Sulfur Degassing via Nitrogen Sweep for H2S Recovery
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Solution Overview
Problem
Existing methods for treating sulfur-containing vent gases from liquid sulfur storage and handling face challenges such as H2S release, toxicity, explosive mixtures, high capital and operating expenses, combustion air control issues, corrosion, and SO2 emissions, particularly when degassing large volumes or routing vent gases to remote locations.
Innovation Solution
The method involves recycling all acid gas-containing streams back to the sulfur recovery unit and tail gas treating unit, degassing liquid sulfur to very low H2S levels, and routing acid gas-containing streams to the main reaction furnace or tail gas unit under pressure, using a sweep gas with minimal oxygen to avoid poisoning hydrogenation catalysts and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If vent gases from un-degassed sulfur loading are routed to an incinerator, then H2S release is prevented, but SO2 emissions increase
Solution Approach 1:
The patent converts the harmful H2S vent gases into a useful resource by routing them to the SRU where they are converted to elemental sulfur through the Claus process. The sulfur-containing gases that would otherwise be waste are transformed into a valuable product, eliminating both H2S release and SO2 emissions while producing additional sulfur
Solution Approach 2:
The patent recovers sulfur from the vent gases by routing them to the SRU for processing. Instead of discarding the sulfur-containing gases through incineration, the system captures and recovers the sulfur, converting it back to elemental form that can be reused or sold
2Object-affected harmful factors
If large volumes of vent gases are routed to SRU main burner via long runs of jacketed piping, then H2S release is prevented, but combustion air control problems and insufficient furnace temperature occur
Solution Approach 1:
The patent segments the sulfur handling system into distinct functional zones: in-pit degassing occurs in the rundown pit area, while out-of-pit degassing occurs in separate vessels. This segmentation allows vent gases to be processed closer to their source, reducing the need for long piping runs and improving combustion air control at the SRU
Solution Approach 2:
The patent applies preliminary degassing action by implementing both in-pit and out-of-pit degassing before the sulfur is loaded or stored. This preliminary removal of H2S reduces the volume and concentration of gases that need to be handled by the SRU, preventing combustion air control problems
3Object-affected harmful factors
If sulfur rundown pits are swept with air, then H2S release is prevented, but oxygen in the vent gas poisons the hydrogenation catalyst
Solution Approach 1:
The patent uses an inert atmosphere by replacing air (which contains oxygen) with nitrogen gas for sweeping the rundown pit. Nitrogen is inert and will not poison the hydrogenation catalyst, while still effectively displacing and removing H2S from the pit atmosphere
Solution Approach 2:
The patent introduces nitrogen as an intermediary gas that mediates between the need to remove H2S and the need to protect the catalyst. Nitrogen serves as a carrier gas that transports H2S to the SRU without introducing oxygen that would harm the catalyst
4Manufacturing precision
If liquid sulfur is degassed in separate and serially arranged compartments with oxygen-containing gas, then residual sulfide/polysulfide concentration is reduced, but significant material and complexity are required
Solution Approach 1:
The patent merges the degassing function with the existing sulfur handling infrastructure by implementing degassing in the rundown pit itself and in the sulfur loading area. This eliminates the need for separate, serially arranged degassing compartments while achieving the same level of sulfide removal through the use of nitrogen sparging and vapor recovery
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 eliminates sulfur emissions, reduces the risk of explosions and odor nuisances, simplifies equipment needs, and avoids SO2 emissions by recycling all sulfur-containing gases, ensuring safe and efficient handling and processing with near-zero emissions.
Implementation Method 1
a purge gas is used at a second pressure in a degassing unit to degas the liquid sulfur, thereby forming a degassed liquid sulfur product and an acid gas-containing purge gas
Implementation Method 2
a stream of finely divided oxygen-containing gas is combined under agitation with the liquid sulfur to reduce residual sulfide/polysulfide concentration
Implementation Method 3
routing acid gas-containing streams to the main reaction furnace or tail gas unit under pressure
Data Source
AI summary
Sulfur emissions from liquid sulfur are reduced, or even entirely avoided by degassing the liquid sulfur at pressure in an out-of-pit vessel and by sweeping the rundown pit (or vessel) with a sweep gas that is non-poisonous for a hydrogenation catalyst. Acid gases from degassing are fed at pressure to the Claus unit, while sweep gases are fed to the tail gas treatment unit to substantially recycle the acid gases to extinction. In preferred plants and methods, motive fluids and booster eductors or compressors are not needed, and incineration of the acid gases can be avoided.