||Kaohsiung Lin-hai Industrial Park is an industrial complex and one of the largest industrial areas in Taiwan. Iron works is one of the important stationary sources in Kaohsiung Lin-hai Industrial Park, including an integrated iron and steel plant and several electric arc furnace plants, in which main air pollutants emitted are particulate matter. Currently the stack emission data is rather rare for the steel plants in Taiwan. Thus, this study aims to collect particulate matter emitted from the stacks of steel plants and further analyze its physical and chemical properties, in order to establish the elemental indicator(s) of different manufacturing processes. The results could provide valuable stack emission data to the environmental related governments and research institutes, for establishing air pollution control strategies and identifying potential emission sources.|
In this study, we initially reviewed literature related to particulate matter emitted from the stacks of steel plants, and then conducted stack sampling and chemical analysis of particulate matter emitted from the stacks in Kaohsiung Lin-hai Industrial Park. This study applied a method for sampling and analysis of particulate matter from a stack (NIEA A101.73C) issued by The National Institute of Environmental Analysis for stacks sampling, and further correlated the characteristics of particulate matter with emission sources in the steel plant industrial park.
The air pollution control devices set up in the front of the stacks in the iron and steel manufacturing processes include fabric filter, electrostatic precipitator, and flue gas denitrification (FGDN) device, which mostly operated with the stack emission standard. The concentration of particulate matter emitted from the manufacturing processes ranged between 2.0-62.9 mg/Nm3, which were lower than the stack emission standards and previously detected data.
Results obtained from water-soluble ionic species of particulate matter in the flue gases emitted from stacks showed that the most abundant anion was SO42- and followed by Cl- and F-, while the most abundant cation was Ca2+ and followed by Na+ and K+. The molar ratio of Cl- to Na+ (Cl/Na) ranged between 0.43 and 2.43, while the molar ratio of anion to cation (A/C) ranged between 0.38 and 1.18. Elemental analysis of metals showed that Al was the major metallic element. In addition, the averaged OC concentration was higher than EC, and the OC/EC ratio ranged between 0.68 and 4.58.
Among all chemical species, SO42- was the major species of particulate matter in the steel manufacturing processes. It probably due to raw materials containing sulfur content, which could be oxidized to form sulfur dioxide and further converted to sulfate. Moreover, desulfurizer was generally added to remove impurities in the steelmaking processes, resulting in high concentration of SO42-. Using the recycling fines containing chloride and potassium ions caused higher concentrations of K+ and Cl- in the sintering process while compared to other manufacturing processes.
Aluminum was the most abundant metallic element of particulate matter emitted from the stacks. It possibly resulted from the reduction process for using aluminum oxide to remove oxygen form aluminum oxide ( or alumina). Iron was the second richest metal since steel plants used iron ore, waste steel, and alloy steel as raw materials. Therefore, iron was another elemental indicator of particulate matter emitted from iron and steel manufacturing processes.
Concentration of potassium in particulate matter emitted from sintering process was higher than those from other processes due to the usage of flux in the sintering process. The percentages of iron oxide (Fe2O3) and calcium oxide (CaO) in the particulate matter emitted from the sintering process were the highest. Accordingly, the concentration of iron and calcium elements became relatively higher. The particulate matter emitted from the sintering process with relatively high resistivities made it difficult to achieve high removal efficiency of particulate matter by applying electrostatic precipitators. High calcium concentration of particulate matter emitted from the coking process resulted from the use of huge amount of limestone in the process. Thus, aluminum, iron, and calcium were the elemental indicators of particulate matter emitted from the coking process.
Furthermore, the indicating elements of particulate matter emitted from the coal burning boiler were aluminum, calcium, and iron. Titanium had higher concentration due to the existence of metallic oxide and trace elements in the bottom ash. Aluminum, iron, and titanium were the major recycling metals, and thus titanium can be treated as the indicating element of particulate matter emitted from the coal burning boiler. In the basic oxygen furnace (BOF) process, we served calcium carbide (CaC2) as the desulfurization medium. Therefore, calcium could be the indicating element of particulate matter emitted from the BOF process. Furthermore, nickel was the indicating element of stainless steel, while zinc and lead played as the indicating elements of carbon steel manufacturing process.