The photo is sourced from rscf.ru
The most efficient way to remove heavy hydrocarbons (containing more than three carbon atoms) from natural gas is to use gas separation membrane units made on the basis of silicious polymers. The membranes in such units consist of the dense separation layer and the porous base. The separation is done due to different permeability of the natural gas components: heavy hydrocarbons (ethane, propane, butane) go through the separation layer dozens of times faster than methane. After the separation layer the methane/ethane/propane/butane mix goes through the porous base, and this leads to removal of foreign impurities from methane.
Ideally, the base should not create any barriers for gas movement. This is required for fast movement of the heavy hydrocarbons through the separation layer and faster removal of impurities from methane. That is why the efficiency of gas separation membrane depends on the base throughput, which, in turn, is in the inverse proportion of its resistance.
The scientists from the A.V. Topchiyev Institute of Petrochemical Synthesis of the RAS developed the base made of sulfur-containing fiber polymer (polysulfone) with the wall thickness making 300 micrometres (µm), which is approximately 10 times thinner than a single human hair. To assure the maximum resistance of the membrane, the developers changed the structure of the surfaces of fibres supplying saturated hydrocarbons (pentane, hexene and heptane) inside the base. This made the gas permeability of the base 10 times higher the gas permeability of all previously known porous hollow-fiber analogue. Thereby, this development may double the throughput of the composite membranes and reduce the energy costs of gas separation more than 9 times.
“Our laboratory is currently developing not only the bases, but also new materials for separation layers of the gas separation membranes. As of now, rather thick separation layers are used – about 3 thou nanometres. We are trying to find the way of making them thinner and increasing the throughput of the composite membranes even more”, the Russian Science Foundation is citing Dmitry Matveyev, one of the authors of the study, the engineer of the polymer membranes lab of the Institute of Petrochemical Synthesis of the RAS.