9.17
Sulfur dioxide is oxidized to sulfur trioxide in a small pilot-plant reactor.
SO2 and 100% excess air are fed to the reactor at 450°C. The reaction proceeds to a 65% SO2
conversion, and the products emerge from the reactor at 550°C. The production rate of SO3
is 1,00 X10^2 kg/min. The reactor is surrounded by a water jacket into which water at 25°C
is fed.
(a) Calculate the feed rates (standard cubic meters per second) of the SO2 and air feed
streams and the extent of reaction, ξ.
(b) Calculate the standard heat of the SO2 oxidation reaction, ΔH r (kJ). Then, taking molecular
species at 25°C as references, prepare and fill in an inlet–outlet enthalpy table and write
an energy balance to calculate the necessary rate of heat transfer (kW) from the
reactor to the cooling water.
(c) Calculate the minimum flow rate of the cooling water if its temperature rise is to be kept
below 15°C.
(d) Briefly state what would have been different in your calculations and results if you had
taken elemental species as references in Part (b)
100 kg/ min SO2
n SO2 (g), in
n SO2 (g), out
n SO3 (g), out
n O2 (g), out
100% excess air
n O2(g), in
n N2(g), in = 3,76n O2 (g), in
n N2(g), out = n N2(g), in
T
T
450 C
550
Diketahui
SO2 (g) + 1/2 O2 (g) = SO3 (g)
feed = SO2 dan 100 % excess air at 450 C
produk = 65% SO2 konversi, produks emerge at 550 C,
rate produk =
100 kg/min
basis =
100 kg/min SO3
Persamaan stoikiometri SO3
SO2 (g) + 1/2 O2 (g) = SO3 (g)
∆𝐻 = -98,28 Kj/mol
Menghitung komposisi SO3 di produk
mol SO3 (g), out =
=
100 kg/min SO3
x
1000
80,065
mol SO3
kg
1248,9852 mol/min SO3
Menghitung jumlah molar SO2 mempertimbangkan 65
(n SO2(g), in) x 1 mol SO3
=
1 mol SO2
n SO2(g), in =
Produksi dari SO3 =
Feed rate SO2 =
Feed rate O2 =
1248,9852
1924,112334 mol/min SO2
65%
102 kg/min
66,3 kg/min
66,3 kg/min
245,31
0,65
0,27027027
337,5635674
675,1271349
Menghitung molar O2 dari SO2 di feed gas
mol O2 (g), in =
1924,112334 mol/min SO2 X 1/2 mol O2
1 mol SO2
1924,112334 mol/min O2
Menghitung N2 jumlah inlet dari O2. molar ratio N2 dan O2 dalam gas
mol N2 (g), in =
7234,662377 mol/min N2
Menghitung SO2 yang tidak bereaksi di produk
mol SO2(g), out =
1924,112334 mol/min SO2 X 0,35
673,439317 mol/minSO2
Menghitung O balance untuk menentukan O2 di outlet gas
(2*n SO3(g) in) + (2*n O2(g),in) = (3*n SO3 (g), out) + (2*n SO2(g), out) + (2*n O2 (g), out)
2n O2, out =
7696,449338
5093,834233
2n O2, out =
2602,615105 mol/s
n O2, out =
1301,307552 mol/s
Menghitung untuk feed rate (standard m^3/s) dari SO2 dan udara
feed rate SO2 =
feed rate SO2 =
1921,52 𝑚𝑜𝑙/ min 𝑆𝑂2 𝑥
64,065𝑔 𝑆𝑂2
𝐿
𝑚^3
1 𝑚𝑖𝑛
𝑥
𝑥
𝑥
𝑚𝑜𝑙 𝑆𝑂2
2,62 𝑔 1000 𝐿
60𝑠
0,784149216
784,1492157 m^3/s
Menghitung feed dari udara
feed rate udara =
𝑚𝑜𝑙
100 𝑚𝑜𝑙 𝑢𝑑𝑎𝑟𝑎
28,84 𝑔
1 𝑘𝑔
1 𝑚^3
1 𝑚𝑖𝑛
1921,5
𝑋
𝑋
𝑋
𝑋
𝑋
min 𝑂2
21 𝑚𝑜𝑙 𝑂2
𝑚𝑜𝑙 𝑢𝑑𝑎𝑟𝑎 1000 𝑔 1,225 𝑘𝑔
60𝑠
feed rate udara =
3,595166811 m^3/s
inlet - outlet tabel entalpi SO2 (g), O2(g), SO3 (g), N2(g) at 25 C
No
1
2
3
4
Komponen
SO2 (g)
O2 (g)
N2 (g)
SO3 (g)
n in (mo/min)
H in (Kj/mol)
n out (mol/min)
H out (Kj/mol)
1924,112334
1924,112334
7234,662377
-
H1
H2
H3
-
673,439317
1301,307552
7234,662377
1248,9852
H4
H5
H6
H7
menghitung dHr dari heat formation produk dan reaktan tabel B.1
No
Komponen
Koefisien
1
2
4
SO2
O2
SO3
1
0,5
1
𝑘𝑗
∆𝐻𝑓° (
)
𝑚𝑜𝑙
-296,9
0
-395,18
Vi x ∆𝐻𝑓°
-296,9
0
-395,18
-98,28
kj
Menghitung nilai standar entalpi
No
1
2
3
Komponen
SO2 (g)
SO2(g)
SO3 (g)
interpolasi table B.8
T©
Tref ©
450
550
550
25
25
25
data cp
c
-3,104E-08
-3,104E-08
-8,54E-08
d
8,606E-12
8,606E-12
3,24E-11
data cp
a
0,03891
0,03891
0,0485
b
0,00003094
0,00003094
0,00009188
෡ = ‫𝑇𝑑 𝑃𝐶 𝑇׬‬
𝐻
𝑇𝑟𝑒𝑓
18,80530202
23,57336611
35,33613809
H1
H4
H7
No
Komponen
Interpolasi
1
2
3
4
O2
N2
O2
N2
-13,375
-12,695
16,72
15,815
H2
H3
H5
H6
menghitung dH reaktor
∆𝐻 = 𝜉 Δℎ𝑟 + Σ 𝑛 𝑜𝑢𝑡 𝐻 𝑜𝑢𝑡 − Σ 𝑛 𝑖𝑛 𝐻 𝑖𝑛
Δ𝐻 =
-7962,200364 KJ / min
Menghitung neraca energi
𝑄 + 𝑊 = ∆𝐻 + ∆𝐸𝐾 + ∆𝐸𝑃
W=
0 (tidak ada perpindahan)
∆𝐸𝐾=
0 (tidak ada perubahan energi kinetik)
∆𝐸𝑃=
0 (tidak ada perubahan ketinggian)
𝑄 = ∆𝐻
=
=
−8099,594554 𝑘𝑗/𝑚𝑖𝑛 x
1 𝑚𝑖𝑛
60 𝑠
𝑥
1 𝑘𝑊
1 𝑘𝑗/𝑠
-132,7033394 Kw
Minimum flowrate cooling water
𝑄 = ∆𝐻
𝑄 = ∆𝐻 = −8099,594554 𝑘𝑗/ min = 𝑚 𝐻2𝑂 𝑙 (𝐻𝑙, 40𝐶 − 𝐻𝑙, 25𝐶
Hl, 40C =
Hl, 25C =
m H2O (l) =
167,5 kj/kg
104,8 kj/kg
-126,9888415 kg/min
Jawaban bagian D
perbedaannya dapat diabaikan karena hanya jalur perhitungan yang diubah. jika spesies
unsur diambil sebagai referensi, panas pembentukan akan diperhitungkan selama
perhitungan entalpi spesifik. sedangkan pada metode yang diterapkan, panas pembentukan
diperhitungkan dalam penentuan panas reaksi.
c
konservasi O2 =
65%
mole dari konversi
SO2 = SO2 in - SO2 out x SO2 in
0,65 = SO2 in - SO2 out x SO2 in
0,35
0,65
in - SO2 out x SO2 in
in - SO2 out x SO2 in
awal jumlah mol untuk
SO2 =
1
O2 =
1
SO3 =
0
jadi jumlah mole =
setelah reaksi jumlah mol
2
SO2 =
O2 =
SO3 =
1-x
1-x
x
jadi jumlah mole =
1-x+1-x+x =
2-x