Page 299 - Hydrocarbon Exploration and Production Second Edition

286 Oil and Gas Processing

natural gas gas and gas from
(methane) liquid pipeline
to customer dehydration
compression

expansion

demethaniser

separation
natural gas
(liquids)
to fractionation vapour
plant liquid
Figure 11.19 Gas separation facilities.

cooler

inlet fractionate
feed

residual feed
heater
Figure 11.20 Fractionating column.

In such a plant, the gas stream passes through a series of fractionating columns
in which liquids are heated at the bottom and partly vaporised, and gases are cooled
and condensed at the top of the column. Gas flows up the column and liquid flows
down through the column, coming into close contact at trays in the column.
Lighter components are stripped to the top and heavier products stripped to the
bottom of the tower (Figure 11.20).