Hydrotreating Feed Corrosion Mitigation via Hydrogen
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Solution Overview
Problem
The corrosion of oils and fats in the upstream portion of a hydrotreating unit, particularly in heat exchangers and feed/storage tanks, poses challenges due to the breakdown of triglycerides into free fatty acids, leading to potential corrosion issues and high costs associated with diluting acids or upgrading metallurgy.
Innovation Solution
A process involving passing a triglyceride feedstock through a metal apparatus under controlled conditions of temperature (150° C. to 550° C.), pressure (50 psig to 2000 psig), and residence time (0.001 hour to 5 hours), with the option of co-feeding hydrogen, which significantly reduces corrosion by inhibiting the corrosiveness of oils and fats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If vegetable oil and fats are processed through hydrotreating to produce hydrocarbons, then alternative fuel production is achieved, but corrosion issues arise in the upstream portion of the hydrotreating unit due to free fatty acids
Solution Approach 1:
The patent applies preliminary action by treating the triglyceride feedstock with hydrogen in a separate pre-treatment step before it enters the main hydrotreating unit. This preliminary hydrogen treatment reduces the formation of free fatty acids that would otherwise cause corrosion in upstream equipment, thereby protecting the system while enabling alternative fuel production
Solution Approach 2:
The patent uses hydrogen as an intermediary substance that mediates between the triglyceride feedstock and the hydrotreating process. The hydrogen reacts with the triglycerides in a controlled manner to prevent the formation of corrosive free fatty acids, acting as a protective intermediary that enables the overall process to proceed without corrosion damage
2Object-affected harmful factors
If free fatty acid content in oils and fats is reduced through dilution with low acid feedstock, then corrosion is mitigated, but production costs increase due to requiring more expensive non acidic crude
Solution Approach 1:
The patent employs a cheap and readily available substance (hydrogen gas) to achieve corrosion mitigation, replacing the need to purchase expensive non-acidic crude oil for dilution. The hydrogen is consumed in the pre-treatment reaction and does not need to be recovered, making it an economical solution compared to buying costly alternative feedstocks
3Object-affected harmful factors
If metallurgy is upgraded to corrosion-resistant alloys, then corrosion resistance is improved, but capital costs increase substantially
Solution Approach 1:
The patent applies preliminary action by removing or preventing the formation of corrosive free fatty acids before the feedstock contacts the metal equipment in the hydrotreating unit. This preventive approach allows the use of standard, less expensive metallurgy rather than requiring costly corrosion-resistant alloys, as the corrosive agent is eliminated in advance
4Productivity
If residence time of oils/fats in metal apparatus is extended, then triglyceride conversion is improved, but corrosiveness increases due to breakdown into free fatty acids
Solution Approach 1:
The patent applies preliminary action by conducting hydrogen treatment before the triglycerides undergo extensive breakdown in the main hydrotreating process. This preliminary hydrogenation step modifies the triglyceride structure in advance to prevent excessive free fatty acid formation during subsequent processing, enabling longer residence times without increased corrosion
Solution Approach 2:
The patent changes the chemical parameters of the feedstock by introducing hydrogen, which alters the reaction pathway of triglyceride breakdown. This parameter change (adding hydrogen) modifies how triglycerides decompose, reducing the formation of free fatty acids even when residence time is extended, thus decoupling conversion efficiency from corrosiveness
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 effectively mitigates corrosion rates by controlling residence time and using hydrogen, thereby reducing the need for costly metallurgy upgrades and dilution methods, making it economically viable for producing hydrocarbons from triglycerides.
Implementation Method 1
the presence of hydrogen in the metal apparatus can also inhibit the corrosion rate of oils/fats
Implementation Method 2
triglycerides that make up the bulk of both oils and fats may break down under heated conditions to produce additional free fatty acid
Data Source
AI summary
It has been discovered that the residence time of oils/fats in metal apparatus, particularly in the upstream of a hydrotreating unit, for example, a heat exchanger and/or a storage/feed tank, can impact significantly on corrosiveness of oils/fats in combination with and without conventional hydrocarbons. In addition, it is also found that the presence of hydrogen in the metal apparatus can also inhibit the corrosion rate of oils/fats.