Hydrocarbon Processing - August 2021 - 69

Heat Transfer
Spiral vs. shell-and-tube. TABLE 1 summarizes the advantages
of SHEs compared to shell-and-tube heat exchangers based
on design features explained in the previous section. With
fewer turnaround inspection and cleaning activities, the end
user will avoid production losses and significantly decrease
maintenance costs.
Technology implementation. For the Saudi Aramco Tanajib
Gas plant project (part of the Saudi Aramco Marjan Increment
Program), the licensor selected SPHEs for the three services here:
* Reclaimer loop heater
* Slurry cooler
* Lean/rich ethylene glycol (MEG) exchanger.
The SPHE was selected due to the high fouling phenomena
that would be eliminated with this technology. Furthermore,
due to the services' highly corrosive nature, the licensor specified
that the material of construction must be stainless-steel alloy
6MO to sustain the reliability of the exchanger throughout
its anticipated lifetime of 25 yr in service. Inspection and maintenance
activities will be minimized for these services within
the plant, which is a time and cost-effective proposition.
A case study performed using an HTRI run for a slurry
cooler considering SPHEs and shell-and-tube heat exchangers
(TABLE 2) provides a good indication of the size, weight and use
of plant layout for the exchanger design with identical duties
and temperature differences requirements. Slurry is a concentrated
MEG solution saturated with salts and containing up to
20 wt% solid salts particles. The total salts content is 25 wt%, as
per H&MB Rev.H. Salts are mainly composed of sodium chloride
(NaCl), so the chloride content is high. pH is maintained
between 10 and 11.5.
Based on TABLE 2, the shell-and-tube design would be eight
times larger in length compared to an SPHE (compacted), confirming
the advantage of having a smaller footprint in the industrial
plant, excluding the need of additional space for tube bundle
removal utilizing crane and truck for loading and unloading.
Another advantage is the higher velocity in the SPHE design,
which in turns provides a self-cleaning effect due to the
higher velocity and the turbulence created with spacing studs.
SPHE technology has been in existence since 1930; with
advancements made over the years, it has proven to be the bestsuited
technology for such services.
This technology was implemented in the Fadhili Gas Plant
in 2019 with an indication of satisfactory performance and
reliability in operation with no adverse reports, including the
performance of SHE implementations within applications at
a petrochemical complex and another chemicals manufacturing
facility.
TABLE 2. Case study results
Slurry coolers
Diameter
Length
Weight
Velocity slurry
Velocity water
Spiral
24 in.
2 ft
3,600 lb
6.56 ft/sec
3.28 fts/sec
Shell-and-tube
16 in.
16 ft
4,000 lb
0.73 ft/sec
1.21 ft/sec
Hydrocarbon Processing | AUGUST 2021 69
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Takeaway. Fouling is a chronic problem in the oil and gas industry,
particularly for exchangers operating in harsh environments.
The SPHE is a reliable technology that can overcome
such conditions.
The SPHE's compact, true countercurrent flow design with
self-cleaning effect and high heat transfer coefficients provide
easy access to interior heat transfer services for field inspection,
routine maintenance, or manual and chemical cleaning as required,
with no involvement of heavy equipment.
The authors' company is adopting the International Standard
API 664 for material selection, design, fabrication, inspection
and testing. Developing a company specification, standard
and special inspection requirement formed in collaboration
with the company's approved spiral heat exchanger manufacturer
will be the next step to govern design, fabrication and inspection
for future purchase requests.
ABDULLAH ALHAZEMI is a Project Engineer at Saudi Aramco
with a BS degree in applied mechanical engineering from
King Fahd University of Petroleum and Minerals. He began
his career as a Maintenance Engineer and now works at the
Marjan project. Mr. Alhazemi holds PMP and SMRP certificates.
SHUJA ALHARBI works at Saudi Aramco and is a certified
PMP with more than 13 yr of experience with turbomachinery
and static equipment in the oil and gas industry. He earned
a BSc degree in mechanical engineering.
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