Supplemenal Maerial for Transpor Process and Separaion Process Principles Chaper 1 Liquid Liquid and Fluid Solid Separaion Processes This chaper includes examples of adsorpion processes where one or more componens of a gas or liquid sream are adsorbed on he surface of an adsorben maerial. The following problem module illusraes pressure swing adsorpion process for purifying hydrogen for proon exchange membrane fuel cells. 1.-1 Hydrogen Purificaion in Pressure Swing dsorpion Process Daniel López Gaxiola 1 Suden View Jason M. Keih
Liquid Liquid and Fluid Solid Separaion Processes Example 1.-1 Hydrogen Purificaion in Ehanol Reforming Process The dry reformae sream coming from an ehanol reforming process conains 7 mole % H and mole % CO. Lopes e al. [1] sudy he adsorpion of CO on a packed bed of acivaed carbon wih a lengh of.67 m. The bed conains 45.6 kg of adsorben maerial consising of acivaed carbon, wih a paricle diameer of.9 mm. The average flow rae of he dry reformae is kg a densiy of.587. m 5 m 5 1 and has s Use he daa in he following able o deermine he ime required o reach he break poin C concenraion =.1, he ime equivalen o he oal capaciy of he bed, and he ime C equivalen o he usable capaciy of he bed up o he break poin ime. lso calculae he lengh and capaciy of unused bed afer he break-poin ime. Wha is he sauraion capaciy of he bed? Breakhrough Concenraion of CO in he packed bed Sraegy (s) C/C (s) C/C 149.8814 7.6 164.966 187.15 187.918 48.58 19.9444 6.191 17.9569 61.487 4.9695 64.449 7.9757 667.4884 56.9819 747.56 77.9817 85.6661 85.9879 97.7168 1.994 167.7611 8.998 1.855 44 1. 16.8561 6 1. The break-hrough and capaciy of he packed bed can be deermined using he design equaions given in Secion 1.D of Geankoplis. Soluion Firs, he break poin ime can be obained from he abulaed daa, a he poin where be equal o b = s C.1 C = o 1. Lopes, F.V.S., Grande, C.., Rodrigues,.E., Chemical Engineering Science, 66, 17 (11) Daniel López Gaxiola Suden View Jason M. Keih
Supplemenal Maerial for Transpor Process and Separaion Process Principles The ime for he oal capaciy of he bed can be calculaed using he inegral of he funcion of ime: C curve as a C C = 1 d = + 1 C where 1 and are he shaded areas shown in he following figure: C/C 1..9.8.7.6.5.4...1. 5 1 15 5 5 4 (s) 1 C b s i can be seen in his figure, we can deermine he break hrough ime by calculaing he areas 1 and. Thus, 1 ( )( ) = s s 1 1 = s Daniel López Gaxiola Suden View Jason M. Keih
Liquid Liquid and Fluid Solid Separaion Processes To deermine he area, we can use he rapezoidal mehod o calculae he area under he curve and subrac i from he oal area of he recangle, as shown below: C/C 1..9.8.7.6.5.4...1. 5 1 15 5 5 4 (s) 1 The area of he recangle o he righ of he break poin can be calculaed as follows: = ( s s)( 1 ) = 41 s The resuls for he numerical inegraion using rapezoidal mehod will yield: = s Now we can obain he area o be: = = 41 s s = s We can subsiue he areas 1 and ino he equaion for he break-hrough ime, o obain: = s + s = s Daniel López Gaxiola 4 Suden View Jason M. Keih
Supplemenal Maerial for Transpor Process and Separaion Process Principles The ime equivalen o he available capaciy of he bed before he break poin ime can be obained as shown in he following seps: b C u = 1 d = C u = s The lengh of he unused bed can be calculaed using Equaion 1.-4 of Geankoplis: u HUNB = 1 HT where: H T = Toal lengh of he packed bed Subsiuing he imes we calculaed and he lengh of he packed bed ino his equaion, we ge: s HUNB = 1 m s HUNB =.1 m ( ) Finally, o deermine he sauraion capaciy of he acivaed carbon in he bed, we need o obain he moles of carbon dioxide adsorbed on he bed. The carbon dioxide can be obained by muliplying he iniial concenraion of CO in he gas by he mass of gas in he ime of s. Thus, Toal CO adsorbed kmol CO 5 m kg gas. 5 1 ( s).587 kmol gas s m kg CO = kg gas kmol CO kmol gas Toal CO adsorbed = kg CO The molecular weigh of he gas mixure was obained by muliplying he molar fracion of each componen by is corresponding molecular weigh and adding he resuls, as shown below: Daniel López Gaxiola 5 Suden View Jason M. Keih
Liquid Liquid and Fluid Solid Separaion Processes kg H kg CO Mgas = yh M H + y CO M CO =. + kmol H kmol CO M gas kg = kmol Now we can divide he oal CO adsorbed by he mass of acivaed carbon on he bed. Hence, kg CO Sauraion Capaciy = 45.6 kg adsorben kg CO Sauraion Capaciy = kg adsorben Daniel López Gaxiola 6 Suden View Jason M. Keih