Shun Meng

Two-dimensional temperature characteristics of syngas flames with nitrogen, carbon dioxide, and steam diluents by planar laser-induced fluorescence thermometry

ABSTRACT In this research, the effects of nitrogen, carbon dioxide, and steam diluents on the two-dimensional temperature structures and characteristics of syngas flames were investigated by two-line planar laser-induced fluorescence thermometry. The spatial resolution and the total uncertainty of the measured results were 41.7 µm and ±8.45%, respectively. The experimental results demonstrated that diluting with carbon dioxide in the syngas flame resulted in the lowest flame temperature, followed by steam diluent. The measured temperature fields for these three diluents exhibited a symmetrical but nonuniform structure. It was found that the high-temperature region exists in the downstream of flame front, and the temperature decreases gradually inside-out in the burned zone of syngas flame. The findings in this work will improve our understanding of the temperature characteristics for the syngas flames with different diluents.

Use of a Process Mass Spectrometer to Measure Rapid Changes of Gas Concentration

Abstract Experiments were conducted to investigate the suitability of a multistage in-situ reaction analyzer based on a micro fluidized bed (MFB-MIRA) for measuring rapid changes of gas concentration during gas-solid reactions. The results show that control of capillary temperature of a process mass spectrometer strongly influences the stability of on-line measurements. Based on observed regular patterns, the capillary temperature-control system was equipped with a precision controller that enabled a precision of ±0.2 °C to be achieved, and thereby guaranteed high stabilities of the sampling flow rate and chamber vacuum. Measurements using the modified gas-monitoring system showed that periodic fluctuations of the on-line measurement were eliminated and measurement stability significantly improved. The fluctuating range and relative standard deviation of the measured response to O 2 in air improved from 1.9% to 1.4% and 0.54% to 0.18%, respectively. A pressure-regulating device was also developed to control the absolute pressure at the gas sampling point. This achieved a control precision of ±0.02 kPa. The measured results showed that the response of the process mass spectrometer correlated positively with the absolute pressure at the sampling point, indicating the necessity for a pressure-regulating device. The accuracy and repeatability of the process mass spectrometer were improved. This work has enhanced the suitability of MFB-MIRA for studying rapid gas-solid reactions and broadened the scope of reliable applications of MFB-MIRA combined with a process mass spectrometer.

Experimental Study of Rapid Brown Coal Pyrolysis at High Temperature

Rapid coal pyrolysis is a very important step in the early stage of combustion. Rapid pyrolysis experiments of a brown coal at high temperature have been studied on a laminar drop tube furnace. The volatile mass release measured in this study is high for low rank coal. The activation energy and pre-exponential factor of pyrolysis are 19901.22 kJ/mol and 102.71, respectively. The nitrogen distribution between volatile and char is 0.54. With the increase of temperature, the yields of NH3 decreases, while those of HCN increases, leading the value of HCN/NH3 to become larger. At high temperature, the main nitrogen- containing species of pyrolysis in volatile is HCN.

Numerical Study on the Stereo-Staged Combustion Properties of a 600 MWe Tangentially Fired Boiler

Numerical study of the combustion process and NO emission of a 600MWe tangentially fired boiler with stereo- staged combustion system were performed by Fluent 6.2 CFD software. The stereo-staged combustion technology is consist of horizontal bias combustion (HBC) burners, separated over fire air (SOFA), horizontal offset secondary air and pulverized coal reburning arrangement. The temperature field and the distribution of combustion species concentration in the furnace were gained as well as the aerodynamic field. The simulation results shows that stereo-staged combustion system can keep good combustion stability and the NOx emission of the boiler reduces significantly when the HBC burners and horizontal offset secondary air are adopted.