BVG Bauer-Verfahrenstechnik GmbH, Greifenberg, Germany, was selected the supplier for the PM 4 coating kitchen and wet end chemistry.

The order was given to BVG, because BVG offered the most innovative system for coating color preparation, the "Super-C-Shear”. No operational experience existed before on this technology – it was considered a prototype. The potential and perspective was most promising. Therefore, the Perlen Papier AG project team decided to go for this system. It is not common, on such a big project, to enter into new technology and take chances on a key portion of the plant. Sure the risk was worthwhile. Expectations with the new coating kitchen were not only fulfilled, they were already exceeded during start-up! High-quality coating color was produced from the beginning - with no wasted product. The first container of coating color produced, went out to Omya in Oftringen/ Switzerland, where it was immediately analyzed and qualified as a high-quality product.

This success had been prepared for well in advance and did not come from approximations. BVG put in more than 20 years of experience in equipment construction and had a free hand in the conception and technical conversion of the plant. The accurate, reproducible dosage of the individual components of the coating color was particularly important. BVG had already successfully implemented on-line additive dosages in small quantities on special paper production. Omya also aggreed, making test runs with a trial plant at their facilities in Oftringen - this plant was built dpecially for this project by BVG – to ensure the technological aspects of the design. Important observations were made here and improvements were applied to Perlen. Special thanks goes out to all those involved in the testing phases at Omya.

BVG supplied the Perlen PM 4 project with all the engineering, construction of the entire plant mechanically, the assembly, start-up, and optimization. Since it was to be a fully automated system – no local service personnel is needed, only the PM 4 coater personnel in the control room to monitor and care for the plant - highest priority was put on the programming of the DCS. Therefore, BVG decided to train its own personnel on the supplied Alstom DCS system, and do all the programming as well. Thus, an important condition for the operability and user-friendliness of the entire complex was met. The entire plant, including the BVG recipe manager, comprised only of the Alstom system. The benefits here are user-friendliness, reduced maintenance, easier servicing, and more.

The plant in detail:


Tank-Farm

Here the main products for the coating color and wet-end chemicals are unloaded and stored.The preferred delivery method is by railcar. Unloading by truck is also possible. The tank-farm consists of a separate building with favorable logistics. Accommodated within are:

Unloading station with pumps, air-filters, storage tanks, pumps, and ring-mains for:

- 2 Carbonate slurries
- 2 Clay slurries
- 2 Filler slurries
- 2 Binders
- 1 Alum Sulfate in liquid form
- 2 Components in big bags

- Silo for Powdered products, Disperser, Storage,
Re-circulating line for:
- Talc

 

Storage of Pigment Slurries

Container stations for chemical additives
to be used in the wet end

Components for chemical additives and wet end would be delivered in 1000kg containers to stock the central feeder system with:

- Three nuance dyes
- Defoamer
- Optical brightener
- Anti-Scaling Agent
- Acid for felt washing
- Caustic for felt washing


Wet End Starch

For the wet end starch, a completely new plant was installed to supply both PM 5 and the new PM 4. The new plant utilizes a 100m³ starch silo, which corresponds to approx. 65 metric tons of starch. The entire starch make down is located below and within the silo frame itself. This arrangement is both economically and technologically favorable.
The make down of starch powder is done in a special slurry station with regulation of the slurry concentration to a constant ± 0.15%d.s. Slurry is cooked in the BVG-Super-Jet and fed into a 4m³ storage tank. After this tank there will be dosing system with inline post dilution and supplied to the addition points at PM 4 and PM 5.


Container Pool for chemicals, which are inserted
for use in the coating kitchen.

Minor components for the coating color are delivered in 1000 kg containers and metered in special feeder systems as:

- Two Different Dye Agents
- Optical Brightener
- Sodium Hydroxide
- Hardener
- Anti-Foaming Agent
- Stearate
- Thickener

The metering is done continuously with pumps by use of mass flow meters and control valves.


Preparation of CMC

CMC is delivered in powder form in big-bags. Make down is done automatically, in a batch process, to a final colloidial solution of 10% d.s. The advantage of this system is in the fact that an optimal and gel-free solved product is available, which will not lead to any problems in the coating dye. The small quantities of CMC which are usually used, have only a marginal influence on the final dry solid content of the coating dye. This argument does not justify the use of powder commodity in the disperser, like you hear so often. There are enough other possibilities in order to raise the dry solid content in the coating dye.


Preparation of Coating Starch

Coating starch is delivered in powder form in super-sacks and cooked in a BVG–Super–Jet, a continuous jet cooker, to a final colloidal solution of 40% d.s. This system is fully automatic. The cooker keeps the slurry concentration within the range of ± 0.15% d.s.

 

Starch Preparation from Big-Bags

Continuous Coating Kitchen

The continuous coating kitchen was placed in an existing building, which was used before to prepare stock. The building was reorganized and adapted for use. The heart of the new coating kitchen are the two continuous BVG-Super-C-Shear dispersers, with the associated metering stations for the individual components. There are two units available in order to be able to manufacture different coating colors simultaneously for both sides of the paper. In addition, it is possible, with a disperser, to manufacture two or more different coating colors successively. The high flexibility and efficiency of the system makes this possible.
In the plant, main components from the tank-farm, and the small components are mixed reproducibly in such a way that an ideal mixture is developed and dispersed.

This target will be reached successively by accomplishing this three step process:

Each of the two lines produces appr. 15m³/h (3960gal/h) of coating color. That corresponds to an achievement of appr. 350 metric t/d (386 t/d) of oven-dried coating color per line. The PM4 plant can process a max. of 300 t/d of oven-dried coating color. Thus, a reserve of appr. 100% is available. Each line has an installed electrical power of 20kw, without peripheral devices. A similar batch system would require around 400kw. An immense power reduction!

The highlights of the plant, compared to a batch system:

- Minimal energy requirements
- Minimal space required
- Minimal process volume
- Problem free handling of highest dry solids (up to 68% d.s.)
- No up heating of the coating color
- Highest uniformity of coating color
- Highest quality of coating color
- High flexibility

Continuously Disperging BVG-Super-C-Shear

Service station for the supply of coating colors

The service station is installed below Speed Flow. Distance to the coating kitchen is appr. 200m (660ft.). It is possible to apply different coating colors to both sides of the paper.
Each station consists of a supply tank, two feeder pumps, a BVG-Super–Strainer with 150-micron slotted basket, and a BVG-Super–Ex–Air mechanical de-aeration unit.


Process Control

The entire plant is equipped with sensor technology in connection with the process instrumentation, permitting the operator to monitor the actual status of the plant and to monitor any real-time trending. In this way, any fault can be recognized and corrected in time.


Summary

The performance of the plant, particularly the technological aspects, positively impressed all those involved. It just goes to show, technical progress is only possible if a calculable risk is taken. Perlen Paper took the risk and won.

We thank Perlen Paper for their courage.