Industries Information

Sample dryers are used to remove liquids from a sample through techniques such as freeze drying, spray drying, and evaporation. Drying or dehydration is a mass transfer process that causes the removal of water. There are many types of sample dryers. Examples include freeze dryers and spray dryers. A spray dryer consists of a feed pump, atomizer, air heater, air disperser, drying chamber, and systems for exhaust air cleaning and powder recovery. Spray drying is the process of mixing and drying slurry to form a homogeneous mixture of powders. The powders are mixed with a solvent, and then the mixture is sprayed into the air, so that the solvent evaporates leaving the mixed powders. By contrast, a freeze dryer freezes the material and then reduces the surrounding pressure. Freeze drying allows the frozen water in the material to sublimate directly from the solid phase to gas.

Selecting sample dryers requires an analysis of performance specifications and application requirements. Some sample dryers use a two-stage process which drops the sample’s temperature twice, removing moisture in two individual trap assemblies. Drying can also be done by using evaporators to apply of dry, heated air. This causes the evaporation of surface water, which is replaced by water internally. The process of extreme drying is called desiccation. Desiccators create a dry environment with electronically controlled storage. Lyophilization technology uses the principle of freeze drying in preserving a perishable material. Operating conditions and sample dryer design are selected according to the drying characteristics of the product and powder specification.

Sample dryers are designed and manufactured to meet most industry specifications. They are used in many applications. Examples include pharmaceuticals, chemical synthesis, food preservation, semiconductor wafers, and obtaining absolute alcohol. Sample dryers should adhere to various food processing standards specified by the International Standards Organization (ISO).

Reactors (or bioreactors or fermenters as they are often called) are at the heart of the fermentation process. They are used for growing cells. Reactors are designed to meet the specific needs of the cells namely: optimal mixing, optimal temperature and optimal pH. In some cases, reactors continuously supply nutrients or precursors to produce a particular product. Bioreactors are often computer controlled to ensure that optimal conditions are met.

Reactors are available in a number of designs including bubble column, airlift, flocculated bed, fluidized bed, packed bed, and stirred tank.  Bubble column reactors are tall reactors, which use air alone to mix the contents. Airlift reactors are similar to bubble column reactors, but differ in that they contain a draft tube. The draft tube is typically an inner tube, which improves circulation and oxygen transfer and equalizes shear forces in the reactor.

Flocculated cell reactors retain cells by allowing them to flocculate. These reactors are used mainly in wastewater treatment. In fluidized bed reactors, cells are "immobilized" small particles, which move with the fluid. The small particles create a large surface area for cells to stick to and enable a high rate of transfer of oxygen and nutrients to the cells. In packed bed reactors, cells are immobilized on large particles. These particles do not move with the liquid. Packed bed reactors are simple to construct and operate but can suffer from blockages and from poor oxygen transfer.

Stirred tank reactors use mechanical stirrers (impellers) to mix the reactor to distribute heat and materials (such as oxygen and substrates).

Reactors use different measurement scales to read the reactions taking place.  From smallest to largest they are laboratory scale, pilot scale, and production or industrial scale. The laboratory scale is used for small-scale experiments of kinetics and yield studies.  They are primarily shake flasks and small bioreactors.  This scale is used to complete a preliminary economic evaluation of experiments. Pilot scale reactors are usually in the range of 100 to 1,000 liters and are utilized in kinetic and mass transfer studies.  They are used for economic evaluations, scale-up studies and downstream processing.  Reactors using the industrial scale are for commercial production applications in the range of 1,000 to 1,000,000 liters.  Their uses include commissioning, troubleshooting, improvement and optimization.

Laboratory shakers and rotators are used to blend or agitate samples within flasks or tubes. These devices consist of a housing containing the motor and control panels, upon which an agitation platform is attached. The platform may have simple grooves for supporting flasks and tubes horizontally as the device moves, or it may have basket style holders that keep the sample holders upright. Unlike mixers, which tend to shred or damage constituent sample materials, laboratory shakers generally leave sample material intact, although mixed. Many laboratory shakers are available with some form of temperature control to incubate, foster or retard reactions, or to maintain stasis.

There are many styles of laboratory shakers available, categorized by their manner of shaking motion. While this list is not all-inclusive, it does cover the most common styles. These are reciprocating, rocking, rolling, rotating, orbital, and wrist action.

In reciprocating motion devices, the shaker moves alternately backward and forward. Similarly, rocking motion devices are capable of a rocking or seesaw motion. Rolling devices slide from side to side with a slight upward, then downward tilt. Rotating shakers turn about an axis and function similarly to centrifuges, although they do not reach the same speeds.

Orbital shakers are the most common variety of laboratory shakers. They create an orbital (horizontal circular) shaking motion sufficient for mixing liquids in flasks and conducive to culturing cells. Most incubator style shakers are of this design.

Wrist or hand motion laboratory shakers duplicate the swirling motion of hand mixing. Instead of cradling flasks or tubes within the agitation platform, these devices have long arms attached to the housing, which swing and swirl when the device is turned on.

Some styles of agitation are better used for specific experimentation or research results. When in doubt, check with the manufacturer as to which of the laboratory shakers would be best for the given application.