Bauxite Beneficiation Electrostatic

The most widely used chemical process of refining bauxite into alumina, the Bayer process, involves dissolving the Al2O3 out of the bauxite rock with caustic soda (NaOH) at elevated temperature and pressure. The Al2O3 fraction of the bauxite is dissolved into solution, to later be precipitated out as alumina. Heoi, a high-grade bauxite contains up to 60% Al2O3, and many operating bauxite deposits are well below this, wā rite iti rite 30-40% Al2O3. Because the desired product is a high purity Al2O3, te toe waikura i roto i te bauxite (Fe2O3, SiO2, TiO2, Organic material) are separated from the Al2O3 and rejected as alumina refinery resides (faanahohia) or red mud. I roto i te whānui, te kounga o raro te bauxite (ie lower Al2O3 content) the more red mud is generated per ton of alumina product. I tua atu, even some Al2O3 bearing minerals, pērā kaolinite, produce un-desirable side reactions during the refining process and lead to an increase in red mud generation, me te te mate o te utu matū konutai waihā, he utu tāupe nui i roto i te tukanga para bauxite.

paru Whero fokotu'utu'u ranei tohu te nui, me te i runga i-haere wero mo te ahumahi konumohe. Kei paru Whero waihā wäriu toenga matū nui i te tukanga para, a ko tino kawakore, maha ki te pH o 10 - 13. It is generated in large volumes worldwide – according to the USGS, tata production alumina ao ko 121 miriona toni i roto i 2016. This likely resulted in more than 150 miriona toni o paru whero hangaia i roto i te wā kotahi. Ahakoa rangahau haere tonu, paru whero tēnei wā he torutoru ara arumoni taea ki painga re-whakamahi. Kei te tata te reira e iti rawa o te paru whero ko nga painga o re-whakamahia te ao. Instead the red mud is pumped from the alumina refinery into storage impoundments or landfills, te wahi e rongoa ai, ka aroturuki i te utu nui.

Ko te mate o te konutai waihā utu (NaOH) and the generation of red mud are both related to the quality of the bauxite used in the refining process. I roto i te whānui, the lower the Al2O3 content of the bauxite, te nui te rōrahi o te paru whero kia e ka hanga, as the non-Al2O3 phases are rejected as red mud. I tua atu, the higher the kaolinite or reactive silica content of the bauxite, ka te paru atu whero kia hanga. The reactive silica content not only increases the volume of red mud, but also consumes caustic soda reagent and reduces the yield of Al2O3 recovered from the bauxite. Na reira, there is both an economic and environmental argument to be made for improving the quality of bauxite prior to refining.

Ko te tukanga STET maroke wehenga e horo'a bauxite kaihanga ranei kaimahi koura bauxite ha faingamālie ki te mahi i mua-Bayer-tukanga whakahoutanga o te ore bauxite ki te whakapai ake i te kounga. He maha ngā painga tenei huarahi:

• Whakaitinga i roto i te utu whakahaere o whakatere whakapai e tika ana ki te kohi raro o te konutai waihā mā te whakaiti tāuru takawai urupare.
• Savings in energy during refining due to lower volume of inert oxides (Fe2O3, TiO2, Non-reactive SiO2) tomo ki te bauxite. Smaller mass flow of bauxite to refinery results in less energy to heat and pressurize.
• Reduction in red mud generation volume (ie – paru whero ki alumina ōwehenga) by removing reactive silica and inert oxides.
• Tighter control over input bauxite quality to refinery reduces process upsets and allows refiners to target ideal reactive silica level to maximize impurity rejection.
• Improved quality control over bauxite feed to refinery reduces process upsets, maximizes uptime and productivity.
• Reduction in red mud volume translates into less treatment and disposal costs and better utilization of existing landfills.
• Haunga te paru whero, tailings i te tukanga hiko maroke i roto i kahore matū, me te kore e tohu i te taunahatanga rokiroki taiao wā roa-.
• Haunga te paru whero, dry by-products/tailings from a bauxite processing operation can be utilized in cement manufacture as there is no requirement to remove the sodium, i te mea tuukino ki sima hanga. I roto i te meka – Bauxite is already a common raw material for Portland cement manufacturing.
• Extend operating life of existing bauxite mine by improving quarry utilization and maximizing recovery.
• STET is a low operating cost, high throughput continuous process. No water or chemicals required.