Hydroprocessing Wash Water Corrosion Control
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Solution Overview
Problem
Hydroprocessing units treating renewable feeds face challenges with carbonic acid corrosion of carbon steel equipment, which existing methods do not adequately address, particularly when using sour waste water from other units processing nitrogen and sulfur-containing feeds.
Innovation Solution
Reusing sour waste water from units processing nitrogen and sulfur-containing feeds as wash water in hydroprocessing units treating renewable feeds to reduce corrosion risk and increase hydrogen sulfide concentration, thereby eliminating the need for Duplex stainless steel and using chemicals like ammonia to control pH and form protective iron sulfide films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If condensate or treated water from sour water stripper is used as wash water, then the equipment is protected from carbonic acid corrosion, but the volume of waste water to treatment facility increases and Duplex stainless steel material is required
Solution Approach 1:
The invention converts the harmful sour waste water containing H2S into a beneficial substance that protects carbon steel equipment from carbonic acid corrosion. The H2S in the sour waste water forms a protective iron sulfide film on the carbon steel surfaces, eliminating the need for Duplex stainless steel while reducing waste water volume to treatment facilities.
Solution Approach 2:
The invention changes the chemical composition parameters of the wash water by introducing sour waste water containing H2S, NH3, and other compounds. This alters the chemical environment from corrosive (carbonic acid) to protective (iron sulfide film-forming), allowing the use of carbon steel instead of expensive Duplex stainless steel.
2Reliability
If Duplex stainless steel is used for equipment, then carbonic acid corrosion is prevented, but the cost of materials and complexity increase
Solution Approach 1:
The harmful H2S-containing sour waste water is converted into a protective agent that forms iron sulfide films on carbon steel surfaces. This eliminates the need for expensive Duplex stainless steel materials, reducing both material costs and equipment complexity while maintaining corrosion protection.
Solution Approach 2:
The invention replaces expensive Duplex stainless steel with inexpensive carbon steel by introducing a chemical protective mechanism (H2S-based film formation). This uses a cheap material (carbon steel) protected by a chemical barrier rather than relying on expensive corrosion-resistant alloys.
3Reliability
If sour waste water is used as wash water, then corrosion risk is reduced and waste water volume decreases, but the hydrogen sulfide concentration in recycle gas must be increased to maintain catalyst activity
Solution Approach 1:
The H2S that would normally be considered a contaminant or waste product is converted into a beneficial substance that maintains catalyst activity. The sour waste water provides H2S that prevents carbonic acid corrosion and keeps base metal catalysts in the active sulfided state, addressing two problems simultaneously.
Solution Approach 2:
The sour waste water serves multiple functions: (1) protects equipment from carbonic acid corrosion by forming iron sulfide films, (2) reduces waste water volume to treatment facilities, and (3) provides H2S to maintain catalyst activity. This multi-functionality resolves the apparent contradiction between corrosion protection and H2S concentration requirements.
4Reliability
If chemicals are added to control pH, then corrosion is prevented, but additional chemicals and treatment complexity are required
Solution Approach 1:
The system uses the sour waste water's own chemical composition (H2S, NH3, organic acids) to self-regulate the pH and form protective films on equipment surfaces. This eliminates or reduces the need for external chemical additives and complex pH control systems, as the sour waste water itself provides the corrosion protection mechanism.
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 effectively reduces the risk of carbonic acid corrosion, decreases the volume of sour water requiring treatment, and maintains catalyst activity by recycling hydrogen sulfide, thus minimizing the need for additional corrosion protection materials and chemicals.
Implementation Method 1
The sour waste water from a unit which processes feeds containing nitrogen (NH3) and sulfur (H2S) is used as washing water in a hydroprocessing unit which treats renewable feeds
Implementation Method 2
The ammonia in the waste water from other hydroprocessing units will raise the pH of the waste water from the unit treating renewable feeds
Implementation Method 3
increasing the hydrogen sulfide concentration in the recycle gas to aid in keeping the base metal catalysts in the active sulfided state
Data Source
AI summary
In a method for the hydroprocessing of renewable feeds in a hydroprocessing unit (unit A), comprising the use of sour waste water from the same or another unit (unit B), which is processing feeds containing sulfur and nitrogen, as wash water in unit A, thereby changing the pH of the waste water from unit A to lower the risk of carbonic acid corrosion of corrodible steel parts in unit A, the renewable material in unit A is directed to contact a material that is catalytically active in hydrogenating the renewable material in the presence of hydrogen, and the effluent is combined with the wash water stream which contains hydrogen sulfide and/or ammonia.