ENVEA - Model AMESA - Dioxin Monitoring System
From Dioxin Monitoring
Traditionally, the monitoring of pcdd/fs is achieved by taking 1–3 short-term samples per year (each of 6 hours). However, over the past 10 years it was discovered that especially during start-up and shut-down periods of (state of the art) incinerators the dioxin emissions in the flue-gas can increase compared to normal operation up to factors of 1000 in raw gas and after bag-filters. Another study quantified that around 60 % of the yearly dioxin emissions of a plant are produced and emitted during one start-up. These findings revealed and demonstrated that dioxin and POPs emissions of incinerators cannot be reliably monitored by manual short term sampling since such spot measurements represent only 1–2 ‰ of the yearly operating time of the plants during normal operating conditions.
The AMESA system, approved in 1997 by TÜV Rheinland (Germany), in 2005 by MCerts (UK) and in 2006 by ETV EPA (United States), is designed for the long-term sampling of dioxins (PCDD), furans (PCDF) and other Persistant Organic Pollutants (POPs).
By permanent sampling over a period of up to 4 weeks, AMESA ensures continuous documentation of dioxins/furans emission for each single sample, thus ensuring that fluctuations in plant operation and in the composition of the fuel are well recorded.
The Long Term Dioxin Sampler AMESA can be used, for example, in refuse incinerators, hazardous material incinerators, medical waste burners, cement kilns etc.
The sampling method is also suitable for other sampling applications like e.g. heavy metals, mercury or fine dust (PM10, PM2,5).
Uses the well-known adsorption method
Information on monthly, 2-weekly or weekly mean value of dioxin/furan emissions by analysis of mixed sample (XAD-II cartridge) in laboratory
Additional information on flue gas velocity, sample gas flow volume, flue gas and cartridge temperature as half-hourly average. Optional up to 4 informations like e.g. O2, CO2, CO, HCl, dust etc. can be recorded and saved half-hourly average.
No collection of condensate and none of the associated handling problems during monitoring over long periods. Broadly based measuring range for dioxin/furan concentrations between 0.0001 and 10 ng/m³ (as TE to NATO CCMS model).
Sampling period between 6 hours and 4 weeks possible.
The AMESA system uses the “simplified” cooled probe method which was designed more than 20 years ago. The target was to have an easy handling sampling method in which the organic pollutants (e.g. PCDD / PCDF) of all three physical conditions (gaseous, solid, liquid) are adsorbed in only one adsorption cartridge. Contrary to the other existing methods, this has the big handling advantage that only 1 part (adsorber cartridge) has to be exchanged and to be sent to the dioxin laboratory.
This method, the most practical for long-term sampling of dioxins, combines the advantages of the cooled probe method of EN 1948-1 and the US EPA method 23A.
The other methods described in EN 1948-1 (cooled probe, filter-cooler) produces condensate which has to be collected and analysed.
According US EPA method 23A the collected condensate does not need to be analysed, because it is well known that the amount of dioxins in the condensate is negligible. This was confirmed with AMESA in a lot of measurements in which the condensate was collected and analysed separately.
In the filter-cooler method the sampling probe is heated: this leads to a higher risk of deposits of dioxins in the sampling probe in comparison to the cooled probe method in which the sampling probe is flushed already by the condensate generated in the sampling probe.
The use of the dilution method have also a higher risk of dioxin deposits inside the heated probe. Additionally, there is the risk that dioxins from the dilution air are injected into the system. Therefore a second dioxin adsorber has to be installed always in the dilution air supply.
The operating principle of AMESA sampling system is as follows:
A cooled probe (less than 50°C) is used to extract a part of the flue gas isokinetically from the stack. Dioxins and furans which are combined in the gas, the dust and the condensate of the flue gas are adsorbed in a specific cartridge filled with XAD-2 and quartz-wool.
An automatic leakage test is performed before and after the sampling cycle to validate the non-contamination of the adsorbing cartridge.
After adsorption, the measured gas is pumped through a flexible tube to the control cabinet, where the gas is cooled down (The dried measured gas flow is determined twice by means of a calibrated gas meter and a thermal mass flowmeter.
AMESA operates fully automatically and all necessary data are stored internally and on a removable SRAM card. Both the XAD-2 cartridge and the SRAM card are to be sent to a specialized laboratory for further analysis of PCDD/PCDF.
The new AMESA can be equipped with 4 sampling units, thus allowing successive automatic sampling of different pollutants (dioxins, heavy metals…) on the same stack, or multiplexing on different stacks (max. 4).
Since 1996, more than 150 AMESA were installed in over 14 countries. Applications were realized in:
- Domestic waste incinerators
- Hazardous waste incinerators
- Hospital waste incinerators
- Incinerators for slaughterhouses
- Biomass power generation plant
- Cement kilns
- Power plants
- Metal smelters
- Sulphuric acid production plants…
Currently two certifications for long-term sampling systems are available in Europe: MCERT’s and TÜV.
Since 1999 a complete network of more than 50 AMESA units for dioxin / furan (PCDD / PCDF) stack emission control has been installed throughout Belgium.
In the Walloon region, 12 dioxins testing units were installed in 4 domestic waste incineration plants.
The ISSeP, the Public Scientific Institute in charge with dioxin monitoring has therefore a setback of nearly 10 years of continuous sampling of dioxins with 12 AMESA systems installed with over 2,200 samples collected.
All long-term monitoring results are published on the internet homepage of the region.
Over the years, the continuous measurement of dioxin and furans showed that some plants occasionally exceeded the limit values while some others fulfilled the low emission requirements to a very high degree. But today, based on the measurement results, the contribution of public waste incinerators represents less than 1% of total emissions of dioxins known in the Walloon Region.
This shows how AMESA can successfully help to reduce the PCDD/PCDF emissions in an effective way.