High Pressure Acid Gas Processing with Zero Emissions
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Solution Overview
Problem
The gas processing industry faces challenges in treating natural gas with high acid gas content from unconventional sources like shale gas, as existing methods are uneconomical for high pressure sour/acid gases due to high energy consumption and environmental concerns, and fail to meet stringent emission and energy efficiency requirements.
Innovation Solution
A process involving an absorption unit using a lean physical solvent to remove CO2 and H2S, followed by an amine absorber to further purify the gas, with integrated regeneration units to recycle solvents and amines, and optional redox units for sulfur production, allowing for efficient treatment of high CO2 and H2S content gases without external heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chemical solvent processes are used to remove acid gases, then acid gas removal efficiency is improved, but energy consumption increases proportionally with partial pressure of acid gases
Solution Approach 1:
The process segments acid gas removal into two distinct stages: first using a physical solvent to remove the bulk of CO2 at high pressure, then using a chemical solvent (amine) to remove residual H2S and CO2. This segmentation allows each solvent to operate in its optimal efficiency range, reducing overall energy consumption compared to using chemical solvent alone for the entire removal process.
Solution Approach 2:
The process changes the operating parameters by maintaining high pressure (300-1000 psig) throughout the absorption process and using flash regeneration instead of thermal regeneration for the physical solvent. This parameter change allows the physical solvent to achieve high removal efficiency without the energy-intensive heating required by conventional chemical solvent processes.
2Adaptability or versatility
If physical solvent absorption is used for high acid gas fields, then accommodation of CO2 content variations is improved, but H2S removal capability deteriorates when H2S content is high
Solution Approach 1:
The process segments the removal function: the physical solvent handles CO2 removal and adapts to CO2 content variations, while the chemical solvent (amine) specifically targets H2S removal. This segmentation allows the system to maintain high adaptability to CO2 variations while achieving precise H2S removal that physical solvents alone cannot provide.
Solution Approach 2:
The physical solvent acts as an intermediary that removes the bulk CO2 and prepares the gas stream for subsequent H2S removal by the amine. This intermediary step allows the amine to focus on H2S removal without being overwhelmed by high CO2 concentrations, improving overall H2S removal capability.
3Measurement precision
If sulfur scavenger beds are used to improve treated gas quality, then H2S limits are met, but environmental acceptance deteriorates due to spent bed disposal
Solution Approach 1:
The process converts the harmful H2S that would otherwise require solid scavenger beds into a beneficial concentrated H2S stream through the amine absorption and flash regeneration process. This H2S-rich stream can be directly fed to sulfur recovery units (Claus process) for valuable sulfur production, eliminating the need for spent bed disposal and creating a beneficial byproduct.
Solution Approach 2:
The process replaces the mechanical/scavenger bed system with a chemical absorption and flash regeneration system. Instead of using solid sulfur scavenger beds that require disposal, the system uses amine chemical absorption followed by pressure reduction to release concentrated H2S, which can be continuously processed and converted to valuable sulfur products.
4Measurement precision
If low-boiling organic physical solvents are used, then absorption is enhanced, but electric power consumption increases due to refrigeration requirements
Solution Approach 1:
The process changes the temperature parameter by operating at ambient or mildly refrigerated temperatures (0°F or lower, but not cryogenic) using solvents like propylene carbonate, NMP, or SELEXOL. This parameter change maintains sufficient absorption enhancement while dramatically reducing the electric power consumption associated with cryogenic refrigeration, making the process economically viable.
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 process reduces H2S and CO2 levels in the pipeline gas to meet stringent specifications, recycles solvents and amines, and captures CO2 for sequestration or EOR, while reducing energy consumption and environmental impact.
Implementation Method 1
an absorption unit configured to (i) receive a feed gas comprising H2S and CO2 and (ii) use a lean physical solvent to absorb a portion of H2S and CO2 within the feed gas
Implementation Method 2
an amine absorber coupled to the absorption unit and configured to (i) receive the treated gas from the absorption unit and (ii) use a first portion of a lean amine to absorb a portion of H2S and CO2 within the treated gas
Implementation Method 3
solvent regeneration can be accomplished, by flash regeneration that eliminates the need for heating and so reduces greenhouse gas emissions
Data Source
AI summary
Plants, processes, and methods for reducing the H2S and CO2 contents of shale gasses from fields that produce shale gasses having varying H2S and CO2 contents are provided. Acid gas enters an absorber and is scrubbed using a lean physical solvent, producing a treated gas and a rich physical solvent. The H2S content of the treated gas is further reduced in an amine absorber, producing a pipeline gas and a semi-lean amine. The pipeline gas contains lower levels of H2S and CO2 than gas produced using a polishing bed. A physical solvent regeneration unit regenerates the lean physical solvent from the rich physical solvent for feeding into the absorption unit. An amine regeneration unit regenerates the lean amine from the semi-lean amine for feeding into the amine absorber. Contemplated plants may further comprise a Claus Unit or a Redox unit for oxidizing H2S to elemental sulfur.