CFD Modeling of Pulverized Coal Combustion Using Relax to Chemical Equilibrium Model With Turbulence-Chemistry Interaction

A comprehensive numerical investigation of 2.4 MW IFRF swirl-stabilized coal furnace is conducted. A novel Relax to Chemical Equilibrium (RTCE) model with turbulence-chemistry interaction is used for the gas-phase combustion and the results are compared with the standard Eddy Break-Up (EBU) model. In the RTCE model, the species compositions are relaxed towards the local chemical equilibrium at a characteristic time scale determined by the local flow and turbulence. The turbulence-chemistry interaction is treated using the Eddy Dissipation Concept (EDC) model. The simulation uses a Lagrangian-Eulerian framework to treat the particle transport and the fluid-particle interactions. In all, fifteen species have been included in the RTCE model. For coal particles, a one-step devolatilization, first-order char oxidation, particle porosity, and particle radiation models are employed. The NOx emissions model includes both thermal and fuel NOx pathways. It was found that RTCE model performs well in predicting the overall temperature distribution in the IFRF coal furnace. The predicted temperature, NOx and CO at the outlet match very well with the experimental data, showing marked improvement over the EBU model. The overall NOx profile is also predicted better by the RTCE model.

Surface Complexation Models of Pertechnetate on Biochar/Montmorillonite Composite—Batch and Dynamic Sorption Study

The study summarizes the results of monitoring the properties of two types of sorbents, BC1 (biochar sample 1) and BC2a (biochar sample 2), prepared by pyrolysis of bamboo biomass (BC1) and as its composite with montmorillonite K10 (BC2a). The main goal was to study their applicability to the Tc (VII) separation from liquid wastes, using NH4ReO4 as a carrier. The research was focused on determining the sorbents surface properties (by XRF (X-ray fluorescence) method and potentiometric titration in order to determine the properties of surface groups—Chemical Equilibrium Model (CEM) and Ion Exchange Model (IExM) models were applied here). As well as monitoring Tc (VII) (+Re(VII)) sorption, especially to determine equilibrium isotherm, the influence of pH and kinetics. The subject of research was also the dynamics of sorption, including its mathematical–physical modeling. Both sorbents have good properties against Tc (VII), however BC2a, due to the presence of montmorillonite, is more advantageous in this respect. It has a higher sorption capacity and faster kinetic investigation. An important finding is that the optimal pH is 2–3, which is related not only to the protonation of surface groups (they have a positive charge), but also to the negative form of the existence of Tc (VII) and Re (VII): TcO4− and ReO4−.

Development of a Chemical Equilibrium Model of the Downdraft Fixed Bed Gasification Process with known Product Temperature, Using air as an Oxidizing Agent

A chemical equilibrium model for known outlet temperature of the products was carried out on a downdraft fixed bed gasifier. Biomass from oil palm kernel is used with proximate and ultimate analysis; the general gasification reaction takes into account the biomass moisture, the reaction products are formed by CH4, H2O, N2, CO, CO2 and H2. The model is described in detail and the equations are solved using the EES software. The model shows the results obtained for temperature ranges from 500 K to 1500 K and 1.0 atm. The model is validated by direct comparison of the gas composition with the results reported in the literature for similar conditions, obtaining favorable results.