Distributed Pot Suction for Aluminum Electrolysis
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Solution Overview
Problem
Current aluminum electrolysis cells face challenges in efficiently collecting and processing CO2 due to its low concentration in the process gas, which is less than 1%, making CO2 sequestration both challenging and expensive, and existing solutions are limited by the design of gas collection systems that introduce 'false air' and reduce the energy recovery efficiency.
Innovation Solution
The Distributed Pot Suction (DPS) system integrates a collection cap with dual inlets above the gas evolving area, allowing for increased suction and temperature of the collected gas, reducing 'false air' and enhancing CO2 concentration, enabling efficient CO2 capture and heat recovery by positioning the suction points closer to the alumina feeding area and using a point feeder system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard suction design with multiple suction points along main gas ducts is used, then all effluents are captured and cell is cooled properly, but large quantities of false air are sucked in through gaps and joints, diluting the process gas and reducing CO2 concentration
Solution Approach 1:
The gas collection system is segmented into multiple independent suction points distributed along the gas ducts, each capable of capturing effluents from specific areas. This segmentation allows targeted collection of process gas while minimizing intake of false air through gaps and joints, thereby maintaining CO2 concentration while ensuring complete effluent capture.
Solution Approach 2:
Each suction point is positioned at specific locations along the gas ducts where effluent generation is highest. By localizing suction points to these critical areas, the system maximizes capture of process gas with high CO2 concentration while avoiding unnecessary intake of false air from other regions, thus improving the CO2 concentration in the collected gas stream.
2Quantity of substance
If suction points are positioned closer to the top crust above gas evolving area, then CO2 concentration in collected gas increases, but gas temperature decreases making heat recovery less efficient
Solution Approach 1:
The system dynamically adjusts suction point positions and operational parameters based on process conditions. By making the suction configuration adaptable, the system can optimize between CO2 concentration and gas temperature depending on operational requirements, enabling both high concentration collection and efficient heat recovery when conditions permit.
Solution Approach 2:
The invention introduces a vertical dimension to gas collection by positioning suction points at different heights and depths relative to the top crust. This three-dimensional arrangement allows the system to capture gas at multiple levels, achieving both high CO2 concentration through localized suction and maintenance of sufficient gas temperature for heat recovery by optimizing the vertical distribution of suction points.
3Stress or pressure
If large quantities of false air are sucked through gaps into the gas suction system, then negative pressure is maintained inside superstructure, but the collected gas is strongly diluted and CO2 sequestration becomes expensive
Solution Approach 1:
The system extracts and removes false air from the gas collection path by positioning suction points to selectively capture process gas directly from the gas evolving area. This extraction of false air minimizes its mixing with process gas, thereby maintaining negative pressure in the superstructure while preserving high CO2 concentration in the collected gas stream for cost-effective sequestration.
Solution Approach 2:
The system changes the pressure distribution and gas flow parameters by optimizing suction point positions and airflow dynamics. This parameter optimization allows maintenance of necessary negative pressure to prevent flue gas leakage while minimizing false air intake, thereby preserving CO2 concentration and reducing sequestration costs.
4Reliability
If distributed pot suction with multiple suction points is used, then effluent capture is improved, but device complexity and number of components increases
Solution Approach 1:
The gas collection system is designed with multi-functional suction points that can capture different types of effluents (HF, SO2, CO2) simultaneously. Each suction point serves multiple purposes: collecting process gas, maintaining negative pressure, and enabling heat recovery. This multi-functionality reduces the need for separate dedicated components for each function, thereby reducing overall device complexity while maintaining high effluent capture efficiency.
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 increases the CO2 concentration in the collected gas, making it suitable for standard CO2 capture technologies and enhances heat recovery by collecting hotter, more concentrated process gases, reducing the volume of gas treated and pressure drop, thus improving energy recovery and reducing the need for extensive maintenance.
Implementation Method 1
a gas evacuating system that generates suction flow
Data Source
Figure 1~2
Figure 3~4
Figure 5a~5b
AI summary
An electrolysis cell producing metals needs to add an accurate amount of feed stock (like alumina) to the cell, and as an effect of the reaction taking place in the cell, one needs to extract the product (like aluminium) and remove any waste product (like HF and CO2). In order to cool the cell properly and to ensure collection of all the effluents from the cell, which is not gas tight, a normal suction is about 100-150 times more ambient air than gas volume produced by the cell. The present invention relates to the principles of how one can extract a more CO2- concentrated flue gas from the cell than is standard procedure in the aluminium industry today, by means of distributed pot suction (DPS) devices. In one embodiment the DPS can be integrated with a feeder having a breaker bar for feeding raw material to the cell. Heat energy can be extracted from the hot flue gas.