Reducing refrigeration and dehydration load for a feed stream entering a cryogenic distillation process
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Solution Overview
Problem
Current cryogenic distillation processes for natural gas face challenges in efficiently dehydrating and cooling sour gas feed streams, leading to high refrigeration and dehydration loads, which increase costs and risk of solid precipitate formation.
Innovation Solution
A sequential cooling and progressive conditioning system that separates the sour gas feed stream into water and partially dehydrated streams, followed by staged cooling to reduce the refrigeration load and prevent hydrate formation, incorporating a dehydration unit and multiple cooling stages to optimize the feed stream's temperature and moisture content before entering the cryogenic distillation column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional single-stage cooling and dehydration is used for sour gas feed streams, then the process is simpler, but the refrigeration load is excessively high and hydrate formation risk increases
Solution Approach 1:
The cooling and dehydration process is divided into multiple stages with intermediate separation points. The first cooling stage condenses acid gas and water, which are separated and removed. The second cooling stage further cools the partially dehydrated stream. This segmentation reduces the refrigeration load on each stage compared to single-stage cooling of the entire stream.
Solution Approach 2:
The first cooling and dehydration stage performs preliminary removal of water and acid gas before the second cooling stage. By removing a significant portion of water and contaminants in the first stage, the second stage operates on a reduced load, minimizing overall refrigeration requirements and preventing hydrate formation.
2Reliability
If more aggressive dehydration is applied to the feed stream, then hydrate formation is prevented, but the dehydration load and associated costs increase
Solution Approach 1:
Dehydration is performed in two separate stages with intermediate cooling. The first dehydration stage removes the bulk of water and acid gas condensation products. The second dehydration stage provides additional drying. This segmented approach achieves reliable hydrate prevention while distributing the dehydration load across multiple simpler units rather than requiring one complex high-capacity dehydrator.
3Use of energy by stationary object
If higher cooling temperatures are used, then refrigeration costs are reduced, but liquid generation increases and hydrate formation risk increases
Solution Approach 1:
The cooling process is divided into two stages with intermediate separation. The first stage operates at a temperature that condenses acid gas and water, removing them as liquids. The second stage cools the partially dehydrated stream to a lower temperature. This segmentation allows liquid removal at each stage, preventing excessive liquid accumulation while managing refrigeration costs.
Solution Approach 2:
The condensation of acid gas and water in the first cooling stage, which initially appears as a harmful effect (liquid generation), is actually beneficial. These condensed liquids are separated and removed, preventing them from causing hydrate formation downstream. The harmful liquid generation is converted into a useful dehydration mechanism.
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 reduces the refrigeration load, decreases the amount of liquid generated, and minimizes the risk of hydrate formation, resulting in lower operating and capital costs while maintaining efficient separation of hydrocarbons from contaminants.
Implementation Method 1
a dehydration unit configured to separate the sour gas feed stream into a first stream comprising water and a partially dehydrated feed stream
Implementation Method 2
a first cooling stage configured to condense a first stream comprising acid gas from the partially dehydrated feed stream into a partially cooled feed stream and a first cooling stage liquid stream comprising acid gas
Implementation Method 3
a second cooling stage configured to condense a second stream comprising acid gas from the partially cooled feed stream into a cooled feed stream and a second cooling stage liquid stream comprising acid gas
Implementation Method 4
sequential cooling to reduce the refrigeration load and prevent hydrate formation
Data Source
AI summary
A system for conditioning a sour gas feed stream for a cryogenic distillation tower. A dehydration unit separates the sour gas feed stream into a first stream including water and a feed stream. A sequential cooling assembly is coupled to both the dehydration unit and the cryogenic distillation tower. The sequential cooling assembly includes: a first stage that separates the feed stream into a partially cooled feed stream and a second stream including acid gas; a second stage that cools the partially cooled feed stream into a cooled feed stream and a third stream including acid gas; and a cooled feed stream header coupled to a cryogenic distillation tower feed inlet. The first stage, the second stage, or both send at least one of the second and third streams to a bottom section of the cryogenic distillation tower.