NF3 Recovery in TSA Adsorption Cycles
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Solution Overview
Problem
Conventional NF3 manufacturing methods result in significant emissions of NF3 to the atmosphere due to the venting of co-adsorbed gas during the regeneration step in temperature swing adsorption (TSA) cycles, leading to a low yield and adsorber degradation.
Innovation Solution
A novel TSA cycle that includes a recovery step to selectively desorb and recover 10-100% of co-adsorbed NF3 using an inert purge gas, either co-current or counter-current, before the regeneration step, thereby minimizing atmospheric emissions and extending adsorber life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TSA process vents co-adsorbed NF3 during regeneration, then impurities are removed from the gas stream, but NF3 is lost to atmosphere and yield decreases
Solution Approach 1:
The regeneration process is segmented into two distinct steps: a depressurization step that recovers NF3 by desorbing it from the adsorbent, and a subsequent heating step that removes impurities. This segmentation allows NF3 recovery before impurity removal, preventing NF3 loss to atmosphere while maintaining purification effectiveness.
Solution Approach 2:
The NF3 recovery step is performed as a preliminary action before the main impurity removal step. By depressurizing the adsorber first and collecting the desorbed NF3, the process prepares and recovers the valuable NF3 before proceeding to heat the adsorbent for impurity removal, thus preventing NF3 emissions.
2Reliability
If adsorber capacity for impurities is maximized, then purification efficiency improves, but co-adsorbed NF3 loss per cycle remains equivalent
Solution Approach 1:
The process segments the desorption of NF3 from the desorption of impurities by using a depressurization step first. This allows the adsorber to be optimized for impurity capacity while a separate recovery step captures NF3 before the heating step removes impurities, thereby maintaining both purification efficiency and NF3 yield.
3Duration of action of stationary object
If NF3 is vented during regeneration, then adsorber is regenerated quickly, but adsorber degradation occurs and environmental harm increases
Solution Approach 1:
The depressurization and NF3 recovery step is performed as a preliminary action before the heating step. This preliminary depressurization removes NF3 without requiring high temperatures, and the subsequent heating step for impurity removal can be optimized to avoid adsorber degradation. The preliminary recovery also prevents harmful atmospheric emissions.
4Object-affected harmful factors
If NF3 manufacturing reduces atmospheric emissions, then environmental impact decreases, but process complexity increases
Solution Approach 1:
The regeneration process is segmented into two steps: depressurization for NF3 recovery and heating for impurity removal. While this adds a step to the process, it enables NF3 recovery and emission reduction using standard equipment operations rather than requiring entirely new complex systems.
Solution Approach 2:
The depressurization step utilizes the pressure differential already present in the TSA cycle to drive NF3 desorption and recovery, requiring minimal additional energy input or complex equipment. The process leverages existing operational parameters to achieve emission reduction.
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 novel TSA cycle increases the overall process yield of NF3 by recovering a significant portion of co-adsorbed gas, reducing emissions, and preventing adsorber degradation by controlled NF3 removal during regeneration.
Implementation Method 1
flowing the crude NF3 gas stream through the first adsorber in the first vessel to selectively adsorb the at least one impurity
Implementation Method 2
flowing a recovery purge gas through the first adsorber to selectively desorb co-adsorbed NF3 from the first adsorber
Data Source
AI summary
During the conventional temperature swing adsorption (TSA) process, NF3 co-adsorbed with the impurities is vented during regeneration. This invention is a novel TSA cycle in which the co-adsorbed NF3 is recovered. In this novel TSA cycle, a control scheme is used to stop the adsorption prior to the saturation of the adsorber with impurities and use a recovery purge gas (either co-current or counter-current) to release the co-adsorbed NF3 off the saturated adsorber. The effluent of the inert purge gas can be combined with the effluent of the on-stream vessel or can be recycled to the feed of the on-stream vessel. 10%-100% of the co-adsorbed NF3 is recovered and made available as product in this novel TSA cycle. Thus the overall process yield of NF3 is increased. The removing of the co-adsorbed NF3 from the adsorber also prevents adsorber degradation thus prolonging the useful life of the adsorber.