Fischer-Tropsch Reactor Cooling System with Downcomer and Riser
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Solution Overview
Problem
Current Fischer-Tropsch (F-T) slurry reactor designs require complex heat removal systems with multiple zones and elevated drums, increasing capital costs and complexity.
Innovation Solution
A cooling system that uses a downcomer and riser configuration with controlled pressure drops to maintain coolant in a liquid phase, generating backpressure and promoting boiling heat transfer surfaces for enhanced heat removal, optimizing log mean temperature difference and reducing the required surface area for heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional heat removal systems with multiple zones and elevated drums are used, then heat removal capability is achieved, but device complexity and capital costs increase
Solution Approach 1:
The heat removal system is segmented into distinct functional zones: a downcomer region for liquid coolant descent and a riser region for vaporization and heat transfer. This segmentation allows each zone to perform its specific function efficiently, eliminating the need for complex external drum systems while maintaining effective heat removal capability.
Solution Approach 2:
The invention transitions from a traditional horizontal/elevated drum configuration to a vertical arrangement where the downcomer extends downward and the riser extends upward from a plenum. This dimensional change simplifies the overall system structure by utilizing vertical space more effectively and eliminating the need for elevated drums and external piping.
2Temperature
If larger surface area is provided for heat transfer, then heat removal efficiency improves, but capital costs increase
Solution Approach 1:
The system utilizes phase transition of the coolant from liquid to vapor within the riser region to enhance heat transfer. The vaporization process absorbs large amounts of heat efficiently, allowing for reduced surface area compared to systems relying solely on sensible heat transfer, thereby reducing capital costs while maintaining heat removal efficiency.
Solution Approach 2:
The invention employs natural circulation driven by density differences between liquid and vapor phases. The heated vapor rises through the riser while cooler liquid descends through the downcomer, creating a self-sustaining circulation pattern that enhances heat transfer efficiency without requiring additional pumping power or larger heat transfer surfaces.
3Temperature
If coolant velocity is increased, then heat transfer efficiency improves, but pressure drop increases
Solution Approach 1:
The system changes the physical state parameter of the coolant from liquid to vapor-phase mixture in the riser region. This parameter change allows the coolant to achieve higher heat transfer coefficients through phase change heat transfer, which is more efficient than liquid-only heat transfer even at lower velocities, thereby reducing the required pressure drop.
Solution Approach 2:
The downcomer is designed to maintain the coolant in liquid phase through sufficient backpressure, preventing premature vaporization. This preliminary anti-action ensures that vaporization occurs only in the riser region where it is desired, allowing the system to achieve high heat transfer efficiency without excessive pressure drops that would result from uncontrolled vaporization throughout the system.
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 configuration increases heat transfer efficiency, reduces capital costs by minimizing the necessary surface area for heat removal, and simplifies reactor design by eliminating the need for multiple zones and elevated drums.
Implementation Method 1
the diameter of the at least one downcomer and the pressure of the introduced coolant cooperate to increase the coolant velocity thereby generating backpressure in the at least one downcomer to maintain the coolant in the substantially liquid phase
Implementation Method 2
a portion of the coolant vaporizes to provide a boiling heat transfer surface on the at least one riser
Implementation Method 3
a portion of the coolant vaporizes to provide a boiling heat transfer surface
Implementation Method 4
Heat is transferred from the slurry to the cooling medium
Data Source
AI summary
The present invention is directed to a cooling system for removing heat from a Fischer-Tropsch (F-T) slurry reactor. The cooling system including a downcomer disposed within the F-T reactor to deliver a coolant downward through the F-T reactor at a predetermined velocity. The downcomer and the pressure of the introduced coolant cooperate to increase the coolant velocity, thereby maintaining the coolant in the substantially liquid phase in the downcomer. The cooling system further includes a plenum connected to the downcomer, wherein the coolant remains in the substantially liquid phase. Additionally, the cooling system includes at least one riser extending upward from the plenum, wherein a portion of the coolant vaporizes to provide a boiling heat transfer surface on the at least one riser.