廢漆包線熱解煙氣二噁英排放特性與減排機(jī)理

范春龍,錢立新,丁 龍,沈 濤,姚 銘,春鐵軍,韓藝嬌,龍紅明,3*

廢漆包線熱解煙氣二噁英排放特性與減排機(jī)理

范春龍1,錢立新1,丁 龍1,沈 濤2,姚 銘1,春鐵軍1,韓藝嬌2,龍紅明1,3*

(1.安徽工業(yè)大學(xué)冶金工程學(xué)院,安徽 馬鞍山 243002；2.銅陵市卓翔銅材科技有限公司,安徽 銅陵 244100；3.冶金減排與資源利用教育部重點(diǎn)實(shí)驗(yàn)室,安徽 馬鞍山 243002)

分析了工業(yè)現(xiàn)場(chǎng)2t/爐的間歇式熱解爐煙氣中二噁英的生成及排放特性,提出了基于“過程抑制+末端減排”的二噁英控制技術(shù).研究了在廢銅漆包線熱解過程添加抑制劑,并結(jié)合末端活性炭吸附對(duì)二噁英及其同系物排放的影響.結(jié)果表明,熱解爐煙氣中PCDD/Fs的排放濃度為54.32ng/Nm3,I-TEQ值為5.30ng I-TEQ/Nm3.PCDF的同系物主要為1234678-HpCDF和OCDF;PCDD的同系物主要為1234678-HpCDD和OCDD.應(yīng)用“過程抑制+末端減排”的技術(shù)后,復(fù)合抑制劑能夠減弱金屬銅及其化合物的催化活性,降低Cl2的濃度,抑制從頭合成反應(yīng),復(fù)合抑制劑分解過程形成的活性自由基會(huì)阻礙PCDD/Fs的形成或攻擊PCDD/Fs的分子鍵,抑制二噁英生成,結(jié)合末端活性炭的物理吸附,使熱解爐煙氣中二噁英的排放濃度降低至1.10ng/Nm3,I-TEQ值降低至0.08ng I-TEQ/Nm3,達(dá)到國家環(huán)保標(biāo)準(zhǔn).

廢銅漆包線；熱解；二噁英；復(fù)合抑制劑；活性炭；減排

廢銅漆包線在國內(nèi)每年的產(chǎn)生量超過200萬t,其作為典型的有色金屬二次資源,是高品質(zhì)銅的加工原料,但由于廢銅漆包線表面包裹一層有機(jī)涂層,直接高溫熔煉回收時(shí)存在煙氣污染大、環(huán)境風(fēng)險(xiǎn)不可控等問題[1].因此,廢銅漆包線在回收前必須將其表面的有機(jī)涂層脫除.目前主要的脫除方法有機(jī)械脫漆法、激光脫漆法、化學(xué)脫漆法和熱解法[2-4].機(jī)械脫漆法脫漆效率低,銅損耗率高[1].激光脫漆法設(shè)備價(jià)格昂貴,脫漆效率低,限制了其在工業(yè)生產(chǎn)中的適用性.化學(xué)脫漆法效率高,但耗時(shí)長(zhǎng),易導(dǎo)致二次污染問題.熱解法不僅效率高,而且銅損耗率低,是目前從廢漆包線中回收銅的行業(yè)中主流工藝之一[5-6].然而廢銅漆包線在熱解過程會(huì)產(chǎn)生一些煙氣污染物,如:NO、SO2、HCl和二噁英等.其中,二噁英是毒性極強(qiáng)的持久性有機(jī)污染物[7].現(xiàn)有研究表明,二噁英的生成反應(yīng)可分為均相反應(yīng)(500～800℃)和非均相反應(yīng)(200～500℃)[8].從形成途徑來看,主要包括:從頭合成[9]、前驅(qū)物合成[10]、氯酚和氯苯的重排反應(yīng)[11].在鋼鐵生產(chǎn)過程中,二噁英主要在燒結(jié)工序產(chǎn)生.燒結(jié)原料中鐵礦石和焦粉含有Cl等有害元素,為二噁英的生成提供了必備的氯源.同時(shí),鐵礦石中含有微量的銅,能夠催化二噁英生成.與燒結(jié)工序不同,廢銅漆包線熱解過程,二噁英生成的氯源來自于廢銅漆包線表面的有機(jī)涂層,且廢銅漆包線本身含有大量的銅,為二噁英的生成提供了催化條件.此外,燒結(jié)工序具有風(fēng)量大等特點(diǎn),導(dǎo)致二噁英排放濃度遠(yuǎn)低于廢銅漆包線熱解過程[12].隨著環(huán)保力度的不斷加強(qiáng),我國再生銅領(lǐng)域煙氣中二噁英的排放標(biāo)準(zhǔn)已由1ng I TEQ/Nm3調(diào)整至0.5ng I TEQ/Nm3.但截至目前在工業(yè)生產(chǎn)中對(duì)于二噁英的治理效果有限,缺乏高效低成本的商業(yè)化減排方案.因此,開發(fā)廢銅漆包線熱解過程二噁英減排技術(shù)至關(guān)重要.

減少二噁英排放的途徑分為源頭控制、過程減排和末端治理[13-14].源頭控制是一種通過控制原料質(zhì)量、優(yōu)化工藝條件和改進(jìn)爐型結(jié)構(gòu)來抑制二噁英前驅(qū)體形成,從而減少二噁英排放的技術(shù).然而該方法不能防止冷卻過程中二噁英的重新合成[15].末端治理包括吸附劑吸附技術(shù)和催化降解技術(shù),其中催化降解技術(shù)由于煙氣中較高的水分和粉塵以及高額的成本限制了其在工業(yè)上應(yīng)用[16],而吸附技術(shù)是目前工業(yè)上常用的煙氣中二噁英減排方法之一.過程減排方法是通過在生產(chǎn)區(qū)域噴灑抑制劑,抑制二噁英的生成,具有成本低、效率高的特點(diǎn),得到了廣泛的研究和應(yīng)用[17].

目前,有幾種類型的抑制劑被廣泛用于控制二噁英的形成,其中包括含N抑制劑、含S抑制劑和堿性抑制劑[18-19].已有研究表明,在垃圾焚燒爐中分別添加硫脲和尿素后,二噁英的排放總量分別由1.41ng I-TEQ/Nm3和140ng/m3降低到0.37ng I-TEQ/Nm3和36ng/m3[17,20].盡管現(xiàn)有文獻(xiàn)報(bào)道應(yīng)用于工業(yè)上的二噁英抑制劑,其減排率高達(dá)80%左右[21],但廢銅漆包線熱解煙氣中二噁英的排放濃度高達(dá)5.0～6.0ng I-TEQ/Nm3,通過添加抑制劑將二噁英的排放濃度降低到0.5ng I TEQ/Nm3以下仍是一個(gè)挑戰(zhàn).以往的研究大多只是針對(duì)添加抑制劑這一種方式,且抑制劑大多只在一個(gè)位置添加,導(dǎo)致二噁英的減排效果有限.為解決廢銅漆包線熱解煙氣中二噁英排放超標(biāo)問題,本研究提出添加抑制劑與吸附劑結(jié)合的“過程抑制+末端吸附”減排技術(shù)方案.考察了單獨(dú)添加抑制劑和抑制劑與吸附劑相結(jié)合的方式對(duì)熱解煙氣中二噁英的減排能力.研究了煙氣中二噁英的濃度及同系物分布,并分析了二噁英的減排機(jī)理,以期實(shí)現(xiàn)廢銅漆包線熱解過程二噁英超低排放.

1 原料與方法

1.1 試驗(yàn)系統(tǒng)及原料

本試驗(yàn)在安徽銅陵一家有色金屬加工現(xiàn)場(chǎng)的間歇式熱解爐上進(jìn)行,該熱解爐每爐廢銅漆包線熱解量約2t,研究所使用的廢銅漆包線由該公司提供(如圖1所示).表1為混合原料的主要化學(xué)成分,原料中主要以Cu元素為主,并含有少量的C、H、O、N和Cl等元素,其中Cl元素是導(dǎo)致二噁英生成的重要條件.試驗(yàn)中所用的抑制劑和吸附劑分別為質(zhì)量濃度9.1%的復(fù)合抑制劑(FHI)和比表面積為700～1500m2/g的椰殼型活性炭.如圖2所示,該試驗(yàn)系統(tǒng)主要由熱解爐、原料罐、運(yùn)料車、吸附裝置和煙囪組成.廢漆包線裝入原料罐后,通過運(yùn)料車運(yùn)送到熱解爐內(nèi)進(jìn)行熱解.圖3為熱解爐工作過程中不同位置的溫度變化情況,其中爐膛上區(qū)溫度均值為668℃,峰值為789℃;爐膛下區(qū)溫度均值為570℃,峰值為659℃;煙氣出口溫度均值為379℃,峰值為589℃.

圖1 廢銅漆包線原料

表1 廢銅漆包線的主要化學(xué)成分(質(zhì)量分?jǐn)?shù)/%)

圖2 試驗(yàn)系統(tǒng)示意

圖3 熱解爐不同位置溫度變化情況

1.2 試驗(yàn)設(shè)計(jì)

表2 試驗(yàn)方案

根據(jù)工業(yè)現(xiàn)場(chǎng)實(shí)際工況,設(shè)置本試驗(yàn)熱解爐的廢銅漆包線處理量為2t/爐,熱解時(shí)間為2h/爐.熱解爐爐頂和煙氣出口處開孔后,FHI通過爐頂(FHI噴灑點(diǎn)1)和煙氣出口處(FHI噴灑點(diǎn)2)噴灑.試驗(yàn)過程中,FHI噴灑量按照廢銅漆包線處理量的0.2%計(jì)算,每爐FHI噴灑量為40L,噴灑時(shí)間2h.活性炭添加在吸附裝置中,添加量為10kg.熱解煙氣二噁英采樣點(diǎn)分別設(shè)置在吸附裝置前后兩個(gè)位置,即圖2所示的采樣點(diǎn)1和采樣點(diǎn)2,具體方案如表2所示.二噁英樣品從熱解爐點(diǎn)火開始進(jìn)行采集,直到熱解結(jié)束后為一個(gè)樣品,每進(jìn)行一組熱解實(shí)驗(yàn),將樣品取出保存,用于檢測(cè).

1.3 樣品采集與檢測(cè)方法

二噁英采樣裝置采用ZR-3720型廢氣二噁英采樣器,通過利用該裝置對(duì)熱解煙氣二噁英樣品進(jìn)行等速采集,采樣時(shí)間為2h.采集的樣品首先需要進(jìn)行預(yù)處理,采用甲苯萃取,并用旋轉(zhuǎn)蒸發(fā)儀(EYEL4,東京理化)將樣品濃縮到3mL,并采用多層硅膠凈化,其中多層硅膠由酸、堿和中性硅膠組成,最后使用氮吹儀(N-EVAP)將凈化后的樣品濃縮至200μL.二噁英類化合物的分析由Autospec Ultima高分辨率質(zhì)譜和Hewlett-Packard6890氣相色譜(HRGC/HRMS)完成.共平面多氯聯(lián)苯(Co-PCBs)的分析由JMS-700高分辨率質(zhì)譜和Hewlett-Packard6 890氣相色譜(HRGC/HRMS)完成.非極性氣相毛細(xì)管色譜柱(DB-5MS柱)用于分析Co-PCBs.極性氣相毛細(xì)管色譜柱(SP-2331柱)用于分析四氯代二苯并二噁英/呋喃(TeCDD/Fs)、五氯代二苯并二噁英/呋喃(PeCDD/Fs)、六氯代二苯并二噁英/呋喃(HxCDD/Fs)同系物及其2,3,7,8-取代異構(gòu)體.中等極性氣相毛細(xì)管色譜柱(DB17-HT柱)用于分析七氯代二苯并二噁英/呋喃(HpCDD/Fs)、八氯代二苯并二噁英/呋喃(OCDD/Fs)同系物及其2,3,7,8-取代異構(gòu)體.此外,使用I-TEFWHO-05計(jì)算國際毒性當(dāng)量(I-TEQ),所有樣品的濃度根據(jù)一個(gè)標(biāo)準(zhǔn)大氣壓,273K和11% O2的干燥空氣進(jìn)行歸一化.

2 結(jié)果與討論

2.1 煙氣中PCDD/Fs的含量變化

圖4 煙氣中PCDD/Fs的排放濃度和I-TEQ值

圖4為不同實(shí)驗(yàn)中PCDD/Fs的排放濃度及I-TEQ值.由圖可知,基準(zhǔn)試驗(yàn)(T1),熱解煙氣中PCDD/Fs的排放濃度為54.32ng/Nm3,I-TEQ值為5.3ng I-TEQ/Nm3.在廢銅漆包線熱解過程中噴灑FHI后(T2),熱解煙氣中PCDD/Fs的排放濃度從54.32ng/Nm3降低到5.08ng/Nm3,減排效率為90.65%;I-TEQ值從5.3ng I-TEQ/Nm3降低到0.83ng I-TEQ/Nm3,減排效率為84.34%,說明FHI對(duì)廢銅漆包線熱解過程PCDD/Fs的生成具有較為顯著的抑制作用.盡管減排效率較高,但減排后的二噁英排放濃度仍高于0.5ng I-TEQ/Nm3(不能滿足國家排放標(biāo)準(zhǔn)).相比之下,應(yīng)用噴灑FHI和吸附劑吸附協(xié)同減排技術(shù)后(T3),熱解煙氣中PCDD/Fs的排放濃度和I-TEQ值分別從54.32ng/Nm3、5.3ng I-TEQ/Nm3急劇下降到1.10ng/Nm3、0.08ng I-TEQ/Nm3,減排效率分別高達(dá)97.97%和98.49%(遠(yuǎn)低于國家排放標(biāo)準(zhǔn)),可見,采用噴灑FHI與吸附劑吸附二者相結(jié)合的方式,對(duì)廢銅漆包線熱解煙氣中PCDD/Fs的減排效果十分顯著.

2.2 PCDD/Fs同系物分布

圖6 煙氣中I-TEQ值的分布

如上文所述,發(fā)現(xiàn)通過噴灑FHI的方式來抑制廢銅漆包線熱解過程PCDD/Fs形成的均相和非均相反應(yīng),PCDD/Fs的排放濃度能夠降低到0.83ng I-TEQ/Nm3,若輔以吸附劑進(jìn)行吸附,則PCDD/Fs的排放濃度能夠進(jìn)一步降低到0.08ng I-TEQ/Nm3.為了探究PCDD/Fs的減排機(jī)理,分析了2,3,7,8-取代的PCDD/Fs同系物的分布.從圖5(a)中能夠看出減排前PCDF的同系物主要為1234678-HpCDF,濃度為11.90ng/Nm3,其次為OCDF,濃度為8.36ng/Nm3.孟聰?shù)萚22]在進(jìn)口再生銅冶煉煙氣中發(fā)現(xiàn)二噁英同系物濃度最高的為OCDF和1234678-HpCDF,與本研究結(jié)果相似.噴灑FHI結(jié)合活性炭吸附后,T3中1234678-HpCDF的濃度降低至0.299ng/Nm3,OCDF的濃度降低至0.089ng/Nm3.PCDF分布中高氯代PCDF同系物主要以HpCDFs和OCDF為主,分別占49.5%(T1)、19.7%(T2)和51.3%(T3).如圖5(b)所示,相比之下低氯代PCDF同系物(即PeCDFs和TCDF)的相對(duì)分布比例呈先上升后下降趨勢(shì).PCDDs的分布由圖5(c)可以看出,OCDD和1234678-HpCDD的排放濃度明顯高于其它同系物,其濃度分別為5.37和2.86ng/Nm3.噴灑FHI后,從T2試驗(yàn)采集的樣品中所有PCDD同系物的排放濃度均有不同程度的降低.此外,低氯代PCDD同系物(即PeCDDs和TCDD)比例增加,尤其是T2試驗(yàn)中高達(dá)43.0%.如上所述,可以看出,無論是PCDF還是PCDD同系物,向煙氣中噴灑FHI后,高氯代PCDD/Fs同系物的分布比例下降,而低氯代PCDD/Fs同系物的分布比例增加,說明氯化反應(yīng)受到抑制或發(fā)生了高氯化PCDD/Fs的脫氯反應(yīng)[23].

圖6為煙氣中PCDD/Fs同系物I-TEQ值百分比分布圖,由圖可見,T1中PCDF同系物的I-TEQ值占比最大,為53.76%,其中23478PeCDF貢獻(xiàn)最大,為51.43%,結(jié)果與之前的研究相一致.噴灑FHI后,PCDF同系物I-TEQ值占比降低到50.96%(T2);噴灑FHI結(jié)合活性炭吸附后,PCDF同系物I-TEQ值占比降低到39.72%(T3).

2.3 二噁英減排機(jī)理分析

基于廢銅漆包線成分特點(diǎn)及上述PCDD/Fs同系物分布的分析,通過以下四種途徑實(shí)現(xiàn)了二噁英的減排:(1)金屬銅及其化合物催化活性減弱,抑制了從頭合成反應(yīng);(2)Cl2濃度的降低影響了氯化反應(yīng)和從頭合成反應(yīng);(3)FHI分解過程形成活性自由基阻礙PCDD/Fs的形成或攻擊PCDD/Fs的分子鍵;(4)活性炭的物理吸附.

研究認(rèn)為金屬銅及其化合物,如Cu2O、CuSO4和CuCl2·2H2O等,是從頭合成PCDD/Fs的催化劑,對(duì)PCDD/Fs的生成具有催化作用[24].噴灑FHI后,FHI中的分子可以強(qiáng)烈吸附在堿性氧化物表面的活性反應(yīng)位點(diǎn)上,并與廢漆包線里的金屬銅形成穩(wěn)定的配合物,如[CH4N2O-Cu]+或[(CH4N2O)2-Cu]+,能夠降低金屬銅及其化合物的催化活性[25-26].有研究[27]指出CuCl2不僅是PCDD/Fs形成的催化劑,也是從頭合成的氯源,因此FHI通過降低金屬銅及其化合物的催化活性能夠極大地抑制PCDD/Fs的從頭合成反應(yīng).

熱解過程中廢銅漆包線中的氯元素可能以Cl2或者HCl的形式存在,由于苯環(huán)氯化反應(yīng)的反應(yīng)物是Cl2而不是HCl,研究者普遍認(rèn)為Cl2的含量直接影響PCDD/Fs的形成[28].上述試驗(yàn)結(jié)果中,FHI的加入對(duì)PCDFs的抑制能力比PCDDs更強(qiáng),對(duì)高氯PCDD/Fs的抑制效果更明顯.這證明了噴灑FHI可以降低煙氣中Cl2的含量.因此,可以認(rèn)為,在熱解爐中,FHI分解產(chǎn)生的NH3可以通過反應(yīng)式(1)與Cl2反應(yīng)抑制氯化反應(yīng)[29],或者與HCl發(fā)生反應(yīng)(反應(yīng)式(2)),并且金屬銅及其化合物的催化活性減弱,抑制了Deacon反應(yīng)(反應(yīng)式(3)),從而限制了Cl2的生成[30-31],而Cl2濃度的降低會(huì)顯著影響PCDD/Fs的從[32]頭合成路線.

8NH3+3Cl2→6NH4Cl+N2(1)

NH3+HCl→NH4Cl(2)

4HCl+O2→2Cl2+H2O(3)

FHI大約在135℃進(jìn)行分解,在600℃有效分解率達(dá)到100%[33-34].FHI分解過程中能夠形成含N自由基(NH2*)和H自由基(H*)[35-36].如圖7所示,NH2*可與廢漆包線表面的殘?zhí)拷Y(jié)合,并占據(jù)殘?zhí)勘砻娴幕钚晕恢?使得將要合成為二噁英的有機(jī)物轉(zhuǎn)而合成為相似結(jié)構(gòu)的含氮有機(jī)物,阻礙了二噁英的生成,從而降低了煙氣中持久性有機(jī)物的毒性和危害;而H*具有很強(qiáng)的活性,能夠進(jìn)攻二噁英分子上C-O鍵兩端的C原子和O原子,在H*的進(jìn)攻下二噁英C-O鍵以發(fā)生斷裂,從而使得二噁英發(fā)生開環(huán)反應(yīng),實(shí)現(xiàn)二噁英的降解和抑制(如圖8所示),從而減少二噁英的排放[37-38].圖5表明噴灑FHI后高氯PCDD/Fs同系物的分布比例下降,低氯PCDD/Fs同系物的分布比例增加,進(jìn)一步證實(shí)了上述推論.

圖7 NH2*抑制二噁英產(chǎn)生的示意

圖8 H*進(jìn)攻C原子和O原子示意

理論認(rèn)為,二噁英分子是一種典型的平面分子,三個(gè)環(huán)都在同一平面上,這種結(jié)構(gòu)比較容易進(jìn)入活性炭的微孔中,且活性炭的基本微晶為二維平面結(jié)構(gòu),當(dāng)煙氣中的二噁英分子與活性炭接觸時(shí),排列成六角形的碳原子平行層面會(huì)對(duì)二噁英分子產(chǎn)生范德華力作用,使得二噁英分子被穩(wěn)定吸附在活性炭的微孔中[39].因此,未被抑制生成的二噁英在煙氣末端被活性炭捕集吸附,實(shí)現(xiàn)了二噁英的超低排放(0.08ng I-TEQ/Nm3).

基于本研究提出的“過程抑制+末端減排”的二噁英減排技術(shù),企業(yè)只需在原有的熱解爐工藝流程基礎(chǔ)上,添加抑制劑噴灑設(shè)備及活性炭吸附裝置,即可實(shí)現(xiàn)廢銅漆包線熱解過程二噁英的超低排放.廢銅漆包線經(jīng)過高溫?zé)峤庵?經(jīng)過冷卻、破碎、風(fēng)選和篩分等工序后,能夠使金屬銅和殘?zhí)坑行Х蛛x,分別得到產(chǎn)品金屬銅和副產(chǎn)品碳粉.通過熱解法處理廢銅漆包線對(duì)后續(xù)銅制品的品質(zhì)幾乎沒有影響,該方法已在企業(yè)廣泛應(yīng)用.

3 結(jié)論

3.1 廢銅漆包線熱解煙氣中二噁英的排放濃度為54.32ng/Nm3, I-TEQ值為5.3ng I-TEQ/Nm3.PCDF的同系物主要為1234678-HpCDF和OCDF,其濃度分別為11.90和8.36ng/Nm3;PCDD的同系物主要為1234678-HpCDD和OCDD,其濃度分別為2.86和5.37ng/Nm3.

3.2 單獨(dú)噴灑復(fù)合抑制劑進(jìn)行減排后,熱解煙氣中PCDD/Fs的排放濃度從54.32ng/Nm3降低到5.08ng/Nm3,減排效率為90.65%;I-TEQ值從5.3ng I-TEQ/Nm3降低到0.83ng I-TEQ/Nm3,減排效率為84.34%,采用噴灑復(fù)合抑制劑和活性炭吸附協(xié)同減排后,熱解煙氣中PCDD/Fs的排放濃度和I-TEQ值分別從54.32ng/Nm3、5.3ng I-TEQ/Nm3急劇下降到1.10ng/Nm3、0.08ng I-TEQ/Nm3,減排效率分別高達(dá)97.97%、98.49%,低于國家排放標(biāo)準(zhǔn).

3.3 該過程抑制結(jié)合末端吸附的二噁英減排技術(shù)其減排機(jī)理在于減弱了金屬銅及其化合物的催化活性,抑制了從頭合成反應(yīng);Cl2濃度降低影響了氯化反應(yīng)和從頭合成反應(yīng);復(fù)合抑制劑分解過程形成活性自由基阻礙了PCDD/Fs的形成或攻擊PCDD/Fs的分子鍵;活性炭對(duì)PCDD/Fs的物理吸附.

[1] 胡辰瑋,李 彬,吳玉鋒,等.廢有機(jī)-無機(jī)復(fù)合材料熱解回收技術(shù)現(xiàn)狀與展望 [J]. 材料導(dǎo)報(bào), 2021,35(21):21091-21098,21112. Hu C W, Li B, Wu Y F, et al. Status and progress of recycling waste organic-inorganic composites by pyrolysis [J]. Materials Reports, 2021,35(21):21091-21098,21112.

[2] Sanmartín P, Cappitelli F, Mitchell R. Current methods of graffiti removal: A review [J]. Construction and Building Materials, 2014,71: 363-374.

[3] Liu W, Wang N, Han J W, et al. Thermal degradation behaviors and evolved products analysis of polyester paint and waste enameled wires during pyrolysis [J]. Waste Management, 2020,107:82-90.

[4] Huang Z D, Zhou J H, Hu C F, et al. Role and mechanism of formic acid in stripping of paint comprising epoxy primer and polyurethane topcoat [J]. Journal of Coatings Technology and Research, 2018,15: 385-394.

[5] Li B Y, Wang X L, Xia Z D, et al. Co-pyrolysis of waste polyester enameled wires and polyvinyl chloride: Evolved products and pyrolysis mechanism analysis [J]. Journal of Analytical and Applied Pyrolysis, 2023,169:105816.

[6] Ren Y, Cao C Y, Hu H Y, et al. Transformation behavior and fate of chlorine in polychloroprene (PCP) during its pyrolysis [J]. Fuel, 2022,317:123573.

[7] 王肇嘉,秦 玉,顧 軍,等.生活垃圾焚燒飛灰二噁英控制技術(shù)研究進(jìn)展[J]. 環(huán)境工程, 2021,39(10):116-123. Wang Z J, Qin Y, Gu J, et al. Research progress of dioxin control technologies in fly ash from domestic waste incineration [J]. Environmental Engineering, 2021,39(10):116-123.

[8] Zhang J J, Zhang S G, Liu B. Degradation technologies and mechanisms of dioxins in municipal solid waste incineration fly ash: A review [J]. Journal of Cleaner Production, 2020,250:119507.

[9] Ying Y X, Ma Y F, Wang X X, et al. Emission, partition, and formation pathway of polychlorinated dibenzo-p-dioxins and dibenzofurans during co-disposal of industrial waste with municipal solid waste [J]. Journal of Environmental Chemical Engineering, 2023,11(1):109242.

[10] Ma Y F, Lin X Q, Chen Z L, et al. Influences of PN-containing inhibitor and memory effect on PCDD/F emissions during the full-scale municipal solid waste incineration [J]. Chemosphere, 2019,228:495-502.

[11] Weber R, Hagenmaier H. PCDD/PCDF formation in fluidized bed incineration [J]. Chemosphere, 1999,38(11):2643-2654.

[12] 龍紅明,吳雪健,李家新,等.燒結(jié)過程二噁英的生成機(jī)理與減排途徑 [J]. 燒結(jié)球團(tuán), 2016,41(3):46-51. Long H M, Wu X J, Li J X, et al. Formation mechanism of dioxins in sintering process and their emission reduction approaches [J]. Sintering and Pelletizing, 2016,41(3):46-51.

[13] 梁寶瑞,趙榮志,張文伯,等.鋼鐵行業(yè)二噁英的形成機(jī)理及降解方法研究現(xiàn)狀 [J]. 中國冶金, 2021,31(2):1-5. Liang B R, Zhao R Z, Zhang W B, et al. Research status of formation mechanism and degradation methods of dioxins [J]. China Metallurgy, 2021,31(2):1-5.

[14] 李 雁,郭昌勝,侯 嵩,等.固體廢物焚燒過程中二噁英的排放和生成機(jī)理研究進(jìn)展[J]. 環(huán)境化學(xué), 2019,38(4):746-759. Li Y, Guo C S, Hou S, et al. The formation mechanisms and emission of dioxin during the solid waste incineration process [J]. Environmental Chemistry, 2019,38(4):746-759.

[15] Chang M B, Lin J J. Memory effect on the dioxin emissions from municipal waste incinerator in Taiwan [J]. Chemosphere, 2001,45(8): 1151-1157.

[16] Li W S, Yan D H, Li L, et al. Review of thermal treatments for the degradation of dioxins in municipal solid waste incineration fly ash: Proposing a suitable method for large-scale processing [J]. Science of The Total Environment, 2023,875:162565.

[17] Guo X X, Ma Y F, Lin X Q, et al. Reduction of polychlorinated dibenzo-p-dioxins and dibenzofurans by chemical inhibition and physisorption from a municipal solid waste incineration system [J]. Energy & Fuels, 2020,34(9):11237-11247.

[18] 謝 豐,王云剛,顏 楓,等.生活垃圾焚燒過程中二噁英抑制劑研究進(jìn)展 [J]. 環(huán)境工程, 2022,40(7):222-231,247. Xie F, Wang Y G, Yan F, et al. Research progress of dioxin inhibitors for municipal solid waste incineration [J]. Environmental Engineering, 2022,40(7):222-231,247.

[19] 劉芃巖,高 蘭,張雅婧,等.堿性及含硫化合物對(duì)十溴聯(lián)苯醚熱降解的影響 [J]. 中國環(huán)境科學(xué), 2020,40(6):2658-2663. Liu P Y, Gao L, Zhang Y J, et al. Influence of alkaline and sulfur- containing compounds on the thermal degradation of decabromodiphenyl ether [J]. China Environmental Science, 2020, 40(6):2658-2663.

[20] Zhan M X, Chen T, Lin X Q, et al. Suppression of dioxins after the post-combustion zone of MSWIs [J]. Waste Management, 2016,54: 153-161.

[21] Qian L X, Wang Y F, Liu M L, et al. Performance evaluation of urea injection on the emission reduction of dioxins and furans in a commercial municipal solid waste incinerator [J]. Process Safety and Environmental Protection, 2021,146:577-585.

[22] 孟 聰,岳 波,孟棒棒,等.進(jìn)口再生銅冶煉煙氣中二噁英的生成特性[J]. 環(huán)境化學(xué), 2021,40(8):2462-2472. Meng C, Yue B, Meng B B, et al. Formation characteristics of PCDD/Fs in imported secondary copper smelting flue gas [J]. Environmental Chemistry, 2021,40(8):2462-2472.

[23] Altarawneh M, Dlugogorski B Z, Kennedy E M, et al. Mechanisms for formation, chlorination, dechlorination and destruction of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) [J]. Progress in energy and combustion science, 2009,35(3):245-274.

[24] Ba T, Zheng M H, Zhang B, et al. Estimation and characterization of PCDD/Fs and dioxin-like PCBs from secondary copper and aluminum metallurgies in China [J]. Chemosphere, 2009,75(9):1173-1178.

[25] 張玉才,龍紅明,春鐵軍,等.原料銅和氯元素對(duì)二噁英排放的影響及抑制技術(shù) [J]. 鋼鐵, 2015,50(12):42-46. Zhang Y C, Long H M, Chun T J, et al. Influence of Cu and Cl elements from raw materials on the emission of PCDD/Fs and its emission reduction technology [J]. Iron & Steel, 2015,50(12):42-46.

[26] Luna A, Amekraz B, Morizur J P, et al. Reactions between guanidine and Cu+in the gas phase. An experimental and theoretical study [J]. The Journal of Physical Chemistry A, 1997,101(33):5931-5941.

[27] Lin X Q, Mao T Y, Ma Y F, et al. Influence of Different Catalytic Metals on the Formation of PCDD/Fs during Co-combustion of Sewage Sludge and Coal [J]. Aerosol and Air Quality Research, 2022, 22:220268.

[28] Ji Z Y, Huang B B, Gan M, et al. Dioxins control as co-processing water-washed municipal solid waste incineration fly ash in iron ore sintering process [J]. Journal of Hazardous Materials, 2022,423: 127138.

[29] Long H M, Li J X, Wang P, et al. Emission reduction of dioxin in iron ore sintering by adding urea as inhibitor [J]. Ironmaking & Steelmaking, 2011,38(4):258-262.

[30] Chen Z L, Lin X Q, Lu S Y, et al. Suppressing formation pathway of PCDD/Fs by SN-containing compound in full-scale municipal solid waste incinerators [J]. Chemical Engineering Journal, 2019,359:1391- 1399.

[31] Lu S Y, Xiang Y F, Chen Z L, et al. Development of phosphorus-based inhibitors for PCDD/Fs suppression [J]. Waste Management, 2021,119:82-90.

[32] Wang X X Ma Y F, Lin X Q, et al. Inhibition on de novo synthesis of PCDD/Fs by an N–P-containing compound: Carbon gasification and kinetics [J]. Chemosphere, 2022,292:133457.

[33] Tischer S, B?rnhorst M, Amsler J, et al. Thermodynamics and reaction mechanism of urea decomposition [J]. Physical Chemistry Chemical Physics, 2019,21(30):16785-16797.

[34] Kuntz C, Kuhn C, Weickenmeier H, et al. Kinetic modeling and simulation of high-temperature by-product formation from urea decomposition [J]. Chemical Engineering Science, 2021,246:116876.

[35] Kasai E, Kuzuhara S, Goto H, et al. Reduction in dioxin emissions by the addition of urea as aqueous solution to high-temperature combustion gas [J]. ISIJ International, 2008,48(9):1305-1310.

[36] Schaber P M, Colson J, Higgins S, et al. Thermal decomposition (pyrolysis) of urea in an open reaction vessel [J]. Thermochimica Acta, 2004,424(1/2):131-142.

[37] Qian L X, Chun T J, Long H M, et al. Emission reduction research and development of PCDD/Fs in the iron ore sintering [J]. Process Safety and Environmental Protection, 2018,117:82-91.

[38] Fueno H, Tanaka K, Sugawa S. Theoretical study of the dechlorination reaction pathways of octachlorodibenzo-p-dioxin [J]. Chemosphere, 2002,48(8):771-778.

[39] 潘雪君.活性炭粉末脫除二噁英的研究 [D]. 寧波:寧波大學(xué), 2012. Pan X J. Study on dioxins adsorption by power activated carbon [D]. Ningbo: Ningbo University, 2012.

Emission characteristics and abatement mechanism of dioxins in the pyrolysis flue gas of scrap copper enameled wire.

FAN Chun-long1, QIAN Li-xin1, DING Long1, SHEN Tao2, YAO Ming1, CHUN Tie-jun1, HAN Yi-jiao2, LONG Hong-ming1,3*

(1.School of Metallurgical Engineering, Anhui University of Technology, Maanshan 243002, China；2.Tongling Zhuoxiang Copper Material Technology Co.Ltd., Tongling 244100, China；3.Key Laboratory of Metallurgical Emission Reduction & Resource Utilization, Ministry of Education, Maanshan 243002, China)., 2023,43(11)：5855～5862

This paper analyzed generation and emission characteristics of dioxins in the flue gas of a 2t/furnace intermittent pyrolysis furnace were analyzed, and a dioxin control technology based on "process inhibition and terminal reduction" was proposed. The effects of adding inhibitors to the pyrolysis process of scrap copper enameled wire in combination with terminal activated carbon adsorption on the emission of dioxins and their congeners were investigated. The results showed that the emission concentration of PCDD/Fs in the pyrolysis furnace flue gas was 54.32ng/Nm3, and the I-TEQ value was 5.30ng I-TEQ/Nm3. The congeners of PCDF were mostly 1234678-HpCDF and OCDF, and the congeners of PCDD were mostly 1234678-HpCDD and OCDD. By applying the technology of "process inhibition and the terminal reduction", the composite inhibitor can reduce the catalytic activity of copper metal and its compounds, lower the concentration of Cl2, and inhibit the de novo synthesis reaction, while the reactive radicals formed during the decomposition of the composite inhibitor can prevent the formation of PCDD/Fs or attack the molecular bonds of PCDD/Fs, thus inhibiting the formation of dioxins. Combined with the physical adsorption of the terminal activated carbon, the dioxin emission concentration in the pyrolysis furnace flue gas was reduced to 1.10ng/Nm3and the I-TEQ value was reduced to 0.08ng I-TEQ/Nm3, which meets the national environmental protection standard.

scrap copper enameled wire；pyrolysis；dioxins；compound inhibitors；activated carbon；emission reduction

X511;X705

A

1000-6923(2023)11-5855-08

范春龍(2000-),男,安徽阜陽人,安徽工業(yè)大學(xué)碩士研究生,主要從事煙氣污染物減排技術(shù)研究.發(fā)表論文1篇.fcl_ahut@163.com.

范春龍,錢立新,丁 龍,等.廢漆包線熱解煙氣二噁英排放特性與減排機(jī)理 [J]. 中國環(huán)境科學(xué), 2023,43(11):5855-5862.

Fan C L, Qian L X, Ding L, et al. Emission characteristics and abatement mechanism of dioxins in the pyrolysis flue gas of scrap copper enameled wire [J]. China Envirenmental Science, 2023,43(11):5855-5862.

2023-04-07

國家重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(2021YFC1910501)

* 責(zé)任作者, 教授, yaflhm@126.com