Flue Gas Emissions

Most people buy a flue gas analyser for one of three reasons, and knowing which is yours decides the instrument before any specification is compared.

The first is combustion tuning, and it is the reason the instrument pays for itself. Optimising the combustion process improves efficiency, reduces emissions and increases performance. A correctly tuned unit burns less fuel, emits less, lasts longer and runs more reliably. A badly tuned one misfires, runs hotter, wears faster and costs more to service. On diesel generation, air surplus, fuel pressure, ambient temperature and humidity all significantly affect how a unit runs and what it emits, which makes tuning a measurement exercise rather than a judgement one. On gas turbines, proper combustion tuning also reduces the risk of flame instability and other operational problems that cause significant downtime.

The second is compliance. Emissions of nitrogen oxides, carbon monoxide and unburned hydrocarbons have to be minimised to meet regulatory requirements, and demonstrating that needs a measurement rather than an assertion.

The third is the one people do not expect, where flue gas analysis is a product quality control. In glass manufacturing the melting process produces oxygen, carbon dioxide, sulphur dioxide and nitric oxide, which are displaced during refining to prevent defects forming on the glass surface. Nitrogen oxides form when nitrogen and oxygen react at furnace temperatures. Sulphur oxides come from the decomposition of sulphates in the batch and sulphur in the fuel. The ideal loss value of 15 percent should not be exceeded, because beyond that the clarification of the melt is compromised. Here the analyser protects the product rather than the people or the licence.

Gastech supplies the Testo range across all three cases. The testo 310 ii covers straightforward boiler and heating work. The testo 300 comes as a domestic or a professional kit. The testo 340 is supplied as a boiler kit, a diesel kit or a gas engine kit, so the instrument arrives configured for the fuel rather than needing to be adapted to it. The testo 350 is the industrial analyser, measuring oxygen to 25 percent by volume and carbon dioxide by infrared to 50 percent. On the combustion and toxic side it reaches 10,000 ppm carbon monoxide, 40,000 ppm methane, 4,000 ppm nitric oxide, 5,000 ppm sulphur dioxide and 500 ppm nitrogen dioxide. A maritime version of the 350 is available, along with the testo 380 for particulate measurement in combustion gas.

Four practical points decide whether an analyser survives the application, and they matter more than the headline gas list. Sample temperature is the first, since a furnace or turbine exhaust needs a probe rated for it, which in glass melting means a high temperature ceramic probe. Dust is the second, affecting both the probe and the sampling path. Humidity is the third, because condensing moisture in a sample line affects the reading and the instrument. Calibration is the fourth and the most often overlooked, because an analyser used to tune a turbine or demonstrate compliance is only as good as its own certified accuracy.

For tuning and testing that happens once or twice a year, hire usually works out better than owning, and hire units arrive calibrated with certification. Our Technical Consultants will work through the fuel, the sample conditions and the gases you actually need, from WA, NSW and QLD.