流化床垃圾焚烧炉产生的有毒二(口恶)英同类物分布研究

测定了流化床垃圾焚烧炉焚烧产生的飞灰、烟尘和烟气中的2,3,7,8位氯取代二(口恶)英同类物的含量及其毒性当量.结果表明,产生的二(口恶)英主要存在于飞灰中,烟气中的含量很少.飞灰中二(口恶)英总浓度和毒性当量分别为8.44ng/g和0.80ng/g,经过布袋除尘器后的烟尘和烟气中二(口恶)英的浓度之和与毒性当量之和分别为0.34 ng/m3和0.02 ng/m3,而布袋除尘器前的烟尘和烟气中二(口恶)英的浓度之和与毒性当量之和分别为40.78 ng/m3和3.01ng/m3.飞灰和烟尘中2,3,7,8位氯取代二(口恶)英同类物的分布相似,但是与烟气中2,3,7,8位氯取代二(口恶)英同类物的分布差别较大.通过了解有毒二(口恶)英同类物的分布,可以进一步优化流化床垃圾焚烧炉的焚烧条件,降低二(口恶)英的排放量,减少垃圾焚烧对环境的污染.     

小型焚烧设施烟气中二噁英类的排放和控制

对中国典型的小型焚烧设施现状和二噁英类排放进行了初步调查研究,未经处理的小型垃圾焚烧设施烟气中二噁英类毒性当量(TEQ)大于6 ng/m3,小型火化机烟气中二噁英类TEQ大于5 ng/m3.设计并检验了布袋除尘器和活性炭滤布的二噁英类去除效果.仅使用布袋除尘器二噁英类去除率不高,布袋除尘器和活性炭滤布联用可以有效去除飞灰和气相中的二噁英类,去除率达到90%左右,可达到《生活垃圾焚烧污染控制标准》(GB 18485-2001)二噁英类排放标准.     

生活垃圾焚烧飞灰中元素分布与二噁英的关联性分析

以国内不同地区的14个生活垃圾焚烧炉的布袋除尘器飞灰为研究对象,对飞灰中主要元素的分布和二噁英(PCDD/Fs)含量进行测定,并采用因子分析研究不同炉型飞灰特性及其与PCDD/Fs分布之间的关联性。结果表明:在生活垃圾焚烧飞灰中,Si、Al、Fe、O和Na、K、Cl、S两组元素分布各自呈明显的两两正相关性。流化床炉飞灰中Si、Al、Fe、O的含量明显高于炉排炉飞灰,而Na、K、Cl、S的含量则与之相反。飞灰中PCDD/Fs为0.17~94.49ng/g,毒性当量为0.02~2.53ng I-TEQ/g,不同飞灰差距较大。炉排炉飞灰通常含有高氯代的多氯代二苯并-对-二噁英(PCDDs),PCDDs、多氯代二苯并呋喃(PCDFs)的质量比(PCDDs/PCDFs)均大于1;流化床炉飞灰含有的PCDFs多于炉排炉飞灰,PCDDs/PCDFs均小于1。流化床炉飞灰中Cu、Ca与PCDD/Fs含量有明显的线性关系,相关系数(R)分别为0.86、0.90。     

典型行业周边土壤中二噁英浓度分布特性研究

为了探究典型行业周边土壤中二噁英浓度,针对钢铁冶炼、生活垃圾焚烧和危险废物焚烧等行业开展了周边土壤中二噁英浓度分布特性的研究。结果表明,典型行业周边土壤中二噁英毒性当量浓度为0.77~3.80ng TEQ/kg,平均为1.98ng TEQ/kg,其中钢铁冶炼企业周边土壤中二噁英的平均毒性当量浓度(2.50ng TEQ/kg)最高,其次是生活垃圾焚烧企业(2.01ng TEQ/kg),危险废物焚烧企业周边土壤中二噁英的平均毒性当量浓度最低(1.44ng TEQ/kg)。钢铁冶炼企业浅层土壤(0~200mm)中二噁英毒性当量浓度明显高于深层土壤(200~400mm),土壤中二噁英毒性当量浓度与空气中二噁英的沉降作用有关。钢铁冶炼企业土壤中二噁英分布与最大落地浓度点、污染源中二噁英分布均相近,而生活垃圾焚烧企业和危险废物焚烧企业土壤中二噁英分布与最大落地浓度点、污染源中二噁英分布差异较大。     

医疗垃圾热解焚烧实验研究

医疗垃圾是一种对环境危害极大的危险废弃物。用一种固定炉排炉热解焚烧系统，对广州市部分医院的医疗垃圾进行了热解焚烧及尾气净化试验，并对焚烧工况、烟气中主要的污染物含量及灰渣的灼减率进行分析。分析结果表明：稳定运行时炉膛平均温度在850℃左右，二燃室平均温度在1000℃以上；尾气中CO、NOx，HCI和SO2浓度分别为：71mg／m^3、125mg／m^3、27．8mg／m^3和21mg／m^3，灰渣的灼减率为2．7％。均远远低于标准限值。     

焦炭烘干机烟尘治理

采用脉动－拓吹布袋除尘器治理处理焦炭烘干机烟气，烟尘排放浓度为２４．７ｍｇ／Ｎｍ６３，同时避免了原有湿式除尘废水的污染。     

GC—MS方法测定垃圾焚烧炉飞灰中的二恶英

采用索氏抽提，多级硅胶／氧化铝柱层析等预处理方法，提纯分离出垃圾焚烧炉飞灰中的恶英并进行ＧＣ－ＭＳ分析，检出所测样品中存在的６￣８个氯取代的二恶英。     

GC-MS方法测定垃圾焚烧炉飞灰中的二噁

采用索氏抽提，多级硅胶／氧化铝柱层析等预处理方法，提纯分离出垃圾焚烧炉飞灰中的噁并进行ＧＣ－ＭＳ分析，检出所测样品中存在有６～８个氯取代的二噁。     

小型简易生活垃圾焚烧炉二噁英类排放特征及呼吸暴露风险评估

通过现场采样调查3个小型简易生活垃圾焚烧炉二噁英类(PCDD/Fs)排放水平,并应用AERMOD模型和呼吸暴露评价方法对PCDD/Fs排放进行环境风险评估。结果表明:(1)焚烧炉烟气中PCDD/Fs毒性当量浓度为4.88～24.88ng TEQ/m~3(均为标准条件下气体体积),均高于《生活垃圾焚烧污染控制标准》(GB 18485—2014)限值(0.1ng TEQ/m~3);炉渣中PCDD/Fs毒性当量浓度为91～231ng TEQ/kg。(2)N1～N3焚烧炉PCDD/Fs年均地面毒性当量浓度预测最大值分别为0.60、0.26、0.27pg TEQ/m~3,周边最近居民点的年均地面毒性当量浓度预测值分别为0.10、0.01、0.19pg TEQ/m~3,均没有超过日本年均值标准(0.6pg TEQ/m~3)。(3)小型简易生活垃圾焚烧炉预测区域人群PCDD/Fs呼吸摄入量最大值均低于0.4pg TEQ/(kg·d),而且海拔较低、地形平坦有利于PCDD/Fs的扩散稀释。     

垃圾焚烧过程中影响重金属分布因素的研究

在转式垃圾焚烧炉和固定床加热炉中，研究了有机垃圾焚烧过程中温度、水分、无机氯及有机氯对几种重金属分布的影响。研究结果表明，焚烧垃圾过程中焚烧温度对重金属分布特性的影响特性不一，重金属锌和铅容易转移到气相中去，而重金属镍和铬大部分是以固态形式残留在底渣中；水能与重金属及其化合物发生反应，引起物质转变，影响重金属的分布；氯的存在也影响重金属的分布特性，氯的参与使重金属更易向飞灰或烟气中迁移。     

销毁含多氯联苯废弃物焚烧炉的二噁、类二噁和多氯联苯排放

我国正在研制专用于销毁高浓度多氯联苯（ＰＣＢｓ）的焚烧炉,主要处理废旧的含（ＰＣＢｓ）的电力电容器和变压器,应用可靠准确的监测方法测定了试验性焚烧炉渣、烟灰排气和废水中的二口恶口英（ｄｉｏｘｉｎｓ）,类二口恶口英多氯联苯（ｄｉｏｘｉｎｌｉｋｅＰＣＢｓ）和ＰＣＢｓ含量,结果表明该炉试烧高浓度ＰＣＢｓ时,焚毁率可以达到９９．９９９９％,炉渣中的２,３,７,８ＴＣＤＤ毒性当量为８７．８６ｐｇＴＥＱ／ｇ,烟灰中残留二口恶口英和类二口恶口英的总２,３,７,８ＴＣＤＤ毒性当量为４７．２３ｎｇＴＥＱ／ｇ．     

Study of PCDD/Fs distribution in fly ash,ash deposits,and bottom ash from a medical waste incinerator in China

Over the past decades in China, the number of medical waste incinerators (MWIs) has been rising rapidly, causing emissions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In this study, samples of fly ash, ash deposits, and bottom ash from typical MWIs were analyzed for PCDD/Fs and their distribution characteristics. Results showed international toxic equivalent (I-TEQ) values in the range of 6.9–67 ng I-TEQ/g in fly ash and ash deposits, whereas the concentration in bottom ash was extremely low (only 1.33 pg I-TEQ/g), yet the generation of PCDD/Fs was mostly de novo synthesis in fly ash and ash deposits according to the ratio of PCDFs to PCDDs; the major distribution differences of PCDD/Fs in fly ash was manifested by the content of toxic furan 2,3,7,8-TCDF, but other toxic PCDD/Fs showed similar distribution. Other findings are that 2,3,4,7,8-PeCDF had the most contribution to TEQ concentration, and that the most abundant toxic furan congener is 1,2,3,4,6,7,8-HpCDF. Correlation analysis showed that there was no significant correlation between PCDD/Fs concentration and several other physical and chemical parameters.

Implications: This paper is of interest because it presents the emission performances of PCDD/Fs in ash from medical waste incineration in China. PCDD/F contents in fly ash and ash deposits vary between 6.9 and 67.3 ng I-TEQ/g. However, the concentration in bottom ash was extremely low (only 1.33?×?10^?3 ng I-TEQ/g). The fingerprints of PCDD/Fs in fly ash are almost similar, except for 2,3,7,8-TCDF. There is no marked correlation between PCDD/Fs and other physicochemical properties.

Supplemental Materials: Supplemental materials are available for this paper. Go to the publisher's online edition of the Journal of the Air & Waste Management Association.     

Dioxins and their fingerprint in size-classified fly ash fractions from municipal solid waste incinerators in China--mechanical grate and fluidized bed units

The distribution of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), in brief dioxins, has seldom been addressed systematically in fly ash from municipal solid waste incinerators (MSWIs). This study shows the amount and fingerprint of PCDD/Fs in fly ash from four different Chinese MSWIs, that is, three mechanical grate units and one circulating fluidized bed unit. In these fly ash samples, dioxins-related parameters (international toxic equivalent quantity, total amount of PCDD/Fs, individual isomer classes, and 17 toxic 2,3,7,8-substituted congeners) all tend to increase with decreasing particle size for mechanical grate incinerators, yet only for the finest fraction for fluidized bed units. Moreover, the fluidized bed incinerator seems superior to grate incineration in controlling dioxins, yet a comparison is hampered by internal differences in the sample, for example, the fluidized bed fly ash has much lower carbon and chlorine contents. In addition, the presence of sulfur from mixing coal as supplemental fuel to the MSW may poison the catalytic steps in dioxins formation and thus suppress the formation of dioxins. With more residual carbon and chlorine in the fly ash, it is easier to form dioxins during cooling. Nevertheless, there is no apparent relation between Fe, Cu, and Zn contents and that of dioxins in fly ash.     

Fate of polychlorinated dibenzo-p-dioxins and dibenzofurans in a fly ash treatment plant

To understand the fate of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in a fly ash treatment plant that used the Waelz rotary kiln process (hereafter the Waelz process), the samples of input and output media were collected and analyzed. The most important PCDD/F source in input mass was electric arc furnace (EAF) fly ash, which had a mean PCDD/F content of 18.51 ng/g and contributed more than 99% of PCDD/F input mass, whereas the PCDD/F input mass fractions contributed by the coke, sand, and ambient air were only 0.04%, 0.02%, and 0.000002%, respectively. For the PCDD/F output mass in the Waelz process, the major total PCDD/F contents of 43.73 and 10.78 ng/g were in bag-filter and cyclone ashes, which accounted for approximately 69% and 17%, respectively, whereas those of stack flue gas and slag were 14% and 0.423%, respectively. The Waelz process has a dechlorination mechanism for higher chlorinated congeners, but it is difficult to decompose the aromatic rings of PCDD/Fs. Therefore, this resulted in the accumulation of lower chlorinated congeners. The output/input ratio of total PCDD/F mass and total PCDD/F international toxicity equivalence (I-TEQ) was 0.62 and 1.19, respectively. Thus, the Waelz process for the depletion effect of total PCDD/F mass was positive but minor, whereas the effect for total PCDD/F I-TEQ was adverse overall.     

Evaluation of the emission characteristics of PCDD/Fs from electric arc furnaces

Distribution of PCDD/F (polychlorinated dibenzo-p-dioxin and polychlorinated dibenzofuran) congeners at two electric arc furnaces (EAFs) in Taiwan is evaluated via intensive stack sampling and analysis. Two kinds of exhaust system in EAFs including stack system and shutter system are selected for measuring dioxin emissions. In addition, dioxin emissions during oxidation and reduction stages at EAF-A were characterized. Results indicate that the PCDD/F concentration of stack gas in EAF-A was 4.39 ng/N m³ while total Toxic Equivalent Quantity (TEQ) concentration was 0.35 ng I-TEQ/N m³. The PCDD/F concentration of stack gas in EAF-B was 2.20 ng/N m³ and the TEQ concentration was 0.14 ng I-TEQ/N m³. 1,2,3,4,6,7,8-H_pCDF, OCDD and OCDF are the major contributors of the dioxin concentrations for two EAFs investigated and the percentage of PCDD/F in particulate phase increases as the chlorination level of the PCDD/F congener increases. The results obtained on gas/particulate partitioning of PCDD/Fs in flue gases prior to the APCD in EAFs indicate that more than 90% exists in particulate phase. In EAF-A, the PCDD/F concentration during oxidation stage is slightly higher than that measured during reduction stage, including the sampling points of CO converter outlet, prior to bag filter and stack. Majority of PCDD/Fs emitted from steel-making processes exists in particulate-phase (about 60–70%) at both EAFs investigated.     

Dioxins and their fingerprint in size-classified fly ash fractions from municipal solid waste incinerators in China—Mechanical grate and fluidized bed units

The distribution of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs), in brief dioxins, has seldom been addressed systematically in fly ash from municipal solid waste incinerators (MSWIs). This study shows the amount and fingerprint of PCDD/Fs in fly ash from four different Chinese MSWIs, that is, three mechanical grate units and one circulating fluidized bed unit. In these fly ash samples, dioxins-related parameters (international toxic equivalent quantity, total amount of PCDD/Fs, individual isomer classes, and 17 toxic 2,3,7,8-substituted congeners) all tend to increase with decreasing particle size for mechanical grate incinerators, yet only for the finest fraction for fluidized bed units. Moreover, the fluidized bed incinerator seems superior to grate incineration in controlling dioxins, yet a comparison is hampered by internal differences in the sample, for example, the fluidized bed fly ash has much lower carbon and chlorine contents. In addition, the presence of sulfur from mixing coal as supplemental fuel to the MSW may poison the catalytic steps in dioxins formation and thus suppress the formation of dioxins. With more residual carbon and chlorine in the fly ash, it is easier to form dioxins during cooling. Nevertheless, there is no apparent relation between Fe, Cu, and Zn contents and that of dioxins in fly ash.

Implications This paper is of interest because it presents the amounts and distribution of PCDD/Fs in fly ash samples from some typical waste incineration plants in China, featuring distinct incinerator types, combustion conditions, fuel composition, or residual carbon, chloride, and heavy metal contents in fly ash.     

Distribution patterns of PCDD/Fs in chlorinated chemicals

The purpose of this research was to determine polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in five chlorinated chemicals (phthalocyanine copper, phthalocyanine green, chloranil-1 and 2, and triclosan), and to compare their 2,3,7,8-tetrachlordibenzo-IpI-dioxin equivalents (TEQ). The distribution patterns of total PCDD/Fs and 2,3,7,8-substituted PCDD/Fs were elucidated in detail. The TEQ values of toxic PCDD/Fs in all chemicals were in the range of 5.03-1379.55 ng I-TEQ/kg. The contribution of OCDD and OCDF in phthalocyanine green was 75% of the total TEQ. For chloranils, the maximum contribution of toxic PCDD/Fs was from 2,3,7,8-substituted HxCDF and 2,3,7,8-substituted HpCDF. The TEQ of HxCDF and HpCDF in chloranil-1 was 90% and in chloranil-2 was 71%. And the toxic contribution increased with the degree of chlorination for PCDFs.     

PCDD/Fs levels in indoor environments and blood of workers of three municipal waste incinerators in Taiwan

This study monitored ambient air concentrations of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in three municipal waste incineration plants. Blood PCDD/Fs levels of 133 workers randomly selected from these plants were also measured. The associations between workers' blood PCDD/Fs concentrations and occupational exposures to PCDD/Fs were assessed. Means of air PCDD/Fs levels ranged from 0.08 to 3.01 pg/m3 in international toxic equivalents (I-TEQ). The geometric means of blood PCDD/Fs concentrations were 14.6, 15.8, 19.1 pg/g lipid in World Health Organization (WHO) TEQ, respectively, for workers from three plants. Air levels of total I-TEQ and all congeners, except 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (TeCDD) and 1,2,3,4,7,8,9-heptachlorinated dibenzofuran (HpCDF), were significantly higher in plant B. However, blood concentrations of 2,3,7,8-TeCDD, 1,2,3,7,8-PeCDD, 2,3,7,8-TeCDF, 1,2,3,7,8-PeCDF and 1,2,3,4,7,8,9-HpCDF were significantly elevated in plant C workers. Although job contents, duration of employment and time spent in certain location were significantly different among incineration plants, they were not significantly associated with blood concentrations of any congener. Furthermore, results of the multiple regression analysis that assessed important occupational factors simultaneously and adjusted for potential confounders, showed significant associations between four congeners and incineration plant or job contents. However, the results were limited by small R-squares of the regression models. In conclusion, blood concentrations of several PCDD/Fs congeners were significantly different among three incineration plants. The differences were not explained by the discrepancy in job contents, duration of employment, and time activity in these plants.     

Fate of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans in a Fly Ash Treatment Plant

Abstract

To understand the fate of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in a fly ash treatment plant that used the Waelz rotary kiln process (hereafter the Waelz process), the samples of input and output media were collected and analyzed. The most important PCDD/F source in input mass was electric arc furnace (EAF) fly ash, which had a mean PCDD/F content of 18.51 ng/g and contributed more than 99% of PCDD/F input mass, whereas the PCDD/F input mass fractions contributed by the coke, sand, and ambient air were only 0.04%, 0.02%, and 0.000002%, respectively. For the PCDD/F output mass in the Waelz process, the major total PCDD/F contents of 43.73 and 10.78 ng/g were in bag-filter and cyclone ashes, which accounted for approximately 69% and 17%, respectively, whereas those of stack flue gas and slag were 14% and 0.423%, respectively. The Waelz process has a dechlorination mechanism for higher chlorinated congeners, but it is difficult to decompose the aromatic rings of PCDD/Fs. Therefore, this resulted in the accumulation of lower chlorinated congeners. The output/input ratio of total PCDD/F mass and total PCDD/F international toxicity equivalence (I-TEQ) was 0.62 and 1.19, respectively. Thus, the Waelz process for the depletion effect of total PCDD/F mass was positive but minor, whereas the effect for total PCDD/F I-TEQ was adverse overall.     

Estimation and characterization of unintentionally produced persistent organic pollutant emission from converter steelmaking processes

Unintentionally produced persistent organic pollutants (UP-POPs) including polychlorinated dibenzo-p-dioxins, and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs) were characterized and quantified in stack gas and fly ash from the second ventilation systems in five typical converters in five different steelmaking plants. The 2378-substituted PCDD/Fs (2378-PCDD/Fs) and dioxin-like PCB (dl-PCBs) toxic equivalents (TEQs) were 1.84–10.3 pg WHO-TEQ Nm^?3 in the stack gas and 5.59–87.6 pg WHO-TEQ g^?1 in the fly ash, and the PCN TEQs were 0.06–0.56 pg TEQ Nm^?3 in the stack gas and 0.03–0.08 pg TEQ g^?1 in the fly ash. The concentrations of UP-POPs in the present study were generally lower than those in other metallurgical processes, such as electric arc furnaces, iron ore sintering, and secondary metallurgical processes. Adding scrap metal might increase UP-POP emissions, indicating that raw material composition was a key influence on emissions. HxCDF, HpCDF, OCDF, HpCDD, and OCDD were the dominant PCDD/Fs in the stack gas and fly ash. TeCB and PeCB were dominant in the stack gas, but HxCB provided more to the total PCB concentrations in the fly ash. The lower chlorinated PCNs were dominant in all of the samples. The 2378-PCDD/F, dl-PCB, and PCN emission factors in stack gases from the steelmaking converter processes (per ton of steel produced) were 1.88–2.89, 0.14–0.76_, and 229–759 μg t^?1, respectively.