城市污水污泥与固体垃圾混烧过程中重金属迁移特性的研究

通过城市污水污泥与固体垃圾合成样品在小型管式焚烧炉内的混烧实验,采集灰渣样品进行XRF化学成分分析和浸出毒性鉴别测试,结合污水污泥焚烧过程中热力学平衡计算,定量表征了污水污泥中Cu、Pb、Zn、 Mn、Ni在焚烧过程中向底灰、飞灰和烟气迁移的特性及对灰渣的毒性影响。研究结果表明,污水污泥混烧显著提高了飞灰和底灰中重金属含量,其中Zn和Pb增加量最大,而Ni、Mn、Cu依次减少;随着有机氯的加入,飞灰中重金属含量呈现递增趋势,其中Zn表现最明显。毒性测试结果显示,污水污泥的混烧也导致了垃圾焚烧飞灰中Zn和Pb的浸出浓度超过中国对危险废物浸出的控制标准值。同时,重金属迁移的热力学平衡模型预测结果与实验结果差距较大。这表明热力学平衡计算方法还需进一步考虑影响重金属氯化物形成的其他因素,如在焚烧过程中反应动力学、焚烧室内氧气含量变化、与其他元素间的化学反应等。     

污泥化学链燃烧过程中氮迁移转化特性研究

在单流化床反应器上探究了污泥化学链燃烧过程中氮迁移转化特性。由于赤铁矿载氧体反应活性低,采用30%水泥对其改性。结果表明,水泥改性可提高污泥热解气化反应速率以及赤铁矿还原反应速率,进而提高污泥碳转化率,但是NO生成率也增加。随着反应温度的升高,污泥的碳转化率和NO生成率均增加。另外,随着水蒸气浓度的增加,碳转化率增加,同时可降低NO生成。在污泥化学链燃烧过程中,NO生成率为0.286%-0.768%,低于污泥空气焚烧氮氧化物排放量。     

基于水泥修饰的赤铁矿载氧体污泥化学链燃烧特性研究

采用水泥修饰赤铁矿来提高载氧体的反应活性。实验在1kW_th串行流化床上进行,研究了添加水泥对污泥化学链燃烧特性的影响,考察其长期运行的物化性能。结果表明,在实验工况下,赤铁矿添加水泥后,出口的未燃气体浓度明显下降。燃料反应器温度低于870℃时,水泥的添加使污泥的碳转化率和燃烧效率显著升高。在10h长期运行后,一部分污泥灰沉积在载氧体表面。虽然在反应过程中部分的Fe₂O₃被深度还原,但在长期运行中未出现流化问题和烧结现象。     

一种煤与两种城市污水污泥混合热解的热重分析

采用热重分析法对一种煤和两种城市污水污泥（S1和S2）及其混合物进行了热解实验研究,揭示了煤和污泥在氮气中的热解特性及污泥对煤热解特性的影响。煤和污泥的热解特性参数不同,主要表现在总失重率、失重速率及挥发分析出温度区间等。煤与污泥S1混合有助于增加样品的热解总失重率,提高失重速率;污泥S1与煤的挥发分析出区间部分重合,污泥灰中含的无机物对煤的热解起到催化效果;煤和S2污泥混合后热解反应过程中无明显相互作用;煤与城市污水污泥混合物的相互作用与样品特性和混合比例有关。     

磷对泥/煤混燃灰熔融特性的影响及矿物相演变规律

采用灰熔点仪、X射线荧光仪(XRF)研究了无机非金属P2O5对城市污水污泥与烟煤的混烧灰熔融特性的影响,利用X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)研究在各混烧温度下灰中含磷矿物在晶体和非晶体间的演变。结果表明,对于Al_2O_3含量较多且熔点较高的灰样,磷含量的增加可显著降低其灰熔点,P2O5含量在0-4%时影响最大,使其灰熔点降低126℃;但对碱性含量高的灰样的影响较小。低温灰中主要以磷酸铝(AlPO_4)晶体为主,温度升高后,与硬石膏(CaSO_4)等含钙矿物和赤铁矿(Fe_2O_3)反应生成晶体Ca_3(PO_4)_2和玻璃相(Fe_2O_3)_(0.252)(P_2O_5)_(0.748),磷含量增加可使灰中玻璃相(Fe_2O_3)_(0.252)(P_2O_5)_(0.748)增加,是磷降低灰熔点的主要原因。     

微波消解-磷钼蓝分光光度法测定城市污泥中总磷浓度

建立了微波消解-磷钼蓝分光光度法测定城市污泥中总磷的方法。在微波环境中硝酸-过氧化氢能够将城市污泥中无机磷盐和含磷有机物消解为正磷酸盐,在弱酸性条件下,正磷酸盐在铋盐的催化条件下与钼酸铵-抗坏血酸生成磷钼蓝,于分光光度计波长690nm处进行测定总磷浓度。方法的相对标准偏差0.63%~0.95%,加标回收率为101%~102%,能够满足对城市污泥中总磷浓度的测定要求。     

污泥与煤共热解过程中磷元素的挥发规律研究

污泥灰分中磷元素含量明显高于煤,其中主要的晶体态含磷化合物为磷酸铁钙和少量的磷酸铝。利用高频加热反应装置考察了污泥-神府煤混合物快速热解过程中磷元素挥发规律。结果表明,污泥-神府煤混合物热解后磷元素主要存在于热解焦中。磷元素挥发比例随污泥添加比例的增加先升高后降低,随热解温度的升高而增加。热解温度不高于1 100 ℃时,混合物中以有机磷的挥发为主,磷元素挥发比例不高于3.2%。热解温度高于1 200 ℃后无机磷中磷元素挥发明显,1 300 ℃下最高有33.0%的磷元素随热解气体挥发出。     

添加不同塑料与污泥混合热解对生物炭中重金属的影响

利用高温管式炉开展城市污泥（SS）与四种塑料（PE、PP、PS和PVC）混合热解实验,分别得到四种生物炭（SSC_PE、SSC_PP、SSC_PS和SSC_PVC）,研究了生物炭中重金属（Cr、Mn、Ni、Cu、Zn、As、Cd和Pb）含量、残余率、BCR形态和TCLP浸出毒性特征,并开展潜在生态风险评估。结果表明,添加不同塑料与污泥混合热解能够降低除Cd以外重金属的残余率。与污泥单独热解所得生物炭（SSC）相比,添加PE、PP和PS能够促进生物炭中的重金属向相对稳定态（F3+F4）转化,实现固化稳定;添加PVC仅对生物炭中Cr和As有固化稳定作用,对其他重金属有明显活化作用。四种生物炭中的重金属浸出量低于GB5085.3-2007浸出毒性鉴别标准规定的限值,生态风险均明显地降低至轻微风险水平,表明添加PE、PP、PS和PVC与污泥混合热解所得生物炭的应用不会带来新的环境风险,这为污泥与废塑料协同处置工艺提供了良好的理论支撑。     

污水处理工艺对污泥热处理特性的影响

通过10℃/min时的热重分析,对五种不同性质污泥分别在氮气和氧气气氛下的热解和燃烧特性进行了研究。结果表明,污水处理工艺的“好氧+厌氧”、“厌氧+好氧”过程以及污泥的厌氧消化均使污泥中的有机物结构复杂,导致污泥热解时有机物的分解和析出温度升高,且“好氧+厌氧”过程使污泥中有机物结构更复杂;而对污泥的燃烧过程和燃尽点无影响,但使着火温度升高。利用šatava-šesták 方程对污泥热解、燃烧的反应机理进行了研究。结果表明,五种污泥热解时均呈现为挥发分扩散和随后的化学反应机理函数,而燃烧时则为化学反应和随后的扩散过程。     

污泥与煤和煤矸石共燃特性研究

利用STA 409 PC型同步热分析仪,对煤、煤矸石和污泥不同质量比样品的燃烧过程进行了热重分析。结果表明,单一煤和煤矸石的DTG曲线都只有一个明显的失重峰,污泥的DTG曲线有两个明显的失重峰,而混合物的DTG曲线都有两个失重峰。通过分析不同样品的混燃过程,发现随着煤所占质量比的增加,最大失重峰速率所对应的温度都有所降低。煤、煤矸石、污泥及其混合物的活化能为16.93kJ/mol～109.89kJ/mol。随着污泥所占质量比的增加,混合物的着火温度有所降低,当达到70%时,污泥与煤混合物的着火点接近单一污泥的着火点。     

污泥微波高温热解条件下富氢气体生成特性研究

分别采用单模微波炉和电加热管式炉对污泥热解过程进行了实验研究,分析了污泥粒径、含水率、热解温度和微波吸收剂形态等参数对热解产物分布特性和气体组分浓度的影响规律和机理。结果表明,在粒径0~5.00 mm,污泥粒径大小对污泥微波热解产物分布无明显影响,但粒径减小可以提高H₂和CO浓度,当粒径从2.50~5.00 mm减小至小于0.45 mm,H₂和CO体积分数分别从31%和17%上升至34%和22%;污泥含水率和微波热解温度对热解产物分布和热解气组分浓度分布都有显著影响,提高污泥含水率或微波热解温度都可以显著提高H₂和CO浓度,当污泥含水率从0上升至83%,H₂和CO体积分数分别从32%和20%上升至42%和31%;相比粉末态吸波剂,固定形态的微波吸收器可以提高挥发分向热解气的转化,提高热解气产量,同时还能略微提高H₂和CO产率,但效果并不明显。     

TG-MS as a technique for a better monitoring of the pyrolysis,gasification and combustion of two kinds of sewage sludge

Sewage sludge disposal is a difficult task owing to increasingly restrictive re-use policies. Its final destination will obviously depend on its nature and composition but the generation of energy is a significant option. The thermochemical conversion requires exhaustive gas emission controls. In this regard, this paper offers the results of the use of mass spectrometry together with a thermogravimetric analysis system used to study the thermal conversion processes of two kinds of sewage sludge under different atmospheres simulating pyrolysis, gasification and combustion. This TG-MS combination indicates that gasification is the best process for one kind of sludge while a co-combustion process is more suitable for the other. This revised version was published online in July 2006 with corrections to the Cover Date.     

生活垃圾流化床热处置中重金属迁移分布研究

在流化床实验装置上研究模拟生活垃圾热解、气化、焚烧等热处置过程中重金属Cd、Pb、Zn及Cu的迁移转化,分析氧化还原气氛及温度对重金属挥发特性的影响。结果表明,高温及还原性条件促进了Cd、Pb及Zn的挥发;而氧化性气氛有利于Cu的迁移。热力学平衡模拟结果表明,金属在氧化和还原气氛下的转化途径不同。在还原性气氛下,金属主要以元素态单质或硫化物的形式存在,其熔沸点高低决定了金属挥发程度。反之,CuCl_3等氯化物的生成促进了Cu在氧化性气氛下的挥发。金属基反应在氧化性气氛下得到加强,提高了Cd、Pb及Zn向气相产物转化的起始温度。进一步考察重金属在不同组分的分布及富集规律,大部分以气相形式挥发的重金属易在降温过程中冷凝并富集于飞灰。气流夹带亦是导致重金属迁移的重要原因,流化床的高气速特性对重金属分布有显著影响。     

Simultaneous determination of Cd,Cr, Cu,Ni, Pb and Zn in sewage sludge by slurry introduction ICP-OES method

In order to evaluate the slurry nebulisation method as an alternative method for analysis of sewage sludge, the metal content of sludge samples of different origins was determined. The concentrations of six elements: Cd, Cr, Cu, Ni, Pb, and Zn were determined by introducing the sludge as a slurry into an inductively coupled plasma optical emission spectrometer (ICP-OES). Calibration was performed by using aqueous standard solutions. For comparison, the sewage sludge was also digested by microwave digestion and introduced into the plasma as an aqueous solution. The accuracy of the method was checked by analysing a sewage sludge certified reference material (CRM 007-040 Sewage Sludge). The Student's t-test showed that values obtained using slurry nebulisation were close to the certified values at a 95% confidence level. The values of elements Cd 11.1?±?0.8; Cr 37.7?±?3.3; Cu 563.3?±?38.4; Pb 119.2?±?10.1; Zn 729?±?68.2?mg?kg^?1 obtained using this method were comparable with those obtained using the conventional method. The slurry method can, therefore, be successfully applied to the determination of content of each element in sewage sludge with RSD less than 3%, without the need to predissolve them. This could avoid the use of hazardous chemicals, incomplete dissolution and loss of volatile analytes.     

DTG-DTA study of sewage sludge used in the sorption of Cd2+ and Co2+

The present study was carried out for evaluating the retention behavior of sanitary sewage in relation to cadmium and cobalt ions in an ascendant continuous-flow reactor. It was found that the studied sludge presented a high assimilation of the metals, probably due to the presence of anionic groups, which favors adsorption and complexation processes. Thermal analyses of the samples showed a shift in the thermal decomposition of the ‘in natura’ sludge, when compared with those of the samples spiked with the metals, confirming the possibility of interactions between the heavy metals and the anionic groups present in the sludge.     

改性污泥与无烟煤成浆性的研究

采用阴离子表面活性剂萘磺酸钠甲醛缩合物、聚羧酸钠作为分散剂,考察了不同污泥用量时污泥煤浆的成浆性能。结果表明,当污泥(干基)添加量为煤质量的4%时,成浆浓度超过60%,随着污泥用量的提高,污泥煤浆的成浆浓度降低。污泥加入后,浆体的稳定性增强,污泥比例越高,产生沉淀的时间延长。当污泥(干基)添加量为煤质量的4%时,产生沉淀的时间超过160h,与使用稳定剂效果相当。使用不同添加剂制备的污泥煤浆均呈假塑性。污泥疏松的絮状结构,蜂窝状的外表面,强大的吸水性是造成污泥煤浆成浆浓度下降,稳定性增加的主要原因。     

Thermal decomposition study of sewage sludge and of organicwaste used in the sorption of metals

The conventional treatments of effluents containing heavy metals produce significant quantities of byproducts with recalcitrant characteristics, making necessary looking after alternative techniques in order to avoid the production of new contaminated residues. Sorption process of chromium and zinc in vertical columns loaded with sewage sludge and organic solid waste has been studied in this work. The data from the TG curves of the two sorbents presented significant differences when they were submitted to the metal uptake, being noticed the displacement of the thermal events towards lower temperatures for both types of sorbents studied. As it was expected, for both sorbents, an increase in the mass of samples has been observed at the completion of the thermal tests upon metal uptake. Therefore, these facts demonstrate that during the biosorption process a physico-chemical interaction took place between sorbents and metals, as it was evidenced by the more than 100 K increase in the decomposition temperatures as well as the variation of the ΔH values of the samples.     

Treatment of sewage sludge generated in municipal wastewater treatment plants

This study was designed to evaluate the performance of a cylindrical anaerobic digester in treating secondary sewage sludge. A series of three independent batch experiments was performed for a total operation time of 60 d. The system of anaerobic digestion showed stability conditions, with no noticeable scum or foaming problems. The chemical oxygen demand reduction reached 29, 21, and 45% in sludge and 95, 85, and 82% in supernatant for the three experiments, respectively. Total coliform bacteria levels in the digester ranged from 10⁴ to 10⁵ in influent sludge and from 10⁴ to 10³ in effluent sludge, with an average reduction of 90%. Fecal coliforms of the order of 10⁴ were enumerated in influent sludge and those of the order of 10⁰ were enumerated in effluent sludge, with an average reduction of 99.9%. The studied system had satisfactory results, showing that both organic matter and indicator bacteria levels substantially decrease when the sludge is submitted to anaerobic digestion.     

污泥干燥预处理后与神府煤共成浆性的研究

以萘系阴离子表面活性剂为分散剂,考查了污泥干燥条件和粒径对神府煤成浆性的影响。结果表明,将污泥干燥后再制浆,明显提高了污泥煤浆的成浆浓度;升高干燥温度,有利于提高污泥煤浆的成浆浓度。干燥温度对污泥的可磨性影响较大。干燥温度越高,干燥污泥可磨性越好,球磨的污泥平均粒径越小,制得的污泥煤浆表观黏度越低;温度高于105℃,污泥的可磨性无明显差别,污泥煤浆的表观黏度亦无明显变化。污泥粒径越小,颗粒越细,一定程度上提高了煤粉的堆积效率,使污泥煤浆的表观黏度降低。     

O2/CO2气氛下污泥/煤混燃中半挥发性重金属的释放特性

在固定床焚烧实验装置上,采用正交实验法研究了焚烧温度(t_c)、污泥掺混比(X_s)、O_2体积分数(φ_(O2))、初始含水率(φ_(H2O))、焚烧时间(τ)和含氯量(φ_(Cl))六个因素对O_2/CO_2气氛下污泥/煤混燃中半挥发性重金属(Zn、Pb、Cd、Cu、Ni和Cr)释放特性的影响。结果表明,六种因素对重金属释放率影响程度排序为t_cX_sφ_(H2O)φ_(O2)≈τφ_(Cl)。相同焚烧工况下,Zn释放率最大,Pb和Cd次之,Cu、Ni和Cr较小。提高温度会促进重金属释放,且高温(1000-1100℃)对重金属释放的影响显著强于低温(700-900℃)。随着温度由700℃升高至1100℃,Zn和Pb释放率分别由36.1%和12.2%上升至70.9%和63.5%,Cd在900℃下达到40.0%的最大释放率,而Cu、Ni和Cr释放率大都维持在20.0%以下,温度对重金属释放率影响程度排序为PbZnCdCuCrNi。重金属释放率随着污泥掺混比增加逐渐下降,却随着初始含水率增加呈现波浪式变化趋势,且在30%O_2体积分数下重金属释放率取得最小值。焚烧时间和含氯量对Pb释放的影响程度显著强于其他五种重金属。O_2/CO_2气氛下污泥/煤混燃的最佳工况为:焚烧温度为900-1000℃、污泥掺混比为25%左右、O_2体积分数为30%、初始含水率小于10%,并尽可能的缩短焚烧时间。