A cryogenic gas plant is an industrial facility that creates

molecular oxygen There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O3). Others are: * ...

, molecular nitrogen,

argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...

krypton Krypton (from grc, κρυπτός, translit=kryptos 'the hidden one') is a chemical element with the symbol Kr and atomic number 36. It is a colorless, odorless, tasteless noble gas that occurs in trace amounts in the atmosphere and is often ...

Helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

and

Xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

at relatively high purity. As air is made up of nitrogen, the most common gas in the atmosphere, at 78%, with Oxygen at 19%, and Argon at 1%, with trace gasses making up the rest, Cryogenic gas plants separate air inside a distillation column at cryogenic temperatures (about 100 K/-173 °C) to produce high purity gasses such as Argon, Nitrogen, Oxygen, and many more with 1 ppm or less impurities. The process is based on the general theory of the Hampson-Linde cycle of air separation, which was invented by Dr. Carl von Linde in 1895. Atmosphere gas proportions

Purpose

The main purpose of a cryogenic nitrogen plant is to provide a customer with high purity gaseous nitrogen (GAN), liquid nitrogen (LIN), Liquid argon (LAR) and high purity argon PLAR at high purities, along with extracting trace gasses like kryton, xenon and helium. High purity liquid material such as oxygen or nitrogen produced by cryogenic plants is stored in a local tank and used as a strategic reserve. This liquid can be vaporised to cover peaks in demand or for use when the plant is offline. Argon, Xenon and Helium are usually sold to customers in high pressure tank cars or trucks directly due to the smaller volumes. Typical cryogenic nitrogen plants range from 200ft³/hour to very large range plants with a daily capacity of 63 tonnes of nitrogen a day (as the Cantarell Field plant in Mexico). The cryogenic air separation achieves high purity oxygen of more than 99.5%. The resulting high purity product can be stored as a liquid and/or filled into cylinders. These cylinders can even be distributed to customer in the medical sector,

welding Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as bra ...

or mixed with other gases and used as breathing gas for

diving Diving most often refers to: * Diving (sport), the sport of jumping into deep water * Underwater diving, human activity underwater for recreational or occupational purposes Diving or Dive may also refer to: Sports * Dive (American football), a ...

. The plant also produces nitrogen which is used for

Ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

production for the

fertilizer A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

industry, Float glass manufacturing,

Petrochemical Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable so ...

usage, Purge gas,

Amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen Hydrogen is the chemical element wi ...

gas treatment, Bearing seal gas, and Polyester manufacturing. The resulting Argon gas can be used in

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. ...

manufacturing and Photovoltaic manufacturing.

Plant modules

A cryogenic plant is composed of the following elements:

Warm end (W/E) container

* Compressor * Air receiver *Chiller (

Heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct conta ...

) *Pre-

filter Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

* Air purification unit (APU)

Coldbox

*Main

heat exchanger A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct conta ...

Boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, centr ...

Distillation column A fractionating column or fractional column is an essential item used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on the differences in volatilities. Fractionating columns are used in ...

*Expansion brake

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...

Storage

* Liquid oxygen tank *Vapouriser *Filling station

How the plant works

A-cryogenic-air-separation-plant-that-produces-argon-in-addition-to-oxygen-and-nitrogen

Warm end process

Atmospheric air is roughly filtered and pressurised by a compressor, which provides the product pressure to deliver to the customer. The amount of air sucked in depends on the customer’s oxygen demand. The air receiver collects condensate and minimises pressure drop. The dry and compressed air leaves the air to refrigerant

with about 10°C. To clean the process air further, there are different stages of filtration. First of all, more condensate is removed, then a coalescing filter acts as a gravity filter and finally an adsorber filled with activated carbon removes some

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

s. The last

unit process A ''unit process'' is one or more grouped operations in a manufacturing system that can be defined and separated from others. In life-cycle assessment Life cycle assessment or LCA (also known as life cycle analysis) is a methodology for ass ...

in the warm end container is the thermal swing adsorber (TSA). The Air purification unit cleans the compressed process air by removing any residual water vapour,

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

and

hydrocarbons In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or e ...

. It comprises two vessels, valves and exhaust to allow the changeover of vessels. While one of the TSA beds is on stream the second one is regenerated by the waste gas flow, which is vented through a silencer into the ambient environment.

Coldbox process

The process air enters the main

in the coldbox where it is cooled in counter flow with the waste gas stream. After leaving the main heat exchanger the process air has a temperature of about –112°C and is partly liquefied. The complete liquefaction is achieved through evaporation of cooled liquid oxygen in the

boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, centr ...

. After passing a purity control valve, process air enters on top of the

distillation column A fractionating column or fractional column is an essential item used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on the differences in volatilities. Fractionating columns are used in ...

and flows down through the packing material. The stream of evaporated oxygen vapour in the shell of the boiler vents back into the distillation column. It rises through the column packing material and encounters the descending stream of liquid process air. The liquid air descending down the column loses

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

. It becomes richer in oxygen and collects at the base of the column as pure

liquid oxygen Liquid oxygen—abbreviated LOx, LOX or Lox in the aerospace, submarine and gas industries—is the liquid form of molecular oxygen. It was used as the oxidizer in the first liquid-fueled rocket invented in 1926 by Robert H. Goddard, an app ...

. It flows out into the boiler to the cold box liquid product valve. An on-line oxygen analyzer controls the opening of the liquid product

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fitting ...

to transfer pure low-pressure liquid oxygen into the storage tank. The rising oxygen vapour becomes rich in

and

. It leaves the column and exits the cold box at ambient temperature through the main heat exchanger as a waste gas. This waste gas provides purge gas to regenerate the TSA unit and to the cool the refrigeration

. Turbines located at the base of the cold box provide refrigeration for the process. A stream of high-pressure gas from the main heat exchangers is cooled and expanded to low pressure in the turbine. This cold air returns to the waste stream of the

to inject refrigeration. Energy removed by the turbine re-appears as heat in the turbine’s closed-cycle air-brake circuit. This heat is removed in an air-to-air

cooler A cooler, portable ice chest, ice box, cool box, chilly bin (in New Zealand), or esky ( Australia) is an insulated box used to keep food or drink cool. Ice cubes are most commonly placed in it to help the contents inside stay cool. Ice packs a ...

by waste gas from the cold box.

Storage and vaporising process

Liquid from the tank is compressed to high pressure in a cryogenic liquid pump. It is then vaporised in an ambient air

evaporator An evaporator is a device used to turn the liquid form of a chemical substance, such as water, into a vapor. Uses Air conditioning and refrigeration Some air conditioners and refrigerators use a compressed liquid with a low boiling point, su ...

to produce gaseous oxygen or nitrogen. The high-pressure gas then can pass into cylinders via the gas manifold or fed into a customer's product pipeline.

Applications

Applications for High Purity Oxygen

* Furnace enrichment *Medical gases * Metal production *

Welding Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as bra ...

Applications for high purity nitrogen production

production for the

industry * Float glass manufacturing *

*Purge gas *Blanketing/Inerting gas for tanks and reactor vessels *

gas treatment * Bearing seal gas * Polyester manufacturing

Applications for High Purity Argon

manufacturing * Photovoltaic manufacturing

Applications for Xenon

* Space Travel * Medical Scan

References

{{DEFAULTSORT:Cryogenic Oxygen Plant Chemical processes Industrial processes Chemical plants Gas technologies Industrial gases Cryogenics