Combustion flue gas analyser

Helps reduce emissions and improve efficiency of combustion processes

The latest solution for combustion flue gas analysis, the Rosemount Analytical Model 6888 in-situ oxygen analyser has just been launched by Emerson. The Model 6888 provides accurate measurement of the oxygen remaining in the flue gases coming from combustion processes such as boilers, incinerators, kilns, process heaters and industrial heating furnaces. By maintaining the ideal level of oxygen in the flue gases, optimal efficiency is achieved and the lowest levels of NOX, CO, and CO2 are produced.

The in-situ design of this instrument places a zirconium oxide sensing element at the end of a probe which can be inserted directly into a flue gas stream. Probe lengths are available from 45cm to 3.65m, and a slip mounting option provides the ability to mount a long probe at any insertion depth. Signal conditioning electronics reside in the head of each probe, eliminating the need for expensive signal cable.

The Model 6888 is fully field-repairable. All active components can be replaced, including the diffuser/filter, sensing cell, heater and thermocouple, and all electronics cards. A dual-channel operator interface unit provides an easy-to-use method of set-up, calibration and failure diagnostics.

It offers unique optional features never before possible in an oxygen analyser. Since the calibration frequency of an oxygen analyser is highly application-dependent, the Xi electronics provide an on-line diagnostic that determines when calibration should be conducted. This feature greatly reduces unneeded calibrations, technician time and calibration resources. The feature can trigger a fully automatic calibration by sequencing solenoids to introduce calibration gases to the sensing cell. Calibrations can be conducted on-line while the furnace is in operation.

Another feature of the Model 6888 is its ability to continue operation through process upsets. If process upsets cause flue gas temperatures to exceed the normal sensing cell heater temperature (736oC, 1,357oF), the heater is turned off, the process is permitted to heat the sensing cell, and the electronics calculate the oxygen content of the flue gases on the fly. If process upsets cause a reducing condition (flue gas oxygen levels decline to zero), a stoichiometer feature provides an indication of the level of oxygen deficiency during this event.

In applications where there is a heavy particulate loading in the flue gas stream, a plugged diffuser diagnostic feature notes the "return to process" time after calibration gas is turned off. As the time extends, the diagnostic will indicate the need for a diffuser replacement.

"As the needs and compliance demands for flue gas analysis become greater, we are making our Rosemount Analytical instruments more and more accurate and easy-to-use to meet our customers’ requirements. The Model 6888 promises real savings in time and resources for users, as well as a way to achieve compliance with government regulations," stated Dave Anderson, Marketing Director, Emerson Process Management, Rosemount Analytical.