Method for co-producing alumina and activated calcium silicate from high-alumina fly ash

A method for co-producing alumina and activated calcium silicate from high-alumina fly ash, comprising the following steps:

• 1) high-alumina fly ash and sodium hydroxide solution are mixed, then heated up and introduced into a pressure container for desiliconization reaction, and liquid phase desiliconized solution and solid phase fly ash filter cake are obtained by liquid-solid separation;
• 2) preparation of activated calcium silicate, which comprises the following steps:
• a. milk of lime is added to the desiliconized solution for reaction, to obtain calcium silicate filter cake by filtering;
• b. the calcium silicate filter cake is washed and then added to clean water to prepare a calcium silicate slurry, and milk of lime is added to the calcium silicate slurry for dealkalization reaction;
• and
• c. calcium silicate obtained from the dealkalization reaction is washed with clean water and then added to dilute sulfuric acid for an initial soaking to obtain an initial soaking mixture;
• aluminum sulfate is added to the initial soaking mixture to decrease the pH to be below 10, further soaking of the calcium silicate is then performed;
• and activated calcium silicate is obtained after washing, deslagging, filtering and drying the further soaked calcium silicate;
• 3) sodium carbonate, limestone and/or quick lime solution are added to the fly ash filter cake to obtain a mixed slurry, and the mixed slurry is finely milled and blended into a raw slurry;
• 4) the raw slurry is baked into clinker;
• 5) the clinker and a first-stage regulating solution are mixed for first-stage dissolution to obtain a sodium aluminate crude solution and first-stage dissolution crude slag, the first-stage regulating solution contains the following ingredients:
• 10-60 g/L of Na2Ok, and 10-60 g/L of Na2Oc;
• 6) sodium hydrate alumino-silicate seed crystal is added to the sodium aluminate crude solution for first-stage deep desiliconization to obtain a first-stage desiliconized refined solution, then a part of the first-stage desiliconized refined solution is subjected to second-stage deep desiliconization to obtain a second-stage desiliconized refined solution and second-stage deep desiliconization slag simultaneously;
• 7) the second-stage desiliconized refined solution is subjected to carbonization decomposition to obtain aluminum hydroxide as seed crystal, the aluminum hydroxide is added to the first-stage desiliconized refined solution, which is not subjected to second-stage deep desiliconization, seed precipitation is carried out to obtain aluminum hydroxide, and alumina is obtained by baking the aluminum hydroxide.