Study on designing, producing and applying effervescent atomizer in spraying system for dust suppress in production of lime stone for construction material

At present, in the world the following measures of dust control are recommended: (i) local ventilation to catch and filter dust; (ii) dust suppress at the source by spraying system. In principle, local ventilation to catch and filter dust at source is better than the later one because it can eliminate dust before it emitting to the environment. However, installation of ventilation system requires big investment and some time is not efficient because of affecting factors, for example cross-wind that brings dust out of hood. Therefore, dust suppress at source by spraying is the good choice, both economical and technical, especially for Vietnam at this time. The point is that it needs to carry out study on designing and producing  effervescent atomizer with high quality to have good efficiency of dust suppress. The National Institute of Labour Protection (NILP) is to assign to do the research on this issue and apply to lime stones processing of construction material company. The figure 1 shows the picture of effervescent atomizer designed and produced by the NILP research group.

Figure 1: Picture of effervescent atomizer

The result of measuring diameter of droplet of water by interference photograph method shows that the diameters are ranged from 6.2 μm to 62 μm, average diameter Sauter SMD (d32) from 19.7 μm to 25.5 μm. The research in lab also determines the spraying angle is 20 – 22⁰ and the maximum length of spraying jet is from 1,500 to 2,000 mm. Regarding to diameter of droplet, effervescent atomizer meets well with requirement of dust suppress because the size range of droplet covers the recommended range of droplets for dust suppress (10 – 100μm). In addition, the angle of spraying jet is small (20-22⁰) therefore air amount involved in the jet is low resulting in high efficiency of dust suppress.

The application of effervescent atomizers to dust suppress for jaw crusher of lime stones of Cam Pha exploiting and producing construction materials company serves to determine the condition of operation of spraying system as follows:

– Pressure of compressed air: P=0.5 Mpa;

– Flow rate of compressed air: Q_G = 25 l/min;

– Flow rate of water: Q_w = 1.05 l/min;

– Ratio air/water GLR=0.03;

– Average diameter Sauter SMD (d32): 42 μm;

– Angle spraying jet: (20-22⁰);

– Length of spraying jet: from 800 to 1,200 mm;

– Diameter of spraying jet at above length: 300 – 450 mm;

– Efficiency of dust suppress at source: 89.7%;

– Dust concentration at 6 m from jaw crusher reduced of 48.3% in comparing to not using spraying system.

Before the operation of atomizing system                             After the operation of atomizing system

In short, effervescent atomizer has been designed, produced and applied successfully in practice. The effervescent atomizer needs to be applied widely to improve working condition for industry of exploiting and producing lime stones of construction material as well as for other industries such as ore exploitation and production, coal mining, construction, etc.

Nguyen Thang Loi, PhD

National Institute of Labour Protection

(Source: nilp.vn)