Journal of the Korea Academia-Industrial cooperation Society (한국산학기술학회논문지)

The Korea Academia-Industrial cooperation Society (한국산학기술학회)
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Production of Fluorosilicic Acid from Phosphoric Acid Slurry of a Fertilizer Manufacturing Plant

비료공장의 인산 슬러리로부터 규불산 제조

  • Kim, Se-Won (Center for Green Construction Material, University of Ulsan) ;
  • Moon, Woo-Kyun (Korea Industrial Complex Corp.) ;
  • Park, Hung-Suck (Department of Civil & Environmental Engineering, University of Ulsan)
  • 김세원 (울산대학교 친환경건자재사업단) ;
  • 문우균 (한국산업단지공단) ;
  • 박흥석 (울산대학교 건설환경공학부)
  • Received : 2011.10.27
  • Accepted : 2012.02.10
  • Published : 2012.02.29
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Abstract

Phosphoric acid used for the production of phosphate fertilizers is synthesized by the reaction of phosphate rock and sulfuric acid. As the reaction is exothermic, yield of phosphoric acid is poor at elevated temperature. Therefore, enhancement in its yield requires the process temperature be maintained by releasing the vapor ($80^{\circ}C$) containing HF and SiF4 through a vacuum cooler. However, these valuable resources; Fand Si, which can be utilized for the manufacture of refrigerant and polysilicon, respectively, are being wasted in the treatment process. We performed lab-scale experiments to estimate the amount of recoverable H2SiF6, a by-product of phosphoric acid manufacturing process. The experimental results showed a decrease of fluorine concentration by 0.12wt% in the liquid phase. Preliminary estimation showed a possible recovery of 5,509 ton/yr of fluorine considering the scale of the fertilizer manufacturing plant. Furthermore, field-scale experiment showed that H2SiF6 could be enriched in liquid phase from 0.35wt% to 7.33wt% and the vapor flow-rate from vacuum cooler was estimated at $51,000m^3/hr$. Anew, the efficiency of fluorine recovery in the pilot-scale experiment was found to be 76.74% and the production of H2SiF6 was estimated at 5,340 ton/yr.

일반적으로 비료용 인산은 황산과 인광석의 분해반응에 의해 생산되는데 이 반응은 발열반응으로써 온도가 상승하게 되면 생산수율 저하의 문제점이 따른다. 이를 해결하기 위해 인산제조공정에서는 불산(HF)과 사불화규소(SiF4)가 함유된 증기(vapor, $80^{\circ}C$)를 배출시키는 진공냉각기(vacuum cooler)를 운영하고 있으나, 이 과정에서 냉매 및 폴리실리콘 원료로 활용가능한 귀중한 자원(불소 & 규소)들이 버려지고 있다. 본 연구는 인산제조공정 부산물인 규불산(H2SiF6)으로 회수하기 위한 기초 실험연구로서, 불소회수 후 인산슬러리 내 불소 농도변화를 분석하여 규불산 회수가능량을 예측하였다. 회수 후 불소농도는 약 0.12wt% 감소하였고, 대상 비료공장의 생산규모를 고려할 경우 불소 회수가능량은 약 5,509 톤/년이었다. 한편 현장에서, 규불산의 농도는 0.35wt%에서 7.33wt%까지 농축되었고, 진공냉각기로부터 배출되는 증기유량은 $51,000m^3/hr$이었다. 또한 Pilot실험을 통한 불소 회수효율은 76.74%로 나타나, 실제 회수할 수 있는 규불산량은 5,340 톤/년으로 추정되었다.

Keywords

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