Purification of gases through the PSA(Pressure Swing Adsorption) process - fundamentals and cycles at pressure

Over time, gas purification has taken on a very significant role in the industrial world, since it has become indispensable for any professional who has to use at least one gas in his or her production or transformation process. Indeed, with the tightening of environmental protection regulations and the growing importance of controlling greenhouse gas emissions, atmospheric emissions must be increasingly selective and controlled. A number of examples have since demonstrated that these "constraints" can, on the contrary, be a real added value for the industrialist, thanks to better management of raw materials, which often represent a very significant proportion of production or transformation costs. Of course, investing in plant upgrades is not always an easy decision, from both an economic and a technical point of view, but when it comes to a new project, it is often possible to develop a harmonious and economically viable technical solution.

Four technologies are now commonly used to purify gases:

• distillation processes, cryogenic or not ;

• membrane permeation processes ;

• chemical absorption processes (MEA, DEA, MDEA...) or physical absorption processes (alcohols, glycols...), or a combination of both depending on the solvent chosen;

• finally, adsorption processes, which include the pressure-modulated PSA, RPSA, VSA and VPSA processes covered in this dossier, and the temperature-modulated TSA processes.

This dossier [J 3 606] "Gas purification using the PSA process –Fundamentals and pressure cycles" is the first part of a normal sequel to the dossier "Adsorption – Processes and applications" [J 2 731] . Its aim is to provide the reader with the additional practical information needed to fully understand the fundamental criteria to be mastered in adsorption, as well as the constraints linked to the implementation of pressure cycles.

After reading this dossier, the reader will be able to evaluate the conditions of use of PSA purification technology, and to integrate the fundamental elements necessary for the design of PSA cycles through a knowledge of :

• the feasibility of PSA gas purification;

• adsorbents, their adsorption properties and their sequencing;

• the elementary stages of the PSA cycle, their...