Delayed Coking Pre-Cracking Reactor for Coke Yield Reduction
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Solution Overview
Problem
The delayed coking process produces a high yield of low-value coke, which reduces the overall efficiency and margin of coking operations, and existing additive-based solutions are costly and may affect the quality of products.
Innovation Solution
A method involving mild and severe thermal cracking reactions in a pre-cracking reactor and coke drums, respectively, to optimize the yield of desired products without external additives, using a plug flow reactor and controlling temperature and pressure to minimize coke formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If delayed coking process is used to convert heavy residue into lighter fractions, then conversion of heavy residue is achieved, but high yield of low-value coke is produced reducing overall efficiency
Solution Approach 1:
The coking process is divided into two distinct stages: a pre-cracking reactor stage that performs initial thermal cracking at controlled conditions, and a main coking drum stage that completes the coking process. This segmentation allows optimization of each stage independently to reduce overall coke yield while maintaining conversion efficiency.
Solution Approach 2:
Mild thermal cracking reactions are performed in the pre-cracking reactor before the main coking process in the coke drum. This preliminary action breaks down heavy molecules into smaller units that are more difficult to coke, thereby reducing the amount of coke formed in the subsequent main coking stage.
2Productivity
If higher temperatures are used in coking heater, then coking rate increases, but rapid coking in heater causes shortened on-stream time
Solution Approach 1:
The heating and cracking process is segmented into two zones: the coking heater that provides controlled heating to cracking temperature, and the coke drum that completes the cracking process. This allows the heater to operate at lower temperatures for longer periods without causing rapid coking, while still achieving high overall coking rates.
Solution Approach 2:
The pre-cracking reactor performs preliminary thermal cracking at controlled temperatures before the main coking process. This preliminary action reduces the thermal burden on the coking heater, allowing it to operate at lower temperatures for extended periods without causing rapid coke formation that would shorten on-stream time.
3Productivity
If lower temperatures are used in coking heater, then coking rate decreases, but soft coke with high VCM content is produced
Solution Approach 1:
The thermal cracking process is segmented into a pre-cracking stage at controlled temperatures and a main coking stage at higher temperatures. This allows the pre-cracking reactor to operate at lower temperatures without producing soft coke, while the main coking drum completes the process at temperatures that produce high-quality coke.
Solution Approach 2:
The pre-cracking reactor performs preliminary thermal cracking at controlled temperatures to break down heavy molecules before the main coking process. This preliminary action prepares the feedstock for more efficient coking at higher temperatures in the main drum, avoiding the production of soft coke while maintaining high coking rates.
4Reliability
If water or steam injection is used to control velocity in heating coil, then coke deposition in coil is prevented, but additional control complexity is introduced
Solution Approach 1:
The function of controlling coke deposition is extracted from the coking heater and transferred to the pre-cracking reactor. By performing thermal cracking in the pre-cracking reactor before the main coking process, the heater is protected from coke deposition without requiring complex water or steam injection control systems.
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 reduces the overall coke yield, improving the efficiency of processing heavy petroleum residues and increasing the yield of lighter products like fuel gas, LPG, and naphtha, while maintaining product quality.
Implementation Method 1
introducing the hot feed (61) of step (a) in a pre-cracking reactor (4, 23, 24, 43, 62) wherein it undergoes mild thermal cracking reactions to obtain an outlet product material stream (5, 25, 44, 63)
Implementation Method 2
transferring the hot hydrocarbon stream (10, 30, 50, 66) to preheated coke drums (11, 31, 51, 67) where it undergoes severe thermal cracking reactions to obtain product vapors (12, 32, 52, 68)
Implementation Method 3
heating a hydrocarbon feedstock (1, 20, 40, 59) in a reactor furnace (2, 21, 41, 60) to obtain hot feed (3, 22, 42, 61)
Implementation Method 4
heating the heavy bottom fraction (64) or the heavy bottom (8, 28, 47) of step (c) in a secondary furnace (9, 29, 49, 65) to obtain hot hydrocarbon stream (10, 30, 50, 66)
Data Source
AI summary
The present invention relates to delayed coking of heavy petroleum residue producing petroleum coke and lighter hydrocarbon products. The invented process utilize a pre-cracking reactor and a reactor furnace for mild thermal cracking of the feedstock and an intermediate separator, before being subjected to higher severity thermal cracking treatment in a coker furnace and a coking drums, resulting in reduction in overall coke yield.