No. 3 Nitric Acid Unit is Kellogg Technology. Capacity is 58,000 TPY, 170 TPD (100% acid basis)
56% Strength Nitric Acid is Produced.
It was designed by M.W. Kellogg. and has been upgraded from its original 150 tons/day capacity.
The plant uses a pelletized metallic oxide catalyst instead of platinum gauze for the oxidation process.
Plant is equipped with a fume abater for nox abatement. The fuel used in the fume abater is purged gas off of the ammonia plant.
The compressor section consists of an Allis-Chalmers compressor powered by a Terry 1500 HP steam turbine with a Worthington 3200 HP Expander
Designed by M. W. Kellogg with a capacity of 144TPSD (100% Acid). It was upgraded with a second cooler condenser and a fumabater being added. The converter was modified to use cobalt catalyst instead of platinum. Air was used off utility air compressors to do the bleaching allowing all the air from the compressor set to be used to make nitric acid. There is a discharge cooler added off the discharge of the compressor to lower the preheat temperature.
Compressor set consisted of steam turbine, gear box, Expander tail gas turbine and multistage compressor.
With the turbine running around 5000 RPM and compressor running 7895 RPM, the compressor pulls air through the suction filters and compresses it up to 125, then it passes through an air discharge cooler that cools the discharge from around 400° to about 300° which is what we use for preheating on our cobalt catalyst. The exchanger helps to heat up the tail gas before going to the tail gas preheater. The air then enters the mixer where ammonia is added to it then into the converter where the ammonia/air mixture reacts on the cobalt catalyst at 1500°F to make NO and NO2 as it passes through.
From the converter, it goes to the high-pressure boiler where some of the heat is removed to make 250# steam which is used to help drive the compressor set. Next the process gas passes through the tail gas preheater where some of the heat in the process gas heats the tail gas before it goes to fumabator.
After the tail gas heater the process gas goes through the platinum filter housing, since we use cobalt there are no filter media in the filter housing. From the platinum filter the flow goes to the low-pressure boiler which we use to make 50# steam. Then the process gas is divided to enter to two cooler condensers which cools the gas down and knocks out some weak acid.
The gas stream then enters the bottom of the primary absorber and flows up through the trays which have a liquid level of process acid flowing down through them getting stronger as it nears the bottom, there is bleaching air added to the bottom trays to help remove nitric oxides from the acid and convert nitric oxides into nitric dioxide, the process gas exits the top of the primary absorber then enters the bottom of the secondary absorber passing up through the trays counter current to the condensate that is absorbing the most of the remaining nitric oxides.
The tail gases that are left go to the compressor discharge cooler and tail gas preheater exiting at about 550°F. The gases that are left contain a small amount of nitric oxides which are broke down into nitrogen and water by being burned in the fumabator with purge gas from the ammonia plant. This heated tail gas enters the expander at 1200° F to help drive the compressor set then passes out the stack through a boiler feed water heater and a steam superheater, to the atmosphere. The product acid exit the bottom of the primary absorber at 56.5% and is sent to storage.
Bubbling nitrogen dioxide through hydrogen peroxide can help to improve acid yield.
2 NO2 + H2O2 → 2 HNO3
Commercial grade nitric acid solutions are usually between 52% and 68% nitric acid. Production of nitric acid is via the Ostwald process, named after German chemist Wilhelm Ostwald. In this process, anhydrous ammonia is oxidized to nitric oxide, in the presence of platinum or rhodium gauze catalyst at a high temperature of about 500 K and a pressure of 9 bar.
4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g) (ΔH = −905.2 kJ)
Nitric oxide is then reacted with oxygen in air to form nitrogen dioxide.
2 NO (g) + O2 (g) → 2 NO2 (g) (ΔH = −114 kJ/mol)
This is subsequently absorbed in water to form nitric acid and nitric oxide.
3 NO2 (g) + H2O (l) → 2 HNO3 (aq) + NO (g) (ΔH = −117 kJ/mol)
The nitric oxide is cycled back for reoxidation. Alternatively, if the last step is carried out in air:
4 NO2 (g) + O2 (g) + 2 H2O (l) → 4 HNO3 (aq)
The aqueous HNO3 obtained can be concentrated by distillation up to about 68% by mass. Further concentration to 98% can be achieved by dehydration with concentrated H2SO4. By using ammonia derived from the Haber process, the final product can be produced from nitrogen, hydrogen, and oxygen which are derived from air and natural gas as the sole feedstocks.
Prior to the introduction of the Haber process for the production of ammonia in 1913, nitric acid was produced using the Birkeland–Eyde process, also known as the arc process. This process is based upon the oxidation of atmospheric nitrogen by atmospheric oxygen to nitric oxide at very high temperatures. An electric arc was used to provide the high temperatures, and yields of up to 4% nitric oxide were obtained. The nitric oxide was cooled and oxidized by the remaining atmospheric oxygen to nitrogen dioxide, and this was subsequently absorbed in dilute nitric acid. The process was very energy intensive and was rapidly displaced by the Ostwald process once cheap ammonia became available.
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