Crude Oil Fractionation and Hydrotreating for Flexible Steam Cracking
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Solution Overview
Problem
Conventional refinery configurations are capital and energy intensive, leading to rapid coke formation in steam cracker furnaces, frequent decoke cycles, and reduced yield of valuable chemicals due to vacuum residue's hydrogen deficiency and formation of harmful polynuclear aromatics.
Innovation Solution
A method and system that separates crude oil into light, medium, and heavy fractions, with the medium fraction hydrotreated under low pressure to produce hydrotreated oil, which is then cracked in a steam cracker, and the system includes control mechanisms to switch between max chemicals and chemicals plus fuels modes of operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional refinery units are used to process crude oil, then the various boiling range fractions can be segregated for downstream processing, but the process becomes capital and energy intensive
Solution Approach 1:
The crude oil is separated into three distinct fractions (light oil, medium oil, heavy oil) based on boiling range, allowing each fraction to be processed optimally. The light oil fraction goes directly to steam cracker, the medium oil fraction undergoes hydrotreating, and the heavy oil fraction is handled separately, eliminating the need for conventional complex refinery units and reducing energy consumption.
Solution Approach 2:
The crude oil is pre-separated into boiling range fractions before further processing. This preliminary separation allows the steam cracker to receive only the suitable light oil fraction without requiring complex downstream separation units, and enables the medium oil fraction to be hydrotreated to remove HPNAs before cracking, preventing coke formation.
2Reliability
If vacuum residue is processed without significant formation of heavy polynuclear aromatics, then coke formation in steam cracker furnace is reduced, but conversion of vacuum residue is challenging due to hydrogen deficiency
Solution Approach 1:
The medium oil fraction undergoes hydrotreating before being fed to the steam cracker. This preliminary hydrotreatment removes HPNAs and adds hydrogen to the vacuum residue, preventing rapid coke formation in the steam cracker while improving the hydrogen content and chemical yield. The hydrotreated medium oil fraction can then be cracked with stable long-run operation.
3Productivity
If the process is optimized for maximum chemical production, then chemical yield is maximized, but the ability to produce desirable end products like diesel fuel is eliminated
Solution Approach 1:
The process is designed to be dynamically adjustable between two operating modes. In max chemicals mode, the entire hydrotreated medium oil fraction is fed to the steam cracker for maximum chemical production. In chemicals plus fuels mode, the hydrotreated medium oil fraction is separated to recover diesel fuel and jet fuel fractions, with only the remaining light and heavy fractions fed to the steam cracker. This dynamic flexibility allows adaptation to market demands.
Solution Approach 2:
The hydrotreated medium oil fraction serves multiple functions: it can be entirely fed to the steam cracker for chemical production, or it can be separated to produce both fuel products (diesel, jet fuel) and chemical feedstocks (light and heavy fractions). This multi-functionality enables the same processing unit to serve different market needs without requiring separate dedicated facilities.
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
Enhances production of valuable chemicals and fuels like ultra-low sulfur diesel while maintaining reasonable decoke frequency and flexibility to adapt to market demands.
Implementation Method 1
feeding the light oil fraction to a steam cracker to crack hydrocarbons in the light oil to form a cracked light oil
Implementation Method 2
The medium oil fraction is distillate hydrotreated under low pressure conditions to produce a hydrotreated medium oil fraction
Data Source
AI summary
Systems and methods for flexibly converting crude oil to chemicals and fuels. The systems include unit operations configured to provide flexibility between operating in two different modes for two periods of time. A method includes separating a crude oil, distillate hydrotreating a medium oil fraction resulting from the separation, and operating in a max chemicals mode of operation for a first period of time and in a chemicals plus fuels mode for a second period of time. The method may further include conditioning and hydroprocessing, collectively separating, recovering an unconverted oil fraction, and feeding a light oil fraction, first hydrocarbon fraction, and a diesel fuel fraction or jet fuel fraction to a steam cracker. The system includes a separation unit, a low pressure distillate hydrotreating unit, a separation unit, a steam cracker unit, a separation system, a flow system, and a control system.