MACO Pilot – Optimisation of the mixed-acid online monitoring and control in stainless steel pickling plants

Initial situation

Economic pressure on European steel sector demands high flexible and favourable production
Especially the pickling step is of high importance for stainless steel production
High process flexibility needs a fast adjustment of defined concentrations in industrial mixed-acid pickling baths for achieving consistently high product qualities and plant productivity.
Within the RFCS project FLEXPROMUS an innovative method for continuous HF-HNO₃-mixed-acid online analysis was successfully developed
First prototype tests at stainless steel strip pickling lines showed very promising results

Project objectives

Optimisation of online-measuring-technique for continuous concentration monitoring in HNO₃-HF-mixed acids
Optimisation of concentration monitoring and control at stainless steel pickling facilities
Online-measuring technique prototype test installations at stainless steel strip and wire rod pickling plants and acid regeneration plant
Model based optimisation of the pickling process operation at stainless-steel wire rod dip-tank pickling plants

Innovative process approaches

Continuous online-concentration monitoring of mixed acid pickling solutions by means of model based measuring technique
Development of a „closed loop“-concentration control model for stainless steel strip pickling lines on basis of online-concentration data
Development of a pickling programme management model for wire-rod pickling plants
Concept development for improvement of existing European mixed acid pickling plants by online monitoring and control

Final results to the end of the project (12/2019)

Optimised online-measuring system prototype set-up (increase from TRL5 to TRL7)
Successful installation and operation of online measuring systems at a strip pickling line including regenerated acid tank and wire rod dip tank pickling plant in combination with filtration
Optimised concentration calculation model for different mixed acid applications, deviations between online analysis and BFI laboratory reference analysis mainly < ± 5 g/L for free HF + total metals and < ± 8 g/L for free HNO3 concentration under optimal measuring conditions
Advanced closed-loop and open-loop concentration control models based on high-rate concentration data enable enhanced pickling process stabilization, saving of acids and reduction of emissions as well as saving of costs
Reduction of manual mixed acid sample drawing can improve the working conditions and safety
An innovative pickling program management model enables more optimised and safe wire rod pickling plant operation

Outlook

Further concentrations calculation model optimisation (soft- and hardware modifications)
Finalisation of measuring system set-up from prototype to commercial version

Presentations from the international workshop November 11, 2019