Slurry Injection Nozzle for Vertical Lift Dryer. Final Report. Series No. II: G-5.

摘要

The objectives of this study were to develop for the VLD a coal slurry injection nozzle and operating conditions that would (1) break slurry into fine spray within a short distance, (2) minimize impingement on pipe wall, (3) give positive momentum input to the hot gas stream for minimum pressure drop, (4) minimize erosion in the nozzle,and (5) retain the above capabilities through a significant turndown range in slurry feed rate. A test unit was constructed to study injection nozzles that would best meet these requirements. The selected nozzle is a straight tube with a 7-degree expansion or diffuser discharge section. The straight tube section has a minimum L/D of 4.5,the diffuser length is such that D sub 2 /D sub 1is 1.6. Injection spray nozzle tests were made with the nozzle design using water and coal slurry. Good shattering of the water or slurry was attained at liquid velocities of 80to 90ft/sec and a gas injection rate into the nozzle feed as low as 0.03weight percent of liquid feed. The 35weight percent slurry appeared to have better shattering characteristics and shorter jet breakup length than water alone. A 545-hour erosion test was made with the brass nozzle using 35% slurry at design velocity with a low rate of atomizing gas. Although the severity of the erosion shown by the test was aggravated by omission of a teflon spacer at the nozzle inlet, itemphasizes the necessity of using a hardened material in the nozzle and the design requirement for straight line flow into the nozzle. A modification of the Lienhard and Day correlation for aerodynamic breakup of jets was used to correlate the pneumatic shattering test data. A basis for design of the coal slurry injection nozzle was established. (ERA citation 04:025194)