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SpectraFlow Analytics Switzerland received an order though their partner Precision Light and Air, Nanjing, China to supply a NIR online Crossbelt analyzer for Chalco’s Huasheng Bauxite refinery.

Chalco desires to have a clearer picture of the bauxite quality feeding to the process to optimize the liquor dosing in real time with the goal optimize the recovery of available alumina in their process whilst avoiding increased silica.

About Chalco:

Aluminum Corporation of China Limited (Chalco), incorporated on September 10th, 2001 in China, is a leading company in China’s non-ferrous industry and the only large company in China’s aluminum industry that’s engaged in the whole value chain, from exploration and mining of bauxite and coal, production, sales and R&D of alumina, primary aluminum and aluminum alloy products, to international trade, logistics, and power generation from both fossil fuels and new energy.

Currently Chalco produces 17.95 Mio t p.a. alumina oxide in its various refineries, which makes them the second largest player worldwide.

At Chalco’s Huasheng refinery, located in Fangchenggang City, Guangxi province. The plant receives about 6 million tons p.a. Bauxite. The incoming material is stockpiled in a storage shed before being transported to the Bayer Process. The bauxite is transported to the feed hoppers for the 3 mills. The SpectraFlow analyzer will be installed over the main conveyor to monitor the feed quality to and from the Bayer Process.

Figure 1 - SpectraFlow Crossbelt Analyzer in the Chalco's Huasheng aluminium refinery process.

The goal for Chalco with the implementation of the SpectraFlow online analyzer is to have real time information on Al2O3, Available Alumina, SiO2, Reactive Silica, Fe2O3, TiO2, Total Carbon and Sulphur. With given concentration of the bauxite slurry, the total alumina in the bauxite should be a fixed number, and customer can calculate the amount of alumina that should be digested out of the bauxite, with a stable process condition for a digestion rate. This way the yield will be ensured. However, when the available alumina in the bauxite varies, the concentration of bauxite slurry pumped into digestion system needs to be adjusted correspondingly. The main consideration for the feed quality control is the silica concentration, which is essential in the slurry preparation as part of the silica reacts with caustic. This leads to changes to the digestion rate.

Chalco will use the results measured by SpectraFlow, most importantly available alumina and reactive silica, to ensure optimal digestion by adjusting the caustic liquor addition at the mill and digestion feed location in real time. The measurement results of other components, such as carbon and sulfur, can be used by customers to adjust the back-end process and stabilize the balance of organic matter throughout the Bayer Process.

The original idea from Chalco was to use a sampling system. Yet, with the high throughput it is not possible to ensure representativity of the samples and the significant time delay makes process optimization based on sampling inefficient. Another point to consider is the high work load on the laboratory if data needs to be available in high frequency and fast.

Therefore, only an online analyzer could be used. Chalco selected NIR technology due to the significant advantage over conventional elemental analyzer that SpectraFlow is the only online minerals analyzer, which allows the analysis of minerals as well as organic components and moisture in one system (detector). Therefore, SpectraFlow can measure total Al2O3 vs. available alumina and total SiO2 vs. reactive silica directly, without the use of any calculations.

SpectraFlow Installation for Advanced Process Control (APC):

The SpectraFlow analyzer is an online analyzer that measures dry raw material composition at key points in mining, processing and refining value chains. Usually placed over a conveyor belt, or in an airslide, the analyzer is able to measure fine deviations in the moisture, grade or gangue composition of the material in real time. By using the measurements from the analyzer that are exchanged directly with the control room PLC or from SpectraFlow’s database and monitoring user interface, bulk mineral, precious metal and cement producers can create automated control loops for quality control and assurance of their final product.

The summarized benefits of SpectraFlow’s online NIR analyzer are:

  • The analyzer is free of any radioactive sources, neutron generators or any hazardous components. This means the SpectraFlow analyzer does not require any permits or licenses regarding importation, operation or maintenance. This also means that the SpectraFlow analyzer is completely safe, maintenance can be done by the plant personal.

  • Real time, short acquisition time measurements of the complete flow of material gives the customer the opportunity to provide high resolution feed forward information to downstream processing or make value-based ore sorting control decisions on the material.

  • The Crossbelt Analyzer reduces the need for frequent belt cuts or manual sampling of the material for quality control, and instead gives the user the user large amounts of accurate composition data for real time feedback on upstream quality delivery like ore block control and stockpile blending.

With this new order SpectraFlow is now supplying analyzer to the major global alumina companies of South32, Emirates Global Alumina (EGA) and Chalco.

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