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November | December 2011

Feature title: Direct Cold Plasma: The innovative answer to odour control in the food and feed industry

The International magazine for the aquaculture feed industry

Increasingly, feed manufacturers are being required to address the issue of release of odour and harmful contaminants into the

surrounding community.

Local communities, special interest groups and government legislation all bring pressure to bear on factories to minimise real or perceived risks of contamination. There are no universally applied standards for odour or Volatile Organic Compounds (VOC) emissions and to provide solu-tions that fit specific factory needs can be complex.

There is no single solution but under-standing the feed manufacturers problems certainly helps a great deal.

In recent years, there have been numerous changes regarding where pro-duction facilities are

situated. Factory closures and relocation of manufacturing units has become com-monplace. At the same time urban sprawl has resulted in residential areas being built closer to previously remote industrial areas.

Another pressure companies face is meeting local environmental needs.

So what does the industry need from its odour abatement equipment? This is a complex question and the answer needs to include:

• A compact design minimizing space requirements

• End of pipe solution• Low running cost• Minimal maintenance• Ability to operate at normal feed

manufacturing temperatures, to avoid cooling costs

• High odour removal efficiency• No chemical additions and need to

maintain chemistry• No liquid effluent waste• Instant on/off – no warm up time• Modular construction, ease of reloca-

tion if change of production location and ease the ability to add on mod-ules according to required capacity

• Competitive capital costThis is a tall order but there is a

technology can answer most of these needs: Cold Plasma.

Direct Cold Plasma – A high-tech, high-voltage solution

In 2003 a global petfood manufac-turer tested a new technology for odour removal, referred to as Direct Cold Plasma, on drier and extruder flash-off exhausts.

The technology had obvious advantages over more conventional solutions. As a result the petfood manufacturer looked for a suitable technology partner for collabora-tion on the application of cold plasma on petfood applications.

In 2003 they formed such an agreement with APP (Applied Plasma Physics AS).

APP is both an R&D and equipment sup-ply company, specialising in the application

of high voltage technology and non-thermal plasma systems for industrial processes. APP has now delivered more than 200 sys-tems, most running on difficult applications.

APP has experience on ultra-high odour applications – where odour levels can be over 200,000 odour units per m³ - and the company achieved odour removal efficien-cies of up to 97 percent. Another advantage that is unique for this specific technology is that both odour and dust are removed from the production emissions.

Cold plasma technology – Nature in a box

Odour bearing gases enter the cold plasma module, where care is taken to distribute gases evenly as it enters the reaction chamber. The reaction chamber comprises a cluster of hexagonal cells. Running centrally through each cell is a corona wire, which is isolated from the rest of the chamber.

The high voltage generator distributes

by Havard Vetrhus, Director Sales & Marketing, Applied Plasma Physics AS, NorwayTel: + 47 5160 2220Email: havard.vetrhus@app.no

22 | InternatIonal AquAFeed | november-December 2011 november-December 2011 | InternatIonal AquAFeed | 23

F: Direct Cold Plasma

IAF11.06.indd 22 04/11/2011 08:41

a modulating high voltage supply to each corona wire, and this process results in a discharge between the corona wire and the cell wall. The discharge promotes the emission with high-speed electrons, which collide with background gas molecules cre-ating chemically active species known as radicals and charge carriers.

This is actually identical to what happens with pollution in the atmosphere. Reactions occur with the odour bearing compounds in the gas to be treated. Ambient air may be injected just prior to the reaction chamber to optimise humidity and temperature as well as adding ions to the gas stream.

In essence the cold plasma process encourages ‘oxidation’ of the odour bearing compounds at low temperature by creating discharge (cold plasma).

A closed-loop cooling unit ensures that operating conditions within the High Voltage Generator are maintained within controlled limits. A proprietary control system moni-tors the high voltage passed to each of the corona wires in the reaction chamber, and controls the voltage modulation that generates the cold plasma. The system also detects arcs between the corona wire and the cell wall, automatically shutting down electrical supply for a fraction of a second before power is reinstated.

The reaction chamber may be oper-ated with the gas flow passing upwards or downwards depending on site layout. The unit is capable of operating on emissions with relative humidity close to 100 percent, although the closer to 100 percent RH the unit operates, the higher the possibility of arcs and consequently risks of reduced efficiency. The unit can be operated with emission temperatures up to 70°C. In most cases in the feed industry, the emission temperature from dryers will be less than this temperature limitation.

Maintenance is minimal, if the unit is used as a dust collector as well as odour abatement system, then the unit would have a ‘wash-down’ maybe once per week and an internal inspection

once a month would be recommended. Operating costs are very low and mostly associated with the cost of electricity; 10-20kW for a standard 20,000m³/h cold plasma unit.

A costing exercise produced by one of APP’s customers, is shown below. This is based on a 10-year period, including both investment and operating cost for a volume of 20,000 m³/h. The operating costs for the scrubber alone or scrubber biofilter do not include cost of water.

Testing in the petfood and fish feed industry

Since 2003, extensive testing with a pilot system both on extrusion flash-off, driers and coolers has been carried out. All possible variables have been reviewed to determine the optimum operating condi-tions for the cold plasma system.

Variables tested:• Residence time (determines volume

to be handled by a standard module)• Effects of water scrubber at inlet or

outlet of cold plasm• Cold plasma unit operating alone• Adding water to humidify inlet or

outlet gas• Air infiltration

volume (ion enrichment)

• Intensity of cold plasma generation

• Geometry and arrangement of reaction cells

The pilot plant

is designed to handle 1600m³/h and tests were repeated to check val id-ity. Independent o l f a c t o m e t r y testing was used as a means of d e t e r m i n i n g odour reduction efficiency.

Test results indicate that odour removal efficiencies of up to 90 percent are achievable within the food and feed industry and that the standard

colds plasma module will handle around 20.000Am³/h.

Higher efficiencies may be achieved by using a final polishing module. During testing, both high and low odour concentrations were experienced; nonetheless cold plasma achieved real odour reductions even on very low inlet concentrations, something that is not always the case on alternative technologies.

Overall the tests indicated that the cold plasma unit operated most effectively without a scrubber either at the inlet or outlet. Dust removal was very effective (99 percent reduction).

As a result of these tests, several pet-food sites have now installed cold plasma technology for their processes.

As per today, 50 units are in operation in the petfood industry, a figure that will increase substantially in the years to come.

The experience of the environmental needs of the feed industry, and APP’s approach to innovative design is com-bined to offer a competitive alternative solution to a problem that is of increas-ing significance to the food and feed industry.

22 | InternatIonal AquAFeed | november-December 2011 november-December 2011 | InternatIonal AquAFeed | 23

F: Direct Cold Plasma

ambientair powerpack

fromprocess

toexhaust

WWW.AEROXINJECTOR.COM

Our compact but powerful Aerox®-Injector uses Cold Plasma Injection Technology to treat up to 80.000 m3/h.

The major advantage of the Aerox®-Injector is that it radiates clean, ambient air sourced from outside the process duct, which it then injects into the process duct.

Suitable for saturated exhaust gas flows!

Unit is placed outside the process duct

Cold Plasma unit remains clean

Compact and easy to install

No pressure drop

Easy maintenance

Runs on electricity

No waste products

IAF11.06.indd 23 04/11/2011 08:41

18 | InternatIonal AquAFeed | november-December 2011

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feed-additives@evonik.com | www.evonik.com/feed-additives

11-01-377 vND AZ Aquaculture A4 us.indd 1 27.10.11 16:58IAF11.06.indd 19 04/11/2011 08:41

EDITOR’S DESK

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2 | InternatIonal AquAFeed | november-December 2011

in Molde, NorwayWelcome to ISFNF 2012

Key areas:

■ Sustainable resources

■ Health, welfare and ethics

■ New methods and working-tools

■ Feed technology and feeding regime

■ Nutrigenomics

■ ‘omics’ data and system biology models

■ Nutritoxicology

■ Nutrition in whole life cycle

Please submit your abstract at www.isfnf.org by 20th January 2012

Welcome to Molde in 2012 for the 15th consecutive International Symposium of Fish Nutrition and Feeding 4-7. June 2012

Some conference ingredients:

■ Get updated on the latest research on fi sh nutrition and feeding

■ Mingle with the 500 leading fi sh nutritionists in the world

■ Pre symposium tour to visit industry

■ 4 post symposium sight seeing tours in the beautiful coastal fjords

Phot

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Nofi ma will host the event along with the Aquaculture Protein Centre (APC), the National Institute of Nutrition and Seafood Research (NIFES), the Norwegian School of Veterinary Science (NVH) and the Norwegian University of Life Sciences (UMB).

AD_Nofima_210x297+3.indd 1 01/11/2011 09:19IAF11.06.indd 3 04/11/2011 08:40

www.aquafeed.co.uk

LINKS• Seethefullissue• VisittheInternationalAquafeedwebsite

• ContacttheInternationalAquafeedTeam

• SubscribetoInternationalAquafeed

VOLUME 14 I S SUE 6 2 011

THE INTERNATIONAL MAGAZINE FOR THE AQUACULTURE FEED INDUSTRY

BioMarine Business Convention

Ecobiol Aqua– A unique and highly effective single strain probiotic

Evaluation of probiotic bacteria in tilapia production

Marine based protein hydrolysate- Improve the performance of feeds containing

a low level of fish meal

IAF11.06.indd 1 04/11/2011 08:40

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