Browsing by Author "Duan, Yuanqiang"

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    Flow characteristics in pressurized oxy-fuel fluidized bed under hot condition
    (Elsevier, 2018-06-28) Li, Lin; Duan, Yuanqiang; Duan, Lunbo; Xu, Chuanlong; Anthony, Edward J.
    Pressurized oxy-fuel fluidized bed (POFB) combustion is regarded as a promising technology for carbon capture from coal-fired power plants. High pressure and temperature conditions have important impacts on the flow characteristic of fluidized bed, and understanding them will help to optimize the design and operation of the POFB boiler. In this work, experiments were carried out in two pressurized fluidized bed (PFB) devices (a hot PFB and a “visual PFB”) both operated under high temperature (20-800 °C) and high pressure conditions (0.1-1.0 MPa). Four parameters including the minimum fluidization velocity (umf), the minimum bubbling velocity (umb), bubble diameter (Db) and bubble frequency (f) were examined in this study. Results showed that the umf decreases with rising pressure and temperature. Based on our results a formula was fitted for calculating the minimum fluidization velocity in PFB, with a relative error less than 15%. With the increase of fluidization number (w), the bubble size and tail vortex increased gradually, the bubbles tended to merge, and the shape of bubbles became more irregular. The Db decreases with the increase of temperature and pressure at the same w. The f increases with increased w, while it decreased with the increase of temperature and pressure.
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    Nitrogen and sulfur conversion during pressurized pyrolysis under CO2 atmosphere in fluidized bed
    (Elsevier, 2016-10-25) Duan, Yuanqiang; Duan, Lunbo; Anthony, Edward J.; Zhao, Changsui
    Pressurized oxy-fuel combustion (POFC) is a promising technology for CO2 capture from coal-fired power plants, offering both high efficiency and a low penalty. However, the high partial pressure of CO2 in a POFC furnace has important impacts on fuel-N and fuel-S conversion during the coal pyrolysis process, and understanding this will help to achieve further control of SOx/NOx. In this study, coal pyrolysis experiments were conducted in a pressurized fluidized bed with the pressure range of 0.1–0.7 MPa under N2 and CO2 atmosphere. The gaseous products were monitored by a Fourier transform infrared spectroscopy analyzer (FTIR) and the char residue was characterized by an X-ray photoelectron spectroscopy (XPS) analyzer in order to acquire the species information for S-containing and N-containing compounds. Results show that the enrichment of CO2 in the local atmosphere enhances the fuel-N conversion to HCN in the pyrolysis process, which serves as a favorable precursor to N2O. The generation of HCN and NH3 increase simultaneously with the increase of overall pressure. SO2 concentration in the gaseous product is relatively low, and as the pressure increases, the concentration decreases slightly due to CO reduction of SO2 to COS. Sulfur content in the char decreases as the pressure goes from 0.1 MPa to 0.7 MPa indicating higher CO2 pressure accelerates the decomposition of sulfur compounds in the coal, which is further confirmed by the XPS results.
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    Observation of simultaneously low CO, NOx and SO2 emission during oxy-coal combustion in a pressurized fluidized bed
    (Elsevier, 2019-01-15) Duan, Yuanqiang; Duan, Lunbo; Wang, Jia; Anthony, Edward J.
    Pressurized oxy-fuel combustion is a promising technology for CO2 capture with respect to its high combustion efficiency and the simultaneous reduction of gaseous pollutants. A 10 kWth bubbling fluidized bed reactor with continuous coal-feeding was designed, and effects of pressure, temperature and fuel types on pollutant emission were investigated in detail. Generally, the relatively low carbon content in the ash and CO concentration in the flue gas demonstrated that the combustion efficiency was improved by high pressure. The concentration of NO, N2O and SO2 showed decreasing trends with the increase of pressure. Moreover, the effect of pressure on the emission of NO and SO2 in the lower pressure (≤0.3 MPa) was more pronounced than that in the higher pressure. The concentrations of NO and SO2 correlated positively with temperature, while for N2O, it had a negative correlation. Compared with air combustion, NO and SO2 emission dropped sharply in 21%O2/79%CO2 atmosphere. However, N2O concentration during oxy-combustion was slightly higher than that in air combustion in the range of experimental pressure.