A look on the back of any plant nutrient or fertilizer product at the local agriculture supply retailer will reveal a curious set of numbers and dashes: 27-4-6. This number represents the percentage of total nitrogen, phosphate (a salt of phosphoric acid) and potash (potassium oxide), respectively, present in a particular product. In this case, the product is a bag of lawn food.
Agrium makes forms of the nitrogen that would be found in such a product. The two forms the Kenai facility makes are anhydrous (means "without water") ammonia and urea. These products are then shipped to and sold in such Pacific Rim countries as South Korea, Indonesia, Russia, China, Australia and New Zealand.
Anhydrous ammonia, a liquid fertilizer, is manufactured at two of Agrium's four Nikiski plants by combining the atmosphere's 78 percent nitrogen content with hydrogen derived from natural gas and water.
In the first step of the process, the natural gas is pumped into a set of converters where it is allowed to react with superheated steam over a catalyst. Inside the converters are rows of orange-hot pipes, at upward of 1,500 degrees Fahrenheit, through which the gas steam passes. At the bottom of the converters are millions of coin-sized, wheel-shaped catalysts that induce the chemical reaction that produces a hydrogen-rich gas.
Next, compressed air is added and carefully scaled back to provide the exact amount of nitrogen needed for the ammonia mix, followed by a series of processes to remove carbon monoxide and carbon dioxide. The remaining gas is high in nitrogen and hydrogen and is compressed and sent to a reactor vessel where the ammonia gas is synthesized.
The excess carbon dioxide is used in urea production.
The anhydrous ammonia is then liquefied and stored at a temperature of minus 28 degrees Fahren-heit.
It can be shipped in this form. Jim Senn, the plant operations superintendent, said the ammonia requires specialized equipment to convert the subzero liquid gas into a usable state.
"It's very hard to handle," he said. "But some people prefer anhydrous ammonia because it's higher in nitrogen than urea."
Senn said because some buyers don't have the technology necessary to process anhydrous ammonia, the Nikiski plant does that work on site, as needed.
"We can upgrade it into urea," he said. "It is easier to handle and ship."
Urea is a solid form of the ammonia, which is manufactured at through a reaction of ammonia with the carbon dioxide byproduct of the anhydrous ammonia process. The two substances are heated together under extreme at between 270 and 375 degrees Fahrenheit.
The result from this reaction is a molten urea solution concentrated to about 80 percent. The liquid is further concentrated and then passed through an evaporator to make a little dry, white droplets.
Billions of these droplets are passed through one of four 50-foot long, 14-foot diameter granulators, sitting sloped, all in a row inside one of two buildings at the complex's northernmost end. The droplets move down screws inside to pass over a screen, as the huge steel, sloped granulators slowly turn in a westward direction.
"That way, if something happens, they'll just roll on out to (Cook) Inlet," Senn said.
The screen siphons out a certain size of the granules, and the rest are returned to the top of the granulators to either collect more urea or be trimmed down to fit the precise mold before passing.
The urea is then collected into giant piles inside of one of two warehouses -- each capable of housing a football field -- before eventually being bulldozed over giant trapdoors in the floor and conveyor-belted to ships in Cook Inlet.
Anhydrous ammonia can be used to make fertilizer and urea is utilized to help enhance forest and lawn growth, as well as increasing the nutrients in cattle feed. Beyond agricultural uses, both forms of nitrogen have industrial applications including making paper, synthetic fibers, glues, refrigeration chemicals , waste treatment, rocket propellants, and household cleaners.
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