Dwarikanath Ratha

Influence of Particle-Size Distribution and Temperature on Rheological Behavior of Coal Slurry

The rheological behavior of coal-water slurry of Indian coal is studied using rheometer. The effect of particle size, solid concentration, and temperature on the rheology of the coal-water slurry has been investigated. The settlement analysis of various size ranges of coal particles has been carried out. A particle size less than 75 µm is used for analysis of rheological behavior of coal slurry and it is found that the increase in solid concentration caused the increase in apparent viscosity of the coal-water mixture. Also, it is observed that as the solid concentration increases the coal-water mixture converts to a non-Newtonian fluid. The rheological behavior of the slurry is also analyzed by blending the coal samples with mixture of coarse and fine particles, hence making a bimodal particle-size distribution. The slurry having the bimodal particle-size distribution is prepared by blending the fine particles of 53–75 µm with the coarse particles of 106–150 µm or 150–250 µm with various proportions. The optimum fraction obtained in bimodal slurry sample is 30% at which point the apparent viscosity is minimum. The change in the flow behavior of coal slurries are fitted to rheological models and the model parameters are calculated.

Virus Transport through Unsaturated Zone: Analysis and Parameter Identification

AbstractThis paper presents numerical and parameter estimation models for the analysis of virus transport and the identification of transport parameters in the unsaturated zone. The numerical model couples a mass conservative fully implicit finite difference model simulating moisture flow in the unsaturated zone with the hybrid finite volume model for virus transport. The accuracy of the numerical scheme is tested for both advection- and dispersion-dominated transport. The comparison of the numerical model with the analytical solution indicates that the numerical model’s predictions are in excellent agreement with the analytical predictions. The parameter estimation is formulated as a nonlinear least-squares minimization problem in which the parameters are estimated by minimizing the deviations between the model-predicted and experimentally observed virus concentrations. A parameter estimation procedure is developed by coupling the numerical model simulating one-dimensional virus transport in the unsatura...

Structural Modeling and Analysis of Water Resources Development and Management System: A Graph Theoretic Approach

An attempt is made to develop an integrated system model for the structure of water resources development and management system. The system consists of five subsystems such as watershed management, groundwater development, surface water management, field level development and climate change along with interactions between them. The system is first modelled in the form of hierarchical tree and integrative block diagram for better understanding and analysis. Graph theoretic and matrix models are then developed for storage, retrieval and computer processing. Variable permanent matrix model and variable permanent function in the form of multinomial are the structural models of the system and characterize the water resources development and management system conclusively. Permanent function presents a powerful and exhaustive analysis procedure to generate alternate solutions for the decision makers for the benefit of stakeholders. Coefficient of similarity and dissimilarity are useful matrix for comparing different solutions. SWOT analysis is proposed before taking final and optimum decision on different issues related to water resources development and management system. An illustrative example of groundwater development subsystem is taken to demonstrate the application of methodology.

Physiochemical and leaching characteristics of fly and bottom ash

ABSTRACT Bottom ash and fly ash are the by-products of coal in thermal power plants. They are the combustion wastes and contain many elements that may harmful to the environment. The present study investigates the physiochemical, mineral, and leaching characteristics of an Indian coal ash (bottom ash and fly ash). From the characterization of bottom ash and fly ash, it is found that the ash samples are enriched predominantly in silica, alumina, and iron oxides. A series of leaching experiments have been performed to analyze the tracing elements of metal at the different liquid to solid ratio (L/S). The L/S varies from 20:1 to 80:1. From the leaching results of the fly ash and bottom ash data, it is observed that the tracing elements of Mn, Mg, Cr, Zn, Ni, Pb, Fe, and Cu are the most abundant elements, while Hg, Mo, and Co are the least abundant elements.

A FINITE VOLUME MODEL FOR THE SOLUTION OF THE ADVECTION-DISPERSION EQUATION

ABSTRACT The present study is concerned with the modeling of conservative as well as non-conservative solute transport in ground water. The model is based on an operator split approach which uses an Eulerian frame work with finite volume method for the advective transport and fully implicit central difference method for the dispersive transport. This formulation helps in accurately simulating both highly advective and dispersive transport cases with less restriction on the grid size and time step. The numerical solution is compared with exact as well as the approximate analytical solution and the maximum error as percentage of peak concentration is presented for different values of decay constant at varying distances. It is found that finite volume method provides accurate solutions of both conservative and non-conservative solutes for both advection and dispersion dominated situations.

Computational analysis on disposal of coal slurry at high solid concentrations through slurry pipeline

ABSTRACT The present study is conducted to investigate the flow characteristics of coal–water slurry having high solid concentrations in slurry pipeline using commercial computational fluid dynamics. An Euler–Lagrange multiphase approach is used to simulate the flow of coal–water slurry in 50, 100, and 150 mm diameter straight pipelines. The simulations are carried out using various turbulence models and the results obtained are compared with the experimental results presented in the literature. It is found that the shear stress transport (SST) k–ω turbulence model shows good agreement in comparison to other turbulence models. The SST k–ω turbulent scheme is used to solve the governing equations of two-phase model. Simulations are carried out for coal slurry velocity range 2–5 m/s. Numerical simulation results show that the pressure drop in pipeline increases non-linearly with increase in velocity, solid concentration, and particle size. Extensive simulation is also carried out to estimate the effect of pipe diameter on the pressure drop characteristics through pipeline. It is observed that the pressure drop decreases with the increase in pipe diameter. It is found that the particle sizes have significant influence on pressure drop, solid concentrations, and velocity distributions during the flow of coal–water slurry in a pipeline.