Patent Grant
12158246
The present embodiments relate to apparatus and methods used to provide high pressure CO2 from two or more vessels known as accumulators and in particular, to such apparatus and methods used in the electronics industry such as for example in the semiconductor industry.
An accumulator used in the electronics industry is an apparatus that includes a tank or vessel constructed to store fluids at a pressure greater than atmospheric or ambient pressure, and for many applications at a greatly increased pressure. In the electronics industry, such fluids stored in an accumulator can include liquid carbon dioxide (CO2) and liquid nitrogen (N2), which are ultimately permitted to change phase to a gaseous phase for use in such applications as, for example, cleaning of electronics and optics and inerting gases in proximity to same.
Economies of scale encourage the electronics industry to use a pair of accumulators for applications requiring high pressure gaseous CO2. This is because in order to refill one accumulator of the pair that is depleted of CO2 product, the accumulator must be depressurized prior to refilling while the other accumulator of the pair continues with operations. With no other equipment used for such depressurization, this results in a portion of the CO2 during depressurization being vented to atmosphere, an undesirable activity contributing to greenhouse gas (GHG) emissions, and a loss and waste of the gaseous CO2 product.
The known processes to refill a depressurized accumulator, in order to avoid the unwanted CO2 emissions but still be able to recycle and reuse the gaseous CO2 that would otherwise be lost, re-liquefy and recover the CO2 vent gas by cooling the gas through a refrigeration system. Unfortunately, this known recovery process and the related refrigerator system require a large footprint or pad at the processing facility, and consume a large amount of energy and power to re-liquefy and recover the CO2 vent gas, and related costs to re-liquefy the CO2 gas within a specific amount of time allotted for depressurization of the accumulator. This time limitation is critical and therefore burdensome because the refill of the depressurized accumulator must conclude in good time to assume operations from the other accumulator of the pair as the other becomes deleted of its CO2 product.
An example of the known system and method in the semiconductor industry to capture, re-liquefy and pressurize the CO2 gas is shown in
The known system 10 includes a pair of accumulators 12,14, each of which contains liquid CO2 provided from a source 16 of liquid CO2 through a pipe 18 which is split into a separate branch 20 or pipe in fluid connection with the accumulator 12, and a separate branch 22 or pipe in fluid connection with the accumulator 14, respectively.
The known system 10 is constructed to maintain a continuous supply of high-pressure gaseous CO2, wherein the operating cycle of the system replenishes one of the accumulators 12,14, while the other accumulator is dispensing the CO2 product for industrial and/or commercial use. An example of the operating cycle and corresponding “Modes” of the know system 10 is presented below in Table 1.
Still referring to
The accumulator 14 is depressurized into receiver 26 through fluid connections 39,44,45 by opening valves 59,47. The CO2 vapor from the accumulator 14 is condensed into a liquid by passing through a heat exchanger in condenser 24, the condenser also in fluid communication with a refrigeration unit, after which the liquefied CO2 is delivered through a fluid connection 45 or pipe into and to be stored in receiver 26. The condensation of the CO2 vapor is achieved through an external refrigeration unit (not shown, but referenced in
The condenser 24 must condense the CO2 vapor from the accumulator 14 into a liquid during a specific amount of time allotted for depressurization. In other words, when the accumulator 12 nears depletion of its CO2 supply and is required to go off-line in order to be depressurized and refilled, the plant operator does not want there to be a lull in operations waiting for the accumulator 14 to be refilled. Accordingly, the condenser 24 includes a large heat exchanger and refrigeration unit which are required to meet this time sensitive and increased cooling requirement. That is, the depressurization time is set to allow just enough time to fill and pressurize the accumulator 14 before accumulator 12 is depleted of its liquid CO2 supply. This choreography between the accumulators 12,14 and the respective piping and valves is necessary so that a continuous and reliable supply of gaseous CO2 is delivered from the outlet 95 for subsequent plant applications. However, as mentioned above, the known system 10 of
A reciprocal process is provided when the first accumulator 12 is taken off-line from delivery service and is instead being refilled with liquid CO2 from the bulk supply storage tank 16 or vessel containing liquid CO2.
The Modes in the known system 10 with respect to the accumulators 12,14 are shown in the following Table 1 and pertain to
In contrast to the know system discussed above, the present inventive embodiments call for the condenser and refrigeration unit to be of smaller construction with a reduced footprint at the plant or facility. As a result, all the CO2 vented during depressurization of an accumulator in the present embodiments is captured and recovered for subsequent use by the accumulator, thereby reducing the capital and operating costs associated with the refrigeration components of the present system.
There is accordingly provided herein a depressurization system for producing high-pressure gas, such as CO2 gas, from a pair of accumulators, which system includes a gas buffer tank assembly consisting of a gas buffer tank for the pair of the accumulators. The gas buffer tank assembly also includes a pair of depressurization valves for each accumulator such that depressurization to the gas buffer tank from both accumulators and from the gas buffer tank to a condenser facilitates overall system depressurization. The gas buffer tank and respective accumulator pressures are equalized by the present embodiments, thereby temporarily holding a portion of intermediate gas from each accumulator in the gas buffer tank before allowing that gas to be condensed and reliquefied for reintroduction into the same accumulator.
In certain embodiments herein there is provided an apparatus for depressurizing a pair of accumulators to provide high pressure gas, which includes: a tank in fluid communication with each one of the pair of accumulators for receiving vapor from the pair of accumulators for storage and dispensing the vapor to a remote location other than the pair of accumulators and external atmosphere; a first fluid connection including a first valve assembly interconnecting the tank and a first accumulator of the pair of accumulators; a second fluid connection including a second valve assembly interconnecting the tank and a second accumulator of the pair of accumulators; wherein the first fluid connection with the first valve assembly and the second fluid connection with the second valve assembly are each constructed and arranged to deliver the vapor from a corresponding one of the first accumulator and the second accumulator to the tank during alternating intervals.
In certain embodiments of the apparatus the remote location includes a condenser to condense the vapor into a liquid.
In certain embodiments the apparatus further includes a receiver tank in fluid connection with the condenser for receiving and storing the liquid until needed by the first accumulator and the second accumulator.
In certain other embodiments of the apparatus the vapor is from a liquid selected from the group consisting of liquid CO2, and liquid nitrogen.
In certain embodiments herein there is provided a method for depressurizing a pair of accumulators for providing high-pressure gas, which includes: (a) withdrawing a portion of vapor from a first accumulator of the pair of accumulators to a tank; (b) equalizing pressures in the first accumulator and the tank for temporarily holding the portion of the vapor as an intermediate gas from the first accumulator in the tank; (c) providing the intermediate gas to a remote location other than the pair of accumulators and atmosphere; (d) condensing the intermediate gas into a liquid at the remote location; and (e) returning the liquid to the first accumulator.
In certain embodiments the method includes providing high-pressure gas from a second accumulator of the pair of accumulators during steps (a)-(e).
In certain other embodiments the method further includes storing the liquid at the remote location before the returning the liquid to the first accumulator.
In certain other embodiments the method includes the vapor being from a liquid selected from the group consisting of liquid CO2, and liquid nitrogen.
For a more complete understanding of the present invention, reference may be had to the following description of exemplary embodiments considered in connection with the accompanying drawing Figures, of which:
Before explaining the inventive embodiments in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, if any, since the invention is capable of other embodiments and being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.
In the following description, terms such as a horizontal, upright, vertical, above, below, beneath and the like, are to be used solely for the purpose of clarity illustrating the invention and should not be taken as words of limitation. The drawings, if any, are for the purpose of illustrating the invention and are not intended to be to scale.
References herein to “fluid connections” can be taken to mean a conduit, pipe, passageway or the like which provides for delivery or fluid communication of fluids, and also includes the plural of such elements.
Referring to
The depressurization system embodiment 100 is a high-pressure gas delivery system, and which differs from the known system 10 of
The high-pressure gas delivery system is shown generally at 100. A first accumulator 12 delivers high pressure gaseous CO2 through fluid connections 28, 32 or pipes to the outlet 95 for use in a gaseous application, while a second accumulator 14 is refilled from a bulk supply of liquid CO2 16. The second accumulator 14 must be refilled and ready to assume operations before the first accumulator 12 is depleted of its CO2. The accumulator 14 must first be depressurized before it can be refilled with liquid CO2. The depressurization of the accumulator 14 occurs in two stages: 1st stage—the accumulator 14 is initially depressurized into the gas buffer tank 104 of the buffer tank assembly 102 until such time as the respective pressures in the accumulator 14 and the gas buffer tank 104 are equalized to temporarily store a portion of the CO2 vapor in the gas buffer tank 104; 2nd stage—the accumulator 14 is then fully depressurized into receiver 26 via the fluid connections 39,44 into the condenser 24, whereupon the CO2 vapor is condensed into a liquid. Such condensation is achieved through an external refrigeration unit (not shown) and the condensed liquid provided to the receiver 26 via a fluid connection 45 from the condenser 24 to the receiver. Once the accumulator 14 is fully depressurized to the desired pressure setpoint, the liquid CO2 temporarily stored in the receiver 26 is delivered back to the accumulator 14 through fluid connections 46,42 by opening valve 57. The accumulator 14 is also refilled or topped-off to the desired level setpoint with additional liquid from the liquid CO2 supply 16, where a feed stream 18 comprising liquid CO2 is introduced into the accumulator 14 through fluid connection 22. The accumulator 14 is heated (e.g., by an electric heater 50) to vaporize the liquid CO2 stored in the accumulator and to pressurize same to a delivery pressure for the gaseous CO2 stream to be produced by the system 100 and delivered through fluid connections 30,32 to the outlet 95 for application use. The delivery pressure at the outlet 95 is in the range of 600 psig to 1000 psig.
While the accumulator 14 is getting refilled and pressurized, the gas buffer tank 104 is depressurized into the receiver 26 via fluid connections 206,39,44,45, where the CO2 vapor is condensed into a liquid by the heat exchanger in the condenser 24. Such condensation is achieved through an external refrigeration unit (not shown, but referred to) in communication with the heat exchanger of the condenser 24. The liquid CO2 is also held temporarily in the receiver 26 until the next cycle, wherein the liquid CO2 will be delivered to the accumulator 12 via fluid connections 46,40 or pipes after that accumulator undergoes its depressurization stages.
By initially equalizing the pressures between the accumulator 14 and the gas buffer tank 104 before fully depressurizing the accumulator 14, the amount of CO2 vapor to be condensed in the condenser 24 during this stage is substantially less than what occurs with the known system 10. By temporarily holding a portion of the CO2 vapor in the gas buffer tank 104, the process of condensing the CO2 vapor can be extended over a longer timeframe to thereby reduce the cooling requirement of the condenser 24; instead of being constrained to the strict amount of time allotted for depressurizing the accumulator 14 as is required in the known system 10. Depressurizing the gas buffer tank 104 and condensing the corresponding CO2 vapor occurs during the filling and pressurizing steps of the accumulator 14. This in turn also allows the refrigeration unit to run continuously or nearly continuously to avoid frequent cycling.
The Modes in the system embodiment 100 with respect to the accumulators 12,14 are shown in the following Table 2 and pertain to
The system 100 is therefore more economical than the known system 10 due to the reduction in size of the refrigeration unit and the condenser 24.
The depressurization cycle stages for and the co-action among the accumulators 12,14 and the gas buffer tank 104 of the buffer tank assembly 102 can be summarized as:
The gas buffer tank 104 reduces an amount of CO2 gas leaving the accumulator 12,14 during depressurization of same and offers more time to re-liquefy the CO2 gas through the condenser 24 and the refrigeration unit. The condenser 24-refrigeration unit size and related footprint is significantly reduced as a result of the addition of time from the gas buffer tank 104 and therefore, the related capital and operating costs for the system 100 are also reduced. The present embodiments provide a cost-effective solution to capture all the CO2 gas during depressurization in order to (i) avoid a loss of the CO2 product, (ii) avoid an increase in GHG emissions, and (iii) reduce the size of the condenser/refrigeration unit to condense the CO2 vapor.
Manual valves 71-93 (odd-numbered) are provided for shut-off and partial closure of corresponding fluid connections or pipes to adjust timing of vapor and liquid being delivered through the respective systems 10,100, and one or plurality of same can be included depending upon the system application.
This present embodiments can be applied to other liquid products (e.g., liquid nitrogen or LIN) using the same apparatus and processes herein, wherein the liquid is heated inside an accumulator or a vessel to deliver a high-pressure gas, and to recover and use any gas or vapor in a cost-effective way that would otherwise be vented.
Even without adding the condenser 24 with its heat exchanger and the refrigeration unit, the gas buffer tank 104 will substantially reduce an amount of vent gas during depressurization.
It will be understood that the embodiments described herein are merely exemplary, and that a person skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as provided in the appended claims. It should be understood that the embodiments described above are not only in the alternative but can be combined.
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| 63236462 | Aug 2021 | US |
