Delayed Coking Feedstock Modification for Diesel Yield
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Solution Overview
Problem
Conventional delayed coking processes struggle to maximize diesel oil production while minimizing coke production, as they often result in excessive coke formation and reduced diesel oil yields due to inefficient feedstock modification in Delayed Coking Units.
Innovation Solution
Modifying the feedstock by adding a fraction of heavy vacuum gas oil to the vacuum residuum within the Delayed Coking Unit, which is then processed without a heavy gas oil recycle, to optimize thermal cracking reactions and reduce coke formation, thereby increasing diesel oil yield and decreasing coke production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional delayed coking process is used with vacuum residuum feedstock, then coke production is maintained, but diesel oil production is reduced and yield is suboptimal
Solution Approach 1:
The invention changes the compositional parameters of the feedstock by blending vacuum residuum with a specific fraction of heavy vacuum gas oil (boiling range 300-500°C). This parameter modification optimizes the thermal cracking behavior to increase diesel oil yield while reducing coke formation, directly resolving the contradiction between maximizing diesel production and minimizing coke loss.
Solution Approach 2:
The invention creates a composite feedstock by combining two different petroleum fractions: vacuum residuum and heavy vacuum gas oil. This composite material has optimized properties for delayed coking, achieving better diesel oil production and reduced coke formation compared to using vacuum residuum alone.
2Productivity
If heavy gas oil recycle is used in delayed coking, then operational flexibility is maintained, but diesel oil yield is reduced and process efficiency decreases
Solution Approach 1:
The invention extracts and eliminates the heavy gas oil recycle stream from the conventional delayed coking process. By removing this recycle loop and instead using a controlled blend of fresh heavy vacuum gas oil fraction with vacuum residuum, the process achieves higher diesel oil yield while maintaining operational control through the defined blending ratio.
3Productivity
If thermal cracking reactions are intensified to increase diesel oil production, then diesel yield improves, but coke formation increases excessively
Solution Approach 1:
The invention modifies the feedstock composition parameters by adding a controlled fraction of heavy vacuum gas oil (10-40% by volume) to vacuum residuum. This compositional change optimizes the thermal cracking reactions to produce more diesel oil while suppressing excessive coke formation, effectively resolving the contradiction between intensifying cracking for higher diesel yield and controlling harmful coke generation.
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 significantly increases diesel oil production and reduces coke production, as demonstrated by pilot unit examples showing improved volume and mass yields, indicating a more efficient conversion process.
Implementation Method 1
the thermal cracking reactions can be initiated and the formation of coke in the furnace tubes be minimised
Implementation Method 2
the thermal cracking and coking or carbonisation reactions are completed. These reactions generate hydrocarbons lighter than those in the combined feedstock and coke
Implementation Method 3
The reactions which take place in a coke drum are endothermic and the temperature of the effluents from the drum lie within a band of values from 425 °C to 455 °C
Data Source
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AI summary
A process of delayed coking with modified feedstock is described maximising the volume of diesel oil and minimising the volume of coke produced by means of feedstock which comprises, in a first embodiment of the invention: the bottom product (8) of the vacuum distillation tower (6), known in the prior art as vacuum residuum, and a fraction (7') of heavy vacuum gas oil (7) obtained in the aforesaid vacuum distillation. In a second embodiment of the present invention the bottom residuum (5) proceeding from the atmospheric distillation tower (2), known in the prior art as atmospheric residuum, is employed as feedstock of a Delayed Coking Unit (9) .