Great Exhibition, Vacuum Sugar Apparatus, HF Talbot, 1851

Vacuum evaporation is the process of causing the

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

in a liquid-filled container to be reduced below the

vapor pressure Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phas ...

of the liquid, causing the liquid to evaporate at a lower temperature than normal. Although the process can be applied to any type of liquid at any vapor pressure, it is generally used to describe the boiling of

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

by lowering the container's internal pressure below standard

atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...

and causing the water to boil at room temperature. The vacuum evaporation treatment process consists of reducing the interior pressure of the evaporation chamber below atmospheric pressure. This reduces the boiling point of the liquid to be evaporated, thereby reducing or eliminating the need for heat in both the boiling and condensation processes. There are other advantages, such as the ability to distill liquids with high boiling points and avoiding decomposition of substances that are heat sensitive.

Application

Food

When the process is applied to food and the water is evaporated and removed, the food can be stored for long periods without spoiling. It is also used when boiling a substance at normal temperatures would chemically change the consistency of the product, such as

egg whites Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg. In chickens it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms aro ...

coagulating when attempting to

dehydrate In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...

the

albumen Egg white is the clear liquid (also called the albumen or the glair/glaire) contained within an egg. In chickens it is formed from the layers of secretions of the anterior section of the hen's oviduct during the passage of the egg. It forms aro ...

into a powder. This process was invented by

Henri Nestlé Henri Nestlé () (born Heinrich Nestle; 10 August 1814 – 7 July 1890) was a German-Swiss confectioner and the founder of Nestlé, the world's largest food and beverage company. Early life Heinrich Nestle was born on 10 August 1814 in Frankfu ...

in 1866, of

Nestlé Nestlé S.A. (; ; ) is a Swiss multinational food and drink processing conglomerate corporation headquartered in Vevey, Vaud, Switzerland. It is the largest publicly held food company in the world, measured by revenue and other metrics, since ...

Chocolate fame, although the Shakers were already using a vacuum pan before that (see condensed milk). This process is used industrially to make such food products as

evaporated milk Evaporated milk, known in some countries as "unsweetened condensed milk", is a shelf-stable canned cow’s milk product where about 60% of the water has been removed from fresh milk. It differs from sweetened condensed milk, which contains adde ...

for milk chocolate and

tomato paste Tomato paste is a thick paste made by cooking tomatoes for several hours to reduce the water content, straining out the seeds and skins, and cooking the liquid again to reduce the base to a thick, rich concentrate. It is used to impart an inten ...

for

ketchup Ketchup or catsup is a table condiment with a sweet and tangy flavor. The unmodified term ("ketchup") now typically refers to tomato ketchup, although early recipes used egg whites, mushrooms, oysters, grapes, mussels, or walnuts, among o ...

In the sugar industry vacuum evaporation is used in the crystallization of sucrose solutions. Traditionally this process was performed in batch mode, but nowadays continuous vacuum pans are available.

Wastewater treatment

Vacuum evaporators are used in a wide range of industrial sectors to treat

industrial wastewater Industrial wastewater treatment describes the processes used for Wastewater treatment, treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater (or effluent) may be reuse ...

.Condorchem Envitech
"Vacuum evaporators"
as a technology for industrial water-based liquid waste minimization and treatment. Retrieved 27 January 2009. It represents a clean, safe and very versatile technology with low management costs, which in most cases serves as a zero-discharge treatment system.

Thin film deposition

Vacuum evaporation is also a form of

physical vapor deposition Physical vapor deposition (PVD), sometimes called physical vapor transport (PVT), describes a variety of vacuum deposition methods which can be used to produce thin films and coatings on substrates including metals, ceramics, glass, and polym ...

used in the

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

microelectronics Microelectronics is a subfield of electronics. As the name suggests, microelectronics relates to the study and manufacture (or microfabrication) of very small electronic designs and components. Usually, but not always, this means micrometre-s ...

, and

optic Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...

al industries and in this context is a process of depositing

thin films A thin film is a layer of material ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ...

of material onto surfaces. Such a technique consists of pumping a

vacuum chamber A vacuum chamber is a rigid enclosure from which air and other gases are removed by a vacuum pump. This results in a low-pressure environment within the chamber, commonly referred to as a vacuum. A vacuum environment allows researchers to con ...

to pressures of less than 10⁻⁵

torr The torr (symbol: Torr) is a unit of pressure based on an absolute scale, defined as exactly of a standard atmosphere (). Thus one torr is exactly (≈ ). Historically, one torr was intended to be the same as one " millimeter of merc ...

and heating a material to produce a flux of

vapor In physics, a vapor (American English) or vapour (British English and Canadian English; see spelling differences) is a substance in the gas phase at a temperature lower than its critical temperature,R. H. Petrucci, W. S. Harwood, and F. G. Her ...

to deposit the material onto a surface. The material to be vaporized is typically heated until its

is high enough to produce a flux of several

Angstroms The angstromEntry "angstrom" in the Oxford online dictionary. Retrieved on 2019-03-02 from https://en.oxforddictionaries.com/definition/angstrom.Entry "angstrom" in the Merriam-Webster online dictionary. Retrieved on 2019-03-02 from https://www.m ...

per second by using an

electrical Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described ...

resistive The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels ...

heater or bombardment by a high

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...

beam.

References

{{Reflist Evaporators Food preservation Food science Vacuum Water pollution Thin film deposition

External links