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

摘要

A method for co-producing alumina and activated calcium silicate from high-alumina fly ash, comprising the steps that: high-alumina fly ash reacts with sodium hydroxide solution to obtain desiliconized solution and desiliconized fly ash; milk of lime is added to the desiliconized solution to obtain activated calcium silicate; limestone and sodium carbonate solution are added to the desiliconized fly ash to blend raw slurry, the raw slurry is baked into clinker, and sodium aluminate crude solution is obtained from dissolution of the clinker; the sodium aluminate crude solution is subjected to the processes of first-stage deep desiliconization, second-stage deep desiliconization, carbonization decomposition, seed precipitation and etc to obtain alumina. According to the invention, less material flow and small amount of slag formation are achieved, the energy consumption, material consumption and production cost are low; the extraction rate of alumina is high, and meanwhile, activated calcium silicate with high added value is co-produced.

主权项

1. 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.