Cooling Water Flow Redistribution
 A MW Kellogg ammonia plant had recurring issues with
a cooling water heat exchanger plugging with calcium
sulfate scale. Cooling water flowed through the
shell side of the heat exchanger. The process
inlet temperature to the exchanger averaged about 350° F.
This hot process condition caused the cooling water
to “boil” on the tube surface, thus tenacious
deposits were left that could not be removed. The
bundle had to be replaced every few years.
Chemtech applied it’s Cooling Water Equipment Reliability
Program to the situation. Flow and temperature
surveys showed that the velocity through the exchanger
was less than 2.0 feet per second, and the resulting
tube wall skin temperature was over 230° F. Through
engineering design, the inlet cooling water piping
configuration was altered to allow for cooler first-pass
water to reach the exchanger. Increased cooling
water line sizing was installed allowing for additional
flow to be achieved and velocities to be increased. Also,
the exchanger baffle spacing was redesigned to increase
velocities through the bundle.
The improvements to the system eliminated the deposition
in the heat exchanger, resulting in a cleaner bundle,
improved efficiency, and longer run-time of the unit.
Steam
Drum Carryover
 A large industrial facility had recurring problems
with water droplet carryover in its 1550 psig boiler
system. The carryover resulted in solid deposits
in the turbines and loss of turbine efficiency. It
was estimated that the loss of efficiency was costing
the plant about 25,000 pounds per hour of steam.
Chemtech provided engineering services and proposed
changes to the Chemical feed systems and operation
of the steam drum. It was determined that the
previous chemical and operational program was causing
foaming in the steam drum.
Once Chemtech’s chemical and operational program
was adopted, the carryover was eliminated. Turbine
efficiency remained constant throughout a 3-year run.
The engineering study followed by the improved system
modifications resulted in annualized savings of about
$1.25 million.
Plant Startup after Hurricane Katrina
 A large refinery was affected by the damaging winds
from Hurricane Katrina. The winds damaged the
structure and tore several of the shrouds from the
top of the tower. The plant personnel wanted
to resume operation as soon as possible, but were unsure
how to cope with the loss of the cooling tower, a critical
part of the operation. Chemtech worked with the
process engineers at the plant to establish a path
forward.
Because Chemtech had operational data on the cooling
tower, engineering was able to determine the amount
of heat duty each cooling tower cell could perform. Based
on this information, the plant was able to decide which
cells to repair in what order to start up individual
units in a fashioned sequence. The plant units
were started up in a systematic order corresponding
with the cooling tower cells.
The plant personnel estimated that this work allowed
several refinery units to be started two days earlier
than was originally proposed, resulting in a gain of
about $6 million.
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