TH48990A - Hydrocarbon gas processing. - Google Patents

Abstract

DC60 (16/05/60) revealed a method for the recovery of ethane, ethylene, propane, propylene, and/or heavier hydrocarbon components from a hydrocarbon gas stream. In recent years, the generally accepted method for hydrocarbon gas stream separation involved delivering at least a portion of the gas stream to a fractionation tower containing at least one reheating boiler, and often one or more side reheating boilers, to deliver heat to the column by drawing in and partially heating the tower fluid to produce a vaporization that separates the more volatile components from the desired components. Most often, the reheating boilers and side reheating boilers (if present) are incorporated into the feed stream cooling scheme to provide at least the necessary cooling to condense the components desired for further fractionation in the distillation column. In the revealed method, the tower reheating boiler scheme is modified to utilize one or more distillation streams of tower fluid from a higher point in the column than that used in the conventional reheating boiler scheme, providing a cooler stream for the reheating boilers that offer more efficient cooling of the feed stream and thus improving efficiency. This process separates and recovers the desired components. Furthermore, the liquid stream drawn from a higher point in the column contains a greater volume of more volatile components, which, when vaporized, provide better separation of undesirable components such as carbon dioxide without compromising the purification and recovery of the desired components. The heated distillation stream is then returned to a lower point on the fractionation column, separated from the extraction point by at least one distance. Theories have revealed methods for the recovery of ethane, ethylene, propane, propylene, and/or heavier hydrocarbon components from hydrocarbon gas streams. In recent years, the generally accepted method for separating hydrocarbon gas streams includes delivering at least a portion of the gas stream to a fractionation column containing at least one reheat boiler, and often one or more side reheat boilers, to deliver heat to the column by extracting and partially heating the column liquid to produce a vapor that separates the more volatile components from the desired components. Most commonly, the reheat boilers and... A side reheater (if present) is incorporated into the reheater plan to cool the feed stream, allowing at least a portion of the cooling required to condense the desired components for subsequent fractional separation in the distillation column. In the disclosed procedure, the reheater plan is modified to utilize one or more column liquid streams drawn from a higher point in the column than that used in a conventional reheater plan. This provides a cooler stream for the reheater, resulting in more efficient cooling of the feed stream and, by its means, improving the efficiency of recovering purified components from the desired elements. Furthermore, the column liquid streams drawn from higher points in the column contain a greater volume of more volatile components, which, when vaporized, provide better volatile separation of undesirable components such as carbon dioxide without compromising the recovery of the desired components. The heated distillation stream is then returned to a lower point on the fractional separation column, separated from the extraction point by at least one theoretical distance.

Claims (13)

May 16, 2017 1. A procedure for the separation of a gas stream containing methane, C2 components, C3 components, and heavier hydrocarbon components into a volatile residue gas with the aforementioned methane as the main component and a less volatile residue gas with the C2, C3, and heavier hydrocarbon components as the main components, which is performed by (a) acting on the said gas stream in one or more heat exchange steps and at least one division step to produce at least a first feed stream that has been cooled under pressure to its significant total condensation, and at least a second feed stream that has been cooled under pressure; (b) expanding the said significantly condensed first feed stream to a lower pressure, further cooling, and then delivering it to the fractional separation tower at the upper feed point; (c) expanding the said cooled second feed stream to a lower pressure and then delivering it to the said fractional separation tower at the mid-column feed point; and (d) fractional separating the said expanded and cooled first feed stream and the said expanded second feed stream. At the lower pressures mentioned, which purify and recover the less volatile fractional components than mentioned; improvements are made which (1) draw the distillate stream from the fractional separation tower and heat it; (2) return the heated distillate stream to the bottom point on the fractional separation tower separated from the withdrawal point by at least one theoretical distance; and (3) the volume and temperature of the feed stream to the fractional separation tower are effective enough to maintain the top temperature of the fractional separation tower at the temperature at which the major components of the less volatile fractional fractional components are purified and recovered. 1. In the process for separating a gas stream containing methane, C2, C3, and heavier hydrocarbon components into volatile fractional sub-gases with the aforementioned methane as the main component and less volatile fractional gases with the C2, C3, and heavier hydrocarbon components as the main components, the process is carried out as follows: (a) one or more heat exchange steps and at least one division step are performed to produce at least a first feed stream that is compressed and cooled to its total condensation, and at least a second feed stream that is compressed and cooled; (b) the compressed first feed stream is compressed to a lower pressure, further cooled, and subsequently delivered to the fractionation tower at the top feed point; (c) the compressed second feed stream is compressed to a lower pressure, and subsequently delivered to the fractionation tower at the middle feed point; and (d) the compressed and cooled first feed stream and the second feed stream The aforementioned extended second feed, at a lower pressure than that mentioned, recovers a relatively smaller proportion of volatile fractional components; an improvement which (1) draws the distillate stream from the aforementioned fractional separation tower and heats it; (2) returns the heated distillate stream to a bottom point on the aforementioned fractional separation tower separated by at least one theoretical distance from the draw-off point; and (3) the volume and temperature of the aforementioned feed stream to the aforementioned fractional separation tower are effective in maintaining the top temperature of the aforementioned fractional separation tower at the temperature at which the major components in the relatively less volatile fractional fractional components are recovered. 2. In the process for separating a gas stream containing methane, C2, C3, and heavier hydrocarbon components into a volatile residue stream with the aforementioned methane as the main component, and a less volatile residue stream with C2, C3, and heavier hydrocarbon components as the main components, the following processes are performed: (a) the aforementioned volatile residue stream is recompressed and a portion is withdrawn to form a compressed primary feed stream; (b) the aforementioned compressed primary feed stream is cooled under pressure to significantly condense it; (c) the aforementioned condensed feed stream is significantly extended to a lower pressure, where it is further cooled and subsequently delivered to the fractionation tower at the top feed point; (d) the aforementioned gas stream is acted upon in one or more heat exchange steps to produce at least a second compressed secondary feed stream; (e) The aforementioned second cooled feed stream is extended to the lower pressure mentioned and then delivered to the aforementioned fractionalization tower at the central feed point of the column; and (f) the aforementioned extended and cooled first feed stream and the aforementioned extended second feed stream at the lower pressure mentioned, which recovers less volatile fractional components than mentioned; an improvement which (1) draws the distillate stream from the aforementioned fractionalization tower and heats it; (2) returns the heated distillate stream to the bottom point on the aforementioned fractionalization tower separated from the aforementioned draw-out point by at least one theoretical distance; and (3) the volume and temperature of the aforementioned feed streams to the aforementioned fractionalization tower are effective in maintaining the top temperature of the aforementioned fractionalization tower at the temperature at which the major components in the less volatile fractional fraction are recovered. 3. Improvements pursuant to claim 1 or 2, which involve pumping the distilled liquid as mentioned above after it has been removed from the fractional separation tower as mentioned above. 4. Improvements under claim 3 which (a) divide the aforementioned pumped liquid distillation stream into at least a first and a second part; (b) heat the aforementioned first part; and (c) return the heated first part to the bottom point on the sequence separation tower separated from the extraction point by at least one theoretical distance. 5. An improvement under claim 4, which brings the first part mentioned above, into a heat exchange relationship with at least a portion of the gas stream mentioned above or the feed stream mentioned above, in order to deliver the cooling mentioned above to it, and by that it heats the first part mentioned above. 6. Improvements under claim 4, in which the volume and temperature of the preheated first phase, and the heating delivered to the fractionation tower, are effective in maintaining the bottom temperature of the fractionation tower at a temperature that reduces the amount of carbon dioxide in the volatile fraction to a relatively low level, as previously stated. 7. Improvements under claim 5, in which the volume and temperature of the heated distillation stream as mentioned, and the heating supplied to the fractionation tower as mentioned, are effective in maintaining the bottom temperature of the fractionation tower at a temperature that reduces the amount of carbon dioxide in the volatile fraction to a relatively low level than previously stated. 8. An improvement under claim 3 which brings the said pumped distillation stream into a heat exchange relationship with at least part of the said gas stream or the said feed stream to deliver the said cooling to it and by that means heat the said pumped distillation stream. 9. Improvements under claim 8, in which the volume and temperature of the heated distillation stream as mentioned, and the heating supplied to the fractionation tower as mentioned, are effective in maintaining the bottom temperature of the fractionation tower at a temperature that reduces the amount of carbon dioxide in the volatile fraction to a relatively low level than previously stated. 10. Improvements under claim 3, in which the volume and temperature of the heated distillation stream and the heating supplied to the fractionation tower are effective in maintaining the bottom temperature of the fractionation tower at a temperature that reduces the amount of carbon dioxide in the volatile fraction to a relatively low level than previously stated. 11. An improvement under claim 1 or 2 which brings the said distillation stream into a heat exchange relationship with at least part of the said gas stream or the said feed stream to deliver the said cooling to it and by that means heat the said distillation stream. 12. Improvements under claim 11, in which the volume and temperature of the heated distillation stream and the heating supplied to the fractionation tower are effective in maintaining the bottom temperature of the fractionation tower at a temperature that reduces the amount of carbon dioxide in the volatile fraction to a relatively low level than previously stated. 13. Improvements under claim 1 or 2, in which the volume and temperature of the heated distillation stream as mentioned, and the heating supplied to the fractionation tower as mentioned, are effective in maintaining the bottom temperature of the fractionation tower at a temperature that reduces the amount of carbon dioxide in the volatile fraction to a relatively small degree less than that mentioned.