Municipal Solid Waste Combustion Research Articles

Co-processing of raw and washed air pollution control residues from energy-from-waste facilities in the cement kiln

Co-processing of industrial wastes as alternative raw materials in cement manufacture is an example of industrial symbiosis for improved material resource efficiency. Since co-processing introduces impurities from wastes, such as air pollution control residue (APCR) from municipal solid waste combustion, into the cement kiln, a better understanding of their environmental impacts and effects on cement manufacturing and quality is needed. Portland cement clinkers containing 5–35% raw or 5–34% washed APCR were prepared, with formation of all typical minerals, but with effects on clinkering reactions, and increased 2CaO·SiO2 and decreased 3CaO·SiO2 and 3CaO·Al2O3. Raw APCR affected the shape of the 2CaO·SiO2 and 3CaO·SiO2 grains, and cement paste from clinker made with 35% APCR exhibited negligible 28d strength. Pastes from the clinkers with lower contents of APCR or washed APCR had strengths that were lower than that of the control at 7d, similar at 28d (∼90 MPa) and higher at 6 m (up to 120 MPa), consistent with their 2CaO·SiO2 and 3CaO·SiO2 contents. Utilization of minerals in APCR thus comes with a trade-off against cement quality. Volatilisation of S, Cl, Pb was reduced by washing, which fully eliminated volatilisation of Zn. Zn was found mainly in the interstitial phases of the clinker, in solid solution in 4CaO·Al2O3·Fe2O3 or 3CaO·Al2O3. Further investigation is required to determine whether Zn and other incorporated elements may be released from the cement paste when these phases react with water. APCR co-processing may reduce CO2 emissions by avoiding CaCO3 decomposition, but this is an uncertain benefit, which may be outweighed by the detrimental effects of APCR alkalis, Cl, S and metals on cement production and quality. Life cycle environmental impacts associated with washing, and dispersal of contaminants in the built environment through construction materials, are additional concerns.

Spatial distribution, patterns and source contributions of POPs in the atmosphere of Great Mendoza using the WRF/CALMET/CALPUFF modelling system

Abstract Global monitoring of Persistent Organic Pollutants (POPs) has allowed the knowledge of levels and distribution around the world as well as the understanding of its transport through the atmosphere. However, there are still some gaps in this regard, especially in some locations, as the case of Great Mendoza, a medium-sized urban area located in the center-west of Argentina. In this work, the WRF/CALMET/CALPUFF modeling system was used to estimate airborne levels of four families of POPs (PCBs, PBDEs, DDTs and HCB) in the study area. The model was validated from measured data obtained from eleven sites using passive air samplers with polyurethane foam disks (PUFs), subsequently analyzed by GC-ECNI/MS. Considering both sets of data, measured and simulated airborne concentrations, five statistical performance metrics were calculated for each family of POP [Mean bias error, (MBE), Fractional Bias (FB), Normalized Mean Square Error (NMSE), Factor of two (Fa2) and Pearson correlation coefficient (r)]. Results exhibited a good agreement between modeled and measured data, showing that WRF/CALMET/CALPUFF modeling system predicts POPs airborne concentrations with reasonable accuracy at a local scale. Model output was used to examine the relative source contribution to ground-level concentrations and to assess the spatial variability of the studied POPs in the study area. Source apportionment showed the prevalence of emissions from open burning of municipal solid waste (ranging from 9% to 90%) on the simulated atmospheric concentrations. HCB presented the lowest mean contribution from this activity (37%) but the highest variability (SD = 20%), followed by PCBs (69 ± 9%), and PBDEs (84 ± 4%). The spatial pattern obtained from simulations exhibited that both, lowest and highest levels predicted by the model, occurred in areas where no samples were taken, suggesting that the real gradient in the POPs air concentrations would be much greater than those reflected by measured data. This work highlights the usefulness of the implementation of an atmospheric dispersion model, not only in the study of air quality and exposure levels but also as a tool for the proper design of monitoring networks, taking into account the time and cost that sampling campaigns take, and the conclusions that are intended to be made from the analysis of the obtained data.

Video Based Combustion State Identification for Municipal Solid Waste Incineration

As a means of secondary utilization of resources, waste incineration power generation has received more and more attention in recent years. However, due to various uncertainties, municipal solid waste(MSW) combustion is unstable. Owing to the large time-delay from the combustion state to conventional process measurements, it is difficult to reflect the combustion state of the incinerator. This paper uses a combustion video stream to identify the combustion state in real-time. The PCA-k-means clustering method is proposed to cluster different combustion states to distinguish abnormal flames from normal ones, which do not need any operators’ attention. Based on the clustering, alarms on abnormal combustion states can be implemented to alert an operator to adjust incinerator operation conditions so that the desired combustion state can be achieved.

Conversion of high-ash microalgae through hydrothermal liquefaction

Natural microalgae (NM, Scenedesmus) cultivated by utilization of exhaust gas from a municipal solid waste combustion power plant were used for the biofuel production through hydrothermal liquefaction (HTL).

Comparison of energy produced from waste by removing its different components: A case study of the waste landfill in Tehran

AbstractIn developing and populated cities such as Tehran, a massive amount of municipal solid waste (MSW), both wet and dry, is transferred to landfills daily. Combustion is one of the most common methods of using mixed waste energy from the past to the present. The Dulong formula is widely used to calculate the energy released from MSW combustion. According to the constituent components of Tehran MSW, removing food waste leads to an increase in energy potential, which will be a suitable condition for energy production. In this work, the energy derived from the combustion of mixed and separated dry MSW generated in Tehran was calculated using the experimental Dulong formula and tables in Integrated Solid Waste Management (Tchobanoglous et al. 1993, McGraw‐Hill). The Dulong formula indicates that the use of Tehran mixed MSW (without separating materials for recycling) as a fuel source yields 8,966.40 KJ/kg while the use of Tchobanoglous et al. (1993) tables can generate 8,236 kJ/kg. By removing food waste and recyclable materials, the potential of energy production changes to 22,047 kJ/kg using the Dulong formula and 16,207 kJ/kg and the Tchobanoglous et al. (1993) tables. It indicates increase by 1.46 times and 46%, respectively. Regarding the 200‐ton capacity of the Tehran waste incinerator, the Dulong formula indicated generation of 4,409 MJ/day energy, and the Tchobanoglous et al. table presents 3,241 MJ/day. Therefore, considering that Tehran generates more than 4,000 tons of reject waste daily, it can easily be converted to energy rather than landfilled. This can alleviate the problem of buying land and construction of landfills and leachate generation.

Study of the physical-chemical characteristics of non-food solid waste combustion

The ignition and combustion processes of six non-food municipal solid waste (MSW) samples of different type were studied. The samples of wood waste, rubber, leather, cardboard, textile and plastic were put into the combustion chamber at a temperature of 600 °C in air medium at atmospheric pressure. The observations were carried out by means of high-frequency video imaging of the combustion process. Based on the obtained results the characteristic times of the ignition delay, combustion of volatiles and carbon residue were defined. The highest values of ignition delay and combustion of the carbon residue times were obtained for rubber sample and were 11.3 and 285 s, respectively. Significant correlation was found between the time of volatiles and carbon residue combustion and the fixed carbon content of the sample: the higher the Cd content, the higher value of respective time. The concentration peaks of the gas-phase products release during combustion of non-food MSW were presented as well.

Characteristics of Heavy Metal Pollutants of PM2.5 from Open Burning of Municipal Solid Waste (MSW) and the Associated Exposure Health Risks

The characteristics and health risk assessment for heavy metal pollutants in PM2.5 discharged from the open burning of municipal solid waste (MSW) in different functional areas were studied using a flue gas diluted sampling system. The two common open burning modes of barrel and natural pile-up burning were considered. The results show that the concentration of zinc (Zn) was the highest among the heavy metals produced by five different components of waste incineration, ranging from 1324.03 to 3703.12 mg·kg-1. The concentration of cadmium (Cd) was the lowest, ranging from 20.25 to 63.68 mg·kg-1. According to the geo-accumulation index, lead (Pb), Zn, arsenic (As), and Cd were highly polluted in the measured MSW samples, and all four of these metals reached moderate or higher levels of pollution under natural pile-up burning methods. The geo-accumulation index of Cd was much higher than 5. The results of the human health risk assessment showed that non-carcinogenic risk values for 8 heavy metals (Pb, Zn, Cu, Mn, As, Cd, Cr, and Ni) by respiratory exposure were less than 1, which is within the safe range. For natural pile-up burning, the total non-carcinogenic risk values for As and Pb for children were higher than 1, indicating a non-carcinogenic risk. The carcinogenic risk values for four carcinogenic elements (As, Cd, Cr, and Ni) were less than 1.0×10-4, but still represented a low potential carcinogenic risk under exposure for long periods of time.

Contamination of heavy metals and metalloids in biomass and waste fuels: Comparative characterisation and trend estimation

The use of contaminated biomass and waste fuels is essential for waste management, waste to energy (WtE) and mitigating carbon emissions. The contamination of heavy metals and metalloids is specially concerned by environmental regulation and waste to energy processes. In this study, comparative characterisation is performed for three typical contaminated biomass and waste fuels. i.e. recycled woods, combustible municipal solid waste, and industrial and commercial wastes. The contamination characteristics are further analysed using statistical methods (e.g. significance, correlation, profile, and principal component analyses) to identify specific contamination features, relations among the contaminants and potential contamination sources. Contamination trend is estimated based on the continuously monitoring fuel qualities, the driving forces for regulating and reduction of the contaminations, and potential changes in major contamination sources. The comparative characterisation combined with statistical analyses provides a better way to understand the contamination mechanisms. The approach can also relate the fuel contamination with the contamination sources and their changes for trend estimation. Generally, the toxic heavy metals and metalloids are expected to be significantly reduced due to stricter regulations, but there is no general trend for the reduction of other metals and metalloids because of the complicated changes in contamination sources and waste recycling streams in the near future.

Comparison of the Characteristics of Fly Ash Generated from Bio and Municipal Waste: Fluidized Bed Incinerators.

European solid waste incinerator plants still primarily use grate furnace technology, although circulating fluidized bed (CFB) technology is steadily expanding. Therefore, few investigations have reported on the environmental assessment of fly ash from fluidized incinerators. This research project aims to integrate information on fly ash derived from the combustion of municipal solid waste (FA1) and biomass (FA2) in fluidized bed incinerator facilities. Fly ash samples were comparatively analyzed by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES) to study the mineralogy, morphology, total heavy metal content, and leaching behavior, respectively. The analysis revealed that the two types of fly ash differ in their characteristics and leaching behavior. The concentration of most of the heavy metals in both is low compared to the literature values, but higher than the regulatory limits for use as a soil conditioner, whereas the high contents of Fe, Cu, and Al suggest good potential for metal recovery. The leaching ability of most elements is within the inert waste category, except for Hg, which is slightly above the non-hazardous waste limit.

An investigation of an oxygen-enriched combustion of municipal solid waste on flue gas emission and combustion performance at a 8 MWth waste-to-energy plant

This paper describes the effect of oxygen-enriched combustion (OEC) on the flue gas emission and combustion performance of municipal solid waste (MSW) in a full-scale waste incineration plant without flue gas recirculation. Input gas with different oxygen concentrations (21%, 24%, 27%) were supplied into the MSW grating furnace with a capacity of 150 t/d to evaluate the effect of inlet oxygen content on the emissions of NOX, NO, SO2, HCl as well as dioxins (PCDDs and PCDFs). Combustion temperature in the incinerator, unburnt rate and thermal efficiency were also examined to assess the combustion performance under OEC condition. Results showed that the amount of SO2 and HCl decreased to lower levels during OEC condition, while the average concentrations of NOX and NO increased with increase in oxygen content of input gas. Dioxins (PCDDs and PCDFs) in both flue gas and fly ash were highly increased elevated by the oxygen intake, especially for PeCDFs and HxCDFs. The average temperature in three grates of incinerator increased as oxygen concentration increased, while the unburnt rate gradually decreased, indicating a slight improvement of MSW thermal efficiency and more complete combustion under OEC condition.

Urban air pollution from the open burning of municipal solid waste

Urban air pollution from the open burning of municipal solid waste

Estimation of Municipal Solid Waste (MSW) combustion enthalpy for energy recovery

The global challenges of climate change have been compounded by an unprecedented level of environmental pollution consequent upon the municipal solid waste, MSW generation. Recent advances by researchers and policymakers are focused on sustainable and renewable energy sources which are technologically feasible, environmentally friendly, and economically viable. Waste-to-fuel initiative is therefore highly beneficial to our environment while also improves the socio-economic well-being the nations. This current study introduces an adaptive neuro-fuzzy inference systems (ANFIS) model optimised with Particle Swarm Optimisation (PSO) algorithm aimed at predicting the enthalpy of combustion of MSW fuel based on the moisture content (H2O), Carbon, Hydrogen, Oxygen, Nitrogen, Sulphur, and Ash contents. This model was trained with 86 MSW biomass data and further tested with a new 37 data points. The developed model was observed to performed better in term of the accuracy when compared with other existing models in the literature. The model was evaluated based on some known error estimation. The values of Root Mean Squared Error (RMSE), Mean Absolute Deviation (MAD), Mean Absolute Percentage Error (MAPE), Log Accuracy ratio (LAR), Coefficient of Correlation (CC) were 3.6277, 22.6202, 0.0337, 0.8673 respectively at computation time (CT) of 36.96 secs. Regression analysis was also carried out to determine the level of correlation between the experimental and predicted high heating values (HHV).

REDUCTION OF NATURAL GAS CONSUMPTION AND REDUCTION OF EMISSIONS WITH COMBUSTION PRODUCTS IN MUNICIPAL HEAT SUPPLY

The technical solutions are proposed to reduce the consumption of natural gas, as well as to reduce emissions with combustion products in the municipal heat supply systems:
 - New constructions of water-tube and water-fire-tube boilers with improved technical, economic and environmental characteristics have been developed. Replacing of old boilers with these boilers within Ukraine will provide an economic effect of about 100 thousand tons of fuel equivalent per year. NOx reduction will be up to 35%;
 - The new temperature mode for heating networks 115/70 oС has been developed, which provides the amount of heat that is adequate to the needs of consumers, and is appropriate for use in cities of the country from an economic point of view. However, the implementation of such reduced temperature mode requires a corresponding change in the general requirements when issuing "Technical Specifications" for connection to district heating systems, necessitates changes in the temperature mode values in other documents, for example the general plan of the city, as well as the possible need to change the calculated heat loads in concluded contracts for heat supply to consumers. Nevertheless, the correction of temperature modes of cities should be considered as one of the possible measures to improve the energy efficiency of heat supply systems;
 - The expediency of partial replacement of natural gas in the municipal heat supply systems of large cities of Ukraine with municipal solid waste (MSW) has been proved. The ways of improving the efficiency of mixed MSW combustion in conditions of country, including the extraction of "wet" biowaste from the total mass of mixed MSW with using a separate collection. are determined;
 - To achieve compliance with the new more stringent European environmental standards, the highly efficient devices for cleaning combustion products from particulate matter and sulfur oxides have been developed. The efficiency of dust removal in centrifugal filters is 90...98%, in cyclone dust collectors - 90...93%. Desulfurization efficiency is up to 50%.

Study on corrosion kinetics of 310H in different simulated MSW combustion environment. The influence of SO2 and H2O on NaCl assisted corrosion

In this study, the corrosion kinetics of alloy 310H with and without each of NaCl, H2O-vapor, and SO2 under an oxidizing environment at 500 °C was investigated and the corrosion characteristics in each exposure were compared. The contribution of NaCl, H2O, and SO2 to the corrosion rate was calculated and the corrosion mechanisms in each condition were characterized by means of ex-situ and in-situ thermogravimetric mass-gain measurements, SEM/EDS, XRD, XPS, and theoretical calculations. The contribution was in the order of NaCl>H2O > SO2. Corrosion was linear in the absence of SO2 while in the absence of NaCl, corrosion displayed a multi-stage behavior.

Theoretical and experimental study of gas-phase corrosion attack of Fe under simulated municipal solid waste combustion: Influence of KCl, SO2, HCl, and H2O vapour

Combustion of municipal solid waste (MSW) in waste-to-energy plants have an advantage of energy recovery. However, corrosion of super-heaters induced by KCl, H2O, and S in MSW is the major problem limiting the efficient utilisation of MSW. Corrosion reactions of metals are not well understood at molecular/atomic levels, regarding how they evolve. This situation emphasizes the need to understand the reaction pathways and their reaction rates in order to identify operating conditions that reduces the corrosion rates. In this study, a novel kinetic model for the gas-surface reactions of KCl, S, and H2O with Fe was developed. The rate constants for the elementary reactions were estimated based on density functional theory and conventional transition state theory computations. Fe-clusters (Fen, n = 2–4) were used in estimating the kinetic constants of the surface reactions. Reaction model was used to predict the corrosion behaviour of Fe in simulated flue-gas of combustion of MSW at 500 °C and 4 bars. A perfectly stirred reactor code of chemkin-PRO was employed for the predictions. Due to the novel nature of the mechanism, independent experimental results from the literature and experimental results from well-controlled conditions at 500 °C and 4 bars for 50 h were used to validate model predictions. Comparison of model predictions and all experimental results showed good agreement. The concentration of KCl accelerated the corrosion of Fe by a parabolic behaviour while SO2 between 300–500 ppm showed the lowest mass loss. Water vapour of ∼10 vol% was the critical point at which above corrosion rate was accelerated.

A framework for developing and projecting GHG emission inventory and preparing mitigation plan: A case study of Delhi City, India

To provide a framework for a systematic study to address the issues of GHG emissions, City of Delhi was selected. The study employs state-of-the-art analytical techniques to develop GHG emission inventory, its forecasting and preparing mitigation plan. The total carbon dioxide equivalent (tCO2e) emission was estimated at 41.26 million tonnes (Mt.) for the year 2014. The major contributors were power plants (46.8%), vehicles (29.7%), municipal solid waste burning (7.6%) and domestic cooking (6%). To achieve a continuous reduction, targets were set for two phases in the years, 2022 and 2030. The emissions were projected by considering growth in population, GDP, vehicles on the road and other activities; 63.64 (year 2022) and 79.19 (year 2030) Mt. tCO2e. The electricity consumption showed the highest increase followed by vehicles. Based on emission intensity (ratio of emission quantity to GDP), the target emission in the year 2030 was 54.74 Mt. tCO2e. The control-plan primarily comprised use of renewable sources, energy efficient devices and introduction of electric vehicles. Electricity generation by renewable sources (40% by 2030) could result in a reduction of 25.6 Mt. tCO2e (32% of tCO2e). It is shown systematic emission estimates and mitigation planning can achieve the target emission.

Numerical simulation on operating parameters of SNCR process in a municipal solid waste incinerator

The combustion of municipal solid waste and ammonia based selective non-catalytic reduction (SNCR) process in a moving-grate incinerator was simulated based on the computational fluid dynamics method. The combustion characteristics, overall temperature level, NOX emission, NOX removal efficiency and NH3 slip were analyzed to determine the optimal SNCR injection positions, injection speeds and injection ratios. Results showed that there was no difference in the furnace temperature and O2 concentration under different SNCR injection positions, speeds and ratios. Moreover, the temperatures of SNCR injection zones were in the SNCR reaction temperature range of 800 °C–1100 °C under different SNCR injection positions, speeds and ratios. Further, injection positions strongly affected NOX removal efficiency and NH3 slip. Ammonia should be injected in layer and in the front region within the suitable temperature range as much as possible. Furthermore, SNCR injection speed had an optimal speed, which was 13.80 m/s with NOX removal efficiency of 51.50% and NH3 slip of 11.08 mg/Nm3. In addition, there was a strong impact on NOX removal efficiency and NH3 slip under different SNCR injection ratios. Increasing the ratio of SNCR-1 (the first row of SNCR) was conducive to the improvement of NOX removal efficiency. The best injection ratio was the ratio of 6:3:1 (SNCR-1:SNCR-2 (the second row of SNCR):SNCR-3 (the third row of SNCR)), where NOX removal efficiency was 53.10% and NH3 slip was 8.43 mg/Nm3.

Transformation and migration of cadmium during chemical-looping combustion/gasification of municipal solid waste

The transformation and migration of cadmium during chemical-looping combustion (CLC) and gasification (CLG) of the synthetic municipal solid waste (SMSW) was investigated in a tubular furnace. Both copper-based and iron-based oxygen carriers (OCs) can make elemental cadmium (Cd (g)) into cadmium oxide (CdO) at 850 °C, but their complete reduction products do not have this ability. Cadmium was distributed mainly in the bed material during CLC, but distributed mainly in the fly ash during CLG. After 2 min of reaction, approximately 90% of the cadmium in the bed material distributed in the OC particles, indicating that large amount of cadmium would volatilize from the SMSW particles and migrate to the OC particles at the initial stage of CLC and CLG. As the reducing gas generating later may restore CdO to Cd (g) again during CLG, the cadmium migrating to the OC particles was detached gradually. A two-step-transformation and migration mechanism for cadmium during CLC and CLG was proposed. After five successive cycles of the CLC process, the concentration of cadmium in the OC particles increased linearly from 7.1 mg/kg to 33.3 mg/kg with an average capture efficiency of 85%, while after just one cycle of the CLG process, the high concentration of the cadmium in the OC particles can be removed efficiently. Overall, the cadmium in MSW can be captured by CLC, while be removed by CLG. Therefore, the coupling of CLC and CLG processes may provide an innovative and efficient control, even recycling technology for the cadmium in MSW.

An evaluation of effects of operational parameters on NOx emissions through detailed chemical kinetics simulations

Abstract NOx emissions from biomass and Municipal Solid Waste (MSW) combustion is a great concern. Technologies for reducing NOx emissions based on flue gas cleaning using e.g. Selective Non-Catalytic Reduction (SNCR) or Selective Catalytic Reduction (SCR) are well known. However, limiting NOx emissions by primary measures is an attractive opportunity, avoiding or limiting the use of costly secondary measures. Many factors influence the NOx emission level from biomass and MSW combustion plants, like fuel-N content and speciation, and operating parameters as air distribution and staging, flue gas recirculation, temperature and residence time. In this work a recent detailed chemical kinetics mechanism is used to investigate the NOx reduction potential by staged air combustion at different operational conditions, using two ideal plug flow reactors connected in series. This enables revealing a kinetics limited reduction potential, as a guideline for further detailed studies at targeted conditions using stochastic reactor networks or Computational Fluid Dynamics (CFD). The results show, for demolition wood as fuel, a large NOx reduction potential, as high as above 95% total fixed nitrogen reduction at theoretically optimum conditions. Through reaction path analyses the main reaction pathways and reactions are identified. Comparison with experimental results from grate combustion units is made. Finally, a comparison with earlier and less extensive detailed chemical kinetics mechanisms is made, to check for significant differences and assess the reasons for those. The final goal would be to arrive at computationally effective reduced chemical kinetics mechanisms that could be applied in CFD simulations of real biomass and MSW combustion plants, to arrive at improved operational conditions or improved design.

Cytotoxicity comparison between fine particles emitted from the combustion of municipal solid waste and biomass.

Fine particles (PM2.5) emitted from municipal solid waste incineration (MSWI) contain high amounts of toxic compounds and pose a serious threat to environment and human health. In this study, entire particles as well as extracted water-soluble and -insoluble fractions of PM2.5 collected from MSWI and biomass incineration (BMI) were subjected to physiochemical characterization and cytotoxic tests in A549 and BEAS-2B cells. MSWI PM2.5 had higher contents of heavy metals (including Pb, Zn, and Cu) and dioxins (PCDD/Fs) than did BMI PM2.5. The metals were enriched in the water-insoluble fraction, as measured by inductively coupled plasma-atomic emission spectrometry. BMI PM2.5 had a higher content of endotoxin, which was also enriched in the water-insoluble fraction. MSWI PM2.5 caused more serious cell injuries, as indicated by the lower viability, higher ROS generation, and DNA damage, whereas BMI PM2.5 presented higher pro-inflammatory potential, as indicated by increased mRNA levels of interleukin 6. Normal human BEAS-2B cells were more sensitive than A549 cells in all these tests. Toxic effects caused by MSWI and BMI PM2.5 were mostly attributable to their water-insoluble fractions. Our results indicate different chemical and biological compositions in MSWI and BMI PM2.5 probably dominate in different toxic endpoints in vitro.