DETAILED DESCRIPTION OF SYNTHESIS CONVERTER

The document provides an in-detail simplistic explanation of the synthesis converter

internals. The description is based on my views what I have encountered during the recent

replacement of the same internals. The description might be a bit different from the already

existing internals available at your/other firms. The complex design has been explained in possibly

simplest form as possible. Kindly go through the attached diagrammatic representation for proper

explanation of the mentioned notes. The displayed diagram will be explanatory with combination of

its reflection adjacently. I hope this document helps in clearing the doubts for all the engaged

process engineers/professionals operating in the same field.

To describe the synthesis converter internals I have partitioned as needed for explanation

First/Top basket

Second/Bottom basket

Low pressure shell

Inter bed heat exchanger

Feed effluent heat exchanger

The top five points (two warm shot inlets, quench inlet, top product outlet and fire heater

inlet) have bellows welded to ring gasket placed on main vessel top channel. The space between the

main vessel top channel and the LP shell top cover accommodates pipes and elbows for guiding the

gases inside the converter.

LOW PRESSURE SHELL

The LP shell is placed inside the main vessel. It accommodates all the remaining internals of

the converter. The space in between the LP shell and main vessel is actually the path for the cold

gas flow from bottom inlet. At the bottom most point of the LP shell, we have a product outlet point

on centre and another offset extended arm for guiding the LP shell into the main vessel for boxing

up/alignment. The bottom product outlet line has a bellow welded to a ring gasket placed on the

main vessel which later goes through the steam boiler.

FIRST/TOP BASKET

Top basket consists of concentric basket assembly (Resembling stacked donuts). The basket

has a perforated sheet folded to form a cylinder on the inner side. Whereas on the outer end the

same perforated sheet is fabricated in the form of scallops for accommodating the feed synthesis

gas* as inlet point. Between these two sheets the catalyst placement is done. It is clear to us that the

synthesis gas flow is radial (from outside to inside) across the bed as this makes it certain for the

proper utilization of the catalyst surface for conversion.

*indicates the feed synthesis gas is made up of preheated warm shot gas and preheated cold shot gas during normal operation and

also accommodates cold gas quench & fired heater outlet gas in case of startup or abnormal operation.

INTER-BED HEAT EXCHANGER

The heat exchanger comprises of the two mentioned warm-shot inlet gas lines which extend

up to the bottom and are then preheated on the tube side with upward flow whereas the product

outlet of the first catalyst bed provides the heat on the shell side on its downward flow. The tube

side outlet at the top consist of two guide vanes for proper gas distribution and ensure thorough

mixing with the already preheated bottom cold shot gas flow.

SECOND/BOTTOM BASKET

Bottom basket consists of concentric basket assembly (Resembling stacked donuts). The

basket has a perforated sheet folded to form a cylinder on the inner side. Whereas on the outer end

the same perforated sheet is fabricated in the form of scallops for accommodating the feed gas as

inlet point. Between these two sheets the catalyst placement is done. It is clear to us that the

synthesis gas flow is radial (from outside to inside) across the bed as this makes it certain for the

proper utilization of the catalyst surface for conversion. The description of both the baskets might

be similar but the volume is more for the bottom bed (nearly three times).

# here indicates that the synthesis gas is the outlet product gas of shell side of inter- bed heat exchanger.

FEED/EFFLUENT HEAT EXCHANGER

The heat exchanger comprises of the cold shot gas moving from the annular space with

downward flow into the shell side for getting preheated and then moving out through the adjacent

annular space with upward flow. The tube side consists of second catalyst bed outlet gas with a part

of it moving out upwards and the other part moving in downward direction. The product gas

moving upwards is also partly responsible for imparting heat to the cold gas inlet on the shell side

of feed/effluent heat exchanger.