 |
Industrial agitators are machines used to stir or mix fluids in industries that process products in the chemical, food, pharmaceutical and cosmetic industries. [1] Their uses include:
Several different kind of industrial agitators exist:
The choice of the agitator depends on the phase that needs to be mixed (one or several phases): liquids only, liquid and solid, liquid and gas or liquid with solids and gas. Depending on the type of phase and the viscosity of the bulk, the agitator may be called a mixer, kneader, dough mixer, amongst others. Agitators used in liquids can be placed on the top of the tank in a vertical position, horizontally on the side of the tank, or less commonly, on the bottom of the tank.
The agitation is achieved by movement of the heterogeneous mass (liquid-solid phase). In mechanical agitators, this the result of the rotation of an impeller. The bulk can be composed of different substances and the aim of the operation is to blend it or to improve the efficiency of a reaction by a better contact between reactive product. Agitation may also be used to increase heat transfer or to maintain particles in suspension.
The agitation of liquid is made by one or several agitation impellers. Depending on its shape, the impeller can generate:
These two phenomena provide energy consumption.
Propellers (marine or hydrofoil) give an inlet and outlet which are on axial direction, preferably downward, they are characterized by a nice pumping flow, low energy consumption and low shear magnitude as well as low turbulence. An impeller is a rotor that produces a sucking force, and is part of a pump.
Turbines (flat blades or pitched blades) which inlet flow is axial and outlet flow is radial will provide shearing, turbulence and need approximately 20 time more energy than propellers, for the same diameter and same rotation speed.
An agitator is composed of a drive device ( motor, gear reducer, belts…), a guiding system of the shaft (lantern fitted with bearings), a shaft and impellers .
If the operating conditions are under high pressure or high temperature, the agitator must be equipped with a sealing system to keep tightened the inside of the tank when the shaft is crossing it.
If the shaft is long (> 10m), it can be guided by a bearing located in the bottom of the tank (bottom bearing).
Cavitation is a phenomenon in which the static pressure of a liquid reduces to below the liquid's vapour pressure, leading to the formation of small vapor-filled cavities in the liquid. When subjected to higher pressure, these cavities, called "bubbles" or "voids", collapse and can generate shock waves that may damage machinery. These shock waves are strong when they are very close to the imploded bubble, but rapidly weaken as they propagate away from the implosion. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal, causing a type of wear also called "cavitation". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior: inertial cavitation and non-inertial cavitation.
A pump is a device that moves fluids, or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy.
The Tesla turbine is a bladeless centripetal flow turbine patented by Nikola Tesla in 1913. It was his 100th patent.
A turbopump is a propellant pump with two main components: a rotodynamic pump and a driving gas turbine, usually both mounted on the same shaft, or sometimes geared together. They were initially developed in Germany in the early 1940s. The purpose of a turbopump is to produce a high-pressure fluid for feeding a combustion chamber or other use.
Flow measurement is the quantification of bulk fluid movement. Flow can be measured using devices called flowmeters in various ways. The common types of flowmeters with industrial applications are listed below:
A submersible pump is a device which has a hermetically sealed motor close-coupled to the pump body. The whole assembly is submerged in the fluid to be pumped. The main advantage of this type of pump is that it prevents pump cavitation, a problem associated with a high elevation difference between the pump and the fluid surface. Submersible pumps push fluid to the surface, rather than jet pumps, which create a vacuum and rely upon atmospheric pressure. Submersibles use pressurized fluid from the surface to drive a hydraulic motor downhole, rather than an electric motor, and are used in heavy oil applications with heated water as the motive fluid.
Centrifugal compressors, sometimes called impeller compressors or radial compressors, are a sub-class of dynamic axisymmetric work-absorbing turbomachinery.
In industrial process engineering, mixing is a unit operation that involves manipulation of a heterogeneous physical system with the intent to make it more homogeneous. Familiar examples include pumping of the water in a swimming pool to homogenize the water temperature, and the stirring of pancake batter to eliminate lumps (deagglomeration).
A chemical reactor is an enclosed volume in which a chemical reaction takes place. In chemical engineering, it is generally understood to be a process vessel used to carry out a chemical reaction, which is one of the classic unit operations in chemical process analysis. The design of a chemical reactor deals with multiple aspects of chemical engineering. Chemical engineers design reactors to maximize net present value for the given reaction. Designers ensure that the reaction proceeds with the highest efficiency towards the desired output product, producing the highest yield of product while requiring the least amount of money to purchase and operate. Normal operating expenses include energy input, energy removal, raw material costs, labor, etc. Energy changes can come in the form of heating or cooling, pumping to increase pressure, frictional pressure loss or agitation.
An impeller or impellor is a driven rotor used to increase the pressure and flow of a fluid. It is the opposite of a turbine, which extracts energy from, and reduces the pressure of, a flowing fluid.
Turbomachinery, in mechanical engineering, describes machines that transfer energy between a rotor and a fluid, including both turbines and compressors. While a turbine transfers energy from a fluid to a rotor, a compressor transfers energy from a rotor to a fluid.
Centrifugal pumps are used to transport fluids by the conversion of rotational kinetic energy to the hydrodynamic energy of the fluid flow. The rotational energy typically comes from an engine or electric motor. They are a sub-class of dynamic axisymmetric work-absorbing turbomachinery. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber (casing), from which it exits.
A fluidized bed is a physical phenomenon that occurs when a solid particulate substance is under the right conditions so that it behaves like a fluid. The usual way to achieve a fluidized bed is to pump pressurized fluid into the particles. The resulting medium then has many properties and characteristics of normal fluids, such as the ability to free-flow under gravity, or to be pumped using fluid technologies.
An axial-flow pump, or AFP, is a common type of pump that essentially consists of a propeller in a pipe. The propeller can be driven directly by a sealed motor in the pipe or by electric motor or petrol/diesel engines mounted to the pipe from the outside or by a right-angle drive shaft that pierces the pipe.
An agitator is a device or mechanism to put something into motion by shaking or stirring. There are several types of agitation machines, including washing machine agitators and magnetic agitators. Agitators can come in many sizes and varieties, depending on the application.
A fluid coupling or hydraulic coupling is a hydrodynamic or 'hydrokinetic' device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and controlled start-up without shock loading of the power transmission system is essential.
A batch reactor is a chemical reactor in which a non-continuous reaction is conducted, i.e., one where the reactants, products and solvent do not flow in or out of the vessel during the reaction until the target reaction conversion is achieved. By extension, the expression is somehow inappropriately used for other batch fluid processing operations that do not involve a chemical reaction, such as solids dissolution, product mixing, batch distillation, crystallization, and liquid/liquid extraction. In such cases, however, they may not be referred to as reactors but rather with a term specific to the function they perform.
A high-shear mixer disperses, or transports, one phase or ingredient into a main continuous phase (liquid), with which it would normally be immiscible. A rotor or impeller, together with a stationary component known as a stator, or an array of rotors and stators, is used either in a tank containing the solution to be mixed, or in a pipe through which the solution passes, to create shear. A high-shear mixer can be used to create emulsions, suspensions, lyosols, and granular products. It is used in the adhesives, chemical, cosmetic, food, pharmaceutical, and plastics industries for emulsification, homogenization, particle size reduction, and dispersion.
A centrifugal fan is a mechanical device for moving air or other gases in a direction at an angle to the incoming fluid. Centrifugal fans often contain a ducted housing to direct outgoing air in a specific direction or across a heat sink; such a fan is also called a blower, blower fan, or squirrel-cage fan. Tiny ones used in computers are sometimes called biscuit blowers. These fans move air from the rotating inlet of the fan to an outlet. They are typically used in ducted applications to either draw air through ductwork/heat exchanger, or push air through similar impellers. Compared to standard axial fans, they can provide similar air movement from a smaller fan package, and overcome higher resistance in air streams.
A rotodynamic pump is a kinetic machine in which energy is continuously imparted to the pumped fluid by means of a rotating impeller, propeller, or rotor, in contrast to a positive displacement pump in which a fluid is moved by trapping a fixed amount of fluid and forcing the trapped volume into the pump's discharge. Examples of rotodynamic pumps include adding kinetic energy to a fluid such as by using a centrifugal pump to increase fluid velocity or pressure.