Combustion of coal in thermal power stations is one of the major sources of anthropogenic emission of mercury. In view of increased consumption of various fossil fuels such as coal, oil and gas, there is a growing concern in India on environmental degradation brought about by fuel combustion. Proper collection and estimation of mercury in flue gas is essential for assessing and monitoring the level of mercury emissions into the environment. Conventional method of drawing samples from flue gas for mercury estimation generally uses ss-probe (stainless steel probe). This can lead to the problem of sticking of mercury vapour on alloy steel surface, thereby introducing error in estimation. A new technique of using suitably designed glass probe is proposed which can minimize the problems associated with steel probe. A suitable glass probe has been designed and constructed which is provided with easily assembled and demountable parts. The newly constructed glass probe has been tested and verified by drawing Hg vapour samples from simulated Hg-laden gas stream as obtained from simple laboratory arrangements in a nebulised flame system of AAS equipment.
A comparative assessment for collection of flue gas has been carried out by inserting the probe inside the sample port of the stack, at the position of the mean velocity point. The flue gas samples are drawn maintaining an iso-kinetic condition. The collection of the gas samples had been done side by side by using a glass probe and a stainless steel probe in a 500MW-boiler unit of a coal based power plant situated at Singrauli region of India. The comparative study shows a slightly improved mercury sample, collected through glass probe as compared to the ss- probe (stainless steel probe)
