Process flow sheets: Aluminium Sulphite

Process Description

The manufacturing of alums entails just one step additional to the aluminium sulphate process. Practically all alums and aluminium sulphates are now made-from bauxite by reaction with sulphuric acid. The bauxite ore is crushed to a fine powder until 80% passes through 200-mesh; next it is conveyed to storage bins. The reactants are thoroughly mixed and heated with the aid of agitators and live steam in lead lined steel tanks. These reactors are operated in series. In the last reactor, barium sulphide is added in the form of black ash to reduce ferric sulphate to the ferrous and to precipitate the iron. The mixture from the reactors is sent through a series of thickeners. The residue is washed to remove the alum from the residue. The clarified aluminum solution is concentrated in an open, steam coiled heated evaporator from 35^o to 59^o or 62 ^oBe. The concentrated liquor is poured into flat pans, where it is cooled and completely solidified. The solid cake is broken and ground to size for dispatch in bags.

Practically the waste to be generated from the production process of alum is any sulphuric acid leak. So containment concrete vessel is built and the content will be neutralized by using caustic soda before disposal.

Production process

Prepare 35% kaolin suspension in a reactor and add proportional amount of sulfuric acid. The leaching process is to be conducted at 145-150^oC at 0.45 atm. for 4-6 hours. The post suspension in the reactor tank is agitated at 80^oC and then filtered by filter press at 200 bars. The liquid and solid part is separated by filtration; the solid part (filter cake) is silica sand, which is the byproduct. The filtrate is a mixture of aluminum oxide and aluminum sulphate. The aluminum sulphate is separated from the oxide by evaporating at 113^oC and crystallizing.

The liquid waste to be generated due to leakage of pipes and vessels and washing of the production facility is collected in a concrete made containment vessel. The content will be neutralized by checking its PH and adding caustic soda till it becomes neutral and safe for disposal.

Production video