Continuous particulate emissions monitor calibrator

Details Continuous particulate emissions monitor calibrator Continuous particulate emissions monitor calibrator

1996-03-18

1998-06-02

Nelms, David C.

Optics: measuring and testing

For light transmission or absorption

Of fluent material

356438, G01N 2100

Patent

active

057609110

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates in general to a device for monitoring particulates passing through a duct, such as for instance, passing through a duct in a baghouse discharge or from an industrial stack. In particular, the present invention relates to a device for monitoring the frequency at which a light shown across an emissions duct is interrupted. More specifically, the present invention is directed to a method, system, and device for correlating a selected percentage opacity with its associated reading in concentration units in connection with such an emissions monitor.
2. Description of the Related Art
Emissions monitoring has become increasingly important in response to strict environmental regulations and increased public awareness of environmentally-safe industrial processes. Numerous types of devices have been developed for monitoring particulate emissions in industrial applications. In general, these devices monitor the particulate flowing through a duct or stack, and particularly, monitor the amount of particulate being emitted. In this regard, the greater the concentration or percentage of particulate relative to the emissions as a whole, the greater the quantity of pollutants entering the atmosphere. If an industrial process emits pollutants into the air in excess of a maximum permissible amount as set by the Environmental Regulators, great expense associated with fines and perhaps shut-down can be incurred. Accordingly, monitoring particulate emissions is extremely important for maintaining a clean environment and transacting business in accordance with the law.
Numerous devices and systems have been developed for monitoring particulate emissions. One conventional system utilizes what is called opacity technology. In general, opacity devices shine light from a transmitter located on one side of a stack or duct to be monitored to a receiver located on the opposite side of the duct in optical alignment with the transmitter. As dust travels through the stack or duct, the dust both scatters and absorbs some of the light provided by the opacity device. By comparing the brightness or intensity of the light shining across the stack or duct when no emissions are occurring with the dimmer brightness or intensity of light associated with dust traveling through the stack, a percentage opacity measurement can be obtained. Percentage opacity is a commonly used unit for measuring emissions. Another type of emissions monitoring device, called an impaction or triboelectric device, utilizes an earth-grounded probe inserted into a stream of particles to be monitored. As each particle impinges onto the probe, a transfer of electrical charge occurs which results in an electrical current at the probe. Monitoring the current results in a relative emissions measurement.
The foregoing devices have numerous drawbacks which reduce their effectiveness and desirability. For instance, opacity systems, which are based upon the amount of light energy detected through passing dust, quickly become inaccurate as lenses used by the device become caked with dust. In other words, as particulates build up on the sensors, the opacity device is unable to distinguish between moving dust being emitted from the stack or duct and stationary dust which continues to settle on the sensors. Accordingly, the reading in such an environment is inaccurate. In this regard, an opacity device having dust accumulated on the sensors will show an emissions reading even when no emissions are occurring. Accordingly, the sensors of an opacity device require constant cleaning. Similarly, impaction or triboelectric devices, which have a probe positioned within the dust stream, quickly become dirty and must be repeatedly cleaned. Periodic cleaning of the foregoing devices, in addition to requiring repeated extensive time and effort, increase the cost of using such devices.
A more recent device for monitoring particulate flowing through a duct or stack uses a DC light beam shining across the duct or st

REFERENCES:
patent: 3632209 (1972-01-01), Kingman
patent: 3779650 (1973-12-01), Crowley
patent: 3825345 (1974-07-01), Lorenz
patent: 3879129 (1975-04-01), Inoue
patent: 4135821 (1979-01-01), Pechin et al.
patent: 4420256 (1983-12-01), Fladda et al.
patent: 4583859 (1986-04-01), Hall, II
patent: 5028790 (1991-07-01), McGowan et al.

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