Introduction to Carbon Molecular Sieve for PSA Nitrogen Generation
With the wave of industrial revolution in the 1950s, the application of carbon materials became increasingly widespread, with the fastest expanding field being activated carbon, which gradually developed from filtering impurities to separating different components. At the same time, with advances in technology, human processing capabilities of matter became stronger, under which carbon molecular sieve was born. In the 1960s, carbon molecular sieves was successfully manufactured and quickly promoted in the United States. Initially, it was used as adsorbents to separate oxygen from air and gradually applied to devices for producing nitrogen. By the late 1970s and early 1980s, the demand for nitrogen worldwide continued to increase, while the technology of pressure swing adsorption for nitrogen production gradually matured, further driving the development of carbon molecular sieve manufacturing technology.
By 1982, nitrogen production in the United States and Japan exceeded that of oxygen. At this time, pressure swing adsorption for nitrogen production accounted for about 18% of total nitrogen production, as the market share of the technology continued to grow, major industrial countries around the world invested in research and development of carbon molecular sieve for pressure swing adsorption, of which the United States, Japan, and Germany were in the leading position technologically. Up to today, major carbon molecular sieve producers worldwide are still mainly distributed in these countries.
The raw materials for carbon molecular sieve are coconut shells, coal, and resins
First, they are processed and ground into powder, then mixed with the substrate, mainly to increase strength and prevent fragmentation of the material. The second step is activation and pore formation, which involves injecting an activator at a temperature of 600-1000 ℃. Commonly used activators include water vapor, carbon dioxide, oxygen, and their mixtures. They react with more active amorphous carbon atoms to chemically generate heat, gradually expanding the surface area to form pores. The activation and pore formation time lasts for 10-60 minutes. The third step is pore structure regulation, using chemical substance vapors such as benzene to deposit on the micro-porous wall of the carbon molecular sieve to adjust pore size to meet requirements.
Carbon molecular sieve is roughly divided into four stages according to their performance differences
In the first stage, carbon molecular sieve had a very uneven pore size distribution due to manufacturing process limitations, and could only produce nitrogen with purity of about 97%-98%, with a recovery rate of only 26% to 34%, requiring high energy consumption.
In the second stage, carbon molecular sieve had improved performance and could produce nitrogen with a purity of over 99.9%, but energy consumption was very high and lacked conditions for large-scale application. In this stage, molecular sieves could produce nitrogen with purity of 97-98%, with a recovery rate of 37%-42%, and had already been widely used.
In the third stage, molecular sieves made significant progress in performance due to improved processing technology, and could produce nitrogen with a purity of over 99.99% in one step, with a recovery rate of 40% when producing nitrogen with 99.5% purity. The third-generation molecular sieves are the most commonly used molecular sieves and are chosen by most manufacturers.
The fourth-generation molecular sieve was successfully developed by a Japanese company in 2001. Compared with the third-generation molecular sieves, its performance had a substantial improvement. Together with Ruiqi’s non-isobaric pressure swing adsorption technology, it is capable of producing nitrogen with a purity of over 99.9995% in one step. When producing nitrogen with 99.99% purity, the nitrogen recovery rate is an incredible 32%. In today’s energy-strapped environment, its significance is even more important.