Plant-Wide Assessment at Houston Refinery Results in Comprehensive Energy Management Strategy
August 30, 2005
A recent plant-wide energy assessment at Valero Energy Corporation's refinery in Houston, Texas, is helping Valero optimize the plant's entire energy production system while reducing energy costs and environmental emissions. The refinery produces about 60,000 barrels of gasoline and 35,000 barrels of distillates per day.
The assessment team estimated that carrying out all the projects they identified could result in total annual energy savings of about 1.3 million MMBtu for fuel and more than 5 million kWh for electricity. These reductions in turn would generate cost savings of about $5 million per year.
First, the team conducted an energy systems review to identify primary natural gas and refinery fuel gas users, electricity- and steam-producing equipment, and cooling water systems. Then, they developed an energy optimization and management strategy and identified ways to reduce water use and emissions.
More than a dozen projects were identified. For one of them, the team recommended replacing two rented diesel air compressors with a new, steam-driven compressor. This alone would reduce diesel fuel use by 108 gallons per day and save the plant $160,000 per year in rental fees. In another project, installing a new carbon monoxide control system would reduce CO and other emissions substantially.
Aspen Technology was chosen to develop the Energy Optimization and Management System (EOMS) using its Aspen Utilities software. This software analyzes conditions such as supply contract variability, alternative fuel options, optimum loading of steam boiler equipment, motor versus turbine driver decisions, and importing versus exporting of steam, fuel, and power. The EOMS will be used in assessing, implementing, and tracking changes in process unit energy use and in gauging the effects of implementing new projects. Aspen Technology estimated that the EOMS will reduce annual energy use by 2% to 6%.
Based in San Antonio, Valero has approximately 20,000 employees. The company owns and operates 14 refineries throughout the United States, Canada, and the Caribbean with a combined throughput capacity of more than 2 million barrels per day—or about 10% of total U.S. refining capacity. Valero purchased the Houston refinery in 1997.