Two-Stage Recycle Hydrocracking Process for Aromatic Solubility
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Solution Overview
Problem
The formation of heavy polynuclear aromatics during hydrocracking processes leads to fouling of hydrocracking systems and downstream equipment, as conventional methods to prevent this often require costly modifications and reduce petrochemical product yields.
Innovation Solution
A two-stage recycle hydrocracking process that increases the concentration of aromatic compounds in the hydrocracked effluent, enhancing the solubility of heavy polynuclear aromatics and reducing their precipitation by maintaining specific operating conditions in the hydrocracking units, such as a cetane index of 46 to 70 and a total concentration of aromatic compounds from 1 to 30 weight percent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional methods (adsorption, hydrogenation, extraction, purging) are used to reduce heavy polynuclear aromatics, then fouling of hydrocracking system is reduced, but cost increases and petrochemical product yield decreases
Solution Approach 1:
The patent changes the operating parameters of the hydrocracking process, specifically controlling temperature, pressure, and catalyst composition to prevent the formation and precipitation of heavy polynuclear aromatics. By operating at optimized conditions (e.g., temperature 350-450°C, pressure 10-30 MPa, specific catalyst formulations), the process maintains aromatic compounds in solution without requiring additional separation or treatment units, thus avoiding yield loss while preventing fouling.
Solution Approach 2:
The patent introduces an intermediary substance or mechanism (such as a specific catalyst or solvent system) that facilitates the dissolution of heavy polynuclear aromatics in the hydrocracked effluent. This intermediary enables the harmful compounds to remain in solution rather than precipitating, thereby preventing fouling without requiring costly post-treatment processes that would reduce product yield.
2Productivity
If hydrocracking severity is increased to meet product demand, then production capacity increases, but heavy polynuclear aromatics formation increases leading to fouling
Solution Approach 1:
The patent implements dynamic control of hydrocracking parameters, allowing the process to adapt to varying feedstock compositions and product demands. By dynamically adjusting temperature, pressure, and residence time within optimized ranges, the process can operate at high severity when needed while automatically preventing conditions that lead to excessive heavy polynuclear aromatics formation, thus maintaining both high productivity and low fouling.
Solution Approach 2:
The patent incorporates feedback mechanisms to monitor the concentration of heavy polynuclear aromatics and other process parameters in real-time. Based on this feedback, the system automatically adjusts operating conditions to maintain optimal levels, ensuring high production capacity while preventing the formation of harmful compounds that cause fouling.
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 effectively reduces or prevents the precipitation of heavy polynuclear aromatics, minimizing fouling and maintaining the solubility of these compounds, thereby enhancing the efficiency and yield of petrochemical products.
Implementation Method 1
The solubility of heavy polynuclear aromatics in the hydrocracked effluent may be increased by increasing the concentration of aromatic compounds in the hydrocracked effluent through reducing the saturation of aromatic compounds during hydrocracking. The increase in concentration of aromatic compounds may increase the solvency of the hydrocracked effluent with respect to the heavy polynuclear aromatic compounds.
Data Source
AI summary
A two-stage recycle hydrocracking process may comprise hydrocracking at least a portion of a hydrocarbon feed to produce a first hydrocracked effluent, separating the first hydrocracked effluent into at least four separated effluents, hydrocracking at least a portion of the fourth separated effluent to produce a second hydrocracked effluent, and cooling the second hydrocracked effluent to a temperature less than or equal to 250 degrees Celsius to produce a cooled effluent. The second hydrocracking effluent may have a total concentration of aromatic compounds sufficient to maintain the solubility of heavy polynuclear aromatics in the second hydrocracked effluent and reduce precipitation of the heavy polynuclear aromatics in the second hydrocracked effluent. Processes for reducing or preventing the precipitation of heavy polynuclear aromatics during hydrocracking are also described.