Harvested from the sea and hard to move around

Sept. 1, 2014

Seaweed is tractor-harvested at low tide, dried and processed to yield high-quality crop fertilizer and soil amendments.

If ever the spirit moves you to commercialize and manufacture marine and seaweed-based products for use in agriculture and horticulture, consider the maritime region of the lower St. Lawrence River.

For one Quebec, Canada-based company the area’s benefits include easy access to fresh raw materials it needs — specifically, the seaweed Ascophyllum Nodosum. Not far away, seaweed is tractor-harvested at low tide, dried in greenhouses to retain its pungency and ultimately processed to yield high-quality crop fertilizer and soil amendments.

As part of its processing, seaweed, hot water and caustic solution are introduced into a 3,000-gallon tank and mixed until the seaweed lengths dissolve into more-or-less liquid form. Next stop is a centrifuge, where the solution is dewatered or, as they say, decanted. A NETZSCH progressing cavity pump is used to move solution from the tank to the centrifuge.

By the time the dewatering is done, the seaweed extract that remains is very viscous. Its thick, sticky and gelatinous consistency is, if you will, more than liquid and less than solid. The extract has a high pH value and is running at approximately 90 degrees Celsius (195 degrees F).

Conveyor no option

A conveyor was at one point tested as a way to move the dewatered seaweed extract from the centrifuge to plant packing areas. It was found unsuitable because of its "open" nature and inflexibility.

With a NETZSCH NEMO progressing cavity pump already used to feed the centrifuge, it was only natural for the plant’s managers to turn to NETZSCH, which delivered a custom solution.

During a subsequent pump trial, even with the discharge split to serve two packaging areas, the pressures incurred were handled nicely. Eliminating the need for separate batching equipment was a plus for overall plant productivity.

A solution that today works well was chosen based on the consultation between provider and user, especially as to end-product consistency, and the on-site trouble-shooting that took place as part of the demo pump trial.

The NEMO BF pump, a kind of progressing cavity pump with hopper and feeding screw, was selected. The pump is used in industry for continuous, pressure-stable, gentle and low-pulsation conveyance, with dosing in proportion to rotation speed. It is employed primarily for highly viscous, compacted and crumbly substances that do not have a tendency to bridge.

Some specs delineated

The pump conveying the highly viscous seaweed extract has an open-hopper design in stainless-steel construction with special feed screw and a stainless steel rotor suitable for 194 degrees Fahrenheit (60 degrees Centigrade). It’s the feed screw that makes the difference, allowing the pump to succeed where other pumps wouldn’t.

The feed screw over-feeds the pump chamber, creating a mixing and homogenizing effect in the force-feed chamber and introducing a backflow through the gap between the feed screw and the hopper housing. In addition, say its developers, the screw rises above the joints on both the drive side and the rotor side, thus avoiding dead areas in the joint region.

The customer also requested an EPDM food-grade stator and packed stuffing box. The pump has a right-angle 10 horsepower inverter-duty gear motor with severe-duty protection, a 10 horsepower variable frequency drive controller with coupling and guard mounted on 304 stainless-steel base-plate with a stainless steel 3 inch to 2 inch Tri-clamp discharge connection.

The open hopper pump was installed in late summer 2013. The customer cleanly and efficiently moves product throughout the plant to different packaging areas. The closed piping afforded by the pumping solution also eliminates production odors.

NETZSCH, founded in 1873, is a diversified manufacturer of specialized industrial equipment with solutions for a broad range of demanding industries. For 60 years, NETZSCH Pumpen & Systeme GmbH has served markets worldwide with its NEMO® progressing cavity pumps, TORNADO® rotary lobe pumps, grinding machines, dosing systems and accessories, providing customized, sophisticated solutions for applications in every type of industry. NETZSCH Pumps North America, Exton, Pennsylvania, is a manufacturer of progressing cavity and rotary lobe pumps, as well as grinding and dispersing equipment.

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