STUDY ON THE APPLICATION OF ADVANCED OXIDATION PROCESSING IN GREEN SAND FOUNDRIES

Open Access
Author:
Wang, Yujue
Graduate Program:
Environmental Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
September 26, 2006
Committee Members:
  • Fred Scott Cannon, Committee Chair
  • Robert Carl Voigt, Committee Member
  • Sridhar Komarneni, Committee Member
  • John Michael Regan, Committee Member
Keywords:
  • advanced oxidation
  • green sand foundry
  • air emission
  • clay
  • coal
Abstract:
Green sand foundries have been continuously seeking new production process modifications that will reduce their pollutants, while also diminishing operation costs. The recent development of advanced oxidation (AO) technologies offers these foundries great opportunity to achieve both pollution prevention and material conservation. An AO system (Sonoperoxone™, Furness-Newburge, Versailles, KY) has been incorporated into the conventional foundry process on 22-30 production line that together have the capacity to manufacture about 10-15% of the cast iron in America. The AO systems condition the water that is used in the molding process by coupling ozone, hydrogen peroxide, ultrasonics, and (optionally) underwater plasma. The AO process can reduce air pollutant emission by 20-75% and diminishing clay and coal consumption by 20-35% in these foundries. While the empirical effects of AO on pollution prevention and material conservation have been known for several years, the mechanisms behind these effects are not well understood. In that light, this research appraised the fundamental engineering and science underlying the AO process, and sought to better understand the mechanisms by which the AO process diminished the air pollutants and raw material consumptions. It was discovered that AO processing greatly enhanced the reclamation of clay and coal from baghouse dust. The ultrasonic component of the AO processing effectively separated the clay and coal particles from the sand fines, thus allowing the clay and coal to be recycled for reuse. The ultrasonics also considerably decreased the particle size of the clay by delaminating the clay into more discrete platelets; and this improved the bonding efficiency of a given amount of clay. Surface elemental analysis revealed that AO processing effectively displaced pyrolytic residues of carbonaceous additives that typically accumulated on the clay surface. This restored the damaged foundry properties of the clay and decreased the requirement of new makeup clay addition. AO processing was found to considerably affect the pyrolysis behavior of the coal composition of the green sand. The AO conditioned coal released less mass and emissions than the non-AO conditioned coal during pyrolysis. In addition, more activated carbon was generated from the coal when AO processing was employed in the casting process. Both the AO-enhanced activated carbon generation, plus the AO-incurred clay surface cleaning provided the AO conditioned green sand with higher pore volume, and thus higher adsorption capacity for volatile organic compounds (VOCs). The results reported herein conformed to full-scale foundry empirical finding that when AO is used, foundries need less makeup clay and coal addition through each casting cycle, and they release less air emissions. The author also appraised the emissions character of several carbonaceous additives that could be use in green sand foundries. Of the three coal types evaluated, anthracite released fewer volatiles than did lignite or a highly volatile bituminous coal (seacoal). Cellulose released considerably more volatiles than any of the coals when it was flash pyrolyzed in a Curie-point pyrolyzer. However, when cellulose was gradually heated, it released far fewer volatiles. This means that if cellulose were to be used in a green sand mold, it would release volatiles where they are needed at the molten metal-mold interface, but volatiles would not be released much at further distance from this interface that gradually heats. This characteristic of the cellulose offers an important opportunity for the foundries to diminish their air emissions.