Enaex

Enaex's Prillex América plant in Mejillones, Chile — the world's largest ammonium nitrate production center at 850,000 tons annual capacity — relied on manual valves to regulate coolant water flow across its pump systems. Because manual valves offer no speed modulation, the motors driving those pumps ran continuously at full nominal speed, drawing a combined 1 MW of power around the clock. In energy-intensive chemical manufacturing, where energy costs directly affect the cost per ton produced, this inefficiency compounded across every production hour. The lack of precise flow control left the plant with no mechanism to modulate energy draw in response to actual process demand.

Enaex partnered with Rockwell Automation — a supplier the company had worked with since 1998 — to replace manual valve control with variable-frequency drives equipped with real-time motor feedback. Three Allen-Bradley PowerFlex 7000 medium voltage AC drives (4.16 kV, 1,000 hp each) were installed on the coolant water pump motors of Unit 3 (PANNA 3). The drives continuously monitor motor load and speed, adjusting output to match actual cooling demand rather than running at fixed nominal power. Implementation was deliberately scheduled around a planned one-month service shutdown of PANNA 3 in October 2012, keeping all other production units fully operational. Direct-to-Drive technology reduced the physical footprint of the new electrical room, lowering civil construction costs. Standardizing on Allen-Bradley drives aligned with existing plant equipment, simplifying maintenance and spare-parts management.

The upgrade delivered a 500 kW reduction in coolant system energy consumption — a 50% decrease from the 1 MW baseline — while maintaining identical coolant water flows throughout the production process. Actual measured savings exceeded initial project projections. Financially, the results were equally strong:

• Investment: US$1,207,000
• Net present value: US$2,472,000
• IRR: 59%
• Payback period: 1.7 years

Critically, the implementation caused zero production loss — not a single ton of ammonium nitrate output was disrupted. The company subsequently planned a follow-on VFD project targeting airflow control, reflecting confidence in the technology and the vendor relationship.

• Variable-frequency drives on large cooling pump systems can deliver 50% energy reductions without compromising process performance — the key is eliminating continuous full-load motor operation through demand-matched speed control.
• Scheduling VFD installations around planned maintenance shutdowns eliminates production impact; Enaex completed the full installation within a single one-month service window.
• Financial returns in chemical manufacturing can be compelling: a 1.7-year payback and 59% IRR are achievable in high-load pump applications where motors previously ran at nominal power continuously.
• Long-term vendor relationships accelerate custom engineering; Enaex's history with Rockwell Automation enabled a non-standard UPS control circuit solution that preserved equipment warranty.
• Successful first deployments typically reveal adjacent opportunities — plan for follow-on phases in related systems such as airflow or compressed air.