CO2 Purification via Selective H2S Absorption
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Solution Overview
Problem
Current methods for recovering high-quality native CO2 from hydrocarbon feed streams containing CO2 and H2S contaminants result in CO2 streams that are not pure enough for enhanced oil recovery (EOR) due to residual H2S levels, requiring large and costly equipment for purification.
Innovation Solution
A process involving the separation of hydrocarbon feed gas into sweetened and acid gas streams, followed by a Claus unit to convert H2S into elemental sulfur, and subsequent treatment in a Tail Gas Treatment Unit (TGTU) with a non-selective acid gas absorption unit and selective H2S absorption unit to achieve high purity CO2, using a combination of chemical and physical solvent treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If amine-based CO2 capture unit is used to recover purified CO2 from nitrogen-diluted stream, then CO2 purification is achieved, but equipment size and operational costs increase significantly
Solution Approach 1:
The invention performs preliminary separation of CO2 from the nitrogen-diluted stream using a CO2-selective membrane before the amine-based capture unit. This pre-concentration step reduces the volume of gas requiring amine treatment, thereby缩小ing the equipment size while maintaining high purification quality. The membrane separator is positioned upstream to prepare the feed stream for the subsequent amine unit.
Solution Approach 2:
The CO2 capture process is divided into two independent stages: (1) physical separation using CO2-selective membrane to concentrate CO2 and remove most nitrogen, and (2) chemical absorption using amine-based unit to achieve final purification. This segmentation allows each unit to be optimized for its specific function, reducing the burden on the amine unit and decreasing its required size.
2Reliability
If CO2 is diluted by large amount of nitrogen from combustive agent, then Claus combustion is maintained, but CO2 recovery efficiency and purification quality decrease
Solution Approach 1:
A CO2-selective membrane serves as an intermediary device between the nitrogen-diluted CO2 stream and the amine-based capture unit. The membrane selectively transports CO2 while rejecting nitrogen, acting as a mediator that decouples the combustion requirement (maintaining nitrogen in the Claus unit) from the purification requirement (removing nitrogen before CO2 capture). This intermediary enables both objectives to be achieved simultaneously.
Solution Approach 2:
The invention extracts CO2 from the nitrogen-diluted stream using a CO2-selective membrane before the stream enters the amine-based capture unit. This extraction step removes the harmful dilution effect of nitrogen, allowing the subsequent purification unit to operate on a concentrated CO2 stream rather than a diluted mixture, thereby improving purification quality.
3Manufacturing precision
If incinerator is connected at outlet of amine-based CO2 capture unit, then remaining contaminants are destroyed, but hydrogen and carbon monoxide are lost
Solution Approach 1:
The CO2-selective membrane performs preliminary purification by removing nitrogen and other non-CO2 components before the gas stream reaches the amine-based capture unit and incinerator. This pre-cleaning action reduces the burden on the incinerator, allowing it to operate at lower temperatures and shorter residence times, thereby minimizing the oxidation and loss of valuable hydrogen and carbon monoxide while still achieving the required CO2 purity.
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 reduces H2S levels in the CO2 stream to meet EOR specifications, achieving a high-quality purified CO2 stream with reduced equipment size and operational costs.
Implementation Method 1
a non-selective acid gas absorption unit containing a non-selective amine-based solvent, wherein a hydrogenated tail gas stream is absorbed into said non-selective amine-based solvent
Implementation Method 2
a selective H2S-absorption unit containing a selective H2S-absorption solvent, wherein the enriched gas stream is absorbed into said selective H2S-absorption solvent
Implementation Method 3
a Claus unit, wherein all of the acid gas stream is converted into a liquid stream of elemental sulfur and a tail gas stream
Implementation Method 4
a quench contactor, wherein the hydrogenated tail gas stream is cooled down and water is removed therefrom
Data Source
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AI summary
The invention concerns a method for treating a hydrocarbon feed gas stream containing at least CO2 and H2S to recover a high quality purified CO2 gas stream, comprising the following steps: a. Separating said hydrocarbon feed gas stream into (i) a sweetened hydrocarbon gas stream, and (ii) an acid gas stream comprising at least CO2 and H2S; b. Introducing said gas stream (ii) into a Claus unit, thereby recovering (iii) a liquid stream of elemental sulfur and (iv) a tail gas mainly comprising N2, CO2, SO2 and H2S; c. Introducing the tail gas (iv) into a hydrogenation reactor and then into a quench contactor of the Tail Gas Treatment Unit (TGTU) thereby recovering (v) a hydrogenated tail gas stream mainly comprising N2, H2, CO, CO2 and H2S; d. Contacting said tail gas stream (v) with a non-selective amine-based solvent into a non-selective acid gas absorption unit of the TGTU thereby recovering (vi) an off gas mainly comprising N2, H2 and CO and (vii) a gas stream enriched in CO2 and H2S; e. Sending the off gas (vi) to an incinerator; f. Contacting said enriched gas stream (vii) with a selective H2S-absorption solvent into a selective H2S-absorption unit thereby recovering (viii) a highly purified CO2 gas stream and (ix) a H2S-enriched gas stream, as well as the device for carrying said method.