Study of cut point density and process performance of Floatex density separator in fine coal cleaning

Abstract

Advanced gravity separation of a high-ash (36%) semi-coking coal in a Floatex density separator (FDS) is investigated. The influence of the operating variables on the separation features has been identified. It is established that a higher bed pressure and a higher teeter water flow rate enhance the mass yield of the clean coal albeit with a poorer grade. A higher bed pressure reduces the bed voidage leading to a higher cut point density. Although bed voidage is reduced due to higher teeter water rate, the hydraulic transport increases significantly. A higher pulp density and a higher feed rate introduce severe hindered settling conditions leading to an increase in the cut point density. This results in a poorer product grade with a higher yield. The optimum condition for 23% product ash in a single-stage operation is identified. The yield at the optimum condition is found to be 64.3% which is close to the theoretical maximum for this coal. The dependence of the cut point density as well as Ecart probable (Ep) value on the operating variables is quantified. A specific gravity of separation of below 1.8 and an Ep value of around 0.15 is achievable under controlled operation of the FDS.

Conventional and recent advances in gravity separation technologies for coal cleaning: A systematic and critical review

“…Solid particles in the feed slurry settle down under the gravitational field against the rising current of water. The heavy gangue particles settle down to form a bed while lighter coals are carried to the overflow stream [ 155 , 156 ]. In coal cleaning, FDS is used as a pre-concentrator and/or a classifier prior to other separation processes.…”

“…In coal cleaning, FDS is used as a pre-concentrator and/or a classifier prior to other separation processes. Teeter water flowrate, bed pressure, set-point, feed rate, and pulp density are the important parameters affecting separation [ 155 , 156 ]. It was also found that higher bed pressure and higher teeter water flowrate could enhance the yield of clean coal albeit with poorer grade [ 156 ].…”

Simulation Algorithm for Water Elutriators: Model Calibration with Plant Data and Operational Simulations

“…The different types of hydraulic classifiers are presented in the work of Tripathy et al [4] and the one studied here is the floatex density separator. Hc units have been the subject of several studies and publications (Bazin et al 2011(Bazin et al -2012, Das et al 2007Das et al -2010; Sar et al 2017 [11]; Sadeghi and Bazin 2020 [12], among others). Generally, the prevailing separation mechanisms in an Hc are hindered settling, elutriation and fluidization [4,13].…”