Reactor Downcomer Helical Flow Gas Separation
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Solution Overview
Problem
The presence of hydrogen bubbles in the multi-phase mixture within the downcomer of a reactor for upgrading heavy hydrocarbons hinders the downward flow, necessitating a method to reduce bubble content and enhance gas separation.
Innovation Solution
Increasing the residence time of the multi-phase mixture within a frusto-conical degassing section by directing it in a downward helical flow, which causes denser components to be centrifugally urged outward and less dense bubbles to coalesce into larger bubbles with higher ascension velocity, facilitated by baffles to maximize bubble escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the multi-phase mixture flows through a conventional degassing section, then the gas bubbles escape relatively quickly, but the residence time is insufficient to maximize bubble separation and coalescence
Solution Approach 1:
The degassing section employs a frusto-conical geometry with a curved inner surface that directs the multi-phase mixture in a helical downward flow pattern. This curved geometry extends the residence time by forcing the mixture to follow a longer, more tortuous path while the helical motion promotes centrifugal separation of bubbles from the liquid stream, maximizing bubble coalescence and escape without compromising productivity.
Solution Approach 2:
The invention introduces helical (three-dimensional) flow motion rather than simple vertical or radial flow. By configuring the mixture to travel along the conical surface in a helical direction, the system adds a rotational dimension to the flow, increasing the path length and residence time while simultaneously enhancing the centrifugal forces that drive bubble separation and coalescence.
2Ease of operation
If hydrogen bubbles are present in the multi-phase mixture, then the natural ascension velocity of bubbles is high, but the bubbles inhibit the downward flow of the mixture
Solution Approach 1:
The helical flow configuration generates centrifugal forces that act opposite to the buoyant force on the bubbles. By rotating the flow path around the conical axis, the centrifugal force pushes denser liquid components outward while forcing lighter gas bubbles inward toward the axis, effectively counteracting the bubbles' natural upward motion and enabling their removal from the downward-flowing mixture.
Solution Approach 2:
The invention converts the harmful effect of bubble presence (inhibition of downward flow) into a beneficial separation process. The helical flow path and centrifugal forces cause bubbles to migrate to the center axis where they coalesce and escape, transforming the problem of bubble interference into an effective gas-liquid separation mechanism that cleans the liquid stream.
3Speed
If the degassing section has a large diameter, then the multi-phase mixture travels slower facilitating bubble escape, but the residence time is reduced
Solution Approach 1:
The frusto-conical geometry with its curved inner surface creates a helical flow path that extends the residence time. Even though the cross-sectional area is large, the curved surface forces the mixture to follow a longer, more extended path, increasing the time available for bubble separation while maintaining slower overall flow velocity that facilitates bubble escape.
Solution Approach 2:
By introducing helical motion in three dimensions rather than simple linear flow, the system increases the effective path length significantly. The mixture travels along the conical surface in a spiral pattern, adding a rotational component that extends residence time without requiring a proportionally longer linear distance, thus maintaining slower velocity while increasing contact time.
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 bubble content, thereby minimizing resistance to the downward flow of the multi-phase mixture and improving gas separation, leading to a more efficient operation of the reactor.
Implementation Method 1
flowing the multi-phase mixture along a generally frusto-conical surface of the degassing section in a generally downwardly helical direction. Denser components of the mixture are centrifugally urged outwardly away from a center axis of the surface, and less dense components (e.g., gas) bubbles migrate toward the center axis.
Implementation Method 2
flowing the multi-phase mixture along a generally frusto-conical surface of the degassing section in a generally downwardly helical direction
Implementation Method 3
Small gas bubbles can then coalesce into larger bubbles which have a greater inherent tendency to rise
Implementation Method 4
A flow of liquefied slurry and residual hydrogen gas is recirculated within the chamber through a vertically oriented downcomer in the chamber. Such a multi-phase mixture enters an upper end of the downcomer, for example, under the action of a recirculation pump.
Implementation Method 5
the hydrogen to react with, and hydrogenate, the hydrocarbons
Data Source
AI summary
In an upflow reactor for reacting heavy hydrocarbons with hydrogen gas in a liquefied catalyst slurry, that mixture is recirculated down through a downcomer having an upper degassing section which includes a frusto-conical upper surface. The mixture is caused to flow along that surface in a downward helical path, such that heavier components are centrifugally urged outwardly, and lighter components, e.g., gas, migrate inwardly. The gas bubbles can thus coalesce such that small bubbles become bigger bubbles having a greater tendency to rise out of the downcomer. Baffles placed on the upper surface can maximize the residence time of the mixture in the degassing section.