PV-2 Preexpander

is designed for the preexpansion of expandable polystyrene beads by means of thermal processing. Saturated steam is used there as heat-transfer agent.

All preexpanders can be divided into 2 types:

• continuous type
• batch type

The preexpander we manufacture is a BATCH TYPE preexpander.

Continuous type preexpander disadvantages:

1) It is only possible to control 2 factors while expanding:

• steam passage through raw material (its quantity);
• raw material residence time in the preexpander.

2) Steam pressure can only be decreased (by means of mixing it together with the air), but not increased, as the process is accompanied by air pressure (continuous type preexpanders are open and totally uninsulated vessels).
The above mentioned disadvantage apart from a possible violation of the expansion procedure triggers another and not less important one, namely inefficient steam consumption and, as the consequence, more expenses on steam generation.

3) The raw material average residence time in the continuous type preexpander is abour 3 minutes, the minimum density of expanded granules directly connected with the contents of pentane in raw material.

Batch type preexpander advantages:

1) Steam pressure can be regulated, that is why it is possible to adjust steam temperature to the required density or the level of pentane contents in raw material.

!!! Steam temperature that does not conform to the requirements may lead to the deformation of the cells.

The lower the level of pentane in raw material, the later the expansion begins and the higher the required temperature is.
2) Batch type preexpander is an insulated vessel, that is why steam is consumed in a more efficient way and the expansion speed can be increased dramatically compared to a continuous type preexpander.

Specification (for the production of EPS density 25)

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