Air Phaser Environmental

New NTP based Odor Control at 100,000 TPY Compost Facility Automatically Adjusts to Changing Odor Conditions

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This is a new facility located in southern Ontario that accepts construction and demolition waste (C&D) and 100,000 TPY of source separated organics (SSO) waste. In keeping with the design philosophy to use the best available design and technology, the owners elected to incorporate a new non-thermal plasma (NTP) system to control the odor in its 120,000 cfm air emissions. This NTP system is very compact, fits easily on a platform (see Fig. 1 – the boxes with the green lights), is fault tolerant, uses only a modest amount of electricity and is fully automated to adjust to changing odor conditions.

This technology passes all air through the non-thermal plasma (NTP) fields to neutralize the odor in the air. This transforms the airborne odorous compounds as they pass through the NTP by triggering simultaneous oxidation and reduction reactions in the presence of atomic oxygen. Since all reactions are in the presence of an intense electrical field (the NTP field) and are in air, the gas phase reactions are extremely fast, the majority of them take place in a fraction of a second. There are some subsequent slower reactions continuing in the exhaust duct that involves some hydroxyls, peroxyls and peroxides formed in the NTP field with the moisture in the air and this all helps in the neutralization of the odor. The system is PLC controlled and keeps the exhaust air constant by using an outlet gas analyzer to provide feedback to a controller that modulates the power to the NTP field automatically to compensate for any odor changes in the inlet air.

The system is a very low maintenance solution and it is comparable to a neon light in some ways, which also is a non-thermal plasma. The difference here is that while the neon light has neon enclosed in a tube under high voltage and high frequency, this system passes the odorous air through the catalytic dielectric barrier discharge plates which are under high voltage and high frequency so that the odorous air is transformed to oxidized and non odorous forms. The similarities with a neon light system are that there is nothing to wear out and the catalyst material of the electrodes is not consumed when in operation. The electrodes are compact in size, being approximately 300mm by 150mm with the dielectric barrier matching this in size, so in the rare cases when a ceramic dielectric barrier plate breaks, the system automation automatically senses this, shuts that section down diverting the air flow to the many other sections so the air is continued to be treated. This gives the system fault tolerance as a number of sections can be shut down and the system as a whole still will treat the air with the remaining operational sections. Being of a compact size, the electrodes and plates are also easily changed by a single maintenance person once there is an opportunity to do so and this can be done while the other sections remain in operation.

The compost process is done in a completely enclosed environment, thus the air drawn off the contained environment is super-saturated. A small in-duct heater raises the temperature just enough to prevent condensation in the duct, though the humidity is still very high. Normally, in a high voltage system this would cause maintenance problems. That is not the case here, however, as the patented system high voltage electrodes are both vented for expansion yet sealed against process. Thus they operate without problems even with this high humidity, odorous air. Energy usage is approximately from 1 to 2 watts per cubic foot of air per minute (CFM), so it uses less power than even the fans that move the air in older technology systems.

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A closer look at the typical cabinet for the NTP electrodes shows the 1.25 meter wide by 1.25 meter high cabinets have dual viewing windows so that the plasma field can be observed while in operation. All high voltage is contained in the Kirk Key mechanically and electrically interlocked cabinet which has 4 levels of hard wired interlocks so that all local safety codes are exceeded for equipment and personnel protection. Multi-colored status lights give an instant indication of the system state and the platform mounting in the compost area is good in that the system, which needs little maintenance, is out of the way of the normal day to day operations activities of a typical large scale compost facility.

This new technology tested greater than 98% odor removal efficiency using multiple samples and a standardized odor panel, giving it very good effectiveness in a compact, fault tolerant, fully adjustable and automated package. Since existing systems can be retrofitted with this new technology, it is viable for any existing facility.