Avaliação do comportamento dinâmico do peneiramento vibratório utilizando modelos identificados

Abstract

The presence of solids in the drilling fluid changes its characteristics influencing the drilling time, the life of the drill and the operation of mechanical equipment involved. For the reutilization of this fluid and compliance with environmental constraints, the separation between fluid and solid is required. The first step of this separation uses shale shakers in series, favoring separation and desague mud. The purpose of this study was to experimentally characterize the dynamic behavior of the sieve and relate the moisture of the retained solid with the g-force, concentration of solids fed and feed flow. Using a fluid formed by a sand slurry, water and xanthan gum (density and reology similar to real fluids), models that describe the steady and transient state were identified. The experiments followed a factorial design 2k and were conducted in a unit on a pilot scale with a 175 mesh sieve. The dynamic model was obtained by the analysis of the sieve answer about individual disturbances in independent variables (g-force, concentration of solids fed and feed flow). These data were represented by first order transfer functions plus dead time in which parameters were adjusted by Excel® software. The moisture data obtained after the stabilization of the response were used for the representation of the moisture content in the steady state. The best operating point of the sieve (lowest moisture) was 3.0 g-force; 5.0% concentration and 13 kg/min flow rate. A decrease in the concentration of solids is able to double the amount of moisture. On the other hand, feed flow had little influence on the response of the equipment. The system showed less agile transitions after disturbances in g-force, though the increase in solids concentration significantly decreased the time of the transition.