Separation

Separation-Distillation Column Internals. These are components that are assembled inside the column to enhance the distillation process. Some of these components are: flash boxes, which are mounted adjacent to overheating feeding point; support frames, which hold the rods upon which packing is placed; liquid collectors, which collects liquid trickling down from overhead packing; and vapor distributors, which help to achieve a uniform flow across the entire column.

Things to Consider: Type and materials, Installation and removal through column flange openings or manholes, Nominal diameters, Vapor feed, Phases, Side stream sources, Geometry, Liquid load, Column diameter, Cross-sectional area, Support requirements, Installation location in column.

Separation-Distillation Packaged Systems. In chemistry and chemical engineering the separation distillation processes separate substances into two or more distinct products. The distillation process separates chemical substances based upon differences in their volatilities in a boiling liquid mixture. Fractional distillation is particularly suitable for critical applications that require separation of complex mixtures such as fine chemicals and pharmaceuticals, anywhere where a finer level of purity is needed or when component’s boiling points are close. Fractional distillation equipment is available is a multiple range of sizes from the lab scale solvent recovery through processing scale.

Things to Consider: Liquid composition profile, Number of column sections, Tray/column diameters, Tray spacing, Weir heights, Number of feed streams, Number of side withdraw streams, Condenser modes (total or partial), Choice of reboiler heat exchanger with a heating agent or an external reboiler heater, Number of liquid phases in the reflux drum, Configuration of column overhead, Cooling agent flow rate, Control valves, Flow rate of outside vapor stream, Tray pressure drop, Tray efficiency, Column pressure, Liquid weeping coefficient, Material balance.

Multi-Effect Evaporators. Evaporation thermally removes a liquid from a solution, suspension, or emulsion. In evaporator technology, each evaporator is referred to as an effect. When several connected evaporators or “effects” are use in one system, it is called a multi-effect evaporator. In these systems, the product output from one effect is the feed for the next effect. The high temperature vapor that is removed from one effect is used to heat the lower temperature product in the next effect, with considerable efficiency gains. There are two feed operations: backward and forward. In backward feeds, the raw feed enters the last (coldest) effect, and the discharge from this effect becomes a feed for the next to last effect. This feed is used when the feed is cold, as much less liquid must be heated to the higher temperature of the early effects. In backward feeds, the raw feed is introduced in the first effect, and passed from effect to effect parallel to steam flow. The product is withdrawn from the last effect. This feed is used when the feed is hot.

Things to Consider: Evaporation rate, Number of effects, Water removal per pound of steam used, Capability of running many types of products with minimal or no modification, Foundation requirements, Floor space (area) needed, Modularity, Dimensions.

Reciprocating Plate Extractors. These extractors are also know as agitated liquid-liquid extractors. Common types of these extractors are reciprocating-plate extractors and rotating disc extractors. For both of these, back-mixing, which reduces column efficiency, is a problem. Agitation is needed to increase mass transfer by dispersing one of the phases and increasing turbulence in the continuous phase. In the rotating-disc extractor, the disc is the agitator. In the reciprocating-plate extractor, it is the up-and-down motion of the plate stack. Horizontal stator rings above and below each disc or impeller reduces back-mixing.

Things to Consider: Evaporation rate, Number of effects, Water removal per pound of steam used, Capability of running many types of products with minimal or no modification, Foundation requirements, Floor space (area) needed, Modularity, Dimensions.

Thin-Film Evaporators. A thin-film evaporator has two major components: a heated body and a rotor. Process fluid enters above the heated zone, and is distributed evenly over the inner surface of the body wall. Rotor blades spread the product over the entire heated wall, and generate turbulent flow in the thin liquid layer. The product spirals down the wall while turbulence, developed by the rotor, generates optimal heat flux that evaporates volatile components. The resulting vapors flow upward into a centrifugal separator, which returns entrained droplets back to the heating zone. Clean vapors pass through the vapor outlet ready for condensing or further processing. The concentrated liquid stream leaves the evaporator through its bottom conical outlet.

Things to Consider: Application, Configuration, Evaporation rate, System capacity, Feed tank capacity, Operation temperature, Scale of operation (Production/Pilot/Laboratory), Heating/power source, Display and interface, Dimensions, Weight, Warranty.

Vapor/Liquid (Cyclones & Demisters) Separators. A demister is a vertical vessel into which a liquid and vapor mixture (mist) is fed, and separated. Gravity causes the liquid to fall to the bottom of the vessel from which it is removed. The gas travels upward, and exits the top of the vessel. A cyclone is an adaptation of a centrifuge. The liquid is removed from the vapor by centrifugal force, and like the demister, gravity moves the liquid down and out, while the gas exits the top of the system.

Things to Consider: Source of entrainment, Operating temperature range, Pressure range, Vapor flow rate, Vapor velocity, Vapor density at operating conditions, Vapor molecular mass, Vapor composition or nature of phase, Liquid quantity, Liquid density, Liquid viscosity, Liquid surface tension, Composition or nature of entrainment, Droplet sizes or distribution, Solids content (dissolved or suspended), Allowable total separator pressure drop, Allowable mesh pressure drop, Allowable entrainment, Recommended mesh thickness, Vessel diameter (ID) and length, Vessel position (horizontal or vertical or inclined), Vessel shape (circular or square), Vessel type (evaporator or still or drum), Special conditions.