Algae Harvesting System for Biofuel Production

Nicole Maas, Stefanie Marikis, Josh Nisson, Chance Scripter, Ryan Walters

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Why Harvest Algae?

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• Algae can produce up to 60X more oil than other oil feedstocks
• 1,600 gallons/acre oil yield
• Almost carbon neutral
• Many different strains Many different growing environments

Mark Hanson, Mary Sennes. The Law of Algae

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Deliverables and Constraints

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1. 15% or less moisture content
2. Energy efficient
3. Retrofit onto existing photobioreactor
4. Recirculation of algae growing water
5. Budget of $3000

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Algae Growth: Mini Photobioreactor

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• First round of growth did not go as planned
• Algae dead when it arrived
• Didn’t let algae acclimate
• Low initial temperature
• Wrong type of light
• Second round appears to be doing better

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General Process

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Photo bioreactor

Dewatering

Dehydration

15% Moisture content algae

Algae Nutrients CO2 Energy

Energy

Energy

Red = Input

Green = Output

Grey = Process

Recyclable water

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Dewatering Methods

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• Large batch centrifuging
• energy intensive on an large scale
• increased maintenance costs for saline environment

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• Fine grade filters
• build up on filter screen

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• Floatation
• contamination
• coupled with filtration

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• Flocculation
• chemical coagulant
• electroflocculation
• coupled with filtration

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Dehydration Methods

• Sun-drying
• inefficient due to high water content of algae

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• Freeze-drying
• energy intensive and expensive large scale

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• Rotary drum drying
• higher moisture content output

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Methods we are testing for our system

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Dewatering methods:

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1. 3-Stage Filter
2. “Sixer” Filter
3. Rotary Drum Filter

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Dehydration Methods:

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1. Vertical Cross Flow Dryer (VCFD)
2. Drum Drier

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Modular Filter Housing Optimization

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• For sieve analysis to determine optimal screen size for removal of algae from water.
• Filters are stacked in series and the stack is filled from the top
• Has progressively finer sieve sizes.
• Printed out of PLA plastic

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Modular Filter Housing Assembly

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Dewatering Technique: 3-Stage Filter

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Filter screen is moved between flows to clear it, preventing filter clogging at the source

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1. Green water is passed through a filter, where algae is collected for a determined period of time
2. Compressed air is blown through to remove standing water from the filter
3. Air is blown from the opposite side to clear algae off the filter and collect it

STAGE 1

STAGE 2

STAGE 3

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Dewatering Technique: “Sixer”

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• Rotates cylinder to introduce a new filter when one is full
• Compressed air purges standing water on “idle” filters that have collected algae
• Cylinder is removed and cleaned when all the filters are full

COMPRESSED AIR

GREEN WATER IN

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Dewatering Technique: Rotary Drum Filter

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• Rotary drum with a screen size optimized from modular filter housing
• Rotation of drum prevents clogging of screen

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Dehydration Technique: Vertical Cross Flow Dryer

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• Separation of algae based on distinct particle surface area and density
• Air is blown upwards through a tube
• Controlled hot dry air flow over algae reduces water density, and thus algae density
• Light, dry algae is blown out while heavier, wet algae stays

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Dehydration Technique: Vertical Cross Flow Dryer: Calculations

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Flowing Air

T=? p=? v=?

Fb=?

m=?

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d=?

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Dehydration Technique: Drum Drier

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• Hot air is blown over algae to reduce moisture content.

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• Drum rotates algae to increase surface area exposure to hot air.

• Ends will be sealed to contain hot air.

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Potential Problems and Solutions

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Fall Semester Schedule

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OCTOBER NOVEMBER DECEMBER

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Spring Semester Schedule

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JANUARY FEBRUARY MARCH APRIL

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Budget

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Current expenses

Remaining funds for prototype

Final design funds

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Questions?

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