During the early 1970’s the old experimental paper machine at STFI was left too far behind by technical developments to be of any great use for basic process research. In the mid 1970’s, therefore, the planning began of new equipment at STFI. The aim was to design the experimental system required for a basic process research programme during the period 1980 – 2000.
It has to include all process units involved in recirculating material flows. This means that stock preparation, wire section, press section and backwater system should be included, while drying can be performed off-line.
The wire section should include the two basic twin-wire forming principles as well as a Fourdrinier section. In the wire section it should further be possible to form multi-ply products, either from a multi-ply headbox or from several headboxes. The roll width in the wire section will be 800 mm, which means that headboxes up to 500 mm width can be applied. The press section should avoid open draws and include double felted as well as single-felted nips. To simulate industrial processes running according to modern environmental standards, a filter should be used to recover suspended material from the excess back-water, which could then be re-used for showers, dilution, etc.
The dynamic properties of the FEX System were calculated using computer simulations. As a result it was found that 2 tons of pulp will be needed to run the system into equilibrium. It was decided that the storage capacity in the stock preparation plant should allow the system to be run into equilibrium four times on one batch of pulp.
An experimental paper machine often has to produce more data than paper. The FEX System is therefore heavily instrumented, and the requirements of the different measurements often had a strong impact on the design of the system. A central minicomputer is to administer a number of microcomputers which will do the actual job of process control and data collection and processing, and also automatically start up and shut down the complete system.
Increased use of multi-ply forming and paper-making additives are two important development trends in the paper industry, and extensive research within these areas is planned.