Continuous emission monitoring in power stations and combined heat and power plants

Transcription

1 Ref : 02003Ren Continuous emission monitoring in power stations and combined heat and power plants... Thermal Generation Study Committee...

2 The Union of the Electricity Industry - EURELECTRIC, formed as a result of a merger in December 1999 of the twin Electricity Industry Associations, UNIPEDE 1 and EURELECTRIC 2, is the sole sector association representing the common interests of the European Electricity Industry and its worldwide affiliates and associates. Its mission is to contribute to the development and competitiveness of the Electricity Industry and to promote the role of electricity in the advancement of society. As a centre of strategic expertise, the Union of the Electricity Industry - EURELECTRIC will identify and represent the common interests of its members and assist them in formulating common solutions to be implemented and in coordinating and carrying out the necessary actions. To that end it will also act in liaison with other international associations and organisations, respecting the specific missions and responsibilities of these organisations. The Union of the Electricity Industry - EURELECTRIC is also the association of the Electricity Industry within the European Union representing it in public affairs, in particular in relation to the institutions of the EU and other international organisations, in order to promote the interests of its members at a political level and to create awareness of its policies. The reports published by EURELECTRIC are the result of the work of its structure of expertise: they represent one of the most direct methods of circulating knowledge and information throughout the sector, on subjects of common interest. They are intended for wide circulation both within the electricity supply industry and outside it. Please do not hesitate to ask for the latest available printed EURELECTRIC publications catalogue (with summaries of EURELECTRIC reports) from: Union of the Electricity Industry EURELECTRIC Documentation 66 Boulevard de l'impératrice BE-1000 Brussels BELGIUM Tel: Fax: cpalermo@eurelectric.org You can also use the EURELECTRIC Internet Web site, which provides the following information: - EURELECTRIC general information - EURELECTRIC positions and statements - Events & Conferences - Publications Catalogue 1 International Union of Producers and Distributors of Electrical Energy 2 European Grouping of Electricity Undertakings The Union of the Electricity Industry EURELECTRIC has been formed through a merger of the two associations and

3 TABLE OF CONTENTS EXECUTIVE SUMMARY...1 ACRONYMS...4 ACKNOWLEDGEMENT INTRODUCTION BACKGROUND OBJECTIVES IMPLEMENTATION REASONS FOR CONTINUOUS EMISSION MONITORING DEVELOPMENTS IN MONITORING WORK BY UTILITIES TECHNICAL ASPECTS OF CONTINUOUS EMISSION MONITORING EXTRACTIVE CEM IN-SITU CEM PERFORMANCE CRITERIA DETERMINATION OF MASS FLOW MEASUREMENT AND PEM REPORTING EXPERIENCE WITH CEM EXTRACTIVE CEM IN-SITU CEM ACCURACY Uncertainties of the Measurement Systems Experience with accuracy reported in the different countries REPORTED EXPERIENCE OF A GENERAL NATURE INVESTMENT AND OPERATING COSTS GENERAL DISCUSSION...27 LIST OF TABLES pag e TABLE 1 National and regional criteria for CEM... 4 TABLE 2 Extractive sampling principles reported for the different flue-gas components in each country TABLE 3 In-situ principles reported for the different flue-gas components in each country14

4 EXECUTIVE SUMMARY The necessity for Continuous Emission Monitoring (CEM) for process and emission control of combustion plants is increasing in line with the increased automation of new plants and additional regulatory requirements. This report presents experience and trend information from utilities regarding continuous emission monitoring (CEM) at power and Combined Heat and Powr (CHP) production units in Europe. Topics covered include; reasons for installations, experience and future expectations of the quality, performance, long-term availability and costs of CEM installations. The following components are covered; NO x, SO 2, CO, dust, "secondary" flue-gas components (mainly NH 3 ) and the continuous monitoring of flue-gas velocity. Most of the experience comes from those utilities represented in the UNIPEDE-THERNOX group. Other utilities in these countries may therefore have differing experiences. It has also been difficult to collect all the relevant experience for some of the countries. The most important trend apparent is the increasing requirement for CEM measurements, driven particularly by new requirements of the regulatory authorities. The utilities have performed many investigations into CEM and its advantages. CEM is consequently used not only for control of the environmental performance of a plant but also (particularly in the case of NO x, CO and dust) for optimisation and control of the operation of the plant. Existing and new plants continue to be fitted with emission control measures such as low-no x burners and deno x. An increasing number of CEM installations are therefore required, not only for measurement of NO x for deno x process control, but also for measurement of NH 3 slip when using SNCR. CEM is also widely used in Sweden for the determination of fees and taxes for NO x and SO 2 emissions respectively. Continuous emission monitoring can be done with either extractive or in-situ systems. The use of extractive CEM to date has greatly exceeded that of in-situ CEM. A trend towards greater use of in-situ systems is now becoming apparent on the market. The experience reviewed in this study shows no definite trends for choice of extractive or in-situ CEM, both have been applied successfully in many countries. The sampling principle of most of the extractive CEM systems is based on extraction of flue gas with condensation of water vapour - all countries in this study have reported experience of this sampling principle. There are, however, also some countries that have reported experience of extractive sampling systems with dilution and/or heated extractive systems. The reported experience with CEM based on extraction with condensation is better than that of CEM based on extraction with dilution or heated extractive CEM. The most common in-situ CEM method is single point measurement with a probe, but many in-situ CEM systems measure across the duct. Most countries in this study have experience with both types of in-situ CEM. The most common analytic principles for CEM are IR/UV-absorption. Extractive based CEM mostly uses NDIR or NDUV while the in-situ systems also use differential optical absorption spectroscopy (DOAS) or IR/UV-absorption. Electrochemical cell-based methods could be used for both extractive and in-situ systems. In-situ CEM systems for the measurement of dust are mostly based on opacity. A common practice in extractive CEM for 02003Ren9771 1

5 NO x is the use of converters for the reduction of NO 2 followed by analysis for NO to determine total (NO + NO 2 ). Manufacturers of extractive CEM in Europe reported in this study include; Hartmann & Braun, ADC, Siemens, Rosemount, Bodenseewerk and Maihak. ADC produces CEM based on extraction with dilution while the remaining manufacturers mainly produce extractive CEM with condensation. Bodenseewerk also produce heated extractive CEM. Manufacturers of in-situ CEM in Europe reported in this study include; Lear Siegler, SICK, OPSIS, Codel, Land and Durag. SICK, Codel and OPSIS mostly measure across the duct while Lear Siegler and Land use in-situ probes. The reported experience (accuracy, performance, long term availability, operating costs etc.) with extractive and in-situ CEM systems show no major differences. The main advantages with in-situ CEM are the removal of the need for sample conditioning and the fact that it is possible to measure components, such as NH 3 and NO 2, that otherwise are partly or totally removed during sample conditioning. A number of plants are equipped with SNCR-systems and accurate measurement of the NH 3 slip is therefore useful. Measurement of NH 3 with insitu CEM can easily be combined with measurement of NO x and/or SO 2. A disadvantage of most in-situ systems is the problem of calibration on a regular and routine basis. Extractive CEM, on the other hand, is very easy to calibrate. It takes time and due care to apply CEM in daily operation with adequate accuracy. In general there have been few problems with extractive CEM. Almost all difficulties reported relate to the sampling and calibration systems. Condensate management requires careful attention if problems are to be avoided. Maintenance requirements can be high unless the system is carefully designed with e.g. provision for back purging of probe filters. Although low levels of maintenance are reported concerning in-situ CEM it is clear that there is a need for a minimum level of essential maintenance e.g. cleaning of windows and checking of optical path alignment. It is not possible from the survey to recognise any clear trend regarding the performance and availability of CEM systems. It is clear from many responses that some calibration systems pose problems and require further attention. A common difficulty appears to be the quality and reliability of calibration gas standards. The accuracy of gaseous emission concentrations in flue gas is expected to be high if calibrations are performed carefully and with certified calibration gases or calibration cells. One reported experience from an accredited laboratory is that the deviation between a stationary CEM and a mobile extractive CEM in most cases is below 4% of the measured values. The accuracy of dust CEM, especially at low concentrations, is low though. The accuracy of yearly emission depends also on uncertainties in fuel flow and mass flow calculation. A study on three coal fired power plants reports +/- 5 to 11 % uncertainty for NO x -emission and +/- 25 to 30 % for SO 2 -emission at low concentrations after FGD (mainly due to concentration gradients in flue gas ducts and single point measurement). In most countries measurements are made at a single location (extractive CEM or single point in-situ probes) which is often determined by grid testing. Most analysers are provided with systems for automatic calibration. There are also purge air systems to clean the measurement windows (in-situ CEM). In most of the countries, performance criteria for CEM have been 02003Ren9771 2

6 established. Only in Germany (and anticipated in Ireland) does a standard approval system for the CEM instruments exist. The mass flow are mostly calculated from the measured concentrations in conjunction with the fuel consumption, the excess air level and the fuel analysis and seldom from the measured concentrations and the measured flue gas velocity. In the future it is possible that other flue gas components will be measured more widely and other analytic technologies used. Typical examples of such components are NH 3 and N 2 O for process optimisation. FTIR and diode laser are example of new measurement techniques coming into use. It is also very possible that existing analysers will be developed further and their availability and performance improved the electrochemical analysis principle is an example of such an technique. In some countries Predictive Emission Monitoring (PEM) has been tested for the determination of NO x emissions. A PEM system can be verified by multivariate data analysis or based on predictions by neural network. The plant must be fired with fuels of constant quality if a PEM system is to be used Ren9771 3

7 ACRONYMS AFNOR - French Standards Organisation. BEES - Besluit Emissie Eisen Stookinstallaties: Ordinance on Emission Limit Values for Combustion Installations in the Netherlands. BS - British Standard CEM - Continuous Emission Monitoring. Chemiluminescense - detection based on the luminescense reaction of NO with O 3. DOAS - Differential Optical Absorption Spectroscopy. EPA - Environmental Protection Agency. FGD - Flue-gas desulphurisation (deso x ). FTIR - Fourier Transformed Infra-Red. Extractive CEM - The analysis takes place outside the flue gas duct. HMIP - Pollution Inspectorate (United Kingdom)- now part of the UK Environment Agency. In-situ CEM - The analysis takes place inside the flue gas duct. IR-absorption - Infra-Red absorption. The analysis principle is based on the transmission of characteristic wavelengths in the infra-red spectrum. LCPD - Large Combustion Plant Directive of the EC (88/609/EEC). NDIR - Non Dispersive Infra-Red. NDUV - Non Dispersive Ultra-Violet. PDA - Photo Diode Array. PEM - Predictive Emission Monitoring or (Parameter Monitoring). PEN - National Energy Plan (Spain). SCR - Selective Catalytic Reduction (deno x ). SEPA - Swedish Environmental Protection Agency. SNCR - Selective Non-Catalytic Reduction (deno x ). TA-luft - Technical rules that prescribe the required conditions for CEM in Germany. TÜV - Technischer Überwachungs-Verein, Organisation of Technical Inspection Agencies in Germany. The required conditions for CEM are defined by TA-luft and verified by (TÜV) test laboratories. USEPA - US Environmental Protection Agency. UV-absorption - Ultra-Violet absorption. The analysis principle is based on the transmission of characteristic wavelengths in the ultra-violet spectrum. ACKNOWLEDGEMENT In addition to the authors, the following persons have made major contribution to the report; Mr. Brendan BARRY - ESB (Electricity Supply Board) Mr. Roland CSADER - Badenwerk AG Mr. Mark ELSWORTH - National Power PLC Mr. Daniel MAILLIET - EDF (Electricite de France) Mr. Henk SPOELSTRA - KEMA 02003Ren9771 4

8 1. INTRODUCTION 1.1 Background In 1993 the UNIPEDE THERNOX report on NO x control Technologies was published. In this report a short statement was made about NO x measurement technologies. Widespread use of NO x reduction measures as well as a requirement to meet emission limit values means that NO x measurement is required under all operating conditions. Only robust measuring instruments are suitable for power plant operation conditions. Factors such as high mass flows, large flue gas channel cross sections, particulate containing flue gas and relatively low NO x and SO x concentrations which are all characteristic of power station emissions, pose difficulties for representative emission measurements. In recent times much work has been directed at improving measurement facilities. In 1994 the Thermal Generating Study Committee charged THERNOX to report in more detail on CEM in power stations and CHP plants. After that a working group was established to report on the European situation regarding CEM. Decision was made to collect the information by means of an inventory on experiences of CEM among the THERNOX members. 1.2 Objectives The objectives of this study were; - To document the reasons for CEM installations in Europe; are they installed to meet the requirements of the regulatory authorities?, or for process monitoring and control?, or for both purposes? - To follow-up reported studies and to survey current CEM studies in Europe. - To follow-up experience and opinions about the quality, performance, long-term availability and costs of CEM installations. 1.3 Implementation To collect (and document) the necessary information a questionnaire was sent to the THERNOX Group- members. The questionnaires were filled in by all members in the THERNOX group and were evaluated and processed by the working group. It should be noted that the results from this study are not fully comprehensive for all countries. Practice and experience is reported mainly from those utilities represented in the UNIPEDE-THERNOX group Ren9771 5

9 2. REASONS FOR CONTINUOUS EMISSION MONITORING Continuous monitoring of emissions is required principally to meet the requirements of the regulatory authorities. In the EC the LCPD 88/609/EEC prescribes the minimum requirements; -continuous monitoring of NO x, SO 2, O 2 and dust in new plants > 300 MWth, (with a possibility to exclude SO 2 and dust from the CEM demands of the authorities), - determination of annual emissions for SO 2 and NO x in new plants and -emission inventory of SO 2 and NO x in existing plants. Appendix A contains the text of article 15 and annex 9 of the LCPD which describe CEM. Also, many countries have had CEM requirements before the adoption of the LCPD. Monitoring of other flue gas components is required in some countries. There can be variations at national and regional levels, mostly depending on the thermal rating of the plant. Typical requirements for continuous monitoring are listed in table 1. TABLE I National and regional criteria for CEM Country Component Criteria Austria NO x, SO 2 > 30 MW th CO, dust > 10 MW th Belgium NO x, SO 2, dust > 300 MWth France NO x, SO 2, CO > 150 kg/h dust > 5 kg/h HCl > 20 kg/h Germany NO x, SO 2, CO, dust yes Ireland NO x, SO 2, dust there will be requirements within 2 years Italy NO x, SO 2 national law (>300 MWth), local authorities CO national and regional limits dust > 300 MWth, local authorities Netherland NO x, SO 2, dust > 300 MWth s Poland NO x, SO 2, dust emission limits CO authority requirements Portugal NO x 30 kg/h SO 2 50 kg/h CO 100 kg/h Dust - Spain NO x, SO 2, dust large combustion plants Sweden NO x all plants > 50 MW which produce more than 50 GWh/year, local authorities, fees SO 2 all peat and coal fired plants > 50 MW which produce more than 50 GWh/year, taxes Hg, NH 3, N 2 O, dust some local limits Switzerlan d NO x, SO 2, CO, dust national and cantonal (regional) authorities 02003Ren9771 6

10 Country Component Criteria United Kingdom NO x, SO 2 new plants > 50 MWth, existing plants (>50 MW th ) within 3 years, local limits also exists CO some new plant >50 MWth Dust - Secondary reasons for CEM include process monitoring and control - e.g. monitoring of NO x, CO and dust for combustion control, of SO 2 for control of FGD and of NO x to control deno x processes. NH 3 may also be measured (as in Sweden and United Kingdom) to control NH 3 -emissions from deno x processes and conditioning of dust control devices respectively. Measurement of SO 2 to control deso x processes is required in some countries - in the Netherlands the efficiency of an FGD must be better than 85 % and be controlled by CEM. Velocity may be measured for the calculation of mass flow, it is possible to direct measure the velocity but that is normally not preferred. CEM is also used for combustion modifications or other primary NO x control measures. In Sweden there is a fee-system for emissions of NO x. Plants with energy production greater than 25 GWh/year are included and must quantify their emissions of NO x either by CEM or by estimation using an officially-defined fixed high level. The principle of the fee-system is that plants which qualify must report their emissions of NO x (as NO 2 ) and their energy production to SEPA (the Swedish Environmental Protection Agency) each year. For every kg of NO x emitted the plant must pay SEK 40 (about 4). The total payments made by all plants are refunded. The refund to each plant is based on the ratio of its total energy production to the total energy production of all the qualifying plants. Plants with low emissions and high efficiency therefore make money at the expense of plants with high emissions and low efficiency. In Sweden there are also taxes on sulphur (SEK 30/kg S). This tax is based on the sulphur content in the fuel. A plant emitting less sulphur than that contained in the fuel receives a refund. CEM must be used for the determination of this refund. 2.1 Developments in Monitoring Work by Utilities the Netherlands; (NO x and SO 2 ); Multi-component analysers such as FTIR (Fourier Transform Infra Red) and PDA (Photo Diode Array) are in use. There is a gradual improvement of emission monitoring through improvements in the quality of the system in all its aspects and through an increase in the number of CEM-systems. Studies are being made on the precision and accuracy of the reported data, both for each installation and for the aggregate emissions of all power stations. Poland; In Poland there is a need for a rapid reduction in emissions from utility boilers. An increasing number of CEMs are being installed for process control. Portugal; (NO x ); Measures include research and development to assess the influence of typical measures for NO x abatement and to establish engineering relationships between operating variables influencing NO x emissions and global boiler performance in terms of energy 02003Ren9771 7

11 efficiency, fouling, slagging, safety and reliability. Several engineering tools are under development for the prediction of NO x emissions and boiler performance (as a function of operating conditions and fuel type) and these are being assessed at present. Sweden; (SO 2, CO, NO x, NH 3 ); Gradual improvements are planned such as more cost-effective CEM, "stripped" versions of established techniques and CEM based on analysis by electrochemical cells. Predictive emission monitoring (determination of the NO x -emission from other process parameters; e.g. combustion temperature, oxygen concentration, fuel flow etc.) for oil and gas burners is being studied. Recently, diode lasers have been used for NH 3 measurement. In the future; testing of continuous measurements by use of FTIR (hydrocarbons) will take place. Switzerland; (NO x ); Installation of CEM to study all parameters of the NO x -emissions and to optimise the emissions through primary measures. (SO 2 ); Oil with very low sulphur content will be used. CEM is not applied to oil fired boiler because the fuel analysis gives a better accuracy. United Kingdom; (SO 2, NO x ); Independent reviews by power producers are planned on the relative accuracy of predictive calculation methods versus direct measurement. Cost effective instrumentation is currently being reviewed. (NO x ); A watching brief will be maintained on developments in predictive emission monitoring e.g. neural networks etc. (All components); More cost-effective CEM is being sought this will be done through reviews of new instruments as and when they appear on the market Ren9771 8

12 3. TECHNICAL ASPECTS OF CONTINUOUS EMISSION MONITORING Continuous emission monitoring can be done with either extractive or in-situ systems. To date the use of extractive CEM for gaseous emissions has greatly exceeded that of in-situ CEM. A trend towards greater use of in-situ systems is now becoming apparent in the marketplace. To reduce uncertainties in the flue gas because of concentration profiles there are international standards for location of representative sampling point(s). Standard rules or guidelines for the location of sampling points for CEM have been reported from four countries (France, Poland, Sweden and United Kingdom). In most countries measurements are made at locations where the flue gas inhomogeneity is low at a single location (extractive CEM or single point in-situ probes) which is often determined by grid testing. In all countries the measurement point for emission control is located either at the stack or in the gas duct leading to it. For process control there can also be measurements before and after the de- NO x /de-so x process. A number of manufactures in Europe are listed in appeendix B. 3.1 Extractive CEM The sampling principle of most of the extractive CEM systems is based on extraction of flue gas with condensation of water vapour all countries surveyed in this study have experience of this sampling principle. Experience of extractive sampling systems with dilution has also been reported by Austria, France, Poland, Spain, Sweden, Switzerland and the United Kingdom. Heated extractive systems are used for sampling condensable components such as NH 3 and HCl. Experience of such systems has been reported by France, the Netherlands, Sweden and United Kingdom. Table II contains details of the flue gas constituents monitored and the sampling principles reported for each country. The most common analytic principles used are NDIR or NDUV-absorption. Chemiluminescence is also used for analysis of NO x. Use of converters for the reduction of NO 2 followed by analysis for NO to determine (NO + NO 2 ) is also a common principle. Analysis by electrochemical cells has been done in the United Kingdom and Sweden. Use of UV fluorescence for the determination of the SO 2 -concentration has been reported from Poland, Sweden and United Kingdom. Dust has been measured by β absorption gauges in France and Sweden. Equipment manufacturers that were mentioned in the answers include Hartmann & Braun, ADC, Emission S.A., Siemens, Rosemount, Bodenseewerk and Maihak. The operating principle of most of those analysers is based on absorption in the IR or UV spectrum of samples extracted with condensation. ADC, however, operates by extraction with dilution and uses Chemiluminescence and UV fluorescence for analysis of NO x and SO 2 respectively. Heated extractive analysers, based on 2nd derivative IR-spectroscopy combined with gas filter correlation, are produced by Bodenseewerk Ren9771 9

13 TABLE II Extractive sampling principles reported for the different flue-gas components in each country Country Sampling principles reported Components Austria extractive with condensation NO x, SO 2, CO heated extractive NH 3 extractive with dilution " Belgium extractive with condensation* NO x, SO 2, CO France extractive with condensation NO x, SO 2, N 2 O extractive with dilution NO x, SO 2 heated extractive HCl, dust Germany extractive with condensation NO x, SO 2, CO Ireland extractive with condensation CO Italy extractive with condensation NO x, SO 2, CO Netherlands extractive with condensation NO x heated extractive SO 2, NO x Poland extractive with condensation NO x, SO 2, CO extractive with dilution " Portugal extractive with condensation NO x, CO heated extractive SO 2 Spain extractive with condensation NO x, SO 2 extractive with dilution " Sweden extractive with condensation NO x, SO 2, CO, N 2 O extractive with dilution NO x, SO 2, CO heated extractive NH 3, HCl, dust, N 2 O, NO x, CO Switzerland extractive with condensation NO x, CO extractive with dilution NO x, SO 2 United Kingdom extractive with condensation, NO x, SO 2, CO extractive with dilution NO x, SO 2, CO heated extractive NO x, SO 2, CO *Gas turbines only 3.2 In-situ CEM The principle of most in-situ CEM systems is single point measurement with a probe. The most common example of an in-situ CEM, the ZrO 2 -cell which is used for the determination of Oxygen, is not discussed in this report. There are also in-situ CEM systems which measure across the duct and which are therefore less sensitive for siting. Most countries studied have experience with both types of in-situ CEM. All flue gas components discussed in this report except N 2 O have been measured by in-situ CEM techniques. The analytic principles for in-situ CEM are IR/UV-absorption or electrochemical cell-based methods. In-situ CEM systems based on opacity are used for the measurement of dust. There is also, normally, a purge air supply to clean the sample windows Ren

14 TABLE III GAS COMPONENTS IN EACH COUNTRY Country Monitoring principles reported Components Austria opacity, light absorption dust DOAS (UV) SO 2, NO x, NH 3, H 2 O Belgium 2nd derivative UV-spectroscopy NO, SO 2 IR CO opacity, light absorption dust France DOAS (UV) NO x, SO 2 Germany - - Ireland electrochemical cells NO x IR CO Italy opacity, light absorption dust Netherlands UV, 2nd derivative UV-spectroscopy NO, SO 2 opacity, light absorption dust Poland DOAS, UV, 2nd derivative UVspectroscopy NO x, SO 2 Portugal UV, electrochemical cells NO, SO 2 Spain 2nd derivative spectroscopy (IR/UV) NO, SO 2 Sweden UV NO, SO 2, NH 3 DOAS (UV) NO x, SO 2, NH 3, Hg, H 2 O, HCl NDIR CO 2nd derivative UV-spectroscopy NO, SO 2 opacity, light absorption dust diode laser NH 3 Switzerland IR CO United UV NO, SO 2 Kingdom NDIR, IR NO, CO electrochemical cells NO x, SO 2 IN-SITU PRINCIPLES REPORTED FOR THE DIFFERENT FLUE- The most commonly reported manufacturers of in-situ CEM are Lear Siegler, SICK, OPSIS, Codel, Land and Durag. SICK, Codel and OPSIS mostly measure across the duct while Lear Siegler and Land are based on measurement by in-situ probes. 3.3 Performance Criteria Performance criteria or guidelines for CEM systems have been established in most countries reported in this survey. Only Germany (anticipated in Ireland) has official approval procedures for CEM instruments, only approved types of instruments can be used. Switzerland does not have an official approval procedure as such, but in some cantons (regions), the measurement instruments must be of a type that is officially approved by the German TÜV. In Poland the General Environmental Inspectorate have established guidelines for the design of CEM systems Ren

15 Practice in the USA can be mentioned in this chapter. Germany only approves the specific components in the monitoring system. In contrast, the plant owner in the USA must implement a QC/QA-program for the entire measurement system. This approval includes very detailed tests. Although it may appear that the systems are very different, there are developments on EMAS and QA that tend to go in the same direction in Europe. Austria; NORM M9410, The extraction point is fixed by an authorised institute during commissioning ; The availability of data per month must be > 90 %; Zero point and span calibrations must be done at least once per week; A "technical service" is required every three months. The equipment and criteria are checked every year by the authorised institute; An independent system calibration is done by this institute every 3 years. France; (NO x and SO 2 ); Measurements must be carried out according to AFNOR standards (French Standards organisation) which includes sampling and measurement methods. The license issued by the local authority contains general requirements on regular checking and requires an annual test to be carried out by an accredited independent test laboratory. (Dust); The French authorities require CEM for plant emitting more than 5 kg/h. If the emission exceed 50 kg/h periodic measurements by gravimetric techniques are required also. Germany; (SO 2, NO x and dust); TA-luft prescribes the required conditions. TÜV inspection verifies this. Ireland; (NO x and SO 2 ); The Irish EPA have expressed a preference for CEM which meets TA-luft or which complies with USEPA requirements. Italy; (All flue gas components); Precision, rise time, fall time, response time, detection limit, sensitivity, repeatability, linearity, zero drift, span drift, immunity to interference are some of the instrument characteristics influencing selection in the purchasing process. The Netherlands; (SO 2, NO x and dust); Performance criteria are set according to the "Regulations of Measuring Methods of the BEES". CEM should be used in accordance with generally accepted measuring practice. Poland; In Poland there is an official issue of guidelines and technical requirements for CEM. If power plants install CEM according to these requirements, results of the monitoring are accepted by the Regional Environmental Inspectorate. At other plants the Regional Environmental Inspectorate can perform spot emission measurements. If emissions for certain components exceed upper allowable limits, the power plant must pay a penalty until measurements show that the emissions are below the legal limit. (NO x and SO 2 ); Detection limit = 2 % of measurement range; Zero point drift (between two calibrations) = 2 % of measurement range; Effect of interferences = 4 % of measurement 02003Ren

16 range or automatic compensation for interfering components; Response time = 240 seconds; The measurement range should be 150 % of average measured value. (NO x and SO 2 ); Analysis should be possible with correction of results for the measured oxygen concentration and (sometimes) the content of water vapour in the flue gas - since oxygen and water vapour determine the dilution level in flue gas. (CO); Detection limit = 0,2 %; Effect of interferences = 0,5 %; Zero drift = 0,5 %; Temperature affect = 0,2 %/10 o C. (Gas velocity); Error +/- 2 % of range (Zero and test point drift within 2 % of limit). Portugal; (NO x, SO 2 and CO); The measurement equipment must be submitted to periodic calibration according to the relevant legislation. The span and calibration gases should be certified and differ at most by 2 % from the stated value. Spain; (NO x, SO 2 ); There are standard requirements for the installation of CEM equipment. All equipment is installed at the same location where the flow is homogeneous. Sweden; (NO x, SO 2 and O 2 /CO 2 ); Criteria for CEM for the determination of NO x fees and sulphur taxes; Detection limit 2 % of measurement range; Zero point drift (between two calibrations) 2 % of measurement range; Span drift (between two calibrations) 4 % of measurement range; Effect of interferences 4 % of measurement range; Response time (the whole measurement system) 200 seconds. The measurement ranges should be about twice the highest expected concentrations in the flue gas. The span and calibration gases should be certified and differ by a maximum of 2% from the stated value. (Velocity); Criteria for CEM for measurement of velocity where this is used for the calculation of the mass emission of NO x and sulphur; Detection limit 10 % of measurement range; Zero point drift (between two calibrations) 2 % of measurement range; Span drift (between two calibrations) 4 % of measurement range; Response time (the whole measurement system) 30 seconds. (NO x, SO 2 and CO 2, O 2 or velocity); The whole monitoring system shall be verified by an accredited laboratory once a year (by parallel measurement). There are then two other criteria; The standard deviation between the utilities CEM and the accredited laboratory s CEM result or measured velocity data must be 5 % of measurement range; Systematic error between the two systems must be 2 % of measurement range. Switzerland; (All components); Use of the best measurement technology is required; the Swiss authorities set the specification for official measurements; the performance of CEM systems must be accepted by the Cantonal authorities also; the instruments must generally be approved by the German TÜV. (NO x ); Measurement according to VDI 2456; overall NO x uncertainty +/- 10 %. (SO 2 ); Measurement according to VDI (CO); Measurement according to VDI 2459; overall CO uncertainty +/- 10 % Ren

17 3.4 Determination of Mass Flow Measurement and PEM The dominant method for determination of mass flow is stoichiometric calculation on the basis of fuel composition, flue gas O 2 content and fuel consumption. This applies in most countries. Use of direct measurement of flue gas velocity is normally not used. Predictive emission monitoring (PEM) for the determination of NO x emissions has been tested in some countries. This has involved prediction by neural network or multivariate data analysis. Italy; (NO x and SO 2 ); Periodic measurements have been made on thermal units < 300 MW th. Mass flow rate is calculated stoichiometrically on the basis of fuel consumption and O 2 content in flue gas. Netherlands; It is permissible to determine NO x emissions by the continuous measurement of one or more characteristic parameters. A relationship is derived between these characteristic parameters and NO x emissions which is verified every 3 years. The statement is only true when a simple relationship exists between NO x -emissions and load e.g. in natural gas-fired power stations with constant gas quality but never in coal-fired power stations. Poland; In those cases where there is no direct measurement of the flue gas mass flow, the mass flow rate is calculated stoichiometrically on the basis of fuel consumption and the O 2 content of the flue gas. Portugal; Assessment is being done on several engineering tools which are under development for the prediction of NO x emissions and boiler performance as a function of operating conditions and fuel type. Sweden; The principle of predictive emission monitoring (PEM) is accepted by SEPA for determination of NO x -emissions. The first applications have been for two biofuel-fired boilers in two separate saw-mills during The performance criteria for PEM must be similar to the performance criteria for a CEM (chapter 5.3). Mass flow rate is calculated stoichiometrically on the basis of fuel composition and flue gas O 2 content. Switzerland; The principle of predictive emission monitoring (PEM) is generally accepted by the authorities (for gas and oil combustion). The NO x emissions can be determined by the continuous measurement of characteristic parameters. The accuracy must be similar to direct measurements. United Kingdom; A watching brief is being kept on developments in PEM e.g. neural networks. 3.5 Reporting 02003Ren

18 The EC LCPD stipulate reporting of emission from new (large) plants. LCPD describes monitoring of concentrations of SO 2, NO x and dust and the statistical procedures in order to assess compliance with ELV. In addition national or regional authorities may formulate obligations for existing plants, smaller plants and for other pollutants. Also, reports may be required for other purposes, such as emission fee-systems. The mass flow are mostly calculated from the measured concentrations in conjunction with fuel consumption, the excess air level and the fuel analysis and seldom from the measured concentrations and the measured flue gas velocity. Some of the additional national and regional limits can be simply concentration limits (ppm or mg/m 3 n) rather than mass emission limits. In such a case it is necessary to correct measurements to a fixed level of O 2 or CO 2 if emissions are to be made comparable. Otherwise it is not possible to take dilution by excess air or moisture into account. Some examples of reporting to the authorities are as follows; Austria; (NO x, SO 2, dust and CO); At least one set of data are measured per minute, mean values are calculated for every half hour and daily mean values are also calculated. A yearly report is made to the regulatory authorities; part 1 covers emission mass flows/month and part 2 covers compliance with the legal limits: Legal requirements are met if no daily value > limit, if less than 3 % of half hour values > 120 % of the limit and if no half hour value > 200 % of limit. Belgium; (SO 2, NO x and dust); Collection of measurement data is done every 15 seconds, the NO x concentrations are calculated, standardised (for O 2 ) and stored every half-hour. Daily mean values are calculated from the half-hour mean values. Daily, monthly and annual reports are available. The mass flows and a classification of the half-hour mean values (frequencies > 1,2 and > 2 times the limit values) are detailed in these reports. An annual report is sent to the authorities. France; (NO x, SO 2, dust and HCl); Collection of measurement data is done every 10 seconds and minute-average figures are calculated as basic data. An average concentration is calculated every hour from calculated mass flows. Daily and monthly mass flows, exceedances, average and maximum concentrations are reported monthly to the regional authority. An annual report is sent to the Environment Ministry. Germany; (NO x, SO 2 and CO); An annual report is made. Italy; (NO x, SO 2 and dust); The monthly arithmetic mean, summary statistics of the 48 hourly averaged values over the year and the total annual mass emission must be reported on a periodic report (usually yearly). The Netherlands; 02003Ren

19 (NO x, SO 2 and dust); Reporting is done for both existing and new installations, annually or more frequent, on an individual basis. Poland; (SO 2, NO x and CO); Half hourly data must be available to the authorities. If limits are exceeded a report is made on a special form. Portugal; (NO x, SO 2 and CO); The measurements of emissions are sent to the authorities every three months in the case of CEM, and within 30 days for any spot measurements. Regarding CEM, the statistical parameters are determined with a minimum of 75 % of possible values, measured in normal conditions during a reference year (1 April - 31 March). The same approach is applied to the calendar year i.e. the period between 1 January and 31 December. Spain; (NO x and SO 2 ); Half-hourly data is reported to the national authorities in a standard format. Sweden; (NO x ); Reporting of NO x for determination of fees; Hourly mass flows are calculated. These mass flows are summated to produce daily mass flows and the daily masss flow are used to generate annual mass flows. The annual mass flows are reported to the Swedish EPA. (SO 2 ); Reporting of SO 2 for determination of taxes; Hourly mass flows are calculated. These mass flows (sulphur) are summated to produce daily mass flows and the daily mass flows are summated to produce annual mass flows. The annual mass flows are declared to the taxation authority. (All components); There are also requirements from the regional authorities, generally involving annual reporting. These requirements refer mostly to specific emission rates (mg/mj) but in some cases reporting is required of emission concentrations normalised to a fixed concentration of O 2 or CO 2. Continuous monitoring of emissions is not necessary for these purposes. Switzerland; (NO x, SO 2 and CO); The cantonal (regional) authorities assume that the emission limits are complied with. They verify the power plant emissions (by official measurements) every ~ 2 years. A detailed report, based on CEM or PEM of all power plant emissions (NO x, SO 2, CO, dust, volatile organic compounds,..), must be given (~yearly) to the authorities: This covers the type of emission, the emission concentration and its mass flow as a function of time and further statistical information to fully describe the situation. The SO 2 emissions can be calculated from the fuel analysis for oil fired boilers. United Kingdom; (SO 2, NO x, and CO); Hourly averages are determined every 10 minutes. No averages must exceed 150 % of the set limit. 95 % of the hourly averages in a month must be below the limit. Annual mass emissions are reported Ren

20 4. EXPERIENCE WITH CEM Experience in different countries of the two measurement systems (extractive and in-situ) is reviewed in this chapter. A common theme in many responses was difficulty in obtaining a consistent reliable supply of calibration gas. 4.1 Extractive CEM There is variable experience with extractive CEM but most countries have had good experience while the availability in some countries has been poor. In general there have been few problems specifically with the analysers and almost all difficulties reported relate to the sampling and calibration systems. Condensate management requires careful attention if problems are to be avoided. Maintenance requirements can be high unless the system is carefully designed with e.g. provision for back purging of probe filters. Only a few reports about dilution systems was given and the experience was mixed. A major advantage of extractive systems is their ease of calibration. Experience in each country is as follows; Austria; (All components); Extractive with condensation - generally good experience for all components even at high dust concentrations, some problems with leakage (difficult to detect) and with interferences from moisture in the flue gas (NDUV/NDIR). (All components); Extractive with dilution - generally satisfactory for all components, can only be used in gases with a low dust content, problems with calibration exist (dilution can vary with temperature), difficulties exist for correction of measurements to standard dry conditions (NDUV/NDIR). Heated extractive CEM - is used in two cases for measurement of NH 3. Experience is acceptable. Belgium; (SO 2, NO x and CO); Use of NDIR for plant monitoring has been abandoned because of high maintenance costs. It is still used for comparative measurements but the sampling system adds many uncertainties. Extractive systems work satisfactorily on gas turbines where they are the only type suitable for gas monitoring at high temperature (550 C). (CO); Good with clean flue gases; for gas turbines (NDIR). France; (SO 2 and NO x ); No important problems with NDIR instruments which are fitted to most EDF power plants. (Dust); β-absorption method is used. Maintenance is made difficult by the sampling location - generally in the upper portion of stack. Germany; (NO x, SO 2 and CO); Good experience is reported for one utility (NDUV/NDIR). Ireland; (NO x ); Highly labour intensive based on a single experience. (CO); Poor performance. Condensation causes blockage of gas flow, leakage problems at pumps and cooler, probe filter plugging (NDIR) Ren

21 Italy; (NO x, SO 2 and CO); Installed in all ENEL power plants > 300 MWth. Principle is NDIR/NDUV. > 80 installations for NO x and SO 2. Problems with automatic calibration procedures due to the quality of calibration gases. Problems also with the gas dehumidification system. Netherlands; (NO x ); Attention must be paid to representative and proportional sampling. Good agreement with independent measurements. Novel techniques such as FTIR or PDA (photo diode array) are still not sufficiently developed to be used for CEM. (SO 2 ); All parts must be heated to avoid loss of SO 2 in condensate, attention must be paid to representative and proportional sampling (NDIR/NDUV). (NH 3 ); All parts in the sampling system must be heated to avoid condensation of water vapour and ammonium salts (NDIR). (N 2 O); The interferences of CO, CO 2 and NO must be checked regularly (NDIR). (Dust); Dust monitoring is installed after the FGD plant. Sampling systems may clog when the plant is restarted after a shutdown. Monitors are adjusted monthly (zeroed) and are maintained twice yearly. Poland; (All components); There are about 40 systems installed, but, within each power plant, the same CEM type is normally used for measurements on the different boilers. Generally there is good experience of extractive CEM with condensation, some problems arise relating to leakage (difficult to detect) and moisture. Maintenance problems occur with sample conditioning. It is of limited usefulness for on-line process control because of the long response time (NDIR/NDUV). Portugal; (NO x and SO 2 ); Calibration problems are often encountered. Minor problems related to the condensate drain pump are sometimes reported (NDIR, NDUV). (SO 2 ); Problems related to H 2 SO 4 formation and associated corrosion (NDIR). (CO); Calibration problems (NDIR). Spain; (NO x, SO 2 ); Generally good experience. Maintenance problems with sample conditioning equipment (NDUV/NDIR/Chemiluminescence). Sweden; (NO x, SO 2, CO, N 2 O); Extractive with condensation - generally good experience (availability and performance), problems with leakage at connections, coolers or pumps, plugging of the probe filter or with drain pumps. CO could not be measured in series after the NO x - converter. The maintenance can be much reduced if systems for automatic calibration and back purging of the probe filter are installed (NDIR/NDUV). (N 2 O); Hydrocarbons can interfere (NDIR). (NH 3, H 2 O, HCl); Heated extractive. Problems with condensation of moisture and ammonium salts (2 nd derivative IR-spectroscopy combined with gas filter correlation). Switzerland; 02003Ren

22 Extractive with condensation: (NO x, CO); Good experience with multi-point probe. Frequent calibration is important. To check for leakage, it is important to be able to inject the different calibration gases near the sample probe and also near the CEM instruments. The fast response time allows the detection of small combustion changes in optimisation (chemiluminescense/ndir). United Kingdom; (NO x ); Generally good availability, some problems with drain pumps (NDIR). (SO 2 ); Problems with high moisture content flue gas analysis (NDIR) after FGD processes (limited experience). (CO); Problems with drain pump and condensation of sample in lines, trace heating recommended (NDIR). 4.2 In-situ CEM There is generally good experience with in-situ CEM. A disadvantage of most in-situ systems is the problem of calibration on a regular and routine basis. The main advantage is the removal of any need for sample conditioning. Although low levels of maintenance are reported it is clear that there is need for a minimum level of essential maintenance e.g. cleaning of windows and checking of optical path alignment. All dust CEM which uses light absorption or opacity must be calibrated against a manual gravimetric dust measurement. The opacity and light scattering from particles from different fuels normally varies. Some experience in the different countries is as follows; Austria; (Dust); Problems with water droplets after FGD. (SO 2, NO x, NH 3, H 2 O and CO 2 ); Generally good experience is reported with DOAS after a lengthy adjustment period in a waste incineration application. Belgium; (All components); No severe systematic defaults has been observed. Measurement of the emission parameters requires extremely reliable sensors which provide self calibration, including auto/zero correction, auto/span checks and correction. Highly encouraging results have been achieved. (SO 2, NO); Thirty analysers of the 2nd derivative UV type have been in use since Accurate, free of interferences, calibration intervals are of the order of 6 months. Very low instrument drift, inaccuracy is frequently a result of bad calibration, air leakage is a possible source of inaccuracy. Equipment intervention has been limited almost completely to replacement of the UV-lamp. (Dust); ~ 60 dust density monitors in use since The calibration of optical density to mass concentration varies with type of coal. Although not easily quantifiable, the error amounts to at least 30 %. France; (NO x and SO 2 ); A test of DOAS has been in progress for some months in an EDF power plant Ren