Reyes Skovgaard (breathfemale2)

SO2 emissions from coal-fired boilers are air pollutants and a source of acid rain, causing extensive environmental pollution. Limestone (CaCO3) is a Ca-based sorbent which is injected into circulating fluidized bed (CFB) boilers, where it combines with SO2 to produce calcium sulfate (CaSO4). As a result, SO2 emissions from a power plant are reduced. In this study, CaCO3 addition was proposed and the desulfurization efficiency improved. The direct desulfurization reaction is dominant in a commercial CFB boiler due to the high CO2 partial pressure, but CaO is formed at a fast reaction rate by calcination in the high temperature or in the low CO2 partial pressure region. When CaO remains in the loop seal, it is exposed to a high CO2 partial pressure condition moving through the recirculation section for an extended period and re-injected into the furnace as recarbonated CaCO3. To analyze the direct desulfurization reaction kinetics, a shrink core model in which the reaction proceeds inside the particle was adopted. Surface observations through FE-SEM of CaSO4 produced by the 180 minute long desulfurization experiment using TGA suggest that the CaSO4 crystal growth rate increased after the pre-treatment (recarbonation) of limestone. Recarbonation lowered the limestone crystallinity, causing a faster reaction. The CaCO3 recarbonation increased the Ca utilization by more than 20% when the direct desulfurization reaction occurred. The TGA experiments show that recarbonation contributes to CaSO4 conversion. Increasing the desulfurization efficiency using recarbonation can reduce the fixed investment and operating costs of oxy-fuel CFB plants because only desulfurization in the furnace is able to meet SO2 emission regulations or lower the flue gas desulfurization (FGD) dependence. Accordingly, the desulfurization conversions of recarbonated CaCO3 and limestone were compared in this study. Morphological changes in the limestone were also evaluated using XRD, FE-SEM, and other analysis methods.Solid wastes from commercial coal gasification plants are a significant environmental issue in China because of the large quantities produced. In recent years, with the rapid development of coal gasification technologies in China, more and more coal gasification residues are being disposed of in landfills because of the low utilization of the residues. In the present study, the column leaching procedure M1314 developed by the U.S. Environmental Protection Agency was used to evaluate the potential for environmental pollution by potentially hazardous trace elements (Be, V, Mn, Cr, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sb, Cs, Ba, Tl, Pb, Hg, Th, and U) in the coarse and fine gasification residues from two plants using General Electric (GE) and Gaskombinat Schwarze Pumpe (GSP) coal gasification technologies in northwest China. The potentially hazardous trace elements in the residues show different release patterns with the liquid-solid ratio increasing. The cumulative leached concentrations of the potentially hazardous trace elements from the coal gasification residues were generally low, and only Mo in the leachate of GSP fine residue was moderately soluble. V in the GSP coal gasification residues showed an increasing leachability in the leaching procedure. As, Se, Mo, Sb, and Tl in some leachates exceeded their thresholds in Level III of the Chinese Quality Standard for Groundwater and/or the Maximum Contaminant Levels of the U.S. National Primary Drinking Water Regulations. According to the risk assessment code, Se in the GE fine residue and Mo in the GE and GSP fine residues had medium risk to the ecosystem. Those data indicated that the potential for environmental pollution by those elements from coal gasification plants should be given consideration.The use of Raman spectroscopy for analytical quality control of anticancer drug preparations in clinical pharmaceutical dispensing units is increasing in popularity, notably supported by commerciall