Combustion of the foamed emulsion containing biochar microparticles.

Foamed emulsion containing biochar particles can serve as a perspective type of fuel for contemporary power engineering. Such a combustible system represents a multiphase system consisting of oxygen bubbles dispersed in the oil-in-water emulsion which in turn contains biochar microparticles. The paper considers the issues related with combustion of foamed emulsion containing biochar particles. In the process of experimental study we determined the dependencies of flame speed in the foamed emulsion on the concentration of biochar microparticles for different types of aliphatic hydrocarbons (hexane, heptane, isooctane and nonane). It is found that the use of biochar microparticles could lead to rather significant increase in total burning rate of the foamed emulsion. Thus, for example, the addition of biochar particles into the isooctane-based foam leads to the four-times increase in total burning rate. Herewith, the dependence of total burning rate of the foam on the biochar particles concentration is non-monotonic, so the maximum burning rate is achieved at some moderate biochar particles concentration. With the help of laser-lighted photography of multiphase flow the experimental data is obtained for the diameter of water droplets forming in the process of foamed emulsion decay during its combustion. It is obtained that biochar particles favor finer dispersing of liquid phase of the foam since they represent by themselves heterogeneous centers of vapor bubbles nucleation. In turn the diameter of water droplets defines the heat losses from the flame front and therefore the flame speed. On the basis of simple phenomenological representations we obtained the estimate for flame speed in the foamed emulsion containing biochar microparticles. Obtained relations makes it possible to substantiate the non-monotonic manner the total burning rate depends on the biochar microparticles content in the emulsion. [ABSTRACT FROM AUTHOR]