Sulfur removal | Sulfur recovery (TopClaus®)

TopClaus® sulfur recovery – combining the best of two proven technologies

The TopClaus® sulfur recovery solution combines

  • the industry-standard Claus gas desulfurizing process and
  • the Topsoe wet gas sulfuric acid process (WSA)

to achieve 99.9+% sulfur removal efficiency (SRE) from acid gases – at significantly lower cost of ownership. You get the best of two thoroughly proven sulfur recovery technologies – combined for even greater benefits.
The Claus part of the TopClaus® solution is identical to the Claus technology that you know.

TopClaus® Plant

How it works

TopClaus® integrates the well-known, well-proven Claus and WSA processes. Acid gases are treated in the Claus unit of the TopClaus® plant, resulting in recovery of elemental sulfur. The tail gases from the Claus unit are treated in the WSA unit, where the remaining sulfur compounds are converted to sulfuric acid. The sulfuric acid is then returned directly to the Claus reaction furnace for reprocessing to elemental sulfur, with no sulfuric acid left as by-product. However, it is entirely up to the plant operator to draw off some of the sulfuric acid for specific uses or for sale, if desired.

Oxygen enrichment by sulfuric acid

Sulfuric acid (H2SO4) is a particularly efficient oxygen carrier, reducing the volume flow through the Claus unit just like with conventional oxygen enrichment, but without the high-temperature issues of the latter.
In the WSA unit all combustibles in the Claus tail gas like H2, CO, SX, CS2, COS and H2S are converted into H2O, CO2 and SO2, and the SO2 is further processed to sulfuric acid. Thereby final incineration of the tail gas becomes redundant, thus reducing fuel consumption and cutting back on your CO2 emissions.

Lower CAPEX and OPEX

Using a WSA unit as a TGTU in the TopClaus® process also brings you other benefits. When oxidizing the sulfur components to sulfuric acid, the WSA unit recovers as much as 90% of the heat generated, in the form of valuable superheated high-pressure steam that you can use in other key refinery processes, or use to generate electricity. This is in contrast to the large amount of steam that would be required to regenerate the amine in a conventional TGTU unit, and results in big reductions in your plant’s operating costs and CO2 footprint.
50% lower operating costs, combined with a reduction in capital expenditure of up to 40%  compared to any conventional amine-based technology, provides you with a financially attractive, efficient and environmentally responsible solution for SRU design, be it a grassroot project or a revamp.

Boost reliability

In addition, the TopClaus® configuration gives refineries operating a sour water stripper (SWS) greater flexibility and SRU reliability because the SWS gas can be by-passed around the Claus unit to the WSA unit, allowing a lower operation temperature in the Claus reaction furnace and preventing ammonia from causing problems in the Claus unit.

Eliminate bottlenecks and boost capacity

Oxygen enrichment by using sulfuric acid in the Claus reaction furnace provides you with excellent opportunities for boosting the sulfur recovery capacity and/or the SRE of an existing Claus plant.

The TopClaus® payoffs

Combining the capabilities and benefits of Claus and WSA technologies makes it possible to shift the benchmarks for reliability and costs.

  • SRE >99.9%, with all sulfur compounds in the acid gas feed converted into elemental sulfur and/or commercial-grade sulfuric acid (if desired)
  • Up to 40% CAPEX reductions
  • Up to 50% lower OPEX
  • More attractive net present value

TopClaus® sulfur recovery benefits

A TopClaus® installation can easily cope with virtually any acid gas feedstock (even those with a significant ammonia and hydrocarbon content) and any Claus tail gas composition you may have to deal with.

  • Simple, robust and efficient plant
  • Combines and integrates proven technologies – the efficient features of WSA with the industry-standard sulfur-producing Claus process
  • Ideal for debottlenecking existing acid gas treatment plants, providing more uptime, increased capacity and/or lower emissions
  • Equally suitable for greenfield projects and revamps
  • H2SO4 is an efficient oxygen carrier, allowing higher throughput of the Claus unit
  • You can export high-pressure steam – often superheated – that your plant can use elsewhere, instead of importing steam for amine regeneration
  • Ammonia-related operational problems avoided because SWS gas treatment in the WSA unit makes sure ammonia is effectively burnt off

The TopClaus® technology has been developed by Haldor Topsoe and Comprimo, the leading licensor in gas treating and sulfur recovery technology.


Rasmus Atle Breivik

Rasmus Atle Breivik

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