Hydrocarbon Processing - May 2022 - 31

Biofuels, Alternative Fuels and Green Petrochemicals
rangement, separate compressor bearings
are not necessary. The bearings of the pinion
shafts are identical to those of the compressor
rotor. The rotor shafts are made
from a single heat-treated forged low-alloy
steel. Shaft seals can be labyrinths, dry gas
seals or floating carbon rings.
The high-speed rotors use tilting pad
bearings and sleeve bearings for the slowspeed
shaft, while multiple disk couplings
connect the driver and the compressor
gearbox. Operational control is via a
fixed-speed e-motor drive with inlet guide
vanes installed upstream of the first stage
impeller (part of the compressor casing).
The integrally geared compressor
features optimized aerodynamic speed
capability, increasing rotor speeds along
the compression process. Furthermore,
its integral setup makes it possible to
have an intercooling or steam application
for a desuperheater after each compression
stage, which results in increased efficiency
(FIG. 2).
This IGC provides reliability, an essential
element in polyethylene plants.
The broadening use of this compression
technology in hydrocarbon processing
environments has been supported by several
factors, including advances in shaft
seal technology, modern aerodynamics,
increased rotor dynamic and thermodynamic
knowledge. With these advances, its
simplicity, reliability, and lightweight and
compact design, IGCs have become more
widely accepted in the hydrocarbon world.
Design details. For the Terneuzen PE
plant, a two-stage compressor was designed
(FIG. 4), which means one pinion
with two impellers on each end. The
number of stages is defined by the pressure
ratio limit for each stage; if required,
it would have been possible to design a
three-stage compressor for this purpose.
The advantage would have been a lower
power consumption of the e-motor
(though not to a significant degree).
The MVR is a two-stage IGC that compresses
superheated steam from 3 barg to
12.5 barg. The nominal mass flow of the
installation is 12 tph. The steam is cooled
by water injection with a desuperheater
at the inlet and between the stages. The
larger droplets are caught downstream by
a knockout drum. The steam enters the
compressor on the suction side at 3 barg
and a temperature of 150°C-220°C. The
steam is sent through the desuperheater
Steam in: 12.4 tph
2.9 barg, 178°C
163°C
Desuperheater water:
0.1 tph, 20°C
E
Power:
1.46 MWe
6.7 barg
262°C
196°C
Desuperheater water:
0.7 tph, 20°C
FIG. 5. Average unit values between November 17, 2020 and November 17, 2021.
and the knockout drum in case temperatures
reach higher than 170°C so that
it can avoid higher temperatures in the
compressor discharge stage (FIG. 3).
High coefficient of
The co-author of this articleb
performance.
carried
out research on the compressor's coefficient
of performance (COP) that was
performed once the compressor was up
and running. The research determined a
result of 7.5, which represents a high performance-partly
attributable to the inherent
advantage of an open-heat pump
compared to a standard compression heat
pump (FIG. 5). More recently, between
November 17, 2020, and November 17,
2021, the measurements resulted in an
overall COP of 7.5. A COP of 7.5 means
that for 1 MW of electricity, 7.5 MW of
thermal energy was produced.
The COP value indicates the energy
efficiency of a range of machines, such as
chillers, heat pumps and MVRs. In simple
terms, COP shows the ratio between the
recovered thermal power and the supplied
electrical compressor power. Depending
on the application, a COP value
of at least 2 can be attractive from an energy
and economic perspective. After reaching
a COP high of 7.5, the expectations
on the potential of steam compression are
certainly high. In addition to good COP
achievement, steam recompression underpins
natural gas savings and CO2
The compressor now operates without
significant problems, and it has only been
briefly out of service for steam network
maintenance. In the last 12 mos, approximately
10 MMNm³ of natural gas was
saved, and a CO2
reduction of 17.8 kilotons
was achieved.
NOTES
a Atlas Copco Gas and Process
b Blue Terra
ULRICH SCHMITZ has more than
25 yr of experience in sales,
marketing and project handling of
tailor-made turbomachinery for
markets such as industrial gases,
power generation, chemical/
petrochemical, and oil and gas.
As Vice President Marketing for Atlas Copco Gas and
Process, he is based at the production company Atlas
Copco Energas in Cologne, Germany. Mr. Schmitz drives
product management and state-of-the-art products
while also identifying new markets and products
needed in the near- and long-term future. He holds a
diploma in mechanical engineering from the University
of Applied Sciences in Cologne (FH Köln), Germany.
PETER VAN LIMMEN has been
a mechanical engineer at Dow
Chemical for 37 yr and has held
several roles in operations,
maintenance and engineering.
Based in Terneuzen, the
Netherlands, he globally
supports Dow Chemical Power Plants as a Rotating
Equipment Specialist. His experience includes large
turbomachinery overhauls, uprates and repairs,
projects and reliability issues. Mr. van Limmen holds
a BS degree in mechanical engineering from the
HZ University in Vlissingen, the Netherlands.
emissions
reductions.
Using the untapped potential of lowpressure
steam via MVR, the Terneuzen
plant operators successfully found a more
energy-efficient and sustainable energy
supply. The project highlighted that MVR
can be used anywhere where there is lowpressure
steam.
RENÉ WAGGEVELD has 18 yr
of industry experience and has
spent 13 yr with BlueTerra. His
expertise is in process modeling,
capacity expansion studies, and
energy optimization projects in
various fields, ranging from
petrochemical companies to paper and energy
production. Dr. Waggeveld earned an MS degree
in chemical engineering from the University of
Twente, the Netherlands, and a PDEng in process
design from the same university.
Hydrocarbon Processing | MAY 2022 31
�: 77%
COP: 7.5
�: 76%
Steam out: 13.3 tph
12 barg, 274°C
Hydrocarbon Processing - May 2022

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