37–137THERMALPOWERPLANTSThermalPowerGenerationThisprocessinvolvesthegenerationofelectricityfromtheburningoffossilfuelinalargeindustrialfurnace.Inverysimpleterms,inacoal-firedstation(Figure1)thecoalispulverizedandblownintothefurnacewhereitburns,muchlikeagasflame,toheatwaterandgeneratesteam,whichmovesathighspeedtoaturbine.Theturbinespinsanddrivesarotorattachedtoamagnetinagenerator.Therotatingmagneticfieldsmovingacrosscoilsinthegeneratorproduceelectriccurrents.Thethermalmachinesusedtoconvertthestoredenergyinthefuelstothekineticenergyoftherotorarecomplexunits.Eachconsistsoftwoprincipalparts:boilersandturbines.Theyalsoincludeavarietyofauxiliaryequipmenttoprovidefuelandwatertotheunitandtoeliminatewastegasesandproductsofcombustion.Thebasicoperationsaremechanicalandhighlyautomated.Inacoal-firedpowerstation,whereboilersandturbinesarecombined,thereisautomaticcontrolofcoalpulverization,ofsuppliedwaterandfuel,ofcombustion,andofsuperheating.Theeliminationofashintheauxiliaryprocessesisalsoautomated.PlantsFiredbyFossilFuelMostconstruction,repair,andmaintenanceworkisdoneduringunitshutdownsorperiodsofextensiverehabilitation.Thiscouldinvolveworkingononeofthefollowingsystemcomponents:•steamdrum•primarysteampiping•boilerfeedwater•superheater•reheater•economizer•downcomers•feederandrisertubesThesourcesofenergycreatedbynormalboileroperationarenotusuallypresentduringmajorreconstructionwork.However,unitsadjacenttotheshutdownunitareusuallyrunning,whichcancauseotherhazardssuchasheatandnoise.CommonHazardsofShutdownandRehabilitationWork1)ConventionalConstructionHazards•falls,eitherpeoplefallingorthingsfallingonpeople•electricalcontact–seeproximityrequirementstoworkaroundoverheadpowerlines•workingonornearliveequipment–workerswhoareaskedtoworkonornearenergizedequipment(regardlessoftheenergysource)mustcomplywithplantrequirementstobeappliedinallworksituationswheresystemsaretobedeenergizedandlockedoutbydevicessuchasswitchesorvalves•riggingandhoistinghazards•site-specifichazards—tobeidentifiedbytheplantrepresentative.2)IndustrialHygieneHazardsChemicalHazardsBeforeworkbegins,crewsshouldreceivetraininginthehazardsexistingintheworkareaandobtainandreviewtheMaterialSafetyDataSheets(MSDSs)foranyhazardousmaterialstowhichtheymaybeexposed.Theseshouldbereadilyavailablefromthefacilityand,infact,shouldbeobtainedbycontractorsandsubcontractorsatthetimeofbiddingtofacilitatejobplanning.Anyprotectiveequipmentusedshouldatleastequalthatwornbyplantpersonnelinthearea.SeeTable1.ReportedHealthProblemsSomeworkersinboilerroomsmaysufferfromdiseasesoftheupperrespiratorytractsuchasbronchitis,andfromconjunctivitiscausedbyvanadiumcompounds(dustgivenoffbyoilcombustion)andSO2.THERMALPOWERPLANTS•waterwalls•boilerhangerrods•muddrum•boilercasing•condensatesystem•electrostaticprecipitators•sulphurdioxidescrubbers•stacks.Figure1–Thermal(Coal-Fired)GeneratingStation37–2Fluecleanersandcinderremoversmay,aftersomeyears,sufferfromchronicbronchitisandrhinopharyngitisaswellaspneumosclerosiscausedbycinderdustandsulphurdioxideandtrioxide.Theresiduesofoilcombustionaremoreharmfulthanthedustgivenoffafterthecombustionofotherfuels.Dermatitiscandevelopfromashescontactingdampskin.Eczemamayresultfromthecombinedactionofcompoundsofnickel,vanadium,andsulphuricacidpresentintheresidues.3)OtherHealthHazardsForinformationonotherhealthhazards,refertothechaptersonWHMISandBasicOccupationalHealthinthismanual.Onecontroversialtopicisthepotentialhealthhazardofbeinginthevicinityofhighelectromagneticfieldsinthermalgeneratingplants.Thisconcernshouldbemonitoredforfutureinformation.THERMALPOWERPLANTSSubstanceCharacteristicsandDominantHazardAsbestos–Designatedsubstanceunderconstructionregulations–Diseasesincludeasbestosisandcancer.Seechapteronasbestosinthismanual.Lead–Designatedsubstanceunderindustrialregulations–CancausekidneyandbraindamageFlyash–Coalashcontainsoxidesofsilica,aluminum,andiron,withtracesofmanganese,lime,sodium,andunburntfuel(carbon).Alsoidentifiedaretraceelementssuchasarsenicandselenium–Oilashcancontainpentoxide,othervanadiumoxides,andsolublenickelcompounds–Respiratorytractirritation,dermatitis,andpossibleeczemawithextendedskincontactSilica–Designatedsubstanceunderindustrialregulations–CancausesilicosisCarbonmonoxide(CO)–Clear,colourless,odourless,tastelesstoxicgas–CausesdrowsinessleadingtodeathSulphurdioxide(SO2)–Fromsulphurcontentinoil–Veryirritatingandcorrosivegas,sulphur-likeodour,formsanacidoncontactwithmoistureCoaldust–InfuelsupplyandtransportareasWeldingfumes–Hazardsvarydependingontypeofmetal,typeofwelding,andcoatings–Healtheffectscanincludemetalfumefeverandrespiratoryirritation.Table1–HazardousSubstances
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