The development of a New Process for Phosphate Thickening

In phosphate beneficiation process, thickening is used to concentrate the slurry or sludge in order to increase its solid content and recover the maximum of water. The addition of flocculants helps to form larger particles that can thicken out quickly. However, the high consumption of flocculant in the thickeners increases the cost of the operation. The purpose of this research is to study the effect of flocculant on sedimentation velocities of different particles size in order to develop a new thickening process which ensure the maximum thickening rate and a minimum flocculant consumption.To achieve this goal, initially the impact of flocculant on different size fraction was studied. The objective of this step is to define the cut-size from which the flocculant has no considerable effect on thickening. This granulometric slice can decant by a simple free sedimentation without needing the flocculant. After that, a hydrocyclone was dimensioned and modeled in order to eliminate this granulometric slice which will undergo free sedimentation. This allowed to design a new thickening technology that targets only fine particles overflow of the hydro-cyclone and that require the addition of flocculant. This technology will significantly reduce the flocculant consumption and ensure a better water recovery in the thickening process

Search for an L-mu - L-tau gauge boson using Z -> 4 mu events in proton-proton collisions at root s=13 TeV

A search for a narrow Z' gauge boson with a mass between 5 and 70 GeV resulting from an L-mu - L-tau U (1) local gauge symmetry is reported. Theories that predict such a particle have been proposed as an explanation of various experimental discrepancies, including the lack of a dark matter signal in direct-detection experiments, tension in the measurement of the anomalous magnetic moment of the muon, and reports of possible lepton flavor universality violation in B meson decays. A data sample of proton-proton collisions at a center-of-mass energy of 13 TeV is used, corresponding to an integrated luminosity of 77.3 fb(-1) recorded in 2016 and 2017 by the CMS detector at the LHC. Events containing four muons with an invariant mass near the standard model Z boson mass are analyzed, and the selection is further optimized to be sensitive to the events that may contain Z -> Z'mu mu -> 4 mu decays. The event yields are consistent with the standard model predictions. Upper limits of 10(-8)-10(-7) at 95% confidence level are set on the product of branching fractions B(Z -> Z'mu mu)B(Z' -> mu mu), depending on the Z' mass, which excludes a Z' boson coupling strength to muons above 0.004-0.3. These are the first dedicated limits on L-mu - L-tau models at the LHC and result in a significant increase in the excluded model parameter space. The results of this search may also be used to constrain the coupling strength of any light Z' gauge boson to muons. (C) 2019 The Author(s). Published by Elsevier B.V