Fluidized Bed Furnace Research Articles

Comparative Study on the Applicability of Solid Waste Treatment by Fixed Grate and Fluidized Bed Incinerators: A Bibliometric Review

Using thermal treatment in the waste management process has advantages such as reducing volume and the possibility of energy recovery. There are several incineration technologies with different characteristics and potential. Incineration, however, requires efficient environmental control to reduce associated risks, such as the emission of harmful compounds. The paper aims to compare solid waste treatment processes in grate and fluidized bed incinerators based on technical and environmental characteristics. For this purpose, a bibliometric review was conducted, and consulting works available in the scientific literature describe the waste treatment process with these two technologies. The searches were carried out in the Web of Science and Web of Knowledge databases using the following search engines: “fixed grade incinerator,” “grate incinerator” and “fluidized bed incinerator”. Grate incinerators present a range of elective waste for treatment compared to fluidized bed incinerators, as they do not require homogeneous waste. The study compared solid waste incineration in fixed grate and fluidized bed furnaces. While promising for sludge treatment, the fluidized bed technology may require pre-treatment, increasing costs and limiting its use to larger facilities. Fixed grate furnaces can handle a wider variety of waste without this additional step but generate more halogenated compounds when plastic waste is present. These technologies were primarily studied in Asia and Europe, where landfill space is limited and more significant potential for energy recovery exists. Adopting these technologies in other regions depends on waste characteristics, economic conditions, and environmental impacts.

Carbon removal flotation performance and economic analysis of different coal fly ash using waste fried oil as a collector

Collector consumption in flotation is significant, and petrochemicals like kerosene, being non-renewable and expensive, are commonly used collectors; therefore, finding suitable alternatives to reduce costs is essential. Waste fried oil (WFO) possesses properties similar to those of kerosene, making it a viable substitute for flotation processes. In this study, the flotation performance was analyzed and economic analysis of WFO as a collector was performed for circulating fluidized bed furnace fly ash (CFBFA) and pulverized coal furnace fly ash (PCFFA). The interaction mechanism between WFO and fly ash was analyzed using contact angle, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) tests. The findings revealed that the optimal WFO dosage for coal fly ash closely correlates with the combustion technology used to obtain it. The study also established well-fitted curves for the loss on ignition (LOI) of CFBFA and PCFFA with changes in WFO dosage. FTIR and XPS analyses revealed that the interaction of WFO carbon chains with nonpolar regions on the surface of unburned carbon in coal fly ash resulted in an increase in hydrophobic carbon chain groups on the surface of unburned carbon, and the combination of oxygen-containing groups in WFO with the hydrophilic sites on the surface of unburned carbon were the main reasons for the enhancement of hydrophobicity of unburned carbon particles. Moreover, the economic analysis revealed that flotation of 1 t of CFBFA and PCFFA with WFO can yield profits of 1.91 USD and 1.11 USD more, respectively, compared with kerosene, which has practical applications in industry.

Migration of trace elements and radioisotopes to various fractions of solid wastes generated as a result of the sewage sludge incineration process

The research was aimed at providing new knowledge in the field of chemical characteristics of solid waste generated in the process of combustion of sewage sludge in fluidized bed furnaces. The research material consisted of disposed fluidized beds (DFB), sewage sludge ash (SSA) and air pollution control residues (APC) from three Polish installations for the thermal treatment of sewage sludge. Natural radionuclides as well as anthropogenic isotope 137Cs were determined in the tested materials and the migration of a wide spectrum of trace elements to various waste fractions generated in the process of sewage sludge combustion was examined. It was observed that both radioisotopes and most of the trace elements determined accumulate in SSA and DFB, while the APC fraction contains a much smaller amount of them. The exceptions are mercury and selenium, whose volatile compounds migrate to the exhaust gas dedusting system and accumulate in the APC fraction (up to 40 mg/kg and 13 mg/kg, respectively). A potential threat from the 226Ra isotope in SSA is identified in the context of the management of this waste in the production of building materials because the typical activity of 226Ra in SSA collected from areas with very low Ra content in natural environment exceeds 1.5–6 times the activity of this isotope in conventional cement mixtures. When managing SSA and DFB, special attention should be paid to the content of metalloids such as As, B and Se, due to the high content of mobile forms of these elements in the mentioned materials.

Comparative Analysis of Laboratory-Made and Industrial-Made Sewage Sludge Ash: Implications for Effective Management Strategy Development.

In the pursuit of environmentally and economically sustainable sewage sludge ash (SSA) management methods, researchers often employ laboratory-made SSA (L-SSA) as a substitute for industrial-made SSA (I-SSA) produced in fluidized bed furnaces. To check whether L-SSA is a material that imitates I-SSA well, the fractionation of metals whose presence is a significant problem during SSA management was performed. In addition, the grain distribution, specific surface area, and textural properties of the tested materials were examined. Differences in total Pb and Hg content and mobility of Cu, Ni, Mn, and Zn were observed between I-SSA and L-SSA. Larger particle sizes of L-SSA compared to I-SSA were confirmed, while comparable textural properties and specific surface area of both types of materials were maintained. Based on the results, it was concluded that L-SSA is chemically different compared to I-SSA, and that L-SSA should not be used as a reference in research focused on the design of SSA management methods. Moreover, fractionation of metals was performed in disposed fluidized beds (FBs), which are diverted to non-hazardous waste landfills without prior analysis. It has been proven that studied metals are present in FBs as abundantly as in SSA, while Cu, Mn, and Ni may show higher mobility than in I-SSA.

Mechanism and technological results of sulfidation roasting of oxidized lead compounds

The paper presents the results of a critical analysis of existing technologies for processing lead-zinc ores and industrial products; the relevance of the research lies in the development of methods aimed at additional extraction of zinc and lead in conditions of a rapid decrease in the content of lead and zinc in ores. The paper presents research on the thermodynamic justification of sulfiding roasting, the results of the development of technology for intensifying the process of processing poor, difficult-to-process complex lead-zinc ores and middlings through preliminary thermal activation by sulfiding roasting in a fluidized bed furnace. The mechanism of sulfidation of oxylated lead compounds has been established according to the scheme: PbO → PbO·PbSO4 → PbSO4 → PbS. The results of the physicochemical study of roasting products, as well as the results of magnetic enrichment of cinders, are presented. The results of magnetic separation of cinders after heat treatment of industrial products show that it is possible to separate up to 70% of iron in the form of pyrrhotite into a magnetic product, while the pyrrhotite content in the magnetic product is up to 98.2%. The paper presents a new technological scheme for processing lead-zinc industrial products from enrichment to obtain pyrrhotites with predicted properties.

Mechanical properties and microstructural discrepancies of concrete with flotation-modified fly ash from circulating fluidized bed and pulverized coal furnaces

Fly ash (FA) is a by-product of coal-fired power generation in thermal power plants. Disparities in coal types and combustion furnaces result in varying levels of unburned carbon in FA, hindering its effective utilization. In this study, FA from a circulating fluidized bed furnace (CFBFA) and pulverized coal furnace (PCFFA) was modified using froth flotation technology, and the influence of the modified FA from the froth flotation process on the mechanical properties and microstructural discrepancy of concrete was analyzed through the preparation of mortar and cement paste specimens. The results indicated that the flotation process proved effective in reducing the unburned carbon content in FA, with modified PCFFA showing higher surface area and fluidity, opposite to CFBFA. Notably, the flotation process altered CFBFA's mineral content, reducing CaSO4·2 H2O from 26.6% to 7.5% and increasing CaSO4, enhancing hydration and strength in concrete applications. The optimal FA dosage was found to be 20%, with CFBFA specimens displaying superior compressive strength across all tests. Conversely, the modified PCFFA exhibited low activity, making it challenging to reach the desired strength after 28-d. This study serves as a theoretical foundation for the application of highly unburned carbon FA in construction engineering and promotes the circular development of FA resources.

CHAMBER FURNACE FOR SIMULATION OF CARBON MATERIALS HEAT TREATMENT IN ELECTROTHERMAL FLUIDIZED BED

Existing laboratory furnaces for high-temperature heat treatment of materials at around 3000°C, which have graphite heaters, allow samples to be heated at a rate two orders of magnitude lower than in electrothermal fluidized bed furnaces. This makes it impossible to use them in the research into the heat treatment of carbon materials because they do not meet the conditions of shock heating and do not allow to keep accurate residence time. The paper presents the research into the use of low-density composite carbon materials as heaters. Based on the results obtained, a high-temperature chamber furnace was designed, studied, and the temperature field in the heater was simulated. As a result, a high-temperature laboratory furnace was created with a sample heating rate of 20 °C/s - 100 °C/s, which made it possible to use it to simulate the heating process in the electrothermal fluidized bed furnace. Comparison of energy consumption in the furnace with a traditional graphite heater and a low-density carbon composite heater showed that heat loss in the furnace is reduced by 1.7 to 1.8 times.

Fate of perfluoroalkyl and polyfluoroalkyl substances (PFAS) through two full-scale wastewater sludge incinerators.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are an emerging issue in wastewater treatment. High-temperature thermal processes, incineration being time-tested, offer the opportunity to destroy and change the composition of PFAS. The fate of PFAS has been documented through wastewater sludge incinerators, including a multiple hearth furnace (MHF) and a fluidized bed furnace (FBF). The dewatered wastewater sludge feedstock averaged 247- and 1280-μmol targeted PFAS per sample run in MHF and FBF feed, respectively. Stack emissions (reportable for all targeted PFAS from MHF only) averaged 5% of that value with shorter alkyl chain compounds comprising the majority of the targeted PFAS. Wet scrubber water streams accumulated nonpolar fluorinated organics from the furnace exhaust with an average of 0.740- and 0.114-mol F- per sample run, for the MHF and FBF, respectively. Simple alkane PFAS measured at the stack represented 0.5%-4.5% of the total estimated facility greenhouse gas emissions. PRACTITIONER POINTS: The MHF emitted six short chain PFAS from the stack, which were shorter alkyl chain compounds compared with sludge PFAS. The FBF did not consistently emit reportable PFAS from the stack, but contamination complicated the assessment. Five percent of the MHF sludge molar PFAS load was reported in the stack. MHF and FBF wet scrubber water streams accumulated nonpolar fluorinated organics from the furnace exhaust. Ultra-short volatile alkane PFAS measured at the stack represented 0.5%-4.5% of the estimated facility greenhouse gas emissions.

Assessing the impact of wet and dry flue gas recycling on heat transfer in oxygen-fired circulating fluidized bed furnaces

Oxygen-driven circulating fluidized bed combustion (oxy-CFB) has been suggested as a potential technique for facilitating carbon capture in large-scale power generation. Precise modeling of radiative heat transfer is vital for forecasting the thermal performance of such processes. This research examines the impact of wet and dry flue gas recycling on the thermal behavior of a large-scale oxy-CFB furnace, utilizing a combined modeling strategy that merges a three-dimensional furnace process model with a thermal radiation solver. The semi-empirical furnace model operates in steady-state conditions, accounting for fluid dynamics, reactions, and heat transfer phenomena. The radiation solver, based on the zone method, employs novel correlations for radiative heat exchange between optically thick zones. The radiation solver employs a weighted sum of the gray gases model, developed specifically for oxy-combustion, and geometric optics to determine the radiative characteristics of combustion gases and particles, respectively.This research covers various process conditions and boiler loads to evaluate the influence of wet versus dry flue gas recycling on heat transfer and temperature profiles. Model results were successfully compared against small-scale oxygen-fired CFB tests and large-scale measurements in a supercritical air-fired CFB. Utilizing an external radiation solver allows for a more precise representation of radiative heat transfer and the influence of varying process conditions. The insights from this research can aid in the design of large-scale oxy-CFB facilities, and the demonstrated modeling approach can be employed for additional model development, such as integrating the external radiation solver with other modeling tools.

CFD Simulation of Biomass Combustion in an Industrial Circulating Fluidized Bed Furnace

ABSTRACT In this study, a three-dimensional computational fluid dynamics (CFD) model is employed to investigate the hydrodynamic and combustion characteristics of biomass particles in an industrial-scale circulating fluidized bed (CFB) furnace. The CFD model considered here is based on the Eulerian-Lagrangian framework, the multi-phase particle-in-cell (MP-PIC) collision model, the coarse grain method (CGM), and a recently developed distribution kernel method (DKM). The challenge of simulating industrial-scale CFB furnaces using CFD lies in the large number of particles in the system. MP-PIC and CGM showed that local particle overloading could occur, causing the numerical simulation to diverge. The combination of MP-PIC with CGM and DKM was shown to overcome this problem. The CFD predictions werecompared with onsite temperature experiments in the furnace, and the predicted furnace temperature agreed fairly well with the measured data. Using the CFD results, the study analyzed the transient solids mixing and fluidization characteristics, as well as the thermochemical process in biomass combustion. The simulated individual particle provided insight into the physical and chemical processes of the granular flow in the dilute/dense regions of the CFB furnace. The simulated results revealed the CO and NOx emission processes in the furnace.

Comprehensive assessment of the efficiency of the system for removal, purification and processing of gases from fluidized bed furnaces of the JSC Kola MMC`s refining shop

Comprehensive assessment of the efficiency of the system for removal, purification and processing of gases from fluidized bed furnaces of the JSC Kola MMC`s refining shop

Technology of high-temperature sulfidizing roasting of oxidized lead-zinc ore in a fluidized bed furnace

Technology of high-temperature sulfidizing roasting of oxidized lead-zinc ore in a fluidized bed furnace

Modification of Concrete Composition Doped by Sewage Sludge Fly Ash and Its Effect on Compressive Strength.

The sustainable development of construction materials is an essential aspect of current worldwide trends. Reusing post-production waste in the building industry has numerous positive effects on the environment. Since concrete is one of the materials that people manufacture and use the most, it will continue to be an integral element of the surrounding reality. In this study, the relationship between the individual components and parameters of concrete and its compressive strength properties was assessed. In the experimental works, concrete mixes with different contents of sand, gravel, Portland cement CEM II/B-S 42.5 N, water, superplasticizer, air-entraining admixture, and fly ash from the thermal conversion of municipal sewage sludge (SSFA) were designed. According to legal requirements in the European Union, SSFA waste from the sewage sludge incineration process in a fluidized bed furnace should not be stored in landfills but processed in various ways. Unfortunately, its generated amounts are too large, so new management technologies should be sought. During the experimental work, the compressive strength of concrete samples of various classes, namely, C8/10, C12/15, C16/20, C20/25, C25/30, C30/37, and C35/45, were measured. The higher-class concrete samples that were used, the greater the compressive strength obtained, ranging from 13.7 to 55.2 MPa. A correlation analysis was carried out between the mechanical strength of waste-modified concretes and the composition of concrete mixes (the amount of sand and gravel, cement, and FA), as well as the water-to-cement ratio and the sand point. No negative effect of the addition of SSFA on the strength of concrete samples was demonstrated, which translates into economic and environmental benefits.

Prospects for the development of hydrogen technologies in the domestic metallurgy

The inevitability of the development of carbon-free steel production technologies in the domestic metallurgy is due not only under the pressure of environmental requirements for decarbonization, but also by the need to bring steelmaking technologies in line with the level of modern science. The electronic theory of oxidation/reduction can serve as a scientific basis for new technologies for the reduction of metals. From the standpoint of this theory, the final stage of the electrochemical process of reducing metals with any reducing agent, including hydrogen, is the electrolysis of oxides with the release of metal and gaseous oxygen under the action of an electron flow generated in the fuel cell during the combustion of the reducing agent due to the oxygen of the oxides. Comparison of two technology options ‒ iron reduction by “green” hydrogen or direct electrolysis of ore oxides using electricity from the electrical network shows a multiple advantage of electrolysis in terms of energy costs. It is concluded that the priority in the development strategy of the industry should not be given to the production and use of “green” hydrogen, but to the electrolysis of ore. The use of hydrogen as a reducing agent can be justified in the selective extraction of iron from complex ores in units such as plasma shaft furnaces, plasma reactors or fluidized bed furnace, in which, along with reduction, nitriding would also take place to convert soft iron into steel. In Russia, there is already an opportunity to master the production of steel using “green” or “turquoise” hydrogen. It is most rational to start the introduction of hydrogen reduction of iron on the basis of the deposits of titanomagnetites of the Kola Peninsula using the excess capacity of the Kola NPP to produce hydrogen

Co-Combustion Characteristics of Municipal Sewage Sludge and Coal in a Lab-Scale Fluidized Bed Furnace

The co-combustion of dry coal and sludge was carried out in a self-built laboratory scale fluidized bed furnace. We used FTIR spectroscopy, high-resolution gas chromatography, high-resolution mass spectrometry, and XRF to capture and dynamically observe the flue gas fly ash and bottom ash. The sludge sample was taken from a municipal sewage treatment plant and its mixing ratio was below 20%. The temperature distribution of the furnace was observed and the emissions of the main gaseous pollutants such as SO2, NOx, and dioxins were measured in the combustion process. The heavy metal contents of fly ash and bottom ash were later detected to analyze the migration characteristics. The results showed that all of the gaseous pollutants measured increased linearly with the sludge mixing ratio. However, it could also meet the 1 metal content of bottom ash and fly ash did not change much. Through the elaboration of the above points, this study can provide guidance for future research on the co-combustion of coal boiler sludge and suggest favorable conditions for the co-combustion of coal boiler sludge.

Method for oxidative roasting of sulfide zinc concentrates in an air oxygen stream in fluidized bed furnaces

An increase in the oxygen content in the blast to a concentration of 26-28% during the firing of zinc concentrates in the KS furnaces leads to a decrease in the formation of undesirable compounds of ferrites and zinc silicates, increases the degree of desulfurization, and shortens the firing time. At the same time, it becomes possible to load concentrate with high humidity into the furnace, which will save costs for drying the raw materials. Ultimately, it leads to an increase in the complexity of raw materials, increasing the profitability of production and making the products competitive in the world market. The article is considered questions of increased efficiency of processing collective zinc concentrates without their preliminary selective division. Our developments on the processing of collective zinc concentrates are directed to that in the maximum degree to receive sulfates of zinc transferring zinc to the solution. Thermodynamic calculations show that the formation of sulfates most intensively precedes in the range of 1000-1100 °C. It is offered to carry out roasting of a collective concentrate to furnaces of the boiling layer in the gas environment.

Mathematical modeling of zinc concentrate roasting in a fluidized bed

The paper aims to stabilize the roasting of zinc sulfide concentrates in fluidized-bed furnaces using oxygen- enriched air. The balance between the given excess air blast (on average 20%) and the amount of loaded charge is achieved by selecting an appropriate number of evaporative cooling elements in the fluidized-bed furnace. Through the evaluation of scientific and technical information, as well as literature sources on the research topic, data were collected on the effects produced by an oxygen excess in the blast on the quality of sulfide concentrate roasting and by a blast volume on the state of the fluidized bed. In addition, statistical data for the study were obtained by analyzing the operation of fluidized-bed furnaces at Electrozinc. As part of the study, the heat balance in roasting was determined, taking into account the following technical characteristics of fluidized-bed furnaces used for roasting zinc sulfide concentrates: fluidized- bed level, number of nozzles, furnace diameter, diameter in the bed zone, hearth thickness, and the total weight of the furnace. Relying on the operation analysis of fluidized-bed furnaces, a method was proposed to regulate the oxygen supply depending on the amount of loaded charge. The oxygen supply is regulated in order to ensure a stable excess of oxygen in the blast without causing any significant changes in the blast volume and, consequently, to maximize the sulfur removal from the charge. A decrease in the excess air blast below 15% was found to significantly degrade the quality of the resulting cinder and dust, while an increase of over 20% reduced the SO2 content in the exhaust gases with no noticeable improvement in the quality of cinder. Therefore, the proposed method for regulating the oxygen supply to the furnace can improve the techno-economic performance of zinc sulfide concentrate roasting in fluidized-bed furnaces.

SOFTWARE SIMULATOR FOR FLUIDIZED BED FURNACE CONTROL SYSTEM

Modeling plays an important role in the automation of technological processes and production, allowing you to create virtual pilot installations of objects based on mathematical models, analyze the operation of the object and optimize process parameters. In this work, the fluidized bed furnace is the control object. The main control strategies are presented and a description of the main blocks of the software simulator is given

Investigation of the fuel-air flow inside a vortex furnace with a fluidized bed using a special air-distributing nozzle.

The search for resources alternative to fossil sources of thermal energy is a constant component of the development of the energy sector of any country. This issue is now most urgent due to various political processes and the constant decrease of the total amount of non-renewable natural resources. One of the ways to implement the issue of replacing natural gas, coal and other types of fossil fuels is the burning of waste from agriculture and the woodworking industry. But this is associated with a significant number of technical difficulties and an insufficient theoretical basis for implementation. The article presents the results of an experimental study of the fuel-air flow inside a fluidized-bed vortex furnace using a special air-distributing nozzle. A nozzle with a 15ͦ slope of the plates is used, which does not exceed 10% of the total area of ​​the free section of the chamber of the experimental setup. In the course of the experiment, the limiting conditions for the formation of a vortex flow at different amounts of fuel and different air flow rates are indicated, and the values ​​of pressure losses and flow rates are shown. So for 2.9 kg of sawdust, the maximum speed of formation of a vortex flow is 0.72 m/s, for 5.8 kg this value is 0.57 m/s. The results obtained make it possible to formulate recommendations for the improvement of existing solid fuel furnaces through the use of special nozzles to intensify combustion processes. In the future, it is planned to consider other types of solid fuel and the influence of different angles of inclination of the blades on the air distribution nozzle on the aerodynamic characteristics inside the vortex furnace. All this will make it possible to formulate recommendations for the improvement of existing solid fuel vortex furnaces.

Solids backmixing and entrainment in the splash zone of large-scale fluidized bed boilers

This work studies the fluid dynamics of the solids in the splash zone of fluidized bed furnaces, with focus set on solids back-mixing and solids entrainment in order to enhance the understanding and prediction of the solids flow in the bottom region of the furnace. Experimental results show the establishment of a splash zone also for runs in absence of a dense bottom bed. A simple model assuming ballistic trajectories of the ejected solids is shown to satisfactorily estimate the solids back-mixing rate. The flux of non-backmixed solids, which are entrained from the bottom region, is found to be unaffected by the bottom wall configuration (tapered/vertical) for a given gas flow. Finally, an empirical expression is proposed for the solids entrainment from the bottom region which covers wide operational and unit size ranges.