Two-Stage Hydroprocessing with Dividing Wall Fractionation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
There is a need for cost-effective and efficient methods to produce ultra-low sulfur diesel (ULSD) that meet stringent product requirements without overtreating heavier portions of hydrocarbon streams, given the challenges of removing sulfur and nitrogen from liquid hydrocarbons in hydroprocessing.
Innovation Solution
The implementation of a two-stage hydroprocessing system using a dividing wall fractionation column, where the first hydroprocessing zone reduces sulfur concentration and improves cetane number, and the second zone further processes the diesel stream to achieve ULSD, utilizing a continuous liquid phase hydroprocessing and hydrotreating reactions with specific catalysts and hydrogen management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional hydroprocessing is used to remove sulfur and nitrogen from liquid hydrocarbons, then product quality meets regulatory requirements, but operational costs increase due to gas recovery, clean-up, compression and recycle requirements
Solution Approach 1:
The patent changes the phase parameter of hydrogen from gas to liquid by operating at elevated pressures (e.g., 100-300 atm) and temperatures (e.g., 300-450°C), enabling continuous liquid phase hydroprocessing. This eliminates the gas recycle system while maintaining effective sulfur and nitrogen removal through direct liquid-phase reaction with the feedstock
Solution Approach 2:
The patent extracts and eliminates the complex gas recovery, clean-up, compression and recycle system from the conventional hydroprocessing configuration. By using continuous liquid phase hydroprocessing, the harmful gas phase operations are removed entirely, simplifying the overall process while achieving the same contaminant removal effectiveness
2Manufacturing precision
If single-stage hydroprocessing is used to produce ULSD, then sulfur removal is achieved, but heavier portions of the product streams are overtreated increasing operational costs
Solution Approach 1:
The patent segments the hydroprocessing operation into two distinct stages: first stage for initial sulfur and nitrogen removal, and second stage for final ULSD production. The dividing wall fractionation column separates the feedstock into different boiling range fractions, allowing the second stage to process only the diesel-cut portion rather than the entire feedstream, thereby eliminating energy waste from overtreating heavier portions
Solution Approach 2:
The patent performs preliminary fractionation and sulfur removal in the first hydroprocessing stage before the second stage. By removing a significant portion of sulfur and nitrogen early, and separating fractions beforehand, the second stage operates more efficiently on a pre-conditioned feedstream, reducing the energy required for final ULSD production
3Quantity of substance
If continuous liquid phase hydroprocessing is used, then hydrogen requirements are reduced to just over stoichiometric, but the system requires sophisticated fractionation and two-stage processing
Solution Approach 1:
The patent merges the fractionation function into the hydroprocessing system itself through the dividing wall fractionation column. This integrated approach combines separation and reaction functions, where the column simultaneously fractionates the feedstock and provides the basis for selective second-stage hydroprocessing, reducing overall system complexity despite the two-stage configuration
Solution Approach 2:
The dividing wall fractionation column serves multiple functions: it separates the feedstock into different boiling range fractions, directs appropriate fractions to the second hydroprocessing stage, and enables selective processing. This multi-functional component reduces the need for separate dedicated fractionation and reaction systems, offsetting the complexity of continuous liquid phase operation
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 produces ULSD by efficiently removing sulfur and nitrogen, optimizing hydrogen usage, and avoiding the need for gas recycle streams, thus reducing operational costs and improving product quality.
Implementation Method 1
A dividing wall fractionation column includes a dividing wall extending to a bottom of the dividing wall fractionation column that divides the dividing wall fractionation column into a first side and a second side
Implementation Method 2
Hydrotreating is a type of hydroprocessing primarily active for the removal of heteroatoms, such as sulfur and nitrogen, and saturation of compounds in the hydrocarbon feedstock
Data Source
AI summary
Two-stage hydroprocessing uses a common dividing wall fractionator. Hydroprocessed effluents from both stages of hydroprocessing are fed to opposite sides of the dividing wall.