Airborne Dust Capture and Induced Airflow of Various Spray Nozzle Designs

Abstract

Water spray characteristics, including droplet size and velocity, airborne dust capture potential, and induced airflow quantity for various spray nozzle designs were evaluated to provide basic information for improving spray applications. Water droplet size and velocity characteristics were initially measured by a Phase Doppler Particle Analyzer (PDPA) for hollow cone, full cone, flat fan, and air atomized spray nozzles at similar operating parameters. Airflow inducement and dust capture experiments were also conducted under the same operating parameters to examine any salient features of the spray nozzle type, droplet characteristics, induced airflow, and airborne dust capture.Test results indicate that there are trade offs between airflow inducement and dust capture efficiency. A spray nozzle with a wider discharge angle was observed to induce more airflow, but at reduced dust capture efficiencies. Increasing spray nozzle fluid pressure(s) generally reduced water droplet sizes with concurrent increases in droplet velocity, airflow inducement, and airborne dust capture. Placing a three-sided barrier around the spray nozzles normally reduced spray air induction and increased dust capture efficiency. A direct relationship between airborne dust capture efficiency and spray input power normalized per unit of airflow induced was observed. This information can be utilized to improve the performance of water sprays for reducing airborne dust levels.

Open-air sprays for capturing and controlling airborne float coal dust on longwall faces

“…Six of the included sprays had been tested previously by Pollock and Organiscak (2007) for respirable dust capture efficiency, airflow inducement and various spray droplet characteristics. Gemci et al (2003) had measured the water droplet Sauter mean diameter (SMD) and mean velocity, V , for these same sprays using a Phase Doppler Particle Analyzer at two distances along the nozzle axis under the same operating parameters.…”

“…For example, Kost, duBreuil and Saltsman (1979) found that, independent of spray type selected, sprays oriented downstream in a 0.5-m/s (100-fpm) tunnel were 20 to 30 percent more effective at controlling airborne dust than those oriented upstream. More recent investigations by NIOSH examined spray airflow inducement and its effect on respirable dust capture potential (Pollock and Organiscak, 2007). This effort found that open-air, or unconfined, sprays with high airflow inducement did not necessarily result in higher rates of airborne dust capture, though higher pressures globally produced higher droplet velocities and improved capture efficiencies.…”

Development of a Respirable Dust Mitigation System for a High Longwall Face at Sihe Colliery in China – a Case Study

“…Despite the dust control measures available, field practice has demonstrated that the control of respirable dust in longwall faces is very difficult and often ineffective [13][14]. This is particularly true in the Shihe colliery, where the dust concentration, particularly respirable dust, at its high longwall faces often exceeds the maximum allowable dust limit.…”

Empirical engineering models for airborne respirable dust capture from water sprays and wet scrubbers

“…Other researchers more simply related several empirical spray operating parameters to airborne dust capture. Common spray operating parameters studied include spray operating pressure, water flow rate, water flow to airflow ratio and spray power to airflow ratio (Jayaraman, 1982; Jones and James, 1987; Organiscak and Pollock, 2007; Pollock and Organiscak, 2007). …”

“…Spray nozzle parameters such as orifice diameter are directly related to water quantity at constant pressure, while discharge angle is indirectly related to droplet size and velocity at constant pressure (Streeter and Wylie, 1979; Pollock and Organiscak, 2007; Klima et al, 2017). Water spray operating pressure is indirectly related to water droplet size and directly related to water droplet velocity for a particular spray nozzle (Cheng.…”