(436f) Microstructure Design of Carbon Materials and Matched Adsorption Process for the Low-Grade Methane Separation from Its Mixture with Nitrogen

Microstructure design of carbon materials and matched
adsorption process for the low-grade methane separation from its mixture with
nitrogen

Kai Lu (speaker), Donglei Qu, Ying Yang, Li Ping*,
Yu Jianguo

State Key Laboratory of Chemical
Engineering, College of Chemical Engineering, East China University of Science
and Technology, Shanghai 200237, China

*Correspondence
author email: 13671654719@163.com, liping_2007@ecust.edu.cn

Abstract

Methane is not
only a clean and high caloric fossil fuel, but also the second largest
greenhouse gas after carbon dioxide with dramatic influence
on climate change. Besides natural gas, unconventional nature gases, such as
coalbed gas, shale gas, oil-field gas, landfill gas, biogas, etc, also have CH₄ as the main component. Due to the high impurity content in these feedstocks, the CH₄ separation and enrichment processes are always
required before
unconventional nature gases can be used for power generation, chemical raw material and other processes. Due to the weak
polarities of CH₄ and N₂ and their similar
physicochemical properties, the microporous adsorbents have a little amount of
adsorption capacity for the low-concentration methane, and the separation of CH₄/N₂
is also very difficult to accomplish by the adsorption-based process.

In this work, we shall investigate the microstructure effect of carbon
materials on the low-concentration methane adsorption separation from its
mixture with nitrogen, including raw material or precursor for carbon skeleton
formation, effect of the specific surface area of carbon material on the
low-concentration methane adsorption amount, relationship between micropore
size distribution of carbon material and CH₄/N₂
adsorption separation mechanism, and effect of different activator on the weak
polar methane adsorption capacity, as shown in Fig. 1.

Fig. 1 microstructure effect of carbon
materials on the low-concentration methane adsorption separation from its
mixture with nitrogen. (a) Comparison between carbon molecular sieve and
activated carbon, (b) comparison among activated carbons with different
precursor.

After
microstructure analysis, the potential carbon materials are recommended for the
low-concentration methane adsorption separation from its mixture with nitrogen.
Then, two adsorption
processes, vacuum pressure swing adsorption (VPSA) process and CO₂
displacement VPSA process, as shown in Fig. 2, are adopted to separate CH₄/N₂
and recover the low-concentration methane. According to the experimental results
and simulated data, the matched adsorption process to the
potential carbon material is discussed in order to recover effectively the
low-grade methane from its mixture with nitrogen.

Fig. 2 VPSA processes with and without CO₂
displacement for the low-concentration methane adsorption separation from its
mixture with nitrogen.

Keywords: Methane enrichment; CH₄/N₂
separation; microstructure of carbon material; VPSA process; unconventional
nature gas