fate of chlorine compounds in combustion of alternative fuels

FATE OF CHLORINE COMPOUNDS IN COMBUSTION OF ALTERNATIVE FUELSKamil WICHTERLE, Jan CIESLAR, Antonín KLEČKA, Zdeněk KLIKA and Václav ROUBÍČEKDepartment of Chemistry, VŠB TU Ostrava, 70833 Ostrava Poruba, Czech RepublicCorresponding author‘s e-mail: kamil.wichterle@vsb.cz(Received xxxx 2005, accepted xxxxxxxxx 2005)ABSTRACTMost of natural materials contain traces of chlorine and it enters also to the combustion process. Chlorine products ofcombustions are usually inorganic hydrogen chloride vapors and chloride salts, nevertheless smaller amount of organicchlorine compounds are formed. Simpler of these organic compounds can act as greenhouse and ozone depleting gases;more complex compounds are directly dangerous for their mutagenity or extreme toxity like so called dioxines. Nonfossilnatural materials and fuels derived of them can contain more chlorine than common coal. From the publishedresearch studies is evident that the formation of organochlorine compounds is limited to the temperature range 300-800°C. At the higher temperatures, these compounds are destroyed. In the stage of flue gas cooling some chlorine maybe by a "de novo" synthesis introduced to the organic form. Well-controlled combustion of alternative fuels need notcontribute to the increase of amount of emissions of dangerous chlorine compounds. In our research were moreoverstudied the fuels with lower chlorine content. The experimental tests of the emissions from large-scale industrial fluidbed boiler indicated that substitution of large percentage of coal by alternative fuels had no significant effect.KEYWORDS: chlorine, dioxin, combustion, alternative fuel1. INTRODUCTIONDemand to reduce the greenhouse gasproduction turns the attention to the substitutionof fossil fuels by waste wood and agriculturalresidua, that were in past composted or not treatedanyhow. Various solid wastes from biorefineriesof food, pulp and paper production, textile fiberindustries, organic sludge from wastewatertreatment can be employed as well. Highpercentage of combustibles is also contained insolid mixed communal wastes and there aresimilar problems with employment of the relatedenergy.More and more effects of combustion to theenvironment have been systematically monitoredrecently. First, the attention was paid to thesmoke and flue ash. The smoke is no moreconsidered as a symbol of prosperity. Nextcontaminants under examination were sulfurdioxide and nitrogen oxides known as cause ofacid rain. Today, carbon dioxide and of otheressentially inert components like volatile organiccompounds and nitrous oxide, that can affect theozone layer and contribute to the greenhouseeffect are monitored. More attention is paid to theminor components like compounds of heavymetals and halogens, chlorine in particular.The chlorine compounds belong to the toxics,carcinogenics, ozone depleting species. Therefore,prudence is necessary, when introducing them tothe combustion process. In this paper, we arestudying the problem of chlorine duringcombustion of biomass and other alternative fuelsin industrial boilers. All lignocellulose materials –derived from wood, bark, straw, rice hulls,baggase, etc. contain some chlorine. Lowestpercentage is 0.1 % of Cl in dry matter ofconstruction (cellulose) and storage (starch) parts,the specialized cells contain up to 1 % Cl, higherpercentage can be detected in plants from salinesoils. During the biomass combustion, this chlorineenters number of chemical reactions producingproblematic compounds. As the amount of chlorinefed can hardly be limited, it is necessary to controlthe process to minimalize the non-demandedreactions.2. CHLORINE COMPOUNDS IN THE ENVIRONMENTThe chlorine compounds on the Earth occurmostly as chemically stable and non-dangerouschlorides, either dissolved in oceans or stored incrystal form underground. However, lowconcentration chlorine is scattered everywhere and itis irreplaceable for any living organism. Also anatural chemical transformation of chlorinecompounds and their movement is significant. Tocompare, the complete industrial production ofchlorine is about 40 millions tons yearly. Onemedium size volcano eruption may evolve nearly onebillion tons of hydrogen chloride. Production ofhighly reactive elementary chlorine byphotochemical reactions of chlorides at the sea levelis estimated to 800 millions tons per year.Chlorine from the biological materials is releasedduring slow decomposition, during natural fires andduring controlled combustion, preferably asinorganic chloride compounds. In any case, smallfraction of organo-chlorine compounds is formed,like methyl chloride (0.5 million tons/year),1

chloroform (0.7 million tons/year) and compoundsof the toxic group of dioxins PCDD/F (170kg/year).Industrial employment of chlorine was oriented in19.century to the production of bleaching powder,calcium hypochlorite, for bleaching of textiles andpaper and for disinfections. Water chlorination intowns started around 1900. Short episode withelementary chlorine and organo-chlorinecompounds as war gases lead to the developmentof efficient pesticides known as DDT, HCH, PCP,etc. Chlorinated hydrocarbons became used assolvents, chloroprene resin and a wide scale ofpharmaceutics was developed. Polychlorinatedbiphenyls (PCB), now forbidden as toxics, hadbeen excellent transformer oils. Chemical stabilityand simple liquefying of chlor-fluorinatedhydrocarbons (freons) was employed inrefrigerators and in sprays. An interesting effect ofhalogenated hydrocarbons is fire inhibition andtheir use as fire retardants and fire extinguishingliquids. An important consumption of chlorine isin manufacture of PVC, which is a still verypopular plastic with a wide application.Fast development at the beginning of the 20 thcentury was accompanied with a low level ofdiscipline at manufacture, transport, storage andapplication of chemicals, and little attention waspaid to the industrial emissions.One important turning point is dated 1976, whenin Italian locality Seveso in a carelesslyabandoned reactor for production of 2,4,5-trochlorphenole (intermediate for disinfectants)started uncontrolled spontaneous reaction and theaerosol cloud containing (Bluemler, 2005) 0.2 to 5kg of polychlorinated dioxins escaped. Largeresidential area was evacuated and next 4 yearswere spent by the place decontamination. Thisaccident initiated development of so called ECSeveso II Directive (EC, 1996), internationallyaccepted rules for prevention of industrialaccidents and limiting of their eventualconsequences. It results increasing safety ofchemical industry processes and alsomedialization of even banal cases of breakdownand spill.3. "DIOXINS"In the focus of our interest is a group ofpersistent chlorinated compounds derived fromdibenzodioxins and dibenzofurans. Only 17 of thetotal number 210 of these compounds; just thesecontaining chlorine at least in positions 2,3,7,8 arecategorized as toxics. Common acronym for thesepolychlorinated dibenzo-p-dioxins (PCDD) andpolychlorinated dibenzo-p-furans (PCDF) isPCDD/F, however the simple term "dioxins" isfrequently used in unqualified slang.The most dangerous is 2,3,7,8 tetrachlorodibenzo-pdioxine.It is a solid material (melting point 259°C)practically insoluble in water; it can be dissolved inorganic solvents and in fat. Its lethal dose differs forvarious animals, the extremes are 0.6 µg /kg forguinea pigs (Schwetz et al., 1973) and 5000 µg /kgfor hamsters (Henck et al., 1981) Data for othertested animals (mink 4, rats 10-4000, chicken 20,monkey 70 µg /kg) are inside this interval. It isformed in traces during decomposition of anyorganic matter in presence of chlorine compounds. Itis formed naturally during the wood and savannafires mostly as a component of ash. Aerosolsdistribute PCDD/F throughout land and resultingnatural background in soils is about 20.10 -12 g pergram of dry matter. The PCDD/F compounds arealso produced by slow decomposition of biomass incomposts. Due to the development of organochlorinechemical industry and extensive applicationof chlorinated agrochemicals, it is possible to traceenormous content of persistent chlorinatedcompounds in sediments from the period 1930-1960.Since 1960, the concentration of androgenic chlorinecompounds in environment steadily and significantlydecreases(Yake, 2005), (Verta et al., 2004). Toxicityof all PCDD/F is summarized by the toxicityequivalent I-TEQ, calculated as a sum of actualcontent of particular derivate multiplied by the factorI-TEF. I-TEF is equal to unity for the most toxic2,3,7,8-CDD and the other coefficients are derivedfrom The factors are considerably smaller than one,e.g. for the1,2,3,4,6,7,8,9 derivate it makes only0,001.Very complex literature review and analysis of9O81289 1276Odibenzo-p-dioxin4376O34dibenzo-p-furanFig. 1 Formulas of basic compounds and numbering of position of eventual chlorine derivates in PCDD/F2

the chemistry of PCDD/F, their formation andeffects can be found in documents of U.S.Environmental Protection Agency presentedrecently (EPA, 2005). This set of papers isdeclared as a draft, which cannot be quoted yet.Nevertheless, it represents several thousands ofpages of valuable information with more than1200 references.Anything like a safe limit of PCDD/F in food hasnot been declared. Present level 1 pg/(kg day) inEuropean industrial countries is considered to beacceptable. Lethal poisoning of humans bydioxins is unknown; in fatal cases dioxinsrepresent at most a minor component besidesother evidently toxic compound. There are onlytwo well-documented cases of serious acutepoisoning of humans by dioxins. In the recentcase, Ukrainian politician Yushenko accumulated1000 µg I-TEQ in his body (for comparison itcorresponds to the consumption of 150 tons ofmeat from a bad locality containing 6 pg/kg).Release of chlor-organic compounds,containing significant amount of dioxins, takingplace in Seveso, cased solely acute burns of skinand mucous membranes, comparable with verylow exposition of war gases of yperit type.Chronic effects like immune suppression, birthdefects, hormonal imbalance, increasing cancerincidence etc. were proved for laboratory animals.However evaluation of the data for less than 500people exposed to dioxins in Seveso is insufficientto discriminate any statistically significant longtermeffects. Other investigation of humanexposure concerns Vietnam, where defoliantsAgent Orange were applied for 10 years in largeextent (70 thousands tons of chlorinated dioxins,mostly not belonging to the compounds listed astoxics; nevertheless, the release of minorimpurities could make 300 kg I-TEQ that time).Even here, the correlation of the health effects tothe dioxin exposition is not statisticallysignificant, when taking also in account the warstress, bad regimen and other synergic effects.Some intermediates of these defoliants wereparadoxically purchased in communistCzechoslovakia (mainly fom Chemko Strážske,and Spolana Neratovice). With respect to the lowtechnical level and to the secrecy measure, we canonly roughly estimate that more than 80 personsin the Spolana chlorphenol plant sufferedchronically or acute poisoning by dioxins thattime.One result of activities related to the SevesoDirective is inventory of sources, emissions andimissions of PCDD/F. Reduction of PCDD/Femissions became an important criterion oftechnical culture of industrial processes, withoutrespect to the discussions how the given technologiesare important for the environment.4. ANTHROPOGENIC SOURCES OF PCDD/FToxic PCDD/F have not been anytime purposelyindustrially produced and their minute laboratorypreparation is limited to the production of analyticalstandards.Unintentionally, PCDD/F are formed during thermaltreatment and combustion anytime, when tar or sootand hydrogen chloride is released in presence ofoxygen. In industrial countries, 75 % ofanthropogenic emissions originate in following foursources:- incineration of mixed waste,- agglomeration of feed for metallurgy plants,- local furnaces (stoves, boilers, fireplaces, openfires),- hospital incinerators.Surprisingly, neither thermal power stations, norlarge dangerous waste incinerators are listed. Onereason is that production of PCDD/F depends mainlyon the thermal regime of the process, composition ofthe fuel being less important. The emissions ofdioxins from chemical plants during regularoperation are also less significant in the total balance.5. PCDD/F EMISSIONS FROM THE COMBUSTIONPROCESSESPCDD/F can come to the emission by three ways:1. In a simple case, dioxins are present in the fuel.It concerns waste incinerators; in particular theincinerators for liquidation of dangerous wastematerial with high chlorine content. However,99.99 % conversion of dioxins destruction isreached in 1 s at 980°C; in this region thereaction speed ten times multiplies for every 80K temperature increase (Shaub and Tsang,1983).2. In temperature range 300-800°C pyrolysis takesplace in organic compounds producing aromatichydrocarbons and chlorinated aromatics inpresence of chlorine compounds. Later also morecomplex compounds PCDD/F are synthesizedunintentionally.3. As mentioned at high enough temperature, allorganic compounds are broken to small simplemolecules. Nevertheless, in the stage of flue gascooling, number of synthetic reactions takesplace and PCDD/F are formed by the mechanismcalled "de novo". When alkali metals arecaptured by sulfur dioxide or by amphotericoxides, there remains volatile hydrogen chloride.It is oxidized by the Deacon reaction withoxygen at 300°C to extremely aggressiveelementary chlorine. And at the sametemperature are usually present somehydrocarbons that can be attacked. About 1.5 %3

of chlorine enters chloromethane andchloroform. Polyaromatic hydrocarbons(PAH) of tar are also chlorinated and formchlorbenzene and number of precursors ofPCDD/F synthesis. Important catalysts arecopper compounds. De novo synthesisdepends on- the residence time at the temperature 300-800°C (important measure for preventionof dioxin formation is fast cooling of fluegas),- presence of flue ash (the reactions runwell on its surface),- presence of metal compounds as catalysts(copper in particular),- content of soot and inorganic chlorides influe ash (they catalyze the formation ofchlorinated PAH),- presence of oxygen (it releases elementarychlorine from chlorides).These principles are mostly qualitative. Withrespect to the small content of dioxins, theircomplicated and expensive analyses, an tosynergic effect of a great number of compounds,changing their composition in combustionprocesses, there have not been completed relatedthermodynamics data yet. Important fact is thatconcentration of chlorine in fuel is not consideredto be essential. 10-100 µg I-TEQ is formed bycontrolled combustion of 1000 kg of coal orbiomass. This amount of fuel contains usuallymore than 1 kg of chlorine (0.1 %), which iscomparatively so much that it can hardly affectthe equilibrium.Typical path of controlled combustionintermediates and products is presented in Fig.2.The balance is based on 1000 kg of coal, which isone-minute consumption of medium-sizeindustrial boiler.6 MAIN SOURCES OF DIOXINS1. Local residential furnaces like stoves, boilers,fireplaces and open fires represent anextended number of small, distributedsources. Their main disadvantage isuncontrolled regime and frequent operationout of the optimum conditions (application ofimproper or non-uniform fuel, wrong controlof air supply, start-up and shut-down period,extremely slow or fast fuel loading, etc.)Essential feature of the combustion in smalllocal furnaces is moderate temperature. Justthe problematic range 300-800°C, wherePCDD/F are formed and not destroyed isusual. Flue gases are not treated, lot of flueash is dispersed and large amount ofdangerous chemicals is emitted to theenvironment. It is reason why the leading areasin the world balance of chlorine emissions areChina, India, Africa and Latin America. Duringthe regular combustion of 1000 kg of dry wood,the stoves emissions are 1-3 µg I-TEQ, forfireplaces and open air fires it is up to 30 µg I-TEQ/ton. During combustion of fuel with highchlorine content like waste wood treated withchlorine containing insecticides and fungicidesthe production of dioxins increases and 500 µg I-TEQ/ton. Common backyard burning ofapparently inert waste material from householdand gardening is significant source of PCDD/F indeveloped countries. It was estimated thatbonfires and fireworks celebrating the GuyFawkes Day every November released about14% of 1-year dioxins emissions in Britain.Destruction of PVC insulation from copper wiresby uncontrolled combustion is reprehensible,though it can be safely done in industrialtechnologies.2. Due to non-uniformity of feed and its lowercalorific capacity in waste incinerators, there isusually a significant of temperature oscillationand a higher probability to operate in below800°C. Chlorine is usually present in the feedand large amount of fly ash containing numberof metallic elements is present. The most ofPCDD/F either from feed, or from lowtemperature incineration, or produced de novo iscaptured as a solid part of fly ash. In the wellcontrolledwaste incinerators, like in theindustrial coal fire boilers, all fuel is subjected tosuch a high temperature that any chlorinatedorganic compounds are decomposed and de novosynthesis is suppressed by fast cooling of fluegas. Measurements (Lahl et al., 1991) werecarried out in a municipal waste incineratorwhere 90 µg I-TEQ/ton was fed, the relatedemissions contained 9 µg in bed ash, 0.9 µg influe ash and 0.5 µg in gas stake emissions. Someadvanced technologies recommend to remove ina second step the PCDD/F adsorbed on the flueash by baking and to liquidate them separately.3. Iron ore sintering plants are forming granulesfrom iron ore and steelmaking dust by heatingwith coke dust. Nonferrous metals, includingcopper in form volatile chlorides are present inrecycled dust. Comparatively slow heating ancooling with a long residence in the undesirabletemperature range is essential for synthesis oforganochlorine compounds. The most ofPCDD/F condense on released as a airborneparticles. Part of the dust is dumped as adangerous material, the other part is returned tothe steelmaking process. Anyhow, vast amountof aerosol is emitted. The iron ore sinter plants4

are major sources of airborne PCDD/Femissions (Rappe, 1992), (Lexen et al., 1993),(Lahl, 1993 and 1994).4. Another important class of PCDD/F emissionsare medical waste incinerators. They shouldmanage in number of localities heterogeneousmicrobiologically contaminated material. It isdone in comparatively small facilities withsimple (if any) treatment of flue gas.Emissions up to 5000 µg TEQ/t are reported.Though high percentage of PVC in hospitalwaste is usually suspected, this level ofemissions goes evidently on account of badcontrol of combustion in outdated kind offurnaces.Any numbers concerning the concentration ofPCDD/F and their inventory should be takencritically. Even the highest concentrations are sosmall that it requires special analytical tools. Price ofone analytical test is charged in hundreds of US$.Moreover, there is a serious problem of sampling.Scatter of the data is considerable, which isfrequently misused to declare biased conclusions byopposing camps of “chlorophiles” and “ecologists”.Polychlorinated dioxin-like compounds stays vaporat elevated temperatures only. The significant part ofthese compounds rapidly settles on any solid surfacesof aerosols, ash and equipment walls, later in theenvironment on plant leaves, soil and water surfaces.Later path of dioxins and their very slowdecomposition cannot be simply traced. Moreover,the imission data interfere with a backgroundoriginated in former accidental forest and savannafires.10 t 1 t 100 kg 10 kg 1 kg 100 g 10 g 1 g 100 mg 10 mg 1 mg 100 µg 10 µg 1 µg 100 ngN 2NO xchlormethanschlorbenzenesCO 2H 2 OCOPCDD/FhydrocarbonsPAHSO 2HClCl 2HgFLUE GASKClheavy metalsFLUE ASHPCDD/FSiO 2 ,Al 2 O 3 ,CaSOFe 2 O 3 .. 4.K 2 SO 4BOTTOM ASHN 2 O 2AIRC H OcombustiblesSKClashheavy metalsHgINPUTCOALLIMESTONEFig. 2 Estimate of quantitative amount of particular components for combustion of 1000 kg coal in a fluid bed boiler withdry desulfurization5

7. ENERGY FROM BIOMASS AND ALTERNATIVEFUELSEnergy from biomass and alternative fuelsis on issue in last decades. Massive support ofrelated activities comes even from USgovernment, without respect to its quite reservedapproach to the commitment to reduce emissionsof carbon dioxide. US Department of Energy(DOE, 2001) is proposing to substitute 15 % ofcoal by biomass in power stations up to 400 MW.11 large scale facilities just operate in USA. Themost of them use powder burners, single plant inTacoma (Hannan and Rottler, 2005) has a fluidbed boilers 2×25MW. 5 facilities are reported inEurope, the most significant are straw powerstations in Denmark.Different granulometry classes of the sizeand shape of fuel particles may destabilize thefluid bed, formation of plugs and short circuitscan be obtained namely when the particles arenon-uniformly distributed (Kostamo, 1999)Respective oscillation of temperature can provokeformation of polyaromatic hydrocarbons (PAH), andpersistent organic pollutants (POP) includingchlorine compounds up to PCDD/F. Even minoramount of transition metals compounds stronglyaffect composition and structure of bottom ash andflue ash.Thinner ash particles from biomass moreeasily deposits on the walls and heat transfersurfaces. In presence of alkali metals they may formhard glassy layers. Important prerequisite of largescaleuse of alternative fuels is just a successfulsolution of the problems of crusts and corrosion(Sami et al. (2001).To investigate these potential risks, the effectof addition of several alternative fuels to coal wasstudied experimentally in an industrial fluid bedcombustor.8. EXPERIMENTALThe experiments have been carried out in175 MW fluid bed boiler K11 in the paper millFranschach Štětí. The equipment is described indetails in other parts of the presented research report.Tab.1 Mass, energy and chlorine flow in the combustion processRun: 1 2 3Material balancecoal kg/h 30000 35000 26700wood and bark chips kg/h - 19800 15200sewadge sludge kg/h - - 15200refuse-derived-fuel kg/h - - 1000limestone kg/h 3490 4320 3240bottom ash kg/h 3670 4770 3710fly ash kg/h 5510 7180 5560flue gas Nm 3 /h 167000 242000 247000Energy of fuelcoal MW 123 139 107organic fuels MW - 31 46total MW 123 170 153Temperaturefluid bed °C 880 850 830residence time s 4 4 4cooling time s 4 4 4stack °C 160 160 160Chlorine balancecoal kg/h 15.5 10.6 8.3wood and bark chips kg/h - 4.4 3.4sewadge sludge kg/h - - 0.3refuse-derived-fuel kg/h - - 0.1limestone kg/h 1.4 3.5 3.1bottom ash kg/h 5.8 6.3 4.2fly ash kg/h 6.4 7.2 5.4flue gas kg/h 4.7 6.3 5.5Copper inputtotal kg/h 0.6 0.9 1.0PCDD/Fflue gas µg/h 1.7 2.9 3.76

The research has been supported by the GrantAgency of the Czech Republic as a project GACR101/03/1402.The boiler was designed for lignite; thesupply comes from North Bohemian Brown CoalDistrict (Most Basin). As alternative fuel,following materials have been tested:- wood chips with bark from pulp plant,- paper mill sewage sludge,- refuse-derived fuel containing chopped paper,textile and plastics from municipal waste.As shown in Tab.1, the applied alternativefuels do not bring into the balance any essentialinput streams of chlorine. Wood and bark chipscontain 200 ppm Cl, the sewage sludge 20 ppmCl, and the applied refuse-derived fuel 130 ppm.The more important is content 300-520 ppm Cl inthe lignite. Surprising fact is comparatively largecontent of Cl in the limestone used fordesulfuration.Analysis of composition of particulate streamsproved that:- chlorine content in alternative fuel was lowerthan in coal of the same mass and even thesame thermal content- content of copper and other heavy metals inalternative fuel was considerably lower than incoal itself,- content of alkali metals in alternative fuel wasalso lower than in coal.With respect to the above facts, the alternativefuel applied does not bring any problems in itschemical composition. Potential problem mayoccur in the effects to the temperature regime inthe fluid bed, caused by non-uniformity and lowerthermal content of the fuel.Basic data on the chlorine streams andtemperatures are presented in Tab.1. Evidently,distribution of chlorine to the emissions – bottomash, flue ash and flue gas in stack - has not beenchanged significantly. It can be assumed that thechemical speciation of the stream has not vary aswell. Presented data on PCDD/F supports thisstatement.9. CONCLUSIONLow emission of dioxins is a criterion oftechnological excellence of the combustion anddownstream processing of flue gas. It is a wellknownfact, that content of PCDD/F dependsprimarily on the uniformity of combustion andtemperature regime in the bed and in the way offlue gas cooling and ash separation. Content ofchlorine within the limits (0.1-1 kg Cl per 1000 kgof fuel) has a minor effect. The most of thechlorine is retained in ash as environmentallyfriendly or at least inert inorganic compounds, lessthan 0.1 % of chlorine input is emitted in flue gas asvolatile organic compounds. Content of toxicpolychlorinated dibenzo-dioxins and dibenzo-furansis seven decadic orders lower, i.e. few hundredsnanograms per ton of fuel. Even the large powerplants using low grade coal containing seriousamount of chlorine are not classified as a mainsource of PCDD/F.In this work, these assumptions were checked forthe fluid bed boiler 175 MW with dry desulfurationduring combustion of alternative fuel. There are twopotential reasons for worsening the emissions foralternative fuel. First, it may be increasing input ofchlorine with fuel. It was not our case. Second, theremay be lower and oscillating temperature. In ourfluid bed the temperature level was kept above800°C even with the alternative fuel. Therefore therewas no reason to find any adverse effect to theemission of chlorine compounds and their speciation.In particular, it has been proved by determination oflow toxicity equivalent I-TEQ of PCDD/F in flue gasfor all our fuel combinations. A hypotheses that theslight variation of dioxin production can becorrelated with the copper content in fuel seems to beplausible, but it should be checked using moreextended experimental material. With lower level ofalkali metals in alternative fuel, the incrustation ofash on walls is not on issue; this may be problemwhen combusting straw or reed.The large-scale experiments proved thefeasibility of addition of large percentage, up to50 %, of alternative organic fuels, namely wood andbark chips, paper mill sewage sludge, and choppedpaper, textile and plastic particles, to the fluid bedboiler as a substitute for lignite. From the viewpointof chlorine derived compounds in emissions, the cofiringof lignite with the alternative fuels underinvestigation is a good choice.ACKNOWLEDGMENTThe authors wishes to express their thanks to the GrantAgency of Czech Republic for financial support under thegrant 101/03/1402.REFERENCESBluemler, P., 2005. Dioxin: Seveso, Vietnam andeveryday exposure. [http://www.mpipmainz.mpg.de/~bluemler/extra/teaching/dioxine.pdf],7.8.2005DOE: 2001, Biomass Policy.[http://www.eren.doe.gov/power/pdfs/bio_co_fire.pdf ]15.3.01EC:1996, Council of the European Union Directive96/082/EEC of 9 December 1996 (commonly referred toas the Seveso II Directive)7

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