Cartiere Burgo S.p.A., Verzuolo Mill will use Pressure Grounwood (PGW) as a raw material for LWC paper

Published Mar 08, 2000 00.00.00 +2 GMT

The Italian paper producer and Valmet Corporation signed in November, 1999 a contract for a EPC delivery of a complete pulp and papermaking line with a value exceeding EUR 250 million. The OptiConcept paper machine will produce light-weight coated (LWC) paper. The furnish for the machine will be purchased bleached kraft pulp (BKP) and Pressure Groundwood (PGW) pulp.

Cartiere Burgo made a very thorough study about the feasibility of the proposed expansion project at Verzuolo. This included pulping trials with a mixture of European spruce wood in the same ratio the mill is using the wood today. Pulping trials confirmed that PGW 70 process provides the most optimum pulp property profile for the Verzuolo project. The low electrical energy demand as well as low enviromental load of PGW were significant factors.

500 TPD PGW Plant The plant consists of 6 Valmet T 1815P grinders which are designed for 1.5 m log length. The grinders have automated log feeding system.

The ground PGW pulp is fed to shredders where slivers are disintegrated. Valmet TAS 340 pressure screen is used for grinder shower water screening. Valmet Water Jet equipment will be delivered for stone conditioning.

The main line screening to be delivered consists of two parallel Valmet multistage screens (MuST503E) with three internal screening stages after a PreScreen with ø 3,0 mm hole. The screens are equipped with a narrow slot wedge wire baskets.

Screen rejects will be handled in a cleaner system for sand removal and will be prethickened with a side hill screen. For high consistency refining, the rejects are thickened with screw presses and refined with two Valmet RGP 262 pressurized refiners.

The reject screening will be handled with a multistage screen MuST503E in a similar way as in the main line. Accepted pulps from main and reject screenings are combined and thickened with a disc filter.

After disc filters pulp is pumped with an MC pump to Valmet twin wire presses TWP 31 for HC peroxide bleaching. For chemical mixing, mixers will be delivered. Depending on brightness target peroxide bleaching, hydrosulfite bleaching or both can be used. Thus a final brightness of 80 % ISO for the pulp can be achieved with moderate chemical consumption. After bleaching pulp is diluted and washed with paper machine white water on twin-wire presses and then pumped to the storage tower.

High quality LWC paper requires low freeness mechanical pulp. The final pulp freeness level will be CSF 35 - 40 ml. For Burgo the excellent paper surface and optical properties are most important. Trials with mill wood showed that PGW 70 process gives the best optical properties and at the same time strength is superior when compared to the pulp from the existing groundwood plant.

For further information, please contact:

Valmet Mechanical Pulping Lines Hannu Salakari Sales Manager, News & Magazine Tampere, Finland Tel. + 358 2048 2170 Fax. + 358 2048 2 2850