Mixed Feedstock Needle Coke Processing for Sulfur and Thermal Stability
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Solution Overview
Problem
Existing methods for producing needle coke using catalytic slurry oil and ethylene tar face issues such as high ash and sulfur content, requiring solid-removal and hydrodesulfurization treatments, and poor thermal stability leading to incomplete polymerization and short operation periods in delayed coking units.
Innovation Solution
A method and apparatus involving the hydrotreatment of a mixture of feedstock oils with specific aromatic carbon ratios and temperature differences, followed by cracking and separation to produce high-quality needle coke, utilizing ethylene tar to enrich aromatics and catalytic slurry oil to reduce sulfur and improve thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If catalytic slurry oil is used as feedstock for needle coke production, then the sulfur content is high requiring hydrodesulfurization treatment, but the aromatic ring saturation increases and produces excessive alkyl side chains that hinder polymerization
Solution Approach 1:
The patent changes the hydrodesulfurization process parameters by introducing a two-stage approach with different temperature and pressure conditions. The first stage uses milder conditions (lower temperature, higher pressure) to selectively remove sulfur while preserving aromatic rings. The second stage uses stronger conditions to complete desulfurization. This parameter optimization reduces excessive hydrogenation while maintaining high aromatic content necessary for needle coke formation.
Solution Approach 2:
The patent introduces an intermediary substance - a specific catalyst system comprising nickel and sulfur promoters on an alumina support. This catalyst selectively facilitates hydrodesulfurization while minimizing aromatic ring saturation. The catalyst acts as a mediator that allows sulfur removal without the excessive hydrogenation that would occur with conventional catalysts, thus preserving the aromatic structure needed for polymerization.
2Reliability
If ethylene tar is used as feedstock for needle coke production, then the colloid content is high requiring removal treatment, but the thermal stability is poor causing easy polycondensation under high temperature
Solution Approach 1:
The patent applies preliminary action by performing colloid removal and aromatic enrichment treatments on ethylene tar before it enters the coking unit. The process includes extraction to remove colloidal materials and selective hydrogenation to stabilize the aromatic structure. This preliminary treatment prevents thermal instability issues during subsequent high-temperature coking operations, allowing longer operation periods.
Solution Approach 2:
The patent optimizes process parameters including temperature, pressure, and residence time in the coking unit to match the modified feedstock composition. By adjusting these parameters, the process achieves optimal balance between colloid removal and thermal stability preservation, preventing premature polycondensation while maintaining high aromatic content for quality needle coke production.
3Reliability
If hydrogenation treatment is applied to catalytic slurry oil, then the sulfur content is reduced, but the carbon-carbon double bonds of aromatic rings are saturated converting to alkyl side chains
Solution Approach 1:
The patent employs a specialized catalyst system as an intermediary that selectively promotes hydrodesulfurization while suppressing aromatic ring hydrogenation. The nickel-based catalyst with sulfur promoters facilitates sulfur removal through hydrodesulfurization mechanism without the excessive hydrogenation that would saturate aromatic rings and create alkyl side chains. This selective catalysis preserves the harmful-free aromatic structure needed for needle coke formation.
Solution Approach 2:
The patent optimizes hydrogenation process parameters including hydrogen pressure, temperature, and catalyst quantity to achieve selective hydrodesulfurization. By controlling these parameters, the process removes sulfur effectively while minimizing aromatic ring saturation. The optimized conditions allow sulfur removal without excessive alkyl side chain formation, maintaining the aromatic character necessary for quality needle coke production.
4Ease of manufacture
If delayed coking unit operates with ethylene tar, then the production process is simplified, but the operation period is short due to poor thermal stability
Solution Approach 1:
The patent applies preliminary treatment actions including colloid removal through extraction and aromatic structure stabilization through selective hydrogenation before the feedstock enters the delayed coking unit. These preliminary actions prepare the feedstock to be thermally stable during coking operations, preventing premature polycondensation and extending the operation period while maintaining process simplicity.
Solution Approach 2:
The patent introduces an intermediary treatment stage with a specific catalyst system that stabilizes the thermal properties of ethylene tar-derived feedstock. This intermediary catalytic treatment modifies the molecular structure to improve thermal stability without complicating the overall coking process. The stabilized feedstock can then undergo delayed coking for extended periods without premature degradation or polycondensation.
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 method enhances the quality and yield of needle coke by improving aromatic ring saturation and reducing excessive alkyl side chains, increasing naphtha yield, and optimizing the utilization of feedstock components, thereby extending the operation period of coking units.
Implementation Method 1
hydrotreating a mixture of a first feedstock oil and a second feedstock oil to obtain a hydrogenated product
Implementation Method 2
cracking the hydrogenated product to obtain a cracked product
Data Source
AI summary
A method for producing a needle coke includes the following steps: (1) hydrotreating a mixture of a first feedstock oil and a second feedstock oil to obtain a hydrogenated product; (2) cracking the hydrogenated product to obtain a cracked product; and (3) producing the needle coke with the cracked product as a starting material. The first feedstock oil has an aromatic carbon ratio of greater than 65 mol %, the second feedstock oil has an aromatic carbon ratio of greater than 60 mol %, the first feedstock oil has a coking starting temperature lower than that of the second feedstock oil by 10-140° C. The apparatus for carrying out the method is also provided.