Mercury Stack Monitor SM-3

Continious emission monitor (CEM) for mercury
SM-3 Mercury Stack Gas Monitor
Approved by TÜV (published in GMBl Nr. 33/1999)
Detects elemental, ionic and bound mercury
True continuous measurement
(no measuring cycle)
No wet-chemistry - no use of reagents
Maintenance-free solid state catalyst
Range 1 ... 45; 0 ... 75; 0 ... 500 µg/m³ Hg
(others optional)
Corrosion protected rugged construction
Compact size, mobile operation possible
Fields of application

The SM-3 Mercury Stack Gas Monitor is used for continuous monitoring of mercury in stack gas. Bound forms of mercury like HgCl2, HgO, HgS and particulate mercury are detected as well as elemental mercury.

  • Municipal Waste Incinerators
  • Sewage Sludge Incinerators
  • Hazardous Waste Incinerators
  • Cement Production
  • Coal Fired Power Plants
  • Thermal Soil Resanitation Plants
  • Wood Combustors Using Recycled Wood
  • Metal Recycling Furnaces

Operating principle

A sample gas stream is taken from the duct through a heated sampling system. The gas is drawn through a high-temperature particulate filter and subsequently enters the reduction unit. In this part of the analyzer a thermo-catalytic reduction of ionic and bound mercury is performed. Elemental mercury vapor is formed as a result of this transformation process. The gas is then dried in a maintenance-free peltier cooler and fed to the mercury detector where the mercury concentration is measured with the so called "cold vapor atomic absorption spectroscopy (CVAAS)" method. The high surface temperature of the gas entry filter guarantees that mercury is thermally completely desorbed from particles and thus also detected.

Figure: Schematic flow diagram of SM-3 Mercury Stack Monitor


Design features

All surfaces coming into contact with the sample gas are heated to temperatures >180¡C to prevent any adsorptional loss of mercury . The sample line is made of perfluoralkoxy (PFA), a material which shows extremely weak interaction with mercury vapor. Sampling and reduction are performed at temperatures far above the dew point. Therefore no condensate is formed before all mercury is in elemental state. This minimizes signal noise and avoids nonspecific peaks.

The SM-3 avoids to use any gold collector for mercury preconcentration thus giving a very fast response and providing results continuously and in real-time. Possible problems connected with "poisoning" of the gold surface are thus eliminated.

The straightforward analysis avoiding wet-chemical sample treatment and avoiding a gold trap ensures high reliability and low maintenance.

Easy to operate
The SM-3 is operated via a waterproof membrane keypad. All inputs required are selected in a readily understandable menue shown on the graphical display. It is also possible to initiate functions like zero adjustment and calibration check from an external computer.

Low maintenance and low costs of ownership
Thanks to the new thermo-catalytic sample treatment method no reagents are required. Compared to first generation instruments employing wet chemical sample preparation methods, the SM-3 features clearly increased reliability and requires only minimum maintenance. This results in particularly low cost of ownership and maximum availability.

Quantitative determination of the mercury concentration is performed in a UV-photometer with an electrodeless low-pressure mercury lamp. This lamp is controlled using the reference-beam-method which ensures a highly stable baseline.

Automatic zero adjustment
The zero line of the SM-3 is checked and adjusted automatically after a preset period of time. A magnetic valve stops the sample gas stream and switches over to zero air which has been cleaned in a carbon filter. Automatic zero adjustment is performed every hour and requires 30 seconds.

Automatic self-cleaning filter
To prevent the instrument from being plugged up by dust-particles, the SM-3 has a self-cleaning filter system which is operated by compressed air. The cleaning function is automatically activated every hour and is a matter of seconds

Sampling system
The sample gas is extracted with a stainless steel probe and conducted through a heated tube to the analyzer. The entire sample line is made of perfluoralkoxy (PFA), a material guaranteeing a minimial memory effect. The dimensions of the sampling system mounting flange are customized (for example DN 80/PN 6 or ANSI 3"/ 150 lbs).

The importance of continuous mercury emission monitoring
Monitoring of mercury emissions from stack has become a global issue. More strict regulations by authorities as well as the public claim for a complete surveillance of incinerators have caused an increasing interest in continuous emission monitors (CEMs) for mercury. For the potential user of such systems it is important to find a reliable and economic solution. First generation CEMs for mercury were based on the automation of known laboratory methods. This resulted in high maintenance costs, unreliable operation, oversized and heavy construction and last but not least a high price.

A new analytical solution: the SM-3

The operating principle of the SM-3 is based on a completely new technique. Cracking and reduction of bound and ionic mercury contained in stack gas is performed applying the thermo-catalytic method. Wet chemical sample gas treatment using reagents and bubblers is avoided. Maintenance and servicing of the SM-3 are therefore extremely easy. Purchasing costs for purchase and costs of ownership are comparatively low.

As the SM-3 is a compact-sized and low-weight device, it may also be used for mobile applications. Installation is easy and done in a short time.



Figure: SM-3 Mercury stack gas monitor, installed at a cement kiln

Pictures of typical installations of the SM-3

SM-3 Installation at stack
of a municipal waste incinerator
(Bavaria, Germany)

Sewage sludge incinerator (Stuttgart, Germany)

SM-3 Installation inside
protection cabinet
(cement kiln, Germany)

Cement kiln

Cement plant
with installation of SM-3
on top of baghouse

As a leading supplier of high precision analytical equipment, we strive at all times to offer top quality solutions. Our products are manufactured according to the ISO 9001 quality regulations.

Ankersmid M&C bvba,  (32) - 3/820 80 01