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Measurement and Minimization of Particles in Process Gases
Published in R. P. Donovan, Particle Control for Semiconductor Manufacturing, 2018
Gases used in semiconductor fabrication are generally divided into two broad categories—atmospheric gases and specialty gases (Lattimer, 1967; Ruheman, 1949). The industrial atmospheric gases, i.e., nitrogen, oxygen, and argon (as well as the rare gases, i.e., neon, krypton, and xenon), are produced by air separation. Other industrial gases also found in air, such as carbon dioxide, helium, and hydrogen, are more economically produced by alternative processes. In air separation units (ASU), atmospheric air is drawn through a filter and compressed to the required pressure by one or more compressors. The air temperature is reduced in heat exchangers during and following compression. The air is brought to near liquefaction temperature (−170°C at 5.5 × 105 Pa [5.5 atm]) in reversing heat exchangers, where carbon dioxide and water impurities are removed with waste gas. In some plants, pre-purification units (PPU) consisting of molecular sieve adsorption beds are used to remove these impurities. The cooled and purified air then enters a single or double distillation column where, through the processes of boiling, evaporation, condensation, and expansion, the desired elements are separated from the air. Both liquid and gaseous products are possible, and purities can be increased through process and equipment design modifications.
Polymeric Membranes and Their Applications
Published in Mihir Kumar Purkait, Randeep Singh, Membrane Technology in Separation Science, 2018
Mihir Kumar Purkait, Randeep Singh
The membranes for air separation can be operated in either one of two modes: pressure or vacuum. The pressure mode is the standard mode of operation and thus widely used. In this method, the air is pressurized and given to the membrane module as feed. On the other hand, the permeate side is kept at atmospheric pressure. Thus, pressure difference plays the role of driving force for the separation of air in the desired individual gas. The pressure difference in this method is higher as compared to the vacuum mode. This results in the requirement of less membrane area for the purpose. In the vacuum mode, the feed is pressurized a bit higher than the atmospheric pressure and the permeate side is kept at vacuum. In this mode the retentate vents out at atmospheric pressure from the membrane module. This mode is more energy efficient than the pressure mode. In the case of oxygen enrichment, this mode is suitable due to its energy efficiency and the pressure mode is better for the separation of nitrogen. The two modes can also be used together for their synergistic effects. In this mode the feed will be pressurized, as is the case of pressure mode, and a vacuum will be created on the permeate side, as in the vacuum mode. This will result in increased feed to permeate and feed to retentate pressure ratios. The main applications of air separation are in the production of oxygen, water removed from air to be used in oil and gas drilling, regulated and controlled atmosphere, maritime transportation, gases for laboratory use, inert atmosphere, beverage dispensing, and inflation of tires.
Customers: Electric Service Requirements
Published in J. Lawrence, P.E. Vogt, Electricity Pricing, 2017
The electricity requirements of a particular customer influence purchasing characteristics, at least in part. Energy intensive industries utilize large amounts of electricity and pay significant sums of money for their monthly usage. For example, an air separation process distills common air into its fundamental gasses, including oxygen, nitrogen, and argon, typically in a liquid form. The primary raw input – air – is free. The modern air liquefaction plant is highly automated and requires a minimal amount of labor force. But a large quantity of electricity is required to compress and chill the air so that the individual liquefied gasses can be extracted. The cost of the electricity to produce these air-based products may represent well over 60% of the total cost of the gaseous products. Thus, price is a critical driver in the procurement of electricity.
Membrane separation process modeling for CO2 partial removal in prepurification of air separation units
Published in Chemical Engineering Communications, 2019
Dongyun Wu, Chunhai Yi, Wei Wang, Yixuan Wang, Bolun Yang, Suitao Qi
Currently, the cryogenic air separation process is considered as the most common approach to produce high-purity gases, such as O2 and N2 on an industrial scale (Ham and Kjelstrup, 2010; Tian et al., 2015). It is well known that atmospheric air contains impurities such as water vapor, CO2, and traces of light hydrocarbons (Rege et al., 2001). Since the freezing points of H2O and CO2 are well above the cryogenic temperatures of liquefied air, it is an obvious possibility of occluding the distillation column internals (Tian et al., 2014; Epiepang et al., 2016). Therefore, the impurity content such as moisture, CO2, and hydrocarbons in feed air should be reduced to tolerable levels before entering the air separation units (ASUs). This operating process is commonly termed as “air prepurification”. The rapid growth in demand for industrial gas in steel and chemical industries results in the capacity expansion of the cryogenic ASUs, which may adversely influence the performance of the prepurification facility, like adsorber (Tian et al., 2015).
Experimental and numerical investigation of the aircraft fuel tank inerting system
Published in Australian Journal of Mechanical Engineering, 2023
As depicted in Figure 1, the bleed air undergoes temperature and pressure regulation as well as filtration to create air source conditions that meet the requirements of the membrane separation device. Within the air separation device, which incorporates the hollow fibre membrane, the air is separated into NEA and oxygen-enriched air (OEA) due to the different permeabilities of nitrogen and oxygen through the hollow fibre membrane. The OEA is discharged from the aircraft, while the NEA is transported to the aircraft’s fuel tank via the distribution pipeline.