Soot Deposits and Fires in Exhaust Gas Boiler - Martin's Marine ...
Soot Deposits and Fires in Exhaust Gas Boiler - Martin's Marine ...
Soot Deposits and Fires in Exhaust Gas Boiler - Martin's Marine ...
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OC Temperature T<strong>Exhaust</strong> gas boilerPreheaterEvaporatorSuperheater<strong>Exhaust</strong> gasSaturatedsteam forheat<strong>in</strong>gservicesOil-firedboiler withsteam drumHeatexc.250SuperheatedsteamSaturatedsteam300200150100<strong>Exhaust</strong> gasSteam/water 7 bar absP<strong>in</strong>chpo<strong>in</strong>tTurbogenerator(steam turb<strong>in</strong>e)CondenserCondensate pumpsFeedwaterpumpAtmosphericsurpluscondenserHot well5000% 20% 40% 60% 80% 100%FeedwaterHeat transmissionQSuperheater Evaporator PreheaterFig. 8: Special exhaust gas boiler system with turbo generator forelectricity productionS<strong>in</strong>gle pressure steam system with preheater, evaporator<strong>and</strong> superheater sectionsFig. 9: T/Q diagram for an exhaust gas boilercommon steam drum for the oil-firedboiler <strong>and</strong> the exhaust gas boiler.Separate steam drums may also beused, so that one boiler can be run ifthe other should malfunction.Because of its simplicity <strong>and</strong> low capitalcost, the above system is widely used<strong>and</strong> is often entirely adequate when thesteam production is viewed as a meansof meet<strong>in</strong>g the steam dem<strong>and</strong> for heat<strong>in</strong>gservices on the ship.The loss of water from the exhaust gasboiler is <strong>in</strong> the magnitude of about 1%of the steam production.Special exhaust gas boiler systemwith turbogeneratorWhen a turbogenerator, i.e. a steamturb<strong>in</strong>e driven electrical generator, is <strong>in</strong>stalled(utilis<strong>in</strong>g the steam available afterdeduction of steam for heat<strong>in</strong>g services),the exhaust gas boiler systemwill be more advanced.An example of such a system is shown<strong>in</strong> Fig. 8. The boiler is, apart from theevaporator, also fitted with a preheater<strong>and</strong> superheater. In this system too,the steam drum of the oil-fired boiler isnormally used as a common steam drum.The <strong>in</strong>fluence of a boiler’sp<strong>in</strong>ch po<strong>in</strong>tA boiler’s p<strong>in</strong>ch po<strong>in</strong>t is a parameter thatcan tell us a lot about the boiler’s design<strong>and</strong> potential behaviour <strong>in</strong> operation. Itwill therefore be def<strong>in</strong>ed below, <strong>and</strong> its<strong>in</strong>fluence on some important boiler parameterswill be discussed <strong>in</strong> this section.A boiler’s T/Q diagram <strong>and</strong> def<strong>in</strong>itionof p<strong>in</strong>ch po<strong>in</strong>tA temperature/heat transfer diagram, aso-called T/Q diagram, illustrates thecharacteristic temperature coursethrough the exhaust gas boiler. As anexample valid for the special exhaustgas boiler system shown <strong>in</strong> Fig. 8, a T/Qdiagram is shown <strong>in</strong> Fig. 9.The utilisation efficiency of an exhaustgas boiler is characterised by its p<strong>in</strong>chpo<strong>in</strong>t. The p<strong>in</strong>ch po<strong>in</strong>t is the lowesttemperature difference between the exhaustgas <strong>and</strong> the saturated steam, i.e.the temperature difference between theexhaust gas leav<strong>in</strong>g the evaporatorsection <strong>and</strong> the saturated steam, seethe T/Q diagram <strong>in</strong> Fig. 9.Normally, the steam pressure will be above7 bar abs. (6 barg) <strong>and</strong> often equal to 88This document, <strong>and</strong> more, is available for download at Mart<strong>in</strong>'s Mar<strong>in</strong>e Eng<strong>in</strong>eer<strong>in</strong>g Page - www.dieselduck.net