Pyrolysis Tar Hydroprocessing Utility Fluid
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Solution Overview
Problem
Pyrolysis tar hydroprocessing in hydroprocessing reactors experiences significant reactor pressure drop due to fouling, leading to reduced recovery rates and frequent shutdowns for catalyst rejuvenation, especially when transitioning from catalyst activation to hydroprocessing mode or with changes in pyrolysis tar composition.
Innovation Solution
The process involves hydroprocessing pyrolysis tar with a utility fluid comprising ≥90.0 wt. % aromatics and ≤10.0 wt. % paraffins, where the pyrolysis tar:utility fluid weight ratio is periodically decreased to mitigate fouling-induced pressure drops by introducing additional utility fluid, and the activating fluid is substituted with utility fluid before introducing pyrolysis tar, maintaining reactor temperature and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pyrolysis tar is hydroprocessed in a hydroprocessing reactor, then the tar is upgraded to higher-value products, but reactor pressure drop increases rapidly due to fouling and catalyst coking
Solution Approach 1:
A utility fluid (aromatic hydrocarbon) is introduced as an intermediary substance to mix with the pyrolysis tar feedstock before entering the hydroprocessing reactor. This utility fluid acts as a mediator that reduces fouling and catalyst coking, enabling continuous operation while maintaining tar upgrading productivity.
Solution Approach 2:
The composition parameters of the feed mixture are changed by controlling the ratio of utility fluid to pyrolysis tar. By adjusting this ratio, the process optimizes between maintaining high tar upgrading rates and preventing excessive pressure drop that would require shutdowns.
2Reliability
If catalyst coking is reduced by operating at elevated hydrogen partial pressure, then catalyst life is extended, but hydrogen demand and equipment costs increase
Solution Approach 1:
The utility fluid serves as an intermediary that protects the catalyst from coking by forming a protective layer or modifying the reaction environment, thereby reducing the need for high hydrogen partial pressure and associated costs.
3Reliability
If reactor pressure drop is reduced by adding utility fluid, then continuous operation is enabled, but the complexity of feed mixture preparation increases
Solution Approach 1:
The utility fluid performs multiple functions simultaneously: it acts as a feed diluent to reduce fouling, serves as a hydrogen carrier, and functions as a process control medium. This multi-functionality simplifies the overall system despite the added mixing requirement.
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 significantly reduces reactor pressure drop, allowing continuous operation for extended periods without shutdowns, maintaining reactor efficiency, and preventing fouling by using the specified utility fluid to dislodge accumulated foulants, thereby enhancing tar recovery and process stability.
Implementation Method 1
combining pyrolysis tar with a utility fluid upstream of the hydroprocessing in order to lessen the rate of increase in reactor pressure-drop
Implementation Method 2
the presence in the SCT of molecules having an atmospheric boiling point ≧565° C., known as 'tar heavies', which include asphaltenes and other high molecular weight molecules
Implementation Method 3
converting pyrolysis tar in a hydroprocessing reactor
Implementation Method 4
these conditions favor undesired hydrogenation reactions
Implementation Method 5
operating the process at an elevated hydrogen partial pressure
Implementation Method 6
operating the process at an elevated hydrogen partial pressure
Data Source
AI summary
The invention relates to pyrolysis tar upgrading processes, and in particular for decreasing reactor pressure drop when the upgrading includes converting pyrolysis tar in a reactor. The invention also relates to upgraded pyrolysis tar, and the use of upgraded pyrolysis tar, e.g., as a fuel oil blending component.