Technology to replace pumps and macerators

Novel technology could replace pumps and macerators in paper recycling plants saving costs through lower energy consumption and reduced maintenance

Novel technology could replace pumps and macerators in paper recycling plants saving costs through lower energy consumption and reduced maintenance.

Operating within an energy-intensive, highly competitive industry means that paper-recycling businesses are keen to improve the process efficiency and save costs through lower energy consumption and reduced maintenance.

Two areas offering great potential for savings are the de-inking process and hydrapulpers.

Both the washing and floatation de-inking processes are heavy consumers of energy due to the mechanical macerators and pumps required.

Furthermore, worn equipment tends to raise the energy consumption as well as leading to a substantial maintenance overhead.

Should excessive wear lead to stoppages and/or unplanned maintenance, the direct and indirect costs can become substantial.

An innovative alternative to traditional macerators and pumps is the PDX fluids handling system from Pursuit Dynamics.

Moreover, a single PDX unit can also perform the dual roles of macerating and pumping in appropriate applications.

Pursuit Dynamics owns the intellectual property underlying the novel system that is derived from a marine propulsion application.

The system is the subject of 15 patent applications resulting from three years of research, computer modelling and simulation, together with extensive validation using physical prototypes, and has cost in excess of UK PDS4million.

A mobile in-field demonstration plant and dedicated test facilities are available for demonstration either at Pursuit headquarters or at a location of the customer's choice.

A broad range of liquids are readily processed, including those with extreme viscosities and high solids contents.

Driven by readily available steam - of which neither high pressure nor high volume is necessary - the PDX unit has no moving parts and can be manufactured from a range of materials, or accept coatings or liners to provide excellent abrasion resistance In addition, compared with conventional macerators and pumps, the PDX system requires minimal maintenance, and is virtually impossible to block.

In addition the system is intrinsically safe and extremely effective in hostile chemical environments.

Steam is injected into what is, essentially, a plain round tube via a series of nozzles arranged around the circumference.

Energy transfer to the process fluid is produced by momentum transfer of the steam, from the pressure drop when the steam condenses, and from the development of a controllable supersonic shock wave.

Air, or other gases, fluids or solids, can also be naturally entrained into the low-pressure zone to boost the performance and enhance the natural mixing effect.

The supersonic shock wave zone can be generated across the full bore of the processed fluid.

This shock zone increases the energy transfer and has a macerating effect on any semi-solids present.

Process fluids are drawn into this low-pressure zone at a typical linear velocity of 8-10 m/s.

If the process fluid is water, the effect will be to pump the water, with the condensation energy of the steam resulting in a small temperature increase in the fluid flow.

However, the process can be controlled in such a way as to intentionally raise the temperature significantly higher if desired.

When solids - such as saturated paper or board - are added to the process flow, the shock zone breaks down the material without any need for mechanical macerators, blades or moving parts of any kind.

Furthermore, staples, paper clips or other debris pass straight through without clogging or blocking.

If a suitable wear-resistant liner or coating is used, abrasive objects will not cause any damage, and the steam injection principle ensures that the nozzles are self-cleaning.

The system is available in a number of different sizes but a 47 mm diameter bore system will typically produce flowrates of up to 65,000 litres/hour, but there is no significant limit on the size of the units that can be designed and built and, therefore, the maximum flowrate is practically unlimited.

A single PDX unit can also achieve a considerable suction head, depending on the steam pressure applied, or multiple PDX units can be used in series to generate additional suction head.

Returning to de-inking, the floatation process requires the addition of surfactant chemicals; while conventional de-inking systems need another pump to add these, the PDX system can also entrain other fluids, thereby eliminating the need for further pumps.

Utilising the low pressure available within the unit, additional fluids, gasses or powders can be naturally drawn into the process and they immediately become thoroughly mixed with the process fluid as it passes through the shock zone.

If the entrainment aspect of the PDX system is utilised for the addition of surfactants - or, indeed, any other chemicals - the design enables appropriate materials to be used in its construction so as to make it impervious to hostile solutions.

Aside from the de-inking process, the PDX system can also be used to enhance, assist or even replace the mechanical hydrapulper.

As with de-inking, the PDX system can perform both the macerating and pumping roles, though the PDX system has the added advantage that it could also be used in conjunction with suitably configured valves to pump the finished pulp into storage tanks in readiness for the ensuing screening and cleaning processes.

In common with the application of the PDX system to de-inking, the pumping and maceration in a hydrapulper would be immune to damage and blocking by debris, and the system would require virtually no maintenance.

The unique solids handling capabilities of the system, and the absence of any intrusions into the pipeflow, rotating components, or lubrication requirements greatly enhances the availability and minimises forced outages.

Consequently the cost of ownership can be considerably lower than conventional systems.

For waste paper recycling, the PDX system also offers several other secondary advantages.

For example, it is intrinsically safe and, having no moving parts, there is never any risk of oil or grease contaminating the pulp; the system is also virtually silent in operation and causes less vibration than equipment that utilises rotating components.

Lastly, the PDX system is extremely environmentally friendly, which may be seen as a bonus in an industry concerned with recycling.

Pursuit Dynamics is currently looking for suitable partners to licence or adopt this system.

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