Natural Gas Industry Natural Gas Liquids (NGL) Plant Process Gas Chromatograph Application Note A Natural Gas Liquids (NGL) plant consists of a series of fractionators whose purpose is to separate a mixture of light hydrocarbons into various pure products. The NGL Plant typically consists of a demethanizer, a deethanizer, a depropanizer, a debutanizer, and a butane splitter. Other arrangements of columns are possible for NGL Plants and also parallel columns may be present for higher plant processing capacity. monoxide and hydrogen). The ethane stream from an NGL Plant is used as either fuel or as feedstock for chemical production (for chemical production, the chemical desired is usually ethylene). The isobutane product of an NGL Plant is usually used as feedstock for an alkylation unit. The normal butane stream is used as feedstock to a butamer unit (to make isobutane) or as fuel. The C5+ product stream is used as a gasoline blending component. The feed to a NGL Plant consists of a mixture of light hydrocarbons (methane, ethane, propane, isobutane, n-butane and C5+ or gasoline components) from the Natural Gas Plant. The NGL is fed to the demethanizer where methane is removed (by fractionation) as an overhead product. The bottoms product, consisting of ethane and heavier compounds, is the feed to the deethanizer. In the deethanizer, ethane is removed as an overhead product. Propane and heavier components leaves the deethanizer as a bottoms product and fed to the depropanizer. In the depropanizer, propane is removed as an overhead product and butane and heavier compounds leaves the product and fed to a debutanizer. In the debutanizer, isobutane and normal butane are removed as an overhead product and fed to a C4 splitter. C5+ material leaves the debutanizer bottoms product. In the C4 splitter, isobutane is separated (overhead product) from the normal butane (bottoms product). The operating objectives of an NGL Plant are typically a balance of two objectives: The methane stream from an NGL Plant is normally used as fuel (i.e. used for its heating value) or as feedstock to a methane reformer for the production of synthesis gas (a mixture of carbon 1.To maximize through-put while maintaining product quality. 2.To optimize product specifications versus utilities to maximize economic return. Process gas chromatographs provide the compositional information needed for the plant control system to meet these objectives. Typical GC measurements The number of gas chromatographs required varies on how many products the plant wants to extract from the natural gas liquid feed stream. As mentioned above, the analyzers used in the NGL plant fall into two categories. The first are those analyzers used for monitoring the purity of the overhead product streams. The second type of analyzers used is the column-to-column analyzers that monitor the efficiency of each tower. www.usa.siemens.com/processanalytics Natural Gas Liquids (NGL) Plant Analyzer no. Stream Components measured Measurement objective 1 Methane Product C2 Minimize losses of C2 in Methane Product stream 2 DeMethanizer Bottoms C1, C2 Control C1 impurity in the Ethane Product stream 3 Ethane Product C3 Minimize losses of C3 in the Ethane Product stream 4 DeEthanizer Bottoms C2, C3 Control C2 impurity in the Propane Product stream 5 Propane Product iC4 6 DePropanizer Bottoms C3, iC4 Minimize losses of iC4 in the Propane Product stream Control C3 impurity in the isoButane Product stream Minimize losses of iC5 in the n-Butane Product Stream Control nC4 impurity in the C5+ Product stream Control iC4 impurity in the n-Butane Product stream 7 DeButanizer Overhead 8 DeButanizer Bottoms 9 C4 Splitter Overhead iC5, nC4 nC4 nC4 10 C4 Splitter Bottoms iC4 Control nC4 impurity in the isoButane Product stream For more information, please contact: Siemens Industry, Inc. 7101 Hollister Road Houston, TX 77040 713-939-7400 email@example.com Siemens Industry, Inc. 3333 Old Milton Parkway Alpharetta, GA 30005 1-800-241-4453 firstname.lastname@example.org Subject to change without prior notice Order No.: PIAAP-00007-0713 Printed in USA © 2013 Siemens Industry, Inc. www.usa.siemens.com/processanalytics The information provided in this flyer contains merely general descriptions or characteristics of performance which in case of actual use do not always apply as described or which may change as a result of further development of the products. An obligation to provide the respective characteristics shall only exist if expressly agreed in the terms of contract. All product designations may be trademarks or product names of Siemens AG or supplier companies whose use by third parties for their own purposes could violate the rights of the owners.
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