High temperature Solutions – Foundry

Green Sand Bonding Technologies

RIKO© - Recovery of Bentonite & Carbon From Foundry Dust
A Unique Process Technology

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

Foundry Dust Collection and the Loss of Beneficial Materials

Bentonite 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%).

  • The bentonite and carbon slurry is added back into the sand preparation process. It comprises a significant percentage of the water, bentonite and carbon needed in the green sand process.

  • Because it is pre-hydrated, the RIKO material exhibits better binding and sand property performance compared to traditional dry materials.

  • The recovered bentonite and carbon is at least 50% lower in total cost versus traditional, dry bentonite and carbon.

  • No need for capital equipment investment. IMERYS invests the CapEx, licenses process, and charges monthly for the amount of material produced/consumed. The foundry operates the system and pays all variable expenses, with IMERYS remote monitoring and regular field technical assistance.

  • Patents have be submitted for expansion of the RIKO process to include a unique dry separation methodology. This is still in the development stages, but would allow for a much larger percentage recovery and foundry market capture.

  • Research on a dry process involves a similar cyclonic removal technique, but without introduction of water. While less efficient, this dry technique does not limit the amount of material that can be re-introduced into the foundry sand system.

 

 

 


- A semi solid thixotropic solution consisting of 20-25% solids

− With >65% bentonite and >20% carbon