A Nitric Oxide/Ammonia Sensor for Fossil Fuel Combustion Control Applications

EPA Grant Number: R826164
Title: A Nitric Oxide/Ammonia Sensor for Fossil Fuel Combustion Control Applications
Investigators: Vetelino, John F. , Dwyer, Daryl F. , Segee, B. E.
Current Investigators: Vetelino, John F.
Institution: University of Maine
EPA Project Officer: Shapiro, Paul
Project Period: January 21, 1998 through January 20, 2000
Project Amount: $197,761
RFA: Exploratory Research - Environmental Engineering (1997) RFA Text |  Recipients Lists
Research Category: Engineering and Environmental Chemistry , Land and Waste Management


The Detection and measurement of flue gases are critical not only for achieving real time process control of new clean combustion systems, but also to minimize the emissions of dangerous air pollutants generated by these systems. Among the most dangerous of these air pollutants are nitric oxide (NO) and nitrogen dioxide (NO2), collectively referred to as NOx. Currently about one half of all NOx emission into the environment is due to power plants and industrial boilers. If NOx concentrations exceed certain critical levels, immediate threats to health and the environment are posed.

In combustion processes such as coal, 90-95% of all NOx emissions are NO. In order to minimize the NO released in the environment, flue gas treatment techniques such as selective catalytic reduction (SCR) are employed. In this process ammonia (NH3) is injected into the flue gas stream, where it reacts with NO to form environmentally safe gases such as nitrogen and water vapor. This process, however, is usually incomplete, resulting in NO emission and the emission of NH3 (NH3 slip).


A critical need exists for an in situ NO/ NH3 sensor that can operate at the output of the SCR system near the stack and serve as an in situ sensor in a real time control system which would control the NH3 injections and hence minimize NO emissions to the environment. The development of such a sensor is being proposed. This sensor utilizes a tungsten trioxide film (WO3) as the sensing element and a neural network to provide selectivity. In order to establish WO3 films as viable NO and NH3 sensing elements, electrical conductivity measurements of doped and undoped films will be made upon exposure to various concentrations of NO and NH3 at a variety of temperatures in a simulated flue gas environment. Conclusions will be made relative to the optimum temperature(s) and film parameters (dopant and thickness) to obtain maximum sensitivity. After appropriate films have been selected, neural network techniques will be employed to attain maximum selectivity for NO and NH3.

Expected Results:

The proposed research program will determine the feasibility of using multiple WO3 films of varying parameters, in conjunction with a neural network, to simultaneously detect NO and NH3 in a simulated flue gas environment. It is anticipated that the results of the proposed research will form the knowledge base to develop a combustion sensor array that can be used to detect not only NO and NH3, but also other combustion gases such as hydrogen sulfide ( H2S ) and various sulfur oxides ( SOx ). This sensor array would be a critical element in a control system whose objective is to minimize the release of dangerous combustion-generated air pollutants. The control system would prove to be valuable where fossil fuel combustion is integral to operations, such as power plants, pulp and paper mills, petroleum refining, mines, steel mills, motor vehicles, and many others.

Publications and Presentations:

Publications have been submitted on this project: View all 3 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 1 journal articles for this project

Supplemental Keywords:

atmosphere, nitrogen oxides, innovative technology, engineering., RFA, Scientific Discipline, Waste, Environmental Chemistry, Incineration/Combustion, Environmental Engineering, Nitrogen dioxide, sulfur oxides, selective catalytic reduction, air pollution, chemical contaminants, coal, ammonia sensor, Hydrogen sulfide, flue gas emissions, fossil fuel combustion

Progress and Final Reports:

  • 1998
  • Final Report