1commonbiogastreatmentscheme

    以1000t/d焚燒廠為例分析，滲瀝液處理系統產生的沼氣量約9000m3/d，沼氣送入除濕裝置，除去沼氣中的水分，之后進入過濾裝置，過濾出沼氣中的顆粒雜質。清潔沼氣通過壓縮機送入沼氣儲罐，沼氣低位熱值約取20MJ/m3。

 Takinga1000t/Dincinerationplantasanexample,theamountofbiogasproducedbytheleachatetreatmentsystemisabout9000m3/D.thebiogasissenttothedehumidificationdevicetoremovethemoistureinthebiogas,andthentothefiltrationdevicetofilterouttheparticulateimpuritiesinthebiogas.Thecleanbiogasissenttothebiogasstoragetankthroughthecompressor,andthelowcalorificvalueofbiogasisabout20MJ/m3.

    1.1設置沼氣燃燒器，回焚燒爐焚燒（方案1）

    1.1setbiogasburnerandreturntoincineratorforincineration(scheme1)

    該方案是將滲瀝液厭氧處理過程中產生的沼氣經沼氣燃燒器送入焚燒爐燃燒，整套系統的熱量增加，實現了對資源的回收利用。沼氣燃燒器位置一般設在輔助燃燒器附近。   Inthisscheme,thebiogasproducedintheprocessofanaerobictreatmentofleachateissenttotheincineratorforcombustionthroughthebiogasburner,theheatofthewholesystemisincreased,andtheresourcerecyclingisrealized.Biogasburnersareusuallylocatednearauxiliaryburners.

    沼氣噴入焚燒爐內燃燒，增加了鍋爐的蒸發量，相應地也增加了汽輪發電機組的發電量。發電廠熱效率按21.5%計算，沼氣低位熱值約為20MJ/m3，每小時發電量為448kWh。沼氣上網發電量每小時約為403kWh，年上網發電量為3.22x106kWh。垃圾焚燒發電廠上網電價一般為0.65元，每年可以增加收入約210萬元，則30a特許經營期共討約6300萬元。    Biogasisinjectedintotheincineratorforcombustion,whichincreasestheevaporationcapacityoftheboilerandthepowergenerationcapacityofthesteamturbinegeneratorunit.Thethermalefficiencyofthepowerplantis21.5%,thelowcalorificvalueofbiogasisabout20MJ/m3,andthepowergenerationperhouris448kwh.Thebiogaspowergenerationisabout403kwhperhour,andtheannualpowergenerationis3.22x106kwh.Theongridelectricitypriceofwasteincinerationpowerplantisgenerally0.65yuan,whichcanincreasetheincomeby2.1millionyuanperyear,sothetotalamountoftheconcessionperiodof30yearsisabout63millionyuan.

    1.2設置沼氣回噴入爐焚燒裝置，但無點火設備（方案2）

    1.2installationofbiogasreinjectionincineratorwithoutignitionequipment(scheme2)

    該方案設置沼氣回噴入爐焚燒裝置，但不設置點火設備。其工藝流程見圖1。回噴槍將沼氣供向有垃圾火焰的部分，并且通過二次燃燒空氣的供給，在氧氣濃度升高的情況下即使未燃盡的垃圾也可以發生自燃，因此將其位置設置在爐排燃燒段側壁但比垃圾層高的位置。因此處溫度較高，約1000°C,故回噴槍材質選用不銹鋼或合金鋼。沼氣燃燒所需的燃燒空氣是焚燒垃圾所用燃燒空氣的一部分。

 Inthisscheme,biogasisinjectedbackintotheincineratorwithoutignitionequipment.TheprocessflowisshowninFigure1.Whentheoxygenconcentrationincreases,eventheunburnedgarbagecanspontaneouslyignite.Therefore,thepositionofthelanceissetonthesidewallofthegratecombustionsectionbuthigherthanthegarbagelayer.Therefore,thetemperatureishigheratabout1000°C,sostainlesssteeloralloysteelisusedasthematerialofthespraygun.Thecombustionairrequiredforbiogascombustionisapartofthecombustionairusedforincinerationofgarbage.

    沼氣發電回噴系統示意圖

    Schematicdiagramofbiogaspowergenerationinjectionsystem

    沼氣在使用時低壓向爐內供應沼氣，在不使用時由冷卻空氣冷卻，以防止沼氣長管熱燒傷。另外，沼氣長管通過沼氣后，可能會因沼氣中的H2S結露而發生腐蝕，為防止此問題出現，在沼氣停止供應時通過壓縮空氣將管道內殘留的沼氣吹掃干凈。

    Biogasissuppliedtothefurnaceatlowpressurewhenitisinuse,andcooledbycoolingairwhenitisnotinuse,soastopreventthelongbiogaspipefromthermalburn.Inaddition,thelongbiogaspipemaybecorrodedduetothecondensationofH2Sinthebiogasafterpassingthroughthebiogas.Inordertopreventthisproblem,theresidualbiogasinthepipeisblowncleanbycompressedairwhenthebiogassupplyisstopped.

    另外，需設1套火炬沼氣燃燒處理裝置，當焚燒爐停爐時，可通過管道輸送至火炬高空燃燒處置。

    Inaddition,asetoftorchbiogascombustiontreatmentdeviceisrequired,whichcanbetransportedtothetorchforhigh-altitudecombustiontreatmentthroughpipelinewhentheincineratorisshutdown.

    在運行過程中，沼氣被送入焚燒爐后，經焚燒會釋放自身熱量。熱效率、年發電量等與沼氣燃燒器基本相同，30a特許經營期共計約6300萬元。

    Intheprocessofoperation,afterbiogasissenttotheincinerator,itwillreleaseitsownheatafterincineration.Thethermalefficiencyandannualpowergenerationarebasicallythesameasthoseofbiogasburners.Thetotalfranchiseperiodof30yearsisabout63millionyuan.

    1.3將沼氣排放至垃圾坑，經風機抽回至焚燒爐焚燒（方案3）

    1.3thebiogaswillbedischargedtothegarbagepitandpumpedbacktotheincineratorforincinerationthroughthefan(scheme3)

    滲瀝液收集間設置通風裝置，將滲瀝液處理過程中產生的沼氣等有害氣體排至垃圾坑，垃圾坑內保持負壓，經一次風機抽取后通過爐排下部送入焚燒爐燃燒。理論上，被送入焚燒爐的沼氣被送入焚燒爐后，經焚燒會釋放自身熱量。熱效率、年發電量等與沼氣回爐焚燒相同。30a特許經營期共計約6300萬元。   Aventilationdeviceissetintheleachatecollectionroomtodischargethebiogasandotherharmfulgasesgeneratedintheleachatetreatmentprocesstothegarbagepit.Thenegativepressureismaintainedinthegarbagepit.Afterbeingextractedbytheprimaryfan,itissenttotheincineratorforcombustionthroughthelowerpartofthegrate.Intheory,thebiogassenttotheincineratorwillreleaseitsownheatafterbeingburned.Thethermalefficiencyandannualpowergenerationarethesameasthoseofbiogasincineration.The30-yearfranchiseperiodisabout63millionyuan.

    垃圾坑中垃圾本身也會產生沼氣，甲烷與氧氣完全反應：CH4+2O2=C02+2H20,CH4與02反應體積比是1:2，空氣中氧氣含量為21%，即1LCH4燃燒需空氣9.5L。因此甲烷占混合氣體的體積分數約為9.5%，當甲烷在空氣中體積分數達到9.5%時，會發生強烈爆炸。而生活垃圾中有機物含量較高，集中堆放容易形成厭氧環境，致使垃圾產生的沼氣不斷積累與釋放，若CH4在空氣中的含量達到其爆炸極限有氧條件下，CH4爆炸極限為5%?15%或遇到明火則極易引起爆炸。    Thegarbageitselfinthegarbagepitwillalsoproducebiogas.Methaneandoxygenwillcompletelyreact:CH4+2O2=C02+2h20,thevolumeratioofCH4and02is1:2,andtheoxygencontentintheairis21%,thatis,9.5lairisrequiredfor1lch4combustion.Therefore,thevolumefractionofmethaneinthemixedgasisabout9.5%.Whenthevolumefractionofmethaneintheairreaches9.5%,astrongexplosionwilloccur.However,duetothehighcontentoforganicmatterindomesticwaste,itiseasytoformananaerobicenvironmentforcentralizedstacking,resultinginthecontinuousaccumulationandreleaseofbiogasgeneratedbywaste.IfthecontentofCH4intheairreachesitsexplosionlimit,theexplosionlimitofCH4is5%-15%underaerobicconditions,oritisveryeasytocauseexplosionwhenencounteringopenfire.

    1.4配套沼氣發電燃氣內燃機發電機組（方案4）

    1.4gasenginegeneratorsetforbiogaspowergeneration(scheme4)

    燃氣內燃機適用于沼氣產量較小的場所，以沼氣為燃料，帶動內燃機和發電機發電。  Gasinternalcombustionengineissuitableforplaceswithsmallbiogasproduction.Biogasisusedasfueltodriveinternalcombustionengineandgeneratortogenerateelectricity.

    根據國內外機組經驗，燃氣內燃機發電機組熱效率按33%計算，則每小時發電量為20x1000x375-3600x33%=687KWH。沼氣上網發電量每小時約為583kWh，年上網發電量為4.66x106kWh。每年可以增加收入302萬元，30a特許經營期共計為9060萬元。

    Accordingtotheexperienceofdomesticandforeignunits,ifthethermalefficiencyofgas-firedinternalcombustionenginegeneratorsetiscalculatedas33%,thehourlypowergenerationis20x1000x375-3600x33%=687kwh.Biogaspowergenerationisabout583kwhperhourand4.66x106kwhperyear.Theannualincomecanbeincreasedby3.02millionyuan,withatotalof90.6millionyuanin30-yearfranchiseperiod.