QDOS PERISTALTIC PUMPS | DOSING ACCURACY IN THE PAPER INDUSTRY
Dewatering was far more effective, resulting in an increase of 2.5% in dry solid content on ideal circumstances, which are rarely the case in practice. In truth, process conditions vary, and end-users simply like to install a dosing pump at plug and play level into their process. Qdos pumps deliver accurate flow, despite changing process conditions, and do not require additional ancillaries like inlet and pressure-holding valves. This lowers the cost of maintenance and process downtime due to clogged valves. Huhtamaki recognised the issues with diaphragm pumps some years previously, and decided to participate in the development of Qdos peristaltic metering pumps for a number of paper pulp duties. Since the adoption of this new technology, various process enhancements have been made, achieving increased efficiency, improved product quality, safer maintenance and significant savings on chemical usage. Driven by Huhtamaki’s ongoing ambition to be the best moulded fibre packaging company worldwide, it decided to establish a project to bring down its greenhouse gas emissions to a minimum, and maximise the reuse of its process water. The project set out to optimise the calcium load in their system and impact on the company’s CO 2 emissions. By dosing lime with high accuracy, Huhtamaki succeeded in achieving optimal control over the pH. The trial proved that the dewatering stage was far more effective than it had been, resulting in an increase of 2.5% dry solid content at the entrance of the drying section. Moreover, less water had to be heated up to 100C and evaporated.
Above: Qdos pumps used for colourant dosing
tend to get blocked by lime dispersion. Even after removing the foot valve and pressure-holding valve on the discharge side, diaphragm pumps do not deliver a constant flow. As the accuracy of the quantity of lime dosed has a significant impact on the process performance and end-product quality, it is critical to select the optimal dosing pump for the task. For the trials at Huhtamaki’s site, a Qdos 120 peristaltic chemical dosing pump from Watson-Marlow Fluid Technology Group was used to deliver the lime prior to dewatering the paper pulp.
translates into less slime in the system and lowers the odour of the end product.
More importantly, closed loop water systems, common in paper manufacturing, struggle with a high calcium load. Water evaporates at the drying section but the calcium remains in the system causing scale formation. By adding the lime at the wet end, the calcium will be enclosed in the paper floc (substrate). This will lower the calcium load as the calcium leaves the manufacturing process via the end-product. This also enhances dewatering, resulting in lower drying section temperatures and lower gas consumption. Lime is a challenge to work with, as it tends to settle, forming lumps in suspension. Diaphragm pumps are often used to add lime. However this can cause difficulties as ancillary foot valves
The technology The selection of a chemical dosing
pump often has a significant impact on the efficiency of a water treatment or manufacturing process. According to the specification sheets, most chemical dosing pumps deliver similar performance, although this test data is often based
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