Major savings can be made in the Lead Acid Battery industry by purchasing and transporting Sulphuric Acid in its most concentrated form and diluting it on-site at the battery manufacturing stage. Sulphuric Acid, however, has a great affinity for water and so the dilution process has a high exothermic heat of dilution - releasing large quantities of heat energy. Because of this, boiling of the resultant mixture can occur quite easily if the process is not carefully controlled.
It should be noted that, regardless of the proportions of the feedstocks and the final concentration, the mixture will always pass through the maximum exotherm (in excess of 145°C) at some point in the process.
In the mixing and cooling areas, plant conventionally used to produce Dilute Sulphuric Acid from concentrated feedstock traditionally uses resin filled graphite, PTFE or glass for contact surfaces; these direct mixing designs suffer from severe thermal shock and thermal cycling associated with the relatively fragile and expensive materials. The results of these stresses can lead to high maintenance costs and significant plant downtime.
Who uses the system?
Sulphuric acid dilution systems can be used in a number of industries. The Chem Resist system has in particular been successful in the battery manufacturing industry with Exide (UK), Akuma (Czech Republic), Sunlight (Greece) and Hawker (Poland).
Overview of the System
The system consists of four sections:
- Acid Feed
- Deionised Water Feed
- Static Mixing and Cooling
- Cooled Acid Pumping
The product composition is monitored by a densitometer and controlled using an electronic control system which regulates the water feed control valve. For safe operation of the plant, mixing temperatures are monitored by temperature sensors linked to an electronic controller. This, in alarm conditions, initiates a close-down procedure which renders the plant safe.