The subject of this paper is to analyse the infl uence of moisture on selected technical
and combustion characteristics of alternative fuels. The analyses are conducted on the
basis of analyses of samples of alternative fuels simulating states of the fuel in expected
operating conditions, focusing on the identifi cation of potential operational risks. The
fi nal part consists of a set of recommended measures to ensure the operational safety of
the practical use of alternative fuels based on the results of the analysis

Kulich, Martin

TRANSACTIONS of the VŠB – Technical University of Ostrava Safety Engineering Series

Abstract
The subject of this paper is to analyse the influence of moisture on selected technical and combustion characteristics of alternative fuels. The analyses are conducted on the basis of analyses of samples of alternative fuels simulating states of the fuel in expected operating conditions, focusing on the identification of potential operational risks. The final part consists of a set of recommended measures to ensure the operational safety of the practical use of alternative fuels based on the results of the analysis.</jats:p

Martin Kulich

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The Dependence of Selected Technical and Combustion Characteristics of Fire on Moisture Levels in Alternative Fuels

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Transactions of the VŠB - Technical university of OstravaSafety Engineering Series Vol. IX, No. 1, 201425THE DEPENDENCE OF SELECTED TECHNICAL AND COMBUSTION CHARACTERISTICS OF FIRE ON MOISTURE LEVELS IN ALTERNATIVE FUELSMartin KULICH11 Scientifi c-Research Coal Institute (VVUÚ a.s.), Ostrava, Czech Republic, kulichm@vvuu.czAbstract: The subject of this paper is to analyse the infl uence of moisture on selected technical and combustion characteristics of alternative fuels. The analyses are conducted on the basis of analyses of samples of alternative fuels simulating states of the fuel in expected operating conditions, focusing on the identifi cation of potential operational risks. The fi nal part consists of a set of recommended measures to ensure the operational safety of the practical use of alternative fuels based on the results of the analysis.Keywords: Fire, combustion, risk, alternative fuels.Research articleIntroductionThis research and the presented results on this topic are directly related to the long-term cooperation between VVUU (specifi cally the Risk Analysis Division and Accredited Testing Laboratory No. 1025) and ČEZ Group in the area of research and development related to the risks of fi re and explosion associated with alternative and mixed fuels that are suitable for use in conventional power plants in the ČEZ group.This project, "fi re-safety aspects of the use of alternative fuels" funded by ČEZ group a. s., can be divided into two parts, from the perspective of the tested fuel samples, namely:• Alternative fuels based on biomass,• Alternative fuels based on RDF.Within the scope of this research, we will also deal with some solutions in the area of biomass (BM).Materials and methodsDuring selection of fuels for the purpose of the project many requirements and selection criteria were considered to which the samples had to conform (operational-technological, environmental, fi nancial, legislative, etc.). Based on the identifi cation of the above-mentioned factors, each sample was passed through a selection process. These specifi c samples were selected for specifi c operating conditions and tested for various technical parameters of fi re and combustion characteristics (TPFC). The analyses aim at clarifying the behaviour of BM samples at different moisture levels that may actually occur in real-world conditions.In general, it can be said that increasing the moisture content of the sample reduces the susceptibility to fi re/explosion (Štroch, 2010).Specifi cations of the test set of BMBelow are the specifi cations of samples that were selected for analysis, including the specifi cations of test conditions under which the TPFC analyses were performed:   DOI 10.2478/tvsbses-2014-0004Marking of the samples for testing:Sample Specifi cation:Defi ned % moisture for testing TPFC:State: BM1Wood chips (branches, roots and fi bre)20, 30, 40 [% wt.]DustMarking of the samples for testing:Sample Specifi cation:Defi ned %  moisture for testing TPFC:State: BM2Pellets from purpose grown plants10, 15 [% wt.]DustMarking of the samples for testing:Sample Specifi cation:Defi ned % moisture for testing TPFC:State: BM3Sunfl ower plant pellets (husk and seeds)10, 15 [% wt.]DustTransactions of the VŠB - Technical university of OstravaSafety Engineering Series Vol. IX, No. 1, 201426Dust is defi ned [EN 14034-1:2004+A1:2011] as a collection of small solid particles in the air that settle under their own weight, but can remain dispersed in the air for some time. (average size of the dust below 500 micron).Specifi cations of the analysis of TPFCTo ensure the necessary accuracy of the results, all analyses were performed by Testing Laboratory No. 1025 VVUU accredited by the Czech Accreditation Institute (CAI), according to the harmonized European normative test code (EN, 1999; EN, 2011; EN, 2008; EN, 1998).1The specifi cations of the TPFC analysis, together with the indicated regulation norms that defi ne the test procedure and defi ned specifi cations of the selected tests from the perspective of operational experience and practical solutions for the prevention of explosions during operation in industrial plants are shown in Tab. 1.ResultsDuring the course of the project, a wide range of results characterizing the parameter changes in TPFC for BM when moisture content is changed was observed. For the purposes of this contribution, the conclusions of the sample values of TPFC and the important comparisons of the selected samples that take place are, concretely:• Ignition temperature of dust clouds for part of the samples of BM - Fig. 7,• Induction period for part of the samples of BM - Fig. 8,• The speed of the spread of fi re upon a sample layer of settled dust for part of the samples of BM - Fig. 9.Setting and verifi cation of the moisture levelThe sample was dried in a drying oven at 103 ± 2 [°C] to a constant weight. Drying was verifi ed through basic chemical analysis. On the basis of the results, the estimated amount of water was added and the target moisture level of the sample was verifi ed using basic chemical analysis.Summarization and comparison of the observed values of TPFCIn Fig. 7, 8 and 9 is a summarization and comparison of the observed results.1 Test procedure from the requirement ČSN 015140-3 that was eliminated 1. 2. 2003 without a replacement (ČSN, 1985; Damec and Šimandl, 2005).DOI 10.2478/tvsbses-2014-0004Marking of the samples for testing:Sample Specifi cation:Defi ned % moisture for testing TPFC:State: BM4Grass Pellets10, 15 [% wt.]DustMarking of the samples for testing:Sample Specifi cation:Defi ned % moisture for testing TPFC:State: BM5Briquettes10, 15 [% wt.]DustMarking of the samples for testing:Sample Specifi cation:State: BM6Palm Husks (15 wt. %) + Black Coal (85 wt. %)Black Coal - Dust, Palm Husks - GroundFig. 3 BM3 - Sunfl ower plant pellets (husk and seeds)/dustFig. 1 BM1 - Wood chips/dustFig. 5 BM5 - Briquettes/dustFig. 4 BM4 - Grass pellets/dustFig. 2 BM2 - Pellets from purpose grown plants/dustFig. 6 BM6 - Palm Husks/ground + Black Coal/dustTransactions of the VŠB - Technical university of OstravaSafety Engineering Series Vol. IX, No. 1, 201427DOI 10.2478/tvsbses-2014-0004Flashpoint/Ignition temperature of powder (EN 50281-2-1)The fl ashpoint of settled powder is the lowest ambient temperature at which an external ignition source is able to ignite the gasses of the thermal decomposition. The ignition temperature of the settled powder deposits is the lowest ambient temperature at which the in the absence of an external source of ignition spontaneous ignition of the gaseous pyrolysis products is possible.Ignition temperature of dust clouds (EN 50281-2-1)The lowest ambient temperature at which gaseous products from thermal decomposition ignite even in the absence of an external ignition source. This value is important in determining the risk that a mixture of dust and air would ignite on the hot surfaces of equipment.Lower Explosive Limit (EN 14034-3+A1)The lowest concentration of a combustible dust in air, at which the mixture is explosive. The value of the lower explosive limit for powdered materials is given in the unit [g.m3].Maximum Explosion Pressure (EN 14034-1+A1 EN 14034-2+A1)The maximum pressure resulting from an explosion of explosive dust in a closed container under specifi ed test conditions where the dust/air mixture is at optimal levels. This is the maximum pressure that the substance is able to create in a closed vessel during an explosion. The value of this parameter is important for the proper design of explosion protection equipment (relief diaphram, fl aps and valves).Maximum speed in rise in pressure (brisance) (EN 14034-1+A1 EN 14034-2+A1)The maximum value of the rise in pressure per unit of time resulting from the combustion of a range of fl ammable dust substances in a closed vessel under specifi ed test conditions.KSt Constant (EN 14034-1+A1 EN 14034-2+A1)The cubic constant. It expresses the brisance of a dust air mixture regardless of the volume in which it was established. According cubic constants, dust is classifi ed St1 to St3, the St3 class explosion is the most dangerous.Limit Oxygen Concentration (EN 14034-4+A1)The limit of oxygen content is the experimentally determined concentration of oxygen, which does not allow an explosion of the mixture of fuel, air and inert gas. It is used in the area of equipment protection by rendering the environment inert.Determination of susceptibility to spontaneous combustion (EN 15188)The self-ignition temperature is defi ned as the lowest temperature at which a substance ignites itself without the application of an external ho[t exothermic processes. The heat required to ignite the substance arises from the substance itself as a result of chemical, physical or biological processes. The term self-ignition is to be understood not only the ignition of the substance, but the aggregate on-going process from the fi rst temperature increase (= self-ignition temperature), until reaching the ignition temperature.Minimum Ignition Energy (IEC 1241-2-3)The minimum ignition energy is the lowest possible energy an ignition source needs to ignite a substance in the optimal concentration.Rate of the spread of fi re of a layer of dustThe rate a fi re spreads is determined by the amount of time it takes to transfer combustion in the opposite direction of the fl ow of oxygen from a predetermined distance.Tab. 1 TPFC analysis/norms/commentsFig. 7 Ignition temperature of dust cloudsTransactions of the VŠB - Technical university of OstravaSafety Engineering Series Vol. IX, No. 1, 201428ConclusionBefore drawing conclusions from the analysis of TPFC carried out within the project, it is necessary to point out some important facts.In order to comply with the requirements of the test procedures (thus, among other things, ensuring the reproducibility of individual tests) it is often necessary to test samples before the start of the analyses to adjust to the condition, which is required by the individual test procedures and methodologies.One of the essential steps in the process of preparing samples for the analysis of TPFC itself is often to modify the characteristics of the grounds, drying, etc., so that the tested samples were observed at the most critical (most dangerous) values for each factor of TPFC. Knowledge of the "maximum" value is particularly important in the design and implementation of industrial explosion protection.The values TPFC and the resulting conclusions apply only to the tested set of fuels. Based on the results of the tests performed it is clear that it confi rms the assumption that with increasing moisture content of the test sample the BM, there is a decrease in the susceptibility of samples to ignite and initiate in general (increasing ignition temperature when settled and when in the form of dust clouds). It also shows that a higher percentage of water content results in the need for higher dust concentrations for the formation of explosive atmospheres (higher /lower explosion limit) and signifi cantly reduces the intensity of an explosion event (which gives us values such as pmax, brisance, KSt).This behaviour can be derived not only on the sample BM1 but it can be safe to assume that at a water content of > 40 %, the fuel already displays this characteristic and does not exhibit explosive properties - it can then be concluded that this will be the case in response to varying moisture levels of the samples when these conditions occur in real industrial environments.Another important fi nding is that all the tested samples in all test conditions (i.e. different humidity levels) exhibited susceptibility to spontaneous DOI 10.2478/tvsbses-2014-0004Fig. 8 The Cubic Constant, KStFig. 9 The rate of the spread of fi re on a layer of dustTransactions of the VŠB - Technical university of OstravaSafety Engineering Series Vol. IX, No. 1, 201429combustion, which is essential information especially in terms of their long-term storage in large piles. The result of the susceptibility of the test set of alternative fuels to auto-ignite corresponds with what is currently known on this issue (Balog, 1999).The burning of alternative fuels, and their co-incineration in equipment that was originally designed for the combustion of classic fuels, is not, especially in energy higher levels, anything unusual. Alternative fuels have specifi c characteristics which, in turn can cause security risks in the various stages of storage, transportation, treatment and combustion itself.In the cases of incineration, co-incineration and a modifi ed fuel base, it is always needed to analyze and evaluate the risks, and not only in terms of explosion prevention. In the area of explosion prevention the basic regulation Government Regulation No. 406/2004 Coll. (Government Regulation, 2004), which in § 4 point d) imposes on the operators the requirement for the processing and maintenance of written documentation of explosion prevention. This regulation can be understood such as rule, by means of which the Czech Republic is implementing the requirements of the European Parliament and Council Directive 92/99/EC (Directive, 1999) (often known under the name of ATEX 137).One of the pillars of the risk analysis of any technology is thorough knowledge of the material properties - in the form of fi re and explosion characteristics that will occur in the technology (in this case, the fuel or fuel mix). The requirement for technical knowledge of fi re and explosion characteristics of processed and stored materials is also defi ned by the Decree of the Ministry of Interior No. 246/2001 Coll (Decree, 2001).Finally, proper risk analysis must always be clearly and unequivocally based on whether the technology can be considered safe for its operation with a new fuel base, and/or what technical or organizational measures must be taken to do so.Quality and comprehensive risk analysis and the application of technical and organizational measure that are defi ned in it, in the past, has been proven many times to go beyond the protection, safety and health of workers at the workplace as well as saving much in the form of the value of equipment and downtime.DOI 10.2478/tvsbses-2014-0004ReferencesBALOG, Karol (1999). Auto-ignition: self heating, ignition, fi re. 1st ed. Ostrava: Association of Fire and Safety Engineering. (in Slovak)ČSN 015140:1985. Cobustible dusts. Methods of testing. Determination of the rate of fl ame propagation on deposited dust layer. Praha: Úřad pro normalizaci a měření. (in Czech)DAMEC, Jaroslav and Ladislav ŠIMANDL (2005). Laboratory Practice explosion prevention technology processes. Ostrava: Association of Fire and Safety Engineering. ISBN 80-86634-57-4. (in Czech)Decree (2001). Establishing the conditions for fi re safety and state fi re supervision (Fire Prevention). In: Journal of Laws of 2001, No. 95. Directive (1999). Directive of the European Parliament and Council Directive 1999/92/EC of 16 December 1999 ominimálních requirements for improving the safety and health protection of workers potentially at risk from explosive atmospheres (also called ATEX 137). In: Offi cial Journal of the European Union. EN 50281-1-1:1999. Electrical apparatus for use in the presence of combustible dust - Part 2-1: Test methods - Methods for determining the minimum ignitron temperatures of dust. Praha: Český normalizační institut. (in Czech)EN 14034-1+A1:2011. Determination of explosion charakteristics of dust clouds - Part 1: Determination of the maximum explosion pressure pmax of dust clouds. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví. (in Czech)EN 14034-2+A1:2011. Determination of explosion charakteristics of dust clouds - Part 2: Determination of the maximum rate of explosion pressure rise (dp/dt)max of dust clouds. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví. (in Czech)EN 14034-3+A1:2011. Determination of explosion charakteristics of dust clouds - Part 3: Determination of the lower explosion limit LEL of dust clouds. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví. (in Czech)Transactions of the VŠB - Technical university of OstravaSafety Engineering Series Vol. IX, No. 1, 201430EN 14034-4+A1:2011. Determination of explosion charakteristics of dust clouds - Part 4: Determination of the limiting oxygen concentration LOC of dust clouds. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví. (in Czech)EN 15188:2008. Determination of the spontaneous ignitron behaviour of dust accumulations. Praha: Český normalizační institut. (in Czech)EN 15357:2011. Solid recovered fuels - Terminology, defi nitons and descriptions. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví. (in Czech)EN 15395:2012. Solid recovered fuels - Specifi cations and classes. Praha: Úřad pro technickou normalizaci, metrologii a státní zkušebnictví. (in Czech)Government Regulation (2004). The detailed requirements for ensuring safety and health at work in potentially explosive atmospheres. In: Journal of Laws, 2004, No. 131. (in Czech)Government Regulation (2006). Government Regulation No. 393/2006 Coll on the minimum safety and health at work in explosive environments. In: Journal of Laws č.393/2006, amounts 140. 2006.IEC 1241-2-3:1998. Electrical apparatus for use in the presence of cobustible dust - Part 2: test methods - Section 3: Methods for determining minimum ignitron energy of dust/air mixture. Praha: Český normalizační institut. (in Czech)KULICH, Martin (2012). Application of alternative and mixed fuels in line with the guiding principles to ensure safety explosion in conventional energy. In: KULICH, Martin. Fire Protection 2012: Proceedings of the 2012 XXI of lectures. annual international conference. Ostrava: Association of Fire and Safety Engineering. (in Czech)ŠTROCH, Petr (2010). Processes of fi re and explosion. Žilina: EDIS - Publishing University of Žilina. ISBN 978-80-554-0187-4. (in Czech)DOI 10.2478/tvsbses-2014-0004

The dependence of selected technical and combustion characteristics of fire on moisture levels in alternative fuels

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The dependence of selected technical and combustion characteristics of fire on moisture levels in alternative fuels

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