Plug Flow Digester
www.PlugFlowDigester.com


Plug Flow Digester

Anaerobic Digesters  *  Biogas Plants  *  Biogas Processing  Biomethane  *  Gas Dehydration  Gas Sweetening

H2S Removal  Landfill Gas to Energy  Pipeline Quality Gas  *  Sewage Sludge  *  Wastewater Treatment




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Plug Flow Digester
www.PlugFlowDigester.com


What is a
plug flow digester?

A plug flow digester is one of the primary types of anaerobic digesters that handle greater amounts of solids than both a covered lagoon and a complete mix digester. A plug flow digester is nearly identical as a complete mix digester with  manure entering the digester which in turn, displaces digester volume, thereby causing an equal amount of material to exit from the digester. The difference with the plug flow digester is that the manure/contents within the plug flow digester are thick enough to keep particles from settling to the bottom of the tank.  

Plug flow digesters do not require mechanical mixing as in other types of digesters such as the complete mix digester.

Total solids content of manure in a plug flow digester should be at least 15% to as high as 20%. 

Plug flow digesters are typically five times longer than they are wide. 

Hydraulic retention times are generally in the 15 days to 21 day time-frame.

Diagram of a plug flow digester.

 

Plug flow digesters have long, narrow concrete tanks with either a rigid or flexible 
cover. The plug flow digester (tank) is built partially or fully below grade to limit 
the demand for requiring additional heating. Plug flow digesters are used only at 
dairy operations that collect manure by scraping.

More information on Anaerobic Digesters can be found at:

www.AnaerobicDigester.com


Plug Flow Digester

Anaerobic Digester  *  Biogas Plants  *  Biogas Processing  Biomethane  *  Gas Dehydration  Gas Sweetening

H2S Removal  Landfill Gas to Energy  Pipeline Quality Gas  *  Sewage Sludge  *  Wastewater Treatment




info@PlugFlowDigester.com

 

 




 



 

 


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What is an Anaerobic Digester?

An anaerobic digester is a system that takes an organic waste stream and through the process of anaerobic digestion (meaning without oxygen), microorganisms break-down the waste stream which generates biogas in the process.  The biogas cannot be used due to the large amount of impurities it contains, so the biogas must cleaned through a biogas to biomethane process after which, the clean biomethane, often referred to as "renewable natural gas" is used just as natural gas, methane or CH4.

The right anaerobic digester and "feedstock" are critical components to optimum production of biomethane which can fuel your own cogeneration or trigeneration power plant.


Anaerobic Digesters
: Different types for different applications


Basic Types of
Anaerobic Digesters

While there are many different types of anaerobic digesters, three designs (below) are the most common found in the U.S., which are:

1.  Anaerobic Lagoons
2.  Plug Flow Digesters
3.  Complete Mix Digesters

with more information, pictures and diagrams found below:

Anaerobic Lagoons

Diagram of a covered lagoon system.

More info at:  www.AnaerobicLagoon.com



An anaerobic lagoon (above) is sealed with a flexible, impermeable cover.  The Biomethane is recovered 
and piped to the cogeneration plant, or to a biogas to biomethane processing plant for sale to a nearby 
natural gas pipeline.  Some systems use a single cell for combined digestion and storage.

More info at:  www.AnaerobicLagoon.com

_________________________________________

What is a complete mix digester?

A complete mix digester is one of the basic types of anaerobic digesters comprised of a sealed tank that organic waste materials, principally manure as generated at a dairy farm, is heated and mixed with microorganisms for breaking down the waste. The incoming liquid displaces an equal amount of liquid in the complete mix digester, and an equal amount exits. Biogas (methane or ch4) is generated inside of the complete mix digester which is then extracted from the top of the digester for biogas processing and upgrading into "biomethane" which can then be sold as natural gas to a natural gas pipeline, or used as a substitute fuel for natural gas. Retention times for a complete mix digester are in the 21 - 30 day range. 

Complete Mix Digesters

 

Diagram of a complete mix digester.

Complete Mix Digesters have an enclosed, heated tank with either a:  
mechanical, hydraulic, or gas mixing system.  Complete mix digesters work 
best when there is dilution of the manure with water, i.e. milking center wastewater

Anaerobic digestion is the bacterial decomposition of organic waste in the absence of oxygen. The two main products of anaerobic digestion are biogas and a solid residual material. 

Food scraps, manure, biosolids, as well as Fats, Oil, and Grease (FOG) can all be "digested" anaerobic digesters and the biomethane (cleaned-up and purified biogas) used to fuel a cogeneration power plant.


Benefits of an Anaerobic Digester:

Graphic depicting an anaerobic digester facility. Farm manure is processed in the digester, producing solids and liquids suitable as soil enhancers, and biogases used in the production of heat and power.

 

 

 

Anaerobic Digester Systems in the U.S. and Europe

Country

Biosolids

Biowaste / Solid

Agricultural

Industrial Wastewater

Industrial

Austria

100

3

100

25

Canada

50

13

Czech Republic

10

4

Denmark

64

21

5

Finland 

1

3

Germany

49

1,500

91

Greece

2

1

2

Italy

4

50

38

Netherlands

2

84

Norway

17

2

5

Portugal

94

3

Spain

1

6

27

Sweden

134

4

3

8

Switzerland

70

11

69

20

U.K.

200

1

25

26

U.S.A.

1,600

28

92

above info courtesy of www.usda.gov
and updated by: www.AnaerobicDigester.com 

 

 

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"Leading the Renewable Energy Revolution"


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info@PlugFlowDigester.com

 

 

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