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New low-density titania catalyst for improved sulphur recovery

Summary

Axens has developed a new titania-based catalyst named CRS 41, which has a much larger porosity than its renowned predecessor, CRS 31 catalyst. Thanks to an improved catalyst manufacturing process and a new recipe, the porosity of CRS 41 has been increased while preserving the mechanical resistance for loading, allowing customers to optimise their capex by either reducing the Claus reactor size or loading volume of TiO2 catalyst.

Abstract

Increasingly stringent environmental legislation requires maximising sulphur recovery yields. That explains the growing role of titania (TiO2) catalysts in SRUs, which is accompanied by the arrival of high-activity tail gas treatment catalysts on the market. Titania-based catalysts are used because they can efficiently convert all sulphur species to elemental sulphur, even under conditions that deactivate conventional alumina catalysts. Furthermore, the use of titania facilitates the conversion of COS and CS2 at low temperature, which is essential if hydrocarbons are present in the acid gas feed. Axens’ titania-based catalyst, CRS 31, has extensive commercial experience with thousands of tonnes loaded worldwide, and is considered to be the benchmark titania catalyst. It contains high amounts of TiO2, which is very active towards hydrolysis of sulphided species. However, not all the titanium dioxide of CRS 31 contributes to the catalytic activity, since not all of it is accessible to the gaseous reagents. Keywords: titania catalyst, low density catalyst, sulphur recovery, Claus, CRS 41, porosity, loading volume, reactor size, Claus conversion, COS, CS2, Axens

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New impaction technology for acid plant towers

Summary

MECS, Inc. (MECS) has developed a new impaction-based mist eliminator called Brink® Prime Impact™, which offers equivalent or improved efficiency at higher throughput and the same pressure drop as traditional impaction beds, resulting in the ability to debottleneck existing inter-pass absorption towers and final absorption towers in sulphuric acid plants or design new or replacement towers with smaller diameters, thus reducing investment cost.

Abstract

Fibre bed mist eliminators have a long history of use in industrial applications and are utilised in a wide variety of processes. Originally invented and developed by Joe Brink in the 1950s, the use of the products that comprise this technology has become ubiquitous with removal of liquid mist and soluble solids from a gas stream throughout industry. Keywords: fibre bed mist eliminator, Brink Prime Impact, pressure drop, impaction bed, absorption tower, sulphuric acid plant, MECS

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Replacement of upper part of a co-current flow quench tower

Summary

Gavin Floyd (Eco Services Operations Corp.) and Roland Günther (STEULER-KCH GmbH)

Abstract

This case study reports on the successful collaboration of two experienced partner companies to replace the problematic upper part of a co-current flow quench tower in a spent acid plant and shows the benefits of using resistant, pre-lined workshop fabricated equipment. Keywords: acid tower, revamping, quench tower, brick lining system, workshop fabricated equipment, Steuler, Eco Services

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Back to the roots: single versus double absorption

Summary

With increased demands to reduce SO2 emissions and lower energy consumption, Eduardo Almeida and Nelson Clark of Clark Solutions highlight the advantages of single absorption sulphuric acid plants compared to double absorption plants.

Abstract

In the 1950s, led by environmentalist pressure following events such as the Great Smog of London in 1952, industries emitting sulphur dioxide (SO2) began searching for alternatives. Specifically in the sulphuric acid industry, the solution was to increase the conversion of SO2 to SO3 from 96 – 97% to 99.6 – 99.7%, favouring thermodynamics by the intermediate removal of oxidised SO3. This transformation changed single absorption plants into double absorption, reducing emissions by both increasing energy consumption and decreasing specific steam generation. Keywords: sulphuric acid plant, SO2 emissions, energy consumption, single absorption plant, SA plant, double absorption plant, DA plant, intermediate circuit, regenerative, tail gas scrubber, Clark Solutions

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Cobalt-molybdenum catalyst activation in low temperature TGUs – Part 1

Summary

Cobalt-molybdenum (CoMo) catalysts are integral components of tail gas units (TGUs), playing a vital role in reducing harmful sulphur dioxide (SO2) emissions arising from Claus sulphur recovery units. Effective activation of these catalysts is essential for their optimal performance. The consequence of sulphiding at low temperatures and atmospheric pressure in low temperature TGUs is to compromise effectiveness of catalyst activation. In the first part of this two-part article, Michael Huffmaster, Consultant, explores CoMo catalyst activation at low pressure, focusing on sulphiding reaction pathways and the impact of temperature and the composition of the sulphiding media on reaction kinetics, specifically the concentration of H2, H2S, and H2O.

Abstract

Cobalt-molybdenum (CoMo–Al2O3) catalysts are integral components of tail gas units, playing a vital role in reducing harmful sulphur dioxide (SO2) emissions from Claus sulphur recovery units in refineries and gas plants. The catalyst function is to convert all sulphur species from the Claus unit to hydrogen sulphide (H2S) in the hydrogenation reactor. This H2S is recovered via an amine system and recycled to the upstream Claus unit. Relatively sulphur-free off gas is incinerated and released to atmosphere. Keywords: Claus tail gas treating, catalyst, cobalt-molybdenum, tail gas unit, sulphur recovery, catalyst activation, sulphiding, low temperature TGU, catalyst activity, sulphur emission

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