Steel companies are constantly refining their recycling operations to make the process more efficient and environmentally friendly. At Nucor Corp. we place a high value on being stewards of our environmental resources, and to that end we have become the largest recycler in North America.
During the steel recycling process, scrap metal is heated in an electric arc furnace (EAF) and, depending on the type of steel being produced, a combination of elements is added to the viscous steel to create the appropriate steel alloy. This process requires large amounts of energy that vary significantly depending on the amount of scrap placed in the furnace. When we purchased the Marion, OH facility in 2005, operators relied on estimates to determine the amount of steel placed in the furnace, causing the metal to be overheated oftentimes. This results in an unsatisfactory end product that must be recycled again, which costs the company time, money and energy.
To reduce the number of reheats, in 2007 we deployed a low-cost scale and weighing system using LabVIEW and NI Compact FieldPoint controllers that accurately calculates the amount of steel in each burn. Prior to implementing this system, we did not have a method of tracking the number of reheats; however, out of the more than 6,000 batches recycled in 2007, we only performed 10 reheats, which was far less than in 2006.
Eliminating Flicker and Improving Facility Safety
Not only did we receive monetary penalties for using too much electricity, but the power grid flicker was an inconvenience to Marion residents. To reduce electricity consumption, we developed an online reactor in series with the furnace using the LabVIEW FPGA module and the CompactRIO platform that measures the amount of energy drawn from the power grid. If the furnace approaches the prescribed limit, the system can quickly change control methods to reduce the amount of power being drawn.
The Benefits of Factory Automation Using NI PACs
By programming with LabVIEW and PACs versus programming with PLCs and ladder logic, we have seen a tenfold increase in efficiency and drastically reduced the costs of facility automation. Additionally, by developing a proactive approach for monitoring our power intake using the NI platform, we have reduced the impact our facility has on the residents of Marion by eliminating power grid flicker.