Simple Solutions That Work! Issue 12

38 TIM MCMILLIN Director Sales & Business Development IMERYS - High Temperature Solutions - Foundry Green Sand Bonding Solutions ARTICLE TAKEAWAYS: • Reclaim active clay and lustrous carbon from dust collector material • Water-based reclamation process to separate sand, clay and carbon • Can replace 20-30% of the foundry total need for bentonite RIKO © - RECOVERY OF BENTONITE & CARBON FROM FOUNDRY DUST A UNIQUE PROCESS TECHNOLOGY Foundry Dust Collection and the Loss of Beneficial Materials B entonite and carbon have long been used as key components in the green sand casting process. In 2018 United States Foundry Industry consumed approximately 700,000 tons of bentonite and carbon. Silica sand has been used in the green sand process for hundreds of years. Recently the United States Environmental Protection Agency instituted tighter regulations on the Permissible Exposure Limits for silica sand dust. This has meant an increased focus on, and need for additional ventilation and dust collection. While this ventilation and dust collection reduces the amount of fine silica sand, it extracts other useable materials, such as active bentonite and carbon. In the U.S. it is estimated that close to one million tons of dust from the casting process is disposed of in landfills annually. This includes over 150,000 tons of reusable bentonite and carbon. The estimated recovery value potential, for the U.S. foundries, is some $45 million USD. The need for a process to recover usable bentonite and carbon from the dust collector “waste” has been recognized for decades. However, the bentonite is typically bonded to the fine sand particles and very difficult to separate. Both dry and wet process have been tried over the years, but with limited success. The RIKO© Process RIKO is a unique, patented process for recovery of usable bentonite and carbon from foundry dust collection. • Historically, the difficulty was how to efficiently separate the clay and carbon from the fine sand grains it is adhered to. The large surface area of the fine sand, combined with the bonding strength of the bentonite makes separation a real challenge. • Dry and wet conventional process, including chemical accelerators, has been tried. But with limited technical and cost/ benefit success. • Water is the only constituent added to the dust in the RIKO process. Intensive hydraulic separation, specific gravity differences, and mechanical screening provide for simple, efficient recovery. A demonstrated 83% recovery from the dust provides a substantial amount of useable bentonite and carbon. • The process utilizes high shear mixing, hydro-cyclonic separation and screening to produce a slurry of 23% solids, typically comprised of hydrated clay (68%) and lustrous carbon (32%).