sign in sign up
<<
Home , Industrial gas

The Chemical 2. Industrial

1 Industrial gases

◦ Industrial gases are the gaseous materials that are manufactured for use in industry. The principal gases provided are , , , , , and , although many other gases and are also available in cylinders. ◦ The industry producing these gases is also known as industrial gas, which is seen as also encompassing the supply of equipment and to produce and use the gases. ◦ Their production is a part of the wider (where industrial gases are often seen as "specialty chemicals"). 2 ◦ Industrial gases are used in a wide range of industries, which include oil and gas, , chemicals, power, , , , environmental protection, , pharmaceuticals, , food, water, , , electronics and aerospace. ◦ Industrial gas is sold to other industrial enterprises; typically comprising large orders to corporate industrial clients, covering a size range from building a process facility or pipeline down to cylinder gas supply.

3 Early history of gases

◦ The first gas from the natural environment used by humans was almost certainly air when it was discovered that blowing on or fanning a fire made it burn brighter. Humans also used the warm gases from a fire to smoke foods and from boiling water to cook foods. ◦ Carbon dioxide has been known from ancient times as the byproduct of fermentation, particularly for beverages, which was first documented dating from 7000–6600 B.C. in Jiahu, China. ◦ was used by the Chinese in about 500 B.C. when they discovered the potential to transport gas seeping from the ground in crude pipelines of bamboo to where it was used to boil sea water. ◦ was used by the Romans in winemaking as it had been discovered that burning made of sulfur inside empty wine vessels would keep them fresh and prevent them gaining a vinegar smell. 4 ◦ The history of tells us that a number of gases were identified and either discovered or first made in relatively pure form during the of the 18th and 19th centuries by notable in their .

◦ The timeline of attributed discovery for various gases are:

carbon dioxide (1754) (1776) hydrogen (1766) (1777) nitrogen (1772) (1800) (1772) (1810) oxygen (1773) acetylene (1836) (1774) (1886), (1774) , and xenon (1898)

5 Oxygen production

◦ Oxygen finds broad application in various technological processes and in almost all industry branches. ◦ The primary oxygen application is associated with its capability of sustaining burning process, and the powerful oxidant properties. ◦ Due to that, oxygen has become widely used in the processing, , cutting and brazing processes. ◦ In the chemical and industries, as well as in the oil and gas sector oxygen is used in commercial volumes as an oxidizer in chemical reactions.

6 Oxygen plants are industrial systems designed to generate oxygen.

They typically use air as a feedstock and separate it from other components of air using swing adsorption or membrane separation techniques.

Such plants are distinct from cryogenic separation plants which separate and capture all the components of air.

7 Adsorption technology https://www.youtube.com/watch?v=SrtL6sEHGmI

◦ Gas separation by adsorption systems is based on differential rates of adsorption of the components of a gas into a adsorbent. ◦ The current methods of gaseous oxygen production from air by the use of adsorption technology produce a high fraction of oxygen as their output. The mechanism of operation of a modern oxygen adsorption plant is based on the variation of uptake of a particular gas component by the adsorbent as the temperature and partial pressure of the gas is changed. ◦ The gas adsorption and adsorbent regeneration processes may therefore be regulated by varying of the pressure and temperature parameters. 8 Pressure swing adsorption (PSA)

◦ Pressure swing adsorption (PSA) is a technology used to separate some gas species from a mixture of gases under pressure according to the species' molecular characteristics and affinity for an adsorbent material. ◦ It operates at near-ambient temperatures and differs significantly from cryogenic techniques of gas separation. ◦ Specific adsorbent materials (e.g., zeolites, activated carbon, molecular sieves, etc.) are used as a trap, preferentially adsorbing the target gas species at high pressure. ◦ The process then swings to low pressure to desorb the adsorbed material.

9 Process

◦ Pressure swing adsorption processes utilize the fact that under high pressure, gases tend to be attracted to solid surfaces, or "adsorbed". The higher the pressure, the more gas is adsorbed. When the pressure is reduced, the gas is released, or desorbed. ◦ PSA processes can be used to separate gases in a mixture because different gases tend to be attracted to different solid surfaces more or less strongly. If a gas mixture such as air is passed under pressure through a vessel containing an adsorbent bed of zeolite that attracts nitrogen more strongly than oxygen, part or all of the nitrogen will stay in the bed, and the gas exiting the vessel will be richer in oxygen than the mixture entering. ◦ When the bed reaches the end of its capacity to adsorb nitrogen, it can be regenerated by reducing the pressure, thus releasing the adsorbed nitrogen. It is then ready for another cycle of producing oxygen-enriched air.

https://upload.wikimedia.org/wikipedia/commons/7/76/Pressure_swing_adsorption_principle.svg 10 Pressure swing adsorption

◦ Today, there exist three methods of arranging the adsorption-based process with the use of swing : pressure (PSA), (VSA) and mixed (VPSA) ones. ◦ In the pressure swing adsorption flow processes, oxygen is recovered under above- atmospheric pressure and regeneration is achieved under atmospheric pressure. ◦ In vacuum swing adsorption flow processes, oxygen is recovered under atmospheric pressure, and regeneration is achieved under negative pressure. ◦ The mixed systems operation combines pressure variations from positive to negative.

11 One of the biggest oxygen plants in the world guarantees critical oxygen supply for Metsä Group’s bioproduct mill (Vacuum Pressure Swing Adsorption technology - VPSA) https://linde-stories.com/one-of-the-biggest-oxygen-plants-in-the-world-guarantees-critical-oxygen-supply-for-metsa-groups-bioproduct-mill/

https://www.youtube.com/watch?v=rbIR7HWPrBo&f12 eature=emb_logo Membrane technology

◦ The basis of gas media separation with the use of membrane systems is the difference in velocity with which various gas mixture components permeate membrane substance. The driving force behind the gas is the difference in partial on different membrane sides. ◦ Membrane consists of a porous polymer fiber with the gas separation layer applied to its external surface. ◦ Structurally, a hollow fiber membrane is configured as a cylindrical cartridge representing a spool with specifically reeled polymer fiber.

13 ◦ Due to the membrane material high permeability for oxygen in contrast to nitrogen, the design of membrane oxygen complexes requires a special approach. ◦ Basically, there are two membrane-based oxygen production technologies: and vacuum ones. ◦ In the case of compressor technology, air is supplied into the fiber space under excess pressure, oxygen exits the membrane under slight excess pressure, and where necessary, is pressurized by booster compressor to the required pressure level. ◦ By the use of vacuum technology, a vacuum pump is used for the achievement of partial pressures difference.

14 Cryogenic Air Separation Unit (ASU)

◦ Cryogenic distillation separates oxygen from air by liquefying air at very low temperatures (-300°F). ◦ Ambient air is compressed in multiple stages with inter-stage cooling then further cooled with chilled water. ◦ Residual water , carbon dioxide, and atmospheric contaminants are removed in adsorbers. ◦ Cooling to cryogenic temperatures is achieved by heat exchange with product gases as well as after-coolers and expanders. ◦ The air then enters the "cold box," which contains a distillation column with many stages, and an argon column for additional oxygen purification.

15 Cryogenic distillation process

◦ Pure gases can be separated from air by first cooling it until it liquefies, then selectively distilling the components at their various boiling temperatures. The process can produce high purity gases but is energy- intensive. This process was pioneered by in the early 20th century and is still used today to produce high purity gases. He developed it in the year 1895; the process remained purely academic for seven years before it was used in industrial applications for the first time (1902) ◦ The cryogenic separation process requires a very tight integration of heat exchangers and separation columns to obtain a good efficiency and all the energy for is provided by the compression of the air at the inlet of the unit. ◦ To achieve the low distillation temperatures, an air separation unit requires a refrigeration cycle that operates by means of the Joule–Thomson effect, and the cold equipment has to be kept within an insulated enclosure (commonly called a "cold box"). The cooling of the gases requires a large amount of energy to make this refrigeration cycle work and is delivered by an air compressor. Modern ASUs use expansion turbines for cooling; the output of the expander helps drive the air compressor, for improved efficiency. https://www.youtube.com/watch?v=M7h59Tg9DS4

16 ◦ The process consists of the following main steps:

1. Before compression the air is pre-filtered of dust. 2. Air is compressed where the final delivery pressure is determined by recoveries and the fluid state (gas or ) of the products. Typical pressures range between 5 and 10 bar gauge. The air stream may also be compressed to different pressures to enhance the efficiency of the ASU. During compression water is condensed out in inter- stage coolers. 3. The process air is generally passed through a molecular sieve bed, which removes any remaining water vapour, as well as carbon dioxide, which would freeze and plug the cryogenic equipment. Molecular sieves are often designed to remove any gaseous from the air, since these can be a problem in the subsequent air distillation that could lead to explosions. The molecular sieves bed must be regenerated. This is done by installing multiple units operating in alternating mode and using the dry co-produced waste gas to desorb the water.

17 4. Process air is passed through an integrated heat exchanger (usually a plate fin heat exchanger) and cooled against product (and waste) cryogenic streams. Part of the air liquefies to form a liquid that is enriched in oxygen. The remaining gas is richer in nitrogen and is distilled to almost pure nitrogen (typically < 1ppm) in a high pressure (HP) distillation column. The condenser of this column requires refrigeration which is obtained from expanding the more oxygen rich stream further across a valve or through an Expander, (a reverse compressor). 5. Alternatively, the condenser may be cooled by interchanging heat with a reboiler in a low pressure (LP) distillation column (operating at 1.2-1.3 bar abs.) when the ASU is producing pure oxygen. To minimize the compression cost the combined condenser/reboiler of the HP/LP columns must operate with a temperature difference of only 1-2 K, requiring plate fin brazed aluminium heat exchangers. Typical oxygen purities range in from 97.5% to 99.5% and influences the maximum recovery of oxygen. The refrigeration required for producing liquid products is obtained using the Joule–Thomson effect in an expander which feeds directly to the low-pressure column. Hence, a certain part of the air is not to be separated and must leave the low-pressure column as a waste stream from its upper section.

18 ◦ Because the boiling point of argon (87.3 K at standard conditions) lies between that of oxygen (90.2 K) and nitrogen (77.4 K), argon builds up in the lower section of the low-pressure column. When argon is produced, a vapor side draw is taken from the low-pressure column where the argon concentration is highest. It is sent to another column rectifying the argon to the desired purity from which liquid is returned to the same location in the LP column. Use of modern structured packings which have very low-pressure drops enable argon with less than 1 ppm impurities. Though argon is present in less to 1% of the incoming, the air argon column requires a significant amount of energy due to the high reflux ratio required (about 30) in the argon column. Cooling of the argon column can be supplied from cold expanded rich liquid or by . ◦ Finally, the products produced in gas form are warmed against the incoming air to ambient temperatures. This requires a carefully crafted heat integration that must allow for robustness against disturbances (due to switch over of the molecular sieve beds). It may also require additional external refrigeration during start-up. https://www.youtube.com/watch?v=pdU5Uj1Tco8

19 20 Nitrogen Production

◦ In many processes, the use of large volumes of nitrogen is crucial to success. From food and beverage manufacture, winery, and oil and gas processes such as nitrogen blanketing and gas purging, large volumes of nitrogen are needed to facilitate these processes. ◦ The manufacture of nitrogen gas has countless applications, especially in the oil and gas industry. Some of the key uses of industrial nitrogen are outlined below. ◦ Nitrogen blanketing ◦ Nitrogen purging ◦ Nitrogen injection/ Gas lifting ◦ Gas-assisted injection molding ◦ Nitrogen Sparging for Wine

21 3 Common Types of Nitrogen Gas Production 1. Pressure Swing Adsorption (PSA) Nitrogen Production This method of production of nitrogen gas relies on the ability of adsorbent material to separate a gaseous mixture into its components. Pressure swing adsorption is a two-stage nitrogen making process that involves adsorption and desorption ongoing simultaneously in two generation towers. ◦ Adsorption This first stage requires the use of an adsorptive tower filled with a molecular carbon sieve material, which selectively retains oxygen while allowing nitrogen to pass into a collecting tank. This process will continue until the adsorptive tower reaches its maximum saturation point.

◦ Desorption This is the second step in a PSA nitrogen generation process and is essentially a reversal of the adsorption process. Once the saturation point for an adsorptive tower is reached, its function is changed, and oxygen is released from it to regenerate the sieve material to enable another cycle of adsorption. 22 23 ◦ 2. Membrane Nitrogen Production ◦ Membrane nitrogen generation uses a semi-permeable membrane to achieve the separation of a stream of air into its component gases using their varied speeds of travel. The hollow fiber membrane module is designed to facilitate faster rates of permeation by providing a larger surface area for the gas stream. ◦ https://www.airproducts.com/supply- modes/prism-membranes ◦ A typical membrane nitrogen generator has these components:

◦ Feed filter coalescers ◦ Immersion heaters ◦ Activated carbon filters ◦ Particulate filters

24 ◦ 3. Fractional Distillation Nitrogen Production ◦ Fractional distillation is a highly effective method of generating nitrogen for industrial use. ◦ The process involves the supercooling of air to its liquefaction point and then distilling its component gases at their various boiling points. ◦ This process will yield nitrogen with a high purity but is generally more costly than PSA or Membrane production.

25 Nitrogen users can choose from a range of options for on-site nitrogen production to meet a variety of needs, including cryogenic air separation (top left), pressure swing adsorption (top right), and membrane systems (bottom). 26

The many paths to hydrogen is the main method used to produce hydrogen on an industrial scale today. In an initial step, feedstocks such as natural gas, LPG or naphtha are combined with steam to produce synthesis gas with the aid of a heterogeneous catalyst. This mixture of carbon monoxide and hydrogen is then further processed. Since fossil are used in this production method, the end product is called gray hydrogen.

Gray hydrogen can also be produced through the of refinery residues. This residue material is heated to a very high temperature with oxygen and steam to produce a raw synthesis gas. If the carbon dioxide (CO2) contained in this gas is removed in a downstream carbon capture process, the resulting hydrogen is called blue.

Green hydrogen (H2) is obtained either by steam reforming, if bio-based feedstock is available, or by splitting water by . The electricity needed for this electrolysis process is generated exclusively from renewable sources.

27 Natural Gas Reforming https://www.youtube.com/watch?v=xAjHJ49VOUM ◦ Natural gas reforming is an advanced and mature production process that builds upon the existing natural gas pipeline delivery infrastructure. Today, 95% of the hydrogen produced in the United States is made by natural gas reforming in large central plants. This is an important technology pathway for near-term hydrogen production.

◦ How Does It Work?

◦ Natural gas contains methane (CH4) that can be used to produce hydrogen with thermal processes, such as ◦ steam-methane reformation, and ◦ partial oxidation.

28 STEAM-METHANE REFORMING HTTPS://WWW.YOUTUBE.COM/WATCH?V=APYAQSP8HXE

◦ Most hydrogen produced today in the United States is made via steam-methane reforming, a mature production process in which high-temperature steam (700°C–1,000°C) is used to produce hydrogen from a methane source, such as natural gas. In steam- methane reforming, methane reacts with steam under 3–25 bar pressure (1 bar = 14.5 psi) in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relatively small amount of carbon dioxide. Steam reforming is endothermic—that is, heat must be supplied to the process for the reaction to proceed.

◦ Subsequently, in what is called the "water-gas shift reaction," the carbon monoxide and steam are reacted using a catalyst to produce carbon dioxide and more hydrogen. In a final process step called "pressure-swing adsorption," carbon dioxide and other impurities are removed from the gas stream, leaving essentially pure hydrogen. Steam reforming can also be used to produce hydrogen from other fuels, such as ethanol, , or even gasoline.

◦ Steam-methane reforming reaction

CH4 + H2O (+ heat) → CO + 3H2 ◦ Water-gas shift reaction

CO + H2O → CO2 + H2 (+ small amount of heat)

29 PARTIAL OXIDATION ◦ In partial oxidation, the methane and other hydrocarbons in natural gas react with a limited amount of oxygen (typically from air) that is not enough to completely oxidize the hydrocarbons to carbon dioxide and water. With less than the stoichiometric amount of oxygen available, the reaction products contain primarily hydrogen and carbon monoxide (and nitrogen, if the reaction is carried out with air rather than pure oxygen), and a relatively small amount of carbon dioxide and other compounds. Subsequently, in a water-gas shift reaction, the carbon monoxide reacts with water to form carbon dioxide and more hydrogen. ◦ Partial oxidation is an exothermic process—it gives off heat. The process is, typically, much faster than steam reforming and requires a smaller reactor vessel. As can be seen in chemical reactions of partial oxidation, this process initially produces less hydrogen per unit of the input than is obtained by steam reforming of the same fuel. ◦ Partial oxidation of methane reaction

CH4 + ½O2 → CO + 2H2 (+ heat) ◦ Water-gas shift reaction

CO + H2O → CO2 + H2 (+ small amount of heat) 30 Why Is This Pathway Being Considered?

◦ Reforming low-cost natural gas can provide hydrogen today for fuel cell electric vehicles (FCEVs) as well as other applications. Over the long term, hydrogen production from natural gas will be augmented with production from renewable, nuclear, coal (with carbon capture and storage), and other low-carbon, domestic energy resources. ◦ use and emissions are lower than for gasoline-powered internal combustion engine vehicles. The only product from an FCEV tailpipe is water vapor but even with the upstream process of producing hydrogen from natural gas as well as delivering and storing it for use in FCEVs, the total greenhouse gas emissions are cut in half and petroleum is reduced over 90% compared to today's gasoline vehicles. 31