Patent Publication Number: US-2022219115-A1

Title: A system and method for handling a multiple phase hydrocarbon feed

Description:
FIELD OF THE INVENTION 
     The invention relates to the removal of acidic gases such as CO 2 , H 2 S and other hydrocarbon heavy components from a hydrocarbon gas feed streams. 
     BACKGROUND 
     The means by which acidic gases including CO 2  are removed from a hydrocarbon feed stream is dependent upon the concentration of CO 2  within the feed stream as well as anticipated flow rates. 
     One such method involves introducing a feed stream containing carbon dioxide and separating a gas stream using a nozzle adiabatic expander or cryogenic separation method including Joule Thomson valve and cryogenic distillation system. 
     A further means of separating CO 2  gas includes cyclonically separating solids and liquid phase from the feed stream whilst also cooling the feed stream so as to maintain the separated flow at a temperature below the acidic gas solid phase. Gas can then be removed directly from the separated gas flow with the solid phase passing to an additional collection tank. 
     It will be appreciated that the inflow into the separator may also be from a cyclonic separator and thus optimizing the separation process. 
     It will be appreciated that such a process, however, must balance the efficiency of removing a high proportion of the acidic gas from the original feed stream as well as managing the solid phase separated flow. 
     SUMMARY OF INVENTION 
     In one aspect the invention provides a solid handling vessel comprising: a separation tank having an inlet for tangentially receiving an inflow of CO 2  enriched hydrocarbon feed stream in a mixed solid vapour liquid phase; said separation tank to facilitate cyclonical flow of said feed stream; a heating assembly within the separation tank for maintaining the feed stream above a temperature for solidification of CO 2 ; a gas outlet arranged to vent gas from the separation tank; a collection tank located below, and in fluid communication with, the separation tank, said collection tank arranged to receive separated liquid and outflow said liquid from a liquid outlet. 
     In a second aspect the invention provides a method of separating a gas component from a CO 2  enriched hydrocarbon feed stream, the method comprising the steps of: tangentially introducing said feed stream into a separation tank; cyclonically flowing of said feed stream so as to separate a portion of CO 2  gas; venting said CO 2  gas from a gas outlet; heating a separated liquid within the separation tank above a temperature for solidification of CO 2 ; flowing said separated liquid from the separation tank to a collection tank, and; outflowing said liquid from a liquid outlet. 
     Accordingly, by ensuring the temperature of the separated liquid phase does not fall below the temperature for solid CO 2  the flow rate, and consequently, the efficiency of the separation process is maintained 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible and consequently, the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention. 
         FIG. 1  is a cross-sectional top section view of a solid handling vessel according to one aspect of the present invention, and; 
         FIG. 2  is a cross-sectional longitudinal view of a solid handling vessel according to a further embodiment of the present invention; 
     
    
    
     DETAILED DESCRIPTION 
     The system according to the present invention may be part of a process system to reduce hydrocarbon loss or enhance CO 2  separation in hydrocarbon gas mixture. This may achieved through a method of controlling the temperature in a vessel so that the frozen CO 2  is melted but not gassified. This will yield pure CO 2  stream in liquid form (and possibly more than 95% CO 2 —which may be especially advantageous for CO 2  injection). This invention can be paired with other cryogenic separation system such as Gas Twister (Nozzle adiabatic separator), Joule Thompson Valve, Cryogenic Distillation system especially that goes into solid region. 
     The present invention seeks to solve flow issues of the prior art by controlling phase change from the separation tank to the collection tank. 
       FIGS. 1 and 2  show the CO 2  solid handling vessel  5  according to the present invention. In this embodiment, the vessel  5  includes a top section  10  into which a 2-phase feed stream is introduced through an inlet  20 , at design operating temperatures in the range of −100° C. to −40° C. The feed stream enters the chamber  22  tangentially so as to place the flow in cyclonic conditions with liquid moving in the outer peripheral area  35  and separated gas moving to the centre  40 . The gas then exits from the gas outlet  25 . The gas outlet may be in fluid communication with a further separation system, so as to further reduce the CO 2  concentration in the vented gas. In one embodiment, the vented gas from the gas outlet  25  may have a concentration of 20 to 30% CO 2  which is a 50-80% reduction from the inlet CO 2  concentration. A subsequent pass through a second separation stream may further reduce this to 2 to 15%. 
     The chamber  22  includes a heating assembly for maintaining the CO 2  above the freezing temperature so as to flow into the collection tank  60 . It will be appreciated that the chamber  22  may include several heating assemblies so as to more uniformly heat the liquid. 
     The chamber  22  may further include a guide  24  to direct the gas flow upwards and fluid/solid flow downwards due to the cyclonic effect. A baffle  50  is provided intermediate the separation tank and the collection tank, proximate to the base of the chamber  22  such that in flowing downwards into the collection tank  60  the cyclonic flow of the liquid is hindered and permitted to flow through the peripheral vents  55  about the baffle  50  and substantially downward linear direction. 
     The bottom section  15  comprises the collection tank  60  having a liquid outlet  30  from which the liquid CO 2  flows. 
     The collection tank  60  includes a shell  62  containing a heat exchange assembly  70  to impart sufficient heat to prevent the liquid CO 2  turning solid. Should solid CO 2  form, the flow characteristics within the collection tank  60  and consequently outward flow from the outlet  30  would be hindered removing the efficiency of the process. To this end, in this embodiment the heat exchange assembly  70  includes tubes about which the liquid CO 2  flows within the shell  62  encapsulated by the collection tank  60 . It will be appreciated that other heat exchange systems may be utilised to achieve a similar result of preventing substantial solidification of the CO 2 . Within the tubes, a heat transfer medium flows, such that heat is imparted through the tube walls into the liquid CO 2 . 
     In a further embodiment, the heat transfer medium may be a portion of the outflowing liquid CO 2 . The outflowing CO 2 , which is arranged to meet to design outflow temperature, is passed through the tubes. At this temperature, the outflowing CO 2  has sufficient heat so as to maintain the temperature of the CO 2  within the collection tank  60  above the temperature required for the liquid phase, and so preventing solids forming. 
     In this arrangement the liquid inlet  20  may be in fluid communication with an upstream source of the feed stream. For instance, cyclonic separators may provide a hydrocarbon stream containing the CO 2  to the vessel  5 . Cyclonic separators will reduce the concentration of CO 2  within the hydrocarbon feed stream with the vessel  5  arranged to further reduce the concentration. In one embodiment, the liquid outlet stream may have a CO 2  concentration of 95% or above, leading to a hydrocarbon loss of less than 5%. 
     By way of example, the following conditions may be observed through the operation of a device according to the present invention. It will be noted that the following is not to be interpreted as limiting on the invention, and is provide as exemplary only. 
     For the conditions at Inlet  20 :
         Temperature: −60 to −80 C   CO2: 30-50%   Pressure: 15 to 30 bar       

     The system according to the present invention may be expected to provide the following outlet conditions.
         Conditions at Liquid Outlet  30 :
           Temperature: −50 to −60 C   CO2: 95-99%   Pressure: 15 to 30 bar   
           Conditions at Gas Outlet  25 :
           Temperature: −50 to −60 C   CO2: 20-30%   Pressure: 15 to 30 bar