Papers by Keyword: Chemical Reactions

Abstract: In this article, the mass and heat balance calculations of underground coal gasification process for thin coal seams in faulting zones of Lvivskyi coal basin (Ukraine) are defined. The purpose of the research is to establish regularities of heat and mass balance changes in faulting zones influence due to usage air and oxygen-enriched blast. A comprehensive methodology that included analytical calculations is implemented in the work. The output parameters of coal gasification products for the Lvivvyhillia coal mines are detailed. The heat balance is performed on the basis of the mass balance of underground coal gasification analytical results and is described in detail. Interpretations based on the conducted research and investigation are also presented. Conclusions regarding the implementation of the offered method are made on the basis of undertaken investigations. According to conducted research the technology of underground coal gasification can be carry out in the faulting zone of stable geodynamic and tectonic activity. The obtained results with sufficient accuracy in practical application will allow consume coal reserves in the faulting zones using environmentally friendly conversion technology to obtain power and chemical generator gas, chemicals and heat.

Abstract: The formula and calculating method of specific heat ratio in confined explosion with small explosive charge volume ratios under considering chemical reactions of the detonation products was researched. Taking the TNT explosive as an example, a numerical calculating program was written, and the specific heat ratio of the confined explosion either considering the influence of the chemical reactions or not were calculated by the program.

Abstract: On the basis of the energy conservation and the state equation of the ideal gas, a formula of quasi-static pressures of the confined explosions calculating was derived under the constant entropy assumption of the detonation products expansion and the constant volume assumption of the chemical reactions. Taking the TNT explosive as an example, the quasi-static pressures of the confined explosion either considering the influence of the chemical reactions or not were calculated and the quasi-static pressures of the confined space were obtained

Abstract: The aim of our work is to contribute to the analysis of the structure of laminar premixed Methane-Air flames using two methods. This allows us to validate the chemical mechanisms, to know the fine structure of the flame front and to get, for a given pressure and temperature of fresh gases, the speed and the mass fractions of all chemical species of the combustion reaction. The first method is based on controlling combustion parameters of laminar premixed flame. The numerical resolution strategy used consist in the discretization of the balance equations completed by the transport properties and the thermodynamic variables expressions, as well as the kinetic mechanisms concepts of chemical reactions and boundary conditions, using the first-order finite difference spatial scheme technique. The final solution is obtained, thereafter, iteratively using a recursive method. The calculations stop when equilibrium is reached. The second method consists in the use of FDS (Fire Dynamics Simulator) in order to simulate the propagation speed of the flame for different equivalence ratio in the cylindrical combustion chamber. This geometry is used by Tahtouh et al. (2009), and Bouvet et al. (2010) in their experimental devices for calculating the flame velocity. This study examines the influence of temperature variation of unburned gases on the structure of the flame front, as well as the effect of equivalence ratio on the flame front speed, combustion products and pollutants formation that allows us to deduce which parameters ensure higher efficiency with less fuel consumption and fewer pollutants.

Abstract: The chemical hydration involves complex multiphysical processes including mass and energy transfer, chemical reactions and consequently stress development and shrinkage. This paper proposed a multiphysics numerical model to predict the kinetics cement paste. The chemical reaction theory, heat transfer theory, diffusion theory, and continuum mechanics were coupled in the theoretical model. A comprehensive theoretical model is established with partial different equation system, auxiliary functions, and typical boundary conditions.

Abstract: The removal of oxygen during sintering by carbothermic reduction and the resulting carbon loss were studied for steel compacts prepared with the compositions Fe-3%Cr-0.5%Mo- 0.5%C and Fe-1.5%Mo-0.5%C, respectively, prepared from prealloyed powders. The compacts were prepared by pressing at 600 and 1000 MPa, and sintering was done at 1100 and 1300°C in vacuum. It showed that for the Cr-Mo steel, deoxidation strongly depends on the sintering temperature, in contrast to the plain Mo steel; at 1300°C very low oxygen levels were measured with the standard density compact while after pressing at 1000 MPa, still significant oxygen is contained, which is in agreement with the lower carbon loss measured. This indicates inhibition of final deoxidation by pore closure; nevertheless, the impact energy was very high and exceeded that of the Mo alloyed steels, indicating that finely dispersed oxides within the matrix are irrelevant if only the surface oxides have been completely removed.