Methane separation

The hydrogen in the vapor stream is a reactant and hence should be recycled to the reactor inlet (Fig. 4.8). The methane enters the process as a feed impurity and is also a byproduct from the primary reaction and must be removed from the process. The hydrogen-methane separation is likely to be expensive, but the methane can be removed from the process by means of a purge (see Fig. 4.8). 

Table 4 summarizes commercial and precommercial gas separation appHcations (86,87). The first large-scale commercial appHcation of gas separation was the separation of hydrogen from nitrogen ia ammonia purge gas streams. This process, launched ia 1980 by Monsanto, was followed by a number of similar appHcations, such as hydrogen—methane separation ia refinery off-gases and hydrogen—carbon monoxide adjustment ia oxo-chemical synthetic plants. 

Dissolution of the higher boiling gases in an oil absorber of hexane, leaving the methane separated. 

Effect of Pressure on Single-Column Process for Helium-Methane Separation... 

Figure 2. Flow diagram for methane separation by absorption/stripping method.

The second technique for C02/methane separation is membrane permeation, now standard in industry. Cryogenic distillation may be applied for methane-enrichment purposes with some technical precautions because of C02 freezing. Equilibrium adsorption on activated carbon would give poor separation. Molecular sieving would permit only the removal of oxygen and nitrogen. 

Tong, J., Matsumura, Y., Suda, H., and Haraya, K. Thin and dense Pd/Ce02/MPSS composite membrane for hydrogen separation and steam reforming of methane. Separation and Purification Technology, 2005, 46 (1-2), 1. 

Carbon dioxide-methane separation Solvent vapor recovery Hydrogen and carbon dioxide recovery from steam-methane reformer off-gas Hydrogen recovery from refinery off-gas Carbon monoxide-hydrogen separation Alcohol dehydration Production of ammonia synthesis gas Normal-isoparaffin separation Ozone enrichment... 

Carbon dioxide—methane separation from Landfill and biogases PSA [15]... 

Each sample cylinder was analyzed, in order to assure their homogenity, using a Varian Vista 6000 Gas Chromatograph. When developing this technique we encountered the common G.C. problems separation of Ethane from Methane in the presence of 90% Methane, separation of Isobutane from Butane, Isopentane from Pentane and condensation of higher hydrocarbons (Hexane, Heptane) on intermediate lines before injection. 

Baoyong Zhang, Yuanping Cheng Wu Qiang 2011. Sponge effect on coal mine methane separation based on clathrate hydrate method. Chinese Journal of Chemical Engineering, 19(4)610-614. 

Baoyong Zhang Qiang Wu 2010. Thermodynamic promotion of tetrahydrofiiran on methane separation from low-concentration coal mine methane based on hydrate. Energy and Fuels, 24 2530-2535. 

Yave, W., Shishatskiy, S., Abetz, V., Matson, S., Litvinova, E., Khotimskiy, V. and Peinemann, K.V. 2007. A novel poly(4-methyl-2-pentyne)/Ti02 hybrid nanocomposite membrane for natural gas conditioning Butane/methane separation. 

Figure 6.4 Pure gas transport data at 25 °C of membranes AF1600 (O), AFl 6 350 30 fD), AF16 80 15 (A), AF16 80 30 (U), AF16 80 40 ( 0), silicalite-1 (O) as derived from literature data (see text), and predictions of the Maxwell model fora AF16/MFI30% membrane ( ) (a) Pure gas steady state permeability vs kinetic diameter of the permeating molecules (b) gas/methane separation factor (c) gas diffusion coefficients from time-lag experiments vs kinetic diameter (d) gas solubility vs the e/k Lennard-Jones parameter...

D. Q. Vu, W. J. Koros, S. J. Miller, Fouling of carbon molecular sieve hollow-fiber membranes by condensable impurities in carbon dioxide-methane separation, Ind. Eng. Chem., 42, 1064 (2003). 

Quench column 6 Gas purification 7 Drier 8 Low-temperature cooler 9 Hydrogen/ methane separation 10 Demethanization column 11 Deethanization column 12 Acetylene hydrogenation 13 Ethylene column 14 Depropanization column 15 Methylacetylene hydrogenation 16 Propylene column 17 Debutanization column 18 Depentanization column 19 Residue column... 

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