Distillation has remained an important separation technology for the chemical process industries. In 1997 it was reported in the journal Chemical Engineering that about 95% of all worldwide separation processes use this technology. In the USA alone, some 40000 distillation columns represent a capital investment of about US $8 billion. They consume the energy equivalent of approximately 1 billio...

In this paper, novel equipment for laboratory studies of heterogeneously catalyzed reactive distillation is described. The so called D+R tray equipment consists of a combination of conventional bubble cap trays with sections that are filled with catalyst and through which the liquid flows when it passes from one distillation tray down to the next. It is designed so that the catalyst can be easi...

A robust nonlinear control law is designed to reject unknown feed composition disturbances with overall stability. Implementation to real columns as well as comparisons with classical control strategies, show the robustness and flexibility improvements of the method. Almtracq-Using singular perturbation techniques on a physical model of distillation column, an aggregated model is proposed for c...

The thermal efficiency of a distillation column may be improved by permitting heat exchange on every tray rather than only in the reboiler and the condenser. Thermodynamic length optimizations on discrete systems specify the optimal temperature of each tray and consequently the amount of heat to be added or withdrawn in order to maintain that temperature.

BACKGROUND This study evaluated in vivo the accuracy of metal (Smart®) and plastic (Triple Tray®) dual-arch trays used with vinyl polysiloxane (Flexitime®), in the putty/wash viscosity, as well as polyether (Impregum Soft®) in the regular viscosity. MATERIALS AND METHODS In one patient, an implant-level transfer was screwed on an implant in the mandibular right first molar, serving as a patte...

PURPOSE To compare the dimensional accuracy of three impression techniques- a separating foil impression, a custom tray impression, and a stock tray impression. MATERIALS AND METHODS A machined mandibular complete-arch metal model with special modifications served as a master cast. Three different impression techniques (n = 6 in each group) were performed with addition-cured silicon materials...

STATEMENT OF PROBLEM Information regarding operators' preferences for different impression mixing techniques and duration of mixing and tray loading is limited. PURPOSE The purpose of this study was to assess operators' preferences, and the duration of mixing and tray loading using different mixing techniques. MATERIAL AND METHODS Thirty dentists, 30 dental assistants, and 30 inexperienced ...

Rotational tibiofemoral congruency and centralized patellar tracking are critical technical factors that affect the postoperative success of total knee arthroplasty (TKA). Several techniques are used to position the femoral component, but there is no validated method for achieving the ideal rotational position of the tibial component. It has been suggested that referencing the midmedial third o...