increase the loss on ignition (LOI) and volatiles. The LOI listed in the table refers to the 1,800F LOI test; volatiles refer to the 1,200F volatiles test.
Other Additives Dust collector fi nes and re-
lease agents also can affect a facility’s emissions. References on dust collector fi nes go back over the past 50 years in the industry. Many metalcasting fa- cilities have tried (with various levels of success) to utilize dust collector fi nes as an addition to molding sand in both dry and wet (sometimes known as black water) applications. Dust collector fi nes consist of the binders (bentonite) and carbon additives that have been removed from the met- alcasting process at cooling and shakeout and are returned back into the molding sand in a controlled method. Some dust collector fi nes can contain up to 40% binder and carbon additives. (On average, the fi nes contain 30% binder and carbon addi- tives.) As a rule of thumb, when dust collector fi nes are added to prepared molding sand in a controlled method using various mechanical techniques, they can help reduce the amount of binder added, among other benefi ts. Green sand release agents are used to
achieve a smooth and even separation be- tween the prepared mold and the pattern on the molding machine. These release agents are formulated predominately from petroleum or vegetable-based oils. The references on this subject have shown that these release agents contribute to emissions during pouring, cooling and shakeout. Since all metal types use release agents in the metalcasting process, a reduction in their use or selection of the base oil will have an impact on pollution prevention.
Application of the Database Different metals can be cast
via various green sand molding methods, so producers of each metal type will have unique opportunities for pollution prevention. Green sand bind- ers (clays) have minimal impact
in their green sand additives. Iron casting facilities have re- duced their quantity of seacoal and/or gilsonite (materials that have higher emission charac- teristics) by up to 50% in the preblend formulation with the addition of processed carbon or causticized lignite (materials that have little or no emission characteristics). Nonferrous casting facili-
A recent study showed that 90% of a green sand facility’s hazard- ous air pollutant emissions occurs during pouring, cooling and shakeout operations.
on pollution prevention since they are mostly inorganic. The greatest impact on pollution prevention will be the selec- tion of the type of green sand additives (organic or inorganic), core sand dilution and green sand release agents. Pollution prevention can take many
directions, as the database suggests. A critical area is the quantity and type of organic materials added into green sand for all metal types. Many metalcasting facilities have successfully reduced their emissions by replacing carbon materials
ties, which use olivine or silica sand-based green sand systems, also have been able to reduce or eliminate seacoal and/or gilsonite from their preblend with the addition of processed carbon or causticized lignite. This reduction in carbon additives in nonferrous plants has resulted in the lower emissions required to meet government regulations. Another area for review is
ganic compounds referenced in the database) has a large impact on the development of CO during pouring, cooling and shakeout (Fig. 2). As the database shows, seacoal is not used in steel and aluminum casting facilities and therefore does not contribute CO in their molding sand. However, since iron and copper-base casting facilities do utilize seacoal, its reduction at those facilities will lead to pollution prevention. As referenced in the database, the
widely accepted methods for detect- ing the quantity of organic additives in green sand mold- ing systems is t he LOI test and the volatile test. It has been well documented that as the LOI test and volatile test decrease, the emissions characteristics of green sand during pouring, cooling and shakeout decrease.
MC About the Authors
Vic LaFay is research and technical development manager and Stephen Neltner is technical service engineer for S&B Industrial Minerals SA, Cincinnati. Dave Carroll is regional sales manager for American Colloid Co., Elgin, Ill. D.J. Couture is senior manufacturing process engineer for General Motors Corp., Pontiac, Mich.
For More Information
Fig. 2. Seacoal is a main contributor to greenhouse gas emissions at green sand casting facilities during pouring, cooling and shakeout.
MODERN CASTING / October 2010
“Know Your HAPs,” J. Schifo, MODERN CASTING, October 2005, p. 33.
29
greenhouse gases (CO and CO2
). Seacoal (and other or-
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