1commonbiogastreatmentscheme

    以1000t/d焚燒廠為例分析，滲瀝液處理系統(tǒng)產(chǎn)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(zhì)。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(chǎn)生的沼氣經(jīng)沼氣燃燒器送入焚燒爐燃燒，整套系統(tǒng)的熱量增加，實現(xiàn)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(nèi)燃燒，增加了鍋爐的蒸發(fā)量，相應地也增加了汽輪發(fā)電機組的發(fā)電量。發(fā)電廠熱效率按21.5%計算，沼氣低位熱值約為20MJ/m3，每小時發(fā)電量為448kWh。沼氣上網(wǎng)發(fā)電量每小時約為403kWh，年上網(wǎng)發(fā)電量為3.22x106kWh。垃圾焚燒發(fā)電廠上網(wǎng)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(jīng)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(fā)生自燃，因此將其位置設置在爐排燃燒段側(cè)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(zhì)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(fā)電回噴系統(tǒng)示意圖

    Schematicdiagramofbiogaspowergenerationinjectionsystem

    沼氣在使用時低壓向爐內(nèi)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(jié)露而發(fā)生腐蝕，為防止此問題出現(xiàn)，在沼氣停止供應時通過壓縮空氣將管道內(nèi)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(jīng)焚燒會釋放自身熱量。熱效率、年發(fā)電量等與沼氣燃燒器基本相同，30a特許經(jīng)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(jīng)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(chǎn)生的沼氣等有害氣體排至垃圾坑，垃圾坑內(nèi)保持負壓，經(jīng)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(jīng)焚燒會釋放自身熱量。熱效率、年發(fā)電量等與沼氣回爐焚燒相同。30a特許經(jīng)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(chǎn)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(shù)約為9.5%，當甲烷在空氣中體積分數(shù)達到9.5%時，會發(fā)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(huán)境，致使垃圾產(chǎn)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(fā)電燃氣內(nèi)燃機發(fā)電機組（方案4）

    1.4gasenginegeneratorsetforbiogaspowergeneration(scheme4)

    燃氣內(nèi)燃機適用于沼氣產(chǎn)量較小的場所，以沼氣為燃料，帶動內(nèi)燃機和發(fā)電機發(fā)電。  Gasinternalcombustionengineissuitableforplaceswithsmallbiogasproduction.Biogasisusedasfueltodriveinternalcombustionengineandgeneratortogenerateelectricity.

    根據(jù)國內(nèi)外機組經(jīng)驗，燃氣內(nèi)燃機發(fā)電機組熱效率按33%計算，則每小時發(fā)電量為20x1000x375-3600x33%=687KWH。沼氣上網(wǎng)發(fā)電量每小時約為583kWh，年上網(wǎng)發(fā)電量為4.66x106kWh。每年可以增加收入302萬元，30a特許經(jīng)營期共計為9060萬元。

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