Two-Stage UCSRP Process for Ultra-Low Sulfur Removal
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Solution Overview
Problem
Current sulfur removal technologies face challenges in achieving ultra-low sulfur levels in gaseous streams, particularly in the UCSRP process when operating in excess SO2 mode for H2S-laden streams with high CO2 levels, leading to high capital and operating costs for additional processing steps to meet stringent SO2 emission targets.
Innovation Solution
A two-stage UCSRP process is implemented, where the first stage operates in excess SO2 mode to minimize solvent recirculation and the second stage in excess H2S mode to produce a product gas with low H2S and no residual SO2, potentially incorporating a COS hydrolysis reactor for further sulfur reduction, thereby reducing the need for additional sulfur removal technologies and minimizing overall costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional single-stage UCSRP process operates in excess SO2 mode to remove H2S, then H2S removal efficiency is improved, but SO2 levels in product gas increase requiring additional costly processing steps
Solution Approach 1:
The single-stage UCSRP process is divided into two sequential stages: first stage operates in excess SO2 mode to maximize H2S removal efficiency, second stage operates in excess H2S mode to remove residual SO2. This segmentation allows each stage to be optimized for its specific function, resolving the contradiction between H2S removal efficiency and SO2 emission control.
Solution Approach 2:
The invention inverts the conventional approach by using a second stage that operates in excess H2S mode (opposite to the first stage's excess SO2 mode) to remove the harmful SO2 byproduct. This inversion transforms the harmful SO2 generated in stage one into a reactant for stage two, where it is converted to elemental sulfur.
2Manufacturing precision
If additional sulfur removal technologies are added to meet stringent SO2 emission targets, then SO2 removal capability is improved, but capital and operating costs increase
Solution Approach 1:
The UCSRP reactor technology serves multiple functions: it removes H2S in the first stage and removes SO2 in the second stage. By making the same reactor technology multi-functional through operational mode switching, the invention avoids the need for entirely different sulfur removal technologies, thereby reducing device complexity while achieving stringent SO2 removal capabilities.
Solution Approach 2:
The invention changes operational parameters (specifically the excess reactant mode) of the UCSRP reactor to achieve different removal functions. By switching between excess SO2 mode and excess H2S mode, the same reactor system can perform H2S removal or SO2 removal, eliminating the need for additional specialized equipment and reducing overall system complexity.
3Manufacturing precision
If UCSRP process operates in excess SO2 mode for H2S-laden streams with high CO2 levels, then H2S removal is improved, but solvent recirculation rates and operating costs increase
Solution Approach 1:
The solvent recirculation burden is segmented between two stages with different operational modes. The first stage handles the bulk H2S removal with moderate recirculation, while the second stage operates with lower recirculation requirements to remove SO2. This segmentation optimizes the overall energy consumption compared to single-stage operation with high recirculation demands.
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 achieves sulfur levels below 50 ppbv in product gas streams at lower costs compared to existing methods, enabling compliance with stringent emission targets and optimizing CO2 utilization for additional power or chemical production, while reducing the need for costly guard-beds and additional reactor vessels.
Implementation Method 1
The UCSRP reactor vessels, which contain a suitable packing material, may be operated either in a co-current down-flow mode or a counter-current mode... a gaseous stream containing H2S... is provided to a first stage UCSRP reactor vessel operating in an excess SO2 mode... The effluent gas from the first stage UCSRP reactor vessel is provided to a second stage UCSRP reactor vessel, which vessel is operating in an excess H2S mode
Implementation Method 2
The off-gases from the stripper are sent to a sulfur recovery unit, most often a Claus plant... The gas is then cooled, resulting in separation of up to about 70% of the sulfur in the feed as liquid elemental sulfur in the liquid phase
Implementation Method 3
The gas is reheated and passed over a catalyst at 600° F. or thereabouts, resulting in the formation of additional elemental sulfur
Data Source
AI summary
A multi-stage UCSRP process and system for removal of sulfur from a gaseous stream in which the gaseous stream, which contains a first amount of H2S, is provided to a first stage UCSRP reactor vessel operating in an excess SO2 mode at a first amount of SO2, producing an effluent gas having a reduced amount of SO2, and in which the effluent gas is provided to a second stage UCSRP reactor vessel operating in an excess H2S mode, producing a product gas having an amount of H2S less than said first amount of H2S.