The Water Intensity of Ammonia

Agrium continues to plan for the potential restart of its ammonia-urea plant in Kenai, Alaska, with a draft water permit that is now entering a 30-day public comment period. As the local press reports:

Agrium’s Manager of Government Affairs, Adam Diamond, said the permit application is advance contingency planning rather than a committed preparation to resume operations.

“The restart has not been firmly decided,” Diamond said. “These permit applications take a long time to process … We’re planning for if there’s a decision to restart.”

However, the fact sheet for the draft permit contains one particularly interesting chart, which follows below, to illustrate the water flows throughout the ammonia-urea plant. In an industry that holds its data close, this is a refreshingly detailed flow chart.

Ammonia Water Intensity. Click to embiggen.
Ammonia Water Intensity. Click to embiggen.
Agrium’s flow chart allows me to calculate a few interesting data points.

It takes 2.3 tons of water to produce a ton of ammonia. However, 45% of that water is process condensate, which gets recycled within the system.

This water intensity data pertains specifically to Kenai’s Ammonia Plant #4, built in 1977 with a capacity of 2,250 stpd (2,040 mtpd), which required roughly 1.25 million gallons of water per day, based on Agrium’s engineering estimates during operations from 2002 to 2004 (and using a conversion rate of 264.17 US gallons per metric ton of water).

Ammonia-urea plant, water inflows. Click to embiggen.
Ammonia-urea plant, water inflows. Click to embiggen.
While there is considerable recycling of water in and around the ammonia-urea plant, a look at just the inflows and outflows give us a simple picture of the points of entry and exit of water within the system.

A subtle point for those interested in water intensity: while 17% of the water is consumed in the ammonia process, some of that water – 6% of the total – is recaptured as a byproduct during the urea process and counts as an inflow in the system.

Ammonia-urea plant, water outflows. Click to embiggen.
Ammonia-urea plant, water outflows. Click to embiggen.
While the ammonia water-intensity chart implies that only 6% of the water used in industrial ammonia production is discharged as effluent into the local waterways, this is misleading: part of the recycled process condensate also ends up as effluent, after cycling through systems including the urea plants and (urea) cooling towers.

Looking at the complete system, 32% of the water used by the plant is discharged as effluent. That’s more than the 28% vented as steam during the combined ammonia and urea processes, or the 21% evaporated in the cooling towers, or the 17% consumed in the ammonia process itself.

The full chart follows below, and can be found at the end of Agrium’s draft Permit Fact Sheet for its Alaska Pollutant Discharge Elimination System, from September 2016.

Agrium Kenai Nitrogen Operations Process Flow Diagram: Schematic of Water Flow. Source: draft permit fact sheet: Alaska Pollutant Discharge Elimination System, September 2016. Click to embiggen.
Agrium Kenai Nitrogen Operations Process Flow Diagram: Schematic of Water Flow. Source: draft permit fact sheet: Alaska Pollutant Discharge Elimination System, September 2016. Click to embiggen.

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