Xianjun Xing

Numerical simulation of a new two-stage dry feed gasifier for double-high coal

In order to study the characteristics of a new two-stage dry feed gasifier with multi underneath nozzles jetting tangentially, numerical simulation and analysis of the gasifier for high ash melting point pulverized coal was conducted based on Fluent. A comprehensive mathematical model for simulation of pulverized coal gasifier has been developed in this paper, chemical process was described with presumed PDF mode, a gasification look-up table was built to describe the relationship between mixture fraction and the scalars of temperature, species, et al. Body fitted hexahedron mesh was adopted and k-ε RNG turbulent model was used to make a closure for turbulence equations. Dispersed phase model (DPM) were employed to describe the coupling effect between gas phase and discrete phase, and Stochastic Tracking Method (STM) were used to track turbulent dispersion of char particles and to consider the turbulent disturbance effects on particle motion on gasification process. In addition, User Defined Functions (UDF) was used to mend heterogeneous gasification reactions model, including carbon with O2, H2O, CO2 and H2. The numerical simulation and analysis of the inner velocity, temperature and species concentrations of the two-stage entrained flow coal gasifier for high ash melting point pulverized coal shown that spatial gasification reactions can be achieved in the gasifier, inner temperature grads reduce remarkably and temperature field become more even, and the key gasification parameters, such as [O]/[C] atom ratio, steam/coal ratio, were optimized through simulation, will offer reference for the further research on the gasifier for high ash melting point pulverized coal.

Research on the Three Different Kinds of Technologies to Achieve Flameless Combustion and Their Applications

Flameless combustion was first to developed suppress thermal NOx formation and raise the efficiency of combustion. Now in further research, three different combustion technologies can be used to achieve flameless combustion those are high temperature air combustion (HTAC), normal temperature air combustion (NTAC) and oxy-fuel flameless combustion. This paper presents a description of the three different technologies, the development of their application in gaseous, liquefied and solid fuels combustion as well as their industrial applications at a research stage. These flameless combustion applied combustion technologies guarantees the uniform temperature distribution, fuel consumption reduction and productivity when applied, for example, to coal gasification, and to low calorific fuel combustion.

Discussion on Gasification of High Ash Melting Point Pulverized Coal Using Excess Enthalpy Combustion

The paper presents the principle and development of excess enthalpy combustion, and recommends that excess enthalpy combustion (high temperature air combustion or flameless combustion ) was applied to correlative researches such as combustion and gasification of solid fuel-pulverized coal. Based on the characteristics and gasification difficulty of coal in China, this paper also puts forward that Normal Temperature Air Flameless Combustion developed by our research team can be apply to gasification of high ash melting points coal. The feasibility and the key difficulty of this technology are analyzed from the effect factors of gasification process. and then draw a conclusion that the technology has the characteristics of a wide range of fuel applicability, low oxygen consumption, high heat value of syngas, the more active content (CO+H2) in syngas, the more high overall process efficiency and molten ash extracted swimmingly and completely. It is likely that the pulverized coal with high ash melting point will be gasified commendably using the technology.

Experimental Investigation on Pressure Drop Profiles in a Swiss-Roll Combustor

Cold state experiment on a Swiss-roll combustor was performed. The effects of wind speed and the number of channels on pressure drop were tested. Results showed that the pressure in the channels of the combustor increase with the increase of the distance from the inlet of gas. The local resistance caused by the bend angle affects on-way resistance very much. The total pressure drop increases with the increase of the number of bidirectional countercurrent channels and wind speed. Within the experiment range, the correlation of total pressure drop and the wind speed show a nonlinear relationship between line and parabola. Based on the formulas of line resistance and local resistance, the flow resistance of the Swiss-roll combustor was described mathematically by a synthetical resistance coefficient. A pressure drop formula was developed by regression of experimental data. The calculation results from this formula agree well with the experimental data. It can provide reference to the design and operation of the burner. Meanwhile, the method can also be widely applied to researches on the flow resistance of multi-elbow structures used in the electrical, water conservation and chemical industries.