Background
The client operates an integrated ammonia urea complex and is also India's largest producer of formic acid, acetic acid and methanol. It holds the world's largest single stream, fuel oil based ammonia urea plant using Texaco Partial Oxidation of Fuel Oil Process for production of synthesis gas (syngas).

Process Overview
The Texaco Gasification Process converts organic materials into syngas, a mixture of hydrogen and carbon monoxide. The feed reacts with a limited amount of oxygen (partial oxidation) in a refractory-lined reactor at temperatures between 12000°C (21632 °F) and 15000°C (27032°F) and at pressures above 18 atm.

The syngas scrubber is used to wash the gases coming out of the fuel oil gassifier. The hot gases coming out of the quencher are cooled to 2500°C (4532°F) by cold water and are then fed into the scrubber. The gases are scrubbed in a tray column having four trays for soot and condensate removal. After scrubbing the gases are sent to the process section.

Customer Requirements
During start-up operation dislodging of trays was occurring, hence the customer approached Munters to study the system and resolve the problem.

Problem analysis
Munters studied the existing system and the construction of existing trays and the following observations were noted:

• The main design constraint of the trays for the column was the extremely high uplift pressure of 6 bars at start-up, which lasted for about 15 minutes
• The gases were impinging on the trays, the impingement force was found greatest on the lowest tray



Probable reasons for failure

• The direction of major beam was found to be perpendicular to the flow. This should have been parallel to the flow. The parallel direction of the beam is important in order to distribute and maintain uniform upward force across the tray deck.
• The existing tray clamping method and also the bolting pitch was found to be inadequate in overcoming the initial upward thrust thus dislodging the trays
• Additional arrangement of sure cleats was not provided

Solutions provided
After studying the system and checking the mechanical design calculations Munters suggested a few modifications.

Other suggestions included providing an impingement strip over each row of sieve trays to further facilitate the soot removal.
Accordingly, new trays with additional features such as sure cleats, stiffener angles on the tray integral beam and lock nuts for clamping assembly and impingement strips were mechanically designed, manufactured, supplied and installed.

Results achieved


• The problem of dislodgement was solved permanently
• Improvement in column performance due to lower soot carry over was achieved