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Improving production and steam system efficiency is a top priority for Terra Nitrogen Company L.P., a major U.S. producer of nitrogen fertilizer products. Although Terra Nitrogen already had an active energy savings program in place, a Department of Energy Save Energy Now energy assessment was performed to identify additional energy savings opportunities. DOE energy expert Veerasamy Venkatesan of VGAEC Inc. worked with plant personnel to analyze the plant’s energy-consuming steam system.
Energy-efficient condensing turbines installed in Ammonia Plant No. 2 at Terra Nitrogen are reducing high-pressure steam demand and low-pressure venting.
Nitrogen fertilizer manufacturing captures naturally occurring nitrogen from the atmosphere and combines it with hydrogen from natural gas under heat and pressure to form anhydrous ammonia. Ammonia is then applied directly to crops as a nitrogen fertilizer and used as a building block to make other nitrogen fertilizer products, such as urea ammonium nitrate solution.
Each year, Terra Nitrogen’s manufacturing facility in Verdigris, Okla., produces 2.2 million tons of urea ammonium nitrate solution and 1.1 million tons of ammonia. The plant requires significant amounts of natural gas to produce hydrogen and fuel its steam systems, which provide critical support to the ammonia production processes. As a result, natural gas costs account for most of Terra Nitrogen’s total expenses — approximately $7 per MMBtu.
Software tools reveal energy-saving potential
“One of the most beneficial aspects of the assessment was that the DOE Energy Expert validated several existing projects so they could be justified and approved by management,” said Dallas Robinson, plant manager for Terra Nitrogen.
For example, before the energy assessment, Terra Nitrogen had installed a loop dehydrator in its Ammonia Plant No. 1. While plant management understood the potential for significant natural gas savings from this project, the analysis performed using DOE’s Steam System Assessment Tool (SSAT) confirmed the scale of potential energy savings resulting from not only installing a loop dehydrator, but also retrofitting a back-pressure turbine with a condensing turbine in Ammonia Plant No. 2.
In fact, analyzing the steam system proved to be so beneficial that it has become an area of focus for Terra Nitrogen’s maintenance plan.
“The SSAT pointed out the importance and cost savings of good steam trap maintenance,” said Robinson. “We took the next step by bringing in a steam trap manufacturer to train our mechanics and third party insulating contractors on proper installation, assessment and replacement techniques.”
From implementation to energy savings
Terra Nitrogen approved and successfully implemented five of the eight improvement projects revealed during the Save Energy Now assessment to save approximately $3.5 million and 497,000 MMBtu in natural gas annually, with a simple payback of 11 months.
“The Save Energy Now assessment process is valuable because it highlights and validates existing programs and uncovers potential blind spots (processes, equipment and cost evaluations) in energy losses and costs,” said Robinson. “The resulting energy savings were real and on target, and the savings were significant.”
Read more articles on these topics from the U.S. Department of Energy