H2S Concentration in Acid Gas Removal
Solution Overview
Problem
Current methods for acid gas removal from syngas, particularly H2S, are inefficient at high pressures due to low selectivity of solvents like DMEPG, resulting in insufficient H2S concentration for Claus units, requiring additional costly processing steps or enrichment processes that often fail to produce a suitable acid gas stream.
Innovation Solution
A syngas treatment process involving an absorber, flash vessel, and regenerator configuration that uses a lean solvent to selectively remove H2S and CO2, followed by flashing and recycling of CO2-enriched gas to enhance H2S concentration, achieving an H2S-rich acid gas stream suitable for Claus plants through multiple flash stages and heat exchanger usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an H2S selective solvent is used to remove H2S from syngas, then H2S removal efficiency is improved, but CO2 co-absorption increases and H2S concentration in acid gas decreases
Solution Approach 1:
The acid gas removal process is divided into multiple absorption stages with intermediate CO2 stripping steps. The rich solvent from each absorption stage is flashed to remove CO2 before entering the next stage, segmenting the overall process to prevent CO2 accumulation and maintain high H2S concentration in the final acid gas product.
Solution Approach 2:
A flash drum is introduced as an intermediary device between the absorption column and regenerator. This flash drum selectively strips CO2 from the rich solvent through pressure reduction and heating, acting as a mediator that separates CO2 from H2S before the solvent enters the regenerator, thereby producing acid gas with high H2S concentration.
2Measurement precision
If high solvent circulation is used to meet sulfur specifications, then H2S removal is improved, but CO2 co-absorption increases and dilutes H2S content
Solution Approach 1:
CO2 is removed from the rich solvent through flashing before the solvent enters the regenerator. This preliminary action prevents CO2 from being carried over into the acid gas product, allowing the system to use sufficient solvent circulation for complete H2S removal without diluting the final acid gas H2S concentration.
3Quantity of substance
If fractionation columns are used for acid gas enrichment at low pressure, then acid gas concentration is improved, but the process fails at high pressures
Solution Approach 1:
The process uses pressure reduction and temperature increase in the flash drum to change the physical parameters of the rich solvent. By flashing the heated rich solvent at reduced pressure, CO2 is selectively vaporized and removed, achieving acid gas enrichment that works effectively at the high pressures typical of gasification plants.
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
The process effectively increases the H2S concentration to above 40 mol % in the acid gas stream, reducing CO2 content in syngas and achieving a suitable feed for Claus plants while minimizing energy consumption and operational costs.
Implementation Method 1
an absorber that receives the syngas and a lean solvent, and that produces a treated (typically CO2-containing) syngas and a rich solvent comprising H2S and CO2
Implementation Method 2
A flash vessel is coupled to the absorber, receives the rich solvent, and produces a flash gas that is enriched in CO2 and a flashed rich solvent comprising H2S
Implementation Method 3
a first heat exchanger heats the rich solvent using heat from the lean solvent
Data Source
AI summary
A syngas treatment plant is configured to remove sulfurous compounds from syngas in a configuration having two flash stages for a physical solvent to so enrich the acid gas to at least 40 mol % H2S or higher as required by the Claus unit and to flash and recycle CO2 back to the syngas feed. Contemplated methods and configurations advantageously remove sulfur to less than 10 ppmv while increasing H2S selectivity at high pressure operation to thereby allow production of an H2S stream that is suitable as feed gas to a Claus plant.