Upgrading Biogas to Biomethane Using Membrane Separation

Abstract

Biogas contains carbon dioxide in the range of 35−45 vol %. Upgrading biogas to biomethane is primarily based on carbon dioxide removal. Biomethane is essentially purified biogas that contains at least 95 vol % methane and it can be either used as fuel for vehicles running on compressed natural gas (CNG) or injected into the natural gas grid. Nowadays, various techniques are used for CO 2 removal from biogas. Among the most commonly used technologies are adsorption, absorption, cryogenic separation, and membrane separation. Currently, in the Czech Republic, no units for biogas upgrading to biomethane are operating. In addition, during the summer months, there is heat overproduction from the co-generation units. In this work, a suitable unit for carbon dioxide separation is proposed. Carbon dioxide separation is possible using membrane separation. Along with carbon dioxide, minor compounds present in biogas such as hydrogen sulfide and water are also separated. The implementation of this unit makes it possible to obtain biomethane form biogas. Membrane separation was tested in a pilot scale using real biogas. All experimental tests were conducted at the Central Waste Water Treatment Plant in Prague. Experimental tests were performed using different types of membranes. For comparison purposes, the following membrane modules materials were chosen: polysulfone and polyimide fiber membranes. Separation of moisture and trace compounds present in biogas was tested for these two types of membrane materials. Other tests were performed using polyimide membranes. Parallel connection of membrane modules was the most effective to remove carbon dioxide from biogas. Purified biomethane contained at least 95 vol % of methane, as is required, even when the highest flow rate was applied of 7 m 3 h −1 of biomethane (measuring conditions: 0.6−0.8 MPa). This small membrane separation unit is recommended for biogas units in wastewater treatment plants.

Ultrathin Films of Porous Metal–Organic Polyhedra for Gas Separation

“…This solution‐based method is highly selective but requires high regeneration temperatures, which reduces its recyclability and increases its cost, making it difficult to implement on a large scale . Alternatively, CO 2 separation by membranes has emerged as an environmentally friendly and more cost effective method, and can be applied to other processes of interest such as the upgrading of biogas to biomethane . However, current membranes lack the capacity to treat huge amounts of flue gas with the required selectivity for CO 2 .…”

“…[1] Alternatively,C O 2 separation by membranes has emerged as an environmentally friendly and more cost effective method, [2] and can be appliedt oo ther processeso fi nterest such as the upgrading of biogast ob iomethane. [3] However,c urrent membranes lack the capacity to treat huge amountso ff lue gas with the required selectivity for CO 2 . [4] Accordingly, membranesa ble to achieve high gas flux (permeance)whilemaintaining ahigh selectivity for CO 2 are intensively sought.…”

Molecular Dynamics Simulation of Methane and Carbon Dioxide Permeation Through A Layered Inorganic Membrane

“…In the absence of condensation or adsorption, the permeation of gas molecule through narrow opening can be considered to follow the Knudsen flow mechanism 34 . For a gas molecule that permeates through cylindrical-pore of radius r at constant temperature T, the Knudsen diffusion is expressed as (2) with M i is the molar mass of the i-th gas species, and R is the gas constant. The Knudsen diffusion D K,i is a constant quantity that inversely proportional to the molecule molar mass.…”

“…The rising of methane and carbon dioxide level in the atmosphere is mainly from anthropogenic emission and it is projected to increase due to economic growth and industrial development. Therefore, the need for a reliable gas separation methods to remove carbon dioxide will see an increasing demand with the continuous effort to upgrade the quality of natural gas, biogas, landfill gas, and atmospheric environment [1][2][3] .…”

Purification of model biogas from toluene using deep eutectic solvents

“…Applied biogas purification technologies are based on adsorption, absorption, biological methods, membranes technologies, cooling or processes using various types of catalysts [4][5][6].…”