Methanol Plant Capacity Enhancement By: Mr. C D ... - Fibre2fashion

Plant Re-commissioning with the Isothermal Reactor
Following the replacement of the quench reactor with the Isothermal reactor from Linde, the plant was ready
for start up. The following details the activities associated with start up after the changes were made.
Basic and Detail Engineering - Design Fundamentals
The original plant was designed by Linde with process licensing from ICI. Linde performed the basic
engineering for the loop modification and the detailed engineering for the new Isothermal reactor. Based on
the data for the new design conditions, a debottlenecking study on the distillation section was carried out inhouse
by our Technical Services department. Major pre-fabrication work and in-plant erection of the loops
which were to be replaced was completed before the final shutdown of the plant. A shutdown schedule of
11 days was planned.
Outline of the Pre commissioning activities
The piping loops were identified and broken down into various process loops per the P & IDs. The plant was
broadly classified into three independent sections: synthesis loop, makeup gas loop, and distillation loop.
This helped prioritize tasks such that the synthesis and related loops were made ready first. The loops,
which were erected before shutdown, were prepared for commissioning by flushing / blowing. Based on the
service, the plans for flushing / blowing were prepared and discussed with the mechanical and instrument
groups to streamline the activities. All instruments in the circuit were removed from the lines.
The following procedures were used:
For gas lines: Gasket blowing with plant air was carried out starting from 1.0 barg up to 3.5 barg repeatedly,
until there was no rust / dust in the line. This was followed by nitrogen passivation / drying.
For liquid lines: Air blowing followed by water flushing was carried out. This was followed by nitrogen
passivation / drying.
For steam lines: Gradual warming of the header before insulation was applied for grease removal and rust
flushing through the trap bypass. Then steam blowing at full capacity was carried out for half an hour by
diverting the open end at a safe location. The header was allowed to cool. This cycle was repeated again till
clear condensate was discharged in the trap bypass.
For Running Machines: There was a pair of process pumps in each service. One pump online and one
spare. With the higher capacity, some pumps were replaced for higher capacity. The main crude feed
pumps and refining column reflux pumps were replaced. With spare pumps, the plant operation was not
interrupted during the pump changes. Each replacement took 12 days and included the modification of the
base, pipeline, motor, and other ancillary pieces.
Likewise, four control valves were replaced via proper coordination between the operations and project
teams. The prefabricated loops were also washed or blown and then dried with nitrogen. These were kept
inert and sealed at their ends until they were to hooked up during the shutdown. This also helped reduce
the pre-commissioning time for the plant. The start-up boiler feed water circulation pump was commissioned
and stabilized prior to shutdown as soon as the errection of the reactor steam drum system was completed.
Both Methanol-I and SGGU operate independently. It was not necessary to shutdown SGGU for the
commissioning of Isothermal reactor in the Methanol-I synthesis loop. The natural gas compressors in the
SGGU plant get cooling water from the Methanol-I plant header. Since cooling tower was to be taken
offline, temporary arrangements to supply an alternate water source was planned to keep the natural gas
compressors in the SGGU running. This was implemented prior to shutdown, avoiding a stoppage of the
SGGU plant.
Reactor Catalyst Charging
This was the first reactor of its kind at GNFC with spiral wound coils within the shell. The catalyst is to be
charged on the shell side, while the cooling medium (boiler feed water) flows in the tubes via thermosiphon.
During the startup, the boiler feed water circulation pump maintains the water circulation.