The highly energy-intensive stone mining and crushing industry, grouped with other mining industries, has been one of the focal sectors of the US Department of Energy's Industries of the Future (DOE-IOF) initiative. In addition to being highly energy intensive, stone crushing currently produces 42% of the total material consumed by weight in the US, which is mainly used as highway aggregates. Based on GDP growth projections, the use of crushed stone could increase at a quicker rate than any other major material use. Given the market size, ample resources and stable growth potential of this industry, the understanding and dissemination of energy efficiency opportunities is paramount for national energy efficiency goals. Further, since there are literally thousands of similar facilities throughout the US (owned by relatively few large holding groups), there is a huge opportunity for replicability of identified energy efficiency measures.
This paper will first review the stone mining, crushing, and asphalt production processes. In this review, we will show that energy use is focused in rock blasting, shot-rock transportation, rock crushing, conveying, and screening. As such, standard building energy efficiency measures such as lighting retrofits and support system optimization have small impacts on overall plant energy use. The identification of energy efficiency opportunities thus relies heavily on system optimization. System optimization not only encourages energy-efficiency, but typically benefits production as well. Coupled with productivity improvements, the economic incentives for energy-efficiency measures in this industry have the magnitude and quick payback that could facilitate industry-wide replication.
The selected case study will feature two plants that manufacture a variety of rock grades for asphalt aggregate, railroad ballast and other uses. These facilities are currently the focus of a US Department of Energy (DOE) Industries of the Future plant-wide assessment. The key findings of the study will be presented, with a critical eye on improvements that are not only applicable to this facility, but to the stone crushing and asphalt industry as a whole.