Column Tag No.:
HCL Scrubber Job No.:4506A Client :JOL
Project :SR - Plant -4, 5Input Data
Stream
:
HCL Vap.
Packing type =Intallox Saddles Packing size =25mm Packing MOC
=PP Gas pr. Drop / m bed =15mmWC / m packing height =147.1(N/m 2
)/m
Total packing height
= 3.2m (including all packed beds)
Gas / Vapour Properties Gas / Air flow rate =
OR
0m 3
/h == 0m 3/s
Gas pressure at entry = 1.0000atm
Gas temperature at entry =30.00o
C =303.00o
K
Gas / Air mol weight
=
29
Component to be scrubbed Component Name =HCL Vap
Component flow rate =70Kg/h % comp. in air/gas =6% (v/v)Molecular weight of comp.=
36.5
3
Conversion :
Liquid Viscosity, μL =0.0035000Ns/m 2 3.5C p =
Ns/m 2
Packing factor, F p
=
21m -1
Charac. Packing Factor,C f =33 Ref. Table 6.3, Characterstics of Random packings
Conversion factor, J = 1.0factor for adequate liquid distribution & irrigation across the bed
SCRUBBER DESIGN (PACKED COLUMN)
0.00350000
Calculations
Since larger flow quantities are at the bottom for an absorber, the diameter will be chosen to accommodate the bottom conditions.To calculate Gas density Avg. molecular weight =29.45Kg / Kmol
Select vol. flow rate and mass flow rate from above,Selected mass flow rate =0.277778Kg/s
Selected vol. Flow rate =0.234499m 3
/s Selected molar flow rate =0.009432Kmol/s Therefore, gas density
=
1.1846Kg/m 3
(mass flow rate / vol. Flow rate)
To find L', G' and Tower c/s area
Assuming essentially complete absorbtion, Component removed =0.0207Kg/s (molar flow rate x % comp. x mol. Wt.)
Liquid leaving =0.0420Kg/s (Inlet liquid flow rate + comp. Removed)
0.5
=0.00497
Using
0.00497
as ordinate, Refer fig.6.34 using a gas pressure drop of 147.1(N/m 2
)/m
G' 2 C f μL 0.1 J =
0.04 (from graph)
G ) g c Therefore, G'
=
0.5
=
1.6665Kg / m 2
.s Tower c/s area =0.1667m
2
( c/s area = mass flow rate / G' )Tower diameter
=0.4607m =
460.7mm
=500mm Corresponding c/s area
=
0.1963m 2
TO CALCULATE COLUMN DIAMETER
Efficiency of fan / blower
=
60%
To calculate pressure drop Pressure drop for irrigated =470.72N/m 2
(pressure drop per m packing x total ht. of packing)
packing
For dry packing,
O/L Gas flow rate, G'=
2.s (Gas inlet flow rate - Component removed) / c/s area
O/L Gas pressure
=2
(subtracting pressure drop across packing)= gas mol wt. x 273 x gas o/l pr. 22.41m3/Kmol T in kelvin 101330=C D =
96.7 Ref. Table 6.3, Characterstics of Random packings
Delta P = Z
=
2
Pressure drop for packing =613.61N/m 2(irrigated packing + dry packing)Pressure drop for internals =25mmWC
(packing supports and liquid distributors)
=245.17N/m
2
Gas velocity
=7.5m/s
Inlet expansion & outlet = 1.5 x Velocity heads = 1.5 x (V 2
/ 2g)contraction losses
=42.19N m / Kg
=49.97N/m 2
(divide by density)
Total pressure drop =
908.75N/m
2
(packing + internals + losses)
Fan power output
=pressure drop,N/m 2 x (gas in - component removed) Kg/s
O/L gas density, Kg/m 3
=201.35N .m / s =0.20kW Power for fan motor
=0.34kW (fan power output / motor efficiency)
=
0.45hp
TO ESTIMATE POWER REQUIREMENT
Liq.-Vap. Flow factor, F LV
=
=Design for an initial pressure drop of
15
mm H2O /m packing
From K 4
v/s F LV ,K 4
=0.85K 4 at flooding =
6.50
Trial % flooding
==Gas mass flow rate, V m
==
3.7763kg/m 2
.s Trial column c/s area
=V / V m (Trial A s )
=
0.0736m 2Trial column dia., D =
0.3060m
D = (4/pi) x Trial A s
Round off 'D' to nearest standard size Therefore, D =0.500m
Column C/S area, A s
=0.1963m
2
A s =(pi/4) x D
2
% flooding =13.5472
% flooding = Trial % flooding x (Trial A s / A s )
Conclusion
Generally packed towers are designed for 50% -- 85% flooding.If flooding is to be reduced,
(i) Select larger packing size and repeat the above steps.OR
(ii) Increase the column diameter and repeat the above steps.
COLUMN DIAMETER / HYDRAULIC CHECK
(1/2)
Input Data 0.018 N/m =dyne/cm Liquid-phase Surface Tension, =20dyne/cm Liquid Viscosity = 3.5cP n
=
1.13080
Calculation ln HETP =0.837437HETP
=
=
For separations, less than 15 theoritical stages, a 20% design safety factor can be applied.Considering 20% safety factor, HETP =0.845065m
For separations, requiring 15 to 25 theoritical stages, a 15% design safety factor can be applied.HETP =HETP PREDICTION
Norton's Correlation Applicable Norton's Correlation NOT applicable
18