Production Of Man-Made Fibres: Specially Adapted Water Treatment Plants For Complete Demineralisation

From spinning to cable production and fibre cutting: all these work stages require fully demineralised water (demineralised water) – almost pure water that is largely free of electrolytes and has low conductivity. About 70 per cent of the water is used for the production of polyester products. In order to induce desired chemical reactions or not to disturb them, the water must be as salt-free as possible. Individually adapted water treatment systems can ensure significantly lower maintenance requirements and higher economic efficiency.

With fully demineralised water, fibre manufacturers avoid, among other things, deposits in the steam boiler, which could often lead to corrosion damage and, in the worst case, even to the bursting of a boiler. All other containers, pipes and fittings with which the water comes into contact on its way through the production stages are also protected by demineralised water, provided they are made of suitable materials.

Reliability And Reduced Logistics

Customised water treatment systems should deliver the desired pure water of the highest quality, without the use of hazardous substances – and they should also simplify maintenance and be available around the clock. In fact, a breakdown might cost several hundred thousand euros a day. Therefore, the reliability of such a plant is an extremely important criterion.

In the past, the preparatory work alone for the beginning of the desalination process was much more time-consuming. For example, about 300 kg of regeneration salt had to be manually filled into salt containers from 25 kg bags every day. This high logistical effort is avoided by the new solution, in which large brine bunkers are created (in the size required by the company), in which brine is continuously formed and used to feed the brine measuring vessels of the softening plants. In this constellation, the necessary salt is delivered in silo trucks only every 1.5 months.

Second Purity Stage with Reverse Osmosis

In reverse osmosis plants, semi-permeable membranes are used that are only permeable to water but not to salt. In this stage, full desalination and the desired ‘pure water’ are finally achieved. All parts of the system with which it comes into contact have a longer life and need to be maintained or cleaned only very rarely. And this also applies to the central element of steam generation, the steam boiler. Any residual amounts of salts that may be still present have to be removed several times a day by drain depressurisers.

The boiler water, which is over 200° C, is cooled down to 40° C so that it can be discharged into the wastewater system. This is done using existing soft water that comes directly from the softening plant and is stored in the drain depressuriser.

Photo: chinnawat