What two operators saw after replacing brick checkerwalls with interlocking ceramic blocks, as published in PTQ 2014.
The first goal was a checkerwall that stays standing.
The second was one that improves the reaction furnace.
This PTQ article reports field experience with the Blasch VectorWall, an interlocking ceramic checkerwall for the Claus reaction furnace of a sulfur recovery unit. It describes why brick checkerwalls fail, how the mortar free HexWall design was turned into a mixing wall, and what two operators measured after the change: no more wall failures and vibration, a hotter zone 1 and about 30% more sour water stripper gas processed in one refinery SRU.
Once the walls stopped falling down, operators began to ask what a checkerwall is actually for, and the answer was time, temperature and turbulence.
At the gas plant, cylindrical and box shaped brick checkerwalls had been used for over 20 years and failed repeatedly. The investigation named thermal cycling during start-up and shutdown, mortar failure, vibration and liquid carryover as causes, and found a design deficiency in the wall itself.
The furnace normally runs at 980 to 1,090 °C, but the hot face has to withstand 1,370 to 1,650 °C during start-up firing on natural gas. Mortar joints do not survive that cycling for long.
The answer was the HexWall checkerwall: hexagonal blocks stacked dry and locked by tabs and slots, with no mortar. Round openings turn every unsupported span into an arch, which carries load in compression. Blocks are 9 in. wide for most furnaces and 18 in. for walls above 5 m, and they can be reused.
Blasch then fitted a vectoring hood, the Vector Tile, into the outlet of each block. Each tile redirects its share of the flow, and together they create a vortex with a long path length and a tight residence time distribution. That version is the VectorWall mixing checkerwall. At the time of writing, nearly two dozen VectorWalls and about 100 HexWalls were in service.
The second case is a Claus reaction furnace in an Asian refinery SRU, 2.1 m inside diameter and about 9 m long, processing amine acid gas and sour water stripper gas with ammonia. Before the revamp, a damaged 9 in. brick wall caused heavy vibration at high throughput, zone 1 could not be run hot, and ammonium salts deposited downstream.
The furnace was relined and fitted with a VectorWall in May 2012. Afterwards zone 1 ran at about 1,400 °C, zone 2 dropped by about 200 °C to below 1,000 °C, the sour water stripper gas processed rose by about 30% to 2,000 m³/h, and the vibration stopped. The authors link the hotter zone 1 to better ammonia destruction. The same plant is described as a case study on furnace vibration.
The flow design was based on simplified cold flow modeling, without burner configuration, temperature effects or reaction kinetics. The field data support the direction of the model, and the authors say so without claiming more.
If your checkerwall or choke ring is rebuilt every turnaround, or your zone 1 runs too cold for ammonia destruction, the wall is a design variable, not only a maintenance item. The Claus reaction furnace page explains where the wall sits and what it changes.
The paper does not give a pressure drop figure. Later CFD work for an Asian refinery SRU found about 900 Pa less pressure drop than a choke ring.
Yes. The blocks are stacked without mortar, so they can be taken down and set again.
It is either set into a slot in the lining or against the hot face brick, with one course of brick on each side to lock it in.
Claus reaction furnaces in a gas plant and a refinery, plus HexWalls in sulfuric acid plants that were still in service after five years.
Tell us the furnace diameter, the feed and what happens to the wall today. A Blasch engineer looks at the mechanics and the flow together.
