Assessment of Harmful Emissions from Multiple Binder Systems in Pilot-Scale Sand Casting

Abstract

This study investigates hazardous emissions from foundry binder systems, comparing organic resins (phenolic urethane, furan, and alkaline-phenolic) and clay-bonded green sand with inorganic alternatives (sodium silicate and geopolymer). The research was conducted at the Fundaciόn Azterlan pilot plant (Spain), involving controlled chamber tests for the production of 60 kg iron alloy castings in 110 kg sand molds. The molds were evaluated under two configurations: homogeneous systems, where both mold and cores were manufactured using the same binder (five trials), and heterogeneous systems, where different binders were used for mold and cores (four trials). Each mold was placed in a metallic box fitted with a lid and an integrated gas extraction duct. The lid remained open during pouring and was closed immediately afterward to enable efficient evacuation of casting gases through the extraction system. Although the box was not completely airtight, it was designed to direct most exhaust gases through the duct. Along the extraction system line, different sampling instruments were strategically located for the precise measurement of contaminants: volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), phenol, multiple forms of particulate matter (including crystalline silica content), and gases produced during pyrolysis. Across the nine trials, inorganic binders demonstrated significant reductions in gas emissions and priority pollutants, achieving decreases of over 90% in BTEX compounds (benzene, toluene, ethylbenzene, and xylene) and over 94% in PAHs compared to organic systems. Gas emissions were also substantially reduced, with CO emissions lowered by over 30%, NO_x by more than 98%, and SO₂ by over 75%. Conducted under the Greencasting LIFE project (LIFE 21 ENV/FI/101074439), this work provides empirical evidence supporting sodium silicate and geopolymer binders as viable, sustainable solutions for minimizing occupational and ecological risks in metal casting processes.

Keywords: foundry emissions; hazardous pollutants; inorganic binders; occupational health; polycyclic aromatic hydrocarbons; volatile organic compounds.

Figure 1

BTEX emissions of each system and combinations and individual BTEX compounds, calculated per kilogram of molding sands (specific numerical values provided in Table 2).

Figure 2

Total PAH emissions for each system, calculated per kilogram of molding sands.

Figure 3

Real-time monitoring of CO concentrations during the experimental period for the nine different systems (note that 5000 ppm is the upper limit of the equipment).

Figure 4

Real-time monitoring of NO_x concentrations during the experimental period for the nine different systems.

Figure 5

Real-time monitoring of SO₂ concentrations during the experimental period for the nine different systems.

Figure 6

Real-time monitoring of O₂ concentrations during the experimental period for the nine different systems.

Figure 7

Experimental setup for measurements of emissions from sand castings. Figure adapted from [12] doi.org/10.3390/ma14102581