The emission of mercury into the environment is now of global concern because of its high toxicity, bioaccumulation and long range atmospheric transport.

It is estimated that over half the mercury emissions to the atmosphere are caused by combustion processes. (Further information is available from the EPA website). The majority are caused by the burning of fossil fuels for power generation but significant amounts are produced from waste incineration, crematorium and smelters.

Mercury is emitted from combustion processes in three forms: (1) elemental mercury Hg⁰, (2) oxidised mercury Hg^II and (3) particulate mercury Hg^P.

The oxidised and particulate forms of mercury have a relatively short atmospheric residence time and affect the area closer to their source but elemental mercury can stay in the atmosphere for times varying from 8 to 16 months and consequently can be wind transported over vast distances with consequent global environmental impact. Mercury continuous emissions monitors are increasingly used at any industrial plant which uses combustion technology and produces significant mercury emissions.

The P S Analytical range of mercury CEMs is designed to handle any application. The system consists of three basic modules (click here) which allow the systems to be built to specific user requirements, which can be summarised as Full scale plant monitoring, pilot plant monitoring or lab scale monitoring.

Full scale plant systems need to be able to handle harsh operating conditions with minimal operator attention. Lab scale systems conversely need more operator attention and have to be able to be handle rapid changes in operating conditions set up.

Pilot plants can vary in size from just above lab scale to full scale plants so analyser requirements can vary greatly.

We describe systems for full scale plants here with recommendations for pilot plant and lab systems on application from our sales department.

The Mercury CEM Analyser

The PSA mercury CEM analyser contains the PSA 10.525 Sir Galahad mercury monitor. Mercury vapour generator, stream selector valves, industrial PC and controllers all mounted in an enclosed monitor cabinet with calibration kit.

All of the analysers have the following capabilities:

• Detection Limit of 0.01µg/m³

• Linear range of up to 3000µg/m³ (without dilution).

They can be configured to any specific customer requirement (however certain configurations are frequently requested and these are described below).

PSA 50.100

PSA 10.665

PSA 10.680

The PSA 50.100 dedicated online CEM analysers for measuring total mercury stack emissions and can be used as a dedicated compliance monitor.

The PSA 10.665 is the standard CEM analyser for measuring both total mercury and speciation levels from mercury removal unit’s outlets and /or inlets. This unit is available with 4 or 8 valves.

The PSA 10.680 CEM analyser is designed to give the power of the PSA 10.665 analyser with the flexibility of a more portable unit and thus can be used as a general purpose monitor or for pilot plant studies.

The Sample Conditioner

This unit is used either to ensure that all the mercury present in the sample is converted to elemental mercury or to measure oxidised mercury in addition to total mercury. This unit can be mounted close to the probe or next to the analyser depending on the amount of access at the sampling point.

There are different options depending on the application. These are:

The PSA S123C300 Conditioner is the standard conditioner with thermal catalyst for measuring total mercury.

The PSA S123C200 Conditioner includes an adsorber tube which selectively removes oxidised mercury as well as the thermal catalyst which allows for measurement of total mercury and oxidised mercury. 

The Probes

The type of probe is fitted with an appropriate stinger, usually about 1.8 -2metres in length (depending on the plant diameter at the sampling point), and will vary depending on the ash content of the sample.

PSA offer a number of probes, some of which are fitted with integral sample conditioners.

The most frequently used are:

The PSA 50.125

Inertial dilution probe is used upstream of particle control devices where high quantities of ash and high temperatures are normal. An optional mercuric chloride generator can be fitted to the probe for recovery and validation studies.

The PSA 50.104

Fast track sample dilution probe is used typically down stream of control devices where the ash content of the sample is considerably lower.

Sample Lines

Heated Teflon sample lines are used to transfer the gas sample from the probe to the sample conditioning unit. Length required must be stated.

Since 1996 PS Analytical has sold in excess of 50 Hg in stack gas analysers which have been used to test in excess of 250 power plants worldwide.

These are installed on sites using various fuel types producing different stack gas compositions.

They are also located within plants to measure the different processes including upstream and downstream of particulate removal devices (ESP, bag-houses), deNOx units, wet/dry scrubbers and flue gas. More than 90% of these installations use the Hg CEM for speciation measurements to establish the efficiency of the control technology.

If you have any specific questions, would like to discuss your individual requirements or need more detailed information on any of the above products please return the Information Request Form.