Vacuum Flasher Hydrocracking Feed Segmentation
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Solution Overview
Problem
Refineries with moderate production volumes face challenges in optimizing capital and operating costs due to the complexity of crude distillation units, particularly in the hydrotreatment of residue streams which require high residence times and large reactors, and the high investment and operating costs associated with vacuum distillation units.
Innovation Solution
A process that directs a poorly separated stream of heavy hydrocarbons from the crude distillation unit to a vacuum flasher unit, followed by hydrocracking, which separates the least reactive hydrocarbons and reduces the need for large reactors, thereby optimizing the balance between capital and operating costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If residue stream is hydrotreated in a residue hydrotreater, then heteroatoms are removed from hydrocarbons, but the reactor becomes very large due to high residence time requirements
Solution Approach 1:
The process segments the crude distillation into multiple fractions (light gas oil, heavy gas oil, vacuum gas oil, residue) and directs only suitable fractions (light and heavy gas oils) to the hydrocracker, while excluding the least reactive residue components. This segmentation allows effective heteroatom removal in a smaller reactor by processing only reactive feedstocks.
Solution Approach 2:
The process extracts and removes the least reactive hydrocarbon components from the feed stream before hydrocracking through the fractionation scheme. By taking out these unreactive components that would require excessive residence time, the hydrocracker reactor volume is significantly reduced while maintaining effective hydrotreatment of the remaining reactive fractions.
2Measurement precision
If vacuum distillation unit is used to separate residue stream, then separation efficiency is improved, but investment and operating costs increase
Solution Approach 1:
The process uses a simplified fractionation scheme that segments the crude into four main fractions using conventional distillation towers, avoiding the need for complex vacuum distillation units. This segmentation provides sufficient separation for the hydrocracking feed selection without the high investment and operating costs of vacuum distillation equipment.
Solution Approach 2:
The process employs conventional, simpler distillation equipment rather than expensive vacuum distillation units. By using readily available and less complex fractionation technology, the process achieves adequate separation at lower capital and operating costs, sacrificing some separation precision for economic efficiency.
3Ease of manufacture
If direct draw from crude distillation unit is processed, then capital cost is reduced, but operating cost increases due to high residence time requirements
Solution Approach 1:
The process segments the direct draw from crude distillation into reactive fractions (light and heavy gas oils) and unreactive residue, directing only the reactive portions to hydrocracking. This segmentation eliminates the need for long residence times by excluding unreactive components, reducing operating costs while maintaining simple capital structure.
Solution Approach 2:
The process extracts and removes the unreactive residue components from the direct draw before hydrocracking. By taking out these components that would require excessive residence time and energy consumption, the process reduces operating costs while maintaining the capital cost advantages of direct processing.
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 reduces hydrogen consumption and moderates residence time and pressure requirements during hydrocracking, leading to cost savings and increased efficiency in producing middle distillate fuels while minimizing equipment size and yield loss.
Implementation Method 1
the heavy tail is separated by means of a vacuum flasher unit
Implementation Method 2
vacuum flasher unit may either be a simple flash drum separating two phases under sub-atmospheric pressure
Implementation Method 3
directing said light hydrocarbon mixture for hydrocracking and a stream rich in hydrogen to contact a material catalytically active in hydrocracking
Implementation Method 4
hydrocracking, which separates the least reactive hydrocarbons
Data Source
AI summary
In a broad aspect the present disclosure relates to a process plant and a process for upgrading a hydrocarbon mixture, withdrawn as a direct stream from a crude distillation unit and an initial boiling point below 200° C., and a fraction of at least 5% boiling above 500° C., 550° C. or 650° C. comprising the steps of a. directing said hydrocarbon mixture to a vacuum flasher unit, b. withdrawing a heavy hydrocarbon fraction from said vacuum flasher unit, c. withdrawing a light hydrocarbon mixture for hydrocrackingfrom said vacuum flasher unit, d. directing said light hydrocarbon mixture for hydrocracking and a stream rich in hydrogen to con-tact a material catalytically active in hydrocracking, e. withdrawing a hydrocracked stream of hydrocarbon from said hydrocracker. with the associated benefit of limiting the amount of asphaltenes, metals and other heavy components contacting said material catalytically active in hydrocracking.