1. Controlling the propagation of dust pollution
The above shows a transport process that occurs at clear and calm night and explains the phenomena of air pollution in a populated area located several kilometers away from the mine pit.
Below is presented a proposal of dust pollution control from the minepit and transported downstream by downslope winds as discussed above.
1.1- A benefit that occurs during the night, as the dust pollution distribution
According to that seen in Section 5 of downslope winds carry dust pollution great distances. As slopewinds are fluidic structures that move along the ground, this is the cause of the worsening of the dust problem at night time in populated areas to which these winds arrive.
On the other hand, the aforementioned concentration of dust in the cold, dense layer of air in the mine pit , is an extraordinary advantage to remove the dust. It suffices to selectively extract these layers and put them in a natural dump place that, as we shall see, is a few tens of meters above the ground.
1.2 - The selective extraction of polluted air
The selective extraction process is a process that can take place in the atmosphere near the ground by the Selective Inverted Sink units (SIS). These units, functioning in locations determined by calculations within the mine site (taking points of dust pollution generation and the topography of the site) SIS Technology is personalized to prevent the spread of dust from the mine pit.
2. Controlling dust pollution with SIS
The extraordinary concentration of the dust at the very thin cold and dense air layer (downslope wind) is a very convenient feature for extracting such polluted air. This dust must be selectively extracted from the lowest air layers and expelling it upwards to a no-danger zone. This is precisely what SIS (Selective Inverted Sinks) do for control frosts, among other applications.
The SIS technology is based on the application of the devices called Selective Inverted Sinks (SIS) which are patented in diverse countries including the US.
SIS are fans of low specific number, vertical shaft and horizontal propeller rotating axle, confined inside a cylindrical structure with a conical shaped inlet designed for reducing the energy losses at the inlet.
In a stratified atmosphere the SIS selectively drain the denser air layers (this means that the layers closer to the soil are drained before those located at larger distances). It must be pointed out that the selective drainage is a characteristic of every single stratified fluid and its study in relation with many hydraulic applications started by the middle of the 20th century.
In the stratified atmosphere this characteristic is used by the SIS for extracting in a selective way the layers located closer to the soil (the denser ones).
The SIS perform the referred extraction through its lower section (inlet) expelling the fluid through its upper section (outlet). The device may be motorized with an electric motor or a stand-alone engine.
The contaminated denser layers drained by the SIS are expelled upwards in the form of a vertical conical jet -that mixes the fluid expelled by the SIS with the fluid captured by the jet coming from the layers from the jet is passing by.
The SIS are the core devices from which the SIS technology is based on for acting under a stratified atmosphere.
As the dust air-clean air mixture contained in the upward jet is denser than the layers the jet goes through, the density of the mixture inside the jet decreases as it goes up. Also as the jet transforms its kinetic energy (which is maximum at SIS outlet) in potential energy, the flow will finally stop its way up and will remain at the layer whose density matches the mean density of the mixture contained in the jet.
The described process assures that, due to atmosphere stratification, the particles vertically impelled by the SIS can not return back to the lower layers due to the existence of the layers located at intermediate height which the jet went through in its way up. This “block” to the descent of the mixture is explained by the larger density of the intermediate layers in comparison to the density of the mixture discharged by the jets at their maximum height. Therefore the mixture will float on the intermediate layers and will propagate horizontally throughout the night.
By regulating the kinetic energy that the SIS introduce to the denser layers extracted from near the soil, it can be regulated the height over the soil at which the mixture will disperse horizontally in the stratified atmosphere.
As already explained, the layers that the jet goes through reduce their density with the height from soil (the atmosphere is stratified) and the jet, in most of the usual applications, stops its way up at a height of between 60m and 120m from soil.
In Fig. 2.1 this aspects are presented for a SIS device, using a colour scale for expressing (qualitatively) the local density of the fluid (blue means larger density than red).
Fig. 2.1–SIS device in a stratified atmosphere before sunrise. Blue means greater air density and red means less air density.
Fig. 2.2 shows how the SIS technology acts protecting a town, village or city affected by dust pollution. By comparing with Fig. 3 above, it can be seen that SIS devices placed along D section avoids the entrance of dust polluted air to the protected area.
Fig.2.2-Controlling dust pollution with SIS.
3- Conclusions
This document focus on night time dust pollution propagation in a mine pit where its generated and conducted through populated areas located several kilometers away from the mine site. Secondly it shows how to control that dust pollution through the implementation of SIS technology.
The SIS technology application can prevent the propagation of dust pollution originated in the mine site to the villages near the mine, thereby greatly improving the quality of life for their residents.
