Oxygen Measurement Improves Efficiency and Product Quality in Cement and Lime Kilns0 pages

Cement & Lime Manufacturing

Application Data Sheet

Oxygen Measurement Improves Efficiency and
Product Quality in Cement and Lime Kilns
The measurement of oxygen (O2) inside a rotating kiln provides
a good indication of combustion efficiency. This oxygen
measurement can also provide an inferred indication of calcining
rates and the production of thermal NOX . Maintaining a consistent
oxygen level can prevent variations in product quality.

at the end of a long probe, and use passive filters with no educator,
sample pump, or other method of inducing flow into the analyzer.
The flue gases simply diffuse into the sensing cell on the end of the
probe, and the diffusion element filters last for many months.

New Design Addresses Application
Difficulties

Getting an unbiased flue gas stream to measure is another challenge.
While kilns will typically utilize “leaf seals” to minimize the amount
of ambient air that gets drawn in between the rotating kiln and the
stationary feed box, some upwards biasing of the flue gas O2 levels
is usually observed, depending on the quality and age of the seals.
There are a couple of methods of minimizing this biasing of
“tramp air”:

The zirconium oxide (ZrO2)measurement technology has become
the standard for measuring oxygen in any combustion processes. A
measurement accuracy of +/- .05 % O2 is achievable, and the sensing
cells are very robust. However, some application difficulties hamper
getting a suitable measurement of oxygen in a rotating kiln.

Particulate
The flue gas exiting from the kiln presents the best opportunity
for measuring oxygen, but heavy particulate levels prevent the
use of extractive methods without extensive filtering and sample
conditioning systems, and the associated high maintenance
required of such systems. In Situ O2 probes place the sensing cell

Tramp air

1.t Testing with a portable analyzer and long sample probe to
discern the “core” of the flue gas flow, ie. area inside the flue gas
ductwork exiting the kiln where the oxygen least affected by
the tramp air.
2.t Utilize a long in situ probe, angled past the rotating seal. See
figure 2.

Figure 1- Proper installation of an oxygen probe in a rotating cement kiln

Limestone Feed
Oxygen Probe installation
(shown with out protective jacket)

Firing Direction

Flue Gas exhaust

Product Flow
Rotating Leaf Seal