CO2 Effluent Treatment via Segmented Precipitation
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Solution Overview
Problem
The direct addition of CO2 to highly basic effluents laden with metals, such as aluminum, leads to instantaneous and difficult-to-control precipitation, causing frequent blockages in injection systems and reducing the performance of treatment installations.
Innovation Solution
The process is divided into two distinct phases: the first phase generates aluminum hydroxide crystals in a low-pH environment without direct CO2 injection, and the second phase optimizes CO2 dissolution in a recirculation loop, allowing for controlled acidification and minimizing precipitation in the injection zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CO2 is directly injected into highly basic effluents to neutralize and precipitate metals, then the neutralization and metal removal efficiency is improved, but the injection systems become blocked due to instantaneous precipitation of solids near injection points
Solution Approach 1:
The treatment process is divided into two separate stages: a first stage for CO2 dissolution where carbonated water is produced, and a second stage for effluent neutralization where the carbonated water is injected. This segmentation prevents precipitation in the injection system by separating the dissolution function from the neutralization function, allowing each stage to operate under optimal conditions without causing blockages.
2Productivity
If CO2 is directly injected to cause instantaneous precipitation, then metal removal is achieved, but the precipitation becomes difficult to control and causes blockages in conduits and injection points
Solution Approach 1:
CO2 is preliminarily dissolved in water under controlled conditions in a dissolution stage before the neutralization process. This preliminary dissolution creates a buffered carbonated water solution that can neutralize effluents gradually and controllably, preventing instantaneous precipitation and allowing better control over the precipitation process in the second stage.
3Productivity
If a great amount of acid (CO2) is added to bring about precipitation, then aluminum removal is effective, but the injection zone rapidly produces precipitates causing blockages
Solution Approach 1:
Carbonated water acts as an intermediary medium between CO2 gas and the effluent. Instead of directly injecting large amounts of CO2 gas into the effluent (which causes rapid precipitation and blockages), the CO2 is first dissolved in water to create a buffered solution. This intermediary carbonated water then neutralizes the effluent more gradually, reducing precipitate formation in the injection zone while maintaining effective aluminum removal.
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 controlled pH management, maximizing CO2 utilization, and preventing blockages, thereby ensuring efficient treatment and reduced operational costs.
Implementation Method 1
the dissolution of the CO2 and the operation of bringing it into contact with the effluent laden with electrolytes
Implementation Method 2
CO2, like any strong acid, brings about a high concentration of acid at the place of the injection
Implementation Method 3
the formation of solid aluminum hydroxides is very great and the risk of plugging of the injection point is then very high
Data Source
AI summary
A method for treatment of an industrial effluent with aluminum, comprising:the effluent to be treated is carried to a first zone constituted by a tank having a pH of less than 9.5, so as to promote precipitation of the aluminum in aluminum hydroxide form and to facilitate its removal;a second zone is available and the recirculation of a part of a medium located in the zone 1 to the zone 2 and then return to the zone 1, and the injection of gaseous CO2 into the recirculated medium, are arranged;the solid particles formed in the zone 1 are separated and discharged; wherein in view of the recirculation of the medium where CO2 has been injected, the amount of dissolved CO2 available in the zone 1 is 0.5 to 3 times greater than the requirement necessary for the precipitation of the incoming effluent.