Heavy Oil Hydroconversion in Solid Accumulation Reactor
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Solution Overview
Problem
Current hydroconversion processes for heavy oils face challenges in achieving total conversion due to incomplete conversion in single reactor passages, leading to non-converted feedstock recycling issues, catalyst deactivation, and complex separation and recycling processes, especially with the formation of coke and solids accumulation.
Innovation Solution
A high-severity hydrotreatment process using a molybdenum-based hydrogenation catalyst in a solid accumulation reactor of the bubble tower type, where hydrogen acts as a fluid-dynamic kinetic vector to ensure homogeneous stirring and direct removal of solids and conversion products in the gaseous phase, eliminating the need for separate recycling sections and maintaining catalyst activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heavy oil is sent to a high-severity hydrotreatment step in a bubble tower reactor with solid accumulation, then complete conversion to vapour phase products is achieved, but the reactor operates with high concentrations of solids and coke accumulation
Solution Approach 1:
The patent converts the harmful effect of coke and solids accumulation into a beneficial fluidization mechanism. The accumulated solids and coke act as a fluidizing medium that enhances mixing and heat transfer, while the continuous hydrogen flow prevents excessive accumulation and maintains catalyst activity. This transforms what would normally be a deactivating factor into a functional advantage for complete conversion.
Solution Approach 2:
The patent operates under specific parameter conditions: high temperature (400-480°C), high pressure (100-200 atm), and high hydrogen flow rates. These parameter changes enable the reactor to tolerate and even utilize high solids concentrations while maintaining complete conversion. The hydrogen partial pressure and flow rate are specifically controlled to prevent excessive coke deposition while achieving total conversion.
2Productivity
If non-converted asphaltene residue is recycled to the reaction, then conversion completeness is improved, but the process complexity and equipment requirements increase
Solution Approach 1:
The patent extracts the conversion products directly in the vapour phase from the reactor outlet, separating them from the solid catalyst and unconverted residue. This extraction of products in vapour form eliminates the need for complex liquid-vapour separation systems and recycling pumps, while still achieving complete conversion by maintaining appropriate residence time and reaction conditions.
Solution Approach 2:
The bubble tower reactor performs multiple functions simultaneously: it serves as the reaction vessel, the vapour-liquid separator, and the solids retention system. The hydrogen gas flow serves both as a reactant and as a fluidizing agent that prevents solids accumulation. This multi-functionality reduces the number of separate equipment units needed compared to conventional two-stage systems.
3Reliability
If the liquid phase is maintained in hydrogen atmosphere to prevent coke formation, then catalyst activity is preserved, but high-boiling product recovery is limited
Solution Approach 1:
The patent utilizes phase transition by allowing conversion products to vaporize directly from the reaction zone. The high temperature conditions cause products to transition from liquid to vapour phase, where they are carried out by the hydrogen flow. This phase change enables complete conversion without requiring the liquid phase to be maintained under hydrogen atmosphere, thus recovering all product fractions including high-boiling components.
4Device complexity
If catalyst and non-converted residue are constantly maintained inside the reactor, then plant complexity is reduced, but solids accumulation may affect reactor operation
Solution Approach 1:
The patent maintains continuous hydrogen flow through the reactor, which continuously fluidizes the solid catalyst and prevents excessive solids accumulation. This continuous action of hydrogen serves both as a reactant and as a cleaning mechanism that prevents deactivating coke layers from forming on the catalyst, ensuring long-term stable operation with the catalyst remaining in the reactor.
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 allows for stable operation under high-solid concentrations, achieving complete conversion of heavy oils to vapour phase products within the reactor, simplifying the process and reducing catalyst deactivation, while minimizing flushing requirements and maintaining high productivity.
Implementation Method 1
hydrogen acts as a fluid-dynamic kinetic vector and as a carrier of the conversion products... introducing hydrogen or a mixture of hydrogen and H2S... the hydrogen... ensures, through induced stirring, a high homogeneity of the reaction mass
Implementation Method 2
hydrogen acts as a fluid-dynamic kinetic vector and as a carrier of the conversion products... operating with the accumulation of coke and metallic sulphides, obtaining the conversion products as outflow of the vapour phase directly in the reactor
Implementation Method 3
sending the heavy oil to a high-severity hydrotreatment step, in the presence of a hydrogenation catalyst based on molybdenum in slurry phase
Implementation Method 4
effected in a reactor of the bubble tower type... operating under such conditions as to obtain conversion products in vapour phase directly in the reactor
Data Source
AI summary
A process for the conversion of heavy oils comprising sending the heavy oil to hydrotreatment, of the high severity type, in the presence of high concentrations of a suitable hydrogenation catalyst dispersed in slurry phase, effected in a suitable solid accumulation reactor capable of operating stably in the presence of solids deriving from and generated by the feedstock charged, wherein the hydrogen or mixtures thereof is fed at suitable flow-rates and suitably distributed, obtaining the conversion products in vapour phase directly in the reactor.