Question

Ultra-pure hydrogen is required in applications rang- ing from the manufacturing of semiconductors to powering fuel cells. The crystalline structure of palla- dium allows only the transfer of atomic hydrogen (H) through its thickness, and therefore palladium mem- branes are used to filter hydrogen from contaminated streams containing mixtures of hydrogen and other gases. Hydrogen molecules (H) are first adsorbed onto the palladium's surface and are then dissociated into atoms (H), which subsequently diffuse through the metal. The H atoms recombine on the opposite side of the membrane, forming pure H, The surface concen- tration of H takes the form C = Kp where K 1.4 kmol/m.bar is known as Sieverts constant. Con- sider an industrial hydrogen purifier consisting of an array of palladium tubes with one tube end connected to a collector plenum and the other end closed. The tube bank is inserted into a shell. Impure H, at T = 600 K, p = 15 bars, X = 0.85 is introduced into the shell while pure H, at p = 6 bars, T = 600 K is extracted through the tubes. Determine the production rate of pure hydrogen (kg/h) for N = 100 tubes which are of inside diameter D, = 1.6 mm, wall thickness 1 = 75 pm, and length L = 80 mm. The mass diffusiv- ity of hydrogen (H) in palladium at 600 K is approxi- mately DAB = 7 X 10 m/s.

Answer 1

2010 july 0.5 monday 5 Surface concentration of H₂ at 15 bax = Kg P H 1936-175 5 = 1.4 kamol 1 m3 bass X 15 banjos = 10.926 kg/m3 Surface con of H₂ at 6bar = 6.914 kolm The value of 8C = 10.926-6.914 = 4:012 kg/m3 10 The value of a = 7x109 m²/s (diffusion coeffre The thickness of palladium tube Arany = 75 um = 75x10 edi 12 Area of palladium tube Apoll = 0.394x100 m² immer rection = 0.8 mm outor reeditur - 0.875 mm length = 80mm 2 The mo of palladiun tuki Na Loo The mass of hydrogen Marydrog-Ed Aparat x 8c this Mrazdrogen = 7X109 x 0.394x108x3600 (4.012 75X106 notes = 0.5 31x10 kg/h 100 tubes of palladium Maydrogen = 0.531 x 104 kg/h 1/2010 wfmtwTFS 14 9 10 11 12 13 14 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 5 6 7 8