Pyrolysis Plastic Oil Hydroprocessing to Prevent Steam-Cracking Fouling
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Solution Overview
Problem
Pyrolysis plastic oil contains impurities such as unsaturated compounds, silicon, halogenated compounds, alkali metals, phosphorous compounds, and iron, which prevent its direct use in processes like steam cracking due to fouling, catalyst poisoning, and corrosion issues.
Innovation Solution
A process involving the use of a high-temperature hydroprocessing method with a second diluent to heat and hydrogenate pyrolysis plastic oil, incorporating a catalyst with both hydrotreatment and trapping functions to remove impurities and unsaturated compounds, while maintaining the reaction in liquid conditions to avoid fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pyrolysis plastic oil is directly used in steam cracking, then the process can proceed without additional treatment steps, but fouling, catalyst poisoning, and corrosion occur due to impurities
Solution Approach 1:
The patent applies preliminary action by performing hydroprocessing treatment on pyrolysis plastic oil before it enters the steam cracking process. This pre-treatment removes impurities such as unsaturated compounds, silicon, halogenated compounds, alkali metals, phosphorous compounds, and iron that would otherwise cause fouling, catalyst poisoning, and corrosion in the steam cracking equipment. The hydroprocessing step is conducted in advance to prepare the oil for subsequent processing without causing equipment damage.
2Manufacturing precision
If high temperature hydroprocessing is used to remove impurities, then purification efficiency improves, but fouling may occur during heating
Solution Approach 1:
The patent uses a diluent as an intermediary substance to heat the pyrolysis plastic oil during hydroprocessing. Instead of directly heating the oil to high temperatures which would cause fouling, the diluent acts as a heat transfer medium that can raise the oil temperature to the required 230-500°C range without causing the same fouling problems. The diluent facilitates the heat transfer process while protecting the system from direct contact between hot surfaces and the impure oil.
Solution Approach 2:
The patent changes the temperature parameter during the hydroprocessing operation, maintaining it within the specific range of 230-500°C. This controlled temperature parameter allows sufficient purification efficiency to remove impurities while avoiding temperatures that would cause excessive fouling. The temperature is carefully managed to achieve the necessary purification without reaching conditions that would promote carbonization and fouling of equipment surfaces.
3Manufacturing precision
If multiple treatment steps are added to purify pyrolysis plastic oil, then impurity removal improves, but process complexity increases
Solution Approach 1:
The patent merges multiple purification functions into a single hydroprocessing step. Instead of using separate treatment units for different impurities, the hydroprocessing reaction simultaneously removes unsaturated compounds through hydrogenation, eliminates silicon, halogenated compounds, alkali metals, phosphorous compounds, and iron through the combined action of catalysts and reaction conditions. This consolidation achieves comprehensive impurity removal while minimizing the number of process steps and equipment required.
Solution Approach 2:
The hydroprocessing unit is designed with multi-functionality to handle various types of impurities present in pyrolysis plastic oil. The catalyst system and reaction conditions are optimized to perform multiple purification functions simultaneously: hydrogenation of unsaturated compounds, removal of heteroatoms, elimination of metals, and prevention of fouling. This universal approach allows a single process step to address all major impurity categories rather than requiring dedicated treatment for each type.
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
The process effectively purifies pyrolysis plastic oil by reducing unsaturated compounds and impurities, enabling its safe use in steam cracking without fouling or catalyst deactivation, thus producing high-quality olefins and aromatics.
Implementation Method 1
A process involving the use of a high-temperature hydroprocessing method with a second diluent to heat and hydrogenate pyrolysis plastic oil, incorporating a catalyst with both hydrotreatment and trapping functions to remove impurities and unsaturated compounds
Implementation Method 2
Pyrolysis converts mixed plastics into gas, liquid oil and solid residue char. The liquid can be further refined for fuel or new plastics production.
Data Source
AI summary
A process for the purification of a hydrocarbon stream including: (a) Providing a hydrocarbon stream having a diene value of at least 1.0 and a bromine number of at least 5 gBr2/100g and containing pyrolysis plastic oil; (b) Optionally contact the hydrocarbon stream obtained in step (a) with a silica gel, clays, alkaline or alkaline earth metal oxide, iron oxide, ion exchange resins, active carbon, active aluminum oxide, molecular sieves, alkaline oxide and/or porous supports and silica gel, or any mixture thereof, (c) Heating the stream obtained in step a) or b) followed by a mixing of the heated stream with a second diluent heated at a temperature of at least 300° C. preferably at least 330° C.; (d) performing an hydroprocessing step at a temperature of at least 250° C. in the presence of H2; and (e) recovering a purified hydrocarbon stream.