The validation of two novel separation technologies in a ZLE concept via in-mill research at recovered paper mill Niederauer Mühle (Germany)
As economic circumstances change and environmental legislation tightens, paper mills are forced to minimise their energy and water consumption to produce minimum emissions. A competitive product based water treatment concept to Zero Liquid Effluent (ZLE) is based on the 'five-fraction model'. To remove suspended solids two novel separation technologies are tested with pilot trials at paper mill Niederauer Mühle. The first pre-treatment technology is a Settle Plate Clarifier (SPC). The SPC was installed for seven months at the paper mill and it was running more stable than a DAF-unit under dynamic papermaking conditions. The SPC has an average TSS-removal efficiency of 96.5% and a particle-removal efficiency of 94% for particles between 0.8 and 100 μm. The best application for SPC would be a pre-treatment followed by a second step dissolved air flotation. This way the clarified process water could be re-used on nozzels of the wire section without risk. As a second pre-treatment technology a Rotating Filter Technology (Rofitec) is tested. The experiments were done with two different pilot units, fist with a non-selfclening Rofitec, which is running as batch process, and second with a continuous selfcleaning Rofitec. The selfcleaning Rofitec can reach a TSS-removal efficiency up to 99.5% and a particle removal efficiency of 93%. The Rofitec is an ideal technology for after treatment of DAF sludge or reject from SPC up to an inlet consistency of 3% to reduce the waste volume (Reject consistency: 30-33%, Thickening factor: 97-99%).
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Laws and legislation
Paper and pulp mills
Wochenblatt für Papierfabrikation, 129 (5), 289-295