SM-3 Mercury Stack Gas Monitor

Continuous Emission Monitor (CEM) for Mercury

Mercury in air and gases

Mercury stack monitors

Mercury laboratory analyzers

Mercury process analyzers

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Detects elemental, ionic and bound mercury

Thermocatalytic principle - no use of reagents

Maintenance-free solid state catalyst

True continuous measurement(no measuring cycle)

3 ranges selectable

Corrosion protected rugged construction

Approved by German Authorities

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The SM-3’s fields of application:

● 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

The SM-3 Mercury Stack Gas Monitor is used forcontinuous monitoring of mercury in stack gas.Bound forms of mercury like HgCl2, HgO, HgS andparticulate mercury are detected as well as ele-mental mercury.

Operating principleA sample gas stream is taken from the duct

through a heated sampling system. The gas isdrawn through a high-temperature particulatefilter and subsequently enters the reduction unit.In this part of the analyzer a thermocatalyticreduction of ionic and bound mercury is perfor-med. Elemental mercury vapor is formed as aresult of this transformation process. The gas isthen dried in a maintenance-free peltier coolerand fed to the mercury detector where the mercu-ry concentration is measured. The high surfacetemperature of the gas entry filter guaranteesthat mercury is thermally completely desorbedfrom particles and thus also detected.

Design featuresAll surfaces coming

into contact with thesample gas are heated totemperatures >180°C toprevent any adsorptionalloss of mercury . The sam-ple line is made of perfluoralkoxy (PFA), a materialwhich shows extremelyweak interaction withmercury vapor. Sampling

and reduction are performed at temperatures farabove the dew point. Therefore no condensate isformed before all mercury is in elemental state.

This minimises signal noise and avoids nonspecificpeaks. The SM-3 does not use any gold collectorfor mercury preconcentration thus giving a veryfast response and providing results continuouslyand in real-time. Possible problems connectedwith "poisoning" of the gold surface are also avoi-ded. The straightforward analysis avoiding wet-chemical sample treatment ensures high reliabi-lity and low maintenance.

Easy to operateThe SM-3 is operated via a waterproof mem-

brane keypad. All inputs required are selected in areadily understandable menu shown on the gra-phical display. Conditions which may lead to amalfunction are detected by sensors and indicatedby a status message provided via relay contacts.

Low maintenance and lowcosts of ownership

Thanks to the new thermocatalytic sample treatment method no reagents are required.Compared to first generation instruments employ-ing wet chemical sample preparation methods,the SM-3 features clearly increased reliability andrequires only minimum maintenance. This resultsin particularly low cost of ownership and maxi-mum availability.

UV-PhotometerQuantitative determination of the mercury

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

SM-3: Installation at a municipal waste incinerator

MERCURY INSTRUMENTS · ANALYTICAL TECHNOLOGIES

Automatic zero adjustmentThe zero line of the SM-3 is checked and adjus-

ted automatically after a preset period of time. Amagnetic valve stops the sample gas stream andswitches over to zero air which has been cleanedin a sulfurized carbon filter. Automatic zero ad-justment is performed every hour and requires 30 seconds.

Automatic calibration checkThe SM-3 is able to perform an automatic span

check at preset time intervals if a suitable calibra-tion gas source (for example from a compressedgas cylinder) is connected to the analyzer.

Automatic self-cleaning filterTo prevent the instrument from being clogged

by dust-particles, the SM-3 has a self-cleaning fil-ter system which is operated by compressed air.The cleaning function is automatically activatedevery hour and is a matter of seconds.

Sampling systemThe sample gas is extracted with a stainless

steel probe and conducted through a heated tubeto the analyzer. The entire sample line is made ofperfluoralkoxy (PFA), a material guaranteeing aminimum memory effect.

The dimensions of the sampling system mounting flange are customized (for example DN 65/PN 6 or ANSI 3"/ 150 lbs).

The importance of continuousmercury emission monitoring

Monitoring of mercury emissions from stackhas become a global issue. More strict regulationsby authorities as well as the public claim for acomplete surveillance of incinerators have causedan increasing interest in continuous emissionmonitors (CEMs) for mercury. For the potentialuser of such systems it is important to find a re-liable and economic solution. First generation CEMsfor mercury were based on the automation ofknown laboratory methods. This resulted in highmaintenance costs, unreliable operation, oversizedand heavy construction and last but not least ahigh price.

A new analytical solution:the SM-3

The operating principle of the SM-3 is based on a completely new technique. Cracking of mer-cury compounds and reduction of ionic mercurycontained in stack gas is performed applying thethermocatalytic method. Wet chemical sample gastreatment using reagents and bubblers is avoided.Maintenance and servicing of the SM-3 are there-fore extremely easy. Purchasing costs and costs ofownership are comparatively low. As the SM-3 is acompact-sized and low-weight device, it may alsobe used for mobile applications. Installation iseasy and done in a short time.

Mercury Stack Gas Monitor SM-3: Flow diagram

SM-3Technical Specifications

Measuring component: total mercury Hg(tot)Measuring principle: thermocatalytic reduction, atomic absorption at 253.7 nmMeasuring range: 0 - 50 µg/m3

0 - 75 µg/m3

0 - 500 µg/m3

Detection limit: < 1 µg/m3

Response time T90: < 60 secondsMeasurement cycle time: none, continuous measurement without time gapsZero drift: < 1 % of range, auto zeroAir supply: oil-less compressed air, approx. 1.5 bar (approx. 22 psi)Operating temperature: 5 - 40 °CPower supply: 230 VAC / 50 Hz (+10% / -15%)Electrical power max. 1000 VA (analyzer) consumption: max. 150 VA/m (sample line)Signal outputs: 4-20 mA (max. load 500 Ohms)

digital status outputs (relais contacts) Dimensions: 550 x 1000 x 700 mm (WxHxD)Weight: approx. 50 kgApproval: Test conducted by German TÜV (Munich),

Report Nr. 24020562/August 1999), published in GMBl 1999/Nr. 33.

Mercury Instruments GmbHAnalytical TechnologiesLiebigstraße 11bD-85757 KarlsfeldTel.: +49 (0)8131 - 50 57 20Fax: +49 (0)8131 - 50 57 22mail@mercury-instruments.de

The Response to an Analytical Challenge:Mercury Instruments.Quantitative trace analysis of mercury has been a challenging task for the analyst until now. We fromMERCURY INSTRUMENTS have made it our job todevelop instruments for mercury analysis of the highesttechnical level. The range of applications for our mercury analyzers is unique world-wide.

www.mercury-instruments.de

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