Basic investigations on burner design for high pressure entrained flow gasifier: Influence of pressure and fluid viscosity on twin fluid atomization

摘要

The conversion of low-grade fossil and biogenic fuels to a high quality chemical energy carrier (syngas) in high pressure entrained flow gasification process opens a wide spectrum for energy efficient fuel conversion. The syngas can be converted to methane (SNG), liquid fuels (BtL/CtL) or it can be fired in a gas turbine of a combined cycle power plant (IGCC) to produce electricity and heat with high efficiency. This so called poly-generation gives maximum operational flexibility combined with fuel- and product flexibility at high energetic efficiency. Currently such a thermochemical process is being tested on a pilot scale at KIT. The so called bioliq process produces synthetic fuels out of residual biomass (BtL) [1]. The operation of a technical entrained flow gasifier aims for complete fuel conversion into a tar-free syngas at minimum oxygen consumption, i.e. maximum cold gas efficiency. Oxygen as the gasification agent also serves as atomization agent in the commonly applied twin fluid nozzles. Based on the required stoichiometry for the gasification reaction there is only a limited amount of atomization agent available (low gas to liquid ratio, GLR) for slurry fed and oxygen blown entrained flow gasifiers. As the droplet size distribution generated by the burner has a significant influence on the fuel conversion and the synthesis gas quality [2], a fine and homogenous spray of high viscous suspension fuel (slurry) has to be generated with minimum amount of atomization agent. For optimization of design and scale-up of the burner nozzle, fundamental knowledge concerning the atomization behavior of pumpable high viscous, non-Newtonian slurries at high process pressure is necessary. In this context, the present work focuses on the influence of the physical liquid properties (dynamic viscosity, Newtonian and non-Newtonian rheological behavior) and the operational parameters (reactor pressure, GLR, gas velocity) on the spray quality generated by a twin-fluid atomizer.