Fluidized Bed Incinerator Research Articles

Design of a small scale fluidized-bed incinerator for MSW with ability to utilize HHO as auxiliary fuel

Waste incineration has become a mature technology and widely accepted due to its environment friendliness, easy operation and ability to reduce more than 95% mass fraction. There are some inherent limitations associated with incinerators such as high fuel consumption and cite feasibility. In this study, we propose a novel design concept of small scale fluidized bed incinerator for household use, with the ability to consume brown’s gas (HHO) as primary fuel for incinerate waste. In principle, the HHO gas generated through photovoltaic (PV) integrated water electrolysis system would be feed from the bottom to provide heat energy to the waste. Theoretical design of fluidized bed type incinerator has been presented with water electrolyzer system. It was calculated that 150 lph of hydrogen is required for this proposed incinerator system which can handle 5 kg of waste.

Performance impairment of Waste to Energy plants during waste delivery times – An analysis of relevant operating parameter

Despite long-term practical experience with waste incineration plants, their operation under the conditions for which they were designed pose challenges, mainly due to the heterogeneous composition of the waste feed.Within the framework of the present paper, the operation of 6 waste incineration plants (five grate and one fluidized bed incinerator) have been analysed in terms of hourly steam production, waste throughput, auxiliary fuel consumption and air surplus over one year. The results reveal that the operation of the majority of the plants was negatively influenced during times of waste delivery. Reductions in steam production and waste throughput of up to 3% were observed for these times in comparison to periods without any delivery of waste. Furthermore, an increase in air surplus and auxiliary fuels consumption (up to a factor of 2) was noticed, both resulting in lower environmental performance. The results further indicate that incineration plants receiving their waste via trucks are more prone to impairments of performance than plants supplied via train delivery. This observation might be explained by the fact that train delivery requires a transfer of the waste from truck to train, which is typically associated with a mixing of the waste.Based on the observed impairment of the operation during waste delivery times, the related economic loss for plant operators is estimated to be several 100,000 Euros per year. Hence, in order to improve the performance of waste incineration plants, a better mixing of the waste, in particular during times of waste delivery, is recommended.

A Study on Treatment and Recycling of Waste Fluid Sand from the Fluidized Bed Incinerator

A Study on Treatment and Recycling of Waste Fluid Sand from the Fluidized Bed Incinerator

Speciation of Cu and Zn in bottom ash from solid waste incineration studied by XAS, XRD, and geochemical modelling

Millions of tons of bottom ash (BA) is generated from incineration of industrial and municipal solid waste each year within EU. The magnitude of leaching of metals like Cu and Zn is critical for hazard and risk assessment of these ashes. Although speciation of metals is a key factor to understand and predict metal leaching, speciation of Cu and Zn in BA is not well known. In this study six metal separated and carbonized BA were investigated by a combination of X-ray absorption spectroscopy, X-ray diffraction, leaching/extraction tests, and geochemical modelling. Five of the BA were from grate boilers and one from a fluidized bed incinerator. The aims were to identify similarities in Cu and Zn speciation and to identify main species. The combination of several techniques was necessary to draw conclusions about speciation and displayed coherent results. A similar speciation of Cu and Zn was indicated in the five studied grate boiler ashes although the proportions between species may vary. Copper(II) oxide and Cu metal were the main Cu species in all BA. Zinc(II) oxide and willemite (Zn2SiO4) were identified in grate boiler ashes. The fluidized bed ash contained Zn-Si-minerals and possibly franklinite or gahnite, while the Zn(II) oxide content was low, if any. The results have implications for classification and risk assessment of MIBA.

Characteristics of fly ash from waste-to-energy plants adopting grate-type or circulating fluidized bed incinerators: a comparative study

ABSTRACT Although the pressure of waste siege was reduced by the development of waste-to-energy (WTE) plants, every year million tons of toxic municipal solid waste incineration (MSWI) fly ash is produced which is regarded as a hazardous waste. In this paper, ten MSWI fly ash samples were collected to analyze the composition, physical properties, leachability of heavy metals, and toxicity of dioxins to obtain a comprehensive evaluation, which has not been discussed in the previous studies. The analysis and comparison of fly ash is based on the main type of incinerators applied nowadays. Due to differences in the incinerator types, there were significant differences observed in the size distribution, microstructure, element content, and crystalline structure of fly ash, which are related to the heavy metal leachability and dioxin toxicity. The heavy metal leaching toxicity of nine fly ash samples failed to meet the requirements of the landfill regulations. The main heavy metals above an unacceptable level are Pb (4.271 mg/L) in the grate-type fly ash and Cd (1.035 mg/L) in the circulating fluidized bed (CFB) fly ash. Furthermore, the I-TEQ concentrations of dioxins of two CFB fly ash (3.207 and 3.212 ng I-TEQ/g) exceeded the limit value. The main contribution to the dioxin concentrations of the fly ash is from OCDD (18.7–64.3%), and the main contributor to the I-TEQ (international toxicity equivalent quantity) value is 23478-PeCDF (range 33.0 to 43.2%). In addition, correlation between compositional analysis and toxicity indexes was discussed carefully. The findings in this work can provide directions for the disposal and utilization of the fly ash from different incinerators, which can be beneficial for MSWI fly ash management.

Is incineration the terminator of plastics and microplastics?

It is widely accepted that incineration can permanently eliminate plastic waste. However, unburned material still exists in the bottom ash that is a solid residue from incinerators. In this study, microplastics exacted from bottom ash in 12 mass burn incinerators, one bottom ash disposal center and four fluidized bed incinerators were identified by micro-Fourier transform infrared spectroscopy. The results showed that bottom ash was a neglected microplastics source with an abundance of 1.9–565 n/kg, which indicated that per metric ton waste produce 360 to 102,000 microplastic particles after incineration. Nine types of plastics were identified, of which polypropylene and polystyrene were the predominant types. Microplastics sized between 50 μm and 1 mm accounted for 74 %. Granules, fragments, film, and fibers accounted for 43 %, 34 %, 18 %, and 5 % of the microplastics, respectively. The abundance of microplastics differed significantly with whether the local waste was source-separated, the local gross domestic product per capita, and the types of furnace. The global microplastics emission from incineration bottom ash was then estimated. Our observations provide empirical evidence proving that incineration is not the terminator of plastic waste, and bottom ash is a potential source of microplastics released into the environment.

Maximizing HBr/Br2 in the flue gas and prevention of secondary pollution during the oxy-combustion of brominated waste electrical and electronic equipment part 1- thermodynamic considerations

Organobromine compounds comprise between 3 and 8% by weight of WEEE and mainly converted to HBr and Br2 in the incinerator. However, these compounds, during the cooling of the flue gases, can form the PBDD/Fs in the post-combustion area of the furnace. Due to the many benefits of Oxy-combustion process, our group has developed a fluidised bed incinerator for burning the WEEE and plan to maximise HBr/Br2 in the flue gas. Experimental results presented in the recent papers show that the combustion of the WEEE particles attains quickly to thermodynamic equilibrium. Thermodynamic modelling can, therefore, predict the concentration of brominated pollutants, particularly HBr, Br2, HgBr2, and Br˙ in the flue gas. In this paper, the effect of various parameters for increasing the HBr/Br2 ratio in the flue gas has been investigated. The model shows that the addition of very small amounts of hydrogen in the post-combustion area can convert Br2 and Br˙ into HBr.

Comparison of porous and nonporous alumina bed materials for PAHs formation during plastic waste fluidized-bed incineration

In order to understand adsorption effect of porous materials on PAHs generation during waste fluidized-bed incineration, comparison of porous and nonporous alumina bed materials for PAHs formation was experimentally investigated in a plastic waste fluidized-bed incinerator. Meanwhile, the distributions and contents of gaseous PAHs, particulate associated PAHs, PAHs precursors (monocyclic aromatic hydrocarbons and light hydrocarbon) in the dense region, freeboard region and outlet of the incinerator were also measured. The results indicated that ethylene (C2H4), ethyne (C2H2), propene (C3H6), benzene (C6H6), and styrene (C8H8) were the main precursors for PAHs formation. The 3-ring and 4-ring PAHs were dominant, and the particulate associated PAHs was the main components in flue gas. Meanwhile, the gaseous PAHs and particulate associated PAHs were respectively reduced by 49.20% and 39.41% when the non-porous alumina was replaced by the porous alumina bed materials. Based on the PAHs formation routes, the suppression mechanism for PAHs formation was proposed that the porous alumina adsorbed more PAHs precursors in the dense region due to its higher adsorption capacity, simulateously reduced the evolution rate of the PAHs precursors and prolonged the residence time of PAHs precursors in the freeboard region of the incinerator.

Comparison of sewage sludge mono-incinerators: Mass balance and distribution of heavy metals in step grate and fluidized bed incinerators

We investigated the distribution of 18 elements including non-volatiles (Al, P, Ca, Fe, Mg, K, Mn, Cu, Na, Cr, and Ni), semi-volatiles (Zn, Pb, Ag, As, and Cd), and volatiles (Hg and S) and compared their behaviors in two types of full-scale sewage sludge mono-incinerators, namely, a step-grate stoker (GS) and two fluidized bed incinerators (F-types), with the same feed sludge. Most of the non-volatile elements were enriched five-fold in all incinerated sewage sludge ash (ISSA), while the volatile S and Hg were barely enriched in ash due to the combustion components generated in the gas phase. While the semi-volatile elements were also enriched five-fold in the F-types, a different enrichment behavior was observed in the GS. Boiler and multi-cyclone dust in the GS showed higher enrichments of Pb and Cd compared to ash due to the combined effects of lower temperature and smaller particle size. Compared to the F-types, the GS generated ashes with lower toxicity as the major component (99.7%) and hazardous dust as the minor component. In the future, more attention should be paid to grate stokers in terms of recycling ISSA.

Emissions of gaseous pollutants, polychlorinated dibenzo-p-dioxins, and polychlorinated dibenzo-furans from medical waste combustion in a batch fluidized-bed incinerator

The quantities of pollutants emitted during the incineration of medical waste using a batch fluidized-bed system have not yet been well characterized. In this study, the CO, NO, and SO2 in the gaseous emissions of a pilot scale vortexing fluidized-bed incinerator (VFBI) and the toxic polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-furans (PCDD/Fs) in the fly ash collected from the baghouse were examined. Four kinds of simulated medical wastes with different chlorine contents were used. The effects of the feeding interval, chlorine content, and the addition of calcium carbonate were experimentally evaluated. The results showed that increasing the feeding interval decreased the amount of all pollutants due to the decreased bed temperature and prolonged residence time in the incinerator. The addition of calcium carbonate decreased the emissions of the three gaseous pollutants; however, the concentrations of PCDD/Fs of the fly ash increased while calcium carbonate was added. The concentration of NO and SO2 decreased while CO concentration increased with the increasing of chlorine content in the simulated medical waste. The magnitude of the effects of the operating parameters on the PCDD/F congeners formed followed the order: chlorine content > feeding interval > Ca/Cl ratio. Based on the experimental results, we extrapolate that the threshold value of the chlorine content was about 1% for PCDD/Fs generation. At a lower chlorine content, the PCDDs formation rate is higher than that at a higher chlorine content, especially for 1,2,3,4,6,7,8-HpCDD and OCDD. When the chlorine content exceeds the threshold value of 1%, the formation rate of PCDFs exceeds that of PCDDs.

Stabilization of heavy metals in municipal solid waste circulating fluidized bed incineration fly ash by fusion–hydrothermal method

Municipal solid waste circulating fluidized bed incineration (MSWCFBI) fly ash was a hazardous waste, maintaining challenges for disposal. One effective approach was stabilizing the toxic heavy metal ions in the fly ash structures in situ. This work proposed a fusion–hydrothermal method, including fusion pretreatment in nitrogen atmosphere and microwave-assisted hydrothermal process, to treat three MSWCFBI fly ash samples. Specifically, leaching tests were performed to demonstrate the heavy metal stabilization. Through the treatment of the fusion–hydrothermal process, the concentrations of Cd, Cu, Zn, Pb, Ni, and Cr ions leaching from the fly ashes were obviously less than those of the raw fly ash and the sample only treated by hydrothermal process. Meanwhile, the heavy metal ions migrating from the fly ash to the hydrothermal residual liquid were reduced. Importantly, lots of zeolites formed during the fusion–hydrothermal process, such as to bermorite and sodalite. The fusion pretreatment significantly facilitated the conversion of quartz into amorphous silicon and silicate salts. Then, the silicon dissolution was accelerated and zeolite formation was promoted. Eventually, the heavy metal ions could be trapped in zeolite frameworks, enhancing the stabilization of heavy metal. Moreover, the cation-exchange capability values of the three treated fly ash were 1.099, 1.168, and 1.188 meq g−1, two-folder larger than those of the samples only treated by hydrothermal process. In summary, the fusion–hydrothermal method could facilitate the stabilization of heavy metal ions in the fly ash and the as-obtained solid product with high content of zeolite was promising for future applications.

Handling uncertainties inherited in life cycle inventory and life cycle impact assessment method for improved life cycle assessment of wastewater sludge treatment

Life cycle assessment (LCA) has been used to evaluate environmental impacts of products or processes including wastewater treatment. Uncertainty has not received adequate attention in LCA studies. Uncertainty inherited in LCA steps such as the life cycle inventory (LCI) or the life cycle impact assessment (LCIA) method use is unavoidable, but it affects LCA outcomes and associated decision-making. The objective of this paper was to show the impact of uncertainty from LCI and LCIA method on LCA outcomes by using a case study base approach on wastewater sludge treatment processes. A qualitative analysis included setting criteria about what data to be included in LCI, characterization of data, differentiating between major and minor contributors in LCI modeling, evaluation of data quality indicators, setting achievable alternative scenarios, and selecting proper LCIA method were used, in addition to quantitative analysis included assigning most appropriate values for data gaps and proper distribution, and conducting probabilistic analysis to evaluate overall uncertainty. This research used a full-scale wastewater treatment plant in Missouri, USA for case study in which multiple hearth incineration (MHI) is the existing process, while fluid bed incineration (FBI) and anaerobic digestion (AD) were proposed as the alternatives. Using ReCipe method, the study revealed that variation in LCA results of MHI is 63.4% for a single end-point score of 57.9 mPt. On the two alternative processes, it is 54.6% probable that FBI would have more environmental impact than AD. The case study showed that the proposed steps were able to address issues of data uncertainty. Due to differences in characterization, normalization, and weighting factors, different LCIA methods may point out different conclusions and need to be addressed in evaluation.

Dichlorination in a circulating fluidized-bed incinerator for municipal solid waste incineration system

Cl is one of the main pollutants emitted from domestic waste incineration systems. In this study, we focused on the process of Ca dechlorination in the furnace of a circulating fluidized-bed waste incineration system. We analyzed the stability of CaCl2 and Ca in the furnace, the dechlorination process, and distribution of Cl in the incineration system. The results show that the optimal Ca/Cl molar ratio for Ca dechlorination in the circulating fluidized-bed waste incinerator is 2:1; moreover, the dechlorination product CaCl2 was found to decompose at high temperatures (> 850 °C). At temperatures > 700 °C, we measured CaCl2 decomposition rates up to 80%. Ca was added in the furnace, mainly to provide a dechlorination Ca source for the decomposition of limestone into tail flue gas. The amount of Ca2+ in the flue decreased gradually, parallelly to the temperature of the flue gas. Stable CaCl2 was formed after HCl was captured, and relatively small solid particles appeared in the ash collecting bag.

The suppression mechanism of PAHs formation by coarser-sized bed material during medical waste fluidized bed incineration

In order to grasp the suppression mechanisms of polycyclic aromatic hydrocarbons (PAHs) formation by coarser-sized bed material in the process of solid waste incineration. Medical waste incineration with silica bed materials under three particle sizes (160–180 μm, 180–250 μm and 250–320 μm) was carried out in a fluidized bed combustor (FBC). The distributions and contents of PAHs, monocyclic aromatic hydrocarbons (MAHs) and light hydrocarbons along the vertical direction (0.4, 0.7 and 1.0 m) were also measured. The results showed that the PAHs concentrations in flue gas had a positive correlation with the concentrations of MAHs and light hydrocarbon during medical waste incineration. The suppression of PAHs formation by the coarser-sized silica (250–320 μm) bed material was mainly attributed to the lower heat transfer rate between the bed material and medical wastes, which resulted in slower evolution rates of MAHs and light hydrocarbon, thus inhibiting the formation of MAHs, light hydrocarbon and PAHs.

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.

Fluidized bed incinerator for medical waste that generates no residual dioxin: a mini-review

ABSTRACT The advantages of medical waste incineration include the sterilization of bacteria, stabilization of chemical activity, and reduction in waste volume. During the incineration of medical waste, dioxin is generated owing to the high chlorine content. Based on previous research, a conventional fluidized bed combustor with a minimum retrofit to dispose of medical waste without residual dioxins is presented in this study. Coal or pyrite was added to inhibit dioxin formation in the combustion chamber. Fly ash and activated carbon which had adsorbed dioxin were pelletized with adhesive material, and the pelletized fly ash was then recycled to the incinerator for burning. The pelletized fly ash with adhesive material was finally discharged as bottom ash. Bottom ash constitutes the net output of the entire incineration system. and its dioxin content can be neglected. An incineration system that does not produce dioxin residue was achieved; however, a better formula for the pelletized fly ash is still required. Title page (short abstract) The emission of dioxin from medical waste incinerators can’t be eliminated by disabling PVC as a raw material of medical devices. Based on the knowledge shown in the previous literature, an integrated fluidized bed incineration system without dioxin residual installed in a large hospital is proposed in this study. There are many ways to reduce dioxin formation during the incineration process; however, conventional methods can’t eliminate the existence of dioxin in fly ash. Pelletized fly ash recycled to the incinerator for re-burning and discharged in the form of bottom ash which is considered dioxin free.

Characterization of PCDD/Fs and dl-PCBs emission from combustion of PCB-containing oil in a fluidized-bed incinerator

Emissions of PCDD/Fs and dl-PCBs from the combustion of PCB-containing oil in a hazardous waste incinerator are characterized. Flue gas samples are simultaneously taken at three points, including the outlet of ultrasonic wet scrubber, the outlet of heat exchanger and stack. In addition, solid matter samples including incinerator bottom ash, wet scrubber sludge, heat exchanger ash and baghouse ash are also collected. The results indicate that TEQ concentration (PCDD/Fs + dl-PCBs) measured in stack from the combustion of PCB-containing oil is 0.51 ng WHO-TEQ/Nm3. For the solid matter, PCDD/F and dl-PCB concentrations of baghouse ash and wet scrubber sludge are significantly higher than those measured in bottom and heat exchanger ashes. The total removal efficiencies of PCDD/Fs + dl-PCBs achieved with bag filtration (BF) + activated carbon injection (ACI) reaches 65.0%. The emission factors of PCDD/Fs and dl-PCBs from incinerating PCB-containing oil are 1.05 and 0.08 ng WHO-TEQ/L, respectively. The overall PCDD/Fs and dl-PCBs destruction efficiencies achieved with fluidized-bed incinerator reach 99.87% and 99.9998%, respectively, which demonstrates that incineration is an effective engineering practice for treating PCB-containing oil. Moreover, this is the first study suggesting the ratios of PCB-114/(PCB-126+ PCB-114) and PCB-157/(PCB-169+ PCB-157) as indicators to distinguish the emission source of dl-PCB from combustion process and technical mixture evaporation in diagnostic ratio analysis.

Study on the migration characteristics of nitrogen and sulfur during co-combustion of oil sludge char and microalgae residue

Integrated thermal treatment (coupled pyrolysis and combustion) has great potential to be a clean and effective method for massive oil sludge (OS) utilization. Produced OS pyrolysis char (OS char) can be effectively utilized through fluidized bed incinerator with auxiliary fuels. A study on co-combustion of OS char and microalgae extraction residue (MR) were conducted with a coupled thermogravimetric-mass spectroscopy system (TG-MS), and a fluidized bed reactor system. Co-combustion process of OS char and MR could be divided into three stages, including water evaporation, volatiles release and combustion, fixed carbon combustion and minerals decomposition. SO2 emissions decreased with the increase of MR ratio and NOx emissions initially decreased followed by an increase until the MR ratio exceeded 50%. Both NOx and SO2 emissions initially increased before a decrease with combustion temperature raised. Higher excessive air ratio (α) promoted the pollutants emission. Pyrrole (N-5) content increased with the increase of MR ratio and more N-5 and pyridine (N-6) could be converted to oxidized nitrogen (N-X) in the bottom ash under a higher temperature during OS combustion. Besides, the temperature range (900–1000 °C) was conductive to SO2 release, and S4+ formation.

Influence of the type of furnace on behavior of radioactive cesium in municipal solid waste thermal treatment

Municipal solid waste (MSW) contaminated by radioactive cesium (r-Cs) has been incinerated since the Fukushima Daiichi Nuclear Power Plant accident. Eight thermal treatment plants with four different types of furnaces were comprehensively investigated to provide fundamental data to improve our understanding of the behavior of r-Cs in various types of MSW thermal treatment facilities. R-Cs tended to distribute to the fly ash (FA) more than to the residue from the bottom of the furnace (bottom ash, incombustibles or slag). The r-Cs concentrations in the FA depended on the type of furnace and followed the order; fluidized-bed incinerator < stoker type incinerator < gasification melting furnaces. Shaft-type gasification melting furnace separated r-Cs selectively into FA and simultaneously discharged decontaminated slag. The leaching rate of r-Cs from FA was high, 30–100%, and independent of the type of furnace, whereas r-Cs in the residue from the bottom of the furnace scarcely dissolved in water. Heat recovery ash e.g. gas cooler ash was characterized by intermediate r-Cs concentrations and leachabilities compared with bottom residue and FA in stoker type and fluidized-bed incinerator. In the case of shaft-type gasification melting furnace, however, heat recovery ash showed similar property to FA due to a cyclone followed by heat recovery process. We evaluated whether baghouses (air- pollution control equipment) successfully removed r-Cs from flue gas. In all cases, r-Cs in flue gas was below the limit of detection after baghouse. We concluded that different types of furnaces affected r-Cs distributions, but flue gases from baghouse systems of all types of furnaces were safe.

Comparison of waste-to-energy technologies of gasification and incineration using life cycle assessment: Case studies in Finland, France and China

Waste-to-Energy (WtE) has gradually constituted one of the most important options to achieve energy recovery from municipal solid waste (MSW). However, the environmental sustainability of a specific WtE system varies with used technologies and geographic differences. As a result, three representative WtE systems are compared using life cycle assessment (LCA): a gasification-based WtE plant in Finland, mechanical-grate incineration in France, and circulating fluidized bed incineration in China. Results show that the overall environmental performance of the gasification system is better than incineration. The use of gasification technology, attributed to an intermediate syngas purification step, can provide benefits of both reducing the stack emissions and increasing the energy efficiency. Regional waste management, especially related to MSW caloric value and emission regulation, are determining factors for a preferable performance of the incineration in France over that in China. Sensitivity and uncertainty analyses further address key variations such as choice of MSW composition, basis of displaced electricity, energy recovery mode, and application of “best-available technology” dedicated to incineration. It is found that the most sensitive parameters influencing the LCA results are: electricity recovery, CO2 emission, and NOx emission. In the future, use of the source-separated high caloric waste combined with a more stringent emission standard can efficiently improve MSW incineration in China. Bottom ash recycling for metals and materials is highly applicable regarding incineration in France. This presented study can overall contribute to the development of specific WtE technology and local waste management plan for decision-makers.