A 2 mol% NH3-in-air mixture at 68°F and 1 atm is to be scrubbed with water in a tower packed with...

Question

A 2 mol% NH3-in-air mixture at 68°F and 1 atm is to be scrubbed with water in a tower packed with 1.5-in, ceramic Berl saddles. The inlet water mass velocity will be 2400 lbk-ft2, and the inlet gas mass velocity 240 lb/h-ft2. Assume that the tower temperature remains constant at 68°F, at which the gas solubility relationship follows Henry's law, p = Hx, where p is the partial pressure of ammonia over the solution, x is the mole fraction of ammonia in the liquid, and His the Henry's law constant, equal to 2.7 atrnlmole fraction.
(a) Calculate the required packed height for absorption of 90% of the NH3.
(b) Calculate the minimum water mass velocity in lbk-ft2 for absorbing 98% of the NH3.
(c) The use of 1.5-in. ceramic Hiflow rings rather than the Berl saddles has been suggested. What changes would this cause in KGa, pressure drop, maximum liquid rate, KLa, column height, column diameter, HoG, and NoG

David · Accepted Answer

Id -  376240 – 
  Part   -a 
   The mole  of    ammonia   gas  =  2   mol % = 2/100  =0.02    
 Air    moles  = 98 /100  =0.98   
    1.5   inch   ceramic   berl  saddles   rings  - 
 Av  = average  bulk  density  lb/ft3  of tower    volume   =38  lb/ft3 
 Surface  area   av   =  44 ft 2/ft3  ,porosity  = e  = 0.75 
  Gw  = water    mass  velocity  =  2400  lb  /ft2  -hr 
  Gg = gas mass velocity   =              240  lb/ft2-hr  
     Temperature  = 68   0 F   and p=1 atm 
  Henry  constant   = H = 2.7     ,      P = H.X 
  The   average   molecular  velocity   of   the entering  gas  mixture  =  29 *98 /100  +2/100*17 = 28.7 
lb/mole 
   Ρy  =ρy  = density  of gas   = 28.7 *(460+32) /359*(468+68)  =  0.0745  lb/ft3 
 Ρx   = ρx =  62.3 lb /ft3   ,  μ = viscosity  =  1  cp  
  Gc  =  4.17  *10^8   ft-lb /lb- hr2   , Gx /Gy = 1.0 
 For  1.5 in  ceamic    berl   saddles – 
 Av  = 44  ft2 /ft3  ,  e  = 0.75  
 Gx /Gy *(ρy/ρx)^1/2 = (0.0745/62.3 )^1/2 =  0.0346   
   Gy ^2 ( μ’)^0.2  ( 62.

A 2 mol% NH3-in-air mixture at 68°F and 1 atm is to be scrubbed with water in a tower packed with 1.5-in, ceramic Berl saddles. The inlet water mass velocity will be 2400 lbk-ft2, and the inlet gas...

Solution

Answer To This Question Is Available To Download

Related Questions & Answers

Submit New Assignment