Sulphur Tail Gas Thermal Oxidizer
Thermal Oxidisers for Sulphur Recovery Unit Tail Gas
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High-temperature destruction of reduced sulphur compounds in SRU tail gas
CRA’s Sulphur Tail Gas Thermal Oxidisers are engineered to provide reliable, high-efficiency destruction of reduced sulphur compounds, such as H₂S, COS, and CS₂, commonly found in Claus unit tail gas and sulphur recovery processes. Operating at high temperatures with optimised residence times, our systems are designed for complete oxidation and stable performance under variable process loads. Built with corrosion-resistant materials, high-integrity refractory linings, and optional heat recovery or pre and post scrubber integration, these oxidisers are designed to meet strict emission limits for SO₂, NOₓ, CO, and unburnt hydrocarbons.
DRE
>99.9%
Design and build
In-house
Target Compounds
H₂S, COS, CS₂
Application
SRU tail gas
What is a Sulphur Tail Gas Thermal Oxidizer?
A sulphur tail gas thermal oxidiser is a high-temperature combustion unit designed to treat the tail gas stream from a Claus sulphur recovery unit, destroying residual reduced sulphur compounds that escape the SRU reaction stages and cannot be discharged directly to atmosphere.
How it works
Tail gas enters the combustion chamber and burns at a temperature and duration engineered to fully oxidise the sulphur compounds it carries.
Tail gas burns at a temperature set for the sulphur load and the process design.
Residence time is engineered to fully oxidise H₂S, COS, CS₂, and mercaptans into SO₂ before the gas exits the chamber.
Optional heat recovery, pre-combustion scrubbing, or post-combustion scrubbing stages can be integrated to manage the converted SO₂ and meet site-specific emission limits.
Key Benefits
Total oxidation of sulphur-bearing compounds, including H₂S, COS, and mercaptans
The combustion temperature is set for the sulphur load and the process design, and the chamber is built to run at it continuously.
Detailed CFD, process simulations, and strict QC are used to achieve adequate residence times and high DRE
Engineered to absorb load swings from SRU upsets, start-ups, or shutdowns with stable combustion
Advanced pre- and post-combustion scrubbing technologies engineered to meet the specific needs of each application
The CRA Edge
With 30+ years of combustion design experience, CRA delivers oxidisers built for extreme sulphur service
Thermal modelling, materials R&D, and fabrication all under one roof ensure speed and precision
ISO 9001 certified; designs aligned with ASME, API and CE
Engineered for uptime, safety, and long service life in the harshest industrial environments
Applications
Built to help you specify.
Sizing tools, decision guides, and technical references. Use them before, during, and after your evaluation.
Frequently Asked Questions
When is a sulphur tail gas thermal oxidiser the right choice?
A sulphur tail gas thermal oxidiser is the right choice where a gas stream carrying reduced sulphur compounds, H₂S, COS, CS₂ and mercaptans, must be oxidised to SO₂ before release or scrubbing. The main duty is Claus sulphur recovery unit tail gas at refineries and gas processing plants, with sulphur-bearing petrochemical vents, hydrogen plant off-gas and chemical processes handling sulphur compounds as further applications. Specialised equipment is needed because H₂S and SO₂ attack standard materials, sulphur loading swings widely between normal and upset operation, high temperatures are required for complete oxidation, and the SO₂, NOx and hydrocarbon limits are tight. CRA builds these oxidisers for sulphur service.
How does a sulphur tail gas thermal oxidiser handle variable SRU loads?
The oxidiser is designed to absorb the load swings that occur during Claus unit start-up, shutdown and upsets, when the H₂S concentration rises well above its normal level. Wide-turndown burners and modulating fuel control follow the change in heat input, and the refractory lining is built for repeated thermal cycling. The controls hold the combustion temperature through these swings, and the safety system covers the upset cases.
What destruction efficiency does a sulphur tail gas thermal oxidiser achieve?
A properly engineered sulphur tail gas thermal oxidiser is designed for destruction efficiency above 99.9% for reduced sulphur compounds, with H₂S, COS and CS₂ destruction above 99.9% in the design basis. Oxidation converts these compounds to SO₂, water and CO₂. Stack SO₂ is typically below 250 ppm, or lower where local regulations require, with caustic or lime scrubbing added downstream when the limit demands it. The design points behind this performance are a combustion temperature matched to the sulphur load, enough residence time and excess oxygen, even temperature distribution and continuous SO₂, O₂ and CO monitoring.
Which operating parameters matter most for a sulphur tail gas thermal oxidiser?
Operating temperature, residence time, excess oxygen, refractory and materials decide performance. The chamber is sized for the worst-case flow, the controls balance complete destruction against refractory protection during high H₂S upsets, and the ductwork and stack use acid-resistant materials for the SO₂ and SO₃ environment.
Will the figures in these FAQs apply to my tail gas stream?
The figures in these FAQs are general guidance for sulphur tail gas service, and the performance of a specific unit depends on the tail gas composition, flow, sulphur load swings, emission limits and site conditions of the plant. CRA reviews the process data, normal and upset cases included, before sizing the chamber, burner, refractory and controls. For a specific application, send the tail gas analysis, flow cases, available fuel and the SO₂ and NOx limits that apply, and CRA's engineering team reviews the design basis with you before any proposal is prepared.