Overcoming obstacles in smelter debottlenecking - experience of a primary zinc smelter.

The Avonmouth Imperial Smelting blast furnace and sintering plant were uprated in 1988, but zinc production in the following 12 months was only 85 000 tonnes and only by 1992 was a rolling 12-month production of 110 000 t consistently achieved. There were initial shortages of sinter due to an offset in uprate timing. Greater difficulties were experienced in operating the larger furnace, particularly on start-up: there were serious slagging problems and a greater tendency for iron production. Deleterious trends in slag chemistry were coincidental. There were refractory problems in the shaft furnace and condenser. Problems in commissioning the wet gas and sinter tip end fans, and difficulties in obtaining sufficient sinter hardness, resulted in shortages of sinter. The full benefits of the sinter-acid plant uprate were not realised due to a late change in design to dispense with sinter gas recirculation, though this was offset by successful use of oxygen. The problems have largely been overcome by a determined attack on their true causes. Data analysis is now more thorough, action taken more cautious, monitoring used more extensively and external advice sought more readily. Furnace zinc output capacity is planned to rise to 120 000 t/y within two years.
The Avonmouth Imperial Smelting blast furnace and sintering plant were uprated in 1988, but zinc production in the following 12 months was only 85 000 tonnes and only by 1992 was a rolling 12-month production of 110 000 t consistently achieved. There were initial shortages of sinter due to an offset in uprate timing. Greater difficulties were experienced in operating the larger furnace, particularly on start-up: there were serious slagging problems and a greater tendency for iron production. Deleterious trends in slag chemistry were coincidental. There were refractory problems in the shaft furnace and condenser. Problems in commissioning the wet gas and sinter tip end fans, and difficulties in obtaining sufficient sinter hardness, resulted in shortages of sinter. The full benefits of the sinter-acid plant uprate were not realised due to a late change in design to dispense with sinter gas recirculation, though this was offset by successful use of oxygen. The problems have largely been overcome by a determined attack on their true causes. Data analysis is now more thorough, action taken more cautious, monitoring used more extensively and external advice sought more readily. Furnace zinc output capacity is planned to rise to 120 000 t/y within two years.