Titanium Etching Bath Regeneration via Sodium Salt Precipitation
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Solution Overview
Problem
Chemical machining baths used for titanium and its alloys in the aeronautical industry face issues with titanium concentration buildup, leading to reduced effectiveness and potential for intergranular corrosion, necessitating frequent bath replacement and disposal of expensive and hazardous acids, which is environmentally and economically costly.
Innovation Solution
A regeneration process using sodium salts (NaNO3 and NaF) to form sodium hexafluorotitanate, allowing for the partial precipitation of titanium compounds and recycling of acidic reagents, reducing the need for frequent bath replacement and minimizing environmental impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the chemical machining bath is used continuously, then productivity is maintained, but titanium concentration builds up reducing bath effectiveness and causing intergranular corrosion
Solution Approach 1:
The patent applies the discarding and recovering principle by removing dissolved titanium from the spent bath through precipitation with sodium salts, then recovering and recycling the acidic reagents (HF and HNO3) back into the machining bath. This allows continuous production while maintaining bath effectiveness by regularly regenerating it without complete replacement.
2Reliability
If the bath is replaced frequently to maintain effectiveness, then reliability is improved, but loss of expensive acidic reagents HF and HNO3 increases
Solution Approach 1:
Instead of discarding the entire spent bath, the process selectively removes titanium through precipitation while recovering and recycling the valuable acidic reagents HF and HNO3. This minimizes loss of expensive substances while maintaining bath effectiveness through regeneration rather than complete replacement.
Solution Approach 2:
The patent changes the chemical parameters of the spent bath by adding sodium salts to precipitate titanium, then adjusting the composition by supplementing with fresh acids to restore optimal concentrations. This parameter adjustment allows reuse of the bath with recovered reagents while maintaining effectiveness.
3Loss of substance
If potassium salts are used for regeneration, then titanium removal is achieved, but potassium ions contaminate the bath affecting part quality
Solution Approach 1:
The patent uses sodium salts instead of potassium salts as a disposable reagent for titanium removal. Sodium ions do not contaminate the bath in the same harmful way potassium ions do, and the sodium-containing precipitate can be easily discarded. This substitution eliminates the contamination problem while achieving effective titanium removal.
4Loss of substance
If the bath is drained and replaced, then titanium concentration is reduced, but production shutdown time increases
Solution Approach 1:
The regeneration process allows titanium removal and bath restoration without complete draining or replacement. By precipitating titanium in-situ and recycling reagents, the process minimizes production shutdown time while effectively reducing titanium concentration through selective removal rather than total bath replacement.
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
The process effectively recycles acidic reagents, maintains bath effectiveness, and ensures compliance with aeronautical quality standards by avoiding the introduction of undesirable potassium ions, allowing for continuous production with reduced waste and environmental impact.
Implementation Method 1
A regeneration process using sodium salts (NaNO3 and NaF) to form sodium hexafluorotitanate, allowing for the partial precipitation of titanium compounds
Implementation Method 2
3 Ti + 4 HNO3 + 12 HF → 3 TiF4 + 4 NO2 + 8 H2O (1) Ti + 4 HNO3 + 6 HF → H2TiF6 + 4 NO2 + 4 H2O (2)
Data Source
Figure 1~2
AI summary
The invention relates to a process for regenerating a nitrohydrofluoric bath for chemical etching of parts made of titanium or titanium alloy that is found in an etching tank (100), comprising, when said etching bath is spent, performing the steps consisting in: a) - transferring a portion of the spent etching bath, referred to as spent solution, from the etching tank (100) to a reactor (1 ), b) - adding to the spent solution an amount of NaF and of NaNC3, in order to form HF, HNO3, and Na2TiF6, c) - separating the precipitate formed from the supernatant, d) - transferring the supernatant which is a regenerated solution, to a reservoir (2), e) - measuring the dissolved HF, HNO3 and titanium concentrations in the reservoir (2) and in the etching tank (100), f) - determining the volume of regenerated solution that can be added to the spent etching bath in order to obtain a regenerated bath, the dissolved HF, HNO3and titanium concentrations of which are each respectively within a predefined range of acceptable concentrations, and transferring said volume of regenerated solution to the etching tank (100).