医疗废物组分及氯含量对PCDD/Fs分布特性的影响

为了研究医疗废物组分、氯含量对PCDD/Fs(polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans)分布特性的影响,对单组分、双组分及不同氯含量的医疗废物进行了热解-焚烧试验。通过对PCDD/Fs的分布特性分析,发现不同氯含量塑料生成PCDD/Fs的能力与氯代水平都有所不同。纤维对PVC焚烧生成PCDD/Fs有促进作用,并使其氯代水平有所提高,且对于不同PVC,这种作用有所不同。随着氯含量的增大,六、七、八氯代呋喃的产量呈增大趋势,二口恶英产量变化与氯含量的关联不是很明显,但当氯含量增大到1.73%时,其产量明显提高。相同氯含量不同PVC氯源的医疗废物其生成的PCDD/Fs特性不同。     

热重-红外联用分析垃圾衍生燃料的热解特性

利用热重红外分析仪(TG-FTIR)研究了两种不同垃圾衍生燃料(RDF)的热解特性。研究发现,尽管两种RDF的来源不同,但却具有相似的热解特性,其热解过程主要分为3个阶段:生物质组分(220～430℃)、塑料类物质(430～520℃)以及无机碳酸盐(>650℃)的分解。利用Coats-Redfern法,求得了RDF热解前两个阶段的表观动力学参数,计算结果表明高温段的反应活化能要高于低温段。通过FTIR对RDF热解析出的气体进行了在线分析,发现两种RDF热解过程中的气相产物析出规律基本一致,析出的气体主要包括H₂O、CO₂、CO以及CH₄等烃类。HCl在低温阶段(230～400℃)即析出完毕。相比之下,NH₃开始析出的温度较高(260℃),并且整个析出温度范围较广,高温下仍有少量析出。SO₂在热解条件下仍有相当量的生成,其析出主要集中在300～600℃的温度范围内。     

二次反应最小条件下聚氯乙烯塑料脱氯过程的实验

采用金属网反应器对PVC热解过程中温度范围300～800℃、升温速率1～1000 K·s^-1、停留时间0～120 s的热解气体释放特性开展了实验研究.并基于EPA-26A标准对热解气中HCl和Cl₂进行了检测.结果显示,HCl和Cl₂的产率均随着温度的升高、停留时间的增长而有所提高.降低升温速率能够提升气态产物总体产率但没有改变含氯气体的总体分布.热解实验中气态产物均以HCl为主,并伴随有少量的Cl₂生成;该结果也证实了在PVC热解脱氯过程中大量含氯自由基的存在,进一步证实了PVC热解过程遵循的是自由基链反应机理.此外,通过对PVC热解焦样的分析进一步发现PVC热解第一阶段链反应终止时的分子更接近于直链多烯烃结构而非聚合环状结构,环化反应在该阶段并未发生.     

橄榄废弃物低温热解过程中氯的析出规律

生物质直燃是生物质能利用的主要方式,而含氯化合物的释放则影响了生物质锅炉的结渣与腐蚀。低温热解作为一种有效的预处理手段可以解决由氯化物导致的锅炉结渣、腐蚀问题。利用水平管式炉试验系统,测量了不同热解温度下橄榄废弃物HCl、CH₃Cl等含氯物质的释放情况,分析了不同热解温度下上述污染物的释放规律。通过分析发现：HCl和CH₃Cl是生物质热解过程中氯的主要析出产物,热解温度的升高有助于氯等元素分别向HCl和CH₃Cl的转化,低温热解条件下氯的释放主要以CH₃Cl为主,随着温度的升高,二者的差距逐渐减小,当温度达到400℃时,HCl取代CH₃Cl成为生物质热解过程中主要的含氯气态产物。     

城市生活垃圾热处理中氯元素转化的热力学平衡分析

利用FactSage软件,采用热力学平衡分析法,研究了燃烧气氛、反应温度及脱氯剂对城市生活垃圾热处理过程中氯元素转化的影响。结果表明,MSW在空气或富氧气氛下焚烧,低温时氯元素的主要产物为Cl_2和HCl,超过一定温度后,全部转化成HCl,这一温度节点会随着垃圾的具体组分不同而变化;富氧下,O_2含量越高,Cl_2越多,而HCl越少;而在全实验温度范围内热解,氯元素几乎全部转化为HCl。超过一定温度(不同工况下400～800℃)时,脱氯剂丧失脱氯效果。脱氯剂的效果:CaO>CaCO_3,添加比例15%>10%>5%,热解>空气>富氧气氛(富氧时CO_2与脱氯剂生成CaCO_3,O_2含量越少脱氯效果越好)。脱氯效果与垃圾组分有关,因MSW样本2中含大量硫元素,硫元素氧化生成CaSO_4,抑制脱氯效果,故MSW样本1脱氯效果优于MSW样本2,适宜脱氯温度范围较广。     

高硫煤泥燃烧过程中的汞排放特性

通过固定床程序升温汞脱附试验系统对所选高硫煤泥中汞排放特性进行在线监测,并利用热重分析仪对煤泥热解和燃烧特性进行研究,结合试验所得热解和燃烧特性参数,采用分布活化能模型,进行动力学分析。结果表明：煤泥的热解和燃烧过程可分为3个阶段,非等温条件下,随着升温速率增加,热解过程在高温区发生,最大失重率提升,对应峰值温度偏移,产生热滞后,利于挥发分析出;在煤泥热解过程中少量氧气的参与,抑制挥发分的析出,在7% O₂条件下综合热解特性参数值D最大。热解性能随CO₂浓度升高而得到改善;煤泥燃烧性能随升温速率的增加而得到加强,其活化能随转化率变化呈现“U”型趋势分布;煤泥中无机汞化合物主要为HgCl₂、α-HgS、HgSO₄以及硅铝酸盐类结合汞,总汞释放主要范围对应200~600℃;煤泥中汞释放量随O₂浓度增大,CO₂气氛条件下,随着CO₂浓度增加,总汞释放量逐渐增大。     

Fe2O3对甘氨酸热解特性及氮转化的影响

选用污泥中典型氨基酸-甘氨酸（Gly）为研究对象,利用差式热值分析-质谱联用技术（DSC-MS）和固定床实验研究了Fe₂O₃对甘氨酸热解特性、NO _x 前驱物生成规律以及氮转化特性的影响。结果表明：热解特性实验中,由于Fe₂O₃将Gly的第一热失重阶段一分为二,导致其热解过程由2个阶段增至3个;Fe₂O₃使Gly热解起始温度及气体析出温度降低50℃,并通过促进半焦的二次裂解反应使Gly失重率增加23%。与Fe₂O₃对Gly热解过程的影响一致,Fe₂O₃将含N气体析出过程同样分成3个独立的阶段。固定床实验中,在Fe₂O₃/N=0.5时,Fe₂O₃最大程度地抑制了NO _x 前驱物（NH₃和HCN）析出,使其减少30%。由于Fe₂O₃促进肽脱水缩合、环化和芳香化反应,使得更多P-N、N-5和N-6固定在半焦中,半焦氮残留率增加5%。     

医疗废弃物典型组分热解过程中产气特性的实验研究

为掌握医疗废弃物的热解特性,在管式炉中对医疗废弃物典型有机组分进行热解实验研究,并用在线气体分析仪监测物料主要热解气体成分及其含量的变化,得到了物料产气过程和产气成分随温度的变化规律。研究结果表明,物料特性、热解终温对气体产物的生成过程和分布影响较大。与纤维素类的脱脂棉和竹子相比,聚丙烯的分解反应起始温度明显较高。提高热解温度会提高气体析出峰值和产量,以及热解气中可燃气体的比重。     

生物质三组分二元混合热解特性研究

采用TG-FTIR-MS研究了生物质三组分二元混合热解过程的失重特性和小分子气体逸出规律。结果表明二元混合组分热解过程降低了热解反应开始温度。纤维素与半纤维素混合热解过程热解反应受到抑制,热解失重率降低,H₂、CH₄和H₂O产量减小,CO和CO₂产量增加。木质素和半纤维素在混合热解过程中存在协同效应,促进热解反应进行,H₂产量增加,然而其他小分子气体产物的生成被抑制,协同效应的效果更有利于可冷凝挥发分产物生成,这种效应随着半纤维素比例增大而减弱。半纤维素和纤维素在整个热解过程表现出相互抑制的效果,其小分子气体产物产量减小,但随着纤维素比例增大,影响减弱。     

氯化镁中试热解炉热工过程数值计算研究

为了探究MgCl₂喷雾热解工艺中的核心设备热解炉内的复杂热过程，提高工艺产品质量和设备使用寿命，采用欧拉-拉格朗日方法建立了气固两相流传热与热解反应耦合的数学模型，研究了热解炉稳定运行时的温度场、颗粒分解过程和HCl分布情况，并探讨了进口气体温度和流量对MgO转化率和HCl分布的影响。结果表明，在研究范围内，随着进口烟气温度和流量的增加，产品转化率逐渐提高。当烟气入口流量为1.5 m³/s、入口温度为1 423 K时和烟气入口温度为1 273 K、入口流量为2.25 m³/s时，产品转化率均达到100%。随着颗粒向下运动，HCl浓度逐渐增大，在出料口处HCl达到最大质量分数为6.5%。此外，随着进口烟气温度和流量的增加，出料口处的HCl浓度呈现先增后减的变化规律。对应HCl浓度最大值时的进口烟气温度和流量分别为1 373 K和1.75 m³/s。     

含氯废弃物燃烧过程中HCl排放特性

引　言生活垃圾中含有的有机氯主要以PVC塑料的形式存在 ,我国塑料制品中PVC占 30 %以上 ;无机氯通常以NaCl的形式存在于厨余中 ,单独焚烧厨余物 (主要含无机氯化物 )会导致大部分氯化物转化为HCl[1] .郭小汾等[2 ] 研究了PVC的燃烧特性和HCl的析出机理 ,认为PVC的燃烧过程分为     

Formations and controls of HCl and PAHs by different additives during waste incineration

This study employed a laboratory-scale fluidized bed incinerator to investigate the formations and controls of hydrogen chloride (HCl) and polycyclic aromatic hydrocarbons (PAHs) by adding different additives in the feedstock during waste incineration. The effects of different organic and inorganic chlorides on the formation and control of HCl and PAHs were also studied. Additionally, the thermodynamic equilibrium modeling was also carried out to interpret and compare with the experimental results.Experimental results showed that the formation of HCl was related to the potential of chlorine released from the combustion of different chlorides. Organic chloride PVC had greater potential to form HCl than inorganic chloride NaCl. The performances of additives were affected by incineration temperature. Increasing temperature decreased the control efficiency of additives because the emission yields of HCl and Cl₂ were increased with temperature. The control efficiencies for HCl and Cl₂ by calcium based additives (Ca(OH)₂, CaO, CaCO₃) were better than that by magnesium based additive (Mg(OH)₂) and CaO was the best additive. The control efficiencies of PAHs by adding CaO in the feedstock were not apparent because the fluidization quality in the fluidized bed incinerator was decreased.     

Fate of the chlorine and fluorine in a sub-bituminous coal during pyrolysis and gasification

The fate of the chlorine and fluorine present in a sub-bituminous coal from Indonesia during pyrolysis and gasification has been studied with fixed and entrained bed reactors. The rate profile for HCl evolved in the temperature programmed pyrolysis exhibits the main and shoulder peaks at 480 and 600 °C, respectively. Model experiments and subsequent Cl 2p XPS measurements show that HCl reacts with metal impurities and carbon active sites at 500 °C to be retained as inorganic and organic chlorine forms, from which HCl evolves again at elevated temperatures. It is suggested that the HCl observed in the coal pyrolysis may originate from the above-mentioned chlorine functionalities formed by secondary reactions involving the nascent char. In the CO₂ gasification of the 900 °C char at 1000 °C and 2.5 MPa, any measurable amounts of HCl and HF could not be detected even at a high conversion of 75 wt% (daf), suggesting the accumulation of these halogens in the residual char. When the coal is injected into an O₂-blown, entrained bed gasifier at 1200-1400 °C under 2.6 MPa, the partial oxidation proceeds to a larger extent at a higher O₂/coal ratio, whereas the chlorine and fluorine are enriched in the remaining char, and the extent of the enrichment at the latter stage of gasification is larger with the fluorine. The XPS measurements of the chars reveal the presence of the broad F 1 s peak, which can cover a wide range of binding energies attributable to inorganic and organic fluorine. The halogen enrichment during gasification is discussed in terms of secondary reactions of HCl and HF with char.     

HCl emission during co-pyrolysis of demolition wood with a small amount of PVC film and the effect of wood constituents on HCl emission reduction

In this study, HCl emission during the co-pyrolysis of demolition wood and a small amount of polyvinyl chloride (PVC) film (the Cl content of which ranged from 0.5% to 6% by weight) in an N₂ atmosphere at elevated temperatures of up to 600 °C was measured using a laboratory-scale cylindrical batch reactor. In the pyrolysis experiments, HCl emission was reduced by the presence of wood. The effect of the primary constituents of wood (cellulose, hemicellulose, and lignin) on HCl emission was investigated by not only measuring HCl emission and Cl distribution to various phases during the co-pyrolysis of each constituent with PVC film but also by conducting thermogravimetric analysis of the constituents. This investigation first revealed that hemicellulose significantly reduced HCl emission by fixing most of the Cl molecules in a sample into pyrolyzed residue.     

Poly(ethylene glycol)–polyhedral oligomeric silsesquioxane as a novel plasticizer and thermal stabilizer for poly(vinyl chloride) nanocomposites

The plasticizing and thermostabilizing effect of poly(ethylene glycol)–polyhedral oligomeric silsesquioxane (PEG‐POSS) on poly(vinyl chloride) (PVC) is discussed thoroughly in this work. As PEG‐POSS content increases, PVC becomes more flexible and the decomposition temperature of PVC increases slightly. Meanwhile, the temperature of maximum HCl emission is elevated from 265.3 °C in neat PVC to 285.7 °C in PVC nanocomposites, with the peak intensity of HCl emission decreased by 30.8%, and a new lower intensity of HCl emission peak appearing at much higher temperature (around 370 °C), which is in accordance with the maximum degradation temperature of PEG‐POSS. Thereby, a possible dehydrochlorination mechanism is suggested according to the fact that the electron donor effect of ether groups would stabilize the C? Cl bonds by means of more electron cloud stacked in those bonds, which agrees with Fourier transform infrared and X‐ray photoelectron spectroscopy experiments in terms of hydrogen bonds. © 2016 Society of Chemical Industry     

煤与PVC共热解固体产物在燃烧中氯的释放特性

通过实验研究了煤与PVC共热解固体产物燃烧时氯的释放特性,结果表明,氯的释放量（率）与燃烧温度、煤与PVC共热解的温度以及共热解时PVC的加入量有关．燃烧温度越高,氯的释放率越大,900℃燃烧时,氯的释放率都在94％以上;热解温度越高。在同一温度燃烧时,氯的释放率越低．400℃时焦中氯的最高释放率达99．86％,而1000℃时焦中氯的最高释放率为94．35％．     

HCl催化氧化制氯气工艺过程

通过对HCl氧化制Cl2的Deacon过程的热力学和动力学分析以及实验研究,得到了HCl催化氧化制Cl2过程的优化工艺条件,即进料HCl/O2摩尔比为4、HCl质量空速为0.45 h-1、反应温度为450℃、常压,在此条件下HCl和O2的转化率均为65%,产物中Cl2干基含量为78.8%,O2干基含量为21.2%.     

The volatilization behavior of chlorine in coal during its pyrolysis and CO2-gasification in a fluidized bed reactor

The volatilization behavior of chlorine in three Chinese bituminous coals during pyrolysis and CO₂-gasification in a fluidized bed reactor was investigated. The modes of occurrence of chlorine in raw coals and their char samples were determined using sequential chemical extraction method. The Cl volatility increases with increasing temperature. Below 600 °C the Cl volatility is different, depending on the coal type and the occurrence mode of Cl. Above 700 °C, the Cl volatilities for the three coals tested are all higher than 80%. About 41% of the chlorine in Lu-an coal and 73% of that in Yanzhou coal are organic forms, and most of them are covalently-bonded organic chlorine, which shows high volatile behavior even at low pyrolysis temperatures (below 500 °C), while the inorganic forms of chlorine in two coal samples are hardly volatilized even at low pyrolysis temperatures (below 400 °C). The restraining efficiency of addition of CaO on chlorine volatility is greatly dependent on pyrolysis temperature. The optimal restraining efficiency can be obtained at temperature range from 450 to 650 °C during pyrolysis of Lu-an coal. The volatile behavior of Cl is mainly dependent on temperature. Above 700 °C high volatility of Cl is obtained in both N₂ and CO₂ atmospheres.