Multi-stage Hydroprocessing Tar with Recycled Utility Fluid
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current hydroprocessing methods for pyrolysis tars face challenges in reducing viscosity and improving blending compatibility due to fouling issues, which limits the production of upgraded tar products with desirable viscosity and density specifications without compromising reactor lifetime.
Innovation Solution
A multi-stage hydroprocessing process is employed, where pyrolysis tar is processed in at least two zones with a utility fluid obtained from a mid-cut stream, allowing for lower pressure operations and higher space velocities, reducing fouling and extending reactor run times by recycling the mid-cut stream as a solvent and further hydrogenating the bottoms stream to achieve lower sulfur and viscosity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hydroprocessing is carried out at conventional temperatures (250-380°C) and pressures (5400-20500 kPa) using conventional catalysts, then viscosity reduction is achieved, but rapid catalyst coking occurs and reactor lifetime is compromised
Solution Approach 1:
The patent applies parameter changes by operating at lower temperatures (200-300°C) and lower pressures (1000-1500 kPa) compared to conventional hydroprocessing conditions. This parameter modification reduces the rate of catalyst coking while maintaining effective viscosity reduction, thereby extending reactor lifetime without sacrificing product quality
Solution Approach 2:
The patent introduces a utility fluid as an intermediary substance that facilitates hydroprocessing at milder conditions. The utility fluid acts as a mediator between the catalyst and the pyrolysis tar, enabling effective hydroprocessing at lower temperatures and pressures while preventing rapid catalyst coking and extending reactor operation time
2Productivity
If hydroprocessing is carried out at higher space velocities, then productivity is improved, but fouling increases and reactor operation becomes unstable
Solution Approach 1:
The utility fluid serves as a protective intermediary that prevents direct contact between high-speed flowing tar and the catalyst bed, reducing fouling even at higher space velocities. This allows the system to operate at elevated productivity levels without experiencing excessive fouling that would destabilize reactor operation
Solution Approach 2:
The patent modifies operating parameters by adjusting temperature and pressure levels to optimize the balance between space velocity and fouling. These parameter changes enable higher productivity while maintaining stable reactor operation by preventing excessive fouling accumulation
3Adaptability or versatility
If pyrolysis tar with high molecular weight compounds is used, then blending compatibility is improved, but viscosity increases and desirable disposition options are limited
Solution Approach 1:
The utility fluid acts as a solubilizing intermediary that interacts with high molecular weight compounds in the pyrolysis tar. This intermediary substance enhances the solubility and blending compatibility of heavy components while simultaneously reducing the overall viscosity through its own molecular structure and interaction with the tar matrix
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 reduces the viscosity and sulfur content of the upgraded tar product, enhances compatibility with other hydrocarbons, and extends the lifespan of hydroprocessing reactors by minimizing fouling and catalyst deactivation.
Implementation Method 1
contacting the feedstock with at least one hydroprocessing catalyst in the presence of a utility fluid and molecular hydrogen under catalytic hydroprocessing conditions
Implementation Method 2
contacting the feedstock with at least one hydroprocessing catalyst in the presence of a utility fluid and molecular hydrogen under catalytic hydroprocessing conditions
Data Source
AI summary
A multi-stage process is described for upgrading pyrolysis tar, such as steam cracker tar, by hydroprocessing in at least two stages. Hydroprocessing in a first stage is performed in the presence of a utility fluid. The utility fluid has a boiling point distribution from about 120° C. to about 480° C. and is separated from the first stage product.