CPB30803 DESIGN PROJECT 2 (PLANT & PROCESS OPTIMIZATION) L01-P10 JANUARY 2016
DESIGN A UREA PLANT WIT CAPACITY CAPACITY O! 100" 000 METRIC TONNES # YEAR
SUPER$ISOR% MR SYAIDI !ADZLI AL!AN
SARI!A ADAWIYA SYED IDRUS
20111313
MUAMAD NIZAMUDIN MUSTA!A
201113601
MOAMAD AZAM SAARUDDIN
201113660
SITI SYAZWANI MOD NASIR
2011138'
MUAMMAD IZZAT A!IZUDDIN MOD SA 20121'260 20121'26 0
D*+,*,+ U. R./ C,*.*, !. *, C4, T5 7 R./
This process implicated the reaction between gas and liquid. The liquid mixture of NH3 and carbamate (180!" and gaseous !#$ (1%0!" are fed to reactor. These two different phases classified as heterogeneous reaction. The& meet at 1'0ᵒ! and 1) atm pressure inside the reactor to form ammonia carbamate (NH$!##NH%". The reaction ta*ing place in the parameters of reactor are as follows. $NH3 + !#$ ,NH$!##NH% + Heat (2xothermic reaction"
-H 13/.$3 *mol
NH$!##NH% + Heat , NH $!#NH$ + H$0 (2ndothermic reaction" 4 deh&dration process
-H 1.) *mol
#5erall reaction6 $ NH3 + !#$ , NH$!#NH$ + H$0 (2xothermic reaction"
-H 118.// *mol
7rom the abo5e reaction which occurs in the reactor it can be identified as re5ersible process. 9hereb& the reaction between $ mols of liquid NH3 and 1 mol of gaseous !#$ will produce 1 mol of NH$!##NH% and 1 mol of H$#. This reaction will react re5ersel& forming bac* $ mols of NH3 and 1 mol !#$. This re5ersible reaction basicall& e5aluated at equilibrium condition. 7ollowing are the *inetics parameter in5ol5ing in the reaction inside the reactor. Howe5er this reaction considered as liquid phase reaction due to the outlet flow out from the reactor in liquid form. T.9 1 :arameter in the reactor P..: 9or*ing temperature ;esign temperature 9or*ing pressure ;esign pressure
$.9 1'0ᵒ ! $)0ᵒ ! 1) atm $10 atm 0= /0.'3*mol ) 1 %.$)' > 10 min
2
The reaction rate constant * was determined b& using
k = A e RT 7rom the existence parameter the 5alue of * was calculated as follows. k =( 4.259 X 10 5 min ˗ 1 ) e
− 60930 J /mol (8.314 J / molK )( 463.15 Kk )
−1
k =0.05719 min −1
k =3.4314 hr
( First order reaction)
The 5alue and unit obtained dri5e to the first order of reaction. ?o the appropriate rate law is
−r A= k C A This shows the reaction obe&s a nonelementar& @ate Aaw whereas the rate equation cannot be determined b& loo*ing at the stoichiometric coefficient. Therefore all the features obtained correspond to plug flow reactor (:7@".
!*+ 1 :lug flow reactor
3
M. & . B.9.,/ 7 R./ T.9 2 Bass Calance of each component inside reactor
R./ 4
NH$!##NH% + heat , NH$!#NH$ + H$# $NH3 + !#$ , NH$!##NH% + heat
-H 1.) *mol -H 13/.$3 *mol
T.9 3 Heat balance for @eactor
1. Total DḢ1+DḢ$+DḢ3 18)330.)%38 Bda& $.
(−117 ) DH) %0'.3%%E
78
3
∗10
DH) /1%0$1.)%1 Bda& 3. Frea formation heat b& decomposing
∑ ṅḢ out
∑¿ ṅḢ 5
$38''.)%%+18)330.)%38/1%0$1.)8%1 1)%'1.)%% Bda& R./ $9:
Cased on Table $ inlet each component for the reactor are con5erted from TIr to *ghr. The 5alues are as follows. T.9 ' Jnlet reactor C:,, NH3 !#$ NH$!##NH%
I,9 R./" T#Y 10$)$/.1'3 $%83'./%30 1%138.13')
I,9 R./" +#4 10/1./ $)$.3' 1/'/.)'
;etermination of inlet 5olumetric flowrate K0 for each component densit& inlet must be considered. T.9 ;ensit& Jnlet C:,,
D,*5 (;+#:3)
NH3 (liquid"
/18
!#$ (gas" at %0ᵒ!
( @ef6 H :err&"
$.38
(densit&:B@TL :1/$ atmT313 M"
1/00
(@ef6 http6www.inorganics.basf.com"
7ollowing are the calculation and 5alue of K0 for each components and total. T.9 6 Jnlet 5olumetric flowrate
m ρ
C:,,
I,9 <9:*/ 79=."
V 0
(
3
m / hr V Ao NH 3
V Bo
V Co
10617.6 kghr ˗ 1
1.181
618 kgm‐ 3
C2
2572.39 kghr ˗ 1
'.$%
277.38 kgm‐ 3
16796.59 kghr ˗ 1
10.%'8
1600 kgm‐ 3
6
NH 2 C NH 4 Total
V ¿
3/.')3
V !FR
R./ $9:" "
V !FR = F Ao
∫ −dX r 0
A
−r A= k C A F A F Ao (1 − X ) = =C Ao ( 1− X ) C a= V V 0
"
V !FR = F Ao
∫ −dX r 0
A
"
V !FR = F Ao
∫ kdX C 0
A
"
V !FR = F Ao
∫ k C dX ( 1 − X ) 0
V !FR =
V !FR =
V !FR =
V !FR =
F Ao k C Ao F Ao k C Ao
[
V o k
Ao
"
∫ (1dX − X ) 0
[
ln
ln
1 1− "
1 1− "
36.953 m
3
] [
/ hr
3.4314 hr
]
−1
ln
1 1− 0.7
] 7
3
V !FR =12.966 m
R*,/ *: , t t =
t =
V V 0
12.966 m 36.953 m
3
3
/ hr 60 min
t =0.351 hr X
1 hr
t = 21.05 min
8
9
M/4.,*/.9 *+, 7 4 ./
Baterials for designing reactor S ;:$89" and stainless steel ($)!r$$Ni$Bo S 31/A F". Titanium had been used widel& in the s&nthesis reactor of the total rec&cle plants till earl& 1'0s and the high pressure (H:" stripper of ammonia stripping process till earl& 1''0s. Jt has good passi5ation propert& with less passi5ation air. Howe5er titanium is susceptible to erosion and it is difficult to weld. #ther than that The life time of titanium is limited (unePa $013".;ue to this disad5antages titanium has been graduall& ta*en o5er b& stainless steel. ?tainless steel has been widel& used for this equipment in urea plants. ?tainless steel is almost immune to erosion and has good weldabilit& but requires large amount of passi5ation air for urea s&nthesis equipment compared to titanium. T&pe 31/A F has been used for a long time in urea plants mainl& because of its excellent weldabilit& fair corrosion 10
resistance and relati5el& low cost. @equirement of huge amount of passi5ation air b& 31/A F in s&nthesis and rec&cle sections restricts its operab ilit&.
T.9 >
T&pe $)!r$$Ni$Bo ?? is being used due to its better corrosion resistance than 31/A F and excellent weldabilit&. This t&pe of metal has been used in reactor and strippers but it is susceptible b& chloride to ?!! and costl&. ;uplex ?? shows excellent corrosion resistance in both 9eld metal and H
11
12
. .,7 <*/ DESIGN O! AMMONIA PREEATER
COLD !LUID TUBE SIDE
Bean ammonia temp. (338+8'./"$ $13.8 7 101 o c Tube crosssectional area (3.1%%"E1/$ $01mm$ Tubes per pass no.of tubes$ )13$ $)/.) $)/ Tube flow area ($)/E$01"1000000 0.0)1m$
14
I,:,.*, ., P/ C,9 L<9 C,9 *,* 4 R./ ( C./. C,9 )
Level Controller
Flow Controller
Output !alve
Output Flow Proce
Reactor Level
L"#u"$ level
Output Flowrate
L"#u"$ Level
@eactor Ae5el is affected b& changes in output flow rate Control Strategy: handle reactor le5el b& adPusting the flow rate of the product output. Jf a disturbance in output flow rate occurs 7! will act quic*l& to hold the output flow rate at its ?et :oint. !ontrol s&stem measures @eactor le5el and compare it to set point le5el of the reactor. Then uses the resulting error signal as the input to a controller for output flow rate.
T:. C,9 *,* 4 R./ ( C./. /,9 )
%e&perature Controller
Flow Controller
'tea& !alve
'tea& Flow Proce
Reactor %e&perature
'tea& Flowrate
%e&perature "n"$e reactor
@eactor Temperature is affected b& changes in reactant feed Temperature Control Strategy: handle reactor temperature b& adPusting the flow rate of the steam on the steam Pac*et. :rimar& control loop (TT S T!" ?econdar& (7T S 7!" The hot steam is used b& B
%e&perature Level
!ontrol s&stem measures ac*et Temperature and compare it to set point temperature of the reactor. Then uses the resulting error signal as the input to a controller for steam ma*eup.
PRINCIPAL: the $ndmanipulated 5ariable is located closed to potential disturbance S react quic*l&
P /,9 *,* 4 R./ ( C./. /,9 )
Preure Controller
(a Flow Controller
(a !alve
(a Flow Proce
Reactor Preure
Preure Level
(a Flowrate
Reactor Preure
@eactor :ressure is affected b& changes in gas flow rate Control Strategy: handle reactor pressure b& adPusting the flow rate of the gas. Jf a disturbance in gas flow rate occurs 7! will act quic*l& to hold the gas flow rate at its ?et :oint. !ontrol s&stem measures @eactor pressure and compare it to set point le5el of the reactor. Then uses the resulting error signal as the input to a controller for gas flow rate.
O<.99 P/ C,9 . R./
)eat *+c,an-er
(a
/&&on"a Ca
FC
!ascade is desired when the single loop performance is unacceptable and a measured 5ariable is a5ailable. Cesides that the secondar& 5ariable must indicate the occurrence of an important disturbancein the s&stem. 7urthermore the secondar& 5ariable also must ha5e a faster response than the primar& which is % times faster than the primar& in order to get a better control.
AD$ANTAGES O! CASCADE CONTROL
The cascade control is an impro5ement of the feedbac* and feed forward control s&stem because the con5entional feedbac* usuall& ta*e the correcti5e action for disturbance after the control 5ariable de5iates from set point. Cesides that the feed forward requires to calculate the disturbance explicitl& and hence a5ailable to calculate the control 5ariable. 7urthermore emplo&ment of secondar& measurement point and secondar& feedbac* controller are required for recogniOes the upset condition sooner. Jn conclusion cascade control s&stem are much more applicable in the reactor control s&stem because it ha5e large impro5ement in performance when the secondar& is much faster than primar& simple technolog& with :J; algorithms use of feedbac* at all le5els since primar& has Oero offset for Xstepli*eY disturbances. 7urthermore plant operating personnel find cascades eas& to operate because cascade at one le5el cause all controllers abo5e to become inacti5e
opening
