Taguchi approach for co-gasification optimization of torrefied biomass and coal.

This study employs the Taguchi method to approach the optimum co-gasification operation of torrefied biomass (eucalyptus) and coal in an entrained flow gasifier. The cold gas efficiency is adopted as the performance index of co-gasification. The influences of six parameters, namely, the biomass blending ratio, oxygen-to-fuel mass ratio (O/F ratio), biomass torrefaction temperature, gasification pressure, steam-to-fuel mass ratio (S/F ratio), and inlet temperature of the carrier gas, on the performance of co-gasification are considered. The analysis of the signal-to-noise ratio suggests that the O/F ratio is the most important factor in determining the performance and the appropriate O/F ratio is 0.7. The performance is also significantly affected by biomass along with torrefaction, where a torrefaction temperature of 300°C is sufficient to upgrade eucalyptus. According to the recommended operating conditions, the values of cold gas efficiency and carbon conversion at the optimum co-gasification are 80.99% and 94.51%, respectively.

A theoretical approach of absorption processes of air pollutants in sprays under droplet-droplet interaction.

Sprays are an important tool for removing air pollutants through absorption. To recognize the mass transport characteristics of air pollutants in sprays, four different air pollutants of sulfur dioxide (SO(2)), hydrogen chloride (HCl), ammonia (NH(3)), and nitric acid (HNO(3)) absorbed by droplets in sprays are analyzed theoretically in association with a numerical method. The number density of droplet in a spray is in the range of 10(3)-10(6)cm(-3) and the droplet radius is 30 µm. By conceiving a bubble as the sphere of influence of droplet-droplet interaction, the predictions indicate that the mass diffusion number and the number density are two important factors in determining the absorption process and results. When the mass diffusion number is larger, the radius of scavenging wave is increased and the effect of the droplet mutual interaction is thus intensified. An increase in number density facilitates the mass transfer of air pollutants from the gas phase to the liquid phase. However, the uptake amount of solutes by individual droplets is abated. At last, according to the mass distributions of the solutes in the liquid (droplet) phase, the appropriate number densities in sprays for the absorption of the four air pollutants are suggested.