High consistency foam in pilot scale

Resource-efficient processing is one of the pathways tomanufacturingsustainablefoam-formed products. Replacing the current foaming methods with High-Consistency Foam(HCF) can reduce resource consumption in terms of water, and equipment footprint. Therefore, we carried out pilot-scale HCF trials to address requirements on the process equipment and parameters to generate low-density porous structures. The pilot scale HCF unit comprisedof unit operations in the following order: (a) 200 L mixing tankwith pitched blade turbines, (b) centrifugal pump with an air-removal system, (c) Headbox with 5 mm and 8 mm rectangular openings and (d) pilot machine with 300 mmand 700 mmweb, impingementand through-airdriers.A mixture of softwood(SW)and hardwood(HW),from 8% to 14%consistencies,were used. 4 to 6 g/L of non-ionic Simulsol 10 was used as a surfactant. We found that a dual impeller system can generate homogeneous HCF with14%consistency (50% SW + 50% HW) resulting in the lowest wet foam density of 160 g/L. Besides,higher mixing power wasrequiredfor pure SW foam compared toHW foam. The headbox with an 8 mm opening and 640 mm width worked better,whereasthe 5 mm opening encountered frequent blockageprobably due to the too-low flow rates. A minimum flow rate of 0.2 L/sec was required to avoid backpressureand to distribute the foam inside the headbox evenly. Highly porous low-densitysamplesin the density of 20-80 kg/m3were examined using x-ray tomography to detect the structures’flow channels/weak points. HW waseasier to foam without flocks, but the structure was brittle whereas themixture of HW andSW enhanced the structure. In summary, an improved understanding ofthe operating parameters of different unit operations (mixer, pump, head box,and pilot machine) to form low-density webs with HCF was achieved.