Pivot Arm Mixing for Algae Bioreactor Mass Transfer
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Solution Overview
Problem
Conventional raceway ponds for algae cultivation face limitations in light distribution uniformity and mass transfer rates, which restrict the scale and efficiency of biofuel production, particularly for high-productivity algae strains, due to energy-intensive water circulation and inertia of large machinery.
Innovation Solution
A system with a pivot arm and mixing device that rotates within the pond to induce localized and bulk water circulation, improving light distribution and mass transfer rates while minimizing unnecessary water flow, using a sparging device to deliver gases and a skimming trough for algae harvesting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If paddle wheels or pumps are increased in size or number to improve mass transfer rates, then mass transfer rate is improved, but device complexity and capital cost increase
Solution Approach 1:
The patent applies dynamics by using a movable mixing device that travels along the pond perimeter rather than stationary paddle wheels. The mixing device is positioned on a movable platform that can traverse the pond, allowing flexible adjustment of mixing location and intensity. This dynamic approach replaces fixed, bulky machinery with a mobile system that achieves similar or better mixing efficiency with reduced capital investment and lower device complexity.
2Productivity
If water circulation velocity is increased to improve mass transfer rates, then mass transfer rate is improved, but energy consumption increases
Solution Approach 1:
The patent applies local quality by concentrating mixing activity at specific locations along the pond perimeter rather than circulating entire pond volumes. The movable mixing device creates localized high-velocity mixing zones where mass transfer is most needed at the gas-liquid interface, while leaving other pond regions in natural circulation. This targeted approach achieves high mass transfer rates with minimal energy input compared to whole-pond circulation systems.
Solution Approach 2:
The patent uses a sparging device that travels along the pond perimeter, creating multiple localized mixing zones as it moves. This mobile sparging system copies the beneficial effects of high-velocity mixing at different locations throughout the pond over time, achieving comprehensive gas-liquid mass transfer without requiring continuous high-velocity circulation of the entire pond volume, thus reducing overall energy consumption.
3Device complexity
If conventional raceway ponds are used for algae cultivation, then simplicity of design is maintained, but light distribution uniformity deteriorates
Solution Approach 1:
The patent improves light distribution uniformity through dynamic movement of the sparging and mixing devices along the pond perimeter. As these devices traverse different locations, they create varying circulation patterns that continuously redistribute algae cells throughout the water column, preventing prolonged exposure of surface algae to excessive light and ensuring more uniform light penetration to deeper layers. This dynamic redistribution achieves better light uniformity while maintaining relatively simple pond infrastructure.
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 enhances light distribution and mass transfer rates, supporting higher productivity algae strains with reduced energy consumption and operational costs, enabling larger-scale, efficient biofuel production.
Implementation Method 1
The sparging device is configured to deliver a gas, such as carbon dioxide, air, or another gas containing carbon, to the water and the algae
Implementation Method 2
a mixing device coupled to the pivot arm and extending into the pond to mix the water and the algae as the pivot arm rotates
Data Source
AI summary
A system for growing algae includes a pivot arm pivotally coupled to a pivot connection positioned in a pond containing water and algae, and a mixing device coupled to the pivot arm and extending into the pond to mix the water and the algae as the pivot arm rotates.