Numerical simulation of the processes of atomization and combustion of a coal-water slurry in different-scale installations

Numerical simulation of atomization of a coal-water suspension (CWS) by a pneumatic nozzle is carried out, taking into account the processes of secondary breakup of droplets. The characteristic parameters of atomization were obtained (the dispersed jet opening angle, the size and velocity of the droplets). The data obtained were used to simulate atomization and combustion of the CWS on the firing stand. The results obtained are in good agreement with experimental data. The proposed numerical technique allows research on the introduction of advanced technologies and the improvement of existing different-scale installations (from stands to pilot industrial boilers).

Experimental studies into the effect of air pressure on the atomization characteristics of coal-water slurries

The paper studies the effect of atomizing agent pressure on the spray characteristics after spraying coal-water slurry that contains small additives of liquid waste from the pyrolysis of industrial rubber goods and used engine oil. The conducted experiments used automobile tires as the indicated rubber products; spraying was carried out employing an internal mixing pneumatic atomizer. Following the atomization of considered fuels, droplet size changes were studied using the interferometric particle imaging (IPI) technique. The spray angle was determined by means of a Photron high-speed camera. In addition, coal-water slurry containing liquid waste from the pyrolysis of industrial rubber goods and used engine oil (3–12 wt%) was sprayed to study the effect of atomizing agent pressure on the spray characteristics. A decrease in air pressure was found to reduce the spray angle by less than 6%, which resulted in the formation of rather large droplets exceeding 600 µm in size. It is experimentally confirmed that more fine droplets are formed at similar fuel and air pressures when using a spraying device equipped with an internal mixing chamber for slurry and air. The number of droplets, in this case, is 2–9% higher as compared to a typical two-component coal-water slurry fuel, with the spray angle of the sprayed coal slurry having the greatest value. When using an atomizer having an internal mixing chamber for slurry and an atomizing agent, fuel droplet breakup occurs due to the aerodynamic drag forces of the environment. Thus, the use of such atomizers reduces the number of possible breakup mechanisms for sprayed fuel droplets.

Study of making coal water slurry with lignite Pendopo coal

The Coal Water Slurry (CWS) technology increases the calorific value and changes the phase of coal from solid to liquid. The CWS Plant with a coal capacity of 1.4 t/hour located at Karawang, West Java converts lignite coal to CWS. Coal undergoes pulverizing, upgrading, and slurry-making processes to become CWS. Pulverization is the process of refining coal size into 200 mesh. The upgrading process is through reducing the moisture content in heat exchangers (HE). It occurs in HE where the coal is pressurized to 15 MPa and the temperature is maintained at 330 0C for 30 minutes. The research objective was to determine the CWS characteristics of the South Sumatra Pendopo lignite coal. The method used is through testing where the Pendopo coal is converted into CWS at the CWS Plant. The result shows that Pendopo coal which has a heating value of High Heating Value (HHV) 2,725.00 kCal/kg As Received (AR) has an increase in HHV heating value of 3,218.00 kcal/kg AR when it becomes CWS. The total moisture content of Pendopo coal has decreased from 49.36% to 44.58% when it becomes CWS. The fixed carbon content of Pendopo coal increased from 19.78% AR to 24.01% AR.