Page 131 - Compression Machinery for Oil and Gas

118 SECTION II Types of Equipment

Gas temperature increases in a given section are reduced by the mixing of the
sidestream flow into the suction of the following section of the compressor. This
maintains gas temperature throughout the machine at reasonable levels [30].
The LNG propane compressor is one of the more difficult compressor appli-
cations, typically accommodating a wide operational map with multiple side-
load inlets, a high molecular weight gas and low temperatures. The process
map in Fig. 3.79 requires a propane compressor that can accommodate four
inlets. Fig. 3.80 shows a ¾ cutout of just such a compressor that is used for
the C3MR process in a 4.7 MMTPA plant (one inlet is not pictured due to
the cutout).
The compressor shown in Fig. 3.80 has the following features:
l Drive-thru shaft with gas turbine main drive at one end and starter motor at
other end.
l Horizontal split casing for simplified maintenance.
l Five nozzles: one main inlet, three side load, and one discharge.
l Internal sideload mixing.
l Unconventional up nozzle requirement necessitates piping removal for
maintenance.
l Not pictured, recycle lines.
Figs. 3.80 and 3.81 show the compressor on its baseplate getting installed and
indicate the scale of this large compressor.

FIG. 3.80 C3MR propane compressor. (Courtesy of Elliott Group.)