垃圾焚烧的二次污染物排放处理

随着垃圾焚烧技术的不断发展,由此产生的二次污染问题也日益显现出来,主要包括垃圾焚烧所产生的飞灰污染、烟气中二恶英以及重金属的污染,特别是二恶英污染已引起全世界的关注,这对垃圾焚烧工艺的进一步发展提出了新的挑战。污染给人类的生存环境造成了很大的破坏,严重威胁着人类的安全。因而,二次污染物的排放控制问题成为亟待解决的问题。本文就垃圾焚烧所产生的二次污染物的排放处理进行讨论。     

Thermophilic composting of municipal solid waste

Process of composting has been developed for recycling of organic fraction of municipal solid waste (MSW). The bioreactor design was modified to reduce the composting process time. The main goal of this investigation was to find the optimal value of time period for composting of MSW in thermophilic bioreactor under aerobic condition. The temperature profiles correlated well with experimental data obtained during the maturation process. During this period biological degraders are introduced in to the reactor to accelerate the composting process. The compost materials were analyzed at various stages and the environmental parameters were considered. The final composting materials contained large organic content with in a short duration of 40 days. The quantity of volume reduction of raw MSW was 78%. The test result shows that the final compost material from the thermophilic reactor provides good humus to build up soil characteristics and some basic plant nutrients.     

城市固体废弃物典型组分的快速热解产气特性研究

选取城市固体废弃物中的常见六种组分(纸屑、厨余、织物、木屑、塑料、橡胶)作为实验物料进行快速热解实验。在所得实验数据的基础上对热解气体产物的组成以及变化情况进行了分析，并研究了热解混合气的热值随时间变化的情况。通过研究有助于对热解产物进行预测，且能够深入地了解热解机理。     

Energy potential from municipal solid waste in Malaysia

The average amount of municipal solid waste (MSW) generated in Malaysia is 0.5–0.8 kg/person/day and has increased to 1.7 kg/person/day in major cities. This paper highlights the MSW characteristics for the city of Kuala Lumpur. Currently, the waste management approach being employed is landfill, but due to rapid development and lack of space for new landfills, big cities in Malaysia are switching to incineration. A simple evaluation was conducted to establish the amount of energy that would be recovered based on the characteristics of the MSW if it were to be incinerated. From the characterization exercise, the main components of the Malaysian MSW were found to be food, paper and plastic, which made up almost 80% of the waste by weight. The average moisture content of the MSW was about 55%, making incineration a challenging task. The calorific value of the Malaysian MSW ranged between 1500 and 2600 kcal/kg. However, the energy potential from an incineration plant operating based on 1500 ton of MSW/day with an average calorific value of 2200 kcal/kg is assessed to be at 640 kW/day.     

Hydrogen-rich syngas produced from co-gasification of municipal solid waste and wheat straw in an oxygen-enriched air fluidized bed

The gasification characteristics of solid waste and wheat straw were investigated in an oxygen-rich atmosphere by using a laboratory-scale continuous fluidized bed reactor in the range of oxidation equivalent (ER) of 0.2~0.5 and reaction temperature of 600 °C~900 °C. Gasification of biomass and waste is an economical method for hydrogen production. When air is used as a carrier gas to gasify municipal solid waste, increasing the oxygen concentration can effectively increase the hydrogen concentration of the syngas. The product distribution of gasification reaction under different mixing ratios and reaction parameters was obtained. As is shown in the results, first, when the ER is between 0.2 and 0.5, if ER decreases by 0.1, the hydrogen concentration of gas production will increase by about 30%; second, if the oxygen concentration increases by 5%, the hydrogen concentration of gas production will increase by about 14%, and the calorific value of gas production will increase by about 14–18%; third, after adding wheat straw in a ratio of 1:1, due to the reduction of plastics, the overall yield of syngas decreased, but the yield of hydrogen increased, and the concentration of hydrogen in syngas increased by 6.4%.     

有机固体废弃物在固定床内热解的实验研究

通过对几种典型的城市有机固体废弃物的热解实验，为开展新的垃圾处理工艺提供基础研究。文中考察了不同工况下的有机固体废弃物的热解产物特性，分析了物料性质、热解终温、加热方式等因素对热解产物分布的影响。通过实验发现，热解终温是较重要的影响因素，同时物料的工业分析结果也是一个重要因素。     

An experimental study on a novel shredder for municipal solid waste (MSW)

Based on composition and volume-mass properties of MSW (i.e., unit weight, void ratio, and water content), a new way for the breakage of the organic MSW is presented to effectively convert MSW to heat and fuel gas. A lab-scale shredder consisting of compaction and shredding chambers is designed and the breakage process of MSW in the shredder can be divided into three successive phases: deformation, further deformation, compressive shearing. The performances of the shredder, such as the effect of the rotor velocity and hydraulic pressure on product size distribution and specific energy are investigated. The results show that with hydraulic pressure the specific energy is reduced, and size distribution of product is finer. When hydraulic pressure is constant, the specific energy decreases with increasing rotor velocity, while the products size distribution is coarser.     

Low‐temperature pyrolysis of municipal solid waste: influence of pyrolysis temperature on the characteristics of solid fuel

This paper presents the results of pyrolysis experiments of the mixtures of nine different combustibles municipal solid wastes (MSW's main composition: rice 24.33% and fruits 14.60%). The experiments were carried out in a laboratory‐scale reactor under nitrogen atmosphere at temperature of 300–700°C. The study concentrates on low‐temperature pyrolysis of MSWs and the effect of the pyrolysis temperature on the characteristics of the products (solid fuels) including proximate analysis, volatile content, heating value, ignition temperature and density of the solid fuel. The results indicate that the pyrolysis temperature plays an important role on the characteristics of the solid fuels. The volatile content of the solid fuels decreases with the pyrolysis temperature so that the low‐pyrolysis MSW treating process has advantage for higher heating value of the solid fuel for energy recovery purpose. The heating value is in the range of 23–27 MJ kg^?1, equivalent to the heating value of low‐rank coals. Copyright © 2005 John Wiley & Sons, Ltd.     

Pyrolytic oil from fixed bed pyrolysis of municipal solid waste and its characterization

Municipal solid waste, in the form of paper waste, has been converted into liquid oil by a fixed bed pyrolysis process. Favorable properties for pyrolysis conversion such as high volatile content, elemental composition, and thermochemical behavior of the waste were investigated by characterization study. The waste paper feedstock was pyrolyzed in an externally heated 7 cm diameter, 38 cm high fixed bed reactor with nitrogen as a carrier gas. The pyrolysis oil was collected in a series of condenser and ice-cooled collectors. The char was separately collected while the gas was flared. The effect of process conditions, like fixed bed reactor temperature, feedstock size and effect of running time on the product yields, was studied. The composition of the oil was determined at a bed temperature of 450 °C, at which the liquid yield was maximum. The liquid product was analyzed for physical, elemental and chemical composition using Fourier transform infra-red (FTIR) spectroscopy.     

Steam catalytic gasification of municipal solid waste for producing tar-free fuel gas

In the paper, a two-region municipal solid waste (MSW) steam catalytic gasification process was proposed. The gasifier was composed of two individual reactors: one is the gasification reactors and the other is the catalytic reactor. The MSW was initially gasified and the produced tar was gasified in the gasification reactor, and further, the tar not gasified entered the catalytic reactor together with the fuel gas and was catalytically decomposed to fuel gas. The influences of the catalysts, steam and temperature on the content of tar, dry gas yield and composition, and carbon conversion efficiency were studied. The results indicated that under the optimum operating conditions, the dry gas yield can be up to 1.97 Nm³/kg MSW and the tar in the product can be completely eliminated. The concentration of hydrogen, carbon monoxide and methane in the fuel gas produced was 50.8%, 9.32% and 13.3%, respectively.     

城市垃圾中温热解新技术

简要阐述了国内外垃圾热解技术的发展概况,详细介绍了几种典型的垃圾热解工艺,在吸收各种垃圾热解技术优势的基础上,结合我国城市垃圾的特点,提出了一种新型的城市垃圾中温热解技术,通过经济效益分析和社会效益分析,说明这项技术具有广阔的应用前景。     

Hydrogen-rich gas from catalytic steam gasification of biomass in a fixed bed reactor: Influence of particle size on gasification performance

The catalytic steam gasification of biomass was carried out in a lab-scale fixed bed reactor in order to evaluate the effects of particle size at different bed temperatures on the gasification performance. The bed temperature was varied from 600 to 900 °C and the biomass was separated into five different size fractions (below 0.075 mm, 0.075–0.15 mm, 0.15–0.3 mm, 0.3–0.6 mm and 0.6–1.2 mm). The results show that with decreasing particle size, the dry gas yield, carbon conversion efficiency and H₂ yield increased, and the content of char and tar decreased. And the differences due to particle sizes in gasification performance practically disappear as the higher temperature bound is approached. Hydrogen and carbon monoxide contents in the produced gas increase with decreasing particle size at 900 °C, reaching to 51.2% and 22.4%, respectively.     

Electro-stimulated biological production of hydrogen from municipal solid waste

Hydrogen production from municipal solid wastes was investigated by applying a weak current (0.06 A) to a slurry of municipal solid waste in an anaerobic reactor at 55 °C using 4 electrodes (carbon graphite for the cathode and platinum electroplated titanium for the anode). Current application to the organic waste stimulated the hydrogen producing bacteria especially bacteria related to the Thermotogales and Bacillus families. Measured hydrogen production rates were comprised between 16 and 41 mL/h. Comparison of bacterial and archaeal communities in methane-producing (control) and electro-stimulated reactors showed similar species but with different dynamics correlated to hydrogen or methane production. Energy efficiency of the overall bioelectrolysis process using municipal solid waste and an applied voltage of 3V was approximately 12.4%, which is relatively low compared to values reported in the literature for organic wastes and can be explained by the low organic carbon content and availability in the municipal solid waste. Results of this study highlight some important operational constraints with respect to electro-stimulated hydrogen production from organic wastes; related in particular to electrode lifetime expectancies. Results nevertheless illustrate the potential for hydrogen production from municipal solid waste as a possible route for energy recovery.     

Simulation analysis of municipal solid waste pyrolysis and gasification based on Aspen plus

To predict and analyze the municipal solid waste (MSW) pyrolysis and gasification process in an up-draft fixed bed more veritably and appropriately, numerical modeling based on Gibbs energy minimization was executed using the Aspen plus software. The RYield module was combined with the RGibbs module to describe the pyrolysis section, while the RGibbs module was used for the gasification section individually. The proposed model was used to forecast and analyze the target performance parameters including syngas composition, lower heating value (LHV) and carbon conversion rate under different conditions of the gasification temperatures, and ratios and types of gasifying agents. The results indicate that there is a good agreement between the experimental data and the simulated data obtained using this model. The predicted optimum gasification temperature is approximately 750°C, and the best ratio of water vapor as gasifying agent is around 0.4. The mixture of flue gas and water vapor has an economical and recycled prospect among four commonly used gasifying agents.     

Assessing the power generation,pollution control,and overall efficiencies of municipal solid waste incinerators in Taiwan

This paper evaluates the productivity of municipal solid waste incinerators (MSWIs) by addressing the following questions: (1) to what extent should one further increase the production of power generation while maintaining the emission of noxious air at the current level?; (2) To what extent should one further decrease the emission of noxious air while maintaining the production of power generation at the current level?; and (3) To what extent should one increase the production of power generation and decrease the emission of noxious air simultaneously? To effectively address these questions to improve performance, the power generation and pollution control efficiencies are evaluated using TODEA (two-objective data envelopment analysis), as well as the overall efficiency evaluated using Tone’s NS-overall model (slacks-based measure with non-separable desirable and undesirable outputs for evaluating overall efficiency). A MSWI case study in Taiwan with the panel data covering the period of 2004–2008 reveals that the power generation and overall efficiencies of build-operate-transfer are more efficient, on average, than those of public-own-operate and build-own-operate. However, the three building and operation types do not significantly differ in pollution control efficiency.     

Partitioning of heavy metals during municipal solid waste incineration on a laboratory fluid bed furnace

The content of heavy metals in the main physical compositions of municipal solid waste (MSW) is analyzed. The effects of temperature, chlorine and water on the partitioning of heavy metals are studied using a laboratory fluidized-bed (FB) furnace with simulated MSW composition. The experimental results show that temperature and chloride content in the feed have significant influence on the volatility of heavy metals, especially those of lower boiling point such as Hg, Cd and Zn. The influence of water is slight. Translated from Proceeding of the CSEE, 2005, 25(17): 100–104 [译自: 中国电机工程学报]     

An analysis of power generation from municipal solid waste (MSW) incineration plants in Taiwan

Heavily (about 99%) depending on imported energy, Taiwan, a country in the subtropics, has limited natural resources. In this regard, biomass energy from (MSW) municipal solid waste incineration plants thus became attractive during the 1990s. The objective of this paper is to present a comprehensive analysis of MSW-to-energy in Taiwan. This paper gave a concise summary of current status of domestic energy consumption &; power generation, MSW generation &; MSW incineration treatment, and electricity generation from MSW incineration plants since 2000. Based on the electricity generation in 2008 (i.e., 2967 GWh), the environmental benefit of mitigating CO₂ emissions and the economic benefit of selling electricity were preliminarily calculated to be around 1.9 × 10⁶ tons and US$ 1.5 × 10⁸, respectively. However, since the heat content of incinerated MSW and the methodologies were used on the recommendation of the (IPCC) Intergovernmental Panel on Climate Change, the net emissions of CO₂ equivalent from methane (CH₄) &; nitrous oxide (N₂O) have been estimated to be at around 76,000 and 88,000 tons/year compared to coal and oil, respectively.     

Supplying hydrogen vehicles and ferries in Western Norway with locally produced hydrogen from municipal solid waste

Gibbs free energy minimization has been used to estimate the hydrogen production potential of air gasification of the wet organic fractions of municipal solid waste available in the Bergen region in Western Norway. The aim of this work was to obtain an upper limit of the amount of hydrogen that could be produced and to estimate of the number of vehicles: passenger ferries and cars that could be supplied with an alternative fuel. The hydrogen production potential was investigated as function of waste composition, moisture content, heat loss, and carbon conversion factor. The amount of hydrogen annually available for both gasification and gasification combined with water-gas-shift-reaction was calculated for different scenarios. Up to 2700 tonne H₂ per year could be produced in the best case scenario; which would, if only utilised for maritime operations, be enough to supply nine ferries and ten fast passenger boat connections in the Hordaland region in Western Norway with hydrogen.     

Organic municipal solid waste (MSW) as feedstock for biodiesel production: A financial feasibility analysis

The pursuit towards an alternative solution to fossil fuel has facilitated science investigation initiatives that compare various options leading to biodiesel production. Besides conventional feedstock derived from vegetable oils, alternative sources that could be produce in large scale at competitive costs are the main scope of research in this field. This paper investigates the financial feasibility using organic solid waste as a feedstock, which results in the production of biodiesel through the conversion of volatile fatty acids into lipids (VFA). As a result, based on existing references of capital and operating costs, production and extraction yields for VFA and lipids and an internal rate of return of 15% in real terms, we concluded that biodiesel production is competitive compared to subsidized biodiesel traded in regions of Europe and the United States. These results encourage research aims to examine this technology at a larger scale. The adoption of public policies for the urban waste's disposal and collection, to reduced municipality's costs associated to the treatment, is also important for the implementation of these technologies.     

城市固体废物焚烧过程中二恶英的生成和控制

文中综述了城市固体废物焚烧过程中二恶英的产生机理和影响因素，在此基础上介绍了垃圾焚烧过程中二恶英的各种控制技术和方法。