● The first flow of air is compressed to a pressure of at least 5 bar in at least one compressor (C);

[0051] ●Only during the intermediate operation period, which takes place after the first operation and before the second operation, at least a portion of the power demand of the method operating during the intermediate operation period is met by at least one electrochemical energy storage device;

[0052] ● The power requirements of the method for operation during the first and / or second run are not met by at least one electrochemical energy storage device;

[0053] ●If a load shedding request is received from the control unit of an electricity production and consumption system that supplies electricity to multiple consumers, electricity is sent to the method through at least one energy storage device.

[0054] According to another aspect, the subject of the invention is an apparatus for separating air by cryogenic distillation, comprising at least one compressor for compressing air, means for cooling and purifying the compressed air, a column system including at least one air distillation column for separating air into oxygen and nitrogen, an electric motor for driving at least one of the at least one compressor, means for supplying high-voltage and / or medium-voltage power from the power grid to the motor, at least one electrochemical accumulator, means for supplying high-voltage and / or medium-voltage power from the at least one accumulator to the motor, means for interrupting the power supply from the power grid to the motor and means for interrupting the power supply from the at least one accumulator to the motor, means for interrupting the power supply controlled by a control system, means for sending a first flow rate of air to be compressed in at least one compressor during a first operation, means for sending a second flow rate of air to be compressed in at least one compressor at a lower flow rate during a second operation, and means for connecting at least one accumulator to the motor in response to a load reduction request signal during an intermediate operation after the first operation and before the second operation.

[0055] Therefore, in response to a load reduction requirement (preferably from a control unit), the device includes means for connecting at least one energy storage unit to the motor, such that the motor is partially powered by the at least one energy storage unit and partially powered by the grid (partial load reduction) at least during intermediate operation, or otherwise fully powered by the at least one energy storage unit.

[0056] The device may include means for interrupting the transmission of power from at least one energy storage unit to the motor after a given time and / or according to a signal from the control unit.

[0057] Preferably, the apparatus includes a device connected to the column system for supplying distillation products and at least one cryogenic liquid storage device connected to these devices. This allows for consistent production even when the column system receives less air.

[0058] The invention will be described in more detail with reference to the accompanying drawings.

[0059] [ Figure 1 The evolution of various features of the method over time is illustrated graphically:

[0060] a) shows the power transmitted from the grid to the air separation device over time;

[0061] b) shows the power transmitted from at least one energy storage device to an air separation device over time;

[0062] c) shows the power consumption of one or more compressors in the air separation device over time;

[0063] d) shows the oxygen flow rate over time.

[0064] [ Figure 2 An air separation device according to the present invention is shown.

[0065] [ Figure 1 The diagram illustrates variable parameters for an apparatus used to separate air via cryogenic distillation. This apparatus forms part of a plurality of consumer units connected to an electricity production and consumption system that supplies electricity to multiple consumers. This power grid R includes a control unit adapted to send modulation commands and, in particular, load shedding commands to the consuming units, including the air separation equipment.

[0066] These load reduction commands can be sent via any suitable means, such as physical media (PLC, radio, ADSL) or via the Internet.

[0067] For example in [ Figure 1 As can be seen from a), during the first operation, the power grid R sends a first electrical charge H to the equipment used to separate air through cryogenic distillation. ASU This electricity is primarily used to operate one or more motors of one or more compressors in the equipment, whether it is the main air compressor, air booster, or product compressor. During intermediate operation, the power grid sends a smaller amount of electricity (amount B) to the air separation equipment. ASU ).

[0068] At the moment t0 of power supply decline [ Figure 1 b) Turn on the storage device to supply the missing power to the separation equipment that is still operating at maximum productivity.

[0069] During the intermediate operation between the first and second operation, at least a portion of the power demand of the method is met by at least one electrochemical energy storage device A, and the power consumption from the grid is lower than the power consumption during the first operation and greater than or equal to the power consumption during the second operation.

[0070] Therefore, even after the power supply from the grid decreased, the air separation unit was still supplied with the same amount of electricity as during the first operation.

[0071] Energy storage device A operates during the intermediate operation period, with a continuous air separation method adapting to the time spent reducing power from the grid. During this intermediate operation period, the power generation from at least one energy storage device A decreases regularly, reaching zero at time t1 at the end of the intermediate operation.

[0072] During the intermediate operation period, the power generation from the grid R is at a low value B corresponding to the power generation during the second operation. Figure 1 ] a)).

[0073] For example in [ Figure 1 As can be seen in c), the consumption of the air separation method decreases during the intermediate operation, but only begins to decrease after the supply from the accumulator is in place, thus after t0.

[0074] The consumption of the air separation method decreases to a low value B during intermediate operation. ASU And the compression flow rate of the main air compressor decreases simultaneously, resulting in less power consumption by the motor. If the method includes a step of pressurizing the feed air, which is used to compress air to evaporate the distilled liquid product, such as oxygen, the air booster can have a constant flow rate in at least two of the following operations: the first operation, the second operation, and the intermediate operation. Therefore, in this case, the oxygen production d) evaporated by the pressurized air does not change. At least some of the oxygen can be supplied by a liquid oxygen storage device supplied by the column of the separation unit. Therefore, as in [ Figure 1 As can be seen from d), the total oxygen production OG remains unchanged, and the oxygen shortage from the column production is supplied by the liquid oxygen storage device.

[0075] If customers can tolerate a decrease in flow rate, oxygen production can also be allowed to vary between t1 and t2 or between t0 and t3.

[0076] Preferably, the purified air booster is driven by an electric motor.

[0077] It is also possible to reduce the amount of electricity supplied by the grid during intermediate operation, but not immediately reduce it to value B. ASU For example, the amount of electricity supplied to equipment by the power grid can immediately drop to H. ASU With B ASU The intermediate value between, or the value that can decrease regularly from T0, as long as it reaches value B at t1. ASU .

[0078] During intermediate operation, the method reduces high-voltage and / or medium-voltage power consumption, preferably once the supply from the energy storage unit begins.

[0079] When the accumulator is no longer generating electricity, the method operates at a low productivity and may produce less product. In this case, the power consumption of the method decreases before the yield declines due to the time required for distillation.

[0080] The second run begins at time t1. During the second run, a second flow of air, at a lower flow rate than the first flow rate, is compressed in the compressor. The second flow rate is cooled and separated to produce a first distillation product at a second flow rate (possibly lower than the first flow rate of the first product). The high-pressure or medium-pressure power requirement is lower than during the first run.

[0081] At time t2, the power grid generates the initial amount of electricity H again. The energy storage device begins charging at or after t2 and ends charging at t3. During this charging period, the air separation device increases its power consumption, reaching value H at t3. ASU .

[0082] Once the accumulator is charged at t3, the energy consumption of the separation device will once again be at H. ASU While the energy storage device is charging, grid production remains unchanged.

[0083] During the first and second runs, or optionally during the first or second runs, at least one electrochemical accumulator does not supply medium- and / or high-voltage power to the method.

[0084] At the end of the intermediate operation, at least one electrochemical accumulator ceases to supply medium- and / or high-voltage power to the method.

[0085] Electrochemical energy storage supplies a decrease in electrical energy over time during intermediate operation.

[0086] The difference between the power consumption of the air separation method in the first operation and the power consumption in the second operation is X MW, where X is a number greater than zero and the maximum power supplied during the intermediate operation is at least 0.9X MW, preferably at least X MW.

[0087] At least one electrochemical energy storage device and one or more compressors of the method are powered by the same power grid.

[0088] Preferably, the electrochemical energy storage device is charged when the electricity price is below a threshold and / or when the power consumption is below a threshold and / or at night.

[0089] In the event of reduced available electricity on the grid, at least a portion of the power demand of this method is met by an electrochemical energy storage device.

[0090] The energy storage device does not necessarily have to be located in the same place as the air separation device. This invention can also realize several energy storage devices and several air separation devices located in different locations but electrically connected to the same power grid.

[0091] The invention can also be implemented to improve the balance between the consumption of one or more air separation units and the production of one or more intermittent renewable power generation facilities (such as wind or solar power facilities) at any time.

[0092] According to variations, the method uses a liquefied air storage device and / or a liquefied product storage device. During the initial operation, liquefied air and / or liquid products from the air separation unit can be stored.

[0093] Depending on the requirements of the method, use at least one of the following method steps:

[0094] ●During the second run and / or intermediate run, liquefied air is delivered from the storage unit to the separation unit;

[0095] ●Liquid products from the storage unit are evaporated during the second run and / or during intermediate runs to supply gaseous products;

[0096] ● During the initial operation and / or intermediate operation, liquefied air was not delivered from the storage unit to the separation unit;

[0097] ●Liquid products from the storage unit were not evaporated during the first run to supply gaseous products;

[0098] ● During intermediate operation, the amount of liquefied air delivered from the storage unit to the separation unit increases;

[0099] ● The amount of liquid product evaporated from the storage unit is increased during intermediate operation to supply gaseous products;

[0100] ● The first flow of air is compressed in at least one compressor (C);

[0101] ● The first flow of air is compressed to a pressure of at least 5 bar in at least one compressor (C).

[0102] The equipment includes means for delivering a first flow rate of air to be compressed in at least one compressor during initial operation, and means for delivering a second flow rate of air, lower than the first flow rate, to be compressed in at least one compressor during a second operation. These means consist of piping and regulating devices.

[0103] The device also includes means for connecting at least one accumulator to the motor in response to a load reduction request signal during intermediate operation after the first operation and before the second operation.

[0104] The device is connected, for example, to a control unit that sends a load reduction request signal to instruct the air separation device to reduce its power consumption from the grid.

[0105] In response to a load reduction requirement (preferably from a control unit), the device allows power to be sent from at least one energy storage device to the motor, such that the motor is partially powered by at least one energy storage device and partially powered by the grid (partial load reduction) at least during intermediate operation, or otherwise fully powered by at least one energy storage device.

[0106] It also provides means for interrupting the power transmission from at least one accumulator to the motor after a given time and / or according to another signal from the control unit.

[0107] [ Figure 2 An air separation apparatus according to the present invention is shown. The apparatus for separating air by cryogenic distillation includes at least one compressor C for compressing air to a pressure of at least 5 bar, a device ER for cooling and purifying the compressed air, a column system K including at least one air distillation column for separating air into oxygen (OG) and nitrogen, an electric motor M for driving at least one of the at least one compressor, a device for supplying high-voltage and / or medium-voltage electricity from a power grid R to the motor, at least one electrochemical accumulator A, a device for supplying high-voltage and / or medium-voltage electricity from the at least one accumulator to the motor, a device for interrupting the power supply from the power grid to the motor and a device for interrupting the power supply from the at least one accumulator to the motor, and a device controlled by a control system S for interrupting the power supply. This control system may be a power grid control unit.

Claims

1. A method for separating air by cryogenic distillation, wherein, During the first operation, a first flow rate of air is compressed in at least one compressor (C), cooled, and separated in a column system to produce a first flow rate (OG) of first distilled product. The high-pressure or medium-pressure power requirement of the one or more compressors of the method is met by the power grid (R). During the second operation, a second flow rate of air, lower than the first flow rate, is compressed in the at least one compressor, cooled, and separated in the column system to produce a second flow rate of first distilled product, lower than the first flow rate of the first distilled product. The high-pressure or medium-pressure power requirement of the compressor is lower than that during the first operation. During an intermediate operation period following the first operation and preceding the second operation, the power consumption of the one or more compressors from the power grid is lower than that during the first operation and greater than or equal to that during the second operation. The method is characterized in that, during the intermediate operation period, at least a portion of the power requirement of the method operating during the intermediate operation period is met by at least one electrochemical accumulator (A).

2. The method as described in claim 1, wherein, During this intermediate operation, the method reduces high-voltage and / or medium-voltage power consumption.

3. The method as described in claim 1, wherein, During this intermediate operation, once the supply from the energy storage unit (A) begins, the high-voltage and / or medium-voltage power consumption of the method is reduced.

4. The method of claim 1, wherein, During the first and / or second operation, the at least one electrochemical accumulator (A) does not supply medium- and / or high-voltage power to the method.

5. The method of claim 2, wherein, During the first and / or second operation, the at least one electrochemical accumulator (A) does not supply medium- and / or high-voltage power to the method.

6. The method of claim 3, wherein, During the first and / or second operation, the at least one electrochemical accumulator (A) does not supply medium- and / or high-voltage power to the method.

7. The method according to any one of claims 1 to 6, wherein, At the end of this intermediate operation, the at least one electrochemical energy storage device (A) no longer supplies medium- and / or high-voltage power to the method.

8. The method of claim 7, wherein, The electrochemical energy storage device (A) supplies the amount of electricity that decreases over time during this intermediate operation.

9. The method according to any one of claims 1 to 6 and 8, wherein, The difference between the power consumption of the air separation method in the first operation and the power consumption in the second operation is X MW, where X is a number greater than zero and the maximum power supplied during the intermediate operation is at least 0.9X MW.

10. The method of claim 9, wherein, The difference between the power consumption of the air separation method in the first operation and the power consumption in the second operation is X MW, where X is a number greater than zero and the maximum power supplied during the intermediate operation is at least X MW.

11. The method according to any one of claims 1 to 6, 8, and 10, wherein, The at least one electrochemical energy storage device (A) and the one or more compressors (C) of the method are powered by the same power grid (R).

12. The method according to any one of claims 1 to 6, 8, and 10, wherein, The electrochemical accumulator (A) is charged when the electricity price is below a threshold and / or when the power consumption is below a threshold and / or at night.

13. The method according to any one of claims 1 to 6, 8, and 10, wherein, In the event of a reduction in the amount of electricity available on the power grid (R), at least a portion of the power demand of the method is met by an electrochemical energy storage device (A).

14. The method of any one of claims 1 to 6, 8, and 10, comprising the step of pressurizing purified air in a motor-driven booster, the pressurized air being used to evaporate the cryogenic distillation liquid product, wherein the pressurized flow rate is the same during at least two of the three runs.

15. The method according to any one of claims 1 to 6, 8, and 10, wherein, The power grid supplies the method with electricity that decreases over time during this intermediate operation period.

16. The method according to any one of claims 1 to 6, 8, and 10, wherein, The amount of electricity supplied by the power grid during this intermediate operation period is equal to the amount of electricity supplied during the second operation period.

17. An apparatus for separating air by cryogenic distillation, the apparatus comprising at least one compressor (C) for compressing air, means (ER) for cooling and purifying the compressed air, a column system (K) including at least one air distillation column for separating air into oxygen and nitrogen, an electric motor (M) for driving at least one of the at least one compressor, means for supplying high-voltage and / or medium-voltage power from a power grid (R) to the electric motor, at least one electrochemical accumulator (A), means for supplying high-voltage and / or medium-voltage power from the at least one electrochemical accumulator (A) to the electric motor, means for interrupting the power supply from the power grid to the electric motor and means for interrupting the power supply from the at least one electrochemical accumulator (A) to the electric motor, and a control system (S). The device for controlling the interruption of power supply, the device for sending a first flow of air to be compressed in the at least one compressor during the first operation, the device for sending a second flow of air to be compressed in the at least one compressor at a lower flow rate than the first flow rate during the second operation, and the device for connecting the at least one electrochemical accumulator (A) to the motor in response to a load reduction request signal during an intermediate operation after the first operation and before the second operation.

18. The apparatus of claim 17, comprising means for supplying distillation products connected to the column system (K) and at least one cryogenic liquid storage device connected to these means.

Images