Pyrolysis Tar Thermal Treatment for Hydroprocessing Fouling
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Solution Overview
Problem
Pyrolysis tar, particularly steam cracker tar, poses challenges in hydroprocessing due to its high reactivity, leading to rapid catalyst deactivation and reactor fouling, which limits the reactor run length and yield of upgraded products.
Innovation Solution
A process involving thermal treatment of pyrolysis tar to reduce its reactivity, combined with a specified utility fluid, allows for hydroprocessing without excessive fouling by maintaining the tar-fluid mixture's reactivity below a reference level, as determined by the Bromine Number, enabling longer reactor run lengths under controlled conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pyrolysis tar is hydroprocessed to reduce viscosity and improve blending properties, then the upgraded tar has improved compatibility with fuel oils, but rapid catalyst deactivation and reactor fouling occur due to high reactivity of the tar
Solution Approach 1:
The patent applies preliminary thermal treatment to the pyrolysis tar before hydroprocessing to reduce its reactivity. The tar is heated to temperatures between 200-400°C for a specified residence time, which stabilizes the tar by reducing its reactive components. This preliminary action prevents catalyst deactivation during subsequent hydroprocessing while maintaining the ability to produce upgraded tar with improved blending properties.
Solution Approach 2:
The patent changes the temperature and residence time parameters of the tar to control its reactivity. By adjusting the thermal treatment temperature (200-400°C) and residence time, the reactivity of the tar is modified to an optimal level that allows hydroprocessing without excessive catalyst deactivation. This parameter control enables the process to achieve both catalyst stability and product upgrading.
2Reliability
If the reactivity of pyrolysis tar is reduced through thermal treatment, then catalyst deactivation is minimized, but the yield of upgraded products may be affected
Solution Approach 1:
The patent employs dynamic control of the thermal treatment conditions, adjusting temperature and residence time based on the specific tar composition and desired product specifications. This dynamic approach allows optimization of both catalyst stability and product yield for different operating conditions, rather than using fixed treatment parameters.
Solution Approach 2:
The patent modifies treatment parameters (temperature, residence time) to achieve the desired balance between catalyst stability and product yield. By carefully controlling these parameters, the process minimizes unwanted side reactions that would reduce yield while still sufficiently reducing reactivity to protect the catalyst.
3Shape
If heavy hydrocarbons are blended to improve tar processing and transport, then viscosity is reduced, but asphaltene precipitation occurs leading to fouling of equipment
Solution Approach 1:
The patent controls the temperature and composition parameters during blending to prevent asphaltene precipitation. By maintaining the tar at elevated temperatures during blending and using carefully selected blending components, the process reduces viscosity improvement while preventing the harmful precipitation of asphaltenes that would cause equipment fouling.
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
The process effectively reduces reactor fouling and extends hydroprocessing run lengths by controlling the reactivity of the tar-fluid mixture, improving the yield and compatibility of the upgraded pyrolysis tar with other blendstocks.
Implementation Method 1
The tar-fluid mixture is hydroprocessed, indicating catalytic hydrogenation reactions occur to reduce the reactivity of the pyrolysis tar components
Implementation Method 2
hydroprocessing using a conventional hydroprocessing catalyst containing one or more of Co, Ni, or Mo
Implementation Method 3
thermal treatment of pyrolysis tar to reduce its reactivity
Data Source
AI summary
This invention relates to a process for determining the suitability of pyrolysis tar, such as steam cracker tar, for upgrading using hydroprocessing without excessive fouling of the hydroprocessing reactor. The invention includes establishing a reference activity for the thermally treating the pyrolysis tar to produce a treated tar having a lesser reactivity.