Introduction
The pressure swing adsorption principle and technology will be used in an experiment to separate the two gases in the lab. The technology is a technique used to separate two or more gases from a collection of various gases using pressure and the gases molecular attributes as well as an affinity for an absorbent material (Alonso-Vicario et al., 2010). The experiment will utilize the principle of pressure swing adsorption to separate active carbon and oxygen using hydrogen and nitrogen as catalysts. Pressure swing adsorption using two main factors in the separation of gases under pressure: the molecular attributes of the gases and the gases’ affinity for an absorbent material.
Pressure swing adsorption technique operates at a temperature that is close to ambient temperature. It employs the use of absorptive materials, such as activated carbon, zeolites and molecular sieves as a trap. The absorbent material preferentially adsorbs the required gas type at high pressure. After the target gas has been absorbed by the absorptive material, the process sways to low pressure and decibels the adsorbed gas (Ebner et al., 2011). It is imperative to note that the processes used in pressure swing adsorption heavily rely on the properties of gases at high pressure. That is to say that; gases at high pressure are always attracted to solid surfaces. High pressure makes gases be highly adsorbed to surfaces, thus allowing for their separation based on different molecular characteristics.
The aim and objective of the experiment are to highlight the students on the operation and processes involved in the separation of gases using pressure swing adsorption. Additionally, the experiment is aimed at using different gas's characteristics such as pressure to separate a mixture of gases. Finally, the students will learn the contribution of gases’ affinity with the absorbent material in the separation process using a pressure swing adsorption technique. The experiment will also expose the students to the working principle of pressure swing adsorption technology in the separation of gases.
Theoretical Background
Pressure swing adsorption is a highly popular technology and technique used in the separation of the gas mixture, hydrogen purification as well as gas drying. The advancements in the technology have seen its application in various areas such as the purification of methane from biogas and natural gas. The application of pressure swing adsorption has a huge potential of various applications and utilization (Alonso-Vicario et al., 2010).While the adsorbent material used in pressure swing adsorbent is tremendously imperative in defining its properties, the process engineering used in the technique has the potential to significantly improve the performance of the pressure swing adsorption.
Adsorption is the process of attraction that a molecule in a fluid phase exhibits when it is close to the surface of a solid material called adsorbent. Absorbents are made up porous solids which have large surface area per unit mass. The separation of gases at high pressure through the use of adsorbents is primarily based on the fact that various gases have different interactions with the surfaces of different adsorbents (Dantas et al., 2011). In most cases, an equilibrium state is usually attained after a certain time when the absorbent material is placed in contact with a fluid phase. The equilibrium is significant is determining the thermodynamic limit of the adsorbent material loading for a specific fluid phase temperature, composition and pressure.
Adsorbent
The characteristic of the pressure swing adsorption is highly determined by the type of adsorbent employed in the separation process (Liu et al., 2011). Adsorbent materials have the ability to differentiate between different gases. Also, adsorbent materials are used due to their large surface area to unit mass ratio. The adsorbent used in an adsorption process is usually shaped into spherical pellets for maximum absorption of the target gas. In other cases, the adsorbent is shaped in the form of monolithic honeycomb configurations which leads to a reduced pressure drop of the separation system.
The feed gas stream is placed into contact with the adsorbent that is usually arranged in fixed beds. The gas, which is not strongly attracted to the absorbent breaks through the columns at higher speed than the gas which is strongly attracted to the absorbent. Separation of the gases is attained by stopping the feed stream before the adsorbed gas break through the column. The adsorbent is regenerated through describing the adsorbed gas (Dantas et al., 2011). The adsorbed gas is placed under low pressure in a different vessel so as to release the gas from the adsorbent material. Regeneration of the adsorbent and separation is attained by reducing the total pressure of the separation system (Ebner et al., 2011). The total pressure of the separation system sways between high pressure in the feed stream and low pressure in the regeneration.
Process
It is important to note the fact that pressure swing adsorption highly relies on the characteristics of gases at high pressure. It is a well-known fact that gases tend to highly adapt under high pressure. In other words, gases are highly attracted to solid surfaces at high pressure (Alonso-Vicario et al., 2010). As a consequence, pressure swing adsorption process uses the molecular attributes at high pressure to separate two or more gases from a gas mixture using a specific adsorbent material. The adsorbent material used to depend on the target gas required to be separated from a given gas mixture.
It is imperative to note that the amount of pressure used in the process determines the amount of gas adsorbed. The high volume of gases is absorbed in high pressure while low volume is adsorbed at low pressure. It is significant to note that when the pressure is reduced, the adsorbed gas is described or released. Pressure swing adsorption is used to separate a mixture of gases to attain the required gas since various gases are drawn to dissimilar solid surfaces less or more strongly (Ebner et al., 2011).
The technology of gas separation using pressure swing adsorption used different adsorbent materials depending on the type of gas that is required at the output. A gas mixture is passed at high pressure through a vessel that is fixed with a specific adsorbent which attracts one of the gases in the mixture more strongly than the other gas (Dantas et al., 2011). The adsorbent traps most or all of the gas, which is attracted to its surface while allowing the other gas to pass through as output. The pout mixture is enriched with the other gas that is less attracted to the absorbent material. The adsorbed gas trapped by the adsorbent material is then passed through a different vessel under low pressure to release the adsorbed gas.
Application
Pressure swing adsorption has been applied in different situations to separate and purity various gases from a mixture of different gases. The technology outputs high concentration of the target gas since it used highly precise processes. Its advantages have led to its use in several applications including air separation, hydrogen purification, on board gas generation system, noble gas purification, removal of carbon dioxide, methane upgrading and n-ISO paraffin separation. As compared to other separation technologies, pressure swing adsorption is associated with low energy consumption and high efficiency.
References
Alonso-Vicario, A., Ochoa-Gómez, J. R., Gil-Río, S., Gómez-Jiménez-Aberasturi, O., Ramírez-
López, C. A., Torrecilla-Soria, J., & Domínguez, A. (2010). Purification and upgrading
of biogas by pressure swing adsorption on synthetic and natural zeolites. Microporous
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Dantas, T. L., Luna, F. M. T., Silva, I. J., Torres, A. E. B., de Azevedo, D. C., Rodrigues, A. E.,
& Moreira, R. F. (2011). Carbon dioxide–nitrogen separation through pressure swing
adsorption. Chemical engineering journal,172(2), 698-704.
Ebner, A. D., Gray, M. L., Chisholm, N. G., Black, Q. T., Mumford, D. D., Nicholson, M. A., &
Ritter, J. A. (2011). Suitability of a solid amine sorbent for CO2 capture by pressure
swing adsorption. Industrial & Engineering Chemistry Research, 50(9), 5634-5641.
Liu, Z., Grande, C. A., Li, P., Yu, J., & Rodrigues, A. E. (2011). The multi-bed vacuum pressure
swings adsorption for carbon dioxide capture from flue gas.Separation and Purification
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