20 Air Monitoring - CEM 2014 Preview
Emission Monitoring with Set CEM CERT A Modularised and EN 15267-3 Approved CEMS Solution Concept
emitted by power plants, boilers, gas turbines, furnaces, incineration plants, chemical plants, etc. The certifi cate is the basis for acceptance in all EU member states, and due to the modular concept of Set CEM CERT the system can be applied to various emission monitoring tasks.
Protection of the environment and human health is a major concern for the European Union. Beside the establishment of different directives (WID, LCPD, IPPC) for the industry, performance criteria and test procedures for automated measuring systems (AMS) have been put in place under EN15267-3. The Siemens Set CEM CERT system has been certifi ed by TUEV Sued in Germany for fulfi lling these requirements. Set CEM CERT is used for continuous monitoring of NOx
, SO2 , CO and O2 in stack gases
Another important benefi t of Set CEM CERT is the high variety of different measuring ranges, which have been tested and approved.
Measurement Techniques
The stringent requirements of the European Commission require a very high performance for CEMS (continuous emission monitoring systems). The emission limit values (ELV’s) are becoming lower and hence the performance of the measurement equipment is becoming more important. CEMS can mainly be divided into two categories: extractive or in-situ. Set CEM CERT (Figure 1) is based on so called “cold-extractive” technology. A heated sample probe with a fi lter element continuously extracts a sample, after which the heated sample line transfers the sample to a compressor gas cooler, where the moisture content is taken out. The dried gas can then be measured by dedicated analysers. One of the benefi ts of this cold-extractive technology is that no moisture measurement is required, since the measurement is already based on dry base, as required by the according directives. The components NO, SO2
and CO are determined by a non dispersive infrared (NDIR)
by Rudi Spinner Siemens AG Industry Sector
Industry Automation Division Sensors and Communication
I IA SC PA PRM 4, Siemensallee 84 76187 Karlsruhe, Germany Tel: +49 721 595-5359 Fax: +49 721 595-2525 Mobile: +49 172 5708683
Email:
rudi.spinner@siemens.com Bob Lane
Business Manager - Process Analytics NWE RC-GB I IA&DT IA SC PA Siemens Industry GB&I
Bridgwater Road, Worcester, WR4 9ZQ, UK Tel: +44 (0)7788 498078
Email:
bob.lane@
siemens.com IET March / April 2014
www.envirotech-online.com
analyser (ULTRAMAT 23). For lower emission limit values, gas turbine emission monitoring applications, for example, a non dispersive ultraviolet (NDUV) analyser (SIPROCESS UV600) can be chosen as an alternative. Due to the fact that the emitted gases need to be referenced to a certain oxygen level, an oxygen measurement is required as well, which is offered with either a paramagnetic or electrochemical cell placed in the ULTRAMAT 23.
As mentioned in the preface, there were many test procedures that had to be conducted to the Set CEM CERT during the certifi cation process, in the laboratory as well in the fi eld under real process conditions. Test procedures included checking of parameters such as calibration function, response time, linearity, maintenance interval, zero and span drift, availability, reproducibility, NO converter effi ciency, sample fl ow rate, infl uence of vibration and, probably most importantly, the infl uence of specifi ed disturbing and interfering components. Out of the results from lab and fi eld tests the total uncertainty is calculated and listed in the EN 15267-3 certifi cate.
Before and during the purchase process of Set CEM CERT the operator is required to establish and implement data and information required by EN 14181 in order to assure the quality of the CEMS. The quality assurance process is classifi ed into three different quality assurance levels (QAL’s): QAL 1, QAL 2 and QAL 3. In addition to the QAL-3 step there is an Annual Surveillance Test (AST) to be conducted. AST can be considered as a minor scale of the QAL 2 tests.
Unique System Features
During the fi eld tests of Set CEM CERT according to EN 15267 the infl uence of each component had to be examined as a whole.
For example, it has to be taken into account that SO2
(sulphur
dioxide), which is formed when sulphur within the fuel reacts with oxygen, is very water soluble. Due to the cooling of the wet gas in the cooler down to +5°C dew point, the moisture content in the stack gas forms condensate, which then can be removed by peristaltic pumps. If this precaution is not taken, a signifi cant loss of SO2
due to the water solubility in the condensate takes place at low concentration levels. Set CEM CERT offers a solution to prevent this loss of SO2
. An acidifi cation module
establishes a suffi cient acidic environment inside the cooler’s heat exchangers in order to replace the water condensate with weak acid. Due to the acidic environment, the solubility of acidic and water
Figure 1: SetCEM CERT panel layout
soluble gases is minimised to a negligible extent. A very suitable acid for this purpose is diluted ortho-phosphoric acid (H3
PO4 ),
which is injected in front of the primary cooler by a peristaltic pump. All the diluted ortho-phosphoric acid solution mixed with condensate is consecutively removed as acid condensate from the bottom part of the cooler by another peristaltic pump. The acidifi cation module (Figure 2) is recommended when measuring SO2
or NO2 ranges less than 0-150 mg/m3 gas turbine applications.
Another important benefi t of Set CEM CERT is the high variety of different measuring ranges, which have been tested and approved. In case of SO2
is 0-7000 mg/m3 the largest range which can be applied . Furthermore, the modular package allows the
certifi ed use of system components from two different leading European manufacturers, thus keeping the number of spare parts in stock to a reasonable amount. Up to two different analysers with different measuring ranges can be confi gured in the Set CEM CERT, and versions for both indoor and outdoor installation are available. When using electric heaters or cabinet air conditioners the ambient temperature application range can be extended according to the local requirements.
concentrations, which has a similar behavior to SO2 . Therefore, Set CEM CERT can be
, in
used as an EN 15267 approved system for emission monitoring in cases where low SO2
concentrations have to be measured, such as
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