INTRODUCTION

The issue of air pollution is getting more and more highlighted at present days all over the world, in particular, dust emission and control is one of the priorities of policy in many countries, developed or not.

According to Hans Bruyninckx, the European Environment Agency (an Agency of EU) Executive Director, “Air pollution harms human health and the environment. In Europe, emissions of many air pollutants have decreased substantially over the past decades, resulting in improved air quality across the region. However, air pollutant concentrations are still too high, and air quality problems persist. A significant proportion of Europe’s population lives in areas, especially cities, where exceedances of air quality standards occur: ozone, nitrogen dioxide, and particulate matter (PM) pollution pose serious health risks. Several countries have exceeded one or more of their 2010 emission limits for four important air pollutants. Reducing air pollution therefore remains important.

 

IS MISTING A SOLUTION?

The use of misting is widely recognized as one of the methods to achieve dust and PM suppression and containment.

The techniques of water misting/water curtains: The moistening of bulk materials is a practically proven technique to prevent dust formation from loading/unloading activities. The misting can be carried out by using a permanent installation or mobile containers (e.g. tankers). Water curtains are, e.g. used to keep dust in the hopper when grabs are opened above the water curtain

HOW DOES IT WORK

Misting systems, used in PM10 pollution suppression, behave themselves like a combination of a “wet scrubber” (i.e. a device that removes pollutants from gas streams through sprays or fluid streams interacting with the gas stream itself) and a filter.

Indeed, the wall of nebulized water acts as a filter which makes it impossible for the particle of dust to pass through it without colliding with any drop produced by the misting system. This phenomenon is known as the agglomeration process. After the p

article of particulate is absorbed by the water drop, the mass of the latter tends to increase, making it fall to the ground by the effect of gravity and with it the particle inside it.

When using misting, one of the primary considerations is the droplet size. If the droplet diameter is much greater than the diameter of the dust particle, the dust particle simply follows the air streamlines around the droplet. If the water droplet is of a size comparable to that of the dust particle, contact occurs as the dust particle follows the streamlines and collides with the droplet

UNDERSTANDING DROPLET SIZE

The process of generating drops is called atomization. The process of atomization begins by forcing liquid through a nozzle. The potential energy of the liquid (measured as liquid pressure for hydraulic nozzles or liquid and air pressure for two-fluid nozzles) along with the geometry of the nozzle causes the liquid to emerge as small ligaments. These ligaments then break up further into very small “pieces”, which are usually called drops, droplets, or liquid particles.

DUBITECS, in cooperation with its sister company, DUBICOOL, which specializes in high-pressure misting and fog systems, offers a wide range of solutions to suppress dust in indoor and outdoor spaces.

 

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