Safer uranium handling

One of the most hazardous aspects in the uranium mining stream is the processing, drying and crushing it to create yellowcake. 

However a new system has been devleoepd that takes the worker out of the process, raising safety and giving remote uranium operations a new edge. 

Adelaide Control Engineering (ACE) specialises in the design, manufacture, installation and commissioning of processing equipment for uranium mines. 

According to managing director, Glenn Jobling, innovative technology and advanced modular design has enabled ACE to reduce the build time and requirement for skilled labour at remote sites by almost 50 per cent, giving the company a sustainable competitive advantage internationally. 

"The ACE modular system based on standard shipping containers is built, assembled, and tested in our Australian manufacturing facility before transport to site," Jobling told Australian Mining

"The $11 million contract involves provision of a plant for dewatering, calcining and packing of yellowcake, complete with a waste gas scrubbing system. The processing system is fed with yellowcake slurry from the mine's primary processing plant. Slurry is dewatered in a centrifuge and then fed to a rotary kiln for drying. 

"From the kiln, the dried yellowcake powder is transferred to the packing module where it is packed into drums. A key design criterion for the fully automatic drum filling plant was that the risk of operator exposure had to be minimised. To achieve this, the drum filling and sampling system is contained within a sealed module, which has integral dust extraction." 

Jobling emphasised that this fully automatic system also provides a high level of product security. "No one has access to the product, which provides product security and ensures that all product is accounted for," he said.  

"Labels are printed automatically for all drums and drum samples with the details logged in a data base to account for all yellowcake. If required, the labels can incorporate barcodes for tracking and audit. 

"With the ACE system, the security and integrity of the product is ensured. When combined with sound site security, our design provides the best product security available. 

"Drums are carried into and out of the packing module on conveyors through entry and exit airlocks. When they enter the module, the drums are weigh checked, then filled, sealed, weighed, washed and dried before leaving the module. The drums can be loaded and unloaded from the conveyors by forklift operators without the need for personal breathing protection. 

"The automatic sampling system takes product at three intervals during the filling of each drum to give representative sample of the contents. These samples are placed into a laboratory jar, the lid is closed and the jar is transported out of the module for labelling.

"A second sampling sequence collects one sample from each drum and deposits it in a larger container to provide a composite sample from each batch of drums." 

Integrated platform 

Specialist suppliers for the project included NHP Electrical Engineering Products, SEW Eurodrive, Global Pumps, and Endress & Hauser, while construction assistance was provided by F Miller Fabrications, Sturns Mechanical Fabrication, and AEC for electrical work. 

Andrew Watts at NHP Electrical Engineering Products says the control system for the project is based around the Rockwell Automation ControlLogix hardware platform available from NHP.

This allowed sequential control, process control and safety functionality all to be deployed in a single integrated hardware platform. 

"The system also uses Rockwell Automation's PlantPax software for its visualisation software component. This system drastically reduces software engineering time by providing a standard library of instructions and visualisation faceplates," he explained. 

"The ACE project solution also heavily leverages Rockwell Automation's Ethernet/IP communication network. This single network is based around unmodified Ethernet (IEEE 802) and allows for SIL 3 PLe safety, HMI traffic and real time control on a single network. 

"Rockwell Automation's machine mounted historian, FactoryTalk Historian ME, is also used for the large scale collection of data from the plant. This data can then be analysed to allow for optimisation of the plant.  

"In addition, advantage is taken of Rockwell Automation's premier drive integration which allows for the complete configuration, control and backup of the systems' variable speed drives inside the Logix-based controllers. 

"The successful implementation of the Rockwell Automation solution was made possible by NHP's specialist automation team. Its expert knowledge of the product and desired application enabled ACE to fully experience the benefits of this platform." 

Darren Seeley at Global Pumps advises that Netzsch helical rotor pumps are used to provide centrifuge feed and concentrate return for the ACE project. 

"The product being pumped is gritty and abrasive slurry, so it's important to keep the pressure drop across each stage as low as possible. Experience has shown that the 2S geometry of these pumps works very well on yellowcake," he said. 

Grand plan 

Jobling says the company plans to remain globally competitive by further improving and standardising the modular plant design. 

"Custom building requires expensive project specific design which significantly increases costs. By building a standard design, quality improves, delivery and commissioning time is reduced and cost can be cut by as much as 25 per cent," he explained. 

"The cost benefits also extend to the site building. Because each module is its own structural unit, complex and expensive buildings are not required to house the plant. All modules can sit at the same level and be housed in a very simple building. The modules can also be easily relocated to another mine should the deposit be mined out. 

 "We are also continuing to innovate with the development of our horizontal kiln for yellowcake calcining/drying to enable production of larger crystals of a more consistent size with less dust. This increases product recovery and reduces risk of contamination, and the technology can be used for other minerals, not just uranium.  

"ACE can also provide the technology and hardware for the continuous fluid bed precipitation of yellowcake. As with our drying/calcining and packing plant, the fluid bed precipitation plant can be provided as modular units based on standard shipping containers for pilot or satellite plants." 

Jobling points out that continuous fluid bed precipitation provides several advantages over standard tank methods.

"These include up to 25 per cent lower cost of production with reduced maintenance, increased recovery of uranium, and reduced fines creating less dust and consequently lower risk to operators.

"There is also an increase in product bulk density giving reduced transport costs and as much as 40 per cent improvement in dewatering which reduces drying costs," he said.  

 

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