DEPRESSURIZATION SYSTEM, APPARATUS AND METHOD FOR HIGH PRESSURE GAS DELIVERY

Abstract

An apparatus for depressurizing a pair of accumulators to provide high pressure gas 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. A related method and system are also provided.

Claims

1. An apparatus for depressurizing a pair of accumulators to provide high pressure gas, comprising: 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.

2. The apparatus of claim 1, wherein the remote location comprises a condenser to condense the vapor into a liquid.

3. The apparatus of claim 2, further comprising 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.

4. The apparatus of claim 1, wherein the vapor is from a liquid selected from the group consisting of liquid CO2, and liquid nitrogen.

5. A method for depressurizing a pair of accumulators for providing high-pressure gas, comprising: (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.

6. The method of claim 5, further comprising providing high-pressure gas from a second accumulator of the pair of accumulators during steps (a)-(e) of claim 5.

7. The method of claim 5, further comprising storing the liquid at the remote location before the returning the liquid to the first accumulator.

8. The method of claim 5, wherein the vapor is from a liquid selected from the group consisting of liquid CO2, and liquid nitrogen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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:

[0024] FIG. 1 shows a schematic of a known system for depressurizing gas to provide high pressure CO.sub.2.

[0025] FIG. 2 shows a schematic of a depressurization system, and apparatus and method embodiments of the present invention for high pressure gas delivery of, for example, CO.sub.2 gas.

[0026] FIG. 3 shows a gas buffer tank embodiment of the present invention used in the system embodiment shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0027] 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.

[0028] 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.

[0029] 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.

[0030] Referring to FIGS. 2-3, the inventive embodiments herein include a depressurization system 100 with, among other elements, gas buffer tank assembly 102 (hereinafter referred to also as the “buffer tank assembly 102”). The buffer tank assembly 102 can be retrofit into or be of original construction with the known system 10 for co-action with the accumulators 12,14. The buffer tank assembly 102 collects a portion if not all of the CO.sub.2 gas generated during depressurization from a respective one of the accumulators 12,14 to equalize the pressures between same in order to temporarily store the CO.sub.2 vapor and separate the depressurization stage into two separate stages. The buffer tank assembly 102 includes a gas buffer tank 104 as shown in FIGS. 2-3. That is, with respect to the accumulator 12 the buffer tank assembly 102 includes the gas buffer tank 104, the fluid connection 106 or pipe and the valve 108; and with respect to the accumulator 14 the buffer tank assembly 102 includes the gas buffer tank 104, the fluid connection 206 or pipe and the valve 208.

[0031] The depressurization system embodiment 100 is a high-pressure gas delivery system, and which differs from the known system 10 of FIG. 1 by the addition of a gas buffer tank 104 and its corresponding piping and valves (valve assemblies) to and from each one of the accumulators 12,14. The system 100 is constructed and arranged to maintain a continuous supply of high-pressure gaseous CO.sub.2, wherein an operating cycle of the buffer tank assembly 102 is set to replenish a first one of the accumulators 12,14, while a second one of the accumulators is dispensing the CO.sub.2 gaseous product. In this manner of construction and operation, there is no lag, lull or downtime during the on-demand CO.sub.2 supply, and there is required a far smaller condenser and refrigeration unit footprint or pad for depressurization of the accumulators 12,14, than is required for the known system 10. An example of the operating cycle and corresponding “Modes” is presented below in Table 2.

[0032] The high-pressure gas delivery system is shown generally at 100. A first accumulator 12 delivers high pressure gaseous CO.sub.2 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 CO.sub.2 16. The second accumulator 14 must be refilled and ready to assume operations before the first accumulator 12 is depleted of its CO.sub.2. The accumulator 14 must first be depressurized before it can be refilled with liquid CO.sub.2. The depressurization of the accumulator 14 occurs in two stages: 1.sup.st 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 CO.sub.2 vapor in the gas buffer tank 104; 2.sup.nd stage—the accumulator 14 is then fully depressurized into receiver 26 via the fluid connections 39,44 into the condenser 24, whereupon the CO.sub.2 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 CO.sub.2 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 CO.sub.2 supply 16, where a feed stream 18 comprising liquid CO.sub.2 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 CO.sub.2 stored in the accumulator and to pressurize same to a delivery pressure for the gaseous CO.sub.2 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.

[0033] 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 CO.sub.2 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 CO.sub.2 is also held temporarily in the receiver 26 until the next cycle, wherein the liquid CO.sub.2 will be delivered to the accumulator 12 via fluid connections 46,40 or pipes after that accumulator undergoes its depressurization stages.

[0034] By initially equalizing the pressures between the accumulator 14 and the gas buffer tank 104 before fully depressurizing the accumulator 14, the amount of CO.sub.2 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 CO.sub.2 vapor in the gas buffer tank 104, the process of condensing the CO.sub.2 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 CO.sub.2 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.

[0035] The Modes in the system embodiment 100 with respect to the accumulators 12,14 are shown in the following Table 2 and pertain to FIGS. 2-3.

TABLE-US-00002 Table 2 Description of: Mode Designation Accumulator 12 Accumulator 14 Offline 0 All valves closed, heaters 48,50 off, All valves closed, heaters 48,50 off, refrigeration unit off. refrigeration unit off. Equalize 1 Initially depressurize accumulator Initially depressurize accumulator 14 12 into gas buffer tank 104 to into gas buffer tank 104 to equalize equalize pressures. pressures. Depressurization valves Depressurization valves 108 and 208 and 210 open. Depressurization 110 open. Depressurization valves valves 59 and 47, supply valve 49, 51 and 47, supply valve 49, fill valve fill valve 61, product valve 67, and 55, product valve 63, and receiver receiver valve 57 closed. valve 53 closed. Depressurize 2 Complete accumulator 12 Complete accumulator 14 depressurization prior to refilling depressurization prior to refilling with with low-pressure liquid. low-pressure liquid. Depressurization valves 110, 51 Depressurization valves 210, 59 and and 47 open. Depressurization 47 open. Depressurization valve valve 108, supply valve 49, fill valve 208, supply valve 49, fill valve 61, 55, product valve 63, and receiver product valve 67, and receiver valve valve 53 closed. Refrigeration unit 57 closed. Refrigeration unit on. on. Fill 3 Fill accumulator 12 with low- Fill accumulator 14 with low- pressure liquid from receiver 26 and pressure liquid from receiver 26 and liquid source 16. Receiver valve 53, liquid source 16. Receiver valve 57, supply valve 49 and fill valve 55 supply valve 49 and fill valve 61 open. Product valve 63 closed. open. Product valve 67 closed. Refrigeration unit on. Refrigeration unit on. Depressurize 4a Depressurize gas buffer tank 104. Depressurize gas buffer tank 104. Gas Buffer Depressurization valves 108, 51, Depressurization valves 208, 59, and 47 open. Depressurization and 47 open. Depressurization valve 110 and receiver valve 53 valve 210 and receiver valve 57 closed. Refrigeration unit on. closed. Refrigeration unit on. Pressurize 4b Pressurize accumulator 12 up to the Pressurize accumulator 14 up to the setpoint (i.e., using electric setpoint (i.e., using electric immersion heater 48). Supply 49, fill immersion heater 50). Supply 49, fill 55 and product 63 valves closed. 61 and product 67 valves closed. Refrigeration unit on. Refrigeration unit on. Ready 5 System hold at pressure awaits System hold at pressure awaits dispensing high-pressure gas 28. dispensing high-pressure gas 30. Depressurization 108,110,51,47, Depressurization 208,210,59,47, receiver 53, supply 49, fill 55 and receiver 57, supply 49, fill 61 and product 63 valves closed. product 67 valves closed. Online 6 System supplying high-pressure System supplying high-pressure gas gas 95. Product valve 63 open. 95. Product valve 67 open. Depressurization valves Depressurization valves 208, 108,110,51, fill valve 55 and 210,59, fill valve 61 and receiver receiver valve 53 closed. valve 57 closed.
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.

[0036] 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: [0037] 1. Equalize the respective accumulator 12,14 and the gas buffer tank 104 pressures. [0038] 2. Depressurize the accumulator/re-liquefy CO.sub.2 to fill the receiver 26. [0039] 3. Fill the accumulator from the receiver. [0040] 4. Fill the accumulator from the liquid CO.sub.2 feed 16 and begin to depressurize the gas buffer tank 104/re-liquify to fill the receiver 26. [0041] 5. Pressurize the accumulator with the respective heater 48,50. [0042] 6. Complete depressurization of the gas buffer tank 104 (the receiver 26 is now partially filled with CO.sub.2 liquid), and standby. [0043] 7. Switchover and dispense high pressure CO.sub.2 from the 1.sup.st accumulator when the 2nd accumulator is depleted. [0044] 8. Start depressurization cycle on the 2.sup.nd accumulator. [0045] 9. Repeat.

[0046] The gas buffer tank 104 reduces an amount of CO.sub.2 gas leaving the accumulator 12,14 during depressurization of same and offers more time to re-liquefy the CO.sub.2 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 CO.sub.2 gas during depressurization in order to (i) avoid a loss of the CO.sub.2 product, (ii) avoid an increase in GHG emissions, and (iii) reduce the size of the condenser/refrigeration unit to condense the CO.sub.2 vapor.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.