Co-combustion Of Municipal Solid Waste Research Articles

Effect of modified diatomaceous earth on the heavy metal volatilization characteristics of aged refuse co-combustion

ABSTRACT This paper investigated the adsorption performance of natural and modified diatomaceous earth (DE) for six heavy metal species (Cu, Zn, Ni, Cd, Pb, Cr) during the co-combustion of aged refuse (AR) and municipal solid waste (MSW) in a lab-scale tubular furnace. The aim was to examine the effects of temperature, sorbents, and modification methods on heavy metals’ adsorption performance. The capture rates of calcined diatomaceous earth (CDE) were higher than those of DE, especially for Ni at 700°C, whose capture rate increased to 78.6%. Modified sorbents with NaOH or Na2CO3 significantly reduced the volatility of six heavy metals at 700°C, with the volatilization rates (VR) of Ni and Zn decreasing by at least 50%. Meanwhile, for Cu, Pb, and Zn, the fixation of heavy metals in the bottom ash increased with rising the sorbents mass. However, when the combustion temperature was equal to or above 800°C, the effects of modification on the VR of Cd, Pb, and Zn diminished, except for 10 wt% DE and CDE-10%NaOH. Using NaOH-modified DE at higher temperatures increased the VR of Ni, Pb, and Zn, particularly for Ni whose VR increased by 21.13%. This work contributes to understanding DE’s control mechanism of heavy metals and investigates new heavy metal control strategies during the co-combustion of MSW and AR.

Co-combustion of municipal solid waste and hydrochars under non-isothermal conditions: Thermal behaviors, gaseous emissions and kinetic analyses by TGA–FTIR

Co-combustion of municipal solid waste (MSW) with hydrochars was proposed as an effective way for both simultaneous treatments of MSW with biomass and energy recovery. In this work, thermogravimetric analyzer coupled with Fourier transform infrared spectrometer was employed to study the (co-)combustion, gaseous emissions and combustion kinetics characteristics of MSW, hydrochars and their blends. The addition of hydrochars to MSW leads to lower burnout temperatures and the shorter combustion time. Hydrochar prepared at 200 °C (SD200) has a better co-combustion performance than hydrochars prepared at 230 (SD230) and 260 °C (SD260) in term of ignition, burnout and comprehensive combustion characteristic index, hydrochar prepared at 260 °C has a better co-combustion evenness. The addition of hydrochar to MSW changed the gaseous products emission patterns of MSW and reduced the release of CO, HCN, NO and HCl. Kissinger-Akahira-Sunose (KAS) and Flynn–Wall–Ozawa (FWO) methods were used to estimate the activation energy of MSW, SD200 and their blends, the minimum average activation energy was observed when the SD200 blending ratio was 70%, which was 75.65 kJ mol−1 by KAS and 82.12 kJ mol−1 by FWO, respectively.

Emission Characteristics and Formation Pathways of PCDD/Fs from Cocombustion of Municipal Solid Waste in a Large-Scale Coal-Fired Power Plant

This study is based on a 300 MW coal-fired power plant cocombusting 2% of MSW, focusing on the emission characteristics and formation pathway of polychlorinated dibenzo-p-dioxins and dibenzofurans ...

Stabilization of Municipal Solid Waste Fly Ash, Obtained by Co-Combustion with Sewage Sludge, Mixed with Bottom Ash Derived by the Same Plant

This study presents an innovative stabilization method of fly ash derived from co-combustion of municipal solid waste and sewage sludge. Bottom ash, obtained from the same process, is used as a stabilizing agent. The stabilization method involved the use of two other components—flue gas desulfurization residues and coal fly ash. Leaching tests were performed on stabilized samples, aged in a laboratory at different times. The results reveal the reduction of the concentrations of heavy metals, particularly Zn and Pb about two orders of magnitude lower with respect to fly ash. The immobilization of heavy metals on the solid material mainly depends on three factors—the amount of used ash, the concentrations of Zn and Pb in as-received fly ash and the pH of the solution of the final materials. The inert powder, obtained after the stabilization, is a new eco-material, that is promising to be used as filler in new sustainable composite materials.

Bottom ash derived from municipal solid waste and sewage sludge co-incineration: First results about characterization and reuse

This paper reports a complete characterization of the lowest fractions of bottom ash derived from co-combustion of municipal solid waste with sewage sludge (COBA), with the aim to suggest suitable reuse strategies of this by-product. X-Ray Microanalysis is coupled with mineralogical characterization, based on X-Ray Diffraction and Rietveld refinement, to extract information about COBA crystalline and amorphous phases. The composition of different particle size fractions shows that amount of amorphous increases with the increase of fractions sizes. In particular, the finest COBA size fraction (<300 μm) shows more leachable heavy metals (i.e. Pb, and Zn) compared to the investigated fraction with the highest sizes (1400 µm). On the basis of their composition, lowest particle size fractions show a better hydraulic behavior compared to bottom ash obtained from incineration of only municipal solid waste, suggesting possible attractive COBA applications, as for example, Portland cement substitution. In addition, COBA with size fractions in the range of 1000–1400 μm are proposed to be used to produce glass and ceramic. Finally, due to its high amount of reactive amorphous phase (about 73% for fraction size of 1400 μm) COBA is used, in combination with other by-products (coal fly ash and flue gas desulphurization residues), to stabilize municipal solid waste incinerator fly ash produced at the same incinerator plant, following the azure chemistry principle of use a waste to stabilize another waste.

Co-combustion of municipal solid waste and coal for carbon emission reduction: A bi-level multi-objective programming approach

The continuing growth in carbon emissions, which are a major contributor to climate change, highlights the need for sustainable coal-fired power generation. With a focus on carbon emission reduction, a bi-level multi-objective optimization model for co-combustion of municipal solid waste and coal under an uncertain environment is used. The model considers not only the relationship between the authority as the leader and the coal-fired power plants as the followers, but also the trade-off between social welfare and allocation satisfaction. Fuzzy theory is applied to deal the imprecise activities and observations during co-combustion. A practical case in Sichuan Province, China is given to verify the efficiency and practicality of the proposed optimization method. The ε-constraint method and Karush-Kuhn-Tucker conditions are employed to optimize the global equilibrium. Various scenarios are then analyzed and discussed, from which it is found that the decision makers can develop better strategy in accordance with the attitudes towards dioxin emissions and allocation satisfaction. This method was found to be capable of reducing carbon emissions by 6.96 ×105 tonnes and disposing of 1.28×106 tonnes of MSW compared with coal combustion alone. It also indicates that additional allocations would be given to coal-fired power plants with cleaner production. Management recommendations for both decision makers are given to provide support in achieving better MSW management strategies and realizing sustainable development. Given the complexity of co-combustion, this model cannot fully capture all parameters; therefore, a more comprehensive model that includes other toxic emissions such as trace metals is to be developed in future research.

Heavy metals chemical speciation and environmental risk of bottom slag during co-combustion of municipal solid waste and sewage sludge

Incineration of sewage sludge (SS) in waste incinerators is one of the main ways of SS disposal. In order to reuse the incineration bottom slag, chemical speciation and environmental risk of heavy metals of bottom slag during co-combustion of municipal solid waste (MSW) and SS should be evaluated. When co-combusted with SS, the proportion of mild acid-souble fraction of Cr, Cu and Zn in the bottom slag decreased, the proportion of reducible fraction and residual fraction increased. As for As, with the increase of sludge blending ratio, the proportion of mild acid-souble fraction increased, and the proportion of oxidizable fraction decreased rapidly. The degree of soil contamination by As and the ecological risk of As of MSW combustion bottom slag increased when co-combusted with SS, while that of Cr, Cu, and Zn decreased. Fitting formulas between environmental index of bottom slag and combustion condition were giving.

Co-combustion of municipal solid waste and coal gangue in a circulating fluidized bed combustor

Mixed incineration of municipal solid waste (MSW) in existing coal gangue power plant is a potentially high-efficiency and low-cost MSW disposal way. In this paper, the co-combustion and pollutants emission characteristic of MSW and coal gangue was investigated in a circulating fluidized bed (CFB) combustor. The effect of MSW blend ratio, bed temperature and excess air ratio was detailedly studied. The results show the NOx and HCl emission increases with the increasing MSW blend ratio and the SO2 emission decreases. With the increase of bed temperature, the CO emission decreases while the NOx and SO2 emission increases. The HCl emission is nearly stable in the temperature range of 850–950 °C. The increase of excess air ratio gradually increases the NOx emission but has no significant effect on the SO2 emission. The HCl emission firstly increases and then decreases with the increase of excess air ratio. For a typical CFB operating condition with excess air ratio of 1.4, bed temperature of 900 °C and MSW blend ratio of 10%, the original CO, NOx, SO2 and HCl emissions are 52, 181, 3373 and 58 mg/N m3 respectively.

Influence on gaseous pollutants emissions and fly ash characteristics from co-combustion of municipal solid waste and coal by a drop tube furnace

Co-combustion experiments of municipal solid waste and coal were carried out in a drop tube furnace at high temperature 1300 °C. The effect of different simulated municipal solid waste (SMSW) added proportion (0, 7.5, 15, 20 and 25 wt%) in the blend fuels on the characteristics of gaseous pollutants emissions, e.g. CO, HCl, SO2, NOx, and heavy metals, and fly ash were studied. The results indicated that CO and CH4 emission concentrations were at a low level under all conditions. With the increasing proportion of SMSW, the combustion efficiency decreased slightly, the HCl emission increased obviously at 25% conditions while at lower proportion conditions the change was not significant; the NOx emission concentration showed a tendency to rise first and then decrease, while the SO2 showed an exactly opposite trend; besides, Fe, Cl and S content in the fly ash increased obviously. Under all experimental conditions, only a small amount of heavy metals were emitted in the flue gas while most of the heavy metals were retained in the fly ash. The leaching results showed that Ni leaching concentration was beyond the national standard which means the fly ash needs further treatment before they can be disposed of by landfill, while the HCl, NOx and SO2 emissions can easily reach the national emission standard under the desulfurization and denitrification system operating conditions in real power plants. These findings are helpful for the further development of co-combustion with renewable energy in coal-fired incinerators, yet more investigation on heavy metal emission in fly ash is still required to be further conducted in the future.

Formation pathways of PCDD/Fs during the Co-combustion of municipal solid waste and coal

The co-combustion of simulated municipal solid waste (SMSW) and the coal in a drop-tube furnace is studied in five test cases. The concentration and signature evolution of polychlorinated dibenzo-p-dioxins (PCDD) and -furans (PCDF) in both flue gases and fly ashes are monitored at the level of individual congeners, using statistical methods. Special attention is paid to chlorophenol (CP)-route congeners, 2,3,7,8-substitution, and 1,9-substitution, to reveal the formation pathways of PCDD/Fs and the interaction between SMSW and coal. It is identified that the increase of SMSW proportion alters the major formation pathways from CP-route to chlorophenols/chlorobenzenes condensation and de novo synthesis. The coal-induced carbon enhances the adsorption capacity of fly ash particles for PCDD/Fs, yet facilitates the generation of carbon matrixes and polycyclic aromatic hydrocarbons, both of which will significantly boost the de novo synthesis with the increase of SMSW-induced chlorine and catalytic metals. Further investigations about restricting the participation of chlorine in PCDD/Fs synthesis are essential to increase the treatment capacity of MSW and to reduce the PCDD/Fs emission.

Emission Characteristics of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans from the Co-combustion of Municipal Solid Waste in a Lab-Scale Drop-Tube Furnace

Generally, coal-fired incinerators are characterized by a high combustion temperature and a well-equipped flue gas cleaning system. Co-combusting municipal solid waste (MSW) in coal-fired incinerators can reduce the emission of PCDD/Fs and help to enhance the treatment capacity of the MSW; more importantly, this approach provides a new orientation for upgrading and transitioning old coal-fired power plants. In this study, the simulated municipal solid waste (SMSW) is mixed with coal in proportions of 0 (without addition), 7.5, 15, 20, and 25 wt.% and then co-combusted in a drop-tube furnace. The PCDD/Fs emitted in both the flue gases and fly ashes from the combustion tests are well investigated. In the present study, the I-TEQ concentration of the PCDD/Fs in the flue gas can meet the emission limit (0.1 ng I-TEQ/Nm3) when MSW is co-combusted at less than 20 wt.%. The concentration of the PCDD/Fs in the fly ash is much lower than the permitting standard for disposal in sanitary landfill sites (3.0 ng I-TEQ...

Emission, distribution and toxicity of polycyclic aromatic hydrocarbons (PAHs) during municipal solid waste (MSW) and coal co-combustion

Emission and distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) were investigated during municipal solid waste (MSW) and coal combustion alone and MSW/coal blend (MSW weight fraction of 25%) co-combustion within a temperature range of 500°C–900°C. The results showed that for all combustion experiments, flue gas occupied the highest proportion of total PAHs and fly ash contained more high-ring PAHs. Moreover, the 3- and 4-ring PAHs accounted for the majority of total PAHs and Ant or Phe had the highest concentrations. Compared to coal, MSW combustion generated high levels of total PAHs with the range of 111.28μg/g–10,047.22μg/g and had high toxicity equivalent value (TEQ). MSW/coal co-combustion generated the smallest amounts of total PAHs and had the lowest TEQ than MSW and coal combustion alone. Significant synergistic interactions occurred between MSW and coal during co-combustion and the interactions suppressed the formation of PAHs, especially hazardous high-ring PAHs and decreased the TEQ. The present study indicated that the reduction of the yield and toxicity of PAHs can be achieved by co-combustion of MSW and coal.

A new theory of the creation of biomethane from aluminium-containing inorganic wastes

Energy by-products from the co-combustion of municipal solid waste with coal or biomass are monitored only in terms of oxides; the amount of metallic aluminium is not determined. When these energy by-products are deposited at landfills, the alkali metal compounds in landfill bodies undergo reactions with aluminium in the presence of water. This leads to the formation of hydrogen and its possible bioconversion into methane. The article summarises the findings of the possible development of methane and hydrogen from the ashes of 11 items of typical municipal waste containing aluminium, burned in power plants, which are then landfilled. The assessment of the new information on aluminium-waste reactions in landfill bodies and the metabolism of some bacteria may give rise to a new theory of the formation of the biomethane contained in the landfill gas.

Effects of blending hydrothermally treated municipal solid waste with coal on co-combustion characteristics in a lab-scale fluidized bed reactor

Experiments on co-combustion of municipal solid waste (MSW) and coal were conducted in a bubbling fluidized bed (BFB). The MSW sample was pretreated through hydrothermal treatment (HT) for obtaining uniform characteristics. MSW blending ratios as 10%, 20%, 30% and 50% were selected and tested at 700, 800, 900°C to verify to which extent coal can be substituted with HT MSW in terms of emissions and unburnt carbon (UC) in fly ash (FA). The results obtained in this study showed that the lowest CO and NO emissions were found at 20% and 30% HT MSW blending respectively. Moreover, the SO2 emissions decreased with the HT MSW addition and the HCl emissions were below 5ppm. Furthermore, the UC contents decreased at the mixing ratio below 30% at low temperature. Positive synergistic relationships were identified and it is possible to accept 30% MSW combustion in a coal-fired BFB reactor.

Pollutant Emission and Ash Characteristics during Co-combustion of Municipal Solid Waste and Corn Stalk

Co-combustion performance of blends of municipal solid waste with high ash content and low calorific value and corn stalk was investigated using a thermogravimetric analyzer coupled with a Fourier transform infrared spectroscopy. Ignition temperature, emissions of major gaseous pollutants, and the ash characterization were studied. The ashes of the blends were characterized with Fourier transform infrared, X-ray diffraction, and a nitrogen adsorption analyzer. The results show that SO2 and NO emission from the blends are a little higher than that from municipal solid waste. X-ray diffraction results indicate that the reaction between calcium in corn stalk and chlorine to form CaCl2 results in an HCl reduction from co-combustion. The higher surface area and pore volume of ash shows that the blends undergo complete combustion.

Combustion kinetics of sewage sludge and combustible wastes

This study estimated the kinetics of the mono- and co-combustion of sewage sludge pellets and combustible wastes such as municipal solid waste (MSW) and refuse-derived fuel (RDF). Sewage sludge was manufactured into pellets with a diameter of 8, 12, or 16 mm and a length of 30 mm. The RDF was composed of paper and plastics and was formed into pellets with a diameter of 8 mm and a length of 30 mm. MSW samples were synthesized using combustible wastes such as garbage, paper, plastics, and wood. The MSW was adjusted to have a moisture content of around 40% after shredding to under 10 mm. A laboratory-scale batch type stoker incinerator was used for the combustion and the gas composition of the flue gas was measured. The activation energy was calculated using the experimental results, and then the relation of the decomposition rate and reaction time was evaluated using the shrinking core model. The decomposition rate of the sludge pellets decreased as their diameter and moisture content increased, and the co-combustion of sludge pellets and combustible waste was affected by the amount of combustible waste. The individual combustion rates of the cylindrical sludge pellets or RDF were mainly controlled by the chemical reaction, but in the case of shredded MSW it was mostly influenced by gas diffusion. The rate for the co-combustion of sludge pellets and combustible wastes was mainly determined by the combustion rate of the combustible waste. The activation energy of the 8-mm-diameter sludge pellets was between 6.70 and 10.0 kcal/mol, according to the moisture content, but it was lower for MSW and RDF. In the case of MSW co-combustion, the reaction rate accelerated as the moisture content of the sludge pellets decreased, but it was markedly increased by the addition of RDF, regardless of the sludge moisture content.

04/02019 Co-combustion of municipal solid waste and Thai lignite in a fluidized bed: Suksankraisorn, K. et al. Energy Conversion and Management, 2004, 45, (6), 947–962

This research comparatively investigates fifteen national-level integrated municipal solid waste (MSW) management schemes and determines the most preferable MSW scheme that attaches equal importance to the environmental, economic, and social impacts. The fifteen schemes are one business as usual (BAU) scheme, seven composting- and seven biogas production-oriented schemes. All the MSW schemes rely on incinerators and refuse derived fuel (RDF) processing for waste disposal. The environmental impacts and costs are quantified by Stepwise2006 based on ecoinvent database. The economic return is evaluated based on the net present value of the construction and operation cost. The affected local community area is the indicator of public perception toward the waste disposal projects (i.e., social impact). The analytic hierarchy process (AHP) is used to determine the most preferable scheme. The results showed that MSW combustion by incineration and RDF is the main contributor of environmental impacts. The environmental costs of composting schemes were lower than those of biogas production schemes. Total environmental cost of scheme 7 (i.e., 25% recycling, 50% decomposing, 5% biogas production, two incineration plants, and seven RDF plants) is the lowest (7492.63 billion THB2020). The cash inflow of BAU is lowest and the cash outflow is highest. In comparison with the biogas production schemes, the cash inflows and outflows of composting schemes are lower. Scheme 7 is the most preferable MSW management scheme, given the highest AHP priority score (0.228). Therefore, the composting-incineration-RDF scheme (scheme 7) should be adopted to treat biodegradable and combustible waste.

Co-combustion of municipal solid waste and Thai lignite in a fluidized bed

Co-combustion of high moisture municipal solid waste (MSW) and high sulfur Thai lignite in a laboratory scale bubbling fluidized bed has been investigated. This paper presents the effects of the mass fraction of a model MSW in the fuel mixture, as against 100% lignite, on the combustion characteristics that may be inferred from temperature distributions, carbon combustion efficiency and CO and CO 2 concentrations and on the emissions of major gaseous pollutants, including CO, SO 2, NO and N 2O. The influence of excess air and secondary air on those characteristics are also discussed. The results show that within the 40% MSW fraction tested, co-combustion is characterized by enhanced combustion of volatiles in the freeboard, a lower bed temperature and a combustion efficiency drop of up to 8%. Co-combustion either increases or reduces CO emission depending on the percentage of excess air. Reduction of up to 7–18% of SO 2 is observed at the 40% MSW fraction for the range of excess air and secondary air tested. Both NO and N 2O increase slightly with increasing fraction of MSW. Within the range of experimental conditions tested, the optimum condition for co-combustion in view of combustion efficiency and CO, NO and N 2O emissions is: 20% MSW, 40% excess air and 0.2 secondary to total ratio, although the reduction of SO 2 is slightly smaller than at other conditions.