Australian Alumina Plant

Australian Alumina Plant

APPLICATION

Process

Liquor burning process in alumina refinery

Temperatures

Process - 900°C (1652 °F) Extraction – 200°C (392°F)

Particulate nature

Abrasive

Filter media

High temperature PTFE membrane bags

PROBLEM

Filter life was below 6 months due to high abrasion on elements. Frequent filter failures led to emissions and action by local EPA + negative media.

Site chose to replace filter media with ceramic filter elements


Replacement of media with ceramic filter elements was a large investment that led to a significant problem:

The filter cleaning system design was not considered when the media was changed. The consequence of higher dP through the filter elements was that the filter flow rates could not be reversed, and no cleaning factor was generated. DP rose to over 4kPa (16 “WG) Filters could only be cleaned off line, causing damage to the kiln, and a cost of over AU$30K each week.
graph 1

Poor cleaning system design = negative cleaning overpressure NO CLEANING.


Cleaning system was modified:

Goyen evaluated several changes to improve the cleaning performance using the GOCO software, computational fluid dynamics, and the test facility. Testing and modelling showed that the combination of the GOCO nozzles and venturis increased the cleaning overpressure so significantly that the pulse cleaning system operating pressure could be reduced. The plant was able to resolve the high dP problem and reduce the electricity consumption of the liquor burner (via fan power reduction and air compressor savings), and eliminate downtime.
graph 2

Ample cleaning power, easily adjusted by compressed air pressure level. 12


Some key considerations when configuring cleaning systems for Hot Gas applications:

Pulse valve choice

•What is the temperature at the valve; will high temperature seals (eg Viton) be required?
•Are aggressive chemicals in contact with the valve?
•Do we need stainless steel components rather than cast aluminium (standard)
 

Media dP

•What will the filter media be? Can we expect higher than usual differential pressures?
•What is the dP required to maintain the dust cake at the appropriate levels?
 

Waste gas and dew point

•Does the waste gas contain contaminants that may turn to an acid when the system passes through the dew point (eg during shut down periods)?
•Acid condensation on pulse system components will considerably shorten the life of these

 

Download Literature

Literature

Filter Cleaning in Hot Gas Applications download - copia

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