Big Rexnord® Bucket Elevators Handle Product with Kid Gloves
at Australian Fertilizer Plant
CASE STUDY
High-capacity Rexnord bucket elevators are handling large loads while minimizing product damage an integrated phosphate fertilizer manufacturing operation in remote northwestern Queensland, Australia. Almost three years after they were installed, the Rexnord Hi-Load elevators continue to perform well under demanding operating conditions.
The world-class US$450 million Queensland Fertilizer Operations (QFO) is part of WMC Fertilizers Pty. Ltd., a wholly-owned Australian-based subsidiary in the WMC Limited group of companies. Its facilities include sulphuric acid, phosphoric acid and granulation plants that are among the largest of their kind in the world, producing up to one million tonnes of di-ammonium phosphate (DAP) and mono- aluminum phosphate (MAP) fertilizer annually.
The Queensland facilities transform mined phosphate rock into fertilizer by a series of chemical processes and reactions. The beneficiation plant converts rock into slurry by crushing, washing and de-sliming, grinding, and thickening. At the phosphoric acid plant, phosphoric acid is produced by combining the phosphate slurry from the beneficiation plant with sulphuric acid. The ammonia plant combines hydrogen extracted from natural gas and nitrogen from air to form liquid ammonia, a rich source of nitrogen.
Rexnord Hi-Load buckets and chain details are
typical of all four elevators at the facility.
At the granulation plant, phosphoric acid is combined with liquid ammonia in a carefully controlled atmosphere to form ammonium phosphate slurry. This slurry is then pumped into the granulator, where it forms granules of fertilizer that are dried, screened and coated.
As materials move through the granulation plant, they are lifted from one level to another at various stages of the process by four separate Rexnord Hi-Load bucket elevators. These are slow-running gravity discharge elevators, designed to minimize damage to the product. Two of the units have a capacity of 830 THP, the third has a capacity of 545 TPH, and the fourth has a capacity of 256 TPH.
The Rexnord elevators were chosen for this application based on their proven track record over decades of use in similar applications with large tonnages and delicate materials. Several features combine to make the elevators well-suited to this service. They have a high-position inlet chute that is designed to fill the buckets without overspill. This prevents excess material from falling into the base of the elevator, which would cause the buckets to “dig” and powder the granules. The buckets are driven by two strands of Rexnord chain and run slowly to help contain the product. The shape of the buckets themselves assists discharge, making it as clean as possible with minimal product damage.
The combination of large tonnages and the need for slow speed makes these elevators significantly larger in size than a typical cement or grain elevator, which commonly handles smaller tonnages and has a centrifugal discharge. Rexnord is one of only a handful of manufacturers worldwide that make machines this large.
Boot end of one of the four Rexnord bucket
elevators shows large access door.
As with all Rexnord bucket elevators, the QFO elevators are designed with large access doors and a low-maintenance gravity take-up system. Segmented sprockets and traction wheels facilitate replacement without the need to disturb the chain, and all headshaft components are secured with shrink discs instead of keyways, to avoid stress cracking.
4-154(7-126) CS/10-23-03
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