Catalyst Bed Decontamination Using Solvent Mist and Nitrogen
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Solution Overview
Problem
Catalysts in refineries become ineffective due to heavy hydrocarbon deposits and process poisons, necessitating frequent replacement and decontamination, which is hazardous and time-consuming, especially when dealing with packed beds of granular materials like catalysts and adsorbents.
Innovation Solution
A method using a mist of liquid solvent in nitrogen carrier gas at controlled temperature and pressure to decontaminate catalysts, combining decontamination and cooling processes, enhancing contaminant removal and reducing turnaround time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional hot strip or vapor phase cleaning methods are used to remove contaminants, then contaminant removal effectiveness is improved, but decontamination time and turnaround time increase
Solution Approach 1:
The invention changes the physical state parameter of the cleaning solvent from vapor phase to liquid phase, and introduces a water-free carrier gas to enhance mass transfer. This parameter change allows the cleaning process to occur at lower temperatures while maintaining or improving contaminant removal effectiveness, thereby reducing decontamination time
Solution Approach 2:
The invention uses a water-free carrier gas (pneumatic medium) to transport and distribute the liquid cleaning solvent throughout the catalyst bed. This pneumatic delivery system ensures uniform solvent distribution and enhances the removal of light hydrocarbon contaminants, achieving effective decontamination in reduced time
2Manufacturing precision
If elevated temperature is used to aid contaminant removal through stripping and vaporization, then contaminant removal effectiveness is improved, but energy consumption increases
Solution Approach 1:
The invention changes the phase parameter of the cleaning solvent from vapor to liquid, and introduces a water-free carrier gas to enhance mass transfer. This parameter change allows the cleaning process to occur at lower temperatures while maintaining or improving contaminant removal effectiveness, thereby reducing decontamination time
Solution Approach 2:
The invention uses a water-free carrier gas (pneumatic medium) to transport and distribute the liquid cleaning solvent throughout the catalyst bed. This pneumatic delivery system ensures uniform solvent distribution and enhances the removal of light hydrocarbon contaminants, achieving effective decontamination in reduced time
3Loss of time
If reactor cooling is accelerated by injecting cold nitrogen, then cooling time is reduced, but nitrogen consumption increases
Solution Approach 1:
The water-free carrier gas serves multiple functions: it acts as the cooling medium during the cool-down step, and simultaneously serves as the delivery vehicle for the liquid cleaning solvent during the decontamination step. This multi-functionality reduces the total nitrogen required by eliminating redundant cooling nitrogen consumption
Solution Approach 2:
The invention merges the cooling function and the solvent delivery function into a single water-free carrier gas stream. By combining these two previously separate functions, the process reduces overall nitrogen consumption while achieving both rapid cooling and effective decontamination
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
Effectively removes oils and heavy hydrocarbons from catalyst beds, reducing decontamination and cooling times by up to 50% compared to traditional methods, while minimizing solvent and nitrogen usage.
Implementation Method 1
This is particularly effective in solubilizing and removing oils and heavy hydrocarbon deposits
Implementation Method 2
The carrier gas, or steam, is also used to effectively desorb LELs at a similar temperature
Implementation Method 3
heat aids in removal of contaminants through stripping and vaporization
Implementation Method 4
The subsequent cool-down step after decontamination is often accelerated by injecting cold nitrogen (N2) into the reactor
Implementation Method 5
The jet compressor is used to enable partial recirculation of the process stream effluent combined with fresh coolant gas. The temperature of the combined fluid is controlled by raising or lowering the temperature of the fresh coolant gas and manipulating the ratio of the recirculated effluent gas to fresh coolant gas
Data Source
AI summary
Catalyst beds in refinery reactors require periodic change out due to build-up of contamination and loss of activity. The instant invention mists a liquid chemical solvent in nitrogen carrier gas to solubilize oils and heavy hydrocarbons and to further desorb light hydrocarbons and remove hydrogen sulfide (H2S), to effect decontamination. This process can be advantageously combined with nitrogen cool-down processes in preparation for catalyst unloading.