High Temperature

Gas-solid fluidized beds are widely employed in chemical and metallurgical industries due to their unique and favorable characteristics in heat and mass transfer, gas-solid contact, and uniform and controllable temperature. They are capable of being employed for processing a wide range of particulate materials including low quality feedstocks like waste feedstocks. Gas-solid fluidized beds are also employed in many under-development technologies for CO2 capture and CO2 utilization for transition to green energy.

Interparticle forces (IPFs) are among the important parameters that can significantly affect the hydrodynamics of a gas-solid fluidized bed and, hence, its overall performance. They are particularly critical for ultrafine powders for which hydrodynamic behavior is principally controlled by these forces rather than hydrodynamic and/or gravitational forces. Another situation that IPFs can play an important role is at elevated operating conditions where the magnitude of these forces is generally greater than that at ambient conditions.

The main challenge in adequately accounting for the contribution of IPFs in hydrodynamic behavior of a gas-solid fluidized bed lies in the unavailability of a reliable technique for in-situ quantification of these forces. Therefore, the primary goal of this study is to develop a reliable approach to quantify the magnitude of these forces in comparison to hydrodynamic/gravitational forces. Subsequently, hydrodynamic models/correlations will be developed in order to simultaneously consider the effect of gravitational, hydrodynamic, and interparticle forces on hydrodynamic behavior of these units.

Bubble columns (BCs), which contain gas and liquid phases, and slurry bubble columns (SBCs), which contain gas, liquid, and solid phases, are among widely utilized multiphase reactors in industry. They are characterized by bubbly flows, where a dispersed gas phase is injected into a pure liquid phase or a slurry, which is a mixture of liquid and fine solids. BCs and SBCs are widely adopted in several chemical, biochemical, and petrochemical processes, particularly when the overall reaction rate is mass transfer limited. The construction of these columns is relatively simple, yet their scale-up is very challenging due to the complexity of their hydrodynamics and, hence, heat and mass transfers. Many studies have focused on the hydrodynamic aspects of BCs and SBCs while most of them have been conducted at laboratory or pilot scale. Therefore, reliable scale-up procedure/criteria are required to design industrial-scale BCs/SBCs. To achieve this goal, it is crucial to have a comprehensive knowledge about global and local hydrodynamics of BCs and SBCs. Hydrodynamic parameters including gas holdup, bubble size distribution, bubble velocity, liquid flow pattern, solids distributions, to name a few, have considerable impacts on the performance of these units. Predictive models have usually been utilized to estimate hydrodynamic parameters in BCs and/or SBCs.

These models should comprise all influential parameters, including design parameters (sparger, column geometry, internals, etc.), operating conditions (pressure and temperature, flow rates, feed composition, solid concentration, etc.), and physical properties of materials (viscosity, surface tension, heat capacity, density, thermal conductivity, particle size, etc.). However, the available models mostly neglect the influences of many parameters, such as pressure, temperature, and solids properties.

Solid particles are generally employed in SBCs as catalysts or reactants in many chemical and biological processes. Many researchers have attempted to highlight solids’ impact(s) on hydrodynamics and SBCs’ overall performances at the macroscopic scale. They considered that the liquid phase properties, like viscosity or density, are altered by the solids, thus considered the system as a gas-slurry two-phase system. This simplified approach cannot represent all phenomena related to the bubble-solid interactions, which makes the corresponding findings dubious.

In general, available hydrodynamic and heat and mass transfer models in BCs and SBCs are highly simplified. Therefore, they cannot properly estimate required data to design a BC or SBC as they do not include all influential parameters. When focusing on SBCs, some intrinsic properties of solids are ignored, while the proposed models for SBCs mainly neglect the effects of operating conditions. Therefore, it is necessary to develop reliable phenomenological models for hydrodynamics, which can be applied to various process situations, in BCs and SBCs. To develop these models, comprehensive studies should be accomplished to increase our knowledge about hydrodynamics of BC and SBC, and, consequently, to properly design (slurry) BCs.

Phosphate ore is used to produce fertilizer and phosphoric acid. A trace amount of heavy metals in phosphate ore has harmful impacts on the kidney, liver, and prostate. Considering the legislative restrictions, heavy metals removal from phosphate ore is essential. A significant removal has been reported after a lengthy processing time (residence time of > 30 min), resulting in a decrease in the ore’s reactivity and depression of the phosphoric acid production. Accordingly, high-temperature processing of phosphate ore under a reductive environment at lower temperatures (~800 ℃) is applied as a promising approach to remove more than 70 wt.% of some of the heavy metals while the reactivity of the product remains high enough to be employed for phosphoric acid production.

The phosphogypsum is a by-product of the phosphoric acid industry. Although its calcium and sulfur contents are important, the recovery of this material remains very limited. The remainder is either thrown into the sea or disposed of in piles depending on the regulations applied in different countries. The phosphoric acid industry is the greatest consumer of sulfuric acid. As a result, the development of an industrial process capable of decomposing phosphogypsum with carbon monoxide (CO) to calcium monoxide (CaO) and sulfur dioxide (SO2), which will be recycled to produce sulfuric acid, presents a very attractive solution, particularly, for counties that produce phosphoric acid but do not have sufficient sulfur resources. The goal of this work is to investigate and develop the kinetic models for different pathways to decompose phosphogypsum with CO.

Phosphorus is a non-renewable source and one of the three irreplaceable macronutrients for life, in addition to nitrogen and potassium. The phosphate ore is acidified by sulfuric acid to produce phosphoric acid by wet process. Although the wet process is an economical route, it suffers from many technical problems and leads to many environmental problems due to the production of phosphogypsum as a by-product. The objective of our project is to understand the mechanisms and study kinetics of high temperature reduction of phosphate ore as a key step in the thermal process that could be an alternative slution of wet process acid.