Acid-resistant linings with additional abrasion resistance characteristics

1. Task assignment 

Chemical waste water is collected in a buffer tank.

By means of direct steam heating, the waste water is brought to a temperature of up to 85 °C. In the container the pH value is set to a value of approx. 2 (sulphuric acid). A continuous mixing of the container is ensured by use of an agitator.

In order to assure a specific buffering capacity the container volume is set at 80 m ³. Due to technical assembly reasons the container’s height including the upper edge is limited to 4 meters. Thereby resulting in a container extension of approx. 6 m.

On-site circumstances showed that a concreted container represents the most economical solution.

In order to have a container form with as few non perfused areas as possible, a 10 cornered prefab polygon was chosen.

Due to the chemical aggressiveness of the waste water, the concrete needs to be protected. In addition the non-dissolved waste water ingredients, which cause corrosion to the concrete, need to be considered.

2. Technical description of the system and its alternatives

Other alternative possibilities which can be chosen during the technical check:

a) steel tank with interior rubber coating

b) concrete container with

1) lining with PP-plates

2) lining with glass-fibre reinforced plastic and chemically resistant in-liner

Ad a)

Steel tanks in dimensions, which exceed a diameter of 4 m, have an increased prefabrication expenditure. Therefore two containers with smaller dimensions would be needed, whereby the expenditure of the agitating technology doubles. Corrosion protection is not provided.

Ad b) 1)

Linings with PP-plates have a constant temperature load of up to max. 80 °C.

Ad b) 2)

The temperature-constant GRP with in-liner does not possess abrasion protection, and offers moreover only limited chemical protection.

Technically implemented constructions

Lining with rubber coating and acid-resistant brick lining.

The layered structure of this acid protection starts at the concrete wall and contains:

• conductive filler

• rubber coating Stellabutyl 2 mm

• lining with acid-resistant bricks 100 mm and furan resin based cement.

Thus, the lining takes over two functions: on the one hand abrasion protection and on the other hand an additional temperature protection particularly close to the steam injection spots.

Special attention is to be placed on the cementing of the masonry, where an increased expenditure in the cutting of the stones is to be considered. A special detail is the implementation of the walls (see the following representation).

In particular the electrical grounding of the container also needs to be considered.

3. Cost effectiveness

Based on the local conditions, we were not only able to find the best technical solution but also, the most economically favourable implementation conversion solution.

4. Summary

During intensive market analysis about acid protection it turned out that several vendors do offer different solutions for industrial purposes, which offer a range of advantages to reach a decision.

However it is necessary to have a detailed description of tasks involved, to find the technical and best economical solution for a certain application.