SETTING THE STANDARD FOR CONTINUOUS EMISSIONS MONITORING AND REPORTING
The recent introduction of EN 17255 has provided a much-needed guarantee of uniformity for the performance of continuous emissions monitoring systems. Christoph Becker, Portfolio Manager for ABB Measurement & Analytics, explains more about the standard and why it marks an important development in reducing industrial emissions.
The growing realization of the need to tackle emissions of potentially harmful pollutants from industrial sources has seen an uptake in the adoption of Continuous Emissions Monitoring systems (CEMS) to help both monitor and control levels and ensure compliance with tightening legislation.
Continuous Emission Monitoring (CEM) is regulated in many regions of the world, with the aim of reducing the emission of pollutants that contribute to poor air quality and lead to signifi cant negative impacts on human health and the environment. For that purpose, reduction commitments have been agreed upon in many regions world-wide in the form of various directives and protocols.
Depending on legislation and the type of information companies require, many industries need to use CEM equipment to monitor their emissions, including power generation, waste incineration, oil and gas, chemicals and petrochemicals, pulp and paper, metals and minerals, landfi lls and biogas, marine and cement production.
Several countries are demanding that polluting facilities and plants install CEMS to meet strict new levels or monitor previously unaddressed pollutants. The Industrial Emission Directive introduced in 2010, for example, places an emphasis on the use of Best Available Technologies (BAT) by companies throughout the EU as a way of reducing emissions of harmful substances to air, water and land that could affect human health and the environment.
Checking CEM accuracy
CEMS solutions are used to quantify levels of pollutants emitted to air. They can range from simple systems monitoring natural gas fi red boilers, measuring gases such as carbon monoxide, carbon dioxide and oxides of nitrogen, to more complex systems set up to monitor large waste incinerators.
In each case, it is important to know that the measurements being taken are correct and can be benchmarked against some form of meaningful standard to allow an accurate and effective comparison of performance against regulated requirements. For example, various standards issued by the International Standards Organization (ISO) and the European Committee for Standardization (CEN) describe performance criteria that must be met by Automated Measuring Systems (AMS) in order to meet maximum permissible measurement uncertainties as mandated in corresponding regulations.
AMS installed in the fi eld are connected to a data acquisition and handling system (DAHS), typically a computer-based system that acquires the measurements together with peripheral data and plant status information.
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)
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.
IET ANNUAL BUYERS’ GUIDE 2022/23
3) Reported descriptive data to demonstrate conformance with legislation, for example, data capture requirements or counts of the number of exceeded limits
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.
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