Hydrocarbon Processing - June 2021 - GP-31

HEAT EXCHANGE
worn-in plate pack achieved the same results
as a new plate pack.
PSHEs have been successfully used in
many upstream, downstream, single-phase,
condensing and boiling applications. Although
the PSHE shell side is accessible
for mechanical cleaning just like bloc-type
exchangers, PSHEs are not recommended
for applications with severe fouling tendency,
where frequent mechanical cleaning
is anticipated on the plate side.
Flow distribution. Shell-side flow
distribution in a cross-flow arrangement
is always a concern. Maldistribution due
to flow bypass from the inlet to the outlet,
which is seen in " X " type S&T exchangers,
is minimal or less likely in a PSHE.
Small channels of plate pack result in a reasonable
pressure drop and, consequently,
even flow distribution.
HTRI performed an extensive study
of flow distribution in 2019.4
The result
is very satisfactory; channel-to-channel
flow distribution was uniform for both the
plate side and shell side in the example.
Multiple inlets and outlets and reasonable
pressure drop over the plate pack minimize
the risk of shell-side maldistribution.
PSHE design for gas-gas exchanger.
The authors' recommended PSHE is
shown in FIG. 5. Wet process gas (feed) is
located on the shell side, and dry process
gas (from the separator) is on the plate
side. Glycol injection to the feed, which
can be done in upstream pipe or directly
inside the exchanger, helps prevent hydrate
formation.
The authors offer several recommendations
for designing a gas-gas exchanger
as a PSHE:
* Maximum channel velocity
is limited, as per Knight's
recommendation.
* Minimum channel velocity is
of minor concern, since the
chance of stratification is nil.
* Glycol injection can be performed
within the exchanger or at the
inlet piping prior to the exchanger.
A CFD analysis might be needed
as further study to ensure even
distribution of glycol over the
entire plate pack.
Recommendations. Compactness and
reliability make PSHEs a suitable candidate
for many non-severe fouling applications
in onshore and offshore plants. It is
!
FIG. 5. PSHE for a gas-gas exchanger.
TABLE 1. Design comparison for PSHE vs. S&T exchanger
Heat exchanger type
Dimensions, mm
S&T
PSHE
1,500 (inner diameter)
× 14,000 (tube length)
1,530 (inner diameter)
× 3,000 (two plate packs)
a good fit in process and utility facilities,
and can be used for debottlenecking and
revamp by directly replacing an existing
tube bundle with a plate pack.
Large, conventional S&T gas-gas exchangers
in gas treatment facilities can be
replaced with compact PSHEs, resulting
in smaller footprint and a better economic
and technical solution (TABLE 1). GP
LITERATURE CITED
1
Mokhatab, S., A. Poe and J. Mak, Handbook of
Natural Gas Transmission and Processing, 4th Ed.,
Gulf Professional Publishing, October 2018.
2
Knight, W. P., " Plant operating data improve heat
exchanger design, " Hydrocarbon Processing, Vol. 54,
Iss. 5, 1975.
3
Nangia, K. K., J. W. Palen and J. Taborek, " Field data
and performance analysis for gas-gas exchanger
with glycol injection, " HTRI Report STS-1, 1972.
4
Farrell, K., " CFD simulation of plate and shell heat
exchanger, " HTRI Report PHE-22, 2019.
28,000
FIG. 4. PSHE exchanger construction.
Glycol injection
Approximate
weight, kg
100,000
Price,
€ MM*
1.8
1.3
*This is an indication for fabrication cost; transportation and installation cost are not included
ROBERT BROAD is Business
Development Manager-Systems at
API Heat Transfer. He is a chartered
chemical engineer, a Fellow of the
Institution of Chemical Engineers and
a member of both the International
Register of Professional Engineers
and the European Federation of National Engineering
Associations. Mr. Broad has worked for more than
20 yr with compact heat exchangers, striving to use
technology to reduce energy usage. He holds an MBA
degree from Henley Management College in the UK.
ABDOLLAH BAYATI is Heat Transfer
Subject Matter Expert at McDermott.
He has more than 20 yr of
experience in fabrication, thermal
and mechanical design of heat
exchangers for the oil and gas
industry, both onshore and offshore.
His journey through fabrication to design, along with
academic study, has strengthened and encouraged
him to explore new opportunities for technical and
economic improvement. He holds a BS degree in
heat transfer and fluid dynamics and an MS degree
in energy engineering.
Gas Processing & LNG | MAY/JUNE 2021 31
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Hydrocarbon Processing - June 2021

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