PROCESS ECONOMICS PROGRAM SRI INTERNATIONAL Menlo Park, California 94025 Abstract Process Economics Program Report No. 135 NATURAL GAS LIQUIES Natural gas liquids (NGL) are the C2-k liquefied hydrocarbons which are recovered above ground in natural gas field facilities or in gas processirg plants. The report concerns the technology and econanics of NGL recovery in gas processing plants by the following three most im- portant processes in commercial use today: l Expander l Cascade refrigeration l Refrigerated absorption. The principal products are ethane, propane, isobutane, n-butane, and C5+ natural gasoline. Capital investment and production costs have been calculated for the expander and cascade refrigeration processes at two natural gas liquids contents (2.32 and 6.26 gal/l,000 scf) and two levels of ethane recoveries (86 and 50%), and for the refrigerated ab- sorption process at the same two natural gas liquids contents but only 50% ethane recoveries. The study shows that, for an equivalent ethane recovery, the ex- pander process has the lowest energy consumption as well as the lowest investment and product value (productioncost +25%/yr ROI), followed by the cascade refrigeration and refrigerated absorption processes, in that order. PEP '78 JJLM
Transcript
PROCESS ECONOMICS
PROGRAM SRI INTERNATIONAL
Menlo Park, California
94025
Abstract
Process Economics Program Report No. 135
NATURAL GAS LIQUIES
Natural gas liquids (NGL) are the C2-k liquefied hydrocarbons which
are recovered above ground in natural gas field facilities or in gas
processirg plants. The report concerns the technology and econanics of
NGL recovery in gas processing plants by the following three most im-
portant processes in commercial use today:
l Expander
l Cascade refrigeration
l Refrigerated absorption.
The principal products are ethane, propane, isobutane, n-butane,
and C5+ natural gasoline. Capital investment and production costs have
been calculated for the expander and cascade refrigeration processes at
two natural gas liquids contents (2.32 and 6.26 gal/l,000 scf) and two
levels of ethane recoveries (86 and 50%), and for the refrigerated ab-
sorption process at the same two natural gas liquids contents but only
50% ethane recoveries.
The study shows that, for an equivalent ethane recovery, the ex-
pander process has the lowest energy consumption as well as the lowest
investment and product value (production cost +25%/yr ROI), followed by
the cascade refrigeration and refrigerated absorption processes, in
that order.
PEP '78 JJLM
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Report No. 135
NATURAL GAS LIQUIDS
JAMES J. L. MA
contributions by : CHING-SHIEN WU
October 1979
A private report by the
PROCESS ECONOMICS PROGRAM
Menlo Park, California 94025
For detailed marketing data and information, the reader is
referred to one of the SRI programs specializing in marketing
research. The CHEMICAL ECONOMICS HANDBOOK Program covers
most major chemicals and chemical products produced in the
United States and the WORLD PETRCCHEMICALS Program covers
major hydrocarbons and their derivatives on a worldwide basis.
In addition, the SRI DIRECTORY OF CHEMICAL PRODUCERS services
provide detailed lists of chemical producers by company, prod-
uct, and plant for the United States and Western Europe.
NGL RECOVERY - GENERAL PROCESS BACKGROUND ..........
Natural Gas Composition ................... Thermodynamics and Phase Equilibrium ............ Process Types. ....................... Compression ........................ Adsorption ........................ Ambient Temperature Absorption .............. Refrigerated Absorption .................. Straight Refrigeration .................. Joule-Thomson Expansion .................. Expander .........................
Gas Treating ........................
27
27 30 34 34 36 36 36 37 37 37 38
NGL BY THE EXPANDER PROCESS .................
Review of Process ...................... Process Description ..................... Process Discussion ..................... Cost Estimates ....................... Capital Costs. ...................... Production Costs .....................
45
45 48 78 82 82 83
NGL BY THE CASCADE REFRIGERATION PROCESS ..........
Review of Process ...................... Process Description ..................... Process Discussion ..................... Cost Estimates ....................... Capital Costs ....................... Production Costs .....................
101
102 105 126 130 130 131
CONTENTS
7 NGL BY THE REFRIGERATED ABSORPTION PROCESS ......... 149
Review of Process. ..................... 149 Process Description ..................... 152 Process Discussion ..................... 175 Cost Estimates ....................... 179 Capital Costs ....................... 179 Production Costs ..................... 180
5.3 NGL by the Expander Process Effect of Plant Capacity on Total Fixed Capital Investment . . . . . . . . . . . . . . . . . , . . . 90
5.4 NGL by the Expander Process Effect of Thermal Value on Average Products Value . . . . . . 96
5.5 NGL by the Expander Process Effect of Operating Level and Plant Capacity on Production Cost for Cases A and B . . . . . . . . . . . . . 97
5.6 NGL Recovery by the Expander Process Effect of Operating Level and Plant Capacity on Production Cost for Cases C and D . . . . . . . . . . . . . 98
6.1 NGL by the Cascade Refrigeration Process Process Flow Schemes . . . . . . . . . . . . . . . . . . . . 104
