A refinery Claus furnace that could not run hot enough to destroy ammonia, before and after a VectorWall in 2012.
Ammonia salts downstream and a furnace that shook at high rates.
The unit could not take more sour water gas
At a refinery in Asia, the reaction furnace of a Claus sulfur recovery unit got a VectorWall in place of its brick checker wall in May 2012. Afterwards zone 1 ran at about 1,400 °C, zone 2 about 200 °C cooler at below 1,000 °C, the unit took about 30% more sour water stripper gas, up to 2,000 m³/h, and the furnace vibration stopped, as reported in PTQ in 2014.
The furnace is the heart of one of the refinery's sulfur recovery units: refractory lined, 2.1 m inside diameter and about 9 m long. It takes two acid gas streams from the hydrodesulfurization plant. One is clean sour gas from amine regeneration, mostly hydrogen sulfide. The other is sour water stripper gas, with roughly equal parts ammonia, hydrogen sulfide and water vapor.
A standard 9 inch brick checker wall split the furnace into two zones, with acid gas fed at the burner and again just behind the wall. At high throughput the furnace vibrated and roared, believed to come from the damaged wall. Zone 1 could not be run hot, ammonia was not fully destroyed, and ammonium sulfate and bisulfate built up in downstream equipment.
Ammonia has to be destroyed in the first zone or it turns up as salt further down the train, so a wall that sends more heat back into zone 1 decides how much sour water gas the unit can accept.
In the May 2012 revamp the whole furnace got new insulating refractory, and the brick checker wall was replaced with a VectorWall. The wall was built against the insulating layer, with high alumina bricks as foundation wedges and castable backfill. Its blocks interlock without mortar. Vectoring tiles in the block outlets turn the flow into a swirl and reflect radiant heat back into zone 1.
| Measured value | Before the revamp | After the revamp |
|---|---|---|
| Zone 1 temperature | limited by vibration | about 1,400 °C |
| Zone 2 temperature | about 200 °C lower, below 1,000 °C | |
| Sour water stripper gas processed | about 30% more, 2,000 m³/h | |
| Furnace vibration | severe at high throughput | none observed |
The authors explain the cooler zone 2 by more ammonia being converted to nitrogen in zone 1, so less of it was left to burn behind the wall.
More sour water gas through the same furnace, fewer ammonium salt deposits to clean out of the train, and a furnace that no longer limits itself by shaking.
The wall used in this revamp, for Claus furnaces, incinerators and sulfuric acid plants.
Why the front zone of a Claus furnace has to be hot and well mixed. Ammonia and BTEX destruction
How a CFD study traced reaction furnace vibration to the choke ring.
In May 2012, together with new insulating refractory for the whole furnace.
More ammonia was destroyed in the hotter zone 1, so less was left to react in zone 2.
Zone 1 should run hot with some back mixing so ammonia is destroyed early. Zone 2 should run cooler with a narrow residence time distribution, which keeps NOx formation down.
No. The blocks interlock and are stacked dry. Only the foundation wedges and backfill against the lining use brick and castable.
Send the furnace dimensions, the acid gas streams and the current internals. A Blasch engineer looks at what a VectorWall could change in your zone 1.
