Fluidized Bed Calciner Research Articles

Experimental Studies of Fluidized Bed Calcination of Granulated Clay Material.

The work presents a detailed analysis of the possibilities of the thermal processing of clay raw material granulates in a fluidized bed reactor powered by coal fuel. Potential customers of calcined granulates include the following: plants producing refractory materials for the steel industry, producers of refractory concrete, sanitaryware plants, tile plants, large-size tile plants, industry abrasives, chemicals, paints, paper, food and medical industries and others. The advantage of the presented fluid bed calcination technology is the possibility of the continuous operation of the reactor and the short time of the material in the bed, compared to the previously used methods of calcination in a shaft and rotary kiln, which lasts less than twenty minutes in the temperature range of 650-850 °C. During the experimental studies of calcination in the fluidized bed layer, the influence of the type of coal, its particle size and the mass share of coal in the feed mixture on the calcination process and the final product obtained was analysed. As a result of the conducted research, it was proven that solid fuels such as anthracite and steam coal type 31.2 (flaming) can be successfully used in the fluidized bed calcination process of clay materials. The key parameter determining the fluidized bed calcination process is the fuel particle distribution.

Research on the regulatory mechanism of pore structure in soil matrix prepared by fluidized bed calcination of coal gangue

As a bulk industrial solid waste, coal gangue has caused serious pollution to the environment, and its application in the field of soil amendments has been widely studied, but the mechanism of pore structure regulation of coal gangue as soil substrate has not been reported in the literature. In this paper, the physical and chemical properties of coal gangue are analyzed, and its particle size, element content, and occurrence state are defined. The regulation mechanism of pores and pores in preparing matrix soil with coal gangue is revealed, and an efficient and energy-saving fluidizing activation technology is proposed to prepare active matrix soil. The results show that matrix soil with optimal pore structure can be obtained by fluidized bed calcination at 700 °C for 15 min, with a porosity of 55.0 %, volumetric water content of 28.7 %, and gas phase rate of 24.8 %. The technology also removes carbon, which is prone to natural fires, and fixes sulfur, which is good for plant growth. The formation and regulation mechanism of pores structure of soil matrix prepared by fluidized calcination of coal gangue is as follows: The oxidation reaction of carbon and the decomposition of minerals in coal gangue will form pore structures. Adjusting the reaction temperature and time, controlling the rate of carbon oxidation reaction, and the rate of mineral decomposition can achieve the goal of regulating the pore structure. Large pores with a pore size greater than 0.03 mm are formed by the oxidation of carbon and the decomposition of kaolinite. The pores with a diameter of 0.0001–0.03 mm are formed by the overflow of carbon dioxide gas, which is generated by the oxidation reaction of carbon embedded in coal gangue particles and the decomposition of calcium carbonate. The results of this study will provide technical and theoretical support for promoting the comprehensive utilization of coal gangue and improving environmental protection.

Discrete Element Method Simulation of the Idaho Calcine Simulant for Hot Isostatic Pressing Canister-Filling Process: Part 1

In preliminary engineering studies and equipment commissioning, readily available simulants with certain resemblances to the target waste, such as particle size, may be employed. However, for the validation of engineering processes, it is crucial to use simulants that closely replicate the physical and flow characteristics of the waste material, typically excluding radioactivity. The production of such simulants can entail significant costs. To facilitate the development of novel engineering solutions, the U.S. Department of Energy provided a nonradioactive alumina calcine simulant. This simulant was utilized to demonstrate a hot isostatic press (HIP) canister-filling system designed by Gravitas Technologies in Australia. The simulant was synthesized through a fluidized-bed calcination process, which mirrored the chemistry and procedure employed for the actual alumina Idaho calcine waste material. Consequently, the simulant exhibited physical properties akin to the actual calcine, including particle size distribution, bulk density, and flow properties. This first paper, Part 1, presents the powder characterization test results determined by a Freeman FT-4 rheometer and the calibration methods that determined a set of unique contact model parameters for dynamically simulating Idaho calcine simulant in a discrete element method (DEM) model. The second paper, Part 2, will present the dynamic simulations of two bulk material-handling scenarios in a full-scale, three-dimensional integrated HIP canister-filling system. The predicted results are compared with historical experimental results for validating the contact model. The contact model, which represents the particle-particle and particle-boundary interactions, was calibrated according to experimental data obtained from six calibration tests. This work aims to support future research with powder characterization experimental data and a calibrated DEM contact model to assist in developing processes for the safe handling and treatment of Idaho calcine waste.

CPFD simulation of an electrically heated fluidized bed calciner with binary particles

Electrifying a calciner with clean energy can cut fuel emissions and produce a stream of relatively pure CO2 from the calcination reaction (CaCO3 → CaO + CO2), which can be utilized or stored. A fluidized bed calciner offers a high heat transfer coefficient and requires low gas flow rates for operation. The design of such a reactor is studied in this work. It is not possible to fluidize raw meal directly, so a binary mixture of coarse lime particles and fine raw meal is used. The commercial Barracuda CPFD software is applied. The model was first validated against experimental results and then used to find an optimized design. The results indicate that the suggested pilot-scale fluidized bed calciner can operate between 10 and 16 t/h of raw meal feeding with a calcination degree above 90% and with negligible coarse particle entrainment. The calciner needs 0.05–0.09 kg-CO2/kg-raw-meal for the operation, so the required gas recycling is low. Overall the calciner operation is smooth, and such a design could be used for electrification combined with CCUS.

Computational model of a Calcium-looping fluidized bed calcination reactor with imposed concentrated solar irradiance

The Calcium-looping process is a promising option for thermochemical energy storage in concentrating solar power plants. A crucial element of this process is the solar calcination reactor, where the endothermic reaction of CaCO3 calcination occurs with formation of CaO and CO2. The solar energy that is chemically stored in the reaction products can be retrieved by the exothermic reaction of CaO carbonation when needed. In this article, a new computational model is developed for the solar calcination reactor in this Calcium-looping process. The calcination reaction takes place in the riser of a continuous circulating fluidized bed that corresponds to an absorber tube exposed to concentrated solar radiation, which allows the reaction chamber to be indirectly heated. A core-annulus heat transfer model and a modified version of the Kunii–Levenspiel fluid dynamics model are used. In contrast to previous models found in the literature, the change in the mass flow rate of the species and in the density of the phases due to the reaction is considered. Simulation studies are performed with a fixed and imposed concentrated solar irradiance on the reactor wall, which varies in both the axial and angular directions. Wall conduction in the angular direction is also considered. The results show that nearly complete calcination can be achieved with a reactor of 4 m of height. A sensitivity analysis with respect to the model parameters and inlet conditions shows that the calcination conversion is mostly affected by the solids mass flow rate and the bed temperature at the inlet.

Utilization of phosphogypsum waste through a temperature swing recyclable acid process and its application for transesterification

In this paper, a biodiesel catalyst was prepared from the phosphogypsum (PG) by a hybrid approach through temperature swing acid leaching/crystallization steps followed by the subsequent fluidized bed calcination. The impacts of acid leaching and crystallization were extensively analyzed via a supervised machine learning approach using a limited number of experimental runs to find out the optimal condition. The determined optimal conditions are X1-95 (ºC), X2-30 (min), X3-30 (wt%-H2SO4), and corresponding validation experimental result (at the optimal condition setting) shows± 5% uncertainties. The prepared catalyst predominately contains CaSO4 (98 wt%) with the impurities less than 0.3 wt% (i.e., P2O5- and F-). The numbers of acid leaching cycles (up to 10 cycles) were investigated, and result indicates a good contaminates recovery (P2O5:1.8 g/100 g PG, Mg2+: 0.3 g/100 g PG, Al3+: 0.3 g/100 g PG, Fe3+: 0.1 g/100 g PG) in the leachate through the downstream solvent extraction. The catalytic conversion reaches about 50% with approximately± 5% deactivation when catalyst was reused at the same transesterification condition. The decreased binding energies of S2p (169.6 eV) and O1st (533 eV) in used catalyst indicate the deactivation of surface catalytic sites. The key properties of the prepared biodiesel are comparable to the American society for testing and materials (ASTM) standards.

Parkland Fuel's Burnaby refinery to expand renewables coprocessing

The cement industry is now confronted with the pressure of strict requirements of energy consumption and pollution emission. To solve the problem, a two-process clinker manufacturing method consisting of a pretreatment process and a final calcination process is raised. The new method uses fluidized bed reactors to substitute the rotary kiln and cyclone preheater. Applicable operation conditions of the brand-new pretreatment process are firstly investigated to make sure the method will succeed. The intermediate product is used to describe the material obtained from the pretreatment process. Influences of the variants including calcination temperature, calcination time, and calcination atmosphere on the formation of intermediate products were discussed in the study. Results showed that the amount of C2S (dicalcium silicate) and strength of the intermediate product particles increased with the rising temperature. The superiority of rapid heating and fluidization in the pretreatment process was illustrated by comparing three heating styles. The recommended sequence of calcination was fluidized bed calcination > rapid calcination > slow calcination. Calcined for 10 min at 1200 °C is the optimal condition for the pretreatment process. The influence of atmospheres on C2S formation was not obvious. Operation conditions of the pretreatment process were determined for further study.

Effect of fluidized bed calcination on cement clinker intermediate products formation under the eutectic temperature

The cement industry is now confronted with the pressure of strict requirements of energy consumption and pollution emission. To solve the problem, a two-process clinker manufacturing method consisting of a pretreatment process and a final calcination process is raised. The new method uses fluidized bed reactors to substitute the rotary kiln and cyclone preheater. Applicable operation conditions of the brand-new pretreatment process are firstly investigated to make sure the method will succeed. The intermediate product is used to describe the material obtained from the pretreatment process. Influences of the variants including calcination temperature, calcination time, and calcination atmosphere on the formation of intermediate products were discussed in the study. Results showed that the amount of C2S (dicalcium silicate) and strength of the intermediate product particles increased with the rising temperature. The superiority of rapid heating and fluidization in the pretreatment process was illustrated by comparing three heating styles. The recommended sequence of calcination was fluidized bed calcination > rapid calcination > slow calcination. Calcined for 10 min at 1200 °C is the optimal condition for the pretreatment process. The influence of atmospheres on C2S formation was not obvious. Operation conditions of the pretreatment process were determined for further study.

Ferrite production with fluidized bed calcination

AbstractFor the process intensification of ferrite production, fluidized bed calcination of raw‐mix (RM) particles for strontium ferrite was tested in a laboratory scale fluidized bed. In cases when the bed was made only of RM particles, agglomeration took place above 900 K, and above 1350 K rapid defluidization was unavoidable. However, successful calcination with no defluidization was achieved by calcining RM particles in the bed of coarse spherical alumina particles. One kilogram of calcined product was produced by repeated batch calcination at 1423 K and with retention time of 60 minutes. The products were made into magnets and their magnetic properties were evaluated. The magnetic properties of fluidized bed product were compatible with rotary kiln products, although residue of unreacted Fe2O3 seemed to have detracted the former somewhat. The presence of unreacted Fe2O3 was found to be caused by the selective adhesion of SrCO3 on the bed material. A slight adjustment of Fe/Sr ratio in the RM was found to be effective in the elimination of such residuals.

Processing of spodumene concentrates in fluidized-bed systems

The production of lithium carbonate or lithium hydroxide out of lithium bearing ores requires a thermal activation for the phase transition in the mineral to enable an acid or soda leaching in the downstream hydrometallurgical section.In this paper, traditional processing of lithium ores in the lithium industry is reviewed and opportunities to improve product quality and recovery rate by simultaneously reducing energy consumption will be presented. The conventional process for pyro-processing is still based on rotary kiln, a technology in use since the early days of lithium ore processing, albeit not significantly further developed since. A new technology in this field is fluidized-bed calcination. A study of the major process parameters (temperature and residence time) was performed on laboratory and larger bench scale aiming for optimal product quality for subsequent processing.When converting α- to both β- and γ-spodumene, high conversion rates were achieved for all investigated materials. The conversion of α- to only β-spodumene varies significantly by concentrate. Preferential conditions were temperatures in the range of 1050–1070 °C with retention times of typically 25–40 min. Additional results include the characterization of granulometric properties, in particular the effect of defragmentation by decrepitation, elemental and mineral phase composition, and further aspects specifically related to the application of fluidized bed technology.After identifying optimal process conditions for calcination and proving general feasibility at laboratory scale, the technical feasibility was confirmed for a wide range of spodumene concentrates at bench and pilot scale (20 up to 500 kg/h feed) providing the basis for industrial process design. Thus, spodumene decrepitation through applying fluidized-bed technology is technically feasible for non-sticking material and high and homogenous product quality can be achieved.

Fluidized bed reactor assisted by Oxygen Transport Membranes: Numerical simulation and experimental hydrodynamic study

In the near future, H2 is bound to become an important energy carrier used for surplus power storage and for sustainable transportation. An innovative technology for the production of a H2 rich gas is the Sorption Enhanced Reforming (SER) of hydrocarbons: a solid CaO-based sorbent is used to capture CO2 produced by reforming and water gas shift, enhancing the equilibrium. CaCO3 is decomposed in a fluidized bed oxy-combustion calciner and the sorbent recycled. In this work, the interest is focused on the Calcium Looping (CaL) cycle, more specifically on the combustor/calciner fluidized bed reactor of the pilot scale platform ZECOMIX (ENEA – 5 kmol/h of H2). The feasibility to feed O2 to a bubbling fluidized bed calciner by means of Oxygen Transport Membranes (OTM) is studied using a simulation model. The fluidizing flow rate is made of CO2 and CH4, preliminarily heated up to 700–850 °C by heat exchange with the output gas stream (above 900 °C); overall gas flow rate and methane content are enough to reach vigorous bubbling fluidization (u ≈ 10 umf) and temperature required by calcination, respectively. Cold model experimental tests with a cylindrical bubbling fluidized bed reactor with internals (vertical rods mimicking the OTM system) are carried out to support the design of the calciner unit in the ZECOMIX experimental platform. The hydrodynamic study is performed under ambient conditions to simulate fluidized bed expansion and to evaluate bubbles behavior in the calciner, in presence of vertical, tubular membranes for oxygen transfer.

Biodiesel production using calcium‐based catalyst from venus shell: Modeling of startup production in an industrial reactor

Calcium oxide‐based catalyst was produced from Venus shell by fast fluidized bed calcination for biodiesel synthesis. The kinetics of biodiesel synthesis was found to be a pseudo‐first‐order reaction at the experimental conditions. The obtained kinetic parameters were used for modeling the startup operation of biodiesel production in an industrial continuous stirred tank reactor (CSTR). The model was found to agree well with the reagent concentration and temperature profiles in a real production practice during biodiesel production. The variations of initial temperature, initial reagent concentration in the reactor was investigated. It was found that the reagent concentration and temperature oscillated around the final steady state. From safety operation perspective, the first 4 h were found to be the most unsteady period during continuous production. The initial concentration of waste fry oil (WFO) was also found to be critical to the safe operation of CSTR. A violation of the settings for safe operation of CSTR will be triggered once the initial concentration of WFO in CSTR reaches 500 mol m−3. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13053, 2019

Effect of calcination temperature on activation behaviors of coal-series kaolin by fluidized bed calcination

Effect of calcination temperature on activation behaviors of coal-series kaolin by fluidized bed calcination

An enhanced process of using direct fluidized bed calcination of shrimp shell for biodiesel catalyst preparation

Fluidized bed reactor significantly intensified the shrimp shell (SS) calcination process for the preparation of high performance CaO based catalyst. A modified Shrinking-Core Model (SCM) was employed to describe the calcination process at high temperature. The activation energy of the chemical reaction controlled initial stage of the decomposition was 64kJmol−1. The activation energy of the diffusional controlled subsequent stage of the decomposition was 22kJmol−1. The response surface methodology (RSM) and the central composite design (CCD) were used to optimize biodiesel preparation conditions. Three critical operational parameters, calcination temperature (°C), catalyst loading (%) and methanol to oil ratio (–) were chosen as independent variables in CCD. The individual effect of the calcination temperature and the combined effect of the calcination temperature with the catalyst loading were significant to biodiesel conversion. The optimal condition for achieving the maximum biodiesel conversion was obtained: calcination temperature (800°C), catalyst loading (3%), and the ratio of methanol to oil (10), with yield and conversion reaching 87.5% and 89%. The 0.16h of calcination duration was achieved using fluidized bed reactor.

Simulation of the reacting flow within a pilot scale calciner by means of a three phase TFM model

The aim of the present work is the 3-D CFD simulation of the reacting flow inside a pilot-scale calciner, which is part of the 1MWth dual fluidized bed (DFB) installation located at TU Darmstadt (TUD). The riser of the fluidized-bed calciner is a cylindrical tube with a height of 11.365m and a varying inner diameter equal to 0.28m near the bottom area and 0.3967m at the freeboard. The energy required for the endothermic reaction is provided by the coal combustion inside the same reactor. The gas-sorbent-fuel flow is simulated by means of the pure Eulerian Two-Fluid model (TFM), which is incorporated into the ANSYS Fluent commercial platform, with the implementation of numerous user-defined functions. Owing to the presence of two solid phases a modified version of the Kinetic Theory for Granular Flows (KTFG) for the bi-dispersed flow is applied. The advanced Energy Minimization Multi-Scale (EMMS) scheme with a new cluster correlation and the homogeneous Gidaspow model are applied for the calculation of the gas-sorbent and gas-fuel momentum exchange coefficients, respectively. Additionally, the Syamlal-Obrien symmetric model is used for the calculation of the sorbent-fuel momentum exchange coefficient. Proper reaction rates retrieved from the literature are applied for the simulation of the heterogeneous and homogeneous reactions occurring inside the reactor. Apart from the calcination of CaCO3 to CaO, the carbonation reaction is also incorporated into the numerical model, in order to observe if the reverse reaction is favored, when the temperature is below calcining conditions. The Computational Fluid Dynamics (CFD) model is validated against available experimental data regarding the pressure and temperature distribution along the riser and O2/CO2 concentrations at the calciner exit. Simulation results show that the carbonation reaction is indeed favored near the bottom bed, owing to the low temperature values, whilst the calcination rate is equal to zero. Over the height of the burner section, where the fuel enters the reactor, the temperature rises quickly to calcining conditions. Regarding the heat transfer mechanisms, it can be seen that in both solid phases the gas-solid heat exchange coefficient takes its maximum value near the bottom bed and then decreases, as the flow becomes more dilute. This fact reveals the strong dependence between the convective exchange coefficient and the solids volume fraction. Finally, concerning the CFD model accuracy, the different sub-models applied, such as drag-force models, reaction rates, heat transfer coefficients, should be further investigated in future simulations in order to enhance its validity.

セメント製造用流動層仮焼炉のDEM-CFD数値解析および実機検証

A numerical calculation method of the fluidized bed calciner for cement production including pulverized coal combustion, raw material decarbonation reaction and heat transfer was developed using the coupling simulation method of DEM - CFD (Discrete Element Method - Computational Fluid Dynamics). In addition, in order to shorten the calculation time, a coarse-grained model for DEM was used in the DEM-CFD. Based on this, the influence of the position and the number of pulverized coal blowing lines into the calciner on the characteristics of pulverized coal combustion and the property of raw material decarbonation was investigated. As a result, a modification plan to change pulverized coal blowing lines to promote pulverized coal combustion and raw material decarbonation was found from the calculation results, and the position and the number of pulverized coal blowing lines were changed from a single pulverized coal blowing line to two blowing lines in a commercial manufacture system. Then, the modified effectiveness and the validity of the numerical calculation method were verified by measuring actual gas composition and temperature distribution in the calciner before and after modifying.

The Indirectly Heated Carbonate Looping Process for CO2 Capture—A Concept With Heat Pipe Heat Exchanger

The carbonate looping process using the reversible calcination/carbonation reaction of limestone is a promising way to reduce CO2 emissions of fossil fired power plants. This paper describes the concept of an indirectly heated version of this process in which heat pipes accomplish the heat transfer from an air-blown fluidized bed combustor to a bubbling fluidized bed calciner. It defines the calciner's specific heat demand which is a pendant to the heating value of coal. The dimensioning depends on the processes inside heat pipes as well as heat transfer of immersed heating surfaces. Experimental investigations in an electrically heated batch reactor with a similar pipe grid provide heat transfer coefficients under calcination conditions.

CO2 capture performance of CaO–based pellets in a 0.1 MWth pilot-scale calcium looping system

Post-combustion CO2 capture performance of CaO-based pellets tested in a pilot-scale calcium looping system is investigated. The pellets were prepared from two natural limestones with 10wt.% cement as a binder. The pilot-scale system setup consists of a circulating fluidized bed calciner operating at 900°C and a bubbling bed carbonator operating at 650°C. The flue gas was supplied to the carbonator from a natural gas-fired combustor, while the oxy-fuel combustion condition was established in the calciner using wood pellets as the fuel source. The test campaign results showed that CO2 capture efficiencies in the range of 80–90% can be achieved for each sorbent. The carbonation efficiency with limestone was steady throughout the ~5h steady-state operation period, whereas efficiencies obtained with pellets exhibited a gradual decline over the duration of the test. An average carbonation conversion over the steady-state duration indicated the superiority of limestone with a conversion of 7.8%, compared to that of 6.0–6.8% achieved by pellets. Neither the limestone type nor the make-up mode showed any significant effect on the performance of the pellets. The inferior performance of pellets compared to that of limestone was attributed to the rapid and sever sintering of the pellets at the early stages of the test. It was concluded that, under the test conditions tested here, the use of CaO-based pellets in a pilot-scale calcium looping system does not seem to be a promising approach due to the significantly higher cost of production with comparable CO2 capture performance to that of limestone. Nonetheless, the test campaign provided important insights into the behavior of synthetic/modified sorbents under pilot-scale calcium looping conditions, which has not been reported elsewhere.

A Hybrid Carbon Capture System of Indirect Calcination and Amine Absorption for a Cement Plant

Here we present the process integration of the indirect calcination process existing in the literature [1] into a cement plant. The indirect calcination process is composed of a circulating fluidized bed combustor and a fluidized bed calciner where hot solid particles are circulated between those reactors for heat transfer. It allows separation of CO2 from limestone calcination in a concentrated form. The process integration proposed in this study minimizes the total thermal energy requirement by using excess energy from high temperature flue gases for cement raw meal preheating as in the conventional cement manufacturing process. It also suggests a new hybrid carbon capture system where an additional CO2 capture unit is combined with the indirect calcination process, since the standalone indirect calcination application can only provide a moderate level of CO2 avoidance. The amine process is added to increase CO2 avoidance rate further. Full process flowsheets have been developed and analyzed using the commercial software UniSim Design R400 from Honeywell. The hybrid system can achieve more than 90% carbon capture rate thanks to the supplementary amine process while the indirect calcination can capture only 56% without the amine process. With the support of a simple and transparent economic analysis, the capture cost involved in the hybrid system was estimated to be higher than that of the indirect calcination only but significantly lower than that of the standalone amine process on a basis of unit CO2 avoided. © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of GHGT.

The Italian ZECOMIX Platform: CO<sub>2</sub> Capture on Calcined Dolomite in Fluidized Bed Carbonator Unit

The Italian Zecomix platform is a gasification pilot-scale plant integrated CCS technology, whose flexibility allows operating each unit alone. For quantitative analysis of the gaseous species an analytical system based on commercially available instruments and sampling lines at various points of plant was properly designed. A Fourier Transform Infrared Spectrometric (FTIR) with portable low resolution and gas chromatographic tools were used. The fluidized bed calciner/ carbonator unit was fed with naturally occurring dolomite (about 300 kg) from quarry of Biella (Italy) and tested for CO2 capture. Carbonation reaction was conducted at around 700°C under simulated reformed synthesis gas containing 30% of CO2. Based on GC and FTIR results a CO2 retention better than 70% was achieved. The application of grain model establishing the carbonation reaction was kinetically controlled within 50 seconds and the reaction rate constant was comparable to that obtained at laboratory-scale level by thermogravimetric analyzer.