The photo is sourced from cdn.britannica.com
Fuel oil-fired boilers and thermal power plants (TPPs) operating in Russia use the technology of staged fuel combustion. During this process, fuel oil undergoes primary atomisation: after entering the heating chamber, it gets sprayed in the form of droplets via burners. If the temperature and oxygen content in the chamber are insufficient for the fuel droplets to ignite, volatile substances contained in the droplets evaporate, as a result of which the droplets turn into solid particles that no longer burn. These particles take part in the secondary atomisation of fuel: fuel oil droplets collide with them and get granulated further, which increases the efficiency of combustion. However, if the droplets end up too big, they are more likely to reach the walls of the boiler and contaminate them with soot. The smaller the droplets, the easier they ignite and the less soot they produce.
This is why the way to make the use of fuel oil more eco-friendly lies in reducing the size of its droplets in boilers. An attempt to produce this effect has been made by the TPU scientists, who recreated the conditions characterised by a lack of oxygen and high temperature in a sublimation chamber of the boiler at the first stage of their study. This made it possible to obtain solid particles from fuel oil droplets. Microscope observation showed that the particles have a porous surface: at a low impact rate, the droplet sticks to the porous particle, while droplet atomisation requires higher rates.
The scientists followed this with bench tests, during which they filmed a collision between a fuel oil droplet and a porous particle. This was done to find out how the efficiency of atomisation is affected by the sizes of the droplet and the particle, the angle of their interaction and the velocity of the droplet. The authors of the study concluded that it is possible to reduce the specific consumption of fuel oil by almost 10% by placing the fuel-spraying burners at an angle of just under ten degrees to each other. It is also possible to increase the efficiency of fuel burnup by using a water-in-fuel oil emulsion instead of pure fuel oil. If the water content in the fuel mixture is about 10%, fuel droplets undergo microexplosions: the water heats up faster than the fuel oil, breaking up the droplets into smaller parts.
“In the future, we intend to find other ways to make the use of fuel oil more eco-friendly so as to expand its applications. For instance, we could add impurities that minimise the emissions of harmful substances such as soot and sulfur compounds,” Nikita Shlegel, one of the authors of the study and candidate of technical sciences, is quoted as saying by the Russian Science Foundation.
