Effects of raw material compositions on the emission and distribution of heavy metal conents during the iron ore sintering process

• Main Authors: Ai-yun Hsieh, 謝艾芸
• Other Authors: Jin-luh Mou
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/38139707072243569474

碩士 === 國立成功大學 === 環境醫學研究所 === 95 === Sinter plant is one of the heavy metal pollution sources from the iron and steel industry. Currently the heavy metals emission data of the sinter plant are almost obtained from the real plant emissions, but the relationship between changing raw materials and its effects on heavy metals emission characteristic and their fates are needed to further investigate. In this study, mini sinter pot was applied to simulate the iron ore sintering process. The raw materials (iron ores, fluxes and west returns) blending ratios were specified based on a real plant and was used as a basic to evaluate the heavy metal emissions. An iso-kinetic sampling method of EPA Method 29 for heavy metal from stack flue gases has been used to collect samples. In addition, bulk samples of raw materials and sinters were collected during flue gases samplings. All collected samples were analyzed for their As, Hg, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn contents by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer). Finally the metal emissions and distribution proportions were determined and were used to find the effects on heavy metal emission caused by iron ores, fluxes and west returns. Results showed that highest heavy metal content in six iron ores(including YAN, MAC, MTF, MBR, CVRD and CARA) is Mn; all the second highest is Pb. Comparing heavy metal emissions of six different iron ores, the highest one is Pb among all heavy metals might because its lower melting point . Heavy metal contents of two tested fluxes shows Reef (176mg/kg)＞Marble (120mg/kg). The results of heavy metal emissions of the two tested fluxes show Reef had a lower heavy metal emission than Marble. This might because the CaO content containing in the Reef. When waste returns of EP dust was used to replace 5% YAN iron ore, we found that a higher heavy metal emission. That might because high heavy metal content originally containing in the EP dust. Because on our mass balance results, we found that with an exception of Hg exists in the flue gases, all other metals mostly remain in the sinters (>70%). In the flue gases, with the exception of Hg exist in the gas phase, all other metals are mainly preserved in the particle phase. Among them Cd, Pb, Zn and As are the heavy metals with low melting point, their major existence in the sinters may be influenced by SiO2. The predicted model of heavy metals contents containing in raw materials and their corresponding emission factors are as follows, Cd: y = 0.234x - 3.673 (n=8, R² = 0.697); Cr: y = 0.129x - 8.127 (n=8, R² = 0.582); Cu: y = 0.210x - 3.082 (n=8, R² = 0.738); Mn: y = 0.003 x + 0.460 (n=8, R² = 0.844); Ni: y = 0.069x - 1.558 (n=8, R² = 0.702); Pb: y = 1.096x - 49.622 (n=8, R² = 0.979); Zn: y = 0.052x - 1.493 (n=8, R² = 0.875); As: y = 0.029 x - 0.152 (n=8, R² = 0.612); Hg: y = 0.203x + 0.113 (n=8, R² = 0.049)。High correlation (R2=0.582-0.979) were found between eight heavy metals contents containing in raw materials and their corresponding emission factors, with an exception found in Hg (R2=0.049), Above data means heavy metal contents containing in raw materials plays the most important role on heavy metal emissions with an exception of Hg. Precdicting the heavy metals annual emission rate from sinering process(including four sinter plants) found the highest one is Pb 464 ton/year among all heavy metals and total heavy metal annual emission rate is 851 ton/year。Total heavy metal emission from sinering process (including four sinter plants) is 6.84 times higher than coal fired power plant and 12.6 times higher than oil fired power plant. Pb emission from sinering process (including four sinter plants) is 268 times higher than coal fired power plant and 414 times higher than oil fired power plant.