Effects of Using Municipal Solid Waste Incineration Tailings as Lightweight Aggregate on the Mechanical Properties of Specified Density Concrete

Municipal solid waste incineration tailings were used as lightweight aggregate(MSWIT-LA)in the preparation of specified density concrete to study the effects on compressive strength,axial compressive strength,flexural strength,microhardness,total number of pores,pore area,and pore spacing.The results showed that the internal curing and morphological effects induced by an appropriate quantity of MSWIT-LA improved the compressive response of specified density concrete specimens,whereas an excessive quantity of MSWIT-LA significantly reduced their mechanical properties.An analysis of pore structure indicated that the addition of MSWIT-LA increased the total quantity of pores and promoted cement hydration,resulting in a denser microstructure than that of ordinary concrete.The results of a principal component analysis showed that the mechanical response of specified density concrete prepared with 25%MSWIT-LA was superior to that of an equivalent ordinary concrete.It was therefore concluded that MSWIT-LA can be feasibly applied to achieve excellent specified density concrete properties while utilising municipal solid waste incineration tailings to protect the environment and alleviate shortages of sand and gravel resources.

Model Prediction and Optimal Control of Gas Oxygen Content for A Municipal Solid Waste Incineration Process

In the municipal solid waste incineration process,it is difficult to effectively control the gas oxygen content by setting the air flow according to artificial experience.To address this problem,this paper proposes an optimization control method of gas oxygen content based on model predictive control.First,a stochastic configuration network is utilized to establish a prediction model of gas oxygen content.Second,an improved differential evolution algorithm that is based on parameter adaptive and t-distribution strategy is employed to address the set value of air flow.Finally,model predictive control is combined with the event triggering strategy to reduce the amount of computation and the controller's frequent actions.The experimental results show that the optimization control method proposed in this paper obtains a smaller degree of fluctuation in the air flow set value,which can ensure the tracking control performance of the gas oxygen content while reducing the amount of calculation.

Prediction of NO_(x)concentration using modular long short-term memory neural network for municipal solid waste incineration

Air pollution control poses a major problem in the implementation of municipal solid waste incineration(MSWI).Accurate prediction of nitrogen oxides(NO_(x))concentration plays an important role in efficient NO_(x)emission controlling.In this study,a modular long short-term memory(M-LSTM)network is developed to design an efficient prediction model for NO_(x)concentration.First,the fuzzy C means(FCM)algorithm is utilized to divide the task into several sub-tasks,aiming to realize the divide-and-conquer ability for complex task.Second,long short-term memory(LSTM)neural networks are applied to tackle corresponding sub-tasks,which can improve the prediction accuracy of the sub-networks.Third,a cooperative decision strategy is designed to guarantee the generalization performance during the testing or application stage.Finally,after being evaluated by a benchmark simulation,the proposed method is applied to a real MSWI process.And the experimental results demonstrate the considerable prediction ability of the M-LSTM network.

Volatilization of heavy metals during incineration of municipal solid wastes

Incineration experiments with MSW, which had been impregnated with heavy metals, were presented to obtain information on the volatilization behavior of the elements cadmium(Cd), lead(Pb), and zinc(Zn) under different conditions. Experiments were carried out in a bubbling fluid bed system connected to a customized inductively coupled plasma optical emission spectroscopy(ICP-OES) for analyzing metals in the flue gas. The results indicated that the combustion temperature, the gas atmosphere, and the chlorine content in the flue gas could affect the volatilization behavior of heavy metals. In the fluidized bed combustion, a large surface area was provided by the bed sand particles, and they may act as absorbents for the gaseous ash-forming compound. Comparer with the metals Cd and Pb, the vaporization of Zn was low. The formation of stable compounds such as ZnO·Al 2O 3 could greatly decrease the metals volatilization. The presence of chlorine would enhance the volatilization of heavy metals by increasing the formation of metal chlorides. However, when the oxygen content was high, the chlorinating reaction was kinetically hindered, which heavy metals release would be delayed.

FORMATION MECHANISMS AND CONTROL STRATEGIES FOR DIOXINS IN INCINERATION PROCESS OF MUNICIPAL SOLID WASTES

Dioxins, which are of the most toxic materials on the earth, are principal emitted from waste incineration process. The molecular structures, toxicity parameters, such as toxicity equivalency factor, tolerable daily intake and physic-chemical properties of dioxins are briefly summarized. Three formation mechanisms of dioxins in waste incineration process, namely as de novo synthesis, mechanisms involving small organic molecular as precursors and homogenous gas phase reaction mechanism are alto reviewed. The influencing factors for dioxins formation during waste incineration process are also discussed. Three major methods for reducing dioxins emission from waste incineration process are discussed based upon the formation mechanisms and influencing factors. A new waste incineration process with low dioxins emission and low hydrogen chloride corrosion has been proposed based on multi- stage unit operation principal according to formation mechanisms of dioxins and potential production location in waste incinerators.

Hydration Kinetics of Municipal Solid Wastes Incineration(MSWI) Fly Ash-Cement

Hydration heat behavior and kinetics of blended cement containing up to 20% MSWI fly ash were investigated based on its hydration heat evolution rate measured by isothermal calorimeter. Kinetics parameters, N and K, and hydration degree, Ca(OH)2 content, were also calculated and analyzed. According to the experimental results, the induction period was elongated, the second heat evolution peak was in advance, and the third hydration heat peak could be detected due to MSWI fly ash pozzolanic reaction. The hydration reaction rate was controlled by nucleation kinetics in the acceleration period and then by diffusion in the decay period, but in the deceleration period, the hydration experienced a dual controlling reaction of autocatalytic chemical reaction and diffusion. The hydration rate of blended cement was faster. Ca(OH)2 content increased before 14 days.

Comparative evaluation of processes for heavy metal removal from municipal solid waste incineration fly ash

Hydrochloric acid leaching, chloride evaporation, acetic acid leaching, and biological leaching were evaluated and compared as processes of heavy metal removal for municipal solid waste incineration fly ash(MSWFA). Six factors, namely, energy consumption, process efficiency, process handling, process cost estimation, cost reduction potential, and study progress, were used in order to find out their advantages and disadvantages and to help develop a better recovery process of heavy metals from MSWFA in terms of treatment of the waste material. Hydrochloric acid leaching process was found to be most balanced among the evaluated processes. It showed superiority on energy consumption, process cost estimation, and study progress. On the other hand, despite of its excellency in process efficiency, chloride evaporation process was most unfavorable mainly due to heavy energy dependence. Biological process, with huge potential of cost reduction, was concluded to be the second best process.

Effect of Leachate Recirculation on Settlement and Leachate Generation of Municipal Solid Waste from Landfill Lysimeter

The objectives of this study are to determine the settlement and leachate generation from landfill lysimeters of municipal solid waste. Two identical lysimeters with a diameter and height of 0.70 m and 2.40 m were prepared, respectively. The lysimeters were operated with and without leachate recirculation treatment. The settlement and leachate generation were quantified daily. The analysis of settlement was conducted by using hyperbolic function and curve fitting. Based on the experiments result, it is observed that garbage pile settlement in lysimeter treated with leachate recirculation （L-2） is higher than without recirculation treatment （L-1） as showed by the hyperbolic function and curve fitting result. The ultimate settlement （S_wlt） for L-1 and L-2 that used hyperbolic function were 0.487 m and 0.53 m, respectively. Meanwhile （S_wlt） that using curve fitting resulted 0.74 m, and 0.68 m for L-1 and L-2, respectively. The lysimeter which treated with leachate recirculation treatment showed a higher leachate height than without the treatment.

Effect of Leachate Recirculation on Characteristics of Leachate Generation of Municipal Solid Waste from Landfill Lysimeter

The objectives of this study are to determine the characteristics of leachates generated from landfill lysimeters of municipal solid waste. Two lysimeters with diameter and height of 0.70 and 2.40 m, respectively, were prepared. The lysimeters were operated with and without leachate recirculation. The leachate produced were quantified and characterised every day for the quantity, pH and ORP （oxidation reduction potential）. Meanwhile, the BOD and COD parameters were characterised every once week. Based on the data of experimental results that the lysimeter with a recirculation gave positive effects on the degradation of waste in landfills, that is the degradation process becomes faster. This is indicated by the quantity and quality of leachate generated. The lyisimeter conducted with recirculation of leachate shew the quantity of leachate generated larger than the lysimeter without recirculation. While the quality of the leachate includes pH, ORP, made it shown that the degradation process is faster. These results operations, especially for young waste. BOD and COD indicate that leachate recirculation on lysismeter suggest that leachate recirculation can be performed on landfills

Improving Compost Process Efficiency by Leachates Inoculation and Shredding of the Organic Fraction of Municipal Solid Waste at Bordo Poniente Composting Plant,Mexico City

Management of MSW(Municipal Solid Waste)is a major downside in most of the biggest cities.The composting of the organic fraction of MSW is one of the oldest and simplest ways of organic waste stabilization.It is a self-heating biological conversion that generates appropriate finished merchandise such as soil conditioner or fertilizers.Mexico City generates about 12,500 ton/day of MSW,44%of it is food scraps and yard trimmings which are the OFMSW(Organic Fraction of Municipal Solid Waste),2,500 ton/day of it is composted at the BPCP(Bordo Poniente Composting Plant)yielding 500 ton/day of compost.The purpose of this study was to evaluate three treatments to accelerate the composting process,so eventually the city could increase the amount of the OFMSW at BPCP.We compared three different treatments;one of them showed a significant reduction in time of the composting process(p≤0.05)i.e.,it took less time to reach the thermophilic stage,maturity and stabilization phases.Maturity was achieved at 35 days and 60 days to stabilize.We conclude that shredding the feedstock plus leachate inoculum addition at the beginning of the process,reduces the composting time in about 61%with respect to the time it takes at the BPCP,where lasted 90 days.

Effect of Moisture on Partitioning of Heavy Metals in Incineration of Municipal Solid Waste

The effect of moisture in municipal solid waste (MSW) on partitioning of lead (Pb), zinc (Zn), copper (Cu) and cadmium (Cd) was studied in a laboratory tubular furnace by using simulated MSW. The moisture in MSW influences heavy metals in following ways, to increase the moisture in flue gas and decrease the combustion temperature, to prolong the combustion time, and to prolong the releasing time of volatiles with the furnace temperature decreased by increasing the moisture. The volatilization of Pb, Zn and Cd was enhanced by increasing the moisture in MSW because of the prolonged combustion time. For Pb and Zn, the combustion time was important at higher temperature, while for Cd, it was important at low temperature. The moisture content showed slight effect on Cu partitioning. When extra chlorine was added to MSW, such as 1%PVC + 0.5%NaCl, the volatilization of Pb, Zn and Cu was enhanced by increasing the moisture because water evaporation reduced the temperature and increased devolatilization time. At higher temperature, NaCl tends to decompose and generates more free chlorine, producing more metal chlorides. Since Cd is a strong volatile heavy metal in MSW, the effect of moisture content on its volatilization is less than that of Pb, Zn or Cu during the MSW incineration.

Minimizing N_20 fluxes from full-scale municipal solid waste landfill with properly selected cover soil

Municipal solid waste landfills emit nitrous oxide （N2O） gas. Assuming that the soil cover is the primary N2O source from landfills, this study tested, during a four-year project, the hypothesis that the proper use of chosen soils with fine texture minimizes N2O emissions. A full-scale sanitary landfill, a full-scale bioreactor landfill and a cell planted with Nerium indicum or Festuca arundinacea Schreb, at the Hangzhou Tianziling landfill in Hangzhou City were the test sites. The N2O emission rates from all test sites were considerably lower than those reported in the published reports. Specifically, the N2O emission rate was dependent on soil water content and nitrate concentrations in the cover soil. The effects of leachate recirculation and irrigation were minimal. Properly chosen cover soils applied to the landfills reduced N2O flux.

Microstructures and thermal properties of municipal solid waste incineration fly ash

To analyze the feasibility of utilization of thermal technology in fly ash treatment, thermal properties and microstructures of municipal solid waste incineration （MSW1） fly ash were studied by measuring the chemical element composition, specific surface area, pore sizes, functional groups, TEM image, mineralogy and DSC-TG curves of raw and sintered fly ash specimens. The results show that MSWI fly ash particles mostly have irregular shapes and non-typical pore structure, and the supersonic treatment improves the pore structure; MSWI fly ash consists of Such crystals as SiO2, CaSO4 and silica-aluminates, and some soluble salts like KCl and NaCl. During the sintering process, mineralogy changes largely and novel solid solutions are produced gradually with the rise of temperature. Therefore, the utilization of a proper thermal technology not only destructs those persistent organic toxicants but also stabilizes hazardous heavy metals in MSWI fly ash.

Polychlorinated dibenzo-p-dioxins and dibenzofurans in flue gas emissions from municipal solid waste incinerators in China

Polychlorinated dibenzo-p-dioxins and furans （PCDD/Fs） emissions in flue gas from two types of municipal solid waste incinerators （MSWIs） most commonly used in China were investigated in this study. The selected incinerators include two grate-type MSWIs： MSWI-A （350 t/d） and MSWI-B 050 t/d）, and two fluidized bed MSWIs： MSWI-C （400 t/d） and MSWI-D （400 t/d）, which are all equipped with semi-dry lime scrubber and bag filter except MSWI-D equipped with cyclone and wet scrubber （WS） as air pollutant control device （APCD）. Results indicated that the emission concentration and the international toxic equivalents （I-TEQs） of the PCDD/Fs from the stacks were in the range of 1.210-10.273 ng/Nm^3 and 0.019-0.201 ng I-TEQ/Nm^3, respectively. They were greatly lower than the emission regulation standard of PCDD/Fs in China （1.0 ng I-TEQ/Nm^3）. However, only the PCDD/Fs emission level from MSWI-C was below 0.1 ng I-TEQ/Nm^3. Although the homologue profiles were distinct, the contributions of the 2,3,7,8-subsituted congeners to the total I-TEQ were similar among all the investigated MSWIs. Two major 2,3,7,8-substituted congeners, 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDD, account for 47% and 9% （average values） of the total I-TEQ values, respectively. The correlation between PCDD/Fs levels and composition of flue gas was also discussed.

Effect of leachate inoculum on biopretreatment of municipal solid waste by a combined hydrolytic-aerobic process

The biopretreatment of municipal solid waste by a combined hydrolytic-aerobic process has become of great interest for biostabilization or biodrying. The study aimed at investigating the effect of leachate inoculurn on the biopretreatment. During the hydrolytic stage, the inoculum addition at the ratio of leachate to waste （LWR） of 5% and 7% stimulated the start-up of hydrolysis and enhanced the hydrolysis rate by 27.4% and 24.2%, respectively; whereas the inoculation at LWR of 1% had almost no effect on the hydrolysis rate and the inoculation at LWR of 10% reduced the hydrolysis rate by 12.7%. During the subsequent aerobic stage, the inoculations at LWRs greater than 5% decreased organics degradation rate. As a whole, compared with none inoculation, the total degradation rates of organics for inoculating trials at LWRs of 5%, 7% and 10% decreased by 14.5%, 14.3% and 32.7%, respectively. Correspondingly, their net water removal rates were reduced by 4.4%, 5.8% and 19.0%. The inoculation at LWR of 1% could not significantly affect the biopretreatment. The inoculum addition at LWR of 5% and 7% could shorten hydrolytic stage and thus accelerate the whole combined process. Moreover, the inoculations at LWRs greater than 5% were favorable for lignocelluloses degradation.

Mechanism of high concentration phosphorus wastewater treated by municipal solid waste incineration fly ash

The mechanism of removing phosphate by MSWI(municipal solid waste incineration)fly ash was investigated by SEM(scanning electron microscopy)with EDS(energy dispersion spectrum),XRD(X-ray diffraction),FT-IR(Fourier transform infrared spectroscopy),BET(specific surface area),and BJH(pore size distribution).The results indicate that the removal rate of phosphate(100 mg/L)in 50 mL phosphorus wastewater reaches at 99.9% as the dosage of MSWI fly ash being 0.9000 g under room temperature.The specific surface area of MSWI fly ash is less than 6.1 m2/g and the total pore volume is below 0.021 cm3/g,suggesting that the absorption capacity of calcite is too weak to play an important role in phosphate removal.SEM images show that drastic changes had taken place on its specific surface shape after reaction,and EDS tests indicate that some phosphate precipitates are formed and attached onto MSWI fly ash particles.Chemical precipitation is the main manner of phosphate removal and the main reaction is: 3Ca2++2 PO4 3-+xH2O→Ca3(PO4)2↓·xH2O.Besides,XRD tests show that the composition of MSWI fly ash is complex,but CaSO4 is likely to be the main source of Ca2+.The soluble heavy metals in MSWI fly ash are stabilized by phosphate.

Quick start-up of EGSB reactor treating fresh leachate of municipal solid waste

An expanded granular sludge bed （EGSB） reactor inoculated with anaerobic granular sludge was started up with its COD removal performance, self-balancing of pH, biogas production rate and characteristics of the granular sludge during the start-up period being investigated. The results indicated that the EGSB reactor can be started up successfully in 27 d by increasing the organic loading rate rapidly. The removal efficiency of COD was maintained above 93% with influent COD concentration of 25 000 mg/L and OLR of 37.94 kgCOD/（m 3 ·d）. The EGSB reactor with good pH self-balancing could be fed with fresh leachate of low pH value （4 5）. The biogas production rate was closely related with OLR and COD reduction. Every gram of COD fed （consumed） to the reactor produced 0.34 L STP （0.36 L STP ） biogas with 0.21 L STP （0.23 L STP ） methane. Thus, 65% 70% of the produced biogas was methane. Sixty one percentage of COD fed to the reactor was converted to methane, another 33% was converted to biomass by metabolism, and the other 6% was left in the liquid phase. The specific methanogenic activity （SMA） of the granular sludge had increased by 92% after 27 d dynamic incubation. The granular sludge in the reactor had good settlement performance with majority diameter of 1 2 mm.

Porous Structure of Municipal Solid Waste Incineration Bottom Ash in Initial Stage of Landfill

For quantitative estimation of the intra-layer porous structure in the initial stage of landfill formation with municipal solid waste incineration (MSWI) bottom ash, the water absorption of individual MSWI bottom ash particles was measured under still-water, degassed, and agitated conditions. The ratio of the water absorption rate found for the still-water procedure to the effective absorption capacity which was the one under degassing was 35.2%. In the water flow experiment of a column filled with MSWI bottom ash, the true density of the bottom ash was higher after water flow than before, which indicated that dissolution of the soluble components of the bottom ash particle surfaces resulted in a loss of apparent particle volume that more than offset the accompanying weight loss. The volume-based water absorption rate found for the bottom ash particles following 50 mL/h water flow through the column, as a ratio to the effective absorption capacity was about 51.8% of the effective absorption capacity. In a landfill layer comprised of MSWI bottom ash, it was suggested that some regions of the ash particle interiors underwent almost no contact with water.

HVAC Design Strategies for Municipal Waste Incineration Power Plants

In recent years,relevant government departments have achieved the goal of reduction and harmless application through the development and implementation of municipal waste incineration power plants,in order to advocate ecological and environmental protection.At present,in order to further achieve the goal of sustainable development,municipal waste incineration power plants have actively responded to the national call and requirements as well as made overall arrangements for the energy-saving design and optimization design of their internal system.Therefore,with the concept of sustainable development,this paper studies and analyzes the problems of the HVAC design as well as suggests related strategies for municipal waste incineration power plants in order to provide relevant reference.