NGL Recovery Methods and Configurations
First Claim
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1. A method of operating a plant for NGL recovery from a feed gas, comprising:
- separating the feed gas in a refluxed column to thereby produce a residue gas, and using a portion of the residue gas after cooling as a first reflux;
expanding a portion of the feed gas upstream of the column to thereby form a second reflux; and
controlling temperature of the column by using at least one of (1) a control circuit that controls a temperature of an expander discharge stream that is fed to the column and (2) an intermediate reflux condenser disposed between an upper section and a lower section of the column that maintains temperature of the lower section above a temperature sufficient to prevent carbon dioxide freezing.
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Abstract
Contemplated plants and methods for NGL recovery from feed gases having a carbon dioxide content equal or greater than about 2% employ temperature control configurations that allow high-level and flexible recovery of ethane and heavier components while avoiding freezing of the carbon dioxide in the process. Where the feed gas has a significant fraction of C3+ components and moderate carbon dioxide content, a single column configuration with an intermediate reflux condenser may be used, while two-column configurations may be used for feed gases with high carbon dioxide content and relatively low C3+ component concentration.
35 Citations
20 Claims
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1. A method of operating a plant for NGL recovery from a feed gas, comprising:
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separating the feed gas in a refluxed column to thereby produce a residue gas, and using a portion of the residue gas after cooling as a first reflux; expanding a portion of the feed gas upstream of the column to thereby form a second reflux; and controlling temperature of the column by using at least one of (1) a control circuit that controls a temperature of an expander discharge stream that is fed to the column and (2) an intermediate reflux condenser disposed between an upper section and a lower section of the column that maintains temperature of the lower section above a temperature sufficient to prevent carbon dioxide freezing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A plant comprising:
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a column having an intermediate reflux condenser that is configured to operate at a temperature of between about −
20°
F. and about −
40°
F. and that is located between a fractionation section and a rectification section of the column, and wherein the column is further configured to receive a first and a second reflux stream and to produce an overhead product;a circuit coupled to the column such that a liquid stream is fed from the fractionation section to the rectification section via a heat exchanger that is configured such that the liquid stream is heated in the heat exchanger; and a recycle circuit that is configured to provide a portion of the overhead product as the first reflux stream to the column. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A plant comprising:
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a first column configured to receive a first and a second reflux stream and further configured to receive an expanded feed gas stream; a temperature control unit thermally coupled to the first column and configured to determine a temperature in the first column; a heat exchanger that is configured to cool a first and a second portion of a feed gas to thereby form the second reflux stream and a cooled second portion of the feed gas, respectively; a bypass valve configured to control flow volume of a third portion of the feed gas to the cooled second portion of the feed gas; and a control system that is configured to adjust the flow volume of the third portion of the feed gas as a function of the temperature in the first column. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification