Claus Unit Tail Gas Catalyst Sequence for Sulfur Recovery
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Solution Overview
Problem
The conventional modified Claus process for transforming H2S into elemental sulfur results in inefficiencies due to catalyst deactivation, leading to reduced sulfur recovery yield and increased atmospheric emissions, as well as increased COS formation and energy consumption.
Innovation Solution
A process involving a sequence of catalysts, where the first catalyst comprises cobalt, molybdenum, and an alumina support, and the second catalyst includes titanium or zirconium oxide with alkaline-earth components, used in series to enhance hydrogenation and hydrolysis reactions without increasing reaction temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the temperature of the hydrogenation reactor is raised to compensate for catalyst deactivation, then the catalyst activity is maintained, but the energy consumption increases and catalyst ageing accelerates
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst by incorporating alkaline-earth metals (Ca, Sr, Ba) at controlled concentrations (0.1-5 wt%) into the CoMo catalyst system. This compositional modification allows the catalyst to maintain high activity at lower temperatures, avoiding the energy penalty and accelerated ageing associated with thermal compensation
2Reliability
If the temperature of the hydrogenation reactor is raised to compensate for catalyst deactivation, then the catalyst activity is maintained, but the catalyst ageing accelerates
Solution Approach 1:
The patent modifies the catalyst's chemical composition by adding alkaline-earth metals which fundamentally change the catalyst's stability properties. This compositional parameter change enables the catalyst to resist thermal degradation and maintain structural integrity at operating temperatures, thereby extending its operational lifespan without requiring temperature increases
3Device complexity
If a conventional hydrogenation catalyst is used, then the process is simple, but the conversion of COS and CS2 into H2S is insufficient leading to increased atmospheric emissions
Solution Approach 1:
The patent creates a composite catalyst system combining CoMo with alkaline-earth metals (Ca, Sr, Ba). This composite material integrates the hydrogenation capability of CoMo with the COS/CS2 conversion enhancement provided by alkaline-earth metals, achieving superior pollutant conversion while maintaining process simplicity
Solution Approach 2:
The modified catalyst performs multiple functions simultaneously: it catalyzes the hydrogenation of sulphur compounds to H2S, promotes the hydrolysis of COS and CS2, and maintains high activity over extended periods. This multi-functionality eliminates the need for additional treatment stages while reducing emissions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the conversion of COS and CS2 into H2S, maintaining catalyst activity and reducing energy consumption, thereby enhancing sulfur recovery yield and minimizing atmospheric emissions.
Implementation Method 1
The catalyst can allow hydrogenation and/or hydrolysis of all of the sulphur-containing compounds present (including traces of sulphur vapour) into H2S
Implementation Method 2
CS2+2H2O→CO2+2H2S
Implementation Method 3
catalytic reactors (usually two or three) placed in series which are intended to carry out the Claus reaction
Data Source
AI summary
For conversion of sulphur-containing compounds present in a gas comprising H2S and sulphur-containing compounds into additional H2S, a step A of contacting the gas with a reducing gas and a hydrogenation catalyst comprising cobalt, molybdenum and an alumina support, the sum of cobalt and molybdenum, in the oxide form, being 3% to 25% by weight, the surface area of alumina being more than 140 m2/g. In step B, effluent gas from step A is contacted with a catalyst comprising at least one alkaline-earth element, at least one dopant being iron, cobalt or molybdenum and at least one compound of titanium oxide and/or zirconium oxide, the catalyst for step B) being either in bulk or supported.