Contribution of stack gases and solid process wastes to the organic pollutant output of thermal waste treatment plants

Within the scope of fundamental investigations as well as individual research projects (W. Knorr, B. Hentschel, C. Marb. S. Sch?del, M. Swerev, O. Vierle, J.-P. Lay, 1999. Rückst?nde aus der Müllverbrennung-Chancen für eine stoffliche Verwertung von Aschen und Schlacken. Initiativen zum Umweltschutz, 13 ed., Deutsche Bundesstiftung Ulmwelt, Erich Schmidt, Berlin), the Bavarian State Office for Environmental Protection performs emission measurements at thermal waste treatment plants to optimize operation, to accompany and support development of new technologies, and to study the effect of this kind of waste treatment technology on the environment. Based on recent studies (October 1995-July 1999) at six municipal solid waste incinerators (MSWI) in Bavaria all emission streams (solid and gas) are characterized with respect to organic pollutant contents and compared to the emissions of waste pyrolysis. The significant ranges of pollutant concentration as well as the specific congener patterns observed are similar for all MSWI, regardless of differences in technical design and waste input, but differ markedly from those of the pyrolysis products. The overall approach, including the sampling of all output streams and the determination of mass streams and volume flow rates, allows the calculation of the total output of different organic pollutants for waste incineration plants aand to estimate the relative contribution of each of the emission streams to the total pollutant load. Removal efficiencies are also calculated for the air pollution control (APC) systems of the different MSWI plants.     

Narrow stack emissions: Errors in flow rate measurement due to disturbances and swirl

ABSTRACT

European legislation continues to drive down emission limit values, making the emission measurement of narrow stacks of increasing importance. However, the applicable standards (EN ISO 16911–1 and EN 15259) are poorly validated for narrow stacks, and the effect of flow disturbances on the described methods are largely unknown. In this article, measurement errors are investigated in narrow stacks with flow disturbances and swirl, both experimentally and through computational fluid dynamics (CFD) simulations. The results indicate that measurement errors due to misalignment of the flow with typical measuring probes (pitot tubes) are small compared to errors resulting from the positioning of these probes in the measurement plane. Errors up to 15% are reported using the standardized methods, while the measurement error is both smaller and more predictable when using additional measurement points.

Implications: Current international standards provide methods to measure emissions from industrial stacks. With increasingly small emission limit values, the accuracy of these measurements is becoming considerably more important. The data from this study can be used to inform revisions of these standards, in particular with respect to flow disturbances in narrow stacks, and can help law- and policy-makers to obtain insight into the uncertainties of emission measurements in these specific situations.     

Chemistry of precipitation at high altitudes: Inter-relation of acid-base components

Data on the chemical composition of atmospheric precipitation for three high altitude WMO stations have been analyzed and critically interpreted using statistics of deposition and various ratio values. The stations are: Monte Cimone, Italy; Mauna Loa, HI, U.S.A.; and Alamosa, CO, U.S.A. The composition is quite variable, both within-station and station-to-station. There is a good correlation between reported alkalinity and Ca content for Monte Cimone. The data analysis suggests that H₂SO₄ is the main cause of “acid rain” at Mauna Loa. Two of the three stations show good association of NH₄⁺ ion with NO₃⁻ ion while the former is not well correlated with SO₄²⁻ ion at any of the stations. On the other hand, simple and multiple correlations indicate that sulfate is strongly related with alkali/alkaline earth elements. Thus, suspended particulate matter may be an important sink for the mass-removal of atmospheric sulfur in the lower troposphere.     

高热值城市生活垃圾归类分流处置的能值分析

生活垃圾处理已成为限制城市化进程和城市经济发展的重大问题之一,采用垃圾归类分流处置方法可以有效地促进垃圾减量化和资源化的效果。以西安市典型高校校园生活垃圾为代表性高热值焚烧型城市生活垃圾,通过绘制能值系统图辨析卫生填埋-沼气发电、焚烧发电、生物质燃料混烧发电等3种垃圾处理系统的能值投入和产出过程。依据垃圾物理组成和热值数据分别计算了2种处理系统的能值产出率、环境负载率、能值投资率、可更新能源投入率和能值可持续指数等5项基本能值指标,并从能量利用的角度对3种生活垃圾处理方法的环境可持续性与经济竞争力进行了比较分析。能值分析结果表明,采用生活垃圾焚烧和生物质燃料混烧发电处理法在能量转化效率和环境影响方面具有显著优势,对高热值焚烧型生活垃圾采用“归类分流-集中焚烧处理”的方式有利于提高城市生活垃圾减量化处理的环境效益与经济收益。     

Dioxin analysis in stack emissions, slags and the wash water circuit during high-temperature incineration of chlorine-containing industrial wastes; Part 2

PCB's and polychlorobenzene sumps have been incinerated in a high-temperature installation. The working conditions, wastes, sampling methods and analysis of the stack emissions, slag and wash water are described. No 2,3,7,8-TCDD and only ppt-traces of some PCDD congeners were detected in the stack emission. The performance criteria of the incinerator and the more important sampling procedures are discussed.     

炉排式垃圾焚烧炉参数敏感性分析与燃用高热值垃圾运行优化的数值模拟

针对垃圾热值提高造成的炉排式垃圾焚烧炉受热面超温问题,采用计算流体力学(CFD)方法模拟焚烧炉内垃圾焚烧过程,并将模拟结果与Morris敏感性分析方法结合,考察一次风温度、过量空气系数、干燥段风量占比和垃圾停留时间4个输入参数改变对垃圾着火位置和下炉膛最高烟气温度2个输出参数的敏感性,以评估各参数对炉内垃圾焚烧的影响,得到更为有效的运行参数调整方案。结果表明,垃圾停留时间是最敏感的控制参数,一次风温度和炉排配风比例也是较敏感的参数。在此基础上,对某1 000 t·d⁻¹焚烧炉燃用高热值垃圾运行优化开展模拟分析发现,缩短垃圾停留时间和调整炉排配风比例使着火点位置接近基准垃圾工况,使烟道前侧壁面附近温度降低93 K;进一步调整后墙二次风入射角至水平,可显著降低进料口壁面附近温度,且烟气温度、氧气和未燃气体的体积分数均满足国家排放标准。本研究结果可为炉排式垃圾焚烧炉燃用高热值垃圾的运行优化提供参考。     

Estimation of direct radiative forcing due to non-methane hydrocarbons

The direct radiative forcing due to non-methane hydrocarbons (NMHCs) has not previously been quantified. We use new measurements of infrared absorption cross-sections and a narrow band radiative transfer model to estimate a forcing. An upper limit to the global mean anthropogenic forcing is likely to be in the region of 0.015 W m^-2, less than 1% of the forcing due to other greenhouse gases. However, taking account of the natural NMHC loading and the vertical profile of these gases the actual radiative forcing is likely to be somewhat less than this.     

Emission characteristics for co-combustion of leather wastes,sewage sludge,and coal in a laboratory-scale entrained flow tube furnace

Four different mixed fuels consisted of leather waste, coal, and sewage sludge were combusted in a lab-scale entrained flow fluidized bed furnace. The influence of blending ratio on emission characteristics of SO₂, NO_x, HCl, particulate matter (PM), heavy metals, and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) was studied. Results showed that the mixing of coal with sewage sludge had a complex effect on the emission characteristics. On the one hand, with more sewage sludge blending in the mixed fuel, the acid gas pollutant (SO₂, NO_x) decreased a lot, and the recovery of volatile heavy metals (Cd, Pb) increased at the same time. Furthermore, the leaching toxicity of Cr in the fly ash and bottom ash went down below the national standard with the adding of sewage sludge. On the other hand, the mixing of sewage sludge which consisted of more ash content resulted in the increase of the PM emission. Moreover, the high content of Cu and chlorine in the sewage sludge can promote the formation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) when the fuel 3 and 4 were combusted. Most importantly, the concentration of toxic PCDD/Fs in the flue gas produced from fuel 3 and fuel 4 was successfully controlled down below 0.20 ng I-TEQ/Nm³ by the active carbon.

     

高架连续点源落地浓度预测中风速的确定

高架连续点源污染物排放落地浓度是大气环境影响预测的主要内容。由于大气污染物扩散明显受气象条件尤其是风速的影响,而现有预测模型中对于风速的取值都是按经验值来确定的。通过分析在不同气象和烟源条件下,平均风速的计算方法对烟羽抬升高度以及最大落地浓度产生的影响,与实测值相比较确定了风速取值的合理方法,缩小了预测偏差。     

Nutrient run-off following application of livestock wastes to grassland

Three types of farm waste (cattle slurry, dirty water and farm yard manure (FYM)) were applied to hydrologically isolated grassland plots on a sloping poorly draining soil. Two applications were made, the first in October and the second in February. Application rates were 50 m(3) ha(-1) of slurry and dirty water and 50 t ha(-1) of FYM. Volumes of run-off following rainfall events and concentrations of N, P and K in run-off were measured. Losses of nutrients were higher following applications made with the soil at field capacity and rainfall soon after application. In terms of percentage loss of applied nutrients, losses were generally low. Concentration of N in run-off from the dirty water and FYM treated plots following the first application and the slurry treated plots following the second application exceeded 11.3 mg dm(-3) (a recommended limit for drinking water) although the maximum concentration recorded was 15 mg dm(-3) following FYM application. Concentration of P in run-off only exceeded 1 mg dm(-3) following the second application of cattle slurry. Concentration of K exceeded 10 mg dm(-3) following the first application of FYM and the second application of cattle slurry.     

微波处理多种固废制备微晶玻璃

以不锈钢渣、铜渣和粉煤灰为原料,通过熔铸法与微波晶化法相结合制备矿渣微晶玻璃,研究铜渣添加量 (Fe₂O₃) 对矿渣微晶玻璃结晶特性与重金属迁移规律。结果表明,铜渣中的Fe₂O₃对微晶玻璃结晶具有调控作用,5%的铜渣添加量会促进辉石结晶;当铜渣超过15%导致了磁铁矿的结晶,抑制辉石析晶。不锈钢渣与铜渣中的重金属Zn、Mn、Cr离子在玻璃结晶过程迁移进入尖晶石,尖晶石为辉石提供形核质点,诱导辉石外延尖晶石析晶。在矿渣微晶玻璃中辉石包裹尖晶石形成“核-壳”结构,对重金属离子有效固化。本研究结果可为高值化利用多种固废制备矿渣微晶玻璃及重金属固化研究提供参考。     

The surface radiative forcing of nitric acid for northern mid-latitudes

Ground-based, high-resolution measurements of downward atmospheric thermal emission spectra are reported for a northern mid-latitude location for summer and winter conditions. These measurements clearly show the presence of the 11.3-μm thermal emission band of nitric acid situated between 850–920 cm⁻¹. By using the FASCOD3 line-by-line radiation code to simulate the background thermal emission, the measured seasonally averaged surface radiative forcing due to nitric acid is determined to be 0.055 W m⁻²±15%. The zenith column amounts of nitric acid are found to vary between 7.9×10¹⁵ and 1.1×10¹⁶ molecules cm⁻²±15%. An estimation is made of the contribution of nitric acid to the direct radiative forcing of the Earth's surface since pre-industrial times for northern mid-latitudes. This work suggests that nitric acid may play a role that is comparable to that of other greenhouse gases, such as CFC-11, in the forcing of the Earth's climate system. Under polluted conditions, nitric acid may contribute about half of the radiative forcing that is currently associated with tropospheric ozone.     

Observations and assessment relating to incineration of chlorinated chemical wastes

Tests have been carried out on the chemical waste incinerator operated by Re-Chem International at Bonnybridge, Scotland, to determine whether any emissions of polychlorodibenzo-p-dioxins (PCDD) or polychlorodibenzofurans (PODF) occurred during incineration under typical conditions of certain organo-chlorine feedstocks. No detectable emissions of PCDDs or PCDFs were found during the incineration of 2,4,5-I esters, pentachlorophenol residues or PCB in liquid form. A just measurable amount of 2,3,7,8 TCDF was detected during the incineration of large intact capacitors and prior shredding, or puncturing, is preferred. The measured levels of PCDDs and PCDFs in soils collected in the vicinity of the Bonnybridge plant were found to be comparable to or less than those reported in urban or rural environments elsewhere. The reported detection of these compounds in a soil sample collected in 1877 suggests that they may be ubiquitous. It is demonstrated that cows grazing close to the Bonnybridge incinerator are unlikely to have suffered ill-effects from these emissions.     

响应面法优化黄粉虫幼虫处理餐厨垃圾饲养条件的研究

研究了黄粉虫幼虫处理餐厨垃圾的方法。首先在饲养温度、饲料含水量和饲养密度等条件下进行单因素实验,然后,以利用率为指标,运用响应面法优化了黄粉虫幼虫处理餐厨垃圾的饲养条件,结果表明,最佳饲养条件为饲养温度26.7℃、饲料含水量14.5%、饲养密度4.1头/cm2。在此饲养条件下,黄粉虫对餐厨垃圾利用率理论值为38.72%,实际餐厨垃圾利用率为38.88%,相对误差为0.41%,说明利用黄粉虫幼虫处理餐厨垃圾具有较好的效果。     

SCR脱硝系统烟道内流场优化

为了改善选择性催化还原法(SCR)催化剂上游烟气的流场、温度场和浓度场分布,基于CFD仿真分析技术,建立了整个脱硝系统三维模型,并通过优化导流板及整流格栅,使得速度标准偏差、浓度标准偏差、温度偏差、速度偏转角以及压降等性能指标都满足设计要求,在满足脱硝效率和氨逃逸率前提下,大大降低了烟气对催化剂层的冲刷,保证催化剂的使用寿命。最后,为了合理布置吹灰器,对优化结构下粉尘颗粒在烟道内的运动情况进行了仿真分析研究,为设计提供了依据。     

Thermal exploitation of wastes with lignite for energy production

The thermal exploitation of wastewood with Greek lignite was investigated by performing tests in a laboratory-scale fluidized bed reactor, a 1-MW(th) semi-industrial circulating fluidized bed combustor, and an industrial boiler. Blends of natural wood, demolition wood, railroad sleepers, medium-density fiberboard residues, and power poles with lignite were used, and the co-combustion efficiency and the effect of wastewood addition on the emitted pollutants were investigated. Carbon monoxide, sulfur dioxide, and oxides of nitrogen emissions were continuously monitored, and, during the industrial-scale tests, the toxic emissions (polychlorinated dibenzodioxins and dibenzofurans and heavy metals) were determined. Ash samples were analyzed for heavy metals in an inductively coupled plasma-atomic emission spectroscopy spectrophotometer. Problems were observed during the preparation of wastewood, because species embedded with different compounds, such as railway sleepers and demolition wood, were not easily treated. All wastewood blends were proven good fuels; co-combustion proceeded smoothly and homogeneous temperature and pressure profiles were obtained. Although some fluctuations were observed, low emissions of gaseous pollutants were obtained for all fuel blends. The metal element emissions (in the flue gases and the solid residues) were lower than the legislative limits. Therefore, wastewood co-combustion with lignite can be realized, provided that the fuel handling and preparation can be practically performed in large-scale installations.     

Current approaches to the revegetation and reclamation of metalliferous mine wastes

Abandoned metalliferous mine wastes can result in severe pollution and have aesthetic impacts on the local environment. Use of a vegetation cover gives a cost-effective and environmentally sustainable method of stabilising and reclaiming wastes such as mine-spoils and tailings. Many characteristics of metalliferous wastes are often inimical to successful vegetation establishment, most notably phytotoxic levels of residual heavy metals, low nutrient status and poor physical structure of the substratum. Current approaches to revegetation and reclamation involve both ameliorative and adaptive strategies to allow plant establishment and encourage subsequent vegetation development. Different techniques of revegetation are available for temperate and arid, subtropical regions depending on the characteristics of the waste. These include direct seeding with commercially available plants, use of cover and barrier systems and the enhancement of natural revegetation processes.     

利用工业废渣固化软土的试验研究

根据软土固化所需水化物组成的特殊性以及固化土结构形成过程的特点,有针对性地选择煤矸石、电石渣和磷石膏制备成以工业废渣为主要成分的软土固化剂。试验表明：采用合理的组成设计,充分利用不同工业废渣在提供碱性物质和膨胀性物质、调整胶结性水化物与膨胀性水化物生成速率协调性等方面的技术优势,利用工业废渣制备的固化剂与普通水泥相比可使固化土强度提高数倍。