United Process Controls, Inc.
Oxyfire-LT Installation/Operation Manual
5 |
P a g e
1 INTRODUCTION
1.1
GENERAL
The Oxyfire-LT In-Situ Zirconia Oxygen Sensor has been designed to measure excess oxygen in a wide
variety of low temperature combustion processes. It is an outstanding unit for monitoring oxygen
concentrations in combustion gas of large or small boilers, industrial furnaces and combustion processes
or for the control of low percent oxygen combustion.
The analyzer consists of a detector and converter. Optional accessories, such as electronics, reference air
units, verification units, mounting assemblies, and protection tubes may be selected to enhance
installation. The complete installation provides system care, minimizes maintenance and provides
automated or manual verification. An optimal control system can be realized if the appropriate
supplemental equipment is selected.
The Oxyfire-LT utilizes high performace Oxyfire-LT Probe technology to provide cost-effective and
reliable oxygen sensing and control in low process tempeture applications.
1.2
OVERVIEW
The Oxyfire-LT is a self-heated device that is mounted into the process flue with a flange interface. The
probe is internally heated to operate at a temperature of 600º
º
C with the application 120V AC power.
Sensor is used to monitor and control the excess oxygen concentration in combustion gases of boilers,
incinerators and other industrial furnaces.
A low temperature sensor sampling gases from 500ºF (300ºC) up to 1100º
º
F (600º
º
C) is inserted into
the process gas stream via a flange, threaded adaptor, or sealable opening. The sensor may be
installed vertically or horizontally, depending on application specifics such as temperature, gas flow,
etc. The atmosphere around the sensor tip should be moving and not stagnant. For optimum results,
the sensor should be protected from direct flame contact and located at a point where combustion is
complete.
1.3
THEORY OF OPERATION
Yttria stabilized zirconia conducts oxygen ions at temperatures above 1000°F (540°C). The driving force
of the ion migration is the difference in the oxygen concentration between the process gas and the
supplied reference air. Partial pressure laws of gases state that oxygen molecules will travel from higher
to lower concentrations. Platinum electrodes, located on both the inside and the outside of the zirconia,
detect the voltage produced by the flow of these ions. This millivolt signal is a function of the difference
in oxygen concentration. Knowing the process temperature, reference gas oxygen concentration (20.9%)
and the millivolt signal, the Nernst equation is used to calculate the percent oxygen.
The Nernst Equation is as follows:
E
0.0215
mV
K
T
ln
%O2_reference
%O2_process
