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Diesel Particulate Removal System

Environmental Energy Technologies, Inc.


Diesel engine emissions are notoriously dirty, both in their chemical and particulate matter (PM) components. Particulate matter (soot) has been especially hard to remove from exhaust gasses and has been under increasing scrutiny from public attention and environmental regulators. Current emission control systems consist of filtration technologies that typically require thermal regeneration or media replacement in order to remain operable. Both of these systems, while operationally effective, offer opportunities for improvement in performance and cost. Additionally, these devices tend to clog, thereby increasing the exhaust back-pressure and negatively affecting engine performance. The extra fuel needed to compensate for the efficiency loss counteracts the positive effects of the filter.

Previous studies have found that strong electronic fields can ionize gasses and change their chemical properties through an oxidation reaction. Although this is low temperature, the oxidation processes technically “burns” molecules into simpler, less harmful components. This electronic field is referred to as Non-thermal plasma (NTP). Previous studies have found such electronic fields reduce PM, HC, CO, and NOx in tailpipe emissions in conjunction with a three-way automotive catalyst.


Develop an emission control device for diesel engines using a Non-thermal Plasma field. The NTP will reduce chemical components to simpler and less harmful gases that can be safely emitted, thus eliminating the need for filter cleaning or replacement. The design will be self-regulating and not have a backpressure penalty typical of filtration devices. The device should be scalable for different size engines,  be packaged for purchase, and be easily installed as a retrofit to existing systems. Both stationary and mobile engines should be able to use this device. Key testing will be done through recognized emissions testing laboratories to verify results.


Environmental Energy Technologies (EET), a spin-off of Rochester Institute of Technology is developing an emission control technology for diesel engines based on the use of non-thermal plasma (NTP). NTP creates highly reactive oxidizing agents (such as O-, singlet oxygen; OH-, NO,  and NO2) that react with and reduce the presence of soot particles, volatile and semi-volatile hydrocarbons, and carbon monoxide in diesel exhaust. A particulate removal system using NTP works by charging particles in an exhaust stream by corona discharge, which is created by a high voltage electrode. The center electrode is negatively charged, while the wall of the exhaust pipe is grounded. The corona discharge uses the electrode at very high voltage (20-50 kV), but the current used is usually very low, from 0.01 mA to 2mA. The voltage is kept just under what would be necessary for the electrode to arc to the inside of the pipe using pulsed power. In the DPRS chamber, the collision between electrons and gas molecules of electronegative gases such as oxygen, carbon dioxide, and sulfur dioxide results in capture of electrons to produce negative ions such as O-, O2-, O3-, OH, and NO2 (from conversion of NO). These highly reactive radicals oxidize particulates into gases such as CO, and CO2.

EET has developed prototypes that have shown low back pressure and self-regenerating operation as an exhaust after treatment device for diesel engines. EET has also demonstrated the synergy of the NTP technology with a low pressure exhaust gas recirculation (EGR) system for NOx control. Promising results have been achieved in a NTP/EGR test program performed at Southwest Research Institute (SwRI).  Current field work involves testing equipment with on-road tests and verification of results. Hardware configuration has been tested and electrical systems continue to be developed. Communications with manufacturers and installers has begun, with the development of promising partnerships between major manufactures of on-road and off- road diesel equipment. EET is also developing product lines for larger engines to expand its product line.


NYSERDA has funded research through five phases of this project from concept through testing. Through this effort, NTP was discovered to be energy efficient, requiring less than 100 watts, and it is capable of removing 50% - 80% of particulate matter with little effect on exhaust back pressure compared to conventional filtration methods. The device is self-regenerating by design and will not need cleaning or replacement in normal use. The device also has been shown to work well during cold engine startups, whereas filters have to come up to temperature before they work effectively. It appears to be effective against both soluble and insoluble types of particulate matter, and it does not require precious-metal catalysts, which will help lower the cost of manufacture. Initial performance and durability test results, based on 18 months of operation in transit bus service, have been successful to date.  The current project path is aimed at achieving performance verification through formal test procedures of the U.S. Environmental Protection Agency or the California Air Resources Board. This level of emissions verification would be a major accomplishment and would greatly accelerate commercialization of the device as a retrofit to in-service engines. The finished product is envisioned to result in new manufacturing, job growth, and related economic development opportunities in New York State.


Barry Liebowitz
Sr. Project Manager
518-862-1090, Ext. 3248

Last Updated: 02/27/2013