IN
DEGREE PROJECT MECHANICAL ENGINEERING, SECOND CYCLE, 30 CREDITS
STOCKHOLM SWEDEN 2016,
On the assessmement of pollutant emissions: the role of flue gas flow rate measurement
Critical review and industrial feedback JULIETTE CHATEL
KTH ROYAL INSTITUTE OF TECHNOLOGY
SCHOOL OF INDUSTRIAL ENGINEERING AND MANAGEMENT
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Master of Science Thesis EGI-2016-106MSC
On the assessment of pollutant emissions: the role of flue gas flow rate measurement
Critical review and industrial feedback
Juliette Chatel
Approved 2016-22-12
Examiner
Per Lundqvist
Supervisor
Fabian Levihn
Commissioner ALCIMED
Contact person Ronan Lucas
Abstract
From a bottom-up perspective, the assessment of flow rate of stack flue gases is crucial being the very first brick of the calculation. With the concentration of pollutant, it gives access to the amount of pollutant released in the atmosphere. Nevertheless, flow rate measurement has not been well-framed and can be poorly controlled, leading to large uncertainties. The recent launch of the European Standard EN 16 911 has enlighten the lack of expertise concerning the flow rate assessment in the industry. That is why RECORD, the project sponsor, conscious of the possible lack of expertise and the possible unreliability of the measurement is willing to understand the requirements; theoretical, technical and regulatory; for a reliable pollutant emissions measurement in accordance with the EU regulation in the field of waste treatment and incineration.
Thus, this study offers the theoretical, operational and regulatory keys to realize a reliable flow rate measurement. 9 methods are identified for stack flue gases flow rate measurement. For each of these methods an ID-card, based on bibliographical researches, supplier’s interviews and representatives of the industry’s feedbacks, has been built containing information required for a reliable measurement. This thesis will contribute to a report that will offers all the keys for a reliable velocity/flow rate measurement in the waste treatment (domestic waste incineration mainly but it can also be useful in every industry that releases flue gas in the atmosphere: chemistry, steel manufacture, etc.).
Moreover, this study proposes an analysis of the European Standard related to flow rate measurement in the industry and enlightens the key information related to these standards for an industrial operator.
Finally, in relation with the complete report published on the RECORD website, a comparison tool of the 9 technologies is created to guide the industrial in their flow rate measurement. Once the best technology has been selected thanks to the comparison tool, the ID-card gives the key to realize a reliable measurement with the selected method. Finally, the theoretical part and the standard analysis have to be used as a frame for all the technologies.
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Table of Contents
Abstract ... 2
Foreword ... 6
1 Context and problem formulation... 8
1.1 Background ... 8
1.2 Problem formulation ...10
1.3 Purpose and research questions ...11
1.4 Expected contribution ...11
1.5 Disposition ...11
2 Methodology ...14
2.1 State of the art of the techniques and devices for flue gases flow rate measurement ...14
2.2 Review of current standards ...17
2.3 Collection and analysis of industrial feedbacks on flow rate measurement ...17
2.4 Planning of the study ...17
2.5 Discussions on the methodology ...17
3 Results ...20
3.1 Theoretical and operational reminders on flow rate and velocity measurement of canalized flows 20 3.2 Technologies identification ...32
3.3 Review of the technologies ...34
3.4 Technology comparison ...40
3.5 European standards analysis and synthesis ...42
4 Conclusions ...44
5 APPENDICES ...46
5.1 APPENDIX 1: Techniques ID card template ...46
5.2 APPENDIX 2: Uncertainty calculation for the QAL1 certification of a Pitot tube manufactured by PCME Ltd. (TUV Rheinland, 2016) ...52
5.3 APPENDIX 3: QAL 1 certificated flow rate/velocity products (MCerts; SIRA certification; CSA group, 2016) (TUV Rheinland, 2016) ...54
Acknowledgements ...56
List of figures ...58
References ...60
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Foreword
The following report is the result of several months of work in the Energy and Environment department of the innovation consulting company ALCIMED. Created in 1993 in Paris, it now employs 200 consultants all around the world divided in the following different business units:
healthcare industry, life science, agribusiness, public policies, chemicals and materials and finally energy, environment and mobility. The Energy and Environment team work with companies involved in renewable energies, oil & gas, power, water, waste, energy efficiency, energy management, industrial gases, tertiary and nuclear industries. Missions type are various: new market approaches (e.g. designing new services, designing innovative business models, seizing opportunities in adjacent markets, implementing unexpected partnerships, motivating communities of customers), technological developments (e.g. the impact of new technologies, analyzing the actions of market leaders and innovators, building an ecosystem of technology partnerships, drawing up an R&D roadmap) or simply to establish positioning on new issues (e.g. Industrial Internet of Things, circular economy, sharing, blockchain…).
This project was conducted for the French collaborative network RECORD gathering public and private environmental organizations. The main objective of this collaboration is the funding and the realization of studies and researches in the field of waste (domestic and industrial) and industrial pollution. Their areas of study are: the evaluation and the characterization of waste and pollution, the management of waste and contaminated sites, the evaluation of the impacts on health and on natural environment and the development and integration of knowledge from the field of social sciences.
The results of this work will be published in a completed report titled – Mesurages de vitesses et débits gazeux en vue de déterminer des flux de polluants canalisés. Revue critique et retours d’expérience1. This document will be released in the first months of 2017 on the RECORD website2 and will be accessible by everyone. The following article describes the work and the discussions encountered during the realization of this study. Some results cannot be found in this thesis but in the report on the RECORD report due to confidentially and properties reasons.
Nevertheless, links to this report have been added to the section of the report.
The project manager, Mr. Lucas supervised, challenged and guided me during the work. A technical expertise especially in the field of European Standards was provided by the INERIS – National Institute of Industrial environment and risk.
NB – Due to confidentiality issues towards the ALCIMED Company, some data will not be communicated in this report.
1 In French on the website – The assessment of pollutant emissions: the role of flue gases flow measurement. Critical review and industrial feedbacks
2 The final report is available here: http://www.record-net.org/reports
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1 Context and problem formulation
This chapter introduces the key issues of pollutants emissions assessment with the crucial role of flow rate and velocity measurement in the industry, which can lead to important uncertainties and mistakes if the good practices of measurement are not well implemented.
1.1 Background
1.1.1 GHG emissions reduction: a compulsory step for climate change mitigation
With more than 15 755 million tons of CO2eq released in 2012 by the OECD countries (OECD, 2016), the CO2 emissions and more globally the Green House Gases emissions are at the heart of the global warming concerns. A scientific consensus has now emerged to link the GHG emissions to the global rise of temperature and its dramatic consequences on climate change.
1.1.1.1 GHG emissions from a top-down perspective
These scientific publications have raised awareness and have led to political actions, with the Kyoto protocol at first followed by the recent COP 21 and 22. In all of these agreements, the mitigation of states emissions are crucial and debated issues: 188 countries are committed to reduce their emissions to limit global warming to 2°C between now and 2100. This target can be reached by reducing the GHG emissions by 40-70% by 2050 and the carbon neutrality needs to be achieved by the end of the century (COP 21, 2015).
To respect these commitments, actions have to take place at the origin of the GHG emissions which are described in the following chart:
Figure 1: Global mean surface temperature increase as a function of cumulative total global carbon dioxide (CO2) emissions from various lines of evidence, source:
(IPCC, 2014)
Figure 1: Time series of global annual change in mean surface temperature for the 1900–2300 period (relative to 1986–2005) from Coupled Model Intercomparison Project Phase 5 (CMIP5) concentration-driven experiments, Source: (IPCC, 2014)
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Figure 2: Total anthropogenic greenhouse gas (GHG) emissions by economic sector (gigatons of CO2- equivalent per year, GtCO2-eq/yr) from economic sectors in 2010, source: (IPCC, 2014)
Thus, the direct emissions represent more than half of the global GHG emissions, and more than half of these are from industry. Thus, flue gases released in the industry (post-combustion mainly) represents an important share of the GHG emissions. This enlightens the importance of GHG evaluation in the industry releasing stack flue gases: gases released in the waste treatment industry are mainly composed of CO2, O2, H2O and N2 (IVRY PARIS XIII, 2013).
1.1.1.2 A need for trustful GHG emissions measurements
To mitigate the direct emissions, a carbon market has been implemented (European Comission - Climate Action, 2016) on the principle “polluters pays”: a GHG emissions threshold is delivered to industries releasing greenhouse gases. Companies that have emitted less than expected can sell CO2 quotas and those who exceed their threshold have to buy CO2 quotas or right to pollute. This implies that GHG emissions have to be precisely measured to have a trustful system. Besides, this is not the only reason for a precise and trustful measurement: many countries have implemented, national or supranational in the case of European Union, GHG emissions statements. The monitoring of the emission and the realization of right and reliable measures are crucial to respect their political commitments.
1.1.1.3 GHG emissions from a bottom-up perspective: the current situation of GHG emission measurements in the industry
As it has been underlined in the section above, the GHG emissions evaluation is crucial for each emitted entity. The mass of GHG gases; carbon dioxide CO2, methane CH4, nitrous oxide N2O, fluorinated gases;
and also substances (for these last ones are not GHG but are important for environmental pollution)possibly regulated for environmental and health reasons such as heavy metals have to be known for the reasons explained above.
Currently, in Europe at least, industry has to declare their emissions in terms of pollutants concentration in mg/Nm3 (3) (FNADE, 2006). Yet, this concentration value cannot give access to the amount of pollutants emitted during a period of time.
3 The Nm3 are referring to standard conditions: the pressure is taken at 1 013 hPa and the temperature at 0°C. Cf.
section 3.
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The concentration level can only provide threshold below which the local impacts on the environment and health are considered low. Nevertheless, it is not sufficient to determine accurately the amount of GHG released during a time lapse.
1.1.1.4 The need for flow rate or velocity measurements
The evaluation of yearly pollutant emissions requires the flow rate or the velocity of the flue gases emissions in Nm3 per unit of time.
1.1.1.5 The lack of framework concerning the flow rate measurement
As it has been enlighten before, currently the industry master and monitor the concentration measurements, which are well standardized and normed, whereas the flow rate measurements can, in some cases, be inaccurate (local measurements, non-established flow, non-symmetrical flow, etc.) and can cause reliability issues (charged fluid, calibration defects, etc.) if the good practices are not fully and well- implemented. Suppliers and experts4, interviewed during the study, agree that the measurement can be, in some cases, poorly controlled (influence parameters unknown, installation issues, large uncertainties, etc.).
Indeed, when local regulations (such as prefectural order-decree) do not impose the flow rate measurement and the reliability control, the measurement can be up to 20% inaccurate, implying 20% of uncertainties on the pollutant emissions.
1.1.1.6 EN 16 911: a new standard to regulate the flue gases flow rate measurement in the industry
This measurement has been recently regulated in Europe with the publication of a new European Standard, the EN 16 911, describing and regulating the performances, the installation, the calibration and the use of flow rate or velocity AMS (Automatic Measurement System)5. This recent publication of the EN 16911 (entering in effect in 2017) is still debated and will come into effect in the next months.
1.2 Problem formulation
The EN 16911 has launched the debate on flow rate measurement in flue gases and has enlightened the possible lack of knowledge and expertise on this measurement, which is a vital
4 Experts interviewed and reports on the subjects (ROBINSON)
5 A similar standard, the EN 14 181 were already implemented concerning the system measuring the concentration (the gases analyzers or dust monitors).
Figure 3: The role of flow rate measurements in the assessment of pollutant emission
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value to determine pollutant emissions yet. Actually, as figure 4 illustrates, the flow rate quantity is crucial to determine the amount of pollutant emitted during a period of time.
1.3 Purpose and research questions
The issue of pollutants emission, and as it is emphasized in the previous paragraph, is particularly crucial in the waste treatment industry where flue gases are extremely framed and where multiple treatments are applied (IVRY PARIS XIII, 2013) (Urban community, 2007) before the release in the air. That is why RECORD, conscious of the lack of expertise and of a complete, simple guiding tool, eagers to understand the requirements; theoretical, technical and regulatory; for a reliable pollutant emissions measurement in accordance with the EU regulation in the field of waste treatment and incineration. Thus, this thesis will contribute to a report that will offer all the keys for a reliable velocity/flow rate measurement in the waste treatment (domestic waste incineration mainly but it can also be useful in every industry that releases flue gas in the atmosphere: chemistry, steel manufacture, etc.). Until now, no report are existing to guide the flowrate/velocity measurement in the industry.
The following research questions and sub-questions have structured the project approach:
• RQ 1: How can a flow rate measurement of flue gases be reliable?
• Sub-question 1.1: What are the theoretical requirement, for an industrial operator, that can impact the flow rate measurement reliability and accuracy?
• Sub-question 1.2: How to choose the right instrument between the different existing technologies and on which criteria, for a reliable flow rate measurement?
• Sub-question 1.3: How is the measurement carried-out on site, are there any best practices emerging among the industries?
• RQ 2: How to apply to European Standard on the flue gases flow rate assessment?
1.4 Expected contribution
The purpose of the study is to provide a guiding tool for waste treatment (mainly domestic) industries regarding the flow rate measurement with the theoretical, the technical and the regulatory knowledge for a good, reliable and trustful emissions assessment.
The final results will be presented in front of the RECORD steering committee, composed of experts and decision-makers of waste treatment leading company, in January 2017. After the approval of the RECORD members, the deliverables will be published on the RECORD website and broadcasted among the members of RECORD6.
1.5 Disposition
The deliverable published on the RECORD website follows the disposition below which is also the disposition of this report7:
1- Context and problem formulation - This chapter introduces the key issues of pollutants emissions assessment with the crucial role of flow rate and velocity measurement in the industry, which can lead to important uncertainties and mistakes if the good practices of measurement are not well implemented.
2- Methodology – This section underlines the objectives of the study, the expected results and the methodology used to reach them. The study has been conducted in three main steps: a literature review with multiple types of sources combined with flow rate devices suppliers interviews with the objective to realize a state of the art of the existing
6 http://www.record-net.org/members
7 In this report, the results part is not fully integrated due to confidential reasons. Nevertheless, they could be found on the RECORD website once the study is published.
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available techniques for gas flow rate measurement, an analysis and a synthesis of the European standards and a collection of interviews of representative of the industry to gather feedbacks on the flow rate measurement in industries.
3- Results – The results section is organized in five main parts described below.
a. Theoretical and operational reminders on flow rate and velocity measurement of canalized flows – This section provides a short fluid mechanics theoretical description with the perspective to be usable at an operational level. The objective is to guide the operators to reliable measurements, explains and illustrates the basics of the measurements theories (influence of specific parameters, installation conditions, uncertainties parameters, etc.). In this section, the important messages from the standards are also included to make the standard key information practical and usable for industry.
b. Technologies identification – During the bibliographic researches and the different interviews conducted, 18 technologies have been identified for flow rate/velocity evaluation of gases. Out of theses 18 methods, only nine technologies have been selected for flue gases flow rate measurement in the industry.
This section explains the reasons of this selection and lists the available and usable technologies.
c. Review of the technologies – This section is composed of the 9 technologies descriptions. For each technology, an “ID-card” has been created describing: the principle of the measurement, the installation conditions, the benefits vs. the drawbacks of the solution, the main fields of application and typical case- studies if available, the diffusion rate of the solution in the industry, the operating condition of the technology (type of fluid, measurement ranges), the performances of the method, the costs (purchasing and operational) and finally the main suppliers. These ID-cards are a synthesis of the literature review, the suppliers’ and the industrial users’ interviews. The objective is to build a synthesis and practical comparison tool between the different technologies and to underline the correct and proper usage of the method to obtain a reliable and trustable measure. Besides, the terms and the notions used in the ID- cards are described, explained and illustrated. They are also linked and underlined with best practices and vigilance points - that have to be kept in mind – gathered during the interviews of industrial users and suppliers.
d. Technology comparison – This section provides a comparison tool for the industries. Different criteria have been used related to the type of fluid, the environment of the measurement, the cost, etc.
e. European Standard analysis and synthesis – This section enlightens notions and important issues that can be found in the European standards related to air emission monitoring: the EN 15 259, 14 181, 15 267 and the last released the EN 16 911that will be implemented next year, in 2017.
4- Conclusions – This part concludes the work presented, underlines the answers provided to the researches questions, the impact on the study and also enlightens knowledge gathered during the master thesis realization at Alcimed.
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2 Methodology
This section underlines the objectives of the study, the expected results and the methodology used to reach them. The study has been conducted in three main steps:
1. a literature review with multiple types of sources combined with flow rate devices suppliers interviews with the objective to realize a state of the art of the existing available techniques for gas flow rate measurement
2. an analysis and a synthesis of the European standards
3. a collection of interviews with representatives of the industry to gather feedbacks on the flow rate measurement in industries.
The study has followed three main steps with dedicated means for each of them:
It has been decided during the first steering committee that the work will also include flow rate measurement techniques for:
• the measurement of flow rate of stack flue gases with the objective to estimate the emissions and to be in conformity with the regulation,
• the measurement of process gases in the incinerator plant and biogas with the objective to assure control of the process.
2.1 State of the art of the techniques and devices for flue gases flow rate measurement
2.1.1 Bibliographic researches
The bibliographic researches aimed to identify the available techniques and to characterize them, to understand the features of flow rate measurement and finally to gather best practices. To reach these objectives, sources from diverse nature have been used: academic supports, specialized media, scientific publications identified thanks to specialized databases – SCOPUS, SCIENCE DIRECT &
Figure 4: Methodology of the study - Objectives & means implemented
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TECHNIQUES DE L’INGENIEUR, MSc and PhD works, licenses database, publications from public institutional organisms, social media (Twitter8 and LinkedIn work group9), websites of flow rate solution supplier.
The main sources are listed and classified below:
8 The Twitter researches have allowed finding the magazine Flow Control.
9 The LinkedIn groups have helped during the state-of-the-art to check if no technology were forgotten and during the validation of the benefits/drawbacks for each technology.
10 Techniques de l’ingénieur, Engineering techniques are a reference database in engineering field: http://www.techniques- ingenieur.fr/.
Academic supports Teaching supports in fluid mechanics courses Bachelor and Masters level (COUFFIGNAL BTS CIA) (GATT, 2006) (MARCOUX, 2016) (SENGUPTA) (MOISY, 2014)
Specialized media Flow control magazine (WYATT, 2013)
Scientific publications 27 relevant publications counted since 2011 on the SCOPUS database 7 relevant publications on specific flow rate measurement techniques on the SCIENCE DIRECT database
5 relevant articles in the Techniques de l’ingénieur 10 (TI - Techniques de l'ingénieur): Optic velocimetry (BOUTIER, et al., 1998), Local velocity measurements in a fluid (DUPRIEZ, et al., 2013), Volumetric flow rate measurement devices (DELLA BELLA, 2007), Choice of a flowmeter (SIGONNEZ, 2006), Temperature sensors (ROGEZ, et al., 2010) PhD thesis (LE GLEAU, 2012) (RIGAL, 2012)
MSc thesis (BENHICOU, 2003) (CHERIGUI, 2003) Specialized literature (BOUTIER, 2012)
1 interview realized with the Scientific Director of RECORD, Department Head of Industrial Processes for the University of Technology of Compiègne (UTC)
Patents 300 patents reviewed on the European patent office database (EPO - European Patent Office , 2016) with a worldwide scope, using the key words: “flow meter” OR “velocity fluid” NOT(electromagnetic OR ultrasonic), from 2012 to 2016
Institutional publications United States: Environmental Protection Agency (US Environnement
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11 « BREF or ‘BAT reference document’ means a document, resulting from the exchange of information organized pursuant to Article 13 of Directive 2010/75/EU, drawn up for defined activities and describing, in particular, applied techniques, present emissions and consumption levels, techniques considered for the determination of best available techniques as well as BAT conclusions and any emerging techniques, giving special consideration to the criteria listed in Annex III to Directive 2010/75/EU. A similar definition was applicable under the IPPC Directive (2008/1/EC). » (JRC - Joint Reasearch Center, 2016)
12 ADEME – National Agency for the Environment and the Energy Control, France
13 CETIAT is a study, testing and calibration laboratory in the fields of aerodynamics and fluid mechanics, heat sciences and acoustics.
14 INERIS – National Institute of Industrial environment and risks.
Protection Agency , 2016), NIST – National Institute of Standards and Technology, US Department of Commerce (NIST, 2016), Laboratory report (ELI LILLY & TIPPECANOE LAB, 2006)
Europe
European collaboration: VGB European Working group emission monitoring (GRAHAM, et al., 2012), European Committee for Standardization (UE) (CEN - European Committe for Standardization, 2011), European - Best Available Techniques11: Monitoring of emissions from Industrial Emission Directive-installations (JRC Joint Reasearch center, 2013), Waste incineration (European IPPC Bureau - Integrated Pollution Prevention and Control, 2006)
UK: National Physical Laboratory (ROBINSON), National Measurement Systems (TUV Nel for the National Measurement Office, 2009)
Netherlands: NL Agency (InfoMil, 2012)
France: Ademe12, CETIAT13 (CETIAT, ADEME & DGCIS, 2014) (RIQUIER, 2013), INERIS14 (POULLEAU, 2014) (CETIAT, INERIS &
LNE, 2004)
Website and documentation of
measurements solution suppliers ABB, Codel international, Cole Parmer, Dantec, Delta fluid, Dr. Födish, Durag, Fluid Component international, Fuji Electrics, Hontzsch, Horiba, Itron, Kurz, OSI, OTI industries, PCME, Sick, Siemens, SKI, TSI, Vortek, Yokogawa
Social media Workgroup LinkedIn (Continuous Emissions Monitoring Professionals, Air emissions monitoring, flow measurement, Flue gas know how, Metrology and Test measurement, Waste management and recycling professionals, Instrumentation technicians group), Twitter (Flowmeters supplier accounts)
Figure 5: Main sources used during the literature review
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The researches have been conducted both in English and in French.
2.1.2 Flowmeter supplier interviews
In order to complete the technical information gathered on their website and documentations, 14 phone interviews have been conducted with solutions suppliers located in Europe (France, UK, Germany, Spain, Italy and the Netherlands) and in North America. Their knowledge was precious to truly understand their technology but also to identify best practices related to it. Moreover, the discussions have also allowed identifying the key selection criteria related to flow rate sensors.
2.2 Review of current standards
This phase has included an analysis and a synthesis of the European Air Emission standards: EN 16 91115, 14 18116, 15 25917, 15 26718 related to devices, measurement methods, the qualification and the certification of the devices used, as well as their calibration and their performances requirements (such as uncertainty, reproducibility and resolution). Moreover, the work has included a study of the two certifications institutes of air emission devices: TUV Rheinland (TUV Rheinland, 2016), MCerts (MCerts;
SIRA certification; CSA group, 2016).
Finally, for this part, multiple exchanges were made with the INERIS – National Institute of Industrial environment and risk – with the dedicated department of standards. These discussions have led to the choice of the 4 standards named earlier.
2.3 Collection and analysis of industrial feedbacks on flow rate measurement
7 interviews have been conducted with representative of the industry (metrology operators and engineers, environment and process engineers, project managers, R&D measurement engineers, etc.) operating in biogas production and transport, in domestic waste incineration, in hazardous waste incineration or in chemical industry located in Europe (France, Germany and Bulgaria). The objectives were to understand their measurement context (type of gases, humidity content, temperature, straight lengths, inner pipe diameter, type of flow, etc.), the solution they use, the reason why they have chosen this solution and the problems encountered – to underline the possible correlation between a characteristic of the measurement environment and the choice of a specific device but also to identify best practices.
2.4 Planning of the study
The study has begun on the 16th of June with a launch meeting with the ALCIMED team and the steering committee of RECORD composed of 10 persons followed by two steering committee meetings in mid- September and mid-November. A final meeting is planned for January 2017/
During these meetings, intermediary results were presented and the scope of the study was modified with the willing to introduce the study of biogas measurement (during the production on the waste site, the transports and finally before the engines or the boilers) for instance.
2.5 Discussions on the methodology
The methodology used to conduct this study is robust meaning that the results are not affected by small variations. Actually, the diversity (geographical, nature of source, interviews of both suppliers and users) of the sources has allowed validating the information. If one piece of information was contradictory to another one, it has been challenged by other interviews and researches. For each of the nine selected
15EN 16 911 – Stationary source emissions -- Manual and automatic determination of velocity and volume flow rate in ducts (EN16911, 2016)
16 EN 14 181 – Stationary emissions – Quality assurance of Automatic Measuring Systems (EN14181, 2014)
17 EN 15 259 – Air quality - stationary source emissions measurement. Requirements for measurement sections and sites and for the measurement objective, plan and report (EN15259, 2015)
18 EN 15 267 – Air quality – Certification of Automatic Measurement System (EN15267, 2015)
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technology but also to challenge the non-relevant nature of the nine remaining, multiple suppliers’
interviews have been made (the interviews were conducted at different level: from the sales representative, to the R&D team through the product manager). Moreover, in order to challenge technology comparison, suppliers offering several techniques from different manufacturer19. They were able to offer neutrality in front of the technology benefit/drawbacks and performances.
Besides, it was very interesting to have feedbacks of industrial users for the lesser known technics to balance and challenge the information from suppliers that tend to highlight only the benefits of their solution. They were chosen in order to have the wider points of view on the different technologies.
Researches have been conducted before among the suppliers to have a list of their users or of their installation sites. When their answers were negative, researches have been made on LinkedIn and on the internet to look for case studies and possible users contacts. These researches have led to 7 interviews covering almost all the technology19. Case-studies or articles in magazines have completed the lack of information for the few technologies without interviews.
This challenge of data and on the choice of the difference criteria of the ID-cards (Cf. 3.3.1.1) between the different sources has also allowed validating the methodology.
One of the other possible weaknesses of the methodology was to forget one technology during the state- of-the-art phase. That is why the researches have been extended to patents (more than 300 patents examined from the last 4 years) and the two databases for scientific publication (164 publications reviewed on the Scopus database researches). Moreover, the technology list has been validated with experts from the RECORD scientific research direction and from the INERIS. Finally, Twitter and questions asked on specialized working group on LinkedIn: Continuous Emissions Monitoring Professionals, Air emissions monitoring, flow measurement, Flue gas know how, Metrology and Test measurement, Waste management and recycling professionals, Instrumentation technicians group have allowed to validated the list.
19 The name or brand interviewed cannot be write here due to confidentiality reason.
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3 Results
3.1 Theoretical and operational reminders on flow rate and velocity measurement of canalized flows
This section provides a short fluid mechanics theoretical description with the perspective to be usable at an operational level.
The objective is to guide the operators to reliable measurements, explains and illustrates the basics of the measurements theories (influence of specific parameters, installation conditions, uncertainties parameters, etc.). In this section, the important messages from the standards are also included to make the standard key information practical and usable for industry.
In first words, it is worth recalling the use of normal conditions for temperature and pressure (noted N in front of units or X0 for physical quantities) in the industry. They are measurement conditions for which temperature and pressure are fixed, respectively at 0°C (T0 = 273 K) and at atmospheric pressure (P0 = 1.013 105 Pa). Thus, the flow rate will be expressed in Nm3/h and not in m3/h.
3.1.1 Essentials of fluid mechanics
In this section, the fundamental principles of fluid mechanics related to flow rate measurement are recalled. The influence of different physical parameters between them, especially with flow rate, is also underlined. Moreover, when it is useful references to best practices found in standards are also highlighted.
3.1.1.1 Equation-of-state for gases
Ideal Gas law gives the relation that links the temperature of the gas T, its pressure P, its volume V and its particles number n:
PV = nRT
Where P is expressed in Pa, V in m3, n in mol, T in Kelvin and finally R is the universal gas constant (R = 8.314 J/mol/K).
Generally, the quantity r is used, it is defined as: r =MR where M is the molar weigh of the gas (expressed in g or kg per mol). Thus, equation (3.1) can be expressed under the following form:
P = ρ r T = ρMR T Where ρ is the density of the gas (cf. 3.1.1.1.2).
3.1.1.1.1 Molar volume Vm
It is the volume occupied by one mole of gas, noted Vm. From the equation (1), it can be deduced the following relation:
Vm= 0.0224 Nm3/mol This value is valid regardless the type of gas.
3.1.1.1.2 Density ρ
It is the mass of one volumetric unit of gas, noted ρ, expressed in kg/m3. It can be deduced from equation (3.1):
𝜌 = 𝑃
𝑟𝑟= 𝑃 𝑀 𝑅𝑟
As it has been in the foreword of this section, multiple values are expressed under normal conditions for temperature and pressure, then, it is necessary to be able to translate the data measured under industrial conditions, called true conditions, of temperature and pressure (true value) under normal conditions.
(Eq. 3.1)
(Eq. 3.2)
(Eq. 3.3)
(Eq. 3.4)
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𝜌(𝑃, 𝑟) = 𝜌0 �𝑃(𝑇)𝑃0 � �𝑇𝑇0�
It is important to underline that the access to ρ0 requires the knowledge of the gas composition (O2, CO2, SO2, H2, etc. because it is rarely pure gases) and more especially the volumetric fraction of each of its components as well as their density. The density of the mix of gases is obtained by calculating the weighted average of each of the components:
𝜌(𝑃, 𝑟) = 𝑃 𝑀
𝑅𝑟 𝑜ù 𝑀 = 10−2� %𝑋 𝑀𝑋
Where %X is the content of the component X in the gas flow in volumetric percentages (also called volumetric fraction) on humid gas and Mx its molar volume (in kg/mol).
Usually, only the following species are taken into account: O2, CO2, H2O and N2 (that can be deduced from the other species contents: %𝑁2 = 100 − (%𝑂2) − (%𝐶𝑂2) − (%𝐻2𝑂)). The molar volume M of the gas becomes then:
𝑀 = 10−5 (32 (%𝑂2) + 44 (%𝐶𝑂2) + 18 (%𝐻2𝑂) + 28 (100 − (%𝑂2) − (%𝐶𝑂2) − (%𝐻2𝑂)) Illustration: Influence of the temperature on the density ρ
For instance, for a gas composed only of air, with a change of the temperature from 120°C to 140°C, the density will decrease from 0.898 kg/m3 at 120°C to 0.854 kg/m3at 140°C. Thus, in that case, a raise of 17% of the temperature induces a decrease by 5% of the density.
Figure 6: Evolution of the density of gas composed of air in function of the temperature
Please note:
- The influence of the pressure and the temperature on the quantity ρ cannot be neglectable.
3.1.1.2 Gas flow rate
The volumetric flow is the flux of fluid which passes through a surface per unit time.
3.1.1.2.1 Volumetric flow rate
The volumetric flow rate links the velocity of the fluid to the section of the fluid flow.
It is expressed as:
𝑄𝑣= < 𝑣 > 𝐴 0
0,2 0,4 0,6 0,81 1,2 1,4
0 50 100 150 200 250 300 350 400 450
Density (kg/m3)
Tmperature (°C)
(Eq. 3.5)
(Eq. 3.6)
(Eq. 3.7)
(Eq. 3.8)
-22-
Where <v> represents the mean output velocity in the cross-sectional area A.
The determination of the area A requires the use of the hydraulic diameter that allows to calculate the surface of any flat surface, it is defined as follow:
𝐷ℎ = 4 𝐴𝐿
Where A is the cross-sectional area and L the wetted perimeter, that is to say, the perimeter of the section that is in direct contact with the fluid (in our field of study, gases flows, it is always the total perimeter of the section).
Thus, it follows:
𝑄𝑣= < 𝑣 > 𝜋 �𝐷ℎ 2 �
2
Please note:
- In the case of a circular pipe, Dh corresponds to the inner diameter of the pipe.
3.1.1.2.2 Mass flow rate
The mass flow rate is expressed in kg/h (or tons per hour) using the following relation:
𝑚̇ = 𝜌0 𝑄𝑣0
Where Qv0 represents the volumetric flow rate under normal conditions, expressed in Nm3/h.
It has to be underlined that the mass flow rate follows the law of conservation:
𝑚̇ = 𝜌0 𝑄𝑣0= 𝜌(𝑃, 𝑟) 𝑄𝑣(𝑃, 𝑟) It can be deduced from the previous equations that:
𝑚̇ = 𝜌0 𝑄𝑣0 = 𝜌(𝑃, 𝑟) 𝑄𝑣(𝑃, 𝑟) = < 𝑣 > 𝑆 𝜌0 �𝑃(𝑟) 𝑃0 � �𝑟0
𝑟 �
The relation (3.13) illustrates that the mass flow rate is inversely proportional to the temperature.
Illustration: Influence of the temperature on the mass flow rate
For instance, for a gas only composed of air, at 120 °C, with a flow velocity of 10 m/s, flowing in a circular pipe with a hydraulic diameter of 1m, at atmospheric pressure, the mass flow rate is 7.05 kg/s that is to say 25.4 tons/h. The change of the temperature from 120 °C to 140°C decreases the mass flow rate by 5% (6.7 kg/s or 24.0 tons/h).
Figure 7: Evolution of the mass flow rate in function of the temperature 0
2 4 6 8 10 12
0 40 80 120 160 200 240 280 320 360 400
Mass flow rate (kg/s)
Temperature (°C)
(Eq. 3.9)
(Eq. 3.10)
(Eq. 3.11)
(Eq. 3.12)
(Eq. 3.13)
-23-
A modification of the gas composition directly impacts the value of the density ρ0 of the fluid. The equation (3) illustrates the direct influence of the gas composition on the mass flow rate since it shows that these two parameters, the mass flow rate and the density of the fluid, are proportional.
Illustration: Influence of the gas composition of the mass flow rate
For instance, for a gas only composed of air, at 120 °C, with a flow velocity of 10 m/s, flowing in a circular pipe with a hydraulic diameter of 1m, at atmospheric pressure, the mass flow rate is 7.05 kg/s that is to say 25.4 tons/h. The raise of the density (and so of the gas composition Cf. 3.1.1.1.2) of 10% increases the mass flow rate by 10%.
Figure 8: Evolution of the mass flow rate in function of the density of the fluid
Please note:
- The volumetric flow rate is almost always expressed under true conditions; thus it is essential to use the value of the density ρ(P,T) under true conditions. To do so, the relation (2) will be used, requiring additional measurements of the temperature T and the pressure P. This is essential for a reliable measurement.
3.1.1.2.3 Volumetric flow rate under normal conditions on dry gas and in reference oxygen content
Besides, in many industrial sites, in order to be comparable, the volumetric flow rate is expressed under normal conditions but also on dry gas and at reference oxygen content (11% of O2). To do so, the following relation is used:
𝑄𝑣,𝑠𝑠𝑠,𝑂2 𝑟𝑠𝑟0 = 𝑄𝑣 𝑃𝑃0 𝑇𝑇0 100−%𝐻100 2𝑂 20.9−%𝑂20.9−%𝑂2
2 𝑟𝑟𝑟
Where Qv is the volumetric flow rate under true conditions, P0 and T0 the pressure and temperature values under normal conditions, %H2O the humidity content of the gas, %O2 the oxygen content under true conditions and %O2 ref the reference oxygen content (expressed in volumetric percentage et often taken as 11%). (FNADE, 2006).
3.1.1.3 Flow regime typology
Two major flow regimes can be defined: the laminar and the turbulent regime. The Reynolds number (noted Re and without dimension) characterizes these regimes. It is defined as follow:
𝑅𝑅 = 𝐷ℎ< 𝑣 (𝑃, 𝑟) >
𝜇(𝑃, 𝑟) 𝜌(𝑃, 𝑟)
Where μ represents the dynamic viscosity expressed in Pi (Poiseuille or Pa.s) and ρ its density (in kg/m3).
0 2 4 6 8 10
1 1,05 1,1 1,15 1,2 1,25 1,3 1,35 1,4 1,45 1,5 1,55 1,6 1,65 1,7
Mass flow rate (kg/s)
Density of the fluid(kg/m3)
(Eq. 3.14)
(Eq. 3.15)
-24- 3.1.1.3.1 Laminar regime: Re < 2100
A flow is said to be laminar when its Reynolds number is below 2100.
In front of this type of flow, it is important to underline that the velocity profile has the particular feature of having the maximum velocity (at the center of the section) corresponding to the double of the mean output velocity (used for the flow rate calculation). This characteristic induces frequent mistakes with punctual measurement techniques such as thermal mass flowmeter or mono-point Pitot tube.
Figure 9: Velocity profile in laminar flow regime
3.1.1.3.2 Turbulent regime: Re > 104
A flow is said to be turbulent when its Reynolds number is above 104.
This type of flow has a quite flat velocity profile. This regime induces less measurement mistakes since the velocity is near uniform with a value very close to the mean output velocity (except close to the walls with the boundary-layer phenomenon).
Illustration: Calculation of the Reynold number in the typical stack flue gases conditions
For instance, the case of an air flow at 120 °C, in a circular pipe of 1m of hydraulic diameter, with a velocity of 10 m/s, the Reynolds number is 39 104: the flow is turbulent.
Please note:
- In the case of a turbulent regime with a steady and developed velocity profile (Cf. figure 11), the point of the profile with a velocity value corresponding to the mean output velocity is located at 12% of the hydraulic diameter from the boundary pipe or at 25% of the radium (source: EN 16911-2).
- During the velocity measurement, it is crucial to know the flow regime in order to adapt the right location of the sensor for a correct measurement of the mean output velocity and so of the flow rate. Yet, for biogas or stack flue gases in waste treatment facilities, the flow regime is always turbulent since the Reynolds number is always equal or higher than 3,60 104 (Cf. 3.1.2.1:
the calculations of the Reynolds number, in the more extreme conditions that could possibly lead to laminar flow, gives a Reynolds number of 3,60 104 ). This is the minimum value that can be found in the scope of this study and it remains higher than 104 which implies that the regime is always turbulent (>104).
<v>
Vmax = 2
<v>
Figure 10: Velocity profile in turbulent flow regime
-25- 3.1.1.4 Flow regime typology
3.1.1.4.1 Entrance (or development) length for a steady flow
For a laminar regime, the length required to fully develop the velocity flow (symmetric, without gyrations and homogeny profile) can be estimated with the following correlation (MARCOUX, 2016):
𝐿𝑠= 0.06 𝐷ℎ 𝑅𝑅
Figure 11: Length entrance for a laminar flow, source: Aerospatiale Department, Fluid mechanics course, University of Sidney
For a turbulent flow, the following correlation can be used (MARCOUX, 2016):
𝐿𝑠 = 0.63 𝐷ℎ 𝑅𝑅0.25
Thus, a flow can be turbulent and steady like the illustration below underlined:
Figure 12: Velocity profile of a steady and turbulent flow
Thus, it clearly appears that having a fully developed and steady profile it is necessary to have a certain straight length upstream and also downstream in order not to disrupt the flow.
Please note:
- For measurement instrument requiring a steady profile, the EN 16911-2 recommends a straight length of 25 Dh upstream the device and 5 Dh downstream it.
Figure 13: Straight length recommendation, EN 16911-2
(Eq. 3.16)
(Eq. 3.17)
-26-
- Nevertheless, the supplier information should be taken into account.
- Moreover, the results of the velocity profile cartographies performed for the pre-studies of the standard EN 16 911-1 (QAL 2 measurements for the choice of the Automatic Measurement System for the flow rate measurement and the validation of the representativeness of the measurement point) and the EN 15259 (homogeneity measurement experiences for all the stationary air emission measurement systems) can reduce these straight lengths.
- Finally, the straight lengths can also vary according to the type of elements upstream (elbow, valve, etc.).
3.1.1.5 Flow rate calculation summary
1- To calculate the density of the fluid under true conditions ρ(P,T), it is necessary to:
- have access to the gas composition (components and their volumetric fractions) then calculate the density of the fluid under normal conditions ρ0
- measure the temperature T and the pressure P in the flow - then use: ρ(P, T) = ρ0 �P(T)P0 � �TT0�
2- To calculate the volumetric flow rate Qv, it is necessary to:
- measure with the most relevant technic (Cf. Technology comparison section) and at a representative point the velocity and assess the mean output velocity <v>
- determine the cross-sectional area A (thanks to the hydraulic diameter Dh) - then use: Qv= < v > A
3- If it is required20, to calculate the mass flow rate, the two parameters above are used:
ṁ = ρ0 Qv0 = ρ(P, T)Qv(P, T)
4- Finally, the Volumetric flow rate under normal conditions on dry gas and at reference oxygen content:
Qv,sec,O2 ref0 = Qv P P0
T0 T
100 − %H2O 100
20.9 − %O2
20.9 − %O2 ref
20 The mass flow rate can be required by intern industry process calculations but it can also be needed in the case of local regulation (local degree, national or regional regulations).
Figure 14: Illustration of the evolution of the velocity profile in presence of an elbow upstream, (COSA Xentaur Corporation; Dr. J. David Hailey, 2015)
(Eq. 3.14) (Eq. 3.12) (Eq. 3.10) (Eq. 3.5)
-27- 3.1.2 Flue gases: a compressible fluid
Generally, the hydraulic theory (liquid fluids theory) is the most known and used. Nevertheless, in the case of stack flue gases study, this theory reaches its limits: its treats incompressible fluids (with a constant density ρ) whereas it could be questioned for gas at elevated pressures.
3.1.2.1 Variation of dynamic viscosity of gases
Several relations are still valid, such as for instance the Reynolds number:
𝑅𝑅 = 𝐷ℎ 𝑣 𝜇 𝜌 =
𝐷ℎ 𝐺 𝜇
Nevertheless, the dynamic viscosity μ of gases varies according to the temperature: its value increases with it.
Typically, for gases, the dynamic viscosity raises by 2 to 5 10 -8 PI by temperature unit T21. Thus, when the temperature raises, μ raises too, and so the value of the Reynolds number decreases. This means that the flow is less and less turbulent: the representativeness of the measurement point is jeopardized compromising the whole measurement value.
Illustration: Influence of the temperature on the Reynolds number
If we consider a gas composed of air, with a velocity of 10 m/s, flowing in a circular section with a diameter of 1m, for a change of temperature from 120°C to 140°C, its dynamic viscosity μ raises by 3.5% changing from 2,30.10-5 Pa.s to 2,38.10-5 Pa.s. Besides, its density decreases from 0.898 to 0.854 kg/m3.
21 The Sutherland Law links the dynamic viscosity to the temperature according to the following relation:
𝜇(𝑟) = 𝜇0∗ �𝑟
𝑟0�3/2𝑟0+ 𝑆 𝑟 + 𝑆
Where µ0 is µ(T0) and S is called the Sutherland temperature and is taken equal to 110.4 K in the case of air.
Figure 15: Flow rate assessment process
(Eq. 3.18)
(Eq. 3.19)
