Simultaneous ignition of several droplets of coal–water slurry containing petrochemicals in oxidizer flow

• Ignition conditions and characteristics different for single and several droplets.
• The relative position of droplets affects ignition conditions characteristics.
• The first droplet acts as “thermal protection” for subsequent droplets.
• The first droplet can be as accelerator of subsequent droplets combustion.
• Ignition delay times can differ about 70% for droplets in the group.

This paper examines ignition features of coal–water slurry containing petrochemicals (CWSP). Fuel slurry composition is based on a filter cake (typical processing waste) of coal (grade K), water, scavenged turbine oil, and plasticizer. The novelty of this paper is that it indicates a joint influence of several droplets on the CWSP ignition characteristics in an oxidizer flow (air). Its temperature and velocity vary in the range of 400–1200 K and 0.5–5 m/s. These ranges are chosen so as to yield optimal results that can be used in various fuel technologies and waste recycling. The study examines the cases of two, three, four, and five droplets. It is considered that droplets are arranged differently relative to each other (in parallel, in series, and in rhomb) in the oxidizer flow. The distances between droplets are also different; here, they vary from 0.5 mm to 1.5 mm. The diameter of each droplet is about 1 mm. The study specifies the ignition delay time for CWSP. Special facilities, such as high-speed cameras, cross-correlation systems, a hollow glass cylinder (representing a combustion chamber), are used to monitor the basic parameters of ignition. Tema Automotive and Actual Flow software allow processing of the experimental results. Experiments demonstrate that the local sources of heterogeneous combustion are formed when CWSP droplets are burning. Such formation is characterized by some features, since droplets are spaced differently in the group relative to the oxidizer flow. Finally, the paper discusses the joint influence of neighboring droplets on the conditions and characteristics of their sustainable combustion.

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