Refining Oil and Saving Energy: Energy Efficiency in the Refining SectorAllison Donnelly for Zondits, July 7, 2014
Petroleum refining is one of the most energy-intensive large manufacturing sectors, even without including the energy content of the fuels being refined. Roughly 22% of US industrial energy use—in the form of fuel, electricity, and steam—goes into refining. Energy also represents the second-largest cost for refiners, behind the petroleum itself, and so refiners that continue to invest in energy efficiency stand to gain substantial savings in energy use and costs. What follows is a brief discussion of some of the refinery processes that could benefit from efficiency measures.
Supply-Side Efficiency Measures
Refineries generate most of their energy on-site by burning waste fractions of the crude oil to generate heat, steam, and electricity. Those refinery processes are referred to as “supply-side” processes, whereas processes that consume their outputs are called “demand-side” processes.
- Stationary combustion units (boilers and heaters) are typically the largest consumers of energy within the refinery. Preheating the combustion air can decrease boiler fuel consumption from 13%‒51%, meaning an increase in the unit’s efficiency of 8%‒18%. One UK refinery realized annual energy savings of more than $100,000 by installing a preheater; the payback period was 2.2 years.
- Steam systems (steam-generating boilers and steam distribution) account for around 38% of a refinery’s energy requirement, and they can be improved through a variety of measures, including boiler feed water preparation, improved insulation and maintenance, and heat recovery from flue gas. If a boiler is in need of replacement, a high efficiency boiler can be 15%‒20% more efficient than a conventional one, decreasing fuel use and therefore emissions.
- Combined heat and power (CHP) is one of the most widely used ways to increase power generation efficiency by generating two refinery inputs together; efficiency improvements can be on the order of 27%. In 2010, 60%‒70% of refineries already used CHP. Installing a new CHP system is expensive, but the annual cost savings are substantial (a study for one refinery showed that a 6.5 MW CHP plant would save it $3.8 million per year).
- Cogeneration of electricity and hydrogen – in use at six refinery hydrogen plants – is likewise a way of producing two inputs simultaneously.
Demand-Side Efficiency Measures
The distribution and consumption of heat, steam, and power offer plenty of locations where efficiency improvements can be made.
- Heat exchanger networks can be improved by increasing the efficiency of each heat exchanger, integrating heating and cooling, and recovering waste heat.
- The steam distribution network can reduce losses through increased insulation, condensate return, decreasing venting, repairs, and monitoring.
- Individual process units (such as fluid catalytic cracking units, coking units, and sulfur recovery units) are a good place to investigate for efficiency improvements. Refineries may have dozens of process units, each with different inputs, uses, and operating conditions.
- Motors consume 70%‒80% of a refinery’s electricity, and their efficiency can be increased 12%‒15% through efficiency investments. High efficiency motors can also replace older motors.
- Lighting systems are good places for cost-effective efficiency improvements, which can reduce their electricity use by 15%‒50%.
- U.S. Department of Energy, “Manufacturing Energy and Carbon Footprints (2010 MECS),” 2014.
- Hydrocarbon Publishing Company, “Prospectus – Refinery CO2 Management Strategies: Technology Solutions to Reduce Carbon Footprint and Meet Business Sustainability Goals,” April 2010.
- US Environmental Protection Agency, “Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from the Petroleum Refining Industry,” Oct 2010.