Spencer Chemical's new plant at Vicksburg is designed to produce 210 tons of anhydrous ammonia, 110 tons of nitric acid, 140 tons of ammonium nitrate solution, and 350 tons of ammoniating solutions daily
Flow diagram of Spencer's Vicksburg plant shows processes for making four prod ucts starting from air and methane
Ammonia Plant on Sfrea First partial oxidation process now in operation producing 9 9 . 9 9 % anhydrous ammonia at Spencer Chemical's Vicksburg plant ^RAHlWAY|
o w in the middle of a shakedown
Ν run, the Vicksburg Works of Spen cer Chemical officially opened there on
F e b . 2. Arrangement and compactness of the facilities, and t h e degree of out door construction, make this plant unique in the ammonia industry. N e w designs, extensive instrumenta tion, both permit only eight operators per shift to control the highly inte grated process easily. Company presi dent Kenneth Spencer says, "The operating force is about one third the size required for a conventional plant of equal capacity/* Spencer Chemical has simplified much of the process for improved efficiency. Vicksburg Works, although built with deflated dollars, should still b e highly competitive with efficient plants built or acquired at other locations during the past 10 years. Original construction estimates for 572
the plant amounted to $ 14 million, b u t Spencer executives say the unit w a s completed for less than this figure. Process facilities include equipment to manufacture 210 tons of anhydrous ammonia, 110 tons of 6 0 % nitric acid, 140 tons of neutral*84% ammonium nitrate solution, a n d 350 tons of ammoniating solutions per day. Storage capacity at the plant will accommodate 2700 tons of anhydrous ammonia a n d 15,000 tons of nitrate solution. At least 509Ό of the nitrogen prod ucts manufactured at Vicksburg will go to agricultural consumers; t h e rest will be used by industry east of t h e Mississippi and south of the Ohio River. The entire operations are divided into seven different phases: air separa tion, hydrogen production, hydrogen purification, ammonia synthesis, nitric acid production, ammonium nitrate p r o CHEMICAL
ΜΜ^™φ&^
duction, and the manufacture of ammoniating solutions. Air to Ammonia. In the partial oxi dation process, Spencer liquefies about 25 million cubic feet ( 1 0 0 0 tons) of air per day. Liquid air is fractionated into nitrogen and oxygen for ammonia synthesis—natural gas is the only other raw material for t h e operation. As a special feature of the process, a centrif ugal pump removes liquid oxygen from the distillation tower so that it c a n b e vaporized in heat exchange with inlet air. Hydrogen for the ammonia synthesis is produced by controlled burning of methane with oxygen in especially de signed generators. Gases leaving these vessels contain high concentrations of hydrogen and carbon monoxide, which are cooled by direct water scrubbing. From here they pass through a shift AND
ENGINEERING
NEWS
Interior of ammonia synthesis plant contains control panel, circulator valves, and one of four 2000-hp. compressors
converter containing a n iron oxide catalyst—this increases the hydrogen yield a n d produces carbon dioxide. To purify the hydrogen it is first scrubbed directly 'with monoethanolamine solution where most of the carbon dioxide is removed. A caustic wash, followed b y scrubbing with liquid nitrogen, removes all traces of methane and carbon dioxide—only 10 p.p.m. of carbon monoxide remain in the gases. During this washing process, pure nitrogen evaporates and is carried out with the hydrogen in concentrations of approximately 10%. Additional pure nitrogen is added to this gas stream for the ammonia synthesis a t a pressure of 3600 pounds per square inch. Here t h e mixture passes through a converter containing an iron catalyst. After separation of the liquid ammonia by refrigeration using VOLUME
3 2,
NO.
7
Natural gas preheaters and hydrogen generators form carbon monoxide and hydrogen by the partial combustion of methane
Freon, the unreacted gases are recirculated through the converter by a German-made centrifugal compressor. This compressor, requiring practically no oil, makes it possible to produce a product with no oil contamination. Nitrogen Products. Nitric acid is manufactured by burning ammonia with air in the presence of a platinum rhodium catalyst. Resulting nitrogen dioxide is absorbed in water under pressure. Ammonia for this reaction is transferred from the ammonia plant as a liquid and is vaporized with steam. Nitrogen, excess oxygen, and small quantity of unabsorbed nitrogen dioxide leaving the absorption tower are vented to the atmosphere. Ammonium nitrate solution is produced by mixing liquid ammonia with 60% nitric acid. Ammonia for this operation is transferred from the ammonia
» » FEBRUARY
15,
1954
plant; flow is controlled automatically to give a resulting neutral solution t h a t is 8 4 % ammonium nitrate. By blending liquid ammonia, ammonium nitrate solution, and water in the proper proportions, high nitrogen solutions can b e manufactured of various concentrations. This product goes directly to tank cars for shipment to fertilizer mixing plants. Asked why Vicksburg was selected for the plant site, Kenneth Spencer said there were several reasons for t h e choice. In general, it is located reasonably close to the anticipated markets in the Mid-South and the Southeast. Most important, however, was a spot which has lower freight rates—east of the Mississippi River—not too distant from the supply of natural gas. Following the general company pattern, operations at Vicksburg are nonunion. 573
