Performance Research On New Atmospheric Continuous Coal Gasifier

Nowadays,the traditional atmospheric fixed bed gasifier is used by most of the domestic small and medium sized chemical companies, which belongs to the phase-out type of coal gasification technology and needs to be improved. The atmospheric dry pulverized entrained flow gasifier is considered to be more reasonable type for improvement through analysis and comparison.The software ANSYS was used in this thesis. Firstly, the cold model numerical simulation research was conducted on the atmospheric dry pulverized rotated tetra-burner entrained flow gasifier and the atmospheric dry pulverized opposed tetra-burner entrained flow gasifier with the flow field and particle residence time distribution achieved and the effect of different operating parameters(inlet velocity, particle diameter, particle density) and structural parameters(jet height, combustion chamber height, outlet diameter) on particle residence time distribution studied. It can be seen that:The central symmetric rotational gradient field occurs in the rotated tetra-burner gasifier with higher velocity outside and lower velocity inside. Two larger recirculation zones occur around the jets with smaller zones upside and larger zones underside, which are formed by the upper and lower streams in the central collision zone of the opposed tetra-burner gasifier. Most of the particle trajectories are concentrated in the zones with larger turbulence intensity and turbulence kinetic energy. The particle mean residence time tm and the particle lag time τ decrease with the increase of the inlet velocity V, the particle diameter d, the particle density ρ and the outlet diameter D. Besides, the tm and τ experience a more significant decrease with the increase of d than ρ. Moreover, there is an increase in the tm and τ with the increase of the combustion chamber height H0. In addition, the tm and τ go up and down with the increase of the distance between jet and top H and when the H is 1150 mm, the tm and τ peak at 8.60 s and 2.25 s respectively. Furthemore, under the same conditions the tm and τ in the opposed tetra-burner gasifier are larger than those in the rotated tetra-burner gasifier.Moreover, the thermal model numerical simulation research on the atmospheric dry pulverized ceiling burner entrained flow gasifier and the atmospheric dry pulverized opposed tetra-burner entrained flow gasifier was conducted with the flow field, temperature field and concentration field achieved and the evaluation indicator of gasification performance studied based on the simulation results. It can be seen that:The effective gas content at the outlet of the ceiling burner gasifier is 61.8%, the carbon conversion rate is 93.00%, the gas yield is 2.44Nm3/kg and the cold gas efficiency is 74.45% by calculation. The effective gas content at the outlet of the opposed tetra-burner gasifier is 62.2%, the carbon conversion rate is 93.75%, the gas yield is 2.46Nm3/kg, the cold gas efficiency is 75.39%. It can be seen that the effective gas content at the outlet, the carbon conversion rate, the gas yield and the cold gas efficiency in the opposed tetra-burner gasifier are superior to those in the ceiling burner gasifier by comparison.Finally, the thermal model optimization analysis on the atmospheric dry pulverized opposed tetra-burner entrained flow gasifier was conducted and the effect of different operating parameters(water vapor flow, oxygen flow, average particle diameter, particle density) and structural parameters(outlet diameter, jet height) on the evaluation indicator of gasification performance was studied. It can be seen that:The increase of the water vapor flow is beneficial to improve the effective gas content at the outlet and the cold gas efficiency of the opposed tetra-burner gasifier with remaining a certain carbon conversion and gas yield as the precondition.Although it is favorable for the improvement of the carbon conversion and the gas yield to increase the oxygen flow of the gasifying agent, the effective gas content at the outlet and the cold gas efficiency of the opposed tetra-burner gasifier reduce and the specific oxygen uptake increases. To sum up, the oxygen flow of 4375Nm3/h is more reasonable with the corresponding effective gas content at the outlet of 62.2%, the carbon conversion rate of 93.75%, the gas yield of 2.46 Nm3/kg and the cold gas efficiency of 75.39%.The decrease of the average particle diameter, the particle density and the outlet diameter is advantageous to improve the effective gas content at the outlet of the opposed tetra-burner gasifier, the carbon conversion rate, the gas yield and the cold gas efficiency with the promise of the coal grinding process, the promise of the equipment and no influence on the normal slagging of the opposed tetra-burner gasifier as the precondition.When the distance between jet and top is 1150 mm, the effective gas content at the outlet of the opposed tetra-burner gasifier, the carbon conversion rate, the gas yield and the cold gas efficiency peak at 64.5%, 96.1%, 2.50Nm3/kg and 79.38% respectively.