Coal-water slurry atomization in a new pneumatic nozzle and combustion in a low-power industrial burner

Abstract A new pneumatic nozzle for spraying coal-water fuel based on the near-wall and cumulative jets and Coanda effect has been tested. The mechanisms and characteristics of CWS spraying and combustion have been investigated. To prepare the CWS, Kuznetsk oxidized coal of grade D (long-flame) was used in proportion to water of 55/45. The disperse composition of water and CWS droplets was measured at the nozzle outlet using the shadow photography method. The characteristic size of liquid CWS droplets in the ignition region is 20 µm. At the same time, the flow contains coal particles with a size of about 100 µm. This size of particles is sufficient for efficient combustion. The principle possibility of efficient joint combustion of CWS and pulverized coal fuel with the help of the developed burner is shown at the uncooled fire setup with an uncooled 5-MW furnace. The experiments were carried out at a power of 1 MW and water content in CWS of 45%. NOx emissions meet the MPC requirements for coal-fired boilers. Emissions of other substances are close to zero even with suboptimal operating and design parameters. The results obtained can be used in numerical simulation of the processes of CWS dispersion and combustion. Further work should be aimed at optimizing operating parameters in application to industrial conditions and at developing practical recommendations for boiler design.