Hydrogen Purification by Chilling and Adsorption in MCH Dehydrogenation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hydrogen production processes face challenges in achieving high purity and recovering trace amounts of toluene while maintaining the Wobbe Index for hydrogen product streams, which are essential for fuel cell and power generation applications, due to the high cost of hydrogen produced by LOHC and the need to recover lost toluene and reduce aromatics.
Innovation Solution
A process involving chilling compressed gas from the net gas section to specific temperatures using a vapor economizer and chiller, combined with an adsorption step in a PSA or TSA unit, to recover toluene and remove aromatics, while maintaining the desired Wobbe Index range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the hydrogen product stream is produced through dehydrogenation of MCH, then hydrogen is obtained, but the hydrogen purity is insufficient and contains trace amounts of toluene and aromatics that must be removed
Solution Approach 1:
The patent applies parameter changes by controlling the temperature of the chiller unit to condense toluene from the hydrogen product stream. By adjusting the temperature parameter within a specific range, the system achieves both high hydrogen purity and toluene recovery, resolving the contradiction between purity improvement and substance loss.
Solution Approach 2:
The patent utilizes phase transitions by condensing toluene vapor to liquid phase through cooling in the chiller unit. This phase change enables separation of toluene from hydrogen gas, simultaneously achieving hydrogen purification and toluene recovery, thus resolving the technical contradiction.
2Loss of substance
If trace amounts of toluene are recovered from the hydrogen product stream, then toluene loss is reduced, but the Wobbe Index of the hydrogen product stream may be affected
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chiller temperature to condense toluene while maintaining hydrogen in gaseous state. This parameter optimization ensures both toluene recovery and preservation of hydrogen's Wobbe Index within the required range of 44-49 MJ/m³, resolving the contradiction between substance recovery and reliability.
3Loss of substance
If the hydrogen product stream is chilled to recover toluene, then toluene is recovered, but energy is consumed in the chilling process
Solution Approach 1:
The patent applies self-service by using the cold chiller unit to simultaneously achieve two objectives: recovering toluene from the hydrogen stream and maintaining the hydrogen temperature within the Wobbe Index specification range. This dual-function approach reduces overall energy consumption by combining cooling purposes, resolving the contradiction between substance recovery and energy use.
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 increases hydrogen purity to at least 99.7 mol% and limits aromatics to less than 1 wtppm of BTX, recovering about 1 wt% toluene and maintaining the Wobbe Index between 44 to 49 MJ/m3, thereby reducing operational costs and meeting stringent purity requirements.
Implementation Method 1
by chilling the compressed gas from the net gas section to about −27° C. to about 17° C.
Implementation Method 2
an adsorption step in a PSA or TSA unit, to recover toluene and remove aromatics
Data Source
AI summary
Present disclosure relates to process for increasing the purity and recovery of hydrogen product stream obtained from a dehydrogenation process. The dehydrogenated effluent stream is separated to obtain the net gas stream. The net gas stream is compressed in a hydrogen compressor section. Even after compressing the net gas, traces of toluene are still present in the gas phase. Applicants have found to recover these toluene traces, the compressed gas from the hydrogen compressor section is chilled in a vapor economizer followed by a chiller to produce a chilled stream at a temperature of from about −27° C. to about 17° C. This process also helps maintain the Wobbe Index of the hydrogen product stream in the range of about 44 to about 49 MJ/m3. In another embodiment, the compressed net gas stream from the hydrogen compressor section is adsorbed in an adsorption unit to separate hydrogen product stream from the recycle gas stream, wherein the recycle gas stream is completely recycled to the hydrogen compressor.