Patent Application
20170030522
The invention relates to a filling station adapted for filling a cryogenic refrigerant from a supply tank to a receiver tank. The filling station comprises a flash tank positioned between the supply tank and the receiver tank, this flash tank being adapted to de-pressurize the liquid cryogenic refrigerant that is transferred from the supply tank to the flash tank, resulting in the formation of a liquid cryogenic refrigerant phase and a vapour cryogenic refrigerant phase within the flash tank, and being adapted to phase separate the liquid and the vapour cryogenic refrigerant phase. The filling station furthermore comprises a pump positioned between the flash tank and the receiver tank, this pump being adapted for pumping the liquid cryogenic refrigerant out of the flash tank to the receiver tank when being in operation.
In the field of maintaining goods at low temperatures below environmental temperature, i.e. either frozen at −21° C. or fresh at +3° C., when being disconnected from a mains supply or a reefer, more especially during transport of these goods, several different solutions have been proposed in the prior art. Some of these comprise the use of large trucks and trailers having tanks (=transportable or mobile tanks) which are supplied with a cryogenic refrigerant, for instance liquid CO2, as is the case in a preferred embodiment of the present invention. This cryogenic refrigerant is thus provided in a thermally insulated transportable tank mounted inside a refrigeration unit or at the chassis of the truck. Inside this refrigeration unit, the cryogenic refrigerant is evaporated in an air/refrigerant heat exchanger. The cooled air from this heat exchanger is then blown into the goods compartment of the vehicle.
In order to fill this mobile tank with liquid cryogenic refrigerant, preferably a filling station is used. An example of a filling station for filling of cryogenic refrigerant fluids, in particular liquid CO2, from a storage tank to a mobile tank for instance located on a vehicle, is described in EP 1 463 905 in the name of Yara International ASA and Thermo King Corporation. The filling station as disclosed therein comprises the following three main components:
These three main components are interconnected by means of liquid CO2 piping from the storage tank to the phase separator with a branch pipe to the dispenser, and a gas pipe from the dispenser with branch pipes to the phase separator and the storage tank respectively.
Inside this pressure/flow control column, the liquid CO2, during the filling of the mobile tank, is de-pressurized, phase separated and measured. This pressure/flow control column has a height of 5 meter and a diameter of approximately 100 mm. The pressure inside the storage tank is normally higher than in the mobile tank. Therefore, the pressure inside the column is reduced by using a back pressure regulator. The pressure reduction causes the liquid CO2 to flash, and it produces a mixture of liquid and vapour phase inside the column. The liquid and vapour phase are then separated in a phase separator and the liquid phase going to the mobile tank is measured. The vapour phase is released to the atmosphere or may alternatively, if it is economically practical to do so, be recompressed and liquefied and put back into the storage tank. In order to allow the liquid CO2 to flow into the mobile tank, the pressure/flow control column with the phase separator is located on a higher level than the mobile tank. The disadvantage thereof however is that the filling speed of the mobile tank is too low.
US 2011/0297273 A1 discloses a method for filling a tank with a cryogenic liquid from a storage unit during which at least part of the cryogenic liquid is transformed into gas in the tank and at least part of the gas formed is being discharged. The method includes detection of the presence of cryogenic liquid in the gas being discharged and thereby determining when the tank is full.
In order to raise the filling speed of the mobile tank, it is already known to replace the pressure/flow control column with a small flash tank serving as the phase separator that is installed between the storage tank and the mobile tank. This small flash tank has a height of 1 meter and a diameter of between 300 and 350 mm. The liquid CO2 is brought from the flash tank into the mobile tank using a pump. This known CO2 filling station however suffers from the disadvantage that it takes quite some time, i.e. around 1 to 2 minutes, to start filling the receiver tank.
Therefore, there exists the need to provide a filling station for filling liquid cryogenic refrigerant from a supply tank to a receiver tank, wherein the filling operation of the receiver tank is started more quickly.
According to the invention, a filling station adapted for filling of liquid cryogenic refrigerant from a supply tank to a receiver tank is provided, the filling station comprising
The term “at a predetermined minimum” is meant to include at or above a predetermined minimum.
In one aspect of the present invention the predetermined minimum is 10% of the size of the flash tank. The size of the flash tank is measured as the maximum mass of cryogenic refrigerant that the flash tank can contain.
In a further aspect of the present invention the predetermined minimum is 30% of the size of the flash tank.
This takes care that after connecting the filling hoses of the filling station to the receiver tank, and after a check of the pressure of the vapour phase in the receiver tank—possibly leading to an adjustment of the pressure of the vapour phase in the receiver tank—, the filling procedure of the receiver tank can start. This only takes about a maximum of ten seconds in order to start the filling the receiver tank.
The filling station according to the invention furthermore is arranged to keep the level of the flash tank below a predetermined maximum.
In one aspect of the present invention the predetermined maximum is 90% of the size of the flash tank. The size of the flash tank is as above measured as the maximum mass of cryogenic refrigerant that the flash tank can contain.
In a further aspect of the present invention the predetermined maximum is 80% of the size of the flash tank. Alternatively the predetermined maximum is in the range 80-90%.
In a favourable embodiment of a filling station according to the invention, the filling station comprises one or more exhaust ball valves adapted for blowing-off excess cryogenic refrigerant vapour out of the flash tank when the pressure in the flash tank is above a predetermined pressure limit and for blowing-off excess cryogenic refrigerant vapour out of the receiver tank when the pressure in the receiver tank exceeds a predetermined pressure limit during the filling process of the receiver tank.
The predetermined pressure limit of the flash tank is preferably between 7 and 10 bar. It is remarked that the working pressure of the flash tank is around 8 bar. When however one or more valves are opened, there is a pressure drop in the flash tank.
In an advantageous embodiment of a filling station according to the invention, the filling station comprises a silencer adapted to reduce the noise of the blowing-off of the excess vapour cryogenic refrigerant out of the flash tank and the receiver tank.
In a preferred embodiment of a filling station according to the invention, the filling station comprises cryogenic refrigerant vapour piping between the supply tank and the receiver tank, wherein the filling station comprises a liquid sensor that is located at the end of the cryogenic refrigerant vapour piping between the supply tank and the receiver tank, this liquid sensor being adapted to detect liquid cryogenic refrigerant entering the cryogenic refrigerant vapour piping when finishing the filling of the receiver tank.
In a more preferred embodiment of a filling station according to the invention, the filling station comprises a housing, wherein the liquid sensor is located inside the housing of the filling station.
In an advantageous embodiment of a filling station according to the invention, the filling station comprises purge means that are adapted to purge the cryogenic refrigerant vapour piping in order to remove liquid cryogenic refrigerant, that may have entered the cryogenic refrigerant vapour piping when finishing the filling of the receiver tank, out of the cryogenic refrigerant vapour piping.
In a more advantageous embodiment of a filling station according to the invention, the filling station comprises a gas dispenser hose, a holder for the gas dispenser hose and a controller that is arranged for receiving a signal from the holder for the gas dispenser hose and for sending a signal to the purge means, wherein at the moment the gas hose is placed on the holder after the filling of the receiver tank has ended, the holder sends a signal to the controller that at its turn sends a signal to the purge means to start the purging operation of the cryogenic refrigerant vapour piping. These purge means are especially advantageous if a high number of sequential fillings have to be performed the one directly after the other.
The purge means preferably comprise a purge valve located in the cryogenic refrigerant vapour piping between the supply tank and the receiver tank.
In a favourable embodiment of a filling station according to the invention, the filling station comprises recirculation means that are arranged for recirculating cryogenic refrigerant liquid out of the flash tank towards the pump in order to cool down the pump.
More preferably, the flash tank comprises
Another disadvantage of the known filling stations having a small flash tank as described above is that they are having problems with the exhaust valves causing the interruption of the filling of the mobile tank only after 10 seconds, which is undesirable because every time the filling procedure of the mobile tank has to be restarted.
There therefore exists the need to provide a filling station for filling liquid cryogenic refrigerant from a supply tank to a receiver tank, having a sufficient filling speed and constantly filling the receiver tank without interruption of the filling process of this receiver tank.
Thereto, in a favourable embodiment of a filling station according to the invention, the flash tank has a size and the pump has an outflow of liquid cryogenic refrigerant being such that the ratio between the size of the flash tank and the outflow of liquid cryogenic refrigerant out of the pump is equal to or more than 1, wherein the size of the flash tank is defined as the maximum mass of cryogenic refrigerant the flash tank can contain and the outflow of liquid cryogenic refrigerant out of the pump is measured in mass per minute.
The size of the flash tank is measured as the maximum mass of cryogenic refrigerant that the flash tank can contain. This mass is normally measured in kg which is usual for defining the size of tanks containing liquefied gas. Accordingly the maximum size of the flash tank can be expressed as the maximum weight of cryogenic refrigerant that can filled into the flash tank.
Such a filling station has an adequate filling speed and is not interrupted during the filling process of the receiver tank.
In an advantageous embodiment of a filling station according to the invention, the ratio between the size of the flash tank and the outflow of the liquid cryogenic refrigerant out of the pump is between 1 to 5.
The bigger the ratio between the size of the flash tank and the outflow of liquid cryogenic refrigerant out of the pump, the better the stability of the filling station. It is however important to notice that, for economic reasons and for reasons of limited available space for the filling station, the flash tank has to have a size such that it fits into the housing of the filling station.
In a preferred embodiment of a filling station according to the invention, the supply tank is a stationary storage tank that is under pressure between 12 bar and 20 bar.
In an advantageous embodiment of a filling station according to any the invention, the receiver tank is a mobile tank that is under pressure between 7 bar to 10 bar. This mobile tank preferably is located on a vehicle such as a truck.
The cryogenic refrigerant preferably is CO2.
Goods to be kept cold or frozen can be different types of products like for instance food, pharmaceutical products and biological products. Such products will typically have an expiration date, and must be kept at a specific low temperature prior to said expiration date. In order to comply with this requirement during loading from a facility, as well as shipping and transport to a destination, the products are stored in a cooled goods compartment that is cooled using cold air originating from a cryogenic refrigerant, preferably liquid CO2 that is stored in a thermally insulated receive tank.
In order to fill the thermally insulated receiver tank present on the vehicle, also called the mobile tank, with liquid CO2, a CO2 filling station is used. A preferred embodiment of a filling station 1 for delivering liquid CO2 as the cryogenic refrigerant to a mobile tank (not shown in the FIGURE) according to the invention is shown in
The stationary storage tank is under a pressure of 12-20 bar, while the mobile tank is under a pressure of 7-10 bar. The working pressure of the mobile tank preferably is 8 bar. This pressure however drops when one or more valves of the filling station 1 are opened. In order to cope with the pressure difference between the storage tank and the mobile tank, a flash tank 2 is installed between the storage tank and the mobile tank. The flash tank 2 serves as a phase separator to de-pressurize the liquid CO2 that is transferred from the storage liquid CO2 tank to the mobile liquid CO2 tank. Because of this de-pressurization, a liquid CO2 phase 21 and a vapour (gas) CO2 phase 22 are formed in the flash tank 2, which are phase separated in the flash tank 2. The vapour CO2 phase 22 is substantially located in the top part 25 of the flash tank 2, while the liquid CO2 phase 21 is substantially located in the bottom part 26 of the flash tank 2.
As can be seen on
The dispenser system comprises three dispenser hoses (not shown on the FIGURE) that are connectable by means of quick connectors 61, 62, 63 to the mobile tank, i.e.
Each of the quick connectors 61, 62, 63 is provided with an anti-tow away-system, meaning that, when the mobile tank of for instance a truck is full, and the driver of the truck drives away without disconnecting one or more of the hoses, the connection will break without loss of CO2.
The dispenser system is furthermore provided with a holder (not shown on the FIGURE) that is arranged to releasably hold the three dispenser hoses as disclosed above.
The main components of the filling station 1 as listed above are interconnected by means of liquid CO2 piping 31, 32, 33, 34 as well as CO2 gas piping 91, 93, 94 that are provided with different valves.
Between the liquid CO2 outlet 41 from the storage tank and the quick connector 61, liquid CO2 piping 31, 32, 33, 34 extends.
The flash tank 2 is located between a first part 31 of the liquid CO2 piping and a second part 32 of the liquid CO2 piping.
The pump 5 is positioned in the second part 32 of the liquid CO2 piping extending between the flash tank 2 and the first quick connector 61. This pump 5 is adapted for pumping the liquid CO2 out of the bottom part of the flash tank 2 to this first quick connector 61.
Between the top part of the flash tank 2 and the second liquid CO2 piping part 32, a third part 33 of the liquid CO2 piping part is provided. In this third liquid CO2 piping part 32, preferably a recirculation valve 15 is provided that is arranged to allow recirculation of liquid CO2 from the bottom part of the flash tank 2 to the pump 5 in order to cool down the pump 5. In the second liquid CO2 piping part 32, after the pump 5, a flow meter 8 is provided that is arranged to measure the outflow of the liquid CO2 out of the pump 5. In order to measure correctly the amount of liquid CO2 flowing out of the pump 5, the liquid CO2 must be 100% liquid and also be free of gas bubbles. In order to ensure that 100% liquid CO2 is being pumped out of the pump 5, in the second part 32 of the liquid CO2 piping, a temperature sensor 81 is provided that is arranged for measuring the temperature of the liquid CO2 that is flowing out of the pump 5 and a pressure transmitter 82 is provided that is adapted for measuring the pressure of the liquid CO2 pumped out of the pump 5. For instance, for a pressure of the liquid CO2 between 8 and 10 bar, the temperature of this liquid CO2 has to be between −40° C. and −45° C. in order to be sure that 100% liquid CO2 is obtained. If the temperature is higher, then no 100% liquid CO2 is pumped out of the pump 5. In the third part of the liquid CO2 piping part 33, a temperature sensor 310 is arranged to measure the temperature of the CO2 gas flowing through the recirculation valve 15.
As can be seen in
In the fourth part 34 of the liquid CO2 piping, a safety valve 181, as well as a pressure transmitter 182 are provided, this pressure transmitter 182 being adapted to measure the pressure in the fourth part 34 of the liquid CO2 piping and a pressure indicator 183 adapted to indicate the pressure measured by this pressure transmitter 182. On the basis of the pressure measured by this pressure transmitter 182 and read on the pressure indicator 183, it is decided whether the valve 14 in the connection piping 13 has to be opened allowing the liquid CO2 piping to be put on the pressure of the CO2 gas piping (also called pre-tensioning of the liquid CO2 piping).
As can be seen in
Between the CO2 gas outlet 42 from the storage tank and the CO2 gas return hose 62 that is adapted to be connected to the mobile tank, CO2 gas piping 91, 93 and 94 extends.
This CO2 gas piping that extends between the CO2 gas outlet 42 from the storage tank and the CO2 gas return hose 62 is dividable in three parts:
The exhaust valve 104 as described above is also connected with the second part 93 of the CO2 gas piping in order to allow blowing-off of CO2 gas entering the second and third part 93, 94 of the CO2 gas piping when filling the receiver tank. The silencer 114, which is already mentioned above, also takes care that the noise produced during the blowing-off of CO2 gas while filling of the receiver tank is reduced.
Each part of the CO2 gas piping where liquid CO2-inclusion can occur has to be provided with an emergency valve. This is the case in the first, second and third part 91, 93 and 94 of the CO2 gas piping. The following safety valves are arranged:
These safety valves 122, 124, 126 are closed during the normal operation of the filling station 1.
The following maintenance valves are provided in the CO2 gas piping:
At the level of the third safety valve 126, a pressure transmitter 127 and a pressure indicator 128 are provided. The pressure transmitter 127 is adapted to measure the pressure in the third part 94 of the CO2 gas piping in order to check if there is still pressure on the pipework. The pressure indicator 128 is arranged to indicate the pressure measured by the pressure transmitter 127.
As can be seen on
At the end of the fourth part 94 of the CO2 gas-piping, purge means, preferably in the form of a purge valve 16, are provided, this purge valve 16 being arranged to get liquid CO2 out of the CO2 gas piping 94, this liquid CO2 entering the CO2 gas piping 94 when the filling operation of the receiver tank is finished (this being the signal that the receiver tank is full). In order to detect liquid CO2 entering the fourth part 94 of the CO2 gas piping when finishing the filling operation of the receiver tank, a liquid sensor 160 is provided. This liquid sensor 160 is preferably located inside the housing of the filling station 1. The purging process performed by this purge valve 16 works as follows: after the receiver tank is full (or after the liquid sensor 160 detected liquid CO2 in the fourth part 94 of the CO2 gas piping), the liquid CO2 filling hose will be put back by the operator on its holder. At that moment, a signal is sent to a controller (not shown on the FIGURE), resulting in the controller at its turn sending a signal to the purge valve 16 allowing the purge valve 16 to operate and to purge the CO2 gas piping in order to remove the liquid CO2 out of it.
The flash tank 2 has a size and the pump 5 has an outflow of liquid CO2 being such that the ratio between the size of the flash tank 2 and the outflow of the pump is more than 1 and more preferably between 1 and 5.
The flash tank 2 is equipped with a level control unit 205 that is arranged to keep the level of the liquid CO2 within the flash tank 2 above a predetermined minimum and preferably also below a predetermined maximum. In this way, the flash tank 2 is always at least partially filled, resulting in a reduced starting time of the filling process of the mobile tank. The level control unit 205 is measuring the content of the liquid CO2 within the flash tank 2.
Between the bottom part 26 and the top part 25 of the flash tank 2, a piping 20 extends which is arranged with a valve 200. Below the valve 200 a branch line with a separate normally open valve 202 is arranged. A further branch line is arranged on the line 20 above the valve 200, this branch also comprises a normally open valve 201. The level control unit 205 is arranged between these two branch line valves 202 and 201. A pressure indicator 203 that is arranged to indicate the pressure in the flash tank 2 is connected to the level control unit 205. Further a pressure transmitter 204 is arranged to transmit the pressure or pressures measured by the level control unit 205.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20131734 | Dec 2013 | NO | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/079020 | 12/22/2014 | WO | 00 |
