- A plant produces 1296 kg/hr of 60% nitric acid from ammonia and air. - Ammonia is vaporized using warm water and then superheated using steam before mixing with compressed air in a reactor. - The reactor feed air is compressed in two stages with intercooling and mixes with superheated ammonia in a feed mixer before the reactor. - In the reactor, ammonia oxidizes over a catalyst to produce nitrogen monoxide and water which exit along with unreacted air components. - A small amount of nitrogen monoxide is further oxidized to nitrogen dioxide in a steam superheater downstream of the reactor.

1. Material Balance
Specification: Plant producing 1296 kg/hr of 60% wt. nitric acid.
Basis: 100% acid and hourly production.
𝑀 = 1296 × 0.6 = 778 𝑘𝑔/ℎ𝑟 (kg of 100% acid per hour).
Ammonia feed: 0.2866 kg/kg 100% nitric acid (Sperner & Hohmann, 1976).
𝐴𝑚𝑚𝑜𝑛𝑖𝑎 𝑓𝑙𝑜𝑤𝑟𝑎𝑡𝑒 (𝐹𝐴𝑚𝑚) = 0.2866 × 778 = 223 𝑘𝑔
Basis: 1 hr
Air flowrate
5.15 kg air per kg 100% acid (82.5% reactor feed and 17.5% secondary air for product
bleaching) (Ray, 2020).
𝐹𝑎𝑖𝑟 = 5.15 × 778 = 4007
Ammonia Vaporizer
The ammonia vaporizer receives liquid ammonia from the adjacent plant at - 15°C and 1240 kPa
and vaporizes it at 35°C using warm water.
Enthalpy of ammonia at 1240 kPa:
𝐻−15 ℃ = −850
𝑘𝐽
𝑘𝑔
𝐻35 ℃ = 525
𝑘𝐽
𝑘𝑔
𝐻𝑒𝑎𝑡 𝑑𝑢𝑡𝑦 𝑡𝑜 𝑣𝑎𝑝𝑜𝑟𝑖𝑧𝑒 𝑎𝑚𝑚𝑜𝑛𝑖𝑎 = (𝐻𝑜𝑢𝑡 − 𝐻𝑖𝑛) × 𝐹𝐴𝑚𝑚
𝐻𝑒𝑎𝑡 𝑑𝑢𝑡𝑦 𝑡𝑜 𝑣𝑎𝑝𝑜𝑟𝑖𝑧𝑒 𝑎𝑚𝑚𝑜𝑛𝑖𝑎 = (525 − (−850)) × 223 = 306625 𝑘𝐽
𝐻𝑒𝑎𝑡 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 𝑓𝑜𝑟 𝑤𝑎𝑡𝑒𝑟 = 4.1
𝑘𝐽
𝑘𝑔. 𝐾
Required circulation rate from the warm-water loop:
𝐹𝑤𝑤 = 𝐻𝑒𝑎𝑡 𝑑𝑢𝑡𝑦/[𝐶𝑝(𝑇𝑖𝑛 − 𝑇𝑜𝑢𝑡)]
𝐹𝑤𝑤 = 306625/[4.2 (80 − 50)]
𝐹𝑤𝑤 = 2434 𝑘𝑔

2. Input = Output
Liquid Ammonia + Warm Water = Saturated Ammonia + Warm Water
223 + 2434 = 223 + 2434
2657 kg = 2657 kg
Ammonia Superheater
The ammonia superheater takes the saturated ammonia vapor at 35°C and superheats it to 177°C
for mixing with air downstream. Superheated steam at 380°C and 4000 kPa is the heating medium.
Average heat capacity for ammonia vapor in the range 35°C to 177°C is 2.25 kJ/(kg K).
𝐻𝑒𝑎𝑡 𝑑𝑢𝑡𝑦 𝑡𝑜 𝑠𝑢𝑝𝑒𝑟ℎ𝑒𝑎𝑡 𝑎𝑚𝑚𝑜𝑛𝑖𝑎 = 𝐹𝐴𝑚𝑚 × 𝐶𝑝(𝑇𝑜𝑢𝑡 − 𝑇𝑖𝑛)
= 223 × 2.25(177 − 35)
= 71249 𝑘𝐽
Enthalpy of superheated steam vapor at 4000 kPa:
𝐻380 ℃ = 3165
𝑘𝐽
𝑘𝑔
𝐻250 ℃ = 2800
𝑘𝐽
𝑘𝑔
Heat of condensation at 250°C and 4 000 kPa: 1714 kJ/kg
𝑆𝑡𝑒𝑎𝑚 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡𝑠 = 𝐻𝑒𝑎𝑡 𝑑𝑢𝑡𝑦 /[∆𝐻𝑐𝑜𝑛𝑑 + (𝐻380 ℃ − 𝐻250 ℃)]
𝑆𝑡𝑒𝑎𝑚 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑚𝑒𝑛𝑡𝑠 =
71249
1714 + (3165 − 2800)
= 34.3 𝑘𝑔

3. Input = Output
Saturated Ammonia + Superheated Steam = Superheated Ammonia + Condensed Steam
223 + 34.3 = 223 + 34.3
257.3 kg = 257.3 kg
Air Compressor
To supply air for the process, a two-stage compressor with an intercooler is employed. A total of
4007 kg of air are needed. Using an axial compressor, stage one involves low-pressure
compression. It compresses the air input to 180°C and 310 kPa from around 35°C. A centrifugal
compressor is used in the high-pressure second stage of compression. At 45°C and 300 kPa, it
draws air from the intercooler, which it then releases at 232°C and 1090 kPa. The theoretical power
for total compression is given by formula.
𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 = 𝑃1𝑄1𝑙𝑛 (
𝑃2
𝑃1
)
𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 = 𝑃1
𝐹𝑎𝑖𝑟
𝜌
𝑙𝑛 (
𝑃2
𝑃1
)
𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 = 99 × (
4007
1.178
) 𝑙𝑛 (
1090
99
)
𝑇ℎ𝑒𝑜𝑟𝑒𝑡𝑖𝑐𝑎𝑙 𝑃𝑜𝑤𝑒𝑟 = 807803 𝑘𝐽
Assuming efficiency of compressor is 65 % (Ray, 2020)
𝐴𝑐𝑡𝑢𝑎𝑙 𝑠ℎ𝑎𝑓𝑡 𝑝𝑜𝑤𝑒𝑟 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑 =
807803
0.65
= 1242774 𝑘𝐽

4. 𝐼𝑛𝑡𝑒𝑟𝑐𝑜𝑜𝑙𝑒𝑟 𝐻𝑒𝑎𝑡 𝐷𝑢𝑡𝑦 = 𝐹𝑎𝑖𝑟 × 𝐶𝑝(𝑇𝑖𝑛 − 𝑇𝑜𝑢𝑡)
𝐼𝑛𝑡𝑒𝑟𝑐𝑜𝑜𝑙𝑒𝑟 𝐻𝑒𝑎𝑡 𝐷𝑢𝑡𝑦 = 4007 × 1.05(180 − 45) = 567992 𝑘𝐽
Cooling Water Flowrate
𝐹𝑐𝑤 = 𝐻𝑒𝑎𝑡 𝑑𝑢𝑡𝑦/[𝐶𝑝(𝑇𝑜𝑢𝑡 − 𝑇𝑖𝑛)]
𝐹𝑐𝑤 =
567992
4.2 (40 − 20)
= 6762 𝑘𝑔
Process Air
𝑃𝑟𝑜𝑐𝑒𝑠𝑠 𝑎𝑖𝑟 = 4007 𝑘𝑔
Bleaching Air Out from Compressor
𝐵𝑙𝑒𝑒𝑐ℎ𝑖𝑛𝑔 𝐴𝑖𝑟 = 4007 × 0.175 = 701 𝑘𝑔
Reactor Feed Air
𝑅𝑒𝑎𝑐𝑡𝑜𝑟 𝐹𝑒𝑒𝑑 𝐴𝑖𝑟 = 4007 × 0.825 = 3306 𝑘𝑔
Input = Output
Cooling Water + Process Air = Cooling Water + Reactor Feed Air + Bleaching Air
6762 + 4007 = 6762 + 3306 +701
10769 kg = 10769 kg

5. Reactor Feed Mixer
Flowrate In
𝑆𝑢𝑝𝑒𝑟ℎ𝑒𝑎𝑡𝑒𝑑 𝐴𝑚𝑚𝑜𝑛𝑖𝑎 = 223 𝑘𝑔
𝑅𝑒𝑎𝑐𝑡𝑜𝑟 𝐹𝑒𝑒𝑑 𝐴𝑖𝑟 = 3306 𝑘𝑔
Input = Output
Ammonia + Reactor Feed Air = Ammonia + Air
223 + 3306 = 223 + 3306
3529 kg = 3529 kg
Reactor
Reactor Feed
Component Weight %
Ammonia 223 6.3
Air 3306 93.7
Total Flowrate In = 3529
Air Composition
Nitrogen
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
0.7491 × 3306
3529
= 70.2 %
Oxygen
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
0.227 × 3306
3529
= 21.3 %
Inert
% 𝐼𝑛𝑒𝑟𝑡 =
0.012 × 3306
3529
= 1.12 %

6. Water
% 𝑊𝑎𝑡𝑒𝑟 =
0.0119 × 3306
3529
= 1.11 %
With a 95% yield, the feed mixture oxidizes over the platinum catalyst, turning the ammonia into nitrogen monoxide
(NO). Since the remaining 5% produces nitrogen gas, it basically doesn't react with any of the following process
units.
Reactions
4𝑁𝐻3 + 5𝑂2 ↔ 4𝑁𝑂 + 6𝐻2𝑂
4𝑁𝐻3 + 3𝑂2 ↔ 3𝑁2 + 6𝐻2𝑂
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 = 𝑛𝑖𝑡𝑟𝑜𝑔𝑒𝑛 𝑖𝑛 𝑎𝑖𝑟 + 𝑛𝑖𝑡𝑟𝑜𝑔𝑒𝑛 𝑓𝑟𝑜𝑚 𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 = 0.7491 × 3306 + [0.05 (
223
17
) × 14]
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 = 2486 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝐼𝑛𝑒𝑟𝑡 = 0.012 × 3529 = 42 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 𝑀𝑜𝑛𝑜𝑥𝑖𝑑𝑒 (𝑁𝑂) = 0.95 ×
223
17
× 30 = 374 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑊𝑎𝑡𝑒𝑟 = 𝑤𝑎𝑡𝑒𝑟 𝑖𝑛 𝑎𝑖𝑟 + 𝑤𝑎𝑡𝑒𝑟 𝑓𝑟𝑜𝑚 𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑊𝑎𝑡𝑒𝑟 = 0.0119 × 3306 + [0.95 × (
3×223
17
) × (
18
2
)] = 376 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑂𝑥𝑦𝑔𝑒𝑛 𝑏𝑦 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 3529 − (2486 + 42 + 374 + 376) = 251 𝑘𝑔
Reactor Mixture
% 𝐴𝑚𝑚𝑜𝑛𝑖𝑎 = 0 %
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
2486
3529
× 100 = 70.4 %
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
251
3529
× 100 = 7.1 %
% 𝐼𝑛𝑒𝑟𝑡 =
42
3529
× 100 = 1.2 %
% 𝑊𝑎𝑡𝑒𝑟 =
376
3529
× 100 = 10.7 %
% 𝑁𝑂 =
374
3529
× 100 = 10.6 %

7. Input = Output
3529 kg =3529 kg
Steam Superheater
About 5% of the NO interacts with oxygen in the superheater to produce NO2. At this point, no nitrogen tetroxide is
created. The components of water, inert gas, and nitrogen don't alter.
2𝑁𝑂 + 𝑂2 ↔ 2𝑁𝑂2
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂 = 0.95 × 374 = 355 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂2 = 0.05 ×
374
30
× 46 = 29 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑂𝑥𝑦𝑔𝑒𝑛 𝑏𝑦 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 3529 − (2486 + 42 + 376 + 355 + 29) = 241 𝑘𝑔
Superheater exit gas mixture:
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
2486
3529
× 100 = 70.4 %
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
241
3529
× 100 = 6.8 %
% 𝐼𝑛𝑒𝑟𝑡 =
42
3529
× 100 = 1.2 %
% 𝑊𝑎𝑡𝑒𝑟 =
376
3529
× 100 = 10.7 %
% 𝑁𝑂 =
355
3529
× 100 = 10.1 %
% 𝑁𝑂2 =
29
3529
× 100 = 0.8 %
The reaction-gas temperature is intended to be lowered from 645°C to 280°C in the steam production section, which
consists of the waste-heat boiler and steam superheater (additional oxidation in these vessels will also continue to
create reaction heat). Enough steam must be generated to be sent to the nearby ammonia and ammonium nitrate
factories. The ideal steam temperature is 380°C and 4000 kPa, or medium pressure. In this temperature range, the
reaction gases have an average heat capacity of 1.I 9 kJ/(kg K). The sensible heat is 0.143 times that of reaction heat.

8. 𝐸𝑛𝑒𝑟𝑔𝑦 𝑓𝑜𝑟 𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 = 𝑆𝑒𝑛𝑠𝑖𝑏𝑙𝑒 ℎ𝑒𝑎𝑡 + 𝑅𝑒𝑎𝑐𝑡𝑖𝑜𝑛 ℎ𝑒𝑎𝑡
𝐸𝑛𝑒𝑟𝑔𝑦 𝑓𝑜𝑟 𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 = 𝑆𝑒𝑛𝑠𝑖𝑏𝑙𝑒 ℎ𝑒𝑎𝑡 + 0.143 (𝑠𝑒𝑛𝑠𝑖𝑏𝑙𝑒 ℎ𝑒𝑎𝑡)
𝐸𝑛𝑒𝑟𝑔𝑦 𝑓𝑜𝑟 𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 = 1.143 (𝑆𝑒𝑛𝑠𝑖𝑏𝑙𝑒 ℎ𝑒𝑎𝑡)
𝐸𝑛𝑒𝑟𝑔𝑦 𝑓𝑜𝑟 𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 = 1.143 × 𝐹𝑡𝑜𝑡 × 𝐶𝑝 × (𝑇𝑜𝑢𝑡 − 𝑇𝑖𝑛)
𝐸𝑛𝑒𝑟𝑔𝑦 𝑓𝑜𝑟 𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 = 1.143 × 3529 × 1.19 × (645 − 280)
𝐸𝑛𝑒𝑟𝑔𝑦 𝑓𝑜𝑟 𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 = 1752015 𝑘𝐽
The steam generation circuit receives the high-pressure boiler feed water that has been warmed to 96°C.
𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 =
𝐻𝑒𝑎𝑡 𝑎𝑣𝑎𝑖𝑙𝑎𝑏𝑙𝑒
[(𝐻380 − 𝐻250) + ∆𝐻 + 𝐶𝑝(250 − 𝑇𝑖𝑛)]
𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 =
1752015
[(3165 − 2800) + 1714 + 4.2(250 − 96)]
𝑠𝑡𝑒𝑎𝑚 𝑟𝑎𝑖𝑠𝑖𝑛𝑔 𝑐𝑎𝑝𝑎𝑐𝑖𝑡𝑦 = 643 𝑘𝑔
Input = Output
Reaction gases + Steam = Reaction gases + Steam
3529 + 643 = 3529 + 643
4172 = 4172
Waste-heat Boiler
As the reaction gas mixture's temperature drops, the equilibrium keeps changing. In the end, 15% more NO is
converted to nitrogen dioxide, and 3% of that NO2 is further converted to nitrogen tetroxide.
Reactions

9. 2𝑁𝑂 + 𝑂2 ↔ 2𝑁𝑂2
2𝑁𝑂2 ↔ 𝑁2𝑂4
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂 = 0.85 × 355 = 302 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂2 = 0.97 × [29 + (0.05 ×
355
30
× 46)] = 54 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁2𝑂4 = 0.03 × (
54
46
) × (
92
2
) = 2 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑂𝑥𝑦𝑔𝑒𝑛 𝑏𝑦 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 3529 − (2486 + 42 + 376 + 302 + 55 + 2) = 266 𝑘𝑔
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
2486
3529
× 100 = 70.4 %
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
266
3529
× 100 = 7.5 %
% 𝐼𝑛𝑒𝑟𝑡 =
42
3529
× 100 = 1.2 %
% 𝑊𝑎𝑡𝑒𝑟 =
376
3529
× 100 = 10.7 %
% 𝑁𝑂 =
302
3529
× 100 = 8.6 %
% 𝑁𝑂2 =
54
3529
× 100 = 1.5 %
% 𝑁2𝑂4 =
2
3529
× 100 = 0.1
Input = Output
Reaction gases = Reaction gases
3529 = 3529

10. Platinum Filter
The platinum filter is essentially a net made of gold and palladium alloy that collects platinum
particles that are transported by the reaction gases from the reactor catalyst gauze. The platinum
and gold/palladium combine to produce a complex, which is how the filter functions. The reaction
proceeds in this unit even when there is no heat transfer, changing the reaction gases' composition
and increasing their temperature. Only around 3 percent of NO can be further oxidized to NO2 due
to the short residence period in the filter. Following this, 0.4% of the nitrogen dioxide oxidizes to
N2O2.
Reactions
2𝑁𝑂 + 𝑂2 ↔ 2𝑁𝑂2
2𝑁𝑂2 ↔ 𝑁2𝑂4
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂 = 0.97 × 302 = 293 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂2 = 0.996 × [54 + (0.05 ×
302
30
× 46)] = 77 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁2𝑂4 = 54 + [0.004 ×
77
46
×
92
2
] = 54 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑂𝑥𝑦𝑔𝑒𝑛 𝑏𝑦 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 3529 − (2486 + 42 + 376 + 293 + 77 + 54) = 201 𝑘𝑔
Platinum gas exit mixture
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
2486
3529
× 100 = 70.4 %
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
201
3529
× 100 = 5.7 %
% 𝐼𝑛𝑒𝑟𝑡 =
42
3529
× 100 = 1.2 %
% 𝑊𝑎𝑡𝑒𝑟 =
376
3529
× 100 = 10.7 %
% 𝑁𝑂 =
293
3529
× 100 = 8.3 %
% 𝑁𝑂2 =
77
3529
× 100 = 2.2 %
% 𝑁2𝑂4 =
54
3529
× 100 = 1.5 %

11. Input = Output
Reaction gases = Reaction gases
3529 = 3529
Tail-gas Preheater
The second step in the tail-gas preheat process is the tail-gas preheater. The tail gas is heated using sensible heat and
reaction heat from the process reaction gases (ultimately for expansion). The tail-gas preheater is also where the
oxidation process takes place. A significant change in equilibrium occurs in favor of NO2 and N2O4, with 25% of the
residual NO becoming NO2 and 7% of the NO2 forming N2O4.
Reactions
2𝑁𝑂 + 𝑂2 ↔ 2𝑁𝑂2
2𝑁𝑂2 ↔ 𝑁2𝑂4
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂 = 0.75 × 293 = 222 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂2 = 0.93 × [54 + (0.05 ×
293
30
× 46)] = 71 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁2𝑂4 = 54 + [0.07 ×
71
46
×
92
2
] = 59 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑂𝑥𝑦𝑔𝑒𝑛 𝑏𝑦 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 3529 − (2486 + 42 + 376 + 222 + 71 + 59) = 273 𝑘𝑔
Platinum filter exit-gas mixture
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
2486
3529
× 100 = 70.4 %
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
273
3529
× 100 = 7.7 %
% 𝐼𝑛𝑒𝑟𝑡 =
42
3529
× 100 = 1.2 %
% 𝑊𝑎𝑡𝑒𝑟 =
376
3529
× 100 = 10.7 %

12. % 𝑁𝑂 =
222
3529
× 100 = 6.3 %
% 𝑁𝑂2 =
71
3529
× 100 = 2 %
% 𝑁2𝑂4 =
59
3529
× 100 = 1.7 %
Input = Output
Reaction gases = Reaction gases
3529 = 3529
Cooler/Condenser
The gases that exit the cooler/condenser and go to the oxidation unit are the subject of another design specification
for this unit. Of the NO, 43% has reacted to generate NO2, and 20% has dimerized to form N2O4.
Reactions
2𝑁𝑂 + 𝑂2 ↔ 2𝑁𝑂2
2𝑁𝑂2 ↔ 𝑁2𝑂4
3𝑁𝑂2 + 𝐻2𝑂 ↔ 2𝐻𝑁𝑂3 + 𝑁𝑂
4𝑁𝑂 + 3𝑂2+ 2𝐻2𝑂 ↔ 4𝐻𝑁𝑂3
4𝑁𝑂 + 𝑂2+ 2𝐻2𝑂 ↔ 4𝐻𝑁𝑂3
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂 = 0.57 × 222 = 127 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂2 = 0.80 × [54 + (0.05 ×
222
30
× 46)] = 57 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁2𝑂4 = 54 + [0.20 ×
57
46
×
92
2
] = 65 𝑘𝑔

13. 𝑀𝑎𝑠𝑠 𝑜𝑓 𝐻𝑁𝑂3 (𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛 3) = 0.80 ×
2 × 63
3 × 46
× 57 = 42 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝐻𝑁𝑂3 (𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛 4) = 0.57 ×
63
46
× 222 = 173 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝐻𝑁𝑂3 (𝑟𝑒𝑎𝑐𝑡𝑖𝑜𝑛 5) = 0.57 ×
63
46
× 222 = 173 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂2 𝑙𝑒𝑓𝑡 = 57 − 0.80 × 57 = 11 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂 𝑙𝑒𝑓𝑡 =
1 × 30
3 × 46
× 57 = 13 𝑘𝑔
Total Mass of HNO3 produced = 42 + 173 +173 = 388 kg. Water is consumed in reaction to HNO3. Thus, the
reaction mixture is depleted to 2765 kg as a result of nitric acid removal.
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑂𝑥𝑦𝑔𝑒𝑛 𝑏𝑦 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 2765 − (2486 + 42 + 13 + 11 + 65) = 148 𝑘𝑔
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
2486
2765
× 100 = 89.9 %
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
148
2765
× 100 = 5.3 %
% 𝐼𝑛𝑒𝑟𝑡 =
42
2765
× 100 = 1.5 %
% 𝑁𝑂 =
13
2765
× 100 = 0.5 %
% 𝑁𝑂2 =
11
2765
× 100 = 0.4 %
% 𝑁2𝑂4 =
65
2765
× 100 = 2.4 %
Input = Output
Reaction gas mixture = Reaction gas mixture + nitric acid

14. 3529 = 2765 +764
3529 kg = 3529 kg
Oxidation Unit
After exiting the cooler/condenser, the reaction gas combination enters the oxygenation unit
where it combines with the secondary air stream (bleaching air), which includes 460 kg of N2O4.
So total gas mixture out = 2765+1161 = 3926 kg
2𝑁𝑂 + 𝑂2 ↔ 2𝑁𝑂2
2𝑁𝑂2 ↔ 𝑁2𝑂4
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂2 =
2 × 46
92
× 525 = 525 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂 =
30
46
× 525 = 342 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁2𝑂4 = 525 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑂2 = 91 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑛𝑖𝑡𝑟𝑜𝑔𝑒𝑛 𝑏𝑦 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 3926 − (525 + 342 + 525 + 91 + 42) = 2401 𝑘𝑔
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
2401
3926
× 100 = 61.2 %
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
91
3926
× 100 = 2.3 %
% 𝐼𝑛𝑒𝑟𝑡 =
42
3926
× 100 = 1.0 %
% 𝑁𝑂 =
342
3926
× 100 = 8.7 %
% 𝑁𝑂2 =
525
3926
× 100 = 13.4 %
% 𝑁2𝑂4 =
525
3926
× 100 = 13.4 %

15. Absorber
Reactions
2𝑁𝑂 + 𝑂2 ↔ 2𝑁𝑂2
2𝑁𝑂2 ↔ 𝑁2𝑂4
3𝑁𝑂2 + 𝐻2𝑂 ↔ 2𝐻𝑁𝑂3 + 𝑁𝑂
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂2 =
46
30
× 13 = 20 𝑘𝑔
(from reaction equations)
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁2𝑂4 𝑖𝑛 𝑟𝑒𝑑 𝑝𝑜𝑟𝑜𝑑𝑢𝑐𝑡 𝑎𝑐𝑖𝑑 =
92
2 × 20
= 2 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁2𝑂4 = 65 − 3 = 62
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑁𝑂 = 309 𝑘𝑔
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑜𝑥𝑦𝑔𝑒𝑛 = 7 𝑘𝑔
Since the plant produces 1296 kg/hr of 60% wt. nitric acid.
Reaction gas mixture = 3926 - 1296 - 2= 2628 kg
𝑀𝑎𝑠𝑠 𝑜𝑓 𝑛𝑖𝑡𝑟𝑜𝑔𝑒𝑛 𝑏𝑦 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒 = 2628 − (309 + 62 + 20 + 7 + 42) = 2188 𝑘𝑔
% 𝑁𝑖𝑡𝑟𝑜𝑔𝑒𝑛 =
2188
2628
× 100 = 83.2 %
% 𝑂𝑥𝑦𝑔𝑒𝑛 =
7
2628
× 100 = 0.3 %
% 𝐼𝑛𝑒𝑟𝑡 =
42
2628
× 100 = 1.6 %

16. % 𝑁𝑂 =
309
2628
× 100 = 11.8 %
% 𝑁𝑂2 =
20
2628
× 100 = 0.7 %
% 𝑁2𝑂4 =
63
2628
× 100 = 2.4 %
Input = Output
Reaction gas Mixture = Reaction gas mixture + red product acid
3926 = 2628 +1298
3926 kg = 3926 kg
Bleaching Column
Bleaching air = 701 kg
Red product acid = nitric acid + N2O4 = 1296 + 2 = 1298 kg
Since product contains 60 wt % nitric acid = 1296 × 0.6 = 778 kg

17. Mass of water = 1296 – 778 = 518 kg
Input = Output
Red product acid + bleaching air = Product acid + bleaching air
1298 + 701 = 1296 + 703
1999 kg = 1999 kg
Overall Material Balance
Input = Output
Ammonia + Air = Product acid + Reaction gases + N2O4 (in red product acid)
4230 = 1296 + 2928 + 2
4230 kg = 4226 kg
% Error
4230 − 4226
4230
× 100 = 0.09 %
The error is negligible. The overall material balance has almost equal input and output, therefore,
the material balance is considered to be accurate with assumptions.

18. Block Diagram
References
Ray, M. S. (2020). Chemical engineering design project: a case study approach: CRC Press.
Sperner, F., & Hohmann, W. (1976). Rhodium-platinum gauzes for ammonia oxidation. Platinum Metals
Review, 20(1), 12-20.