Gasmet Continuous Mercury Monitoring System (CMM) provides a complete automatic system for continuous mercury monitoring, certified TÜV and MCERTS (QAL1).
Gasmet’s CMM has successfully completed the EN15267-3 testing with the world’s lowest EN15267 certified range (0 to 5 µg/m3) for measurements of mercury.
This makes the Gasmet CMM system future-proof for declining emission limits.
Gasmet CMM consists of:
- Dilution probe
- Heated sample line
- Gasmet mercury analyzer
- Gasmet test gas generator
These instruments are integrated in an air-conditioned cabinet.
The Heated dilution probe with a two-stage blowback system ensures the durability and low maintenance of the system even in demanding conditions.
The sample gas is extracted from the process duct with a dilution probe and a heated sample line specially designed for sampling mercury from harsh process conditions.
The analyzer has a detection limit of 0.025 µg/Nm3 and the lowest measuring range for total mercury concentration of 0 – 5 µg/Nm3.
Mercury is a sticky compound and it may easily absorb into dust and accumulate in the sample lines and probe filters which can result in analyte loss and increased response time of the analyzer. Therefore, the Gasmet CMM is equipped with:
- a smaller filter element, which minimizes the amount of dust deposition on the filter,
- and a two-stage blowback mechanism which first removes dust from the filter element and then in the second stage expels the dust from the probe tube back into the process.
The Gasmet CMM’s automatic calibrations are actioned at user defined intervals. System settings can be accessed from the easy-to-use Mercury Analyzer User Interface (MAUI).
Gasmet CMM has excellent annual availability and TES provides technical service and support.
The system has been field tested in a variety of industrial applications such as coal-fired power plant, hazardous waste incinerator, sulphuric acid plant and cement plant.
CVAF provides the highest sensitivity
Gasmet mercury analyzer is based on Cold Vapor Atomic Fluorescence (CVAF) measurement principle, which offers the highest sensitivity in the world.
Measurement uncertainty in traditional analyzers increases by the presence of moisture and oxygen which reduces the fluorescence signal from mercury in the sample. Gasmet has avoided this ‘quenching effect’ in the CMM by developing a dilution sampling approach.
By lowering the concentration of interfering gases, the quenching effect is avoided, but with the CMM’s extremely low detection limit, the sensitivity of the mercury measurement is unaffected.
Thanks to the CVAF technology and Gasmet design, continuous and precise measurement with no need for sample pre-concentration is achieved.
The integrated thermal converter converts all mercury compounds to elemental mercury to measure total gaseous mercury. The converter is directly connected to the fluorescence cell to prevent recombination reactions, where atomic mercury converts back to oxidized forms.
Gasmet CMM is designed for continuous measurement of mercury from hot, wet and corrosive gas streams. The system is used in a wide range of industrial processes requiring mercury emissions monitoring. Continuous mercury monitoring is generally a regulatory requirement for waste incineration plants, power plants and cement kilns.
Thanks to the high sensitivity and selectivity of CVAF measurement technique, CMM is well suited for many different emission monitoring applications even with extremely low mercury concentrations. The Gasmet CMM has been granted the lowest EN 15267-3 certified range in the world (0 – 5 µg/Nm3).
Contact TES if you have a need to measure total gaseous mercury – we’ll be happy to help you in finding the best solution for your needs.
BACKGROUND to Mercury Monitoring
The heavy metal, Mercury (Hg), commonly known as quicksilver occurs naturally in rocks and coal, in forms such as metallic mercury and organic and inorganic mercury compounds.
Exposure to Mercury can affect foetal neurological development, and high levels of mercury in blood have been linked to lowered fertility, brain and nerve damage, and heart disease in adults.
In liquid form, mercury readily vaporises and is released into the air, where it is transported and deposited globally. It can bioaccumulate in, and biomagnify up the food chain, especially in the aquatic food chain where it constitutes a major threat to global food security.
Even at low concentrations, mercury poses a risk of causing adverse effects to human health and the environment. and continuous mercury monitoring is becoming more and more relevant.
The largest sources of anthropogenic mercury emissions are:
- Mining industry
- Coal combustion
- Cement production
- Waste incineration
Awareness for the need to measure mercury is growing.
The Minamata Convention on Mercury is a multilateral environmental agreement that addresses that sets out practical actions to protect human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds. It requires Parties to address mercury throughout its lifecycle, including:
- use in products and processes
- unintentional release from industrial activity
- contaminated sites, and
- long-term storage.
Australia signed the Minamata Convention on 10 October 2013 and is now considering ratifying the Convention to become a full Party to it. This will allow Australia to participate and influence decisions on issues addressed under the Convention. The treaty entered into force on 16 August 2017, 90 days after 50 countries have ratified, with the first Conference of the Parties to take place from 24 to 29 September 2017 in Geneva, Switzerland.
As ratification of the Convention would legally bind Australia to the Convention’s obligations, a detailed assessment process will be conducted, with the preparation of a National Interest Analysis and a Regulatory Impact Statement. Ratification will then be considered by the Joint Standing Committee on Treaties before a final decision as to whether Australia will ratify the Convention is made by the Australian Government.
Industries, especially those burning coal, oil or waste, need to monitor their mercury emissions.
All measuring techniques need to be able to tackle the challenges mercury monitoring presents.
Mercury can occur in various forms and can even be bound to dust particles. Flue gas includes elemental mercury Hg0 and oxidized mercury Hg2+ in the form of HgCl2. As most measurement methods are based on measuring elemental mercury, it means that the oxidized mercury compounds must be converted to elemental mercury.
Methods of measuring mercury
- Cold vapor atomic absorption spectroscopy CVAA
- Cold vapor atomic fluorescence spectroscopy CVAF
- Differential Optical Absorption Spectrometry DOAS
- Sorbent Trap method (non-continuous)
CVAA, CVAF and DOAS are all measurement technologies used in certified systems. Selecting the right technique depends on your analytical needs. The choice of analyzing method may also be determined by regulatory compliance. Therefore, it is vital to check which regulatory methods you need to comply with when choosing a mercury analyzer.
Technical Properties to Consider
- Most continuous mercury measurement methods are based on measuring elemental mercury. This means that the oxidized mercury compounds must be converted to elemental mercury before the measurement. It must be ensured that none of the mercury compounds are lost before the conversion, and that there is no recombination of mercury compounds afterwards. Therefore, placing the converter right before the sample cell is important.
- Mercury concentrations are extremely low compared to other emission gas compounds. The concentrations are generally few µg/m3 in waste incineration and power plants. These extremely low concentrations naturally require that the measurement technique has low detection limits. It should be noted that depending on the plant or process, there can be relatively high concentrations of mercury from time to time. Because of occasionally varying concentrations of mercury, the measuring system needs to be able to withstand and detect the Hg peaks as reliably as the lower concentrations.
- Other features expected from mercury monitoring systems are low cross-sensitivity and stable calibration check routines. Cross-interference effects need to be minimized especially as the mercury concentrations are very low compared to other gases in the stack gas. The quality of the measurements can be tested with frequent calibrations and checks. Check routines are preferred to be automatic and adjustable by the user if needed.
Continuous or Non-continuous Emission Monitoring
Continuous monitoring is a particular advantage where abatement systems can be adjusted according to the mercury levels in the plant emissions. Where flue gas treatment is used to achieve lower mercury emissions, continuous monitoring data can be used for example to optimize sorbent injection rates.
Non-continuous methods do not provide sufficient insight for process control. In addition, by measuring process emissions over a short period of time, non-continuous methods risk failing to provide sufficient information on the variability of mercury emissions over time and between differing feedstocks.
In general, the key requirements of a mercury monitoring system are as follows:
- measures mercury continuously
- measures total gaseous mercury
- measures at low levels with high sensitivity during all process conditions
- measures excursions to higher concentrations
- low cross-interference from gases such as Sulphur dioxide
- no analyte loss or other sampling issues in high dust loading
- stable calibration and simplified calibration check routine
Gasmet Continuous Mercury Monitor (CMM) meets these requirements.