Upstream Caustic Extraction for Low Sulfur Propane and Butane
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Solution Overview
Problem
Hydraulic fracturing processes produce hydrocarbons with sulfur-containing compounds, requiring costly sulfur removal processes, and existing methods necessitate multiple sulfur extraction units, increasing operational expenses and complexity.
Innovation Solution
A method involving a caustic treatment process to convert mercaptans into disulfides, allowing for the separation of sulfur-free propane and butane streams through fractionation, reducing the need for multiple sulfur removal units by integrating sulfur extraction upstream of the fractionation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple sulfur removal units are used to remove sulfur from propane and butane streams, then sulfur removal effectiveness is improved, but device complexity and operational costs increase
Solution Approach 1:
The patent applies preliminary action by performing sulfur removal upstream of the fractionation process rather than downstream. The caustic extraction unit removes mercaptans from the C1-5+ feed stream before it is fractionated into propane, butane, and other hydrocarbons. This preliminary sulfur removal prevents sulfur from being distributed to multiple product streams, eliminating the need for multiple downstream sulfur removal units and thereby reducing device complexity while maintaining effective sulfur removal.
2Manufacturing precision
If sulfur removal processes are implemented after fractionation, then product separation is improved, but operational costs and equipment investment increase
Solution Approach 1:
The patent implements preliminary sulfur removal before the fractionation process. The caustic extraction unit is positioned upstream to remove mercaptans from the feed stream before it enters the fractionation column. This timing allows sulfur removal to occur once on the bulk stream rather than requiring separate sulfur removal units for each fractionated product stream, thereby reducing both capital expense and operating costs while maintaining product separation quality.
Solution Approach 2:
The patent segments the sulfur removal function from the fractionation function. Instead of integrating sulfur removal into each fractionation step or requiring post-fractionation sulfur removal for each product stream, the invention uses a dedicated caustic extraction unit that handles sulfur removal separately and upstream. This segmentation allows each process unit to be optimized for its specific function and reduces the total number of units required.
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 effectively reduces sulfur content in propane and butane streams, minimizing the number of sulfur extraction units required and lowering operational costs by concentrating sulfur removal in a single upstream unit, resulting in sulfur-free hydrocarbon products.
Implementation Method 1
reacting a mercaptan in a washed feed stream with a caustic stream to produce a mercaptan salt
Implementation Method 2
The mercaptan salt in the rich caustic stream is reacted with oxygen and water to produce a mixed caustic/disulfide stream
Implementation Method 3
feeding a washed feed stream into an extraction unit to produce a hydrocarbon treated stream and a rich caustic stream
Implementation Method 4
The hydrocarbon treated stream is fractionated to produce a propane stream, a butane stream, and a C5+ stream
Data Source
AI summary
Methods and apparatuses are provided for producing low sulfur propane and butane. The method includes reacting a mercaptan in a washed feed stream with a caustic stream to produce a mercaptan salt in a rich caustic stream and a hydrocarbon treated stream. The mercaptan salt in the rich caustic stream is reacted with oxygen and water to produce a mixed caustic/disulfide stream, and the caustic and disulfides in the mixed caustic/disulfide stream are separated to produce a disulfide stream and the caustic stream. The hydrocarbon treated stream is fractionated to produce a propane stream, a butane stream, and a C5+ stream.