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CAM reduces curing energy by 40%

Can customers improve suppliers’ technology?— a collaboration between Exide and CAM shows that it can happen.

Time flies… even in the lead-acid battery industry. It’s nearly a decade since BEST magazine paid a visit to the Marfisi family (better known as CAM) covered in the article “Active Material is in the Family” back in the Autumn 2003 issue of BEST. 

The Marfisi brothers— Fernando, Bruno and Armando, the eldest and founder of the company, have been in the industry for over 45 years.

But how did the company actually start up? In 1967, Magneti Marelli invited Armando to establish a mechanical construction and engineering company in his home town, to support new factories that were being built in southern Italy. The years of experience in the field of battery equipment innovation and in the automobile industry formed a solid basis for the fledgling company, and in time it carved a niche in the market. 

This past winter, one of CAM’s biggest customers, Exide Technologies, who acquired Magneti Marelli in the early 1990’s, asked for help to conduct tests aimed at bringing our CAM curing chambers within the guidelines of Exide’s Energy Excellence Program (EEP) (see www.cam-srl.com). As the standard complete cycle time in the 16MC34 curing chambers is 22.5 hours, and in the 30N3-S chambers it is 32 hours for 35 tonnes of pasted plates (0.1-0.2% residual moisture; 1.2-1.4% free lead; grid-to-mass adhesion 100% in both models), the company believed that little could be done to improve performance, but accepted the challenge. 

Exide Technologies Europe’s EEP— Energy Excellence Programme— was launched in April 2011,in collaboration with Alexander Proudfoot. 

The primary objective was to improve efficiency in terms of energy consumption in each of the 12 plants involved in Europe: Azuqueca, Manzanares, La Cartuja and San 

Esteban in Spain, Castanheira and Azambuja in Portugal, Romano in Italy, Poznan in Poland, Lille and Peronne in France, and Buedingen and Bad Lauterberg in Germany.

At the very heart of the Energy Excellence Programme is the need for metering and sub‑metering. The measurement of the plant energy consumption is crucial in order to analyse the data produced, and subsequently take actions and create initiatives aimed at improving the plants’ energy performance. It is also necessary in order to subsequently re-measure the energy utilisation following the completion of said initiatives, to ensure that the required impact has been achieved.

Direct- Indirect Energy

Direct Energy is defined as the electricity used to charge the batteries in the formation area. Overall it accounts for around 40% of the total electricity costs. Indirect Energy is defined as all other electricity plus Gas and accounts for 60% of the total electricity consumption. 

For the Indirect Energy areas within the plant that are a priority, the following were also considered: Compressors, Mills, Rolling Mills, Assembly Lines, Curing Chambers, Filters, Plastics Injection (if applicable) and Ancillary areas (Laboratory, general offices…)

Curing Process and Curing Chambers

In European Exide plants there are different types of curing chambers from several suppliers. The curing profiles can be different for various configurations of flat plates in stacks or as hanging panels or for tubular plates. Chamber sizes, energy sources and other parameters to control the process may vary as well. 

The novel approach of the EEP-Project was to investigate the possibility of reducing energy consumption during the curing process for each plant and chamber. The typical energy sources, depending on chamber type are electrical power, gas, steam or hot water. 

Curing Chamber Investigations

A standard curing run can be investigated by the following procedures: 

Measuring humidity and temperature in the chamber and between plates

Metering all types of energy consumptions with respect to the real chamber loading with paste.

Analyzing cured plates with regards to 

Tri/tetrabasic lead sulphate content

Free lead content and moisture of cured plates

Degree of mass active material adhesion to grid

Uniform colour

Density and porosity

Specific single-plate capacity of dry charged plates

On the basis of these results a modification of process parameters is possible in most cases in order to:

Ensure the quality level of cured plates and 

To reduce the energy consumption during the curing process. 

Guidelines to optimise the curing process

Use the exothermic reaction of curing process as energy source.

Ensure a sufficient level of oxygen in the chamber for the curing reaction.

Avoid a mix of tri- and tetrabasic lead sulphate. 

Ensure full loading of curing chambers with pasted plates.

Ensure uniform plate quality for all rack positions in the chamber.

Double-check programme parameters and tolerances so as to avoid over-adjustment.

Keep the drying step as short as possible.

Use heat exchangers to re-utilise the energy of warm exhaust-fumes and VSDs for ventilation. 

Minimise the ventilation speed during curing.

Where applicable, replace electrical heaters with gas burners on the basis of energy prices. 

Avoid energy loss by ensuring doors are sealed and pipes are insulated. 

Results and Discussion

In collaboration with CAM it was possible to select and optimise the main parameters of the standard curing profile of their 16MC34 chamber within a few test runs. As shown in the figures, during the curing step the plate temperature is higher than room temperature. This indicates that the curing process as exothermic reaction has already begun. At the end of the curing step the temperatures between the plates and in the chamber are equal, showing that the reaction of lead oxidation is nearly complete. The drying step is characterised by an increase in plate temperature and a decrease in humidity between the plates.

Figure 3 shows the general scheme of the basic curing profile in the 16MC34 with 1.5hrs for loading, 15hrs of curing, followed by 6hrs of drying. Figure 4, on the other hand, shows the results of the cycle with modified parameters, where energy consumption was reduced by more than 40% with no deviation in quality with respect to the standard curing process, thus the objectives of the tests were successfully achieved. 

CAM would like to thank Exide Technologies and in particular, Mr. Karl-Heinz Haas and Dr. Harald Niepraschk, the managers and technical staff at Exide Romano di Lombardia, as well as the director and technical staff at Exide Poznan for their kind and fruitful collaboration.

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