Phototrophic H2S Purification via Iron Chelate Mediator
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Solution Overview
Problem
Current methods for removing hydrogen sulfide from hydrocarbon streams are energy-inefficient and costly, particularly in smaller scale operations, and do not effectively address carbon dioxide emissions in refinery and gas production processes.
Innovation Solution
The use of genetically modified green sulfur bacteria in conjunction with an anaerobic metal redox reaction to oxidize hydrogen sulfide to elemental sulfur, while also fixing carbon or nitrogen, reducing the need for costly metal chelators and energy-intensive processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phototrophic bacteria are used to oxidize H2S at high light intensities, then productivity increases, but energy efficiency decreases due to light saturation and waste as heat or fluorescence
Solution Approach 1:
An iron chelate is introduced as an intermediary substance that mediates between light energy and H2S oxidation. The iron chelate absorbs light energy and transfers it to drive H2S oxidation, acting as a mediator that decouples direct bacterial light absorption from the oxidation process, thereby improving overall energy efficiency
Solution Approach 2:
The natural photosynthetic mechanism of phototrophic bacteria is replaced with a photochemical system using iron chelate. Instead of relying on bacterial photosynthesis which suffers from light saturation, the system uses iron chelate photochemistry that can operate more efficiently across a broader light intensity range, substituting a biological mechanism with a chemical one
2Ease of manufacture
If traditional Claus process is implemented for H2S removal, then sulfur recovery is achieved, but capital cost increases making it impractical for smaller scale operations
Solution Approach 1:
The system uses inexpensive, readily available iron chelates that can be easily replenished, replacing the need for expensive, complex Claus plant infrastructure. The iron chelate acts as a consumable reagent that is cheap and can be continuously supplied, making the process economically viable for small-scale operations
Solution Approach 2:
The core sulfur recovery function is extracted from the complex Claus process infrastructure and implemented through a simplified system using iron chelate and phototrophic bacteria. This extracts the essential chemical transformation while eliminating the need for large-scale equipment, making the process suitable for smaller operations
3Productivity
If redox processes with transition metals are used for H2S oxidation, then sulfur is produced, but metal chelators decompose over time requiring constant replenishment
Solution Approach 1:
The system is designed to continuously replenish iron chelate at a controlled rate, discarding decomposed chelate and recovering/adding fresh chelate to maintain the reaction. This continuous replacement strategy ensures steady-state operation despite chelator decomposition, maintaining productivity while using inexpensive replacement material
4Productivity
If aerobic bacteria like Thiobacillus are used to treat H2S, then large quantities of H2S can be treated, but sulfate formation increases requiring energy-intensive removal
Solution Approach 1:
The oxidation process is changed from aerobic biological oxidation (producing sulfate) to photochemical oxidation using iron chelate (producing elemental sulfur). By changing the chemical parameters of the oxidation process - using photochemical instead of biochemical pathways - the product distribution is altered to favor elemental sulfur over sulfate, eliminating the need for energy-intensive sulfate removal
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 provides a cost-effective and energy-efficient method for hydrogen sulfide removal and carbon fixation, suitable for use in locations where traditional Claus plants are impractical, producing elemental sulfur and organic compounds while reducing greenhouse gas emissions.
Implementation Method 1
introducing the reduced metal chelate to a photobioreactor comprising a phototrophic bacterium
Implementation Method 2
The use of genetically modified green sulfur bacteria in conjunction with an anaerobic metal redox reaction to oxidize hydrogen sulfide to elemental sulfur
Data Source
AI summary
The present disclosure relates to processes for desulfurizing hydrocarbon feedstocks. The processes may include introducing a feedstock comprising hydrogen sulfide to an absorber comprising a metal chelate to form a reduced metal chelate. The processes may further include introducing the reduced metal chelate to a photobioreactor comprising a phototrophic bacterium. The present disclosure also relates to apparatuses for desulfurizing hydrocarbon feedstock. An apparatus may include and absorber and a photobioreactor fluidly connected to the absorber. The photobioreactor may be an anaerobic vessel with a light source.