Process Variables and Operating Regimes
Variables involved in mineral processing units characterize process states relatively to material quantities (extensive properties) or qualities (intensive properties). Mass or volume flowrates and hold-ups of solid, liquid, slurry and gas phases (or of given species within these phases) belong to the first category, as well as other related variables such as levels and flowrates. The second category frequently includes the following variables:
• concentrations of chemical species or minerals in solid, liquid and gaseous phases;• solid percentage in slurries;• particle size and density distributions;• concentrations of chemical species or minerals in particle size or density classes;
• pressures, temperatures.
Process variables may or may not be directly measured by sensors or analytical devices. For instance, ore flowrates may be obtained through the information given by a slurry volume flowmeter, a density gauge, and ore specific gravity measurement. Metal flowrates are other examples of process variables that are obtained through a combination of measurements (flowrates and concentrations).There is no unique way to select the set of variables X that characterize process states. The structure of the models and constraints describing a process behavior depends upon variable selection. This will have an impact on the observation or data reconciliation method,although the resulting values of reconciledstates should not rest upon the problem for mulation,if consistent information processing methods are used. Similarly, the measured values Y of the Z process variables used as input to the reconciliation procedure may or may not be raw measurements of the process states X. Furthermore, they can be obtained by combining several sources of raw measurements. The structure of the database Y and of its uncertainties may have a significant impact on the reconciliation method and sometimes on the reconciled results.
The variation of the process states X as a function of time depends on the intrinsic dynamics of the process, on the variations of the operating conditions applied to the process, and on the disturbance dynamics. The process operating regimes can be classified into six types:
• the steady-state regime, when all the process input and state variables are constant;
• the stationary regime, when the process dynamics are limited to random variations around a steady-state regime;
• the transient regime, where the process evolves from one steady-state to another one;
• the quasi-stationary regime, which corresponds to stationary random variations around persistent mean value changes;
• the cyclic regime, when the process operates cycles of production, such as in the carbon-in-pulp process where the carbon transfer is cyclic, or in smelting processes where the material is cyclically cast;
• the batchregime,whenthe states evolved according to a trajectory from an initial state to a final state.PUDA is a 28-year’s leading, growth-focused manufacturer of packing equipment and custom-engineered and integrated plant-wide system for dry bulk powders, flakes, and granules! PUDA-International Inc. is a Canadian based company located in Great Vancouver, Canada in 2004. Puda owns world famous partners like Southern Copper Corp. Rio Tinto Group, Zijin Group, LG China, OT Group, FL Smith, MCC,KAZ Minerals PLC and E.Mix and ECUACORRIENTE S.A.
