Rapid-Cycle Adsorbent Bed Dehydration for Cryogenic Gas Processing
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Solution Overview
Problem
Conventional molecular sieve TSA and PSA processes for natural gas dehydration require high temperatures, large adsorbent volumes, and fired heaters, leading to increased costs, footprint, and hydrothermal degradation of adsorbent materials.
Innovation Solution
The implementation of a rapid cycle temperature swing adsorption (RCTSA) process that utilizes a purge stream from a demethanizer overhead stream at moderate temperatures and pressures, eliminating the need for fired heaters and reducing adsorbent quantity, with larger purge gas volumes and lower temperature regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional molecular sieve TSA process is used for natural gas dehydration, then dehydration efficiency is improved, but capital cost and footprint increase due to large adsorbent volumes and fired heaters
Solution Approach 1:
The patent changes the operating parameters from conventional TSA (high temperature, low pressure) to RCTSA (moderate temperature, high pressure with pressure swing). By operating at elevated pressures (e.g., 50-200 bar) and using moderate temperature regeneration (e.g., 50-150°C), the adsorbent loading capacity increases significantly, allowing the same dehydration capacity to be achieved with much smaller adsorbent volumes and equipment footprint.
Solution Approach 2:
The patent eliminates fired heaters by using the natural gas product stream itself (or a portion of it) as the heating medium for regeneration. The product gas is cooled to provide heat for regenerating the adsorbent, and then reheated before being returned to the process. This self-service approach removes the need for external fired heaters and associated infrastructure, reducing footprint and capital cost.
2Manufacturing precision
If conventional molecular sieve TSA process is used for natural gas dehydration, then dehydration efficiency is improved, but operational cost increases due to fired heater fuel consumption
Solution Approach 1:
The system uses the natural gas product stream as its own heating medium for regeneration. The product gas is cooled in a heat exchanger to condense water and provide thermal energy, then this cooled gas (or a portion of it) is used to heat the adsorbent during regeneration. After transferring heat, the gas is reheated and returned to the process. This eliminates the need for external fired heaters and associated fuel consumption.
Solution Approach 2:
The patent converts the cooling requirement (which would normally be a separate energy input) into a beneficial heat source for regeneration. By cooling the product gas to condense water and then using this cooled gas as the regeneration medium, the system transforms what would be a energy-consuming step into an energy-providing step, eliminating fired heater fuel consumption.
3Reliability
If high temperature regeneration is used in conventional TSA, then adsorbent regeneration is improved, but hydrothermal degradation of adsorbent materials occurs
Solution Approach 1:
The patent changes the regeneration temperature from conventional high temperatures (e.g., 200-500°C) to moderate temperatures (e.g., 50-150°C). By operating at elevated pressures during adsorption, the adsorbent achieves higher loading capacities, so less thermal energy is required for regeneration. This lower temperature regime eliminates hydrothermal degradation while maintaining effective regeneration through the pressure swing mechanism.
Solution Approach 2:
The patent utilizes the porous structure of molecular sieve adsorbents more effectively by operating at elevated pressures. The high pressure increases the driving force for adsorption into the pores, achieving higher loading capacities. During regeneration, the pressure reduction (vacuum or depressurization) efficiently removes adsorbed water from the pores at low temperatures, avoiding thermal degradation while maintaining regeneration effectiveness.
4Device complexity
If conventional PSA process is used for dehydration, then process simplicity is improved, but water removal capacity is insufficient for cryogenic processing requirements
Solution Approach 1:
The patent combines pressure swing with temperature swing to create RCTSA. The system operates at elevated pressures (50-200 bar) during adsorption to maximize water uptake capacity, then uses moderate temperature heating (50-150°C) combined with pressure reduction for regeneration. This dual-parameter approach achieves water removal capacities sufficient for cryogenic processing (typically requiring <1 ppm water) while maintaining relative process simplicity through integrated heat and mass transfer.
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 achieves efficient dehydration with reduced capital and operational costs, smaller footprint, and minimized hydrothermal degradation, while maintaining low water content in the product stream, suitable for cryogenic processing.
Implementation Method 1
passing a gaseous feed stream through an adsorbent bed unit to remove water and other contaminants from the gaseous feed stream
Implementation Method 2
passing a purge stream through the adsorbent bed unit in a counter flow direction to form a purge product stream
Data Source
AI summary
Provided are apparatus and systems for performing a swing adsorption process. This swing adsorption process may involve passing streams through adsorbent bed units to remove contaminants, such as water, from the stream. As part of the process, the adsorbent bed unit is purged with a purge stream that is provided from the overhead of the demethanizer. The configuration integrates a RCTSA dehydration system with a cryogenic recovery system.