Hydroprocessing Pyrolysis Tar with Utility Fluid to Reduce Fouling
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Solution Overview
Problem
Pyrolysis tar, particularly steam-cracker tar, is challenging to process due to its high viscosity and molecular weight, leading to equipment fouling and reduced yield during hydroprocessing, as it forms coke deposits and precipitates asphaltenes, making it difficult to blend with other hydrocarbons effectively.
Innovation Solution
Hydroprocessing pyrolysis tar in the presence of a utility fluid with a high solubility blending number (SBN) and aromatic content, under specific conditions of pressure (>8 MPa) and hydrogen consumption rate (1600-2400 SCF per barrel), to reduce viscosity and density, thereby minimizing reactor plugging and extending catalyst life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydroprocessing is carried out at conventional temperatures (250-380°C) and pressures (5400-20500 kPa), then hydrogenation and hydrocracking reactions occur, but rapid catalyst coking and equipment fouling result from high molecular weight tar heavies forming coke deposits
Solution Approach 1:
The patent applies parameter changes by operating at elevated temperatures (400-500°C) and pressures (100-200 atm) to modify the reaction conditions. These parameter changes promote hydrogenation of aromatic rings and reduce the formation of coke deposits, thereby extending catalyst life while maintaining hydroprocessing productivity
Solution Approach 2:
The patent introduces a utility fluid as an intermediary substance that contains aromatic hydrocarbons. This utility fluid acts as a mediator between the tar heavies and the catalyst, facilitating hydrogenation reactions and preventing direct contact between highly reactive tar components and the catalyst surface, thus reducing coking
2Adaptability or versatility
If pyrolysis tar is blended with heavy hydrocarbons to find higher-value uses, then potential applications in fluxing and fuel blending arise, but phase separation and precipitation of asphaltenes occur due to high incompatibility number
Solution Approach 1:
The patent modifies the chemical composition parameters of pyrolysis tar through hydroprocessing, specifically reducing the incompatibility number by hydrogenating aromatic rings and removing heteroatoms. This parameter change enables stable blending with heavy hydrocarbons by adjusting the chemical properties to match those of fuel oils and other hydrocarbon products
Solution Approach 2:
The patent converts the harmful effect of high aromatic content and heteroatoms in pyrolysis tar (which cause phase separation) into beneficial effects through hydroprocessing. The same components that cause instability are transformed into saturated hydrocarbons that enhance blend stability and compatibility with fuel products
3Ease of operation
If hydroprocessing is performed to reduce viscosity and improve blendability, then upgraded tar product is produced, but reactor plugging increases due to precipitation of high molecular weight molecules
Solution Approach 1:
The patent applies parameter changes by operating at elevated temperatures (400-500°C) and pressures (100-200 atm) to modify the reaction conditions. These parameter changes promote hydrogenation of aromatic rings and reduce the formation of coke deposits, thereby extending catalyst life while maintaining hydroprocessing productivity
Solution Approach 2:
The patent introduces a utility fluid as an intermediary substance that contains aromatic hydrocarbons. This utility fluid acts as a mediator between the tar heavies and the catalyst, facilitating hydrogenation reactions and preventing direct contact between highly reactive tar components and the catalyst surface, thus reducing coking
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 decreases the density and viscosity of the upgraded tar product, improving its compatibility with heavy hydrocarbons and extending the hydroprocessing reactor's operational life by reducing fouling and increasing hydrogen consumption efficiency.
Implementation Method 1
hydroprocessing the combined pyrolysis tar and utility fluid in at least one hydroprocessing zone in the presence of treatment gas comprising molecular hydrogen under catalytic hydroprocessing conditions
Implementation Method 2
catalytic hydroprocessing conditions
Implementation Method 3
combining the components in order of decreasing SBN, so that the SBN of the blend is greater than the IN of any component of the blend
Data Source
AI summary
A process is described for upgrading pyrolysis tar, such as steam cracker tar, by hydroprocessing in the presence of a utility fluid. The hydroprocessing conditions comprise a pressure >8 MPa and a weight hourly space velocity of combined pyrolysis tar and utility fluid >0.3 hr−1 and are selected so that the hydrogen consumption rate is in the range of 270 to 445 standard cubic meters/cubic meter (S m3/m3) of pyrolysis tar.