Titanium tetrachloride silica control via feedback feed-forward
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Solution Overview
Problem
The existing processes for manufacturing titanium tetrachloride in fluidized bed reactors face challenges in controlling excess silicon tetrachloride and silica contamination, which affect the quality parameters of titanium dioxide products, such as particle size distribution and primary particle size.
Innovation Solution
A control process that analyzes the concentration of silicon tetrachloride in the gaseous stream, calculates the difference from a set point concentration, and adjusts the flow of titanium bearing material and chlorine into the reactor using feedback and feed-forward responses to maintain desired silica levels in the final product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional chlorination processes are used in fluidized bed reactors, then titanium tetrachloride is produced, but excess silicon tetrachloride and silica contamination occurs affecting product quality
Solution Approach 1:
The patent implements a feedback control system that continuously monitors silicon tetrachloride concentration in the reactor off-gas and adjusts the titanium bearing material feed rate accordingly. When SiCl4 concentration exceeds the setpoint, the system automatically reduces the feed rate to bring contamination back within specifications, creating a closed-loop control mechanism that dynamically maintains product quality.
Solution Approach 2:
The control system calculates a feed forward response based on historical data and process conditions to proactively adjust the titanium bearing material feed rate before excessive silicon tetrachloride formation occurs. This predictive approach prevents contamination rather than merely reacting to it, by anticipating trends in SiCl4 generation based on operational parameters.
2Productivity
If titanium bearing material feed rate is increased to maintain production, then productivity is improved, but silicon tetrachloride concentration increases affecting product purity
Solution Approach 1:
The patent employs dynamic control of the titanium bearing material feed rate rather than a fixed rate. The system continuously adjusts the feed rate based on real-time SiCl4 concentration measurements and process conditions, allowing the reactor to operate at optimal productivity levels while dynamically adapting to prevent silica contamination excursions.
Solution Approach 2:
The control system modifies operational parameters (feed rate, and potentially other process variables) to maintain the optimal balance between productivity and product purity. By changing the feed rate parameter in response to SiCl4 concentration, the system achieves both high production rates and low silica contamination.
3Manufacturing precision
If manual control methods are used, then device complexity is low, but manufacturing precision and response time are insufficient
Solution Approach 1:
The patent replaces manual mechanical control with an automated control system that uses sensors, processors, and actuators. The system electronically monitors SiCl4 concentration and automatically adjusts the feed rate, substituting human operation with instrumented control to achieve superior precision and responsiveness.
Solution Approach 2:
The control system is self-regulating, automatically monitoring its own performance and making adjustments without external intervention. The system uses the off-gas analysis to self-correct silica contamination issues by autonomously adjusting the feed rate, eliminating the need for continuous manual monitoring and adjustment.
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 process effectively reduces silica contamination in titanium dioxide products, improving their quality by minimizing variability in particle size distribution and primary particle size, as demonstrated by a 51% reduction in standard deviation of SiO2 concentration in titanium dioxide samples.
Implementation Method 1
particulate coke, particulate titanium bearing materials, chlorine and optionally oxygen or air are fed into a reaction chamber, and a suitable reaction temperature, pressure and flow rates are maintained to sustain the fluidized bed
Implementation Method 2
Gaseous titanium tetrachloride and other metal chlorides are exhausted from the reaction chamber
Data Source
Figure 1
AI summary
This disclosure relates to process for controlling chlorination reactions in manufacturing titanium tetrachloride in a fluidized bed reactor, optionally followed by processing to form a titanium product comprising a minor amount of silica, the process comprising: (a) feeding carbonaceous material, titanium bearing material comprising an amount of silica, and chlorine to the fluidized bed reactor to form a gaseous stream, and condensing the gaseous stream to form titanium tetra-chloride, a non- condensed gas stream and a condensable product stream, wherein at least one of the titanium tetrachloride and the non-condensed gas stream comprise silicon tetrachloride; (b) analyzing the non-condensed gas stream, the titanium tetrachloride or both, to determine the analyzed concentration of silicon tetrachloride; (c) identifying a set point concentration of silicon tetrachloride based on the desired amount of silica in the titanium product; (d) calculating the difference between the analyzed concentration of silicon tetra-chloride and the set point concentration of silicon tetrachloride; (e) measuring the titanium tetrachloride flow to a processing reactor that releases chlorine; (f) measuring the flow of fresh chlorine added to the fluidized bed; (g) measuring the flow of the titanium bearing material added to the fluidized bed reactor and establishing a historic average flow of the titanium bearing material added to the fluidized bed reactor; (h) calculating the chlorine released from the titanium tetrachloride that is processed using the titanium tetrachloride flow data from step (e); (i) calculating the total chlorine flow to the fluidized bed reactor by adding the chlorine flow in step (f) to the chlorine flow calculated in step (h) and establishing a historic average chlorine flow; (j) calculating a unit titanium bearing material consumption per unit chlorine; (k) calculating an estimated current consumption rate of titanium bearing material based on the total chlorine flow from step (i) times the unit titanium bearing material consumption per unit chlorine from step (j); and (I) generating a signal based on difference generated in step (d) that provides a feedback response and combining this to the estimated current consumption rate of titanium bearing material from step (k) to provide a feed forward response to control the flow of the titanium bearing material into the fluidized bed reactor.