Electrostatic Precipitators for Pollution Control

August 2, 1990

ELECTROSTATIC PRECIPITATORS

Started in 1980, Project Recoup was a program for applying advanced technology to the solution of a problem shared by a growing number of U.S. communities: how to dispose of refuse in areas where acceptable landfill sites are scarce.

Jointly sponsored by Langley Research Center, Langley Air Force Base and the adjoining City of Hampton, Virginia, the program involved development of a Refuse-fired Steam Generating Facility that incinerates trash, reduces it to a readily-disposable ash, and employs the heat of trash burning to create steam for practical use at Langley Research Center.

A design base for modeling similar projects elsewhere, the facility has proved eminently successful. It disposes of all solid waste from the NASA center, the Air Force Base, and other government installations in the area, and it also accommodates about 70 percent of Hampton's municipal waste.

Hampton, principal financier for the project, realizes revenue from trash disposal fees and from the sale of steam to Langley Research Center. And there is an energy conservation bonus in that the steam generated by burning waste cuts the amount of fuel normally used by Langley by some two million gallons a year.

The project produced another bonus that has largely escaped notice: an air pollution equipment control device, developed of necessity in the course of the program, that is now commercially available.

The device is an advanced electronic control for electrostatic precipitators, widely used in pollution control applications throughout industry. It is built by Kinetic Controls, Inc., Newport News, Virginia, a company formed by two NASA/Langley employees--T.K. Lusby, Jr. and David F. Johnston--who developed the control as their contribution to Project Recoup, working for the most part on personal time and with private funds.

The function of an electrostatic precipitator is to remove particulate matter from the combustion gas created by the burning of a fuel before the gas is expelled through a smokestack.

When standard fuels are burned, the smoke is of relatively constant composition and the highest practical voltage is fairly constant; once the voltage is set, as long as the same type of fuel is used, only small changes in precipitation voltage are needed.

But when refuse is used as a fuel, the composition of the smoke changes continually and that requires corresponding changes in voltage over a very wide range.

To insure minimal pollution of the atmosphere, the two NASA/Langley employees undertook to develop an innovative, microprocessor-based control that automatically senses and compensates for the changes in smoke composition by adjusting the precipitator's voltage and current to permit maximum particle collection.