Hybrid modeling method of dust suppression efficiency for dry fog dust suppression process

The original mechanism model of dust suppression efficiency for dry fog dust suppression could not guide the actual process. In order to accurately predict the dust suppression efficiency in the process, a new mechanism model was established by my analysis of the process. But there were some factors that I could not establish the model. So a hybrid model combining mechanism model and support vector machine (SVM) was proposed. Using the data of dry fog dust suppression oval process, the hybrid model was simulated. The simulation results show that the hybrid model can accurately predict the dry fog dust suppression.

The influence of floating spheres on evaporation suppression under different climatic conditions

<p>Global warming and population growth increase the need for better management of freshwater resources, in particular in arid and semi-arid regions. Due to increased rainfall variability,  reservoirs became a vital management tool that stores the water during rainfall, thus decrease flood risks and supply water during drought periods. However, large amounts of water are lost by evaporation, which markedly affects reservoirs’ function of ensuring water availability. In Egypt, about 20.0% of the country's Nile share (12.1 to 15.4 billion m<sup>3</sup>) are lost annually by evaporation from Lake Nasser. The floating covers, i.e. spheres, shade the water surface and act as a physical barrier that decreases energy flux into the water, thus decrease evaporation. Studies that compare the evaporation suppression efficiency of the floating covers, over different climatic conditions, while considering its impact on the water ecology are limited.</p><p>A field experiment in an outdoor setting (class A-pan) was conducted for nine months (March to November) in two locations that vary in their climatic conditions, i.e. Aswan and Damanhur, representing northern and southern Egypt, respectively. The water surface was covered by white, black, or multicolor spheres, in addition to the control. Daily evaporation rate (ER), water temperature (WT), evaporation suppression efficiency (ESE), were determined. Moreover, the microalgae growth was measured as an indicator of water ecology.  </p><p>Obtained results revealed massive evaporation losses from the uncovered water surface (control) in Aswan location, in which the nine-month average was 2.25 times higher than in Damanhour location. The floating spheres reduced ER in both locations, in particular the white spheres. The ESE in Aswan was less than in Damanhour location. The ESE in Damanhour was 63.38, 58.13, and 54.8%, while in Aswan was 48., 42.5, and 41.6% for white, multicolor and black spheres, respectively. Floating spheres decreased WT in the morning and mid-day, while in the evening the control treatment was the coldest, indicating partial isolation of covered water surface. Irrespective of the spheres’ color, the spheres had no detrimental effect on microalgae growth, indicating enough light penetration and gas exchange through the gaps between spheres.</p><p>In conclusion, the floating spheres is an effective mean for evaporation suppression and its efficiency is dependent on the climate and spheres’ color. The ESE of spheres is lower in environments with lower relative humidity. The white spheres are recommended for evaporation suppression without negative impacts on microalgae growth which could be a viable indicator for the ecology of the water ecosystem. Further studies on larger water reservoirs are needed while considering several aquatic organisms.</p>

Effects of Metamorphic Degree of Coal on Coal Dust Wettability and Dust-Suppression Efficiency via Spraying

Currently, spraying is a main means for dust prevention and control in underground coal mines. The dust-suppression efficiency via spraying is highly correlated with the wettability of coal dusts. There are many factors affecting the wettability of coal dust, among which coal’s metamorphic degree has great influence. In order to gain in-depth knowledge of the effects of coal metamorphic degree on coal dust wettability and the dust-suppression efficiency via spraying, 6 coal dust samples with different metamorphic degrees were collected and used in the study. In the experiments, the microproperties, wetting performance, and dust-suppression efficiency via spraying were measured. According to the experimental results of coal’s microproperties, with the improvement of metamorphic degree, the content of hydrophilic oxygen-containing functional groups on the surface, the surface roughness, the specific surface area, and the interpore diameter all decreased. In addition, as coal’s metamorphic degree was enhanced from lignite to meager-lean coal, the wettability of the coal dust dropped. On the other hand, as the metamorphic degree of coal quality continued to be improved to anthracite, the wettability of the coal dust increased instead. The measured results revealed that the dust-suppression efficiency via spraying was highly correlated with the wettability of coal dust. The coal dust with better wettability exhibited higher dust-suppression efficiency via spraying. With the increase of water-supply pressure, the effect of coal dust wettability on the dust-suppression efficiency via spraying was weakened, and the difference of dust-suppression efficiency among different coal dust samples was narrowed.