REDWATER, AB, Canada, Jan. 9, 2006 -- Agrium Redwater Fertilizer Operations (RFO), located 45 kilometers northeast of Edmonton, Alberta, is the largest fertilizer complex in Canada and one of the largest in North America, with an annual ammonia production capacity of 960,000 tons and a total nitrogen product capacity of 1,400,000 tons.
Challenge
The Ammonia I unit at the RFO site was experiencing low production efficiency due to suspected calcium carbonate scale in the cooling system, resulting in poor heat transfer in the cooling exchangers.
The cooling system circulates water in an open loop between the process stream and the cooling exchangers. The heat from the process is released to the atmosphere in the form of water vapor at the cooling tower.
The efficiency of the cooling system is critical in anhydrous ammonia production because the process involves heating gasses to 1,400°F and then cooling the product down to -27°F.
Scale buildup in the cooling exchangers dramatically increases the cost of production in three ways. First, diminished efficiency of the cooling system reduces the ammonia production rate. Second, more energy is required to produce ammonia due to inefficient cooling in the unit. Third, manually removing of scale in the cooling exchangers (through pressure washing or acid cleaning) is a difficult and expensive process that requires a shutdown of the entire production process.
Solution
Jean Sabourin, the chief steam engineer at the RFO complex, turned to GE Infrastructure Water & Process Technologies (W&PT) to analyze the reduced efficiency of the cooling system and to recommend a solution.
"We contract with W&PT as our treatment consultant and chemical supplier for water treatment," says Sabourin. "We work closely with them, and we expect innovation and improvement not only in the efficiencies of chemical usage, but also in other ways, such as reducing our energy consumption."
A vendor analysis confirmed that the diminished performance of the heat exchangers was caused by buildup of calcium carbonate scale, a type of precipitation.
After evaluating the possibility of localized chemical cleaning of specific exchanger components, W&PT recommended the application of Ferroquest LP-7202 to the entire cooling circuit. This is a proprietary blend of three organic acids, specifically formulated to remove calcium carbonate scale from cooling systems.
Results
"Ferroquest has proven very successful in removing scale from the heat exchanger surfaces," according to Sabourin. "In a production run from July through October 2004, we increased our unit production and reduced our natural gas consumption by saved 114 million cubic feet of natural gas due to increased efficiency of the cooling system. This was equivalent to a reduction of our energy coefficient by 1.3 gigajoules per ton of ammonia produced."
During the production run after the introduction of the descalant, efficiency of the cooling system has remained constant, eliminating any production downtime for scale removal.
"We are very pleased with the results," says Sabourin. "The decreased energy consumption has not only produced a significant cost savings, but it also means that we require less natural gas, a limited natural resource, and we are therefore emitting less carbon dioxide, and nitrogen oxide, which is good for the environment."
GE Infrastructure Water & Process Technologies (www.gewater.com), a unit of General Electric, is an industry leader in solving the world's most pressing water reuse, industrial, irrigation, municipal, and drinking water needs. Through desalination, advanced membrane, separation solutions, and water reuse and wastewater management and process technologies, GE seeks to improve performance and product quality, reducing operating costs, and extending equipment life through a broad range of products and services designed to optimize total performance; protect customers' assets; prevent fouling and scaling; and safeguard the environment through water conservation and energy reduction.
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