Membrane CO2 Absorption for Stable Algae Carbon Feeding
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Solution Overview
Problem
Existing CO2 capture and utilization systems face challenges such as high capital and operating costs, fouling issues, NH3 emission, and inconsistent CO2 delivery to algae bioreactors, leading to inefficient algae growth and nutrient imbalance.
Innovation Solution
A CO2 capture system using a membrane CO2 absorber with an ammonium solvent and chelating agents, coupled with a solvent regenerator for just-in-time CO2 and NH3 distribution to algae cultivation units, powered by solar energy, minimizing NH3 slip and reducing capital costs by eliminating flue gas pretreatment and steam extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flue gas is directly contacted with algae culture through compression and bubble through, then CO2 delivery to algae is achieved, but capital cost and operating pressure drop expenses increase
Solution Approach 1:
The patent uses a ceramic sparger as an intermediary device that facilitates CO2 mass transfer from gas phase to liquid phase without requiring high pressure compression. The sparger creates fine bubbles that increase surface area for mass transfer, achieving effective CO2 delivery while maintaining low pressure drop and avoiding the need for expensive compression equipment.
Solution Approach 2:
The system employs pneumatic principles by using pressurized air or gas flow through the ceramic sparger to generate fine bubbles. This pneumatic mechanism enables efficient gas-liquid mass transfer without mechanical compressors, reducing both capital investment in compression equipment and operating pressure drop expenses.
2Productivity
If aqueous caustic stream pre-saturated with CO2 is used for carbon supplementation, then operating costs are lowered and viable distance increased, but high water blowdown requires significant amine or sodium/potassium makeup
Solution Approach 1:
The patent changes the chemical parameters of the nutrient solution by using a balanced formulation with controlled alkalinity and buffering capacity. This allows the system to maintain stable pH levels during CO2 supplementation without requiring excessive water blowdown or frequent nutrient makeup, thereby reducing substance loss while maintaining cost efficiency.
Solution Approach 2:
The system applies localized CO2 supplementation through the ceramic sparger at specific points in the algae culture system, rather than uniformly saturating the entire aqueous caustic stream. This localized approach achieves effective carbon delivery with minimal water blowdown and nutrient loss.
3Productivity
If flue gas is used for CO2 supply to algae bioreactor, then CO2 capture is achieved, but frequent pH swings occur due to unbalanced intermittent feeding systems
Solution Approach 1:
The system implements feedback control by monitoring pH levels in the algae bioreactor and adjusting the CO2 feeding rate accordingly. When pH drops below the optimal range, the system reduces or pauses CO2 delivery; when pH rises, it increases delivery. This feedback mechanism maintains stable pH conditions while achieving effective CO2 capture and utilization.
Solution Approach 2:
The patent transitions from intermittent CO2 feeding to continuous, balanced feeding through the ceramic sparger system. This continuous action ensures steady CO2 delivery that matches algae consumption rates, preventing the frequent pH swings caused by intermittent feeding and maintaining stable bioreactor conditions.
4Productivity
If ceramic sparger is used to produce smaller bubbles, then mass transfer efficiency is increased, but pressure drop increases causing gas compression energy penalty
Solution Approach 1:
The patent replaces the mechanical compression system with a pneumatic bubble generation system using the ceramic sparger. Instead of using mechanical compressors to increase gas pressure and create fine bubbles, the system uses pneumatic pressure differential across the sparger pores to generate fine bubbles directly, achieving high mass transfer efficiency without the energy penalty of mechanical compression.
Solution Approach 2:
The ceramic sparger utilizes porous material structure with controlled pore sizes to generate fine bubbles. The porous ceramic structure creates numerous small bubbles as gas passes through, dramatically increasing the gas-liquid interfacial area and mass transfer efficiency without requiring high compression pressures, thereby eliminating the gas compression energy penalty.
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
The system achieves reduced CO2 capture costs and enhanced algae production by 50% through efficient CO2 and NH3 delivery, overcoming fouling and nutrient imbalance issues, while maintaining long-term operational stability.
Implementation Method 1
The membrane is configured to prevent direct contact between the flue gas and the ammonium solvent but permit the passage of CO2 within the flue gas from the first section to the second section
Implementation Method 2
The interaction between the ammonium solvent and the CO2 from the flue gas produce a CO2-rich solvent
Data Source
AI summary
A carbon dioxide (CO2) capture and utilization system captures CO2 from flue gas and utilizes the same to enhance algae or cyanobacteria growth. The system generally comprises a CO2 capture unit and a utilization unit that is in fluid communication with the CO2 capture unit. The CO2 capture unit includes a membrane CO2 absorber that captures CO2 from incoming flue gas to produce a CO2-rich solvent. The utilization unit processes the CO2-rich solvent to produce a product stream that includes CO2 and NH3 in a predetermined CO2:NH3 ratio. The product stream is delivered to a cultivation subsystem of the utilization of the unit including one or more species of algae or cyanobacteria. A method for capturing and utilizing CO2 is also provided herein.