Yingjuan Shao

GAS-SOLID FLOW BEHAVIOR IN A PRESSURIZED HIGH-FLUX CIRCULATING FLUIDIZED BED RISER

Gas-solid flow behavior was investigated in a high-flux circulating fluidized bed (HFCFB), whose riser is 0.068 m ID and 5.2 m high. Experiments were carried out at different pressures (0.1–0.5 MPa), solids mass fluxes (122–1015 kg/m2 · s), and standard state superficial gas velocities (6–40 m/s). Geldart group B particles 137 µm in diameter and 2490 kg/m3 in density were used as bed materials. Information on pressure drop, apparent solids holdup, average slip velocity, and solid-to-air mass flow ratio were systematically tested at elevated pressures. The results showed that increase of the operating pressure led to higher total riser pressure drop and solids holdup, lower slip velocity, more homogeneous pressure drop, and longitudinal solids holdup distribution. As a result, a high-density condition with Geldart group B particles, i.e., solids holdup in the riser over 10%, could be successfully formed in the HFCFB at elevated pressure. Similar to the trend at atmosphere, the dimensionless slip velocity at pressurized condition increased with increasing solids holdup for any given superficial gas velocity, and the total riser pressure drop increased approximately linearly with solids-to-air mass flow ratio at the given operating pressure.

Recent Advances of Spout-Fluid Bed: A Review of Fundamentals and Applications

Abstract The spout-fluid bed (SFB) is a very successful synthesis of the spouting and fluidization. The hydrodynamics of SFB are more complex than both fluidized beds and spouted beds. Up-to-date information on the fundamentals and applications of SFBs has been briefly presented, based on the limited work reported, in the new spouted bed book edited by Norman Epstein and John R. Grace (Spouted and spout-fluid beds: fundamentals and applications, 2011). In the past three years, nearly 30 papers have been published in international journals. They reported interesting studies on hydrodynamic characteristics, numerical simulations and new applications of SFBs. This article reviews the major research and development on SFB from the year 2010 and recommends further research topics. This review is intended not only as an important supplement to the SFB chapter of the spouted bed book but also helpful guidance for future research.

Experimental Research on Utilization of Steel Rolling Sludge in Sintering Process

Abstract A quantity of steel rolling sludge (SRS) produced in the rolling mill is harm to the environment and difficult to dispose. This article is devoted to study on utilization of SRS in sintering process. A sinter pot system with capacity of 75 kg was established. The sintering time, the flue gas temperature, the sintering temperature and the suction pressure in sintering process were measured. Besides the sinter quality, air pollutants discharged from the sintering process with the mass fraction of SRS ranging from 0 to 3% was investigated. The results showed that the CO2 concentration is corresponding to the sintering process, the SO2 concentration has a self-sustaining characteristic and the NOX concentration maintains stability. Increase in mass fraction of SRS leads to the decrease of sintering temperature, particle size, tumbler index and basicity of the sinter. Besides, the sintering time and the average concentration of NOX decrease first and then increase, while the suction pressure appears an opposite trend with increasing mass fraction of SRS. Moreover, the average concentration of CO2 and SO2 both decrease with increasing mass fraction of SRS, and the fuel consumption per sinter produced is the least when the mass fraction of SRS is 2%. Therefore, when the mass fraction of SRS was 2%, the sintering process had the best performance in consideration of sinter quality, emission of air pollutants and behaviors in sintering process.

Thermodynamic Analysis of Supercritical CO2 Power Cycle with Fluidized Bed Coal Combustion

Closed supercritical carbon dioxide (S-CO2) Brayton cycle is a promising alternative to steam Rankine cycle due to higher cycle efficiency at equivalent turbine inlet conditions, which has been explored to apply to nuclear, solar power, waste heat recovery, and coal-fired power plant. This study establishes 300MW S-CO2 power system based on modified recompression Brayton cycle integrated with coal-fired circulating fluidized bed (CFB) boiler. The influences of two stages split flow on system performance have been investigated in detail. In addition, thermodynamic analysis of critical operating parameters has been carried out, including terminal temperature difference, turbine inlet pressure/temperature, reheat stages, and parameters as well as compressor inlet pressure/temperature. The results show that rational distribution of split ratio to the recompressor (SR1) achieves maximal cycle efficiency where heat capacities of both sides in the low temperature recuperator (LTR) realize an excellent matching. The optimal SR1 decreases in the approximately linear proportion to high pressure turbine (HPT) inlet pressure due to gradually narrowing specific heat differences in the LTR. Secondary split ratio to the economizer of CFB boiler (SR2) can recover moderate flue gas heat caused by narrow temperature range and improve boiler efficiency. Smaller terminal temperature difference corresponds to higher efficiency and brings about larger cost and pressure drops of the recuperators, which probably decrease efficiency conversely. Single reheat improves cycle efficiency by 1.5% under the condition of 600°C/600°C/25Mpa while efficiency improvement for double reheat is less obvious compared to steam Rankine cycle largely due to much lower pressure ratio. Reheat pressure and main compressor (MC) inlet pressure have corresponding optimal values. HPT and low pressure turbine (LPT) inlet temperature both have positive influences on system performance.