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Process Control – AKZO NOBEL BASE CHEMICALS GmbH

10. April 2009

Chlor-alkali electrolysis has a long tradition at the AkzoNobel Industrial Chemicals Bitterfeld site. Up to 2000, chlorine gas and caustic soda were obtained using a diaphragm and amalgam process. High energy costs and, in particular, heavy environmental pollution led to the modern membrane process being used exclusively now.

Integrated into the Bitterfeld-Wolfen chemical park products and material flow, AkzoNobel Industrial Chemicals, with approximately 70 employees, has an extensive pipeline network of chlorine, hydrogen chloride and caustic soda available for the production operations based here.

 

Plant in Bitterfeld

Control cabinet with 4 FP16 units

The modern, environmentally-friendly membrane plant at AkzoNobel Industrial Chemicals is operated with four electrolysers each with 150 separate components. One component consists of an anode and cathode half-shell with the membrane between them. The service life of the membranes depends on the contamination in the brine. If the brine quality is good, the membrane will continue to work for four years and more.

FELLER ENGINEERING’s development and operating expertise in chlor-alkali electrolysis using the amalgam process gained over more than 30 years was the ideal prerequisite for collaboration with AkzoNobel Industrial Chemicals.

Based on the former monitoring system, a monitoring unit, the FESCA 7.1, was developed which was adapted to the requirements of the new membrane electrolyser technology. By recording and saving various pieces of data (such as voltages, temperatures etc.), the user obtains information on the remaining service life of the individual components or on the ideal parameters for as high a current yield as possible amongst other things.

FESCA 7.1 is designed to measure 150 component voltages. Four specially populated FP16 units record the measurement data and communicate with a PC in the measuring station via the Ethernet. The FESCA 7.1 evaluation software, tailored to the requirements of AkzoNobel Industrial Chemicals, is installed on this PC and is used for process monitoring.

The electrolyser’s component voltages are scanned and saved periodically. The recording rate is 1 second for the last 10 days. Measurement values that are older than 10 days are stored as an average value every hour.

The anolyte and catholyte temperatures and the electrolyser current are recorded and stored in addition to the component voltages. These values are imported periodically by the higher level process management system using an automatic data import process. All essential process values, such as total voltage, mean value, electrolysis current, temperatures and any alarms are shown in an overview for all electrolysers.

Bar diagram

History / Trend

Event protocol

You will obtain a detailed view for each electrolyser by clicking on the overview. All component voltages for the relevant system are shown in the form of a bar diagram.

The calculated mean value of all components appears as a line above the bar. Major deviations from the mean value are indicated in a different colour (see component no. 35 – yellow). The maximum permissible deviation can be configured. If the maximum limit is exceeded, the bar display turns red.

With other functions, such as the trend display or current and historic values, the event log of the last 30 calendar days up to configuring the user level, AkzoNobel Industrial Chemicals now has a convenient system for a configurable analysis of membrane electrolysis systems. The modularity of the hardware components and the flexibility of the structures within the recording software ensure that the system can be adapted easily to different system configurations. Empirical values can be integrated into the software continuously in order thus to support the user in process-related decisions.

The high level of performance readiness for all future requirements will also continue to be the basis for collaboration between AkzoNobel Industrial Chemicals and FELLER ENGINEERING.