Revamp of Syngas Scrubber

Customer:	Fertilizer Company.
Location:	Western India.
Tower Name:	Syngas Scrubber.
Tower Diameter:	3048 mm.
Mass Transfer Equipment:	Sieve Trays.

History:
The client operates integrated Ammonia Urea complex and is also India's largest producer of Formic Acid, Acetic Acid and Methanol. It holds world's largest single stream, fuel oil based Ammonia-Urea plant using “Texaco Partial Oxidation of Fuel Oil” Process for production of Syngas (Synthesis Gas).

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 12000C and 15000C and at pressures above 18 atm.

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 2500C by cold water and are then fed to the scrubber. This gas is scrubbed in a tray column having 4 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 KEVIN to study the system and resolve the problem.

Problem analysis:

KEVIN studied the existing system and the construction of existing trays and following observations were noted
- The main design constraint of the trays for this column was the extremely high uplift pressure of 6 bars at start up, which lasted for about 15 minutes.
- These gases were impinging on the trays, the impingement force was found greatest on the lowermost tray.

The probable reasons for failure were :
- The direction of major beam was found to be perpendicular to the flow which in actual should be parallel to the flow. The parallel direction of beam is important in order to distribute & 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 KEVIN suggested few modifications in the KEVIN suggested few modification.

KEVIN also suggested providing an impingement strip over each row of sieves tray 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:
Plant capacity was increased by 20%. LAB slippage was reduced to less than 5% and the ACI also improved to desired level.