Raw materials Aluminium trihydrate is purified from bauxite. Commercial bauxite (30-75% Al2O3) deposits occur in Australia, Jamaica, France, Guyana, Guinea, the USA and Brazil. Bauxite ore is dissolved in strong caustic soda to form sodium aluminate. The aluminium trihydrate is then precipitated by neutralisation (usually with carbon dioxide) or by autoprecipitation (the Bayer process). The other raw material, sulfuric acid, is manufactured for superphosphate production at Farmers Fertiliser Ltd. Acid arrives by road tanker and is pumped into storage tanks.
Step 1 – Reacting the raw ingredients. The aluminium trihydrate is transported and stored in one tonne bags. Each bag is carried by hoist to the feed hopper, where it is opened and conveyed to the reaction tank. The reaction water, trihydrate and sulfuric acid batch is stirred for a period of time with water vapour exiting through the stack.
Step 2 – Making the final product After the reaction period either liquid or solid alum is made. If liquid, the concentrated batch is run into the dilution tank filled with the dilution water where it cools over time. The liquid alum is then filtered and pumped to storage. There are overhead load out facilities at Morrinsville where a number of liquid chemicals are available in dispatch tanks for road tankers. If solid is made, the concentrated alum is run into the casting pans where it sets, aided by fan cooling. The pans are forklifted to storage racks and from there they are taken to the Crushing Plant and dropped into a hopper. The pieces are broken further by a large kibbler followed by a small kibbler and then screened. Oversize particles go to a bagging hopper and are sold as kibbled product. The screened alum is rotary crushed and further screened to either return to the rotary crusher or be bagged as ground product. Dust is continually collected through an extraction system and is sold as product. The Crushing Plant is flexible and the ratio of kibbled to ground aluminium sulfate is variable.
Post time: Feb-18-2022