Annual Guide 2023 I SOURCE TESTING ASSOCIATION
The raw data is then processed and compared with Emission Limit Values (ELV), which set the maximum permissible limits for the concentration of measured waste gases, for example from a power or industrial plant, which can be emitted within a given period. Using this data, an emissions report is then drawn up which forms the basis for operating permits issued to companies.
While AMS provide a good indication of whether a plant is exceeding its permitted ELV targets, it has been diffi cult to achieve uniformity both in the way that DAHS calculate results and are maintained due to the absence of a single guiding international standard.
Until recently, there has been no international DAHS standard available that specifi es the conversion of data from an AMS to reported data, has performance and test criteria for a type test that allows manufacturers to certify their DAHS and mandates QA/QC procedures. That means pollutant concentrations calculated are dependent on the algorithms installed by DAHS manufacturers interpreting the sparse information made available. As a result, emissions reported are a question of the algorithm implemented and therefore data reported is prone to differ from DAHS supplier to DAHS supplier.
The absence of anything to ensure uniformity has contradicted the idea of manufacturer-independent documentation of emissions, or excess emissions.
The fi gure below uses fi eld data taken from an AMS to illustrate the potential differences in emissions calculations that can arise when different algorithms are applied.
Setting the standard -
introducing EN 17255 The European CEN/TC 264 Air Quality handles the Data Acquisition and Handling System (DAHS) standard EN 17255. It is a series of standards which govern the process for the quality assurance and control of DAHS. Properly titled EN 17255 - Stationary source emissions - Data acquisition and handling systems, the standard unifi es calculations, identifi es performance specifi cations, sets requirements for certifi cation and has QA/QC requirements to ensure that DAHS deliver comparable emission concentrations, and lead to comparable emission reports.
EN 17255 plugs the gap left by EN 14181 Quality Assurance of Automated Measuring Systems, a European standard that covers certifi cation, calibration, testing and performance of AMS commonly known as CEMS, which had explicitly left open the requirements for DAHS.
The new EN 17255 standard consists of four parts, with parts 1 to 3 already published and part 4 published as a draft. Part 1 specifi es the requirements for handling and reporting data and is the most fundamental as it describes the conversion of raw AMS data to a DAHS report.
It defi nes three types of data:
1) First Level Data (FLD), which is the lowest level data and the basis for calculations
2) Reported emission data, which states short- or long-term averages required by legislation to compare against legislative limits, for example, the European Industrial Emissions Directive, or for entry into reporting registers like the European Pollutant Release and Transfer Register (E-PRTR)
3) Reported descriptive data to demonstrate conformance with legislation, for example, data capture requirements or counts of the number of exceeded limits
Both curves show a pollutant corrected for oxygen (O2). The dark blue curve shows correction based on half-hourly averages, whereas the lighter blue curve shows the correction based on minute-by-minute values.
Both curves show similar values except for the two peaks, but both peaks show a signifi cant difference, with the potential to cause different results compared to the daily Emission Limit Value after averaging.
Part 2 specifi es the elements of a DAHS and performance requirements regarding the implementation of procedures for data acquisition, input data processing, reported data, reports, data storage, system functions and end-user documentation.
Part 3 specifi es the testing procedures, description of laboratory tests and requirements of the testing laboratory to produce a test report, which then gives the DAHS manufacturer the opportunity to apply for a certifi cate according to EN 15267 Air quality - Certifi cation of automated measuring systems part 1 and 2.
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