Patent Grant
10443785
This invention relates to a novel method and system for delivery of carbon dioxide from multiple containers to an-end-user or customer point of use for a variety of applications. Additionally, the invention relates to an automated system for performing certain integrity checks prior to filling of carbon dioxide into one or more container.
Carbon dioxide (CO2) storage and dispensing systems have been used for a variety of applications, including, by way of example, on-site beverage dispensing applications, such as a carbonated beverage dispenser. The beverage industry uses CO2 to carbonate and/or transport beverages from a storage tank to a specified dispensing area. By example, beverages such as beer can be contained in kegs in the basement or storage room and the taps at the bar can dispense the beer. The storage and delivery of beer from the kegs can occur in a keg area that is located away from where the patrons are sitting. In order to transport the beer from the keg area to the serving area, CO2 has generally been delivered as a liquid in cylinders. The liquid CO2 cylinders are connected to the kegs, which can comprise one or several tanks or barrels. CO2 in the liquid CO2 cylinders is not completely filled with liquid, thereby allowing the carbon dioxide to vaporize into a gaseous state, which is then used to carbonate as well as move the desired beverage from the storage room or basement to the delivery area and provide much of the carbonation to the beverages.
Today, the usage of CO2 storage and dispensing systems is widespread. Many conventional CO2 storage and dispensing systems utilize low pressure dewars (e.g., vacuum insulated jacketed container) which are typically considered a low pressure storage and dispensing system that is filled to no greater than about 300 psig. Notwithstanding the vacuum insulation, the cold CO2 fluid that fills into a liquid CO2 dewar increases in temperature and vaporizes as heat is gained by the dewar. The vapor generates a higher pressure in the dewar, which may require venting to avoid over pressurization. As such, dewar usage is undesirable as it can increase CO2 products losses arising from the need to periodically vent the excess pressure to avoid over pressurization.
As an alternative to dewars, high pressure uninsulated CO2 storage and dispensing systems have been employed in an attempt to increase CO2 product utilization. However, current high pressure uninsulated CO2 liquid storage and dispensing systems can increase the risk of over pressurization. For example, the maximum permitted filling capability for an uninsulated CO2 liquid cylinder is 68 wt % of total weight (based on water weight). In other words, the system should not be filled to more than 68 wt % by water weight. As temperature increases, the liquid CO2 can vaporize into the headspace and expand to a point where the maximum working pressure of the cylinder is exceeded, thereby potentially rupturing the cylinder.
As a means to control the amount of liquid CO2 filled in uninsulated cylinders, multiple cylinders employing liquid and vapor cylinders have been used. A 2:1 volume ratio for the volume of liquid cylinder to vapor cylinder has been generally regarded as safe operating practice within the industry. Specifically, at the 2:1 volume ratio, the volume of the vapor cylinder and an additional 10% headspace in the liquid cylinder in which the liquid cylinders are deemed to be maximally filled as defined above can create approximately 40% headspace by volume of the combined capacity of the liquid and vapor cylinders. However, this methodology of determining when the system is full poses the risk of overfilling the CO2 liquid containers. Overfilling can also result in the system not operating properly and lead to erratic supply of CO2 vapor product to a customer or end-user.
In view of such drawbacks, there is a need for an improved method and high pressure system for optimizing CO2 filling, storage and dispensing that is not prone to over pressurization.
As will be described herein, the present invention employs a pressure differential device with shuttle valve between the liquid and vapor CO2 containers to maintain a higher pressure in the liquid container relative to the vapor container during filing and subsequent supply of CO2 vapor product from the vapor container to the customer. During CO2 vapor product supply to the customer, vapor transfer from the liquid container to the vapor container is limited until the pressure in the vapor container drops to below the differential pressure set point. This arrangement will preferentially deplete liquid from the vapor container versus vapor transfer from the liquid container, thereby mitigating the potential of over pressurization of the on-site system. The on-site system as used herein can be advantageously assembled on-site at the end-user or customer premises.
In a first aspect, a CO2 safety interlock fill system configured to perform pre-fill integrity checks for automatically leak checking a fill manifold and pressurizing the fill manifold, said pre-fill integrity checks for the leak checking and the pressurizing of the fill manifold performed prior to the CO2 safety interlock fill system allowing a subsequent filling operation of liquefied carbon dioxide (CO2) product into a container from an onsite CO2 source, said CO2 safety interlock fill system comprising: the onsite CO2 source, said onsite CO2 source comprising a source vessel containing liquefied CO2, and vaporized CO2 in a headspace of the source vessel; a fill manifold operably connected to the source vessel, said fill manifold comprising one or more conduits positioned between the source vessel and the container, said one or more conduits comprising at least a CO2 vapor supply conduit extending into the headspace of the source vessel of the onsite CO2 source; said fill manifold further comprising at least one pressure transducer situated along the one or more conduits, said CO2 vapor supply conduit of the fill manifold configured to receive a finite amount of the vaporized CO2 during the pressurization and leak checking of the fill manifold, said CO2 vapor supply conduit receiving the vaporized CO2 from the headspace of the source vessel of the onsite CO2 source; a controller in communication with the fill manifold and the at least one pressure transducer to automatically perform the leak checking of the fill manifold and the pressurization of the fill manifold, the controller having as a first input a first set point equal to the unallowable reduction in pressure of the vaporized CO2 in the fill manifold during a predetermined time period that the leak checking occurs, and further wherein the controller has a second set point equal to the predetermined lower pressure of the vaporized CO2 in the fill manifold below which dry ice may form and a third set point equal to the predetermined upper pressure of the vaporized CO2 above which reversible flow of CO2 vapor may occur from the container into the fill manifold; wherein the controller is configured to receive signals corresponding to real-time pressure measurements from the pressure transducer during the predetermined time period of the leak check and/or the pressurization of the fill manifold; said controller configured to prevent the subsequent filling operation when (i) one or more of the real-time pressure measurements has changed in pressure by an amount that is equal to or higher than the first set point of the unallowable reduction in pressure of the vaporized CO2 in the fill manifold, or (ii) the one or more of the real-time pressure measurements is lower than the predetermined lower pressure at which dry ice forms, or (iii) the one or more of the real-time pressure measurements is greater than the predetermined upper pressure at which reversible flow of CO2 vapor may occur from the container into the fill manifold; and said controller is configured to allow the subsequent filling operation when each of (i) the one or more of the real-time pressure measurements has change in pressure by an amount that is less than the first set point of the unallowable reduction in pressure of the vaporized CO2 in the manifold, and (ii) the one or more of the real-time pressure measurements is equal to or above the predetermined lower pressure at which dry ice forms, and (iii) the one or more real-time pressure measurements is equal to or lower than the predetermined upper pressure at which reversible flow of CO2 vapor may occur from the container into the fill manifold.
In a second aspect, a method of performing pre-fill integrity checks for automatically leak checking a fill manifold and pressurizing the fill manifold, comprising: introducing a finite amount of vaporized CO2 into a fill manifold operably connected to a source vessel of an onsite CO2 source, said fill manifold comprising a CO2 vapor supply conduit, said CO2 vapor supply conduit having a first end and a second end, the first end extending into a headspace of the source vessel of the onsite CO2 source, the second end extending towards a container; inputting a first set point into a controller in communication with the fill manifold, said first set point equal to the unallowable reduction in pressure of the vaporized CO2 introduced into the fill manifold; inputting a second set point into the controller, said second set point equal to a predetermined lower pressure of the vaporized CO2 in the fill manifold, said predetermined lower pressure being a pressure at which an onset of dry ice formation in the fill manifold can occur; inputting a third set point into the controller, said third set point equal to a predetermined upper pressure of the vaporized CO2 in the fill manifold above which reversible flow of CO2 vapor may occur from the container into the fill manifold; measuring the real-time pressures in the fill manifold and generating signals corresponding to each of the real-time pressures; transmitting the signals to the controller operably connected to the fill manifold; determining the pre-fill integrity checks, such that either (a) one or more of the real-time pressures (i) has changed in pressure by an amount that is equal to or higher than the first set point, or (ii) is equal to or lower than the second set point, or (iii) is greater than the third set point; and in response thereto preventing a subsequent filling of CO2 liquid from the onsite CO2 source to the container along the fill manifold; or (b) one or more of the real-time pressure measurements (i) has changed in pressure by an amount that is less than the first set point, and (ii) is above the second set point, and (iii) is lower than the third set point; and in response thereto allowing the subsequent filling of the CO2 liquid from the onsite CO2 source to the container along the fill manifold.
As will be described with reference to the Figures the present invention offers a system for the on-site filling of a carbon dioxide (CO2) container system.
The present invention has recognized that expansion of liquid CO2 and its volume can increase by approximately 30 vol % when the temperature of the liquid cylinder increases from about 0 deg C. to 20 deg C. Therefore, an appreciable volume of CO2 can be transferred to the vapor container from the liquid container even though only the liquid cylinder is filled. Thus, the vapor cylinder contains not only vapor but also liquid. Furthermore, during use, more CO2 vaporizes from the liquid cylinder and is consumed by the customer compared to that from the vapor cylinder. Therefore, with subsequent or successive refills, the required volume of the vapor headspace may prove inadequate.
The present invention offers a novel solution for mitigating the risk of insufficient vapor headspace resulting in over-pressurization of the system by preferably consuming the CO2 in the vapor container 2 rather than the CO2 in liquid container 1. The system 10 comprises a liquid CO2 container 1 and a vapor CO2 container 2 operably connected to the liquid CO2 container 1. As part of the methodology of the present invention, the vapor CO2 container is designed to function as a so-called “virtual headspace” for the liquid CO2 container 1 in a specific manner that avoids over pressurization of the system. CO2 vapor product dispenses to an end-user or customer in a controlled manner, whereby the amount of CO2 vapor product dispensed from the vapor CO2 container 2 is maximized, and the amount of CO2 vapor product dispensed from the liquid CO2 container 1 is minimized. In this manner, a substantial portion of the overall CO2 vapor product is obtained from the vapor CO2 container 2. Unlike other CO2 storage and dispensing systems, the present invention limits transfer of CO2 liquid from the liquid CO2 container 1 to the vapor CO2 container 2 until the pressure in the vapor CO2 container 2 has reduced to a certain level, at which point, a pressure differential device is triggered to allow the flow of CO2 fluid from the liquid CO2 container 1 to the vapor CO2 container 2. As such, CO2 liquid is preferentially depleted from the vapor CO2 container 2 prior to transfer of CO2 fluid from the liquid CO2 container 1.
Because of these distinctive operating features, the present invention offers numerous benefits, including, but not limited to, a system that can deliver the proper amount of liquid CO2 while also reducing the hazards associated with overfilling; a system which enables the end-user or customer to continue using the delivery system without interruption even when the system is being filled; a system that does not require an end-user or customer to enter the premises of the on-site dispensing system to shut down or adjust valving before and after delivery of the CO2 liquid; a system that allows automatic re-fill of CO2 fluid into the system at any time of the day or night without any contact with personnel; and a system that can reduce the amount of carbon dioxide vented to the atmosphere due to increase of temperature or as a means of determining a filled system, thereby resulting in less CO2 product waste, less cost to both the customer or end-user and less potential hazards.
It should be understood that the on-site systems of the present invention can include a single liquid CO2 container or multiple liquid CO2 containers directly or indirectly connected to a single vapor CO2 container or multiple vapor CO2 containers. The liquid CO2 container can receive and stores high-pressure liquefied CO2 from a refrigerated CO2 source. In one example, the liquid CO2 container can be refilled with the high-pressure liquefied CO2 from the CO2 source (e.g., automated truck having refrigerated and pressurized CO2 source) by a fill hose. “Fluid” as used herein means any phase including, a liquid phase, gaseous phase, vapor phase, supercritical phase, or any combination thereof.
“Container” as used herein means any storage, filling and delivery vessel capable of being subject to pressure, including but not limited to, cylinders, dewars, bottles, tanks, barrels, bulk and microbulk.
“Connected” as used herein means a direct or indirect connection between two or more components by way of conventional piping and assembly, including, but not limited to valves, pipe, conduit and hoses, unless specified otherwise.
The terms “liquid container” and “liquid CO2 container” will be used interchangeably to mean a container that contains substantially liquid. The terms “vapor container” and “vapor CO2 container” will be used interchangeably to mean a container contains substantially vapor.
The term “conduit”, “flow leg” and “pathway” and “flow path” as used herein are intended to mean” mean flow paths or passageways that are created by any (i) conventional piping, hoses, passageways and the like; (ii) as well as within the valving, such as a shuttle valve.
“CO2 product” and “CO2 vapor product” will be used interchangeably and are intended to have the same meaning.
The present invention in one aspect, and with reference to
The inventors have observed that this transfer of CO2 fluid from the liquid CO2 container 1 to the vapor CO2 container 2 has a tendency to accumulate CO2 liquid in the vapor CO2 container 2 if the CO2 liquid is not preferentially consumed in the vapor cylinder during usage. “Preferentially consumed during usage” as used herein means that CO2 vapor product is substantially delivered from the vapor CO2 container 2 to the end-user or customer while CO2 vapor product is limited from the liquid CO2 container 1 until substantially all of the liquid CO2 in the vapor container has vaporized and been dispensed to the end-user or customer. In particular, with regards to conventional systems, after one or more subsequent or successive fills of CO2 liquid into the liquid CO2 container 1 of the system 10, the liquid CO2 can accumulate within the vapor CO2 container 2, particularly when the customer or end-user does not use a significant amount of CO2 between the fills, thereby causing the total amount of CO2 in the system to exceed the maximum permitted filling capability (i.e., 68 wt % based on water weight capacity). In this manner, with regards to conventional systems, the virtual headspace of the vapor CO2 container 2 is reduced, and creates an on-site dispensing system that is potentially over pressurized. An overfilled liquefied CO2 system may experience significant internal pressure excursions and build-up from expansion of the liquid CO2 as it warms. As a result, the present invention has recognized that conventional CO2 storage, filling and dispensing systems are prone to over pressurization.
In accordance with the principles of the present invention, an exemplary system and method for optimizing the filling, storage and dispensing of CO2 from a liquid CO2 container and a vapor CO2 container is provided as will be described in connection with
During the filling and subsequent usage of the system 10, the liquid CO2 cylinder 1 stores a majority of the liquid CO2 while the vapor CO2 cylinder 2 contains mostly vapor CO2 and a minimal amount of liquid CO2, which evaporates and is then preferentially dispensed as vapor product to the customer or end user prior to the transfer of additional CO2 fluid from the liquid CO2 cylinder 1 to the vapor CO2 cylinder 2.
Various sizes of cylinders may be used for the liquid and vapor CO2 cylinders 1 and 2, respectively. Preferably, the vapor cylinder 2 is configured to be the same size or larger in volume than the liquid cylinder 1. As such, in comparison to conventional CO2 storage and dispensing systems, the present invention allows the vapor CO2 cylinder 2 to provide a larger virtual vapor headspace and capacity for liquid expansion therein. This virtual vapor headspace is preserved during filling, storage and use, thereby making the system safer than conventional CO2 storage and dispensing systems.
Suitable materials for the cylinders 1 and 2 may be selected based on operating temperature. Specifically, under certain conditions from the standpoint of materials of construction, the temperature of the liquid CO2 cylinder 1 and vapor CO2 cylinder 2 may be below safe limits for common carbon or alloy steel cylinder. Generally speaking, steel's ductile to brittle transition temperature is the result of its (i) alloy composition and (ii) heat treatment. Uncertainties in either property (i) or (ii) during fabrication of the steel cylinder may raise the materials' minimum ductile material temperature (MDMT) to unacceptable levels during filling of the liquid CO2 cylinder 1 with refrigerated CO2. Consequently, in one embodiment of the present invention, alloy steel containers or 6061 T6 aluminum cylinders may be preferred.
In a preferred embodiment, the liquid CO2 cylinder 1 may be filled by a refrigerated liquid CO2 source, such as a CO2 delivery truck that is equipped with a high pressure liquid CO2 pump. The filling is preferably based on pressure, such that when a pre-set fill pressure is reached, the high pressure liquid CO2 pump will stop. Referring to
Valve 4 is a specially designed shuttle valve. The valve 4 includes a reciprocating shuttle valve 4, which is preferably spring-based.
The filling operation in one aspect of the present invention will be explained. Referring to
A pressure differential device 7, which can be located on the vapor port of the shuttle valve 4 and which is situated between the liquid cylinder 1 and the vapor cylinder 2 (
Contrary to conventional on-site CO2 filling processes which generally tend to fully isolate the vapor cylinder 2 from liquid cylinder 1 during filling of CO2 into the system 10, the present invention deliberately avoids complete isolation of the vapor cylinder 2 from the liquid cylinder 1 during the filling operation. The ability to allow a restricted amount of CO2 liquid into the vapor cylinder 2 through a restrictive pathway created and maintained during filling appears counterintuitive to the design objective of creating and preserving the vapor headspace of the vapor container 2. However, the relatively small amount of CO2 introduced into the CO2 vapor cylinder 2 can exert a certain pressure that allows for pressure equalization between both sides of the shuttle valve 4 and ultimately can substantially balance the pressure between liquid cylinder 1 and vapor cylinder 2, thereby allowing the return of the piston 40 towards the fill port 43 when the filling of the pressurized and refrigerated CO2 into the liquid CO2 cylinder 1 is completed, and the liquid CO2 pump has shut off. The ability for the piston 40 to reseat occurs without introducing a significant amount of CO2 liquid into the vapor container 2 that reduces the vapor headspace of the vapor cylinder 2. Accordingly, the filling operation allows substantial CO2 loading into the liquid cylinder 1 while minimizing liquid CO2 into the vapor cylinder 2 to preserve the vapor headspace of the vapor container 2. Without a restrictive passageway from fill port 43 along the clearance or gap between the body of valve 4 and the piston 40, the piston 40 may not reliably reseat onto the fill port 43. The undesirable result is substantial isolation of the vapor cylinder 2 from the liquid cylinder 1 during CO2 dispensing from the system 10 (i.e., the scenario of
Additionally, when the vapor container 2 does not have significant positive pressure, such as may occur during start up, or during operation when the vapor cylinder 2 has low pressure, the piston 40 may not reseat due to higher pressure on the liquid fill port side of the shuttle valve 4 compared to that of the vapor fill port side. The liquid cylinder 1 is essentially isolated from the vapor cylinder 2 which potentially creates a hazardous overpressurized condition of the system 10, whereby the pressure in the liquid cylinder 1 can increase. Accordingly, the inclusion of a gap or clearance between the piston 40 of valve 4 and housing of the valve 4 that is in communication with the fill port 43 creates and maintains a restrictive flow path from fill port 43 into the vapor cylinder 2 during the filling operation (as shown by the arrows in
As a result, complete isolation of the vapor cylinder 2 from the liquid cylinder 1 during fill is avoided by the present invention, but, in doing so, only a restrictive flow path is created and maintained during filling to allow a limited and controlled amount of CO2 fluid into the vapor cylinder 2 as necessary to reseat the piston 40 and substantially equalize pressures of the cylinders 1 and 2. In one embodiment, the amount of CO2 liquid entering the vapor cylinder 2 is less than 30 wt % of the total incoming flow of pressurized and refrigerated CO2 fluid from the CO2 source during a fill; preferably less than 20 wt %; and more preferably less than 10 wt %.
After filling, the pressure of the liquid cylinder 1 can continue increasing for many hours as the liquid CO2 will tend to evaporate until equilibrium is achieved. During this equilibrating period, the pressure differential device 7, situated between the liquid cylinder 1 and the vapor cylinder 2, can remain open, in response to a predetermined pressure difference between the cylinders 1 and 2, which prevents the liquid cylinder 1 from overpressurizing.
Upon completion of filling, and after the system 10 has stabilized to reach a substantial equilibrium state, the use of the system 10 for dispensing CO2 vapor product to an end-user or customer can occur, as will now be described. It should be noted that initially, during use of the system 10 to dispense CO2 vapor product, the piston 40 of the shuttle valve 4 reseats into its unbiased position and remains in the unbiased position (
Although the piston 40 is not substantially blocking the flow path to the vapor cylinder 2 to create a restrictive flow pathway, as can occur during filling, as will be explained herein below, a pressure differential device 7 is situated between the liquid cylinder 1 and the vapor cylinder 2. The pressure differential device 7 is specifically triggered to open and close under specific operating conditions to preferentially deplete CO2 liquid from the vapor container 2. Specifically, CO2 vapor product is preferentially dispensed from the vapor CO2 container 2 with the pressure differential device 7 in the closed position, until a pressure difference between the liquid CO2 container and the vapor CO2 container acquires a set point value, at which point pressure differential device 7 opens to allow additional CO2 fluid to be transferred from the liquid container 1 to the vapor container 2. Preferably, the pressure differential device 7 is set to a certain pressure difference between the liquid container 1 and the vapor container 2 that must be reached or exceeded before opening to allow CO2 fluid transfer from the liquid container 1 to the vapor container 2. Alternatively, the pressure differential device 7 can be set to a certain set point that the pressure in vapor container 2 must reach or drop below before opening. The pressure differential device 7 in the open position allows subsequent or successive refill of CO2 liquid into the liquid CO2 container and/or a transfer of CO2 fluid from the liquid CO2 container 1 to the vapor CO2 container 2.
The pressure differential device 7 can be installed on the vapor port of shuttle valve 4 as shown in
Referring to
Without being bound by any particular theory or mechanism, it is believed that the preferential depletion of CO2 liquid in the vapor cylinder 2 may occur as follows. As CO2 vapor is withdrawn from the vapor cylinder 2, the vapor pressure in the vapor cylinder 2 drops to a level that is lower than the initial vapor pressure corresponding to the initial temperature, which is typically ambient temperature (i.e., the temperature of the premises where the vapor cylinder 2 is located). The reduction in pressure causes liquid CO2 in the vapor cylinder to evaporate to re-establish the vapor pressure in the vapor cylinder 2.
The evaporation of the CO2 liquid requires a heat of evaporation, which can cool the vapor cylinder 2. The cooling of the vapor cylinder 2 causes the overall pressure to drop in the vapor cylinder 2. Accordingly, as CO2 liquid in the vapor cylinder 2 is preferentially vaporized and then dispensed with the pressure differential device 7 in the closed position, the pressure in the vapor container 2 decreases during operation of the system 10 until the pressure has reduced to a certain level that creates a pressure difference between the liquid container 1 and the vapor container 2 that is equal to or greater than the set point pressure of the pressure differential device 7 at which point the device 7 is triggered to open. Upon the pressure in the vapor container 2 dropping to below the certain level, the pressure differential device 7 is activated into the open position to allow transfer of CO2 fluid from the liquid container 1 to the vapor container 2. It should be noted that the shuttle valve 4 remains in the unbiased position (
CO2 fluid transfer into the vapor cylinder 2 occurs along conduit 13 until the pressure in the vapor cylinder 2 has increased to above a predetermined level so as to decrease the pressure difference between the liquid cylinder 1 and the vapor cylinder 2 below the set point pressure of the pressure differential device 7, at which point the pressure differential device 7 switches from open to the closed position. In this manner, the present invention establishes the set point pressure of the pressure differential device 7 to be an operating value that allows preferential depletion of CO2 liquid from the vapor cylinder 2, thereby reducing or eliminating the risk of over pressurization arising from accumulation of the CO2 liquid level in the vapor cylinder 2—a methodology not previously employed with currently utilized on-site CO2 dispensing systems.
The present invention has discovered that without use of the pressure differential device 7 in the manner described herein, during the supply of CO2 vapor product to the customer, CO2 in the liquid cylinder 1 vaporizes and flows into the CO2 vapor cylinder 2 and/or directly to the end-user, until a pressure equilibrium is established in both the liquid cylinder 1 and the vapor cylinder 2. Since the liquid cylinder 1 generally contains more liquid CO2 than the vapor cylinder 2, the evaporation rate of the CO2 liquid in the liquid cylinder 1 is typically faster than in the vapor cylinder 2. Consequently, more CO2 from the liquid cylinder 1 is observed to be dispensed to the customer or end user. As a result, the liquid CO2 in the vapor cylinder 2 may undergo a slower rate in depletion, which could cause accumulation in the vapor cylinder 2 during CO2 fluid transfer from the liquid cylinder 1 to the vapor container 2, as well as during subsequent filling operations. The net effect would be an increased risk of over pressurization in the vapor cylinder 2, as the vapor space of the vapor cylinder 2 is being reduced during operation.
As can be seen, in accordance with the principles of the present invention, the pressure differential device 7 limits CO2 vapor flow from the liquid container 1 into the vapor container 2 during use when the vapor container 2 contains liquid CO2. Specifically, when the vapor container 2 contains liquid CO2 (i.e., the vapor cylinder 2 is not liquid dry), the pressure differential device 7 limits the transfer of vapor CO2 flow from the liquid container 1 into the vapor container 2 until substantially all of the liquid phase CO2 in the vapor container has been vaporized and subsequently consumed or depleted. In one example, the present invention vaporizes at least 75 wt % of CO2 liquid in the vapor CO2 container prior to introducing CO2 liquid and/or CO2 vapor (collectively “CO2 fluid”) from the liquid CO2 container 1 to the vapor CO2 container 2. The present invention utilizes the pressure differential device 7 to isolate the vapor container 2 from the liquid container 1 under such operating conditions to allow the liquid CO2 in the vapor container 2 to be preferentially consumed before the CO2 vapor from the liquid container 1. In this manner, liquid CO2 is prevented from accumulating in the vapor container 2, which consequently minimizes the risk of CO2 overfill and over pressurization of the on-site two container system.
Referring to
The ability of the present invention to preferentially withdraw vapor product from the vapor cylinder 2 as opposed to the liquid cylinder 1 is demonstrated by the tests described in the following Examples.
The behavior of a conventional two cylinder CO2 dispensing system was evaluated. The vapor cylinder was not isolated from the liquid cylinder during use. The weight loss of the liquid cylinder and the weight loss of the vapor cylinder were monitored.
The behavior of an improved two cylinder CO2 dispending system was evaluated. The system was configured as shown in
The system of
The results indicate that the conventional dispensing system and method of Comparative Example 1 failed to preferentially consume CO2 from the vapor container, creating an operating scenario conducive for accumulation of CO2 liquid in the vapor container with subsequent or successive fills. The conclusion from the tests was that over pressurization was likely in the case of Comparative Example 1, but significantly reduced or eliminated with the system and method of Example 1; and that the inventive system was capable of not exceeding maximum permitted filling regulatory requirements as demonstrated in Example 2.
While it has been shown and described what is considered to be certain embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail can readily be made without departing from the spirit and scope of the invention. It is, therefore, intended that the present invention not be limited to the exact form and detail herein shown and described, nor to anything less than the whole of the invention herein disclosed and hereinafter claimed. For example, pressure gauges, pressure relief valves and pressure differential device may be integrated or built into the valve 4. Additionally, valve 4 may be connected to the valve of liquid container 1 through a flexible hose or it may be installed on liquid container 1 directly without using a cylinder valve.
Additionally, the pressure regulator 9 that dispenses CO2 to an end-user or customer may be integrated or built into the shuttle valve 4. Alternatively, the pressure regulator 9 may be integrated to the vapor cylinder valve.
Other modifications and/or instrumentation are also contemplated by the present invention in addition to or independently to achieve similar control for minimizing liquid inventory within the vapor container. Specifically, the present invention can incorporate a means of measuring the liquid level in the vapor container and not permit fill when the liquid level is above a certain value. Level detection may be achieved using capacitance level gauges or optical level detection. By way of example, the monitoring of liquid level of CO2 in the vapor cylinder 2 may be used as an additional safety feature during fill and the basis for controlling the amount of CO2 fluid charged into the system 10. Under normal operation, it is expected that the target fill pressure is achieved prior to the liquid level in the vapor cylinder 2 attaining a predetermined maximum liquid level. However, in the event that the system 10 is not operating under normal operating conditions during fill such that a predetermined maximum liquid level in the vapor cylinder 2 is attained that can create a hazardous condition of overpressurization, the system 10 can shut off upon reaching such predetermined maximum liquid level in the vapor cylinder 2 even though the target fill pressure has not been attained. Specifically, when the liquid level in the vapor container 2 reaches a pre-determined maximum level regardless of whether the target fill pressure has been attained, the filling operation will stop which further ensures the system 10 does not over fill. Alternatively the liquid level in the vapor container 2 may be used solely to control the fill, such that once the liquid level in the vapor cylinder 2 reaches the predetermined maximum liquid level, the fill can stop. Either control means ensures the filling operation does not continue based on attaining a predetermined maximum liquid level in the vapor cylinder 2.
In yet another example, if the fill flow rate is lower than the normal or expected fill rate, more liquid CO2 may be allowed over time (i.e., during the course of subsequent and/or successive refills) to transfer from the liquid container 1 into the vapor container 2 than may occur at the normal fill rate. The methodology of monitoring liquid level in the CO2 vapor container 2 may ensure that the filling is shut off upon detecting the predetermined maximum liquid level in the vapor cylinder 2. Still further, before filling occurs, there may be a scenario where the liquid level in the vapor cylinder 2 is at the predetermined maximum level such that filling would not be permitted to ensue. Such scenarios represent departure from normal operation conditions which can be remedied by monitoring and detecting CO2 liquid level in the vapor container 2.
Besides the level monitoring techniques described herein, the present invention also contemplates thermal imaging techniques and temperature sensitive strip techniques as the means to monitor liquid CO2 liquid levels in the vapor cylinder 2 during the filling operation when the CO2 liquid is relatively lower in temperature than that of the cylinders 1 and 2.
In one embodiment, a two-cylinder system of the present invention in which both cylinders are the same size is operated such that the maximum CO2 liquid level in the vapor cylinder 2 during fill may be controlled to be no more than 55%, preferably no more than 45% and more preferably no more than 35% based on total volume of CO2 in the system 10. The exact liquid level in the vapor cylinder 2 can vary based on the size of each of the two cylinders 1 and 2, respectively. If the vapor cylinder 2 is larger in volume capacity than the liquid cylinder 1, then the liquid level in vapor cylinder 2 can be relatively higher, provided that the total amount of CO2 in the system can't be over 68 wt % by water weight under any conditions.
Still further, load cells may be placed underneath the vapor container 2, and the fill of the liquid container 1 will be prevented unless the load cells indicate the weight of the vapor container 2 with little or no liquid phase present, e.g., tare weight plus 10 lbs. maximum for a 43 L container. The 43 L container can have 14 lb CO2 even if liquid dry. The amount of CO2 allowed in the vapor cylinder can depend, at least in part, on the size of the liquid and vapor containers. For example, if the 43 L container is used for both liquid and vapor containers, 1 and 2, respectively, the vapor container 2 preferably has a maximum of approximately 40 lb CO2.
In yet an alternative design, an independent port and dip tube may be added to vent the liquid CO2 present in the vapor container during fill. The depth of the dip tube is predetermined so as to control and limit the level of liquid CO2 in the vapor cylinder. The vent line may be routed back to the CO2 source (e.g., CO2 truck) instead of open to the atmosphere. Still further, the present invention may also be modified to warm the vapor container to preferentially vaporize its CO2 liquid inventory contained therein.
In another modification, a residual pressure control device 15, as shown in
It should be understood that the present invention has versatility to be employed in various applications. For example, the on-site system of the present invention can be utilized in beverage, medical, electronics, welding and other suitable applications that require on-site CO2 delivery. The present invention is also capable of filling and dispensing CO2 at any CO2 purity grade.
As has been described, the present invention contemplates several means of ensuring that sufficient headspace is provided by the vapor container. Rather than control the fill state of the liquid container as is typical with conventional systems, the present invention focuses on preserving the headspace of the vapor container by limiting CO2 fluid flow to the vapor container from the liquid container during customer usage and/or, by directly or indirectly evaluating the CO2 liquid inventory of the vapor container. As a result, the design of the present invention is aimed to reduce the likelihood of accumulating liquid CO2 in the vapor container that can possibly result in insufficient vapor headspace which is unable to accommodate liquid expansion from the liquid container after filling of the liquid container with refrigerated and pressurized CO2 liquid. As such and in this manner, the present invention represents a significant departure from conventional systems which solely focused on the contents of the liquid container, but failed to provide a solution for handling an increase in specific volume (e.g., ˜30%) as a result of the temperature increase of the liquid CO2, for example, from 0 deg C. to 20 deg C. or higher.
In yet another embodiment of the present invention, prior to filling the CO2 containers of
The safety interlock fill system 400 is indicated by dotted line in
A fill manifold 474 is connected to the source vessel 473. The fill manifold 474 preferably includes a network of conduits to allow leak checking and pressurization with CO2 vapor 471 and then subsequent CO2 liquid filling into downstream containers. The fill manifold 474 includes a vapor supply conduit 477 that is used to perform the pre-fill integrity checks (e.g., leak check and pressurization of the fill manifold 474) as will be explained below.
A pump 402 is situated along a liquid supply CO2 conduit 478. The pump 402 is used to pressurize liquid CO2 472 withdrawn from bottom portion of source vessel 473. Such pressurization may be required when filling containers with CO2 liquid 472 withdrawn from source vessel 473 along the high pressure conduit 440 as well as when replenishing the low pressure containers located downstream of low pressure conduit 450. The safety interlock system 400 also includes a controller 470, preferably a programmable logic controller (PLC). To allow the PLC 470 to perform the integrity checks, the PLC 470 receives various inputs, including a first set point equal to the unallowable reduction in pressure of the CO2 vapor in the fill manifold 474 during a predetermined time period that the leak checking occurs; a second set point equal to the predetermined lower pressure of the CO2 vapor in the fill manifold 474 below which dry ice may form; and a third set point equal to the predetermined upper pressure of the CO2 vapor in the fill manifold 474 above which reversible flow of vapor CO2 from the high pressure containers into the fill manifold 474 may be occurring. Such reversible flow of the vapor CO2 is not desirable, as subsequent venting of the fill manifold 474/fill hose 415 can cause CO2 from the high pressure containers to be vented.
An example of a pre-fill integrity check utilizing the control methodology 500 in
The pressure in the fill manifold 474 and high pressure conduit 440 extending up to high pressure containers can be measured by one or more of several pressure transducers, including pressure transducer 403 in liquid supply conduit 478; and pressure transducer 412 positioned downstream of flow meter 410. The pressure transducers 403 and 412 continuously monitor the pressure in the various conduits during the pre-fill integrity checks. Signals associated with each of the pressure transducers 403 and 412 are transmitted to PLC 470, which calculates whether the fill manifold 474 and high pressure fill conduit 440 extending up to high pressure containers have undergone a pressure change or drop during a certain time period (e.g., 30 sec) as indicated in step 503. Having calculated the pressure change, the PLC 470 determines whether the pressure change in the fill manifold 474 and the high pressure conduit 440 up to the containers, if any, is less than the first set point (step 504). Additionally, the PLC 470 checks whether the pressures are higher than the predetermined lower pressure of the CO2 vapor (e.g., higher than 61 psig), and lower than the predetermined upper pressure of the CO2 vapor in the fill manifold 474 (step 504) (e.g., 300-350 psig).
Should the PLC 470 determine that the fill manifold 474 and high pressure conduit 440 extending up to the high pressure containers has (i) a leak equal to or higher than the first set point; or (ii) a pressure below the predetermined lower pressure (second set point); or (iii) a pressure above the predetermined upper pressure (third set point), then the PLC 470 prevents subsequent filling of CO2 liquid 472 from source vessel 473 into high pressure container (step 505) and displays an alarm for troubleshooting. Next, the control methodology 500 allows a technician to determine whether the system 400 of FIG. 4 has a leak (step 506). If a leak is determined along any of the various conduits inside the confined area where the containers are located or a leak is determined by virtue of the high pressure containers not connected to their respective conduit, then a technician fixes the leak (step 507). A leak may occur, by way of example, as a result of the containers not connected to the fill box though which high pressure conduit 440 communicates with the containers located inside a building or other confined area. If no leak is detected, the pressurization of the system has likely failed as a result of CO2 vapor in fill manifold 474 flowing along conduit 440 and into containers as a result of the containers depleted to a point that the containers have a container pressure less than the pressure in the fill manifold 474 and high pressure conduit 440. As such, the high pressure containers are checked to determine whether they are depleted to a level where the pressure in the container is 61 psig or less (step 508). If such condition is verified, then the system 400 proceeds to fill such container with CO2 vapor until the pressure in the container is at least 61 psig or slightly higher (step 509). In this manner, the fill manifold 474, high pressure conduit 440 and containers are above a predetermined lower pressure at which the onset of dry ice formation is avoided during the subsequent filling of CO2 liquid.
When the leak checks and pressurization criteria are met, the control methodology 500 is designed to allow filling of liquid CO2 to begin. Manual valve 401 is for maintenance purposes preferably kept normally in the open position. Three-way automated valve 411 is normally closed towards liquid supply conduit 478 but normally open towards valve 420 and 111. Three-way automated valve 411 receives a signal from PLC 470 that causes it to open towards liquid supply conduit 478. Pump 402 may be primed prior to the liquid CO2 fill of high pressure containers by circulating liquid CO2 back to source vessel/tank 473 via valve 429. The PLC 470 sends signals to the other control valve 407 along the liquid supply conduit 478 and control valve 413 along high pressure conduit 440 to cause each to open. CO2 liquid 472 can be withdrawn from source vessel 473 and then pressurized by pump 402 as it flows along liquid supply conduit 478, high pressure conduit 440 and then into a high pressure container at the customer site (step 510).
The PLC 470 can be inputted with a predetermined lower flow rate; a predetermined upper flow rate; predetermined lower fill pressure and a predetermined maximum fill time. As filling into container occurs, the filling process is monitored as set forth in step 511. The CO2 liquid is introduced when the PLC 470 determines that the (i) fill pressure (as measured by pressure transducers 403 and 412 with corresponding signals sent back to PLC 470) is greater than the predetermined lower pressure to avoid leakage occurring during fill; (ii) the flow rate (as measured by flow meter 410 with corresponding signal fed back to PLC 470) is greater than the predetermined lower flow rate to ensure there is no blockage in the conduit or any other problem; (iii) the flow rate (as measured by flow meter 410 with corresponding signal fed back to PLC 470) is less than the upper flow rate to ensure there is no problem such as unexpected high pump speed due to higher motor speed; and (iv) the fill time does not exceed the predetermined maximum fill time (as may occur if the cylinder is not receiving CO2 liquid). If all of the conditions in step 511 are met, the filling continues to completion until the PLC 470 determines that container increases to a predetermined container pressure (i.e., fill pressure), at which point the PLC 470 sends a signal to pump 402 to automatically shut down, and the three-way valve 411, which is open towards pump 402, closes so that filling is stopped (step 512). The fill manifold 474 and the high pressure conduit 440 which, includes the line extending from quick connector 430 up to the shuttle valve 4 (
Should one or more of the filling conditions not meet required set points at step 511 as determined by the PLC 470, which compares its inputted set points with corresponding fill conditions, then the filling operation is automatically terminated and a corresponding display message and/or alarm may appear on the display panel of the PLC 470 indicating a need to troubleshoot (step 515). After the issues are fixed, step 501 is started to re-initiate the integrity pre-fill checks.
In another example, pre-fill integrity checks and filling may occur for a low pressure system where filling of CO2 liquid occurs into a container such as an insulated microbulk container that can handle pressures less than 350 psig, such as, by way of example, 200-300 psig. System 400 is configured to fill through low pressure conduit 450 having quick-connect conduit 428 connected to the low pressure containers as shown in
Other variations and additional features are contemplated. For example, the present invention can manually perform the pre-fill integrity checks if desired. In such a scenario, manual valve 117 would open as opposed to control valve 429. Additionally, valve 420 may be configured as manual valve and the filling of CO2 liquid into low pressure containers can occur by free flow from source vessel 473 by opening manual valve 420. No pump 4 is required. CO2 liquid 472 is withdrawn from source vessel 473 and free flows into liquid supply conduit 479 and then travels pass flow meter 410 and downwards through open valve 122 and into low pressure conduit 450. Still further, a manual mode can allow an end-user to operate any automated valve of
A discharge pressure control device 428 which is set higher than the predetermined fill pressure but lower than the pressure rating of the high pressure fill system can be employed. The discharge pressure control device 428 opens when the pressure reaches its set value which returns the excess liquid CO2 to source vessel 473 when the pressure in fill manifold 474 and high pressure conduit 440, extending up to the containers, reaches the predetermined fill pressure but the pump 402 has not stopped. The PLC controller 402 can also be programmed to release the excess liquid CO2 to source vessel 473 via valve 429. Still further, as a means to further enhance safety during filling at step 511, the value of pressure relief devices shown in
Still further, pressure gauges 405, 419 and 427 can be used for local observation during the pre-filling and filling operations.
The PLC 470 may be inputted with various values for the set points when performing the pre-fill integrity checks. In one example, the first set point is about 5 psig or less; the second set point is about 61 psig; the third set point is about 350 psig or higher. With regards to the filling operation, the PLC may also be inputted with various values. In one example, the predetermined lower flow rate is 10 pounds per minute (lbpm); the predetermined upper flow rate is about 40 lbpm; the predetermined maximum fill time is about 7 minute; and the predetermined pressure into the container at completion of filling is about 1200 psig (i.e., filling stops when fill pressure has reached about 1200 psig).
It should be understood that system 400 represents one type of system for carrying out the pre-fill integrity checks in accordance with the present invention. The control methodology 500 contemplates other types of flow, valving and instrumentation configurations for carrying out the pre-fill integrity checks of the invention. For example, the pneumatic control valves can be replaced with solenoid valves. Still further, a single supply conduit for CO2 liquid filling can be used when filling into either low pressure or high pressure containers. Additionally, other values for set points can be used to carry out the pre-fill integrity checks. For example, the predetermined lower pressure limit may be inputted into the PLC 470 as 100 psig to ensure there is enough of a safety cushion on the lower pressure operating regime that ensures the formation of dry ice in the fill manifold 474 and all conduits, including conduits 440 and 450, is avoided.
Although the embodiments have been described in connection with onsite filling at a customer site, it should be understood that the process and associated control methodology of the present invention is applicable to CO2 filling at a plant. Further, the control methodology and pre-fill integrity checks can be applied to other fluids besides CO2. In particular, the present invention is particularly suitable for fluid fill processes where the receiving containers are located in a place where the operator conducting the filling has no visibility of the receiving containers. Still further, although the embodiments have described pressure-based filling, it should be understood that the methodology described herein may be used for filling based on weight. A scale can be employed for the weight fill and the signal form the scale can transmitted to controller 470.
The present invention avoids many of the problems encountered when filling CO2 liquid into containers located inside a building or other confined area on a customer site that are not visible when operating a CO2 liquid filling system, such as inadvertent release of CO2 liquid into the confined area as a result of the containers not connected to the fill hose or leakage of the conduit between the fill box and containers. Further, the present invention ensures dry ice formation is avoided during filling by ensuring the fill manifold and containers are above 61 psig.
The present application claims priority to U.S. Application Ser. No. 62/315,434 filed Mar. 30, 2016 and U.S. Application Ser. No. 62/438,746 filed Dec. 23, 2016, the disclosures of which are hereby incorporated by reference in their respective entireties for all purposes.
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