Multi-stage TiCl4 Oxidation for TiO2 Particle Size Control
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Solution Overview
Problem
Existing multi-stage methods for manufacturing titanium dioxide using the chloride process result in increased mean particle size due to favored surface reactions, requiring corrosive growth inhibitors to counteract this effect, leading to equipment corrosion and increased maintenance.
Innovation Solution
A multi-stage method where liquid titanium tetrachloride is introduced in a first stage with an excess of preheated oxygen to form fine TiO2 particles, which act as nuclei for subsequent growth, and gaseous TiCl4 is introduced in later stages, optimizing the molar ratio of O2:TiCl4 to control particle size without the need for growth inhibitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If gaseous TiCl4 is introduced in all stages, then the reaction proceeds efficiently, but the mean particle size increases due to favored surface reactions
Solution Approach 1:
The patent segments the TiCl4 introduction process into two distinct stages: liquid TiCl4 in the first stage for nucleation, and gaseous TiCl4 in subsequent stages for controlled growth. This segmentation allows different physical states to serve different functional purposes in the particle formation process.
Solution Approach 2:
The patent changes the physical state parameter of TiCl4 from liquid to gas between stages, and optimizes the molar ratio of O2:TiCl4 in each stage. These parameter changes enable precise control over particle size while maintaining reaction efficiency.
2Manufacturing precision
If growth inhibitors are added to control particle size, then particle size is reduced, but equipment corrosion increases
Solution Approach 1:
The patent converts the potentially harmful effect of uncontrolled particle growth into a beneficial process feature by using liquid TiCl4 droplets as controlled nucleation sites. This eliminates the need for corrosive growth inhibitors while achieving precise particle size control.
Solution Approach 2:
By changing the physical state of TiCl4 and optimizing the O2:TiCl4 molar ratio, the patent achieves particle size control through process parameters rather than chemical additives, thereby avoiding equipment corrosion.
3Manufacturing precision
If liquid TiCl4 is used in the first stage, then fine TiO2 particles are formed, but the reaction requires higher preheating
Solution Approach 1:
The patent segments the heating and reaction process into stages, with intensive preheating and liquid TiCl4 injection only in the first stage. Subsequent stages use gaseous TiCl4 that requires less heating, as the reaction zone is already hot from the first stage.
Solution Approach 2:
The patent performs preliminary intensive heating and liquid TiCl4 injection in the first stage to create fine nuclei. This preliminary action establishes the particle size foundation, allowing subsequent stages to proceed with less heating and gaseous TiCl4.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method produces finer TiO2 particles, reducing the need for growth inhibitors and minimizing equipment corrosion, allowing for precise control of particle size and energy savings by utilizing the reaction heat in later stages.
Implementation Method 1
liquid titanium tetrachloride is reacted with an oxidising gas, such as oxygen
Implementation Method 2
the oxidation reaction is highly exothermal, meaning that, following complete, adiabatic conversion, the temperature of the product stream is roughly 900° C. higher than that of the educts
Implementation Method 3
gaseous TiCl4 is fed into the gas suspension containing the initial TiO2 particles in a second stage
Implementation Method 4
The rest of the educts is added to the second stage after just slight heating, or even without heating. There, the educts are heated by the reaction enthalpy released in the first stage
Implementation Method 5
liquid titanium tetrachloride is used in the first stage... a gas suspension containing initial TiO2 particles is formed
Implementation Method 6
the molar ratio of O2:TiCl4 is greater than 1 and a gas suspension containing initial TiO2 particles is formed
Data Source
AI summary
The invention relates to manufacturing titanium dioxide by oxidizing titanium tetrachloride by a multi-stage method, where liquid titanium tetrachloride is used in a first and gaseous titanium tetrachloride is used in a second stage. The process is energetically more favorable and offers the possibility, to a certain extent, of controlling the mean particle size of the end product.