1) The document outlines the step-by-step procedure for unloading the catalyst from a synthesis converter, including cooling down the catalyst bed, purging the synthesis loop with inert gas, dismantling connected pipelines and valves, and preparing for catalyst extraction. 2) The first basket catalyst is extracted using a vacuum system with inert gas bleed and safety precautions like breathing apparatus and safety ropes for workers inside the converter. 3) Once the first basket catalyst is extracted, the second basket catalyst is extracted following similar safety procedures, and then the second basket is removed along with the low pressure shell.

1. STEP BY STEP PROCEDURE FOR
SYNTHESIS CATALYST UNLOADING
COOLING DOWN & PURGING OF THE CONVERTER
Once the bed activity is brought down after stopping the synthesis gas flow to the converter,
try to cool down the catalyst bed to ambient temperature. This can be achieved by quenching the
converter with the same synthesis gas or by circulating an inert gas in the synthesis loop. Plan out
for purging the synthesis loop with inert gas without any time delay considering the time allotted
and capital invested for the project. Isolate the synthesis converter properly to do purging more
efficiently (This includes spading/blinding/blanking off). Use fresh inert gas (inert gas used over
here was nitrogen) for purging and avoid reutilization of used inert gas. Purging result can be
tested by checking the ammonia and hydrogen concentration at the vent point when the system is
at minimum pressure. Recommended result to be achieved for confirmation of purging for
hydrogen should be less than 0.2% and ammonia should be less than 5ppm.
DISMANTLING THE OBJECTING PIPELINES AND CONTROL VALVES
When the purging of synthesis loop is achieved, drop the control valves connected to
converter for servicing and box up blinds on the open ends. Process pipelines projecting at the top
of the converter have to be dismantled as an open area is needed during loading of the catalyst.
Converter catalyst loading is a very rare opportunity for an ammonia engineer. Inert gas bleed
should kept on to the converter continuously to avoid temperature spikes in the catalyst beds due
to oxygen ingression. Make sure that maintenance personals are looking after the top channel cover
stud bolt loosening and availability of the spares in case of gas cutting is needed for stud bolt
removal. At the bottom of the converter, release the converter connected boiler/heat exchanger for
proper separation of converter from synthesis loop. After dismantling the converter connected
pipelines, release the bellows which are welded to the ring gaskets for every opening (in some
cases bellows might not be available in the main design). After releasing the bellows do blank off
the open ends possibly with duct tapes. Remove the long thermowell from the guide tube cavity
with the help of the crane.
PREPARATION FOR FIRST BASKET CATALYST EXTRACTION
Arrangement has to be done for accommodating vacuum system for catalyst removal at the
nearby area. After loosening the top channel cover, drop it with the help of crane. Don’t forget to
blank off the open ends for the main central product outlet pipe as well as the concentric openings
adjacent to it. Inert gas bleed off with minimum positive pressure to the converter remains on
throughout the catalyst removal process because the catalyst is pyrophoric in its active form. From
now on the persons working inside the converter will be on lifelines on continuous basis till the
catalyst extraction is totally completed. It will be better if catalyst replacement job is taken up in
summer season.

2. After top channel cover dropping, (at the topmost part of the converter) pipelines for
guiding the synthesis gas into respective zones are present with bellows at bends helpful for
adjusting to the thermal and pressure fluctuations. Vendor will provide a temporary lid/cover to
accommodate the camera wire, breathing and exhaling lines for person working inside, safety rope
to pullout & a manway for man entry. Remove the pipelines and the first cover is visible which is
bolted to the LP shell. Loosen the bolts and remove the first cover with help of a crane. The first
basket is visible. Remove the second cover which is bolted to the first basket and the inter-bed heat
exchanger. First basket catalyst is visible and extraction can be initiated. Sufficient inert gas supply
should be available for the converter because extraction of catalyst using vacuum system leads to
excess inert gas requirement to avoid oxygen ingression.
FIRST BASKET CATALYST EXTRACTION
Catalyst extraction should be coordinated in a proper manner. A breathing apparatus
assembly with inbuilt communicating device (walkie-talkie) has to be provided to the person
working inside. A safety rope should be tied to the same person to evacuate him in case of
emergency and a rope ladder for proper entry and exit. A person should stand at the top and
supervise/communicate to the person working inside with a continuous watch on him. Three spare
persons should be present at top for pulling the person out in case of emergency. A person was able
to work inside the first basket for removal of catalyst for a period of 45-60 minutes. To
continuously monitor the camera’s live feed to give suggestions and maintain the breathing
apparatus assembly, sufficient persons should be allotted. To loosen the catalyst for extraction,
make use of drilling machine with pressurized inert gas supply. Avoid pressurized air usage for
pneumatic drilling.
There should be a proper disposal plan for the spent catalyst. Once the spent catalyst
collecting trailer is filled, it should be discarded in an open area and water should be sprayed on it
continuously to avoid catching fire. Try to spray water and avoid submerging with excess water to
abide pollution control norms.
To make it possible for separation of first basket, the thermowell guide tube has to be cut at
the first basket bottom before lifting it. When catalyst extraction for the first basket is completed,
box up the second cover to the first basket (as it has hooks for lifting) and remove the bolts
connecting the first basket to LP shell. Now it is possible to lift the first basket and place it at ground
level for inspection and speculation.
SECOND BASKET CATALYST EXTRACTION
The third cover has to be dismantled and removed for accessing the catalyst in second
basket for extraction. Similar procedure has to be followed for second basket catalyst extraction as
mentioned for first basket catalyst extraction. After catalyst extraction completion, inert gas supply
should be maintained because catalyst dust is still present inside the second basket. It is better to
remove the second basket with the LP shell as it is time saving. Now the inert gas supply can be cut
off. Later main vessel related inspection and engineering activities can be initiated.