Two-Stage Delayed Coking for Anode Grade Coke
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Solution Overview
Problem
Conventional methods for producing high quality coke are expensive due to the high pressure requirement of upstream hydroprocessing, which is necessary to purify residual oil and increase coke yield, as residual oil contains significant amounts of asphaltenes and impurities.
Innovation Solution
A two-stage delayed coking process is employed, where the first delayed coker unit produces fuel coke from asphaltenes, and the resin-rich effluent is further processed in a second delayed coker unit to produce high grade coke, such as anode or needle coke, thereby reducing the need for expensive hydroprocessing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If upstream hydroprocessing is used to purify residual oil, then coke yield and quality are improved, but production cost increases due to high pressure requirements
Solution Approach 1:
The coking process is divided into two distinct stages: a first delayed coker unit that processes asphaltenes to produce fuel coke, and a second delayed coker unit that processes the resin-rich effluent to produce high grade anode coke. This segmentation allows each unit to be optimized for its specific function, eliminating the need for expensive hydroprocessing while maintaining high coke quality.
Solution Approach 2:
The invention extracts and removes asphaltenes from the residual oil feedstock in the first coking stage, separating them from the resin fraction. This extraction eliminates the harmful asphaltenes that would otherwise require expensive hydroprocessing, allowing the resin-rich effluent to be directly coked to high grade coke in the second stage.
2Productivity
If conventional single-stage delayed coking is used, then process simplicity is maintained, but high grade coke yield is limited due to asphaltenes and impurities in residual oil
Solution Approach 1:
The coking process is divided into two distinct stages: a first delayed coker unit that processes asphaltenes to produce fuel coke, and a second delayed coker unit that processes the resin-rich effluent to produce high grade anode coke. This segmentation allows each unit to be optimized for its specific function, eliminating the need for expensive hydroprocessing while maintaining high coke quality.
Solution Approach 2:
Each coker unit is designed with specific local quality characteristics appropriate to its function: the first unit handles asphaltenes with conditions optimized for their rapid coking, while the second unit handles resin-rich effluent with conditions optimized for producing high grade coke. This local optimization maximizes high grade coke yield from the resin fraction.
3Ease of manufacture
If residual oil with asphaltenes is directly coked, then hydroprocessing cost is avoided, but coke quality deteriorates due to impurities
Solution Approach 1:
The invention performs preliminary coking of asphaltenes in the first delayed coker unit before the resin-rich effluent is sent to the second unit. This preliminary action removes asphaltenes and their associated impurities from the feedstock, ensuring that the second coking stage receives clean resin-rich effluent that can be converted to high grade coke without requiring expensive hydroprocessing.
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 process increases the yield of high grade coke while reducing the cost associated with hydroprocessing, as the resin-rich effluent is effectively coked in the second stage to meet high grade coke specifications, improving overall efficiency and reducing production costs.
Implementation Method 1
passing the bottoms fraction to a delayed coker unit furnace for heating to a predetermined coking temperature
Implementation Method 2
the feed is cracked to form light products while heavy free radical molecules form heavier polynuclear aromatic compounds, which are referred to as 'coke'
Implementation Method 3
the rate of coking for asphaltenes is approximately 10 times faster than that for resins due to molecular structures, solubility and other thermodynamic factors
Implementation Method 4
the resin may be coked to produce high grade coke e.g., the anode grade coke, needle coke, or both
Data Source
AI summary
A delayed coking process for producing high grade coke comprising: introducing a hydrocarbon feedstock comprising asphaltenes to at least one fractionator to produce at least a bottoms fraction, an intermediate fraction and a light naphtha fraction: passing the bottoms fraction to a delayed coker unit furnace for heating to a predetermined coking temperature; passing the heated bottoms fraction to a first delayed coker unit to produce a first coke product and a first effluent substantially free of asphaltenes and comprising resins; and passing the first effluent to a second delayed coker unit to produce a second coke product comprising the high grade coke.