Use in paper industry
In the paper industry limy deposits from the circulation water are being eliminated by utilization of lime traps. This greatly reduces the consumption of freshwater and results in a sustainable improvement of process reliability. The costs for the repair and maintenance of the systems are also significantly reduced.
Strict rules apply to the disposal of wastewater. Therefore, reprocessing wastewater is not only good for the environment but also makes economical sense. The pump manufacturer EDUR has developed a highly efficient method to improve wastewater treatment.
The pumps operate as a dynamic mixer and do saturate atmospheric air into the recycle water. The lime in the water is getting separated out of the water by adhering the single particles to the generated micro bubbles and smoothly rising it to the water surface. Here the slurry is skimmed away by a separate process step. Various flotation methods are known that mainly differ with regard to the type of bubble generation. In the water treatment technology the so-called dissolved air flotation became proven as an efficient process.
In a paper factory a recycle flow of approx. 288 m³/h used to be saturated with compressed air in a pressure reactor. The compressed air volume inserted was adjusted to approx. 400-500 l/min. To areate the flotation a standard type pump with 75,0 kW motor power (QN 288m³/h, HN 6.5 bar, power input at QN approx.68,0 kW) and a 7,5 kW compressor, a pressure reactor for preparing the air/water mixture and a compressed air tank conventionally were to be installed. This conventional system requires a high amount of energy and furthermore is of high-maintenance, as in addition to the standard pump numerous components like compressor and pressure tank are necessary.
Two EDUR multiphase pumps type LBU 603 E162L / 18,5 kW were installed with air inlet at the pump suction side under the same operating conditions . The results showed a trouble-free operation of the flotation system at an operating point of QN 45 m³/h HN 4 bar incl. approx. 20% air and a power consumption of approx. 13.0 kW per pump at QN. In the conventional system a total of 75,5 kW (motor and compressor) is required. In the EDUR system on the other hand no extra compressor is required and the power consumption of the two pumps is only 26,0 kW. The total drive power thus reduces by 49,5 kW or impressive 65,6%. The annual energy cost savings with an electricity price of € 0,10 / kWh and annual operating hours of 8.000 hours (3 shift operation) amount to approx. € 39.600,00. The energy-efficient modification of the plant thus amortised after approx. 5 months.