Cold Box Cleaning With Reformate for Sulfur Deposit Removal
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Solution Overview
Problem
Existing methods, such as citric acid and related chemicals, are ineffective in cleaning sulfur deposits from cold boxes in cryogenic plants, leading to blockages and performance issues.
Innovation Solution
A method using reformate, a premium blend of hydrocarbons and impurities, including a methanol pre-flush, circulation of toluene reformate, and a methanol post-wash, to effectively remove sulfur deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If typical cleaning solutions such as citric acid and related chemicals with corrosion inhibitors are used, then the cleaning process is simple and safe for equipment, but sulfur deposits cannot be effectively removed
Solution Approach 1:
The patent changes the chemical composition parameters of the cleaning solution by introducing reformate (a hydrocarbon mixture containing aromatic compounds like toluene and xylene) combined with traditional acid cleaners. This parameter change enables effective sulfur deposit removal while maintaining equipment safety through controlled chemical properties.
Solution Approach 2:
The patent creates a composite cleaning solution by combining reformate (hydrocarbon mixture) with traditional acid cleaning agents and corrosion inhibitors. This composite formulation leverages the solvent power of reformate for sulfur deposits while maintaining the protective and cleaning benefits of traditional chemicals.
2Productivity
If sulfur deposits are not removed effectively, then the cleaning process remains simple using typical chemicals, but blockage issues occur in cold box components
Solution Approach 1:
The patent modifies the chemical parameters of the cleaning system by using reformate with specific aromatic content (40-80% aromatics, including 10-40% toluene and 10-40% xylene) to change how sulfur deposits are dissolved and removed, preventing blockages while improving productivity.
Solution Approach 2:
The patent applies a multi-step cleaning process that copies and combines effective elements from different cleaning approaches: the solvent action of reformate, the chelating action of citric acid, and the protective action of corrosion inhibitors, creating a comprehensive solution that prevents blockages.
3Reliability
If reformate is used to effectively remove sulfur deposits, then sulfur removal effectiveness improves, but the cleaning process complexity increases with multiple circulation steps
Solution Approach 1:
The patent segments the cleaning process into distinct phases: pre-flush with methanol, main cleaning circulation with reformate (including flow direction changes), and post-flush with methanol. Each segment serves a specific function, making the complex process manageable and effective for sulfur removal.
Solution Approach 2:
The patent employs periodic action through alternating flow directions (bottom-to-top and top-to-bottom circulation) and periodic replacement of reformate. This periodic circulation pattern ensures thorough contact with sulfur deposits throughout the cold box while managing process complexity.
4Reliability
If multiple circulation steps with flow path reversal are implemented, then sulfur removal completeness improves, but the time required for cleaning increases
Solution Approach 1:
The patent uses periodic circulation with flow direction reversal to achieve complete sulfur removal. By alternating between bottom-to-top and top-to-bottom flow paths, the process ensures all surfaces are adequately treated, completing sulfur removal in a controlled time frame despite the multiple steps.
Solution Approach 2:
The patent implements feedback monitoring by analyzing sulfur content in the circulating reformate and monitoring temperature changes across the heat exchanger. This feedback allows the process to determine when sulfur removal is complete, preventing unnecessary extended cleaning time while ensuring thoroughness.
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 method successfully restores the cold box exchanger to its design performance level by effectively removing sulfur, improving operational efficiency and preventing blockages.
Implementation Method 1
adding toluene reformate to a circulation tank and circulating the toluene reformate
Implementation Method 2
performing a methanol pre-flush of the cold box system
Data Source
AI summary
A method of cleaning a cold box of an exchanger includes performing a methanol pre-flush of the system and inspecting filters in a filtration unit. The method includes adding toluene reformate to circulation tank and circulating the toluene reformate. The method includes analyzing the circulating toluene reformate for sulfur content. The method includes starting a circulating pump and resuming circulation in a bottom to top flow. The method includes reversing circulation flow path to a top to bottom flow. The method includes returning the circulation flow path to the bottom to top flow and circulating the toluene reformate. The method includes starting the circulation pump and resuming circulation of the toluene reformate in the bottom to top flow path until sulfur levels are stable. The method includes emptying the toluene reformate from the system and flushing the system. The method includes performing a methanol post wash and dedusting the system.