SUPPLY OF HIGH-PRESSURE CO2 TO A USER STATION BY ADDING A LIQUEFACTOR AT THE USAGE POINT

Abstract

An installation for supplying a user station with pure or substantially pure liquid CO.sub.2 at high pressure, preferably in the range 50-60 bar, from a liquid CO.sub.2 source, the installation comprising means for compressing the liquid CO.sub.2 that are positioned between the source and the user station, wherein a liquefier for the fluid flowing between the source and the compression means is positioned at the inlet of the compression means.

Claims

1. An installation for supplying a user station with pure or substantially pure liquid CO.sub.2 at high pressure in the range of 50-60 bar, the installation comprising: a. means for compressing the liquid CO.sub.2 that are positioned between the source and the user station, b. a liquefier for the fluid of CO.sub.2 flowing between a source and the compression means is positioned at an inlet of the compression means.

2. The installation according to claim 1, wherein the liquefier implements a heat exchange between a cold fluid and the fluid of CO.sub.2, the cold fluid comprising: glycolated water, or cold water coming from a network of iced water.

3. The installation according to claim 1, wherein the liquefier is implemented using the following means: a refrigeration unit configured to produce cold water at a temperature within a range of 5? C. to 15? C., via a coil, a tank containing water or another medium, and two coils: a first coil in which a refrigerant liquid flows from the refrigeration unit to cool the water or the medium in which this coil is immersed, said water thus being usable as an intermediary to convey cooling power to the fluid CO.sub.2 to be cooled or liquefied coming from said CO.sub.2 source, a second coil able to receive a flow of two-phase gas-liquid high-pressure fluid CO.sub.2, the cold power transferred by the surrounding cold water or the surrounding cold medium being transferred to the fluid CO.sub.2 flowing in this second coil and enabling this fluid to be cooled and to liquefy the gas phase thereof, before conveying this fluid thus cooled towards said user station.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Further features and advantages of the invention will become apparent from the description hereinafter of embodiments, which are given by way of illustration but without any limitation, the description being given in relation with the following attached figures:

[0049] FIG. 1 shows a partial schematic view of an installation suitable for implementing the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0050] FIG. 1 attached is a partial schematic view of an installation suitable for implementing the present invention, including the following installation elements: [0051] i) C: a buffer tank containing a liquid L (water or glycolated water, for example)

[0052] The tank is provided with two coils to enable heat exchanges: [0053] Between the CO.sub.2 and the liquid medium, [0054] Between the refrigerant fluid (coming from the refrigeration unit GF) and the liquid medium.

[0055] (Reference sign S provides an example of coils that may be used in the tank C) [0056] j) GF: a refrigeration unit [0057] k) FG-E: CO.sub.2 to be cooled, to be liquefied (therefore hot) flowing from the CO.sub.2 source towards the tank C.

[0058] The CO.sub.2 is high-pressure CO.sub.2, usually at 50-60 bar and ambient temperature.

[0059] The CO.sub.2 is therefore liquid CO.sub.2 having a small quantity of unwanted gas caused by the ingress of heat occurring upstream. [0060] l) FG-S: Cooled CO.sub.2 flowing from the tank C towards the user station, a pure liquid (the unwanted gas has been liquefied). [0061] m) FF-F: The cold refrigerant fluid flowing from the refrigeration unit towards the tank. [0062] n) FF-C: The heated refrigerant fluid flowing from the tank towards the refrigeration unit.

[0063] The invention therefore relates to an installation for supplying a user station with pure or substantially pure liquid CO.sub.2 at high pressure, preferably in the range 50-60 bar, from a liquid CO.sub.2 source, the installation comprising means for compressing the liquid CO.sub.2 that are positioned between the source and the user station, characterized in that a liquefier for the fluid flowing between the source and the compression means is positioned at the inlet of the compression means

[0064] An example application and implementation calculations of the invention are described below.

[0065] The example relates to a required high-pressure CO.sub.2 flow of D=60 kg/h. A supply between 55 and 60 bar is therefore required.

[0066] In this example, the CO.sub.2 is at a temperature of between 15? C. and 20? C., which corresponds to a point on the CO.sub.2 gas-liquid (or liquid-vapour) equilibrium (Mollier diagram).

[0067] The CO.sub.2 retains a thermal capacity or specific heat capacity of 5 J/kg/K under these conditions.

[0068] Therefore, the total heat exchanged to move from 20? C. to 12? C. is:

[00001]$Q=666.7W=D*\mathrm{Cp}*\left(20-10\right)$

[0069] The objective is to subcool this flow to 12? C. using a coil that is immersed in cold water kept at 10? C.

[0070] This means that this coil is a heat exchanger in which: [0071] The cold liquid: the water in the bath set and held at a temperature of 10? C. [0072] The hot liquid: two-phase liquid-gas CO.sub.2 entering at approximately 20? C. and leaving at approximately 12? C.

[0073] A countercurrent exchange model is used and the logarithmic temperature difference ?T=4.97? C. represents the difference between the temperatures between the two exchanging fluids at the two ends of the coil.

[0074] Care is taken to ensure that the output temperature of the CO.sub.2 flow is slightly above the temperature of the cold fluid (12? C.>10? C.). This prevents heat exchange pinch and therefore stoppage of the transfer in this selected countercurrent model.

[0075] An overall heat transfer coefficient of U-4843 W/m.sup.2/K can then be deduced by applying the McAdams formula. This known formula can be applied to a tube with turbulence having a constant external wall temperature (in this case cold fluid).

[0076] If a line having an internal diameter of 4 mm is chosen (to ensure turbulence and therefore good heat transfer), a minimum required length can be calculated as Lmin=2.2 m. The general classic heat exchange formula is then applied to the coil with:

Q=U*A*?T [0077] where A is the total exchange area of the tube, i.e. the total average surface area (between external and internal diameter) of the tube of length L.

[0078] The following is implemented for this application, which involves keeping a 55-60 bar high-pressure CO.sub.2 flow at a maximum of 12? C., where said flow would otherwise reach 20? C. as a result of the gas caused by the ingress of heat from the installation: [0079] A 20-litre tank that contains a refrigeration unit and a copper coil to keep the water in the bath at a target temperature of between 5? C. and 15? C. [0080] A stainless-steel coil with an internal diameter of approximately 4 mm and a length of 10 m, bearing in mind that the minimum length required for efficient transfer has been calculated at 2.2 m.

[0081] The following can be noted: [0082] 1. A bath temperature of 5? C. would enable the minimum exchange length to be further reduced to approximately 1.5 m. This enables the flexible use of the liquefier thus dimensioned to liquefy any gas that has formed before the usage point. [0083] 2. The equipment can be easily adapted to other flow conditions and target temperatures at the usage point.

[0084] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed.

[0085] Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0086] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0087] Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of comprising). Comprising as used herein may be replaced by the more limited transitional terms consisting essentially of and consisting of unless otherwise indicated herein.

[0088] Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0089] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0090] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.