Needle Coke Production with Solvent Purification of Mixed Pitch
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Solution Overview
Problem
Existing methods for producing needle coke are costly and adversely affect the quality due to high impurity levels, particularly quinoline insoluble (QI), leading to issues like high thermal expansion coefficient and reduced crystallinity, which impact the performance and efficiency of graphite electrodes.
Innovation Solution
A process involving multi-residence time mild thermal cracking of coal tar pitch with petroleum streams, followed by solvent-assisted separation of undesirable QI and solid catalyst fines, and delayed coking to produce high-quality needle coke.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If hydrogenation process is used to separate impurities from coal tar pitch, then impurity removal is improved, but production cost increases and aromatic content decreases
Solution Approach 1:
The patent uses solvent extraction to remove quinoline insoluble impurities from coal tar pitch. The solvent selectively dissolves the pitch components while leaving QI impurities undissolved, allowing their separation through filtration. This extraction method achieves effective impurity removal without the high costs and aromatic content loss associated with hydrogenation.
2Manufacturing precision
If hydrogenation process is used to separate impurities from coal tar pitch, then impurity removal is improved, but aromatic content and reactivity decrease
Solution Approach 1:
The solvent extraction process selectively removes QI impurities while preserving the aromatic structure of the pitch. The solvent interacts with the pitch components through solvation without breaking aromatic bonds, maintaining the high aromatic content (95-100%) and reactivity needed for quality needle coke production.
Solution Approach 2:
The solvent acts as an intermediary that facilitates impurity removal through selective solvation. It forms a solvent-pitch complex that can be separated from QI impurities, enabling purification without direct chemical modification of the aromatic pitch structure.
3Quantity of substance
If coal tar pitch with high QI content is used for needle coke production, then feedstock availability is improved, but coke quality deteriorates due to high thermal expansion coefficient
Solution Approach 1:
The patent applies preliminary solvent extraction treatment to coal tar pitch before coking to remove QI impurities. This pre-treatment prevents the formation of high CTE needle coke by eliminating the problematic impurities that would otherwise be incorporated into the coke structure during carbonization.
4Device complexity
If solid catalyst fines are not removed from petroleum streams before mixing with tar oil, then process simplicity is maintained, but coke quality deteriorates
Solution Approach 1:
The patent incorporates a filtration step to remove solid catalyst fines from petroleum streams before mixing with tar oil. This simple filtration operation effectively eliminates the harmful solid particles that would otherwise degrade coke quality, adding minimal complexity to the overall process.
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 enhances coke yield and quality by optimizing residence time, controlling impurity removal, and improving crystallinity, resulting in a lower thermal expansion coefficient and tailored feed composition for graphite electrodes.
Implementation Method 1
subjecting a feed stream to a multi-residence time mild thermal cracking in the presence of petroleum streams to obtain a mixed pitch
Implementation Method 2
purifying the mixed pitch through a solvent-assisted selective separation of undesirable quinoline insoluble (QI) and solid catalyst fines from the mixed pitch
Implementation Method 3
subjecting the purified mixed pitch to delayed coking to produce the needle coke and a lighter hydrocarbon component
Data Source
AI summary
The present invention relates to a process for needle coke production by co-processing coal tar pitch (CTP) with petroleum streams. The process utilizes a ‘multi-residence time mild thermal cracking’ of coal tar pitch with petroleum streams (CLO, PFO) followed by solvent-assisted selective separation of undesirable quinoline insoluble (QI) and solid catalyst fines from the mixed pitch and delayed coking thereafter to produce needle coke. The solvent employed for feedstock purification is a mixture prepared from an aromatic solvent which is a lighter fraction formed by mild and severe thermal cracking of mixed feedstock, an aliphatic solvent and a polar extraction solvent.