Uniforming mass flow rate of PCI into BF tuyeres with choking phenomena

Extending the concept of choking phenomenon in aerodynamics to compressible gas-powder two-phase flow, an approach for uniforming the mass flow rate of pulverized coal injection into blast furnace tuyeres was developed with extensive experimental study on choking phenomenon of air-coal two-phase flow. The experimental results verified that, as long as choking of the gas-particle flow is developed at the nozzles of the same orifice on the pipeline between the distributor and tuyeres, the gas-powder flow will attain its apparent sonic velocity, and uniform mass flow rate of powder into each tuyere can then be obtained. The critical pressure ratio for attaining the choking state was also determined for various powder/gas ratios of the two-phase flow, and thereby the rules were established for the selection of choking nozzle and carrier gas pressure.