1commonbiogastreatmentscheme

    以1000t/d焚烧厂为例分析，渗沥液处理系统产生的沼气量约9000m3/d，沼气送入除湿装置，除去沼气中的水分，之后进入过滤装置，过滤出沼气中的颗粒杂质。清洁沼气通过压缩机送入沼气储罐，沼气低位热值约取20MJ/m3。

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

    1.1设置沼气燃烧器，回焚烧炉焚烧（方案1）

    1.1setbiogasburnerandreturntoincineratorforincineration(scheme1)

    该方案是将渗沥液厌氧处理过程中产生的沼气经沼气燃烧器送入焚烧炉燃烧，整套系统的热量增加，实现了对资源的回收利用。沼气燃烧器位置一般设在辅助燃烧器附近。   Inthisscheme,thebiogasproducedintheprocessofanaerobictreatmentofleachateissenttotheincineratorforcombustionthroughthebiogasburner,theheatofthewholesystemisincreased,andtheresourcerecyclingisrealized.Biogasburnersareusuallylocatednearauxiliaryburners.

    沼气喷入焚烧炉内燃烧，增加了锅炉的蒸发量，相应地也增加了汽轮发电机组的发电量。发电厂热效率按21.5%计算，沼气低位热值约为20MJ/m3，每小时发电量为448kWh。沼气上网发电量每小时约为403kWh，年上网发电量为3.22x106kWh。垃圾焚烧发电厂上网电价一般为0.65元，每年可以增加收入约210万元，则30a特许经营期共讨约6300万元。    Biogasisinjectedintotheincineratorforcombustion,whichincreasestheevaporationcapacityoftheboilerandthepowergenerationcapacityofthesteamturbinegeneratorunit.Thethermalefficiencyofthepowerplantis21.5%,thelowcalorificvalueofbiogasisabout20MJ/m3,andthepowergenerationperhouris448kwh.Thebiogaspowergenerationisabout403kwhperhour,andtheannualpowergenerationis3.22x106kwh.Theongridelectricitypriceofwasteincinerationpowerplantisgenerally0.65yuan,whichcanincreasetheincomeby2.1millionyuanperyear,sothetotalamountoftheconcessionperiodof30yearsisabout63millionyuan.

    1.2设置沼气回喷入炉焚烧装置，但无点火设备（方案2）

    1.2installationofbiogasreinjectionincineratorwithoutignitionequipment(scheme2)

    该方案设置沼气回喷入炉焚烧装置，但不设置点火设备。其工艺流程见图1。回喷枪将沼气供向有垃圾火焰的部分，并且通过二次燃烧空气的供给，在氧气浓度升高的情况下即使未燃尽的垃圾也可以发生自燃，因此将其位置设置在炉排燃烧段侧壁但比垃圾层高的位置。因此处温度较高，约1000°C,故回喷枪材质选用不锈钢或合金钢。沼气燃烧所需的燃烧空气是焚烧垃圾所用燃烧空气的一部分。

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

    沼气发电回喷系统示意图

    Schematicdiagramofbiogaspowergenerationinjectionsystem

    沼气在使用时低压向炉内供应沼气，在不使用时由冷却空气冷却，以防止沼气长管热烧伤。另外，沼气长管通过沼气后，可能会因沼气中的H2S结露而发生腐蚀，为防止此问题出现，在沼气停止供应时通过压缩空气将管道内残留的沼气吹扫干净。

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

    另外，需设1套火炬沼气燃烧处理装置，当焚烧炉停炉时，可通过管道输送至火炬高空燃烧处置。

    Inaddition,asetoftorchbiogascombustiontreatmentdeviceisrequired,whichcanbetransportedtothetorchforhigh-altitudecombustiontreatmentthroughpipelinewhentheincineratorisshutdown.

    在运行过程中，沼气被送入焚烧炉后，经焚烧会释放自身热量。热效率、年发电量等与沼气燃烧器基本相同，30a特许经营期共计约6300万元。

    Intheprocessofoperation,afterbiogasissenttotheincinerator,itwillreleaseitsownheatafterincineration.Thethermalefficiencyandannualpowergenerationarebasicallythesameasthoseofbiogasburners.Thetotalfranchiseperiodof30yearsisabout63millionyuan.

    1.3将沼气排放至垃圾坑，经风机抽回至焚烧炉焚烧（方案3）

    1.3thebiogaswillbedischargedtothegarbagepitandpumpedbacktotheincineratorforincinerationthroughthefan(scheme3)

    渗沥液收集间设置通风装置，将渗沥液处理过程中产生的沼气等有害气体排至垃圾坑，垃圾坑内保持负压，经一次风机抽取后通过炉排下部送入焚烧炉燃烧。理论上，被送入焚烧炉的沼气被送入焚烧炉后，经焚烧会释放自身热量。热效率、年发电量等与沼气回炉焚烧相同。30a特许经营期共计约6300万元。   Aventilationdeviceissetintheleachatecollectionroomtodischargethebiogasandotherharmfulgasesgeneratedintheleachatetreatmentprocesstothegarbagepit.Thenegativepressureismaintainedinthegarbagepit.Afterbeingextractedbytheprimaryfan,itissenttotheincineratorforcombustionthroughthelowerpartofthegrate.Intheory,thebiogassenttotheincineratorwillreleaseitsownheatafterbeingburned.Thethermalefficiencyandannualpowergenerationarethesameasthoseofbiogasincineration.The30-yearfranchiseperiodisabout63millionyuan.

    垃圾坑中垃圾本身也会产生沼气，甲烷与氧气完全反应：CH4+2O2=C02+2H20,CH4与02反应体积比是1:2，空气中氧气含量为21%，即1LCH4燃烧需空气9.5L。因此甲烷占混合气体的体积分数约为9.5%，当甲烷在空气中体积分数达到9.5%时，会发生强烈爆炸。而生活垃圾中有机物含量较高，集中堆放容易形成厌氧环境，致使垃圾产生的沼气不断积累与释放，若CH4在空气中的含量达到其爆炸极限有氧条件下，CH4爆炸极限为5%〜15%或遇到明火则极易引起爆炸。    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配套沼气发电燃气内燃机发电机组（方案4）

    1.4gasenginegeneratorsetforbiogaspowergeneration(scheme4)

    燃气内燃机适用于沼气产量较小的场所，以沼气为燃料，带动内燃机和发电机发电。  Gasinternalcombustionengineissuitableforplaceswithsmallbiogasproduction.Biogasisusedasfueltodriveinternalcombustionengineandgeneratortogenerateelectricity.

    根据国内外机组经验，燃气内燃机发电机组热效率按33%计算，则每小时发电量为20x1000x375-3600x33%=687KWH。沼气上网发电量每小时约为583kWh，年上网发电量为4.66x106kWh。每年可以增加收入302万元，30a特许经营期共计为9060万元。

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