Suppression of Aluminum Dust Explosion by Ca(H2PO4)2/RM Composite Powder with Core–Shell Structure: Effect and Mechanism

A Ca(H2PO4)2/RM composite powder suppressant with core–shell structure was prepared with modified red mud (RM) as the carrier and Ca(H2PO4)2 as the loaded particles, using a solvent–antisolvent process, in an attempt to suppress aluminum dust explosion more effectively. The suppression effects of the Ca(H2PO4)2/RM composite powder suppressant for aluminum dust flame propagation and for explosion overpressure were tested in a vertical glass tube test apparatus and a 20 L explosion vessel. The results show that the Ca(H2PO4)2/RM composite powder suppressant was more effective in suppressing aluminum dust flame propagation and explosion overpressure than either Ca(H2PO4)2 or RM powder alone. Finally, the suppression mechanism of the Ca(H2PO4)2/RM composite powder suppressant was analyzed. On the one hand, a large amount of burning heat was absorbed through the decomposition of Ca(H2PO4)2 and the melting phase transformation of the decomposition product; on the other hand, the strong isolation provided by the RM helped limit flame propagation. The strong adsorptivity of RM allowed this material to adsorb the radicals from the explosion reaction perfectly.

Coagulation of the Ionized Combustion Products in a Dust Flame of Aluminum Particles

The addition-agent effect of atoms of alkali metals (K, Na, Li, and Cs) and halogens (Cl and I) introduced into the combustion zone of a dust flame of aluminum particles on the average size of Al2O3 nanoparticles is studied. A physical model of coagulation of a monodisperse aerosol is proposed. The model takes into account the formation of a complex plasma consisting of positive and negative ions, electrons, neutral gas molecules, and suspended particles of the condensed phase in the combustion zone. The effect of the forces of Coulomb repulsion of unipolarly charged Al2O3 particles as well as their possible attraction by ion wind on the constant of the coagulation rate is also taken into account. It is shown that at low ion concentrations in the plasma, the coagulation rate is determined by the Coulomb repulsion of the particles, and at ion concentrations greater than 1020 m−3 the coagulation rate is determined by the attraction of the particles by the ion wind. The results of calculations of the dependence of the average Al2O3 particle size on the concentration of the additives are in a good quantitative agreement with the experimental data. The combined effect of the additives and the equilibrium products of aluminum oxide (AlO, Al, and Al2O) evaporation on the concentration of positive and negative gas ions, electrons, and Al2O3 particle size in the condensation zone is analyzed. The peculiarities of the influence of the additives of electronegative gases (Cl and I atoms) on the coagulation rate of a thermally ionized aerosol and on the particle size of Al2O3 are considered.

A Mathematical Investigation of Premixed Lycopodium Dust Flame in a Small Furnace

In the present study, a comprehensive mathematical method is developed to realize the flame expansion in the melting furnace zones. For this purpose, the furnace is composed of two zones: flame and post flame zones. Two different scenarios are covered in this research: Using lycopodium as a substitute fuel which is then converted to methane after the vaporization process, supplying the system with methane directly as a conventional fuel. The equations governing the problem with the required boundary conditions are developed and solved in each zone. The obtained results show great compatibility with the experimental findings in this research. Since lycopodium as the replacement fuel mostly contains volatile materials, one of the challenges in this study lies on understanding the effect of particle vaporization on the temperature distribution in a furnace. It is concluded that the average temperature in zones α1, α2, β1, and β2, is reduced by about 5 K, while it is increased by approximately the same amount in zones χ1, χ2, δ1, and δ2 after considering lycopodium as a fuel. Moreover, the role of vaporization and radiation on the combustion characteristics is studied in details. The achieved results from this analysis can be implemented in several industrial applications aiming for improving the energy efficiency outcome from their systems.

Simulating combustion processes based on digital technologies

The thermal power plants (TPP) make a basis of power-generation industry of the majority of countries. The global growth of power consumption and the policy of energy-saving demand to increase the efficiency of plants operation, which is, among others, determined by the technical level of steam-generating units. The up-to-date digital technologies make it possible to assess the efficiency of boiler furnace operation at the stage of boiler unit designing, its reconstruction or retrofitting and upgrading. Developed in the article are the algorithm, mathematic model and computer program of calculating diffusion-kinetic process of combustion of D-grade Donetsk coal in the coal-dust flame of boiler Е-230-14,0-520. The assigned tasks have been solved by using theoretical methods of analysis, the capabilities of devices of computer-aided calculations have utilized for visualization of results. The considered digital approach to solving technical tasks makes it possible to meet the current and future challenges.