Calcination in an electrically heated bubbling fluidized bed applied in calcium looping

Switching fossil fuels to green electricity as the energy source to decarbonate the raw meal in the calciner can eliminate the CO2 emissions produced through fuel combustion and also provide a basis for simple capture of the CO2 generated through calcination, as CO2 is the only gaseous product exiting from the electrified calciner. For this reason, an electrically-heated fluidized bed reactor was designed as a calciner and its applicability and cost estimation were carried out. A mass and energy balance for steady-state conditions was conducted, so that relevant temperature, flow rates, and duties in the electrically-heated FB reactor and heat exchanger have been calculated by MATLAB code. The key parameters of FB reactor such as minimum fluidization velocity, minimum bubbling velocity, terminal settling velocity, and the reaction time based on the particle size distribution were calculated. The fluidizability of the fine limestone particles was tested by a cold-bed BFB unit and it revealed that owing to the fine particle sizes of the raw meal, there are strong cohesive forces between the particles. Hence, a conventional bubbling fluidized bed is difficult to fluidize Geldart C particles. The identical system was simulated by Barracuda® and the results of the simulations had a good consistency with the experiments. A binary-particle fluidization system, mixing fine powders with the coarse particles, was proposed to enhance the flowability of fine particles. The fluidized bed calciner process was designed as a semi-batch process operating in two modes; the calcination mode (with a low gas velocity) and the entrainment mode (with a higher velocity). After the raw meal particles have been calcined, they have to be separated from the coarse, inert particles. This can be done by increasing the velocity of the CO2 used for fluidization to a value sufficiently high to entrain the raw meal particles, but still sufficiently low that the coarse, inert particles are not entrained. The inert particles may provide a homogeneous distribution of the fine particles and help to fluidize them. The aggregation and clustering of the fine particles will decrease due to collisions with inert coarse particles. The inert particles will also provide a thermal energy reservoir through their heat capacity and thereby contribute to a very stable bed temperature, which is advantageous in the control of the process. The operational conditions at 1173 K, such as the particle size distribution of the inert particles and the fluidization gas velocity were calculated by the Barracuda simulations. The inert particles with the diameter range of 550-800 µm and the velocities in the calcination and entrainment modes equal to 0.18 m/s and 3 m/s appeared as suitable for the calciner operation. The simulations showed that at the velocity of 0.18 m/s, 7.6% of fine particles may be entrained. However, by comparing the CO2 residence time with the reaction time of particles, it was concluded that all fine powders were calcined before leaving the be

Fluidized bed calcination of cement raw meal: Laboratory experiments and CPFD simulations

The chemical and thermal processes associated with the decarbonation and fuel combustion in the cement kiln process produce a large amount of carbon dioxide (CO2) contributing with around 8 % of the global CO2 emissions. Utilizing green electricity instead of fossil fuels to decarbonate the raw meal in the calciner can eliminate the CO2 emissions produced through fuel combustion and also provide a basis for simple capture of the CO2 generated through calcination because CO2 is the only gaseous product exiting from the electrified calciner. In the current work, an electrically heated fluidized bed (FB) reactor is being developed to calcine the raw meal. The FB may replace the traditional entrainment calciner used in many plants. The purpose is to enable efficient indirect heat transfer in the bubbling bed and hence obtain pure CO2 as the gaseous product from the calciner. The minimum fluidization velocity and pressure drop of the particle bed are important characteristics in the design of a bubbling fluidized bed, and these have been measured in a cold-flow lab-scale fluidized bed unit. The particle size distribution of the meal ranged from 0.2 – 180 µm, with a median particle size of 21 µm. The experimental results revealed that the regular cement raw meal is difficult to fluidize due to the large fraction of Geldart C particles in the meal. Based on experimental observation, this may be explained by inter-particular electrostatic forces forming particle clusters. The fluidization process has also been simulated with the commercial computational particle and fluid dynamics (CPFD) software Barracuda® (version 17.4.1). The purpose of using CPFD was to be able to simulate the process at cold-flow conditions and then, based on this, simulate the process at large-scale hot-flow conditions. The simulation results complied quite well with the lab-scale experiments and confirmed the difficult fluidization of the meal

Fluidized bed calcination of cement raw meal: Laboratory experiments and CPFD simulations

The chemical and thermal processes associated with the decarbonation and fuel combustion in the cement kiln process produce a large amount of carbon dioxide (CO2) contributing with around 8 % of the global CO2 emissions. Utilizing green electricity instead of fossil fuels to decarbonate the raw meal in the calciner can eliminate the CO2 emissions produced through fuel combustion and also provide a basis for simple capture of the CO2 generated through calcination because CO2 is the only gaseous product exiting from the electrified calciner. In the current work, an electrically heated fluidized bed (FB) reactor is being developed to calcine the raw meal. The FB may replace the traditional entrainment calciner used in many plants. The purpose is to enable efficient indirect heat transfer in the bubbling bed and hence obtain pure CO2 as the gaseous product from the calciner. The minimum fluidization velocity and pressure drop of the particle bed are important characteristics in the design of a bubbling fluidized bed, and these have been measured in a cold-flow lab-scale fluidized bed unit. The particle size distribution of the meal ranged from 0.2 – 180 µm, with a median particle size of 21 µm. The experimental results revealed that the regular cement raw meal is difficult to fluidize due to the large fraction of Geldart C particles in the meal. Based on experimental observation, this may be explained by inter-particular electrostatic forces forming particle clusters. The fluidization process has also been simulated with the commercial computational particle and fluid dynamics (CPFD) software Barracuda® (version 17.4.1). The purpose of using CPFD was to be able to simulate the process at cold-flow conditions and then, based on this, simulate the process at large-scale hot-flow conditions. The simulation results complied quite well with the lab-scale experiments and confirmed the difficult fluidization of the meal

Fluidized bed calcination of cement raw meal: Laboratory experiments and CPFD simulations

The chemical and thermal processes associated with the decarbonation and fuel combustion in the cement kiln process produce a large amount of carbon dioxide (CO2) contributing with around 8 % of the global CO2 emissions. Utilizing green electricity instead of fossil fuels to decarbonate the raw meal in the calciner can eliminate the CO2 emissions produced through fuel combustion and also provide a basis for simple capture of the CO2 generated through calcination because CO2 is the only gaseous product exiting from the electrified calciner. In the current work, an electrically heated fluidized bed (FB) reactor is being developed to calcine the raw meal. The FB may replace the traditional entrainment calciner used in many plants. The purpose is to enable efficient indirect heat transfer in the bubbling bed and hence obtain pure CO2 as the gaseous product from the calciner. The minimum fluidization velocity and pressure drop of the particle bed are important characteristics in the design of a bubbling fluidized bed, and these have been measured in a cold-flow lab-scale fluidized bed unit. The particle size distribution of the meal ranged from 0.2 – 180 µm, with a median particle size of 21 µm. The experimental results revealed that the regular cement raw meal is difficult to fluidize due to the large fraction of Geldart C particles in the meal. Based on experimental observation, this may be explained by inter-particular electrostatic forces forming particle clusters. The fluidization process has also been simulated with the commercial computational particle and fluid dynamics (CPFD) software Barracuda® (version 17.4.1). The purpose of using CPFD was to be able to simulate the process at cold-flow conditions and then, based on this, simulate the process at large-scale hot-flow conditions. The simulation results complied quite well with the lab-scale experiments and confirmed the difficult fluidization of the meal.acceptedVersio

CPFD simulation of enhanced cement raw meal fluidization through mixing with coarse, inert particles

In the current work, computational particle and fluid dynamics (CPFD) simulations are used to study an electrically heated bubbling fluidized bed (BFB) used as a calciner in a cement manufacturing process, applying a binary-particle fluidization system. Owing to the fine particle size (0.2 – 180 µm) of the limestone used as a raw meal in the cement kiln process, a conventional bubbling fluidized bed may be difficult to apply due to particle cohesion causing poor fluidizability of the particles smaller than 30 µm. In the current study, to enhance the fluidization of the raw meal particles, they are mixed with coarse (550 – 800 µm), inert particles. The aggregation and clustering of the fine particles will decrease due to collisions with inert coarse particles, and hence a more homogeneous distribution of raw meal particles may be achieved. The inert particles will also provide a thermal energy reservoir through their heat capacity and thereby contribute to a very stable bed temperature, which is advantageous in the control of the process. After the raw meal particles have been calcined, they have to be separated from the coarse, inert particles. This can be done by increasing the velocity of the CO2 used for fluidization to a value sufficiently high to entrain the raw meal particles, but still sufficiently low that the coarse, inert particles are not entrained. The commercial CPFD software Barracuda was used for simulations to investigate suitable operational conditions at 1173 K, such as the particle size distribution of the inert particles and the fluidization gas velocity. The impact of gas velocity variation on the fluidization of the particle mixture was studied, and an appropriate range of velocities for the calcination and entrainment modes could be determined. The simulations revealed that mixing raw meal particles with inert coarse particles can enhance the flowability in the FB reactor indicating that it is possible to apply the concept in a full-scale calcination process

Evaluating the performance of advanced wells in heavy oil reservoirs under uncertainty in permeability parameters

Advanced wells play a crucial role in maximizing the efficiency of oil production. To achieve a successful design for advanced wells, several parameters must be considered and evaluated. Uncertainty in these parameters can have a significant impact on the performance assessment of the well in its lifetime. Absolute permeability, relative permeability, and permeability anisotropy are the parameters that determine reservoir permeability and are among the most important design parameters to be considered. This paper aims to assess the performance of advanced wells completed with passive and reactive downhole Flow Control Devices (FCDs) under uncertainty in the reservoir permeability parameters. The assessment is conducted through a case study on a synthetic heavy oil reservoir with a strong water drive. The EclipseSM reservoir simulator is used as a simulation tool and the Latin Hypercube Sampling (LHS) approach is applied as a sampling tool for uncertainty analysis in this study. According to the obtained results, under the presence of uncertainty, advanced wells with Autonomous Inflow Control Device (AICD) and Autonomous Inflow Control Valve (AICV) completions are able to mitigate the risk of water production by 53.20% and 71.12% respectively compared to conventional wells. However, Inflow Control Device (ICD) completion can only reduce the risk by 0.87%

Experimental and computational studies of circulating fluidized bed

Biomass gasification represents an efficient process for the production of power, heat and biofuels. Different technologies are used for gasification and this article focuses on a circulating fluidized bed (CFB) system. Understanding the behaviour of particles is of primary importance and a cold flow CFB experimental unit was constructed and tested. The particle circulation rate is greatly affected by the loop seal performance, and therefore the loop seal should be properly optimized to maintain an uninterrupted operation. Smooth flow regimes were obtained for the CFB by varying the loop seal aeration rates. Particles with size 850–1000 µm and 1000–1180 µm were chosen for the experiments. The minimum flow rates of air into the riser for the two particle sizes were found to be 1.3 and 1.5 Sm3/ min, respectively. To obtain a smooth flow regime, a velocity range for aeration in the loop seal was found for the two particle sizes. Based on the experimental results, combinations of flow rates were suggested for the simulations. A Computational Particle Fluid Dynamic (CPFD) model was developed using Barracuda VR, and the model was validated against experimental results. The simulated results for the system regarding the pressure and the height of the bed material in the standpipe agreed well with the experimental results. The deviation between the experimental and computational pressure was less than 0.5% at all the locations for both the particle sizes. The deviation in particle level was about 6% for the 850–1000 µm particles and 17% for the 1000–1150 µm particles. Both the experiments and the simulations predicted that a small fraction of the circulating sands are emitted from the top of the rig. The validated CPFD model was further used to predict the flow behaviour and the particle circulation rate in the CFB