Preparation of titanium liquid

Titanium white powder in the production of sulfuric acid in the first step is first decomposed solid titanium iron ore is prepared as a soluble titanium sulphate solution by acid, while the majority of ilmenite and iron impurities into soluble metal sulfate Salt to separate various impurities later. Since ferrous iron ferrite (ilmenite) is a weak acid weak base salt, the reaction with a strong acid (H ₂ SO ₄ ) is essentially irreversible and the reaction can be carried out relatively completely.

The acid decomposition (abbreviated as acid hydrolysis) of ilmenite has a dry method and a wet method. The dry method is to mix the ground ilmenite with sulfuric acid for heating and roasting. After the decomposition is completed, the water is diluted and leached to obtain a titanium sulfate solution. This method cannot be used for large-scale industrial production, and it is sometimes used in the preparation of a titanium sulfate solution in a laboratory.

The wet method is currently the sulfuric acid method commonly used. From the history of development, the wet method has had five different methods: liquid phase method, solid phase method, two-phase method, pressurization method and continuous method.

Liquid phase method : The reaction is always carried out in the liquid phase. Here, the ratio of the concentration of sulfuric acid (effective acid) to the total titanium content is very important, called the acid ratio, and is usually expressed in terms of F. The ratio of 55% to 65% of sulfuric acid is higher (F value is 3 to 3.2), so most of the obtained titanium liquid exists in the form of titanium orthosulfate-Ti(SO ₄ ) ₂ . Because the reaction time is too long, the acid consumption and steam consumption are too high, and the F value is too high, so that the hydrolysis is difficult later, the hydrolysis rate is low, and the industrial production generally does not adopt this method. The test proves that even if the concentration of sulfuric acid in the liquid phase is only 10%, the titanium sulfate solution can be obtained, but the reaction time is longer because the boiling point of 10% sulfuric acid is only 10 ° C, and the reaction rate is 98 ° C for 8 h, and the acid hydrolysis rate is only 30%.

Two-phase method : the concentration of sulfuric acid used in the two-phase method is 65%~80%, and the F value is controlled between 1.8~2.2. When operating, the sulfuric acid is first heated to about 120 °C, then the mineral powder is added and the stirring is heated to 150~200. °C, the main reaction for 3h, the reactant is a paste, followed by cooling, water leaching to maintain a certain concentration of the suspension until the acid hydrolysis rate reaches 85% to 90%. Although the two-phase method consumes less sulfuric acid than the liquid phase method, the reaction time is long and the acid hydrolysis rate is low.

Solid phase method : This method is a commonly used method in the current sulfuric acid titanium dioxide factory because it has the advantages of high reaction temperature, short reaction history and low consumption of sulfuric acid compared with the former two methods. The concentration of sulfuric acid produced by this method is generally 85%~95%, and the reaction is intense and rapid. Due to the high boiling point of concentrated sulfuric acid, the maximum reaction temperature can be as high as 200~250°C, and the reaction can be completed within 5~15min. A large amount of heat is released, so the energy is less, the acid consumption is less, and the F value is generally controlled by 1.7 to 2.1. The obtained product is a porous solid phase, which is easy to be added with water, and the acid hydrolysis rate can usually reach 95% or more.

Pressurization method : Dilute sulfuric acid with a concentration of 20% to 50% is used in a corrosion-resistant pressure-receiving device. This method is sometimes used for the production of synthetic rutile or rutile for welding electrodes.

Continuous process : This method uses a mixed acid of fuming sulfuric acid and 20% sulfuric acid to prepare a semi-fluid reactant and then solidify at a high temperature. The pressurization method and the continuous method have high requirements on the material of the reaction equipment, and the operation is complicated, and has not been adopted in the production of industrial titanium dioxide.