Interlocking hex blocks with angled tiles that steer the gas in Claus, incinerator and sulfuric acid furnaces.
Every opening in the wall turns the gas a little.
Together they decide how long it stays hot.
A vectoring checkerwall improves mixing in a Claus reaction furnace because every opening carries an angled tile that turns the gas, and together the tiles set the whole flow into a controlled swirl. The gas takes a longer path and leaves with a narrow residence time distribution, close to plug flow, so very little of it passes the furnace too fast to react. The tiles also reflect radiant heat back into zone 1, where ammonia and BTEX have to be destroyed, and shield the waste heat boiler tubesheet.
Most Claus furnaces still use a choke ring or a brick checkerwall to hold the gas in the hot zone.
VectorWall is built on HexWall: six-sided ceramic blocks that lock together with tabs and slots and carry round openings. Vector tiles, also called vectoring hoods, sit at the outlet of the openings.
Each tile turns the gas leaving its block. Arranged across the wall, the tiles create a designed flow field, usually one large swirl with a long path through the furnace. The measure behind the design is the old rule of combustion: time, temperature and turbulence.
The tiles also block the direct line of sight through the wall without blocking the flow. A published comparison put first generation tiles at 50% of the radiant heat and the third generation at 100%.
Single zone, straight through. One large swirl, plug flow from wall to outlet. For homogeneous feeds, Claus feeds with 50% H2S or more, and sulfur burning furnaces.
Two zones, split flow. Blocks at the edge are closed like a choke ring, the center carries vector tiles. Zone 1 runs hotter with back mixing to destroy ammonia and BTEX, zone 2 runs cooler with plug flow and less NOx. For Claus feeds below 50% H2S or with sour water stripper gas, and for spent acid furnaces.
The target temperatures come from the chemistry: about 1,050 °C to destroy BTEX and about 1,300 °C for ammonia, according to a 2020 paper on VectorWall geometries in sulfur recovery.
A furnace does not need more volume to destroy more ammonia: it needs every part of the gas to spend enough time hot enough, and the wall decides that.
An independent CFD study of a refinery SRU in Asia compared a choke ring with a VectorWall. With the choke ring, 22.5% of the flow stayed below the residence time needed to destroy ammonia; with VectorWall, none did. Pressure drop was about 900 Pa lower.
For a 500 t/d SRU that can run zone 1 about 100 °C hotter without co-firing fuel gas, a published calculation estimated energy savings of more than $250,000 per year at $3 per million Btu. In units with oxygen enrichment, the same paper put the possible saving in oxygen at 8 to 20%.
Published results, each with the unit it was measured in.
Claus SRU revamp, Asia, 2012
Zone 1 rose to about 1,400 °C while zone 2 fell by about 200 °C to below 1,000 °C. Sour water stripper gas throughput rose by about 30% to 2,000 m3/h, and the furnace vibrations stopped.
Claus SRU incinerator, US Mid-Continent, 2009
Excess oxygen fell by 2 percentage points and sulfur carryover was nearly eliminated. The shell stayed above 500 °F, with no acid condensation.
Spent acid regeneration, 2015
Staged combustion with oxygen enrichment brought NOx from 120 to 150 mg/Nm3 at 900 t/d down to the target of 100 mg/Nm3 at 1,076 t/d.
Acid regeneration plant, USA
Two baffle walls failed in a sulfur burning unit of 14 ft diameter. Seven crates of blocks shipped within a day, and the unit was back on line less than two weeks after the first call.
Claus reaction furnaces, tail gas incinerators and thermal oxidizers in sulfur recovery, and sulfur burning and spent acid regeneration furnaces in sulfuric acid plants, across refining and chemical processing. By 2018 more than 100 systems were installed, including SRUs above 1,000 t/d. In 2014, DuPont MECS made VectorWall the standard internals for all new and revamped spent acid regeneration furnaces of its design. The field record from 2014 is in the PTQ article on VectorWall.
The blocks come in three widths, 9, 13.5 and 18 inches (230, 345 and 460 mm); the largest walls, above 5 m diameter, use the 18 inch block. They are cast in a creep resistant mullite bonded composition, set without mortar, and can be taken down and set again at a turnaround. More on mullite, and on the other self-supporting structures Blasch builds this way.
No. Against a choke ring it lowers it. The CFD study for a refinery SRU found about 900 Pa less, and single VectorWalls have replaced several baffle walls in sulfur burners.
The blocks lock with tabs and slots on all six sides, which keeps the wall standing in upset conditions where loose stacked cylinders fall.
Yes. The HexWall base is used in oxygen-enriched furnaces, and several sulfur recovery units run VectorWall with oxygen enrichment.
Yes. VectorWall replaces choke rings, brick checkerwalls or baffle walls during a turnaround, mounted in the lining like the wall it replaces.
Send the furnace diameter, the feed and the problem you see. A Blasch engineer proposes the wall configuration for your unit.
