SIST EN 12952-9:2003

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Vodocevni kotli in pomožne napeljave - 9. del: Zahteve za kotlovske kurilne naprave na premogov prahWasserrohrkessel und Anlagenkomponenten - Teil 9: Anforderungen an Staubfeuerungsanlagen für den KesselChaudieres a tubes d'eau et installations auxiliaires - Partie 9: Exigences pour les équipements de chauffe pour combustibles pulverisés de la chaudiereWater-tube boilers and auxiliary installations - Part 9: Requirements for firing systems for pulverized solid fuels for the boiler27.060.30Grelniki vode in prenosniki toploteBoilers and heat exchangersICS:Ta slovenski standard je istoveten z:EN 12952-9:2002SIST EN 12952-9:2003en01-december-2003SIST EN 12952-9:2003SLOVENSKI
STANDARD



SIST EN 12952-9:2003



EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 12952-9December 2002ICS 27.040English versionWater-tube boilers and auxiliary installations - Part 9:Requirements for firing systems for pulverized solid fuels for theboilerChaudières à tubes d'eau et installations auxiliaires - Partie9: Exigences pour les équipements de chauffe pourcombustibles pulverisés de la chaudièreWasserrohrkessel und Anlagenkomponenten - Teil 9:Anforderungen an Staubfeuerungsanlagen für den KesselThis European Standard was approved by CEN on 4 November 2002.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2002 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 12952-9:2002 ESIST EN 12952-9:2003



EN 12952-9:2002 (E)2ContentspageForeword.31Scope.41.1Firing systems.41.2Fuels.41.3Operation.41.4Boundary of pulverizing system.42Normative references.43Terms and definitions.54Fuel bunkers with conveying plant.84.1General.84.2Conveying plant.84.3Coal bunkers.85Pulverizing system and pulverized fuel system.95.1General.95.2Coal feeders.95.3Mills.95.4Pulverized fuel bins.105.5Pulverized fuel supply pipes and shutoff devices.106Explosion prevention measures for pulverizing systems and pulverized fuel systems.116.1General.116.2Plants operated without inert gas protection.126.3Plants operated with inert gas protection.127Equipment for air supply and flue gas discharge.137.1Air supply.137.2Air/fuel ratio.137.3Flue gas discharge.148Firing system.148.1General.148.2Burners for pulverized fuel.148.3Flue gas recirculation.148.4Modification of the firing system setting.158.5Monitoring and control.158.6Electrical equipment.158.7Safety precautions.169Ash extraction plant.1910Operation and maintenance.1910.1General.1910.2Operating manual and instructions.19Annex A (informative)
Operational requirements for permanently supervised firing system forpulverized fuel.21Annex ZA (informative)
Clauses of this European Standard addressing essential requirements orother provisions of the Pressure Equipment Directive.24Bibliography.25SIST EN 12952-9:2003



EN 12952-9:2002 (E)3ForewordThis document (EN 12952-9:2002) has been prepared by Technical Committee CEN/TC 269 “Shell and water-tubeboilers”, the secretariat of which is held by DIN.This European Standard shall be given the status of a national standard, either by publication of an identical text orby endorsement, at the latest by June 2003, and conflicting national standards shall be withdrawn at the latest byJune 2003.This document has been prepared under a mandate given to CEN by the European Commission and the EuropeanFree Trade Association, and supports essential requirements of EU Directive 97/23/EC [1].For relationship with EU Directive 97/23EC, see informative Annex ZA, which is an integral part of this document.The European Standard EN 12952 concerning water-tube boilers and auxiliary installations consists of the followingparts:¾ Part 1:General¾ Part 2:Materials for pressure parts of boilers and accessories¾ Part 3:Design and calculation for pressure parts¾ Part 4:In-service boiler life expectancy calculations¾ Part 5:Workmanship and construction of pressure parts of the boiler¾ Part 6:Inspection during construction; documentation and marking of pressure parts of the boiler¾ Part 7:Requirements for equipment for the boiler¾ Part 8:Requirements for firing systems for liquid and gaseous fuels for the boiler¾ Part 9:Requirements for firing systems for pulverized solid fuels for the boiler¾ Part 10:Requirements for safeguards against excessive pressure¾ Part 11:Requirements for limiting devices of the boiler and accessories¾ Part 12:Requirements for feedwater and boiler water quality¾ Part 13:Requirements for flue gas cleaning systems¾ Part 14:Requirements for flue gas DENOX-systems¾ Part 15:Acceptance tests¾ Part 16:Requirements for grate and fluidized bed-firing systems for solid fuels for the boilerCR 12952-17, Water-tube boilers and auxiliary installations — Part 17: Guideline for the involvement of an inspec-tion body independent of the manufacturer.Although these parts may be obtained separately, it shall be recognized that the parts are interdependent. As such,the design and manufacture of water-tube boilers requires the application of more than one part in order for the re-quirements of the standard to be satisfactorily fulfilled.NOTEParts 4 and 15 are not applicable during the design, construction and installation stages.Annex A of this European Standard is informative.According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following coun-tries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland,France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Swe-den, Switzerland and the United Kingdom.SIST EN 12952-9:2003



EN 12952-9:2002 (E)41 Scope1.1 Firing systemsThis European Standard applies to pulverized fuel firing systems of steam boilers and hot water generators andcommences at the filling equipment for the boiler bunkers or for the pulverized fuel storage system and ends at theash extraction plant. For multifuel firing systems using separate or combined burners, these requirements apply to thepulverized fuel firing part involved. For other fuels or firing systems used in combination, other requirements apply e.g.EN 12952-8.1.2 FuelsThese requirements cover the use of pulverized fuels originating from coal ranging from low to high volatile mattercontent. This includes e.g. coke, anthracite, bituminous coal or hard coal, lignite or brown coal, petrol coke and oilshale.1.3 OperationRequirements for operational equipment apply for steam boilers and hot water generators with permanent supervisionby properly trained persons.As firing systems using pulverized fuel may be designed either as direct-firing or as indirect-firing systems, operationalrequirements have to be differentiated. Annex A summarizes the operational requirements for firing systems includingthe pulverizing system.1.4 Boundary of pulverizing systemA pulverizing system is bounded by:¾ the outlet of the fuel bunkers feeding the mill;¾ the outlet of the burners fed from that mill;¾ the points at which the hot air or flue gas and tempering air or flue gas leave their main supply ducts includingthe primary air fan if associated individually with the mill.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. Thesenormative references are cited at the appropriate places in the text, and the publications are listed hereafter. Fordated references, subsequent amendments to or revisions of any of these publications apply to this EuropeanStandard only when incorporated in it by amendment or revision. For undated references the latest edition of thepublication referred to applies (including amendments).EN 1127-1, Explosive atmospheres — Explosion prevention and protection — Part 1: Basic concepts and method-ology.EN 12952-8, Water-tube boilers and auxiliary installations — Part 8: Requirements for firing systems for liquid andgaseous fuels for the boiler.prEN 50156-1, Electrical equipment for furnaces and ancillary equipment — Part 1: Requirements for applicationdesign and installation.SIST EN 12952-9:2003



EN 12952-9:2002 (E)53 Terms and definitionsFor the purposes of this European Standard, the terms and definitions given in EN 12952-8 and the following apply.3.1back-up firing systemseparate firing system to maintain safe ignition and stable combustion of the pulverized fuel3.2burner groupburners operated in forced unison and controlled jointly and the burners supplied by the same mill or the same pul-verized fuel feeder3.3burner management systemburner management system performs a predetermined sequence of actions and always operates in conjunctionwith a flame monitor. It reacts to signals from control and safety devices, gives control commands, controls thestart-up sequence, supervises the burner operation, and causes controlled shutdown and lock-out3.4carrier gastransport medium for pulverized fuel through mill, classifier, and pulverized fuel lines. It may consist of primary airand/or inert gas3.5clearingremoval of accumulation or settlement of pulverized fuel in the case of insufficient purging of the pulverizing system3.6coal bunkerbunker for the storage of raw coal for an individual mill3.7coal feederinstallation for the extraction of coal from the coal bunker and the controlled feeding of coal into the mill3.8combustion airtotal air supplied to the firing system for combustion3.9conveying plant (Coal handling plant)installation for conveying and distributing raw coal to the individual coal bunkers3.10direct-firing systemsystem where the fuel is ground and dried in the mill and then is fed directly to the burners3.11explosionunintentional instantaneous combustion phenomenon occurring in a confined space with considerable pressurebuild-upNOTEA weak explosion is called puffing.3.12explosion pressure resistant designinstallations that are dimensioned so as to withstand the maximum explosion pressure without substaining perma-nent deformationSIST EN 12952-9:2003



EN 12952-9:2002 (E)63.13explosion pressure shock resistant designinstallations that are dimensioned so as to withstand the pressure surge occurring during an explosion withoutrupture although permanent deformation may occur3.14firing rate during start-upfiring rate of a burner or a burner group forming part of a pulverizing system of a direct-fired system during start-up3.15firing systemequipment for the combustion of fuels, including the installations for the storage in the boiler house, preparationand supply of fuels, the combustion air supply, the burner(s), the flue gas discharge, and all related control andmonitoring devicesNOTEA flue gas recirculation system can be installed as an integral part of the firing system.3.16firing system heat inputheat input into the combustion chamber, normally calculated as the mass flow of the fuel supplied multiplied by itsnet calorific value3.17flame monitordevice that detects the presence or absence of the flame and transmits a signal to the control deviceFor a pulverized fuel firing system the flame can be defined as:¾ an individual flame of a single burner,¾ the flame of a burner group for instance all burners connected to a pulverizing system,¾ the flame of all burners in one combustion chamber.3.18flame-resistant materialflame-resistant material that is combustible only when subjected to a continual supply of heat energy and extin-guishes upon removal of the ignition source3.19flue gas recirculationreturn of flue gas from downstream of the flame zone or from the flue gas exitNOTEThis can be achieved by pressure difference or the use of a separate fan or fans into the pulverizing system, the airregister of the burner, or directly into the combustion chamber.3.20implosionunintentional instantaneous negative pressure build-upNOTEThis can occur as a consequence of an explosion in a confined space, by rapid closing of dampers, or by rapid reduc-tion in temperature, e.g. flame out.3.21indirect-firing systemsystem where the fuel that has been ground and dried in the mill is intermediately stored in bins and the vapoursare separatedNOTEThe pulverized fuel is extracted from the bin and fed to the burners.SIST EN 12952-9:2003



EN 12952-9:2002 (E)73.22inertingdilution of the oxygen content of an air/fuel mixture by the addition of an inert gas or steam to a level where it is nolonger ignitable3.23lighting-up equipmentfacility to achieve safe ignition of pulverized fuel at the burner. It may also be used for the provision of heat to initi-ate the drying process during start-up of a mill in a direct-firing system3.24limitertransducer, which, on reaching a fixed value (e.g. pressure, temperature, flow, water level) is used to interrupt andlockout the energy supply and requires manual unlocking before restart3.25lockoutinterruption of the energy supply. Manual unlocking is required before restart3.26master fuel tripdevice for rapid automatic shutoff of all fuel supplies to the boiler area and power to the electrical igniters in theevent of danger3.27maximum heat input of the firing systemmaximum heat input including the reserves required for load control at which the firing system can be safely oper-ated including all reserves3.28millinstallation for grinding and drying the raw coal and for classifying and conveying the pulverized fuel3.29minimum heat input of the firing systemminimum heat input at which the firing system can be safely operated3.30monitorlimit transducer that senses the reaching of a fixed limit value and initiates an alarm and/or a cut out. The outputsignal is only cancelled if the cause of the alarm has been removed and the value has returned to within its fixedlimits3.31multi-fuel burnersburners in which more than one fuel is burned either simultaneously or alternately3.32multi-fuel firing systemfiring system where, in a common combustion chamber, more than one fuel can be burned simultaneously or alter-nately by separate or multi-fuel burners3.33primary airpart of the combustion air flow fed to the mill for the drying and conveying of pulverized fuel. This primary air maybe mixed with flue gas3.34pulverized fuel binbin (silo) for the intermediate storage of pulverized fuelSIST EN 12952-9:2003



EN 12952-9:2002 (E)83.35pulverized fuel burnerdevice for the introduction of fuel and air into a combustion chamber at required velocities, turbulence, and localfuel concentration in order to establish and maintain proper ignition and stable combustion of the fuel3.36pulverized fuel feederdevice for the controlled feeding of pulverized fuel from the pulverized fuel bin into the pulverized fuel supply linesto the burners or other equipment3.37pulverizing system heat inputfiring system heat input of a direct-fired system divided by the number of pulverizing systems in operation3.38purging of the flue gas passesflow of air through the combustion chamber, flue gas passes and associated ducts, which effectively removes anygaseous combustibles and replaces them with air3.39purging of the pulverizing systemremoval of any accumulation or settlement of pulverized fuel from inside the pulverizing system3.40safety timetime period during which the effectiveness of the safety device may be inhibited without a hazardous condition oc-curring4 Fuel bunkers with conveying plant4.1 General4.1.1The conveyance of raw coal, temporary storage in bunkers, and extraction shall be arranged such that theflow of the fuel is ensured as far as possible.4.1.2Coarse coal lumps, foreign matter, and tramp metal shall be removed to avoid damage or blockage of thepulverizing system.4.1.3Access to the coal handling plant area shall be limited to authorized staff (see annex A).4.1.4Dangerous areas of the coal handling plant shall be marked by warning signs.4.2 Conveying plant4.2.1Automatic facilities for the conveyance and distribution of coal into the bunkers shall only be started ifvisual and/or audible warning signals have been given beforehand. Precautions necessary for the protection ofpersonnel against injury by moving components shall be taken. Sufficient waiting time between warning signal andstart-up shall be provided (see A.4).4.2.2Several continuous conveyors arranged in series to form one conveying line shall be interlocked such thatthe normal operation of any conveyor is possible only if the downstream conveyors are in operation and the storagefacility is ready to accept the coal.4.3 Coal bunkers4.3.1The coal bunkers shall be built to achieve uniform discharge by the selection of proper shape and design inorder to ensure a continuous uniform flow of the coal and to avoid segregation.SIST EN 12952-9:2003



EN 12952-9:2002 (E)94.3.2To avoid ingress of hot air/gas into the bunker or the suction of leakage air into the pulverizing system, aminimum fuel level shall be maintained in the bunker, unless other suitable measures are taken.4.3.3The minimum filling level of coal bunkers shall be monitored and an alarm activated when the level fallsbelow the predetermed level.4.3.4The inner surface of the coal bunker roof shall be designed so as to avoid the accumulation of dust andgas in dead pockets.4.3.5Bunker charging openings shall be guarded to prevent personnel from falling in (see A.5).4.3.6Fuel bunkers shall be equipped with fire fighting or fire prevention equipment. Coal bunkers may be emp-tied by use of emergency chutes.5 Pulverizing system and pulverized fuel system5.1 General5.1.1The pulverizing system shall be readily accessible to enable cleaning operations to be carried out. Pres-surized systems shall be dust-tight and gas-tight.5.1.2All practicable steps should be taken to eliminate sites in the pulverizing system where pulverized fuel andraw coal may become lodged.5.1.3If there is a possibility of settlement of pulverized fuel on components that have become hot during opera-tion, facilities shall be provided for purging and clearing after shut-down.5.1.4The system shall include throughout indicators and annunciators which will provide the operator with ade-quate information about significant operating conditions, both normal and abnormal.5.1.5To avoid the build up of electrostatic charges, all components shall be earthed unless forced and faultlessearthing is inherent in the design.NOTEFurther information is given in CENELEC Report R 044-001 [2].5.2 Coal feeders5.2.1Coal feeders and chutes shall be designed to provide a uniform flow of coal into the mill.5.2.2Means shall be provided for monitoring the flow of coal. In the event of loss of flow an audible or visiblealarm shall be acturated.5.3 Mills5.3.1Mills shall be designed to withstand the mechanical and thermal loadings which occur during operation.Pulverising mills are machines within the meaning of Council Directive 98/37/EC and should be designed and con-structed to comply with specified essential safety requirements, in particular requirements to avoid risks from fire orexplosion. Equipment within coal pulverising mills and associated control devices may also fall within the scope ofEuropean Council Directive 94/9/EC on equipment and protective systems for use in potentially explosive atmos-pheres. Manufacturers of pulverised fuel systems shall follow the requirements of EN 1127-1, where applicable toensure that the risks from coal dust explosions are eliminated or properly controlled.5.3.2The temperature downstream of the mill or classifier shall be continuously measured. If the allowable oper-ating temperature is exceeded, this shall be annunciated by an optical and/or accoustic alarm. Suitable automaticdevices shall prevent the upper temperature limit from being exceeded.SIST EN 12952-9:2003



EN 12952-9:2002 (E)105.3.3The allowable operating temperature and the upper temperature limit depend on design, mode of operationand type of fuel. These temperatures shall be determined by the manufacturer upon agreement with the user of theplant.5.3.4A means for inerting the pulverizing system shall be provided unless the risk of explosions and firehazards are prevented by other means, which are also valid in the case of upset conditions. Appropriateprecautions shall be adopted under these circumstances.NOTEIf the pulverizing system cannot be made inert after an emergency shoutdown, there will be a risk of explosion dur-ing the shutdown period if the mill is disturbed, e.g. by opening of the mill, starting the primary air supply, or starting the millmotor. Suitable inerting mediums are steam or inert gases, e. g. flue gas with low oxygen content.5.3.5A fire-extinguishing system shall be provided.5.3.6To isolate the mill for repair purposes during boiler operation, appropriate shut-off devices shall be providedupstream and downstream of the mill.5.4 Pulverized fuel bins5.4.1Pulverized fuel shall only be stored in a dust-tight bin (silo). Charging and extraction devices shall be de-signed to prevent the formation of a direct pathway between the contents of the silo and the atmosphere duringcharging and extraction operations.5.4.2Pulverized fuel bins shall be readily accessible and shall be designed to aid discharge by the selection ofadequate shape and design. The design of the bins and their internals shall be such as to prevent any inadmissibledust deposits from occurring. Bins and accessories shall be designed to prevent the escape of pulverized fuel andinerting gas into the surrounding operating areas.5.4.3On completion of erection of the plant, a leakage test shall be performed by the manufacturer.5.4.4Access doors shall be secured against unintentional opening.5.4.5Pulverized fuel bins shall be protected against inadmissible heating from the outside. Negative pressureswhich can occur shall be taken into account in the design.5.4.6Pulverized fuel bins shall be equipped with a connection for protective equipment, e.g. for the introductionof inert gas or fire extinguishing foam.Pulverized fuel bins shall be automatically monitored for interior fire, e.g. by temperature or CO measurements, unlessthey are operated under inert conditions, or fire hazards are excluded by other means.5.4.7When a pulverized fuel bin is equipped with an additional discharge system, this system shall only be de-signed as a closed system.5.4.8The filling level of the pulverized fuel bin shall be monitored.5.4.9With regard to fuel feeding into the burners the requirements given in 5.2 shall be applied accordingly.5.4.10Shutoff devices shall be provided at the extraction points of pulverized fuel bins. The gaskets shall bemade of flame resistant material.5.5 Pulverized fuel supply pipes and shutoff devices5.5.1Pulverized fuel shall only be conveyed in closed pipes which shall be dust-tight if operated under internalpressure.5.5.2The transport velocities and the pulverized fuel concentrations in the pulverized fuel pipes on a running millshall be sufficient to minimize deposition of pulverized fuel in the pipes and to avoid unsteady pulverized fuel deliv-ery to the burner.SIST EN 12952-9:2003



EN 12952-9:2002 (E)11This shall also apply to installations where the pulverized fuel flow is directed into multiple pipes.5.5.3All piping system components shall be capable of being purged of pulverized fuel.5.5.4Pulverized fuel pipes shall be manufactured using appropriate materials so as to withstand mechanical andthermal stresses occuring during operation, including operation under particular conditions.NOTEThe design of industrial piping system is covered in EN 13480-3 [3].5.5.5Devices shall be installed to isolate idle pulverized fuel pipes or pulverizing systems from the furnace.If one device is used to isolate more than one pulveri
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