Limiting Conditions for Droplet Fragmentation of Stabilized Suspension Fuels

Abstract

The main barrier to the wide use of composite liquid fuels in the energy sector is the significant sedimentation of solid particles during fuel storage and transportation. As a result, the composition of fuel slurries changes quite fast and considerably when yet another portion of fuel is pumped from a storage tank. Stabilizing additives are one of the possible solutions to this problem. The technology of primary and secondary slurry fuel atomization is generally considered promising for obtaining a spray of small fragments (droplets and particles). This way, droplets of liquid components and solid particles can be produced with a size of less than 10 μm. A fuel aerosol with particles and droplets this small burns out rapidly. The most effective secondary droplet atomization technology is based on their microexplosive breakup in combustion chambers by superheating the water in the fuel to exceed its nucleation (boiling) point. As part of this research, we studied the impact of the main stabilizing additives to slurry fuels on droplet breakup behavior: heating time until breakup, breakup delay and duration, and the number, size, and velocities of secondary fragments. Soy lecithin and sodium lignosulfonate were used as stabilizers. The main components of the fuel slurries were water, rapeseed oil, diesel fuel, coal processing waste (filter cake), coking bituminous coal, soy lecithin, and sodium lignosulfonate. Droplets were heated at an ambient gas temperature ranging from 450 to 1050 K until the breakup conditions were achieved. Mathematical expressions were obtained for the relationship between input parameters and the key characteristics of the process. Principal differences and overall patterns of droplet breakup were established for slurries with and without stabilizing additives.

Keywords

• coal–water slurries
• stabilization
• additives
• microexplosive droplet breakup
• microexplosion
• child droplets