回转窑在医废焚烧工程应用中的参数优化

以规模3 t/h的某医疗废物焚烧生产线为依托,优化分析了回转窑焚烧装置核心控制参数（窑头温度、供风量及窑转速）,考察了不同负荷、回转窑转动模式及进料方式对焚烧效果的影响,结果表明：窑头温度升高,有利于提高焚烧效果,是影响焚烧效果最重要的工艺参数;75%负荷时最佳工况是窑头温度850℃、窑转速0.09 r/min、供风量7 000 Nmc/h;连续反转的回转窑转动模式和恒流量的连续进料技术,有助于保持良好焚烧工况,炉渣热灼减率分别达到2.6%和2.3%。     

Biological solubilization and mineralization as novel approach for the pretreatment of food waste

The performance of a garbage disposal system to solubilize and mineralize food wastes through biological solubilization was evaluated through the examination of the effects of operational conditions like water supply volume, water supply frequency and aeration on the amount of waste solubilized, mineralized and accumulated in the reactor. The biological solubilization process consisted of a solubilization reactor and a circulation tank. Food waste and fresh water were supplied into the solubilization reactor with support media. Wastewater from the solubilization reactor was discharged to the circulation tank and water in the circulation tank was periodically pumped back to the solubilization reactor. In case of the total food waste loading of 16 kg m(3-1) d(-1), little carbon (0-5.7%) accumulated in the reactor as long as the system was kept under aerobic condition through large volume of water supply (higher than 3.5 lh(-1)) or applying aeration in the circulation tank. However, 42% of the loaded carbon accumulated under anaerobic condition in low water supply (less than 1.8 lh(-1)). The rest of the waste was either solubilized or mineralized. The aeration in the circulation tank, therefore, was effective to provide similar solubilization and mineralization as the large volume of water supply. However, frequency of feeding at the large volume of water supply had no significant effect on the amount of waste solubilization and mineralization.     

低污染的危险废物焚烧技术研究

目前危险废物焚烧中产生的污染物主要通过尾气处理去除 ,本文认为尾气处理应与通过控制焚烧条件减少尾气中污染物的原始浓度相结合 ,以减少后续处理设备的投资。本文主要讨论了控制危险废物焚烧中主要污染物颗粒物、氯化氢、SOx、NOx、二的焚烧技术     

Emission of organic micropollutants from waste incineration

Flue gas emission from a small, discontiniously operated, waste incinerator located in a high rise building was analysed. Sampling of particles and organic micropollutants was made during two combustion cycles. The samples were chemically analysed by HPLC-fractionating and gas chromatography. The PAH and PAH-derivatives were characterized in detail by GC/MS.     

An analysis of biomedical waste incineration.

The California Air Resources Board (ARB) completed a series of source tests of eight operating biomedical waste incinerators (BMWI) under conditions of typical operation. The emissions of certain metals, and chlorinated dioxins and furans in the flue gases of BMWI are relatively high in comparison to emissions from other combustion sources, such as hazardous waste or municipal waste incinerators of modern design. This study reports on an analysis of the status of the existing regulatory framework and the California data base. Clarification of definitional issues at the federal level is needed to effectively treat BMWI management issues. Although few relationships among combustion parameters and emissions were uncovered, patterns of emissions were evident, suggesting commonality and relationships among the waste stream constituents and emissions. Potential implications for future research, operation of BMWI, controls and source reduction and waste segregation strategies are also discussed.     

城市垃圾预处理改善焚烧特性的探讨

针对目前我国城市垃圾的高水分、低热值的特性,提出了2种改善城市垃圾焚烧特性的有效措施:生物质垃圾源分类和生物干燥.在我国建立生物质垃圾源分类体系,将生物质垃圾源头分类后,剩余垃圾的热值可以提高约50%～120%,已适合直接入炉焚烧,同时分离出来的生物质垃圾也更易于好氧堆肥或厌氧消化.另外一项技术措施是在焚烧前利用生物干燥技术,降低城市垃圾的水分含量,提高入炉垃圾的热值,这种方法主要是利用生物反应热来干燥城市生活垃圾,只需要在垃圾投入焚烧炉前增加一个预处理步骤,不必改变目前的垃圾收运体系,而且进行生物干燥后的垃圾更易于分选其中的可回收物质.     

Fate of antimony in municipal solid waste incineration

The average antimony concentration in municipal solid waste is estimated to be about 10-60 ppm. Thermodynamical models predict a volatile behavior for antimony compounds, yet literature mass balances show that about 50% of the antimony input remains in the grate ashes. This fact can be explained by the formation of thermally stable antimonates in the fuel bed due to interactions with alkali or earth-alkali metals. Thermogravimetric experiments revealed an increased thermal stability for antimony oxide in presence of oxygen and calcium oxide. Spiking experiments on the test incinerator TAMARA showed that chlorination processes have a strong effect on antimony volatilization whereas high fuel-bed temperatures and addition of antimony oxide only have a moderate effect. In the grate ashes, antimony shows a pH-depending leaching property, which is typical for anionic species. This fact supports the thesis that antimony is present in the grate ashes in an anionic speciation.     

Dehalogenation potential of municipal waste incineration fly ash

BACKGROUND, AIMS AND SCOPE: It is well known that the fly ash from filters of municipal waste incinerators (MWI-FA) shows dehalogenation properties after heating it to 240-450 degrees C. However, this property is not general, and fly ash samples do not possess dehalogenation ability at all in many cases. Fly ash has a very variable composition, and the state of the fly ash matter therefore plays the decisive role. In the present paper, the function of important components responsible for the dehalogenation activity of MWI-FA is analysed and compared with the model fly ash. METHODS: With the aim of accounting for the dehalogenation activity of MWI-FA, the following studies of hexachlorobenzene (HCB) dechlorination were performed: The role of copper in dehalogenation experiments was evaluated for five types of metallic copper. The gasification of carbon in MWI-FA was studied in the 250-350 degrees C temperature range. Five different kinds of carbon were used, combined with conventional Cu(o) and activated nanosize copper powder. The dechlorination experiments were also carried out with Cu(II) compounds such as CuO, Cu(OH)2, CuCl2 and CuSO4. The results were discussed from the standpoint of thermodynamics of potential reactions. Based on these results, the model of fly ash was proposed, containing silica gel, metallic copper and carbon. The dechlorination ability of MWI-FA and the model fly ash are compared under oxygen-deficient atmosphere. CONCLUSIONS: The results show that, under given experimental conditions, copper acts in the dechlorination as a stoichiometric agent rather than as a catalyst. The increased surface activity of copper enhances its dechlorination activity. It was found further that the presence of copper leads to a decrease in the temperature of carbon gasification. The cyclic valence change from Cu(o) to Cu+ or Cu2+ is a prerequisite for the dehalogenation to take place. RECOMMENDATION AND OUTLOOK: Thermodynamic analysis of the dechlorination effect, as well as the comparison of dechlorination pathways on MWI-FA and model fly ash, can provide a deeper understanding of the studied reaction.     

添加生物油对垃圾焚烧烟气选择性非催化还原脱硝的强化作用及其机理

为揭示添加生物油对垃圾焚烧选择性非催化还原(SNCR)脱硝特性的影响规律及作用机理,利用高温管式炉开展了实验,以研究生物油添加比例(β)、氨氮比(NSR)及氧浓度对SNCR脱硝特性与CO排放的影响;结合SNCR基元反应与生物油热分解产物的成分,分析了添加生物油对烟气选择性非催化还原脱销的强化作用机理.结果 表明,添加生...     

Investigation of 1,4-dioxane originating from incineration residues produced by incineration of municipal solid waste

As a groundwater contaminant, 1,4-dioxane is of considerable concern because of its toxicity, refractory nature to degradation, and rapid migration within an aquifer. Although landfill leachate has been reported to contain significant levels of 1,4-dioxane, the origin of 1,4-dioxane in leachate has not been clarified until now. In this study, the origins of 1,4-dioxane in landfill leachate were investigated at 38 landfill sites and three incineration plants in Japan. Extremely high levels of 1,4-dioxane 89 and 340 microg l(-1), were detected in leachate from two of the landfill sites sampled. Assessments of leachate and measurement of 1,4-dioxane in incineration residues revealed the most likely source of 1,4-dioxane in the leachate to be the fly ash produced by municipal solid waste incinerators. Effective removal of 1,4-dioxane in leachate from fly ash was achieved using heating dechlorination systems. Rapid leaching of 1,4-dioxane observed from fly ash in a sequential batch extraction indicated that the incorporation of a waste washing process could also be effective for the removal of 1,4-dioxane in fly ash.     

Polycyclic aromatic hydrocarbon emissions from clinical waste incineration

Since the introduction of the Environmental Protection Act in the UK, there are few reports of PAH emissions from clinical waste incinerators (CWIs) operating to improved performance standards. The main aim of this study is to determine PAH emissions from a state-of-the-art CWI focusing on the effects of reactive gases and operating variables on emissions. This was carried out by collection of stack samples over three phases of operation.

At stack conditions, most PAHs are predicted to be in the vapour phase. Reactive losses of PAHs were closely correlated by rank with expected reactivities from laboratory studies. Estimates of emissions incorporating sampling losses were derived, although no correlation was found between PAH losses and the modest levels of reactive stack gases. PAH concentrations were one to two orders of magnitude lower than earlier reports from incinerators without effective air pollution control equipment (APCE). The low levels of carbon monoxide recorded were not correlated with any PAHs.

This study demonstrates the impact of efficient combustion conditions and APCE on PAH emissions from a CWI.     

Characteristic analysis for odor gas emitted from food waste anaerobic fermentation in the pretreatment workshop

Gas chromatography–mass spectrometry, olfactometry, and other related methods were applied for the qualitative and quantitative analysis of the characteristics of odorous gases in the pretreatment workshop. The composition of odorous gases emitted from municipal food waste was also investigated in this study. The results showed that the tested gases are mainly composed of aromatic gases, which account for 49% of the total volatile organic compounds (VOC) concentrations. The nitrogenous compounds comprise 15% of the total concentration and the other gases comprise the remaining 36%. The level of odor concentration ranged from 2523 odor units (OU) m^?3 to 3577 OU m^?3. The variation of the total chemical composition ranged from 19,725 µg m^?3 to 24,184 µg m^?3. Among the selected four sampling points, the discharge outlet was detected to have the highest concentration in terms of odor, total chemical, sulfur compounds, and aromatics. The correlation analysis showed that the odor concentrations were evidently related to the total chemical composition, sulfur compounds, and aromatics (P < 0.05, n = 5). The odor activity value analysis identified the top three compounds, hydrogen sulfide (91.8), ethyl sulfide (35.8), and trimethylamine (70.6), which contribute to air pollution complaint of waste materials.

Implications: Currently, the amount of food waste has rapidly increased, which leads to difficulty in waste management and more odorous gases released as air pollution. In processing of food wastes by anaerobic fermentation, odorous gases are generated, which significantly affect the workers and occupants in the plant. In the pretreatment workshop for anaerobic decomposition, the odorous gases are generated because of the stacking and decomposition of food wastes. The gases emitted mainly consist of organic gases because the food wastes are mainly organic materials. The other odors that comprise 1% of the gases are S-compounds, aromatics, esters, alkanes, and limonene, which result in unpleasant odors that are harmful to the health.     

城市生活垃圾焚烧飞灰的熔融分离处理

焚烧法处理城市生活垃圾已在世界先进发达国家广泛采用。垃圾焚烧飞灰含有大量的重金属,必须进行合理安全处置。在分析城市生活垃圾焚烧飞灰的物理化学性质基础上,研究了垃圾焚烧飞灰固化成型、熔融分离的无害化处理新工艺。实验结果表明：飞灰固化成球的适宜粘结剂为5%～7%消石灰,养护时间为10～12 d,固化球强度达0.24 kg/cm²以上,可以满足运输和熔化分离要求;固化后的飞灰在1 300℃左右熔融分离后,重金属的分离效果好,达到97%以上,可达到无害化处理标准;对1 300℃和1 400℃熔融分离后熔渣的重金属浸出毒性测试显示,重金属浸出毒性问题可以完全解除。研究结果表明,采用飞灰固化-熔融分离工艺处理城市生活垃圾焚烧飞灰是可行的。     

垃圾焚烧飞灰的资源化处置前景

对大量数据进行统计分析,得出垃圾焚烧飞灰中主要重金属元素和二噁英类物质的含量分布特征,并根据垃圾焚烧飞灰的综合特点,结合其他领域现有技术,初步提出了3个垃圾焚烧飞灰的资源化处置方案:①烧制陶粒;②作为凝石成岩剂的原料;③作为上流式厌氧污泥床(UASB)或膨胀式颗粒污泥床(EGSB)废水处理装置的生化反应促进剂.同时回收重金属,并对其前景进行了初步分析.若将上述3个方案逐步完善,不但能节约1000～2000元/t的垃圾焚烧飞灰处置费用,还能够产生很大的附加经济效益.     

热活化过硫酸盐预处理的餐厨垃圾凝胶基缓释氮肥制备及性能

水凝胶转化是一种有前景的餐厨垃圾资源化新方式。采用热活化过硫酸盐对餐厨垃圾浆液进行预处理,并通过聚合交联制备出餐厨垃圾水凝胶 (food waste hydrogel,FWH) 。探究了各试剂投加量对FWH吸水性能的影响,表征了水凝胶的物理化学性质。通过FWH与牡蛎壳粉复配制备出凝胶基缓释氮肥,并以淋洗实验、保水性能实验和种子发芽实验评价其作为缓释氮肥的效果。结果表明,过硫酸钾/热处理系统可在1 h内实现餐厨垃圾浆液的高效水解。FWH样品具有良好的热稳定性,展示出疏松多孔的微观结构,且-OH、-C=O 等含氧官能团以络合反应的形式参与到FWH的合成过程中。在最佳合成条件下,最大吸水率可达351.4 g·g⁻¹,高共价阳离子会显著降低FWH的吸水率。复配后的凝胶基缓释氮肥不仅解决了FWH的酸化劣性,还具有较好的缓释氮肥和保水能力,施用后小白菜种子发芽率增加了17%。本研究结果可为餐厨垃圾资源化利用提供参考。     

Bromine in waste incineration partitioning and influence on metal volatilisation

INTENTION, GOAL, SCOPE, BACKGROUND: The halogen bromine is far less abundant than chlorine, but it can be found at high concentrations in special materials like flame retarded plastics. The fate and effects of Br in waste incineration are not well understood. It may have similar implications like Cl for the volatilisation of heavy metals and the formation of low volatile organic compounds. Due to its lower oxidation potential, there is a risk of formation of elementary Br2 in the offgas. OBJECTIVE: Co-combustion tests of different types of Br containing plastic waste materials (up to 22%) and MSW in the TAMARA pilot plant for waste incineration were conducted to investigate the Br partitioning and the influence of Br on metal volatilisation. METHODS: The Br inventory of the fuel mix was elevated to approx. 1 wt-%. All input and output mass flows of the furnace have been sampled and the partitioning of Cl, Br, S, and a number of heavy metals, has been calculated on the basis of closed mass balances. RESULTS AND DISCUSSION: Organically-bound Br was typically released to more than 90% into the raw gas. Elementary Br2 was detected at high Br levels. Its presence was always analysed when all SO2 in the raw gas was oxidised to SO3. Br enhances the volatilisation of metals like K, Zn, Cd, Sn, Sb, and Pb out of the fuel bed principally in the same way as Cl. The tests gave strong indication that the promoting influence of the halogens on metal volatilisation is more pronounced than that of the fuel bed temperature. The volatilised metals are condensated on the fly ashes and are discharged along with the filter ashes. CONCLUSIONS: As long as a surplus of SO2 is present in the raw gas no Br2 is formed. Although the halogen induced transfer out of the fuel bed causes high concentrations of volatile metals in the filter ashes, a recovery is not economically feasible for the time being. The volatilisation gives no rise to metal emission problems as long as efficient dedusting is achieved. RECOMMENDATION AND OUTLOOK: If there is a risk of Br2 formation, in wet scrubbing a reducing agent has to be added to the neutral scrubber for efficient abatement. Filter ashes should be disposed of in a way that enables access for recovery in the future. The exact volatilisation characteristics of the various metals have to be studied in future using specifically tailored experiments.     

Response surface optimization of substrates for thermophilic anaerobic codigestion of sewage sludge and food waste

This study investigated the effects of food waste constituents on thermophilic (55 degrees C) anaerobic codigestion of sewage sludge and food waste by using statistical techniques based on biochemical methane potential tests. Various combinations of grain, vegetable, and meat as cosubstrate were tested, and then the data of methane potential (MP), methane production rate (MPR), and first-order kinetic constant of hydrolysis (kH) were collected for further analyses. Response surface methodology by the Box-Behnken design can verify the effects and their interactions of three variables on responses efficiently. MP was mainly affected by grain, whereas MPR and kH were affected by both vegetable and meat. Estimated polynomial regression models can properly explain the variability of experimental data with a high-adjusted R2 of 0.727, 0.836, and 0.915, respectively. By applying a series of optimization techniques, it was possible to find the proper criteria of cosubstrate. The optimal cosubstrate region was suggested based on overlay contours of overall mean responses. With the desirability contour plots, it was found that optimal conditions of cosubstrate for the maximum MPR (56.6 mL of CH4/g of chemical oxygen demand [COD]/day) were 0.71 g of COD/L of grain, 0.18 g of COD/L of vegetable, and 0.38 g of COD/L of meat by the simultaneous consideration of MP, MPR, and kH. Within the range of each factor examined, the corresponding optimal ratio of sewage sludge to cosubstrate was 71:29 as the COD basis. Elaborate discussions could yield practical operational strategies for the enhanced thermophilic anaerobic codigestion of sewage sludge and food waste.     

城市垃圾焚烧厂直接掺烧城市污泥处置技术及其污染控制

为研究有效处置城市污泥的方法,通过改变掺烧配比、监测燃烧烟气等对燃烧过程的探索,研究了城市污泥直接与城市生活垃圾焚烧厂中的垃圾进行掺烧混烧的处置技术。结果表明：直接掺烧12.5%左右的城市污泥混烧,对生活垃圾入炉量、焚烧炉稳定以及污染物的排放量均未产生较大影响;根据掺烧城市污泥的烟气监测结果,直接掺烧城市污泥后,排放的污染物浓度虽略有升高,但都满足排放要求;掺烧前后产生的固体废物产生量基本没有太大变化,也未对周围环境造成影响。生活垃圾焚烧厂按照一定比例直接掺烧城市污泥(含水率80.0%)在技术上可行,可为城市污泥处置提供新思路。     

Relation between the exergy of waste emissions and measures of environmental impact

In an attempt to improve methodologies for assessing and predicting environmental impact, the relation between several measures of environmental impact potential and exergy is investigated. Exergy is a measure of the degree of disequilibrium between a substance and its environment. The approach taken compares current methods used to assess the environmental impact potential of waste emissions and the exergy associated with those emissions. The measures of environmental impact potential considered are the Ontario 7le of industrial air emission limits, and two methods of assessing the environmental costs for air emissions resulting from the combustion of three common fossil fuels: coal, oil and natural gas. A relationship was identified between one environmental costing methodology and exergy. Further work appears to be justified, using more data, to verify this relation, and to detect other relationships between the exergy of waste emissions and measures of environmental impact.     

Synthetic fuel for imitation of municipal solid waste in experimental studies of waste incineration

Synthetic fuel is prepared to imitate municipal solid waste (MSW) in experimental studies of incineration processes. The fuel is composed based on the Environmental Protection Agency reports on the materials contained in MSW. Uniform synthetic fuel pellets are prepared using available and inexpensive components including newsprint, hardwood mulch, low density polyethylene, iron, animal feed, sand, and water to imitate paperbound, wood, yard trimming, plastic, metal, food wastes, and other materials in MSW. The synthetic fuel preparation procedure enables one to reproduce and modify the fuel for a wide range of experiments in which the mechanisms of waste incineration are addressed. The fuel is characterized using standard ASTM tests and it is shown that its parameters, such as combustion enthalpy, density, as well as moisture, ash and fixed carbon contents are adequate for the representation of municipal solid waste. In addition, chlorine, nitrogen, and sulfur contents of the fuel are shown to be similar to those of MSW. Experiments are conducted in which the synthetic fuel is used for operation of a pilot-scale incinerator research facility. Steady-state temperature operation regimes are achieved and reproduced in these experiments. Thermodynamic equilibrium flame conditions are computed using an isentropic one-dimensional equilibrium code for a wide range of fuel/air ratios. The molecular species used to represent the fuel composition included cellulose, water, iron, polyethylene, methanamine, and silica. The predicted concentrations of carbon monoxide, nitric oxides, and oxygen in the combustion products are compared with the respective experimental concentrations in the pilot-scale incinerator exhaust.