Two basic plate designs are prevalent in the refiner industry: constant angle and parallel bar. Many variations on these designs are also utilized in today’s market. The constant angle concept has all of the bars at the same angle relative to the centerline of the circle. The parallel bar concept features only one bar per sector at the given angle, with the other bars in the sector at progressively higher angles.
Traditional Parallel Bar Flared/Single Zone
The most efficient way to achieve low intensity refining is to provide a refiner plate that has many bar edges, yet still meets hydraulic and breakage resistance requirements. A comparison of the two plate concepts for the same size refiner will show that parallel bar configuration is the clear winner, because it provides lower intensity and more bar edge crossings [higher km/revolution].
Even when using multiple zones in a radial bar design it is still impossible to develop the same amount of bar edge crossings as the comparable parallel bar plate design without changing the bar/groove configuration significantly.
Parallel Bar features
- Alternating Deep Groove
- ReverseFlare provides less plugging due to flared groove from ID to OD
- Single Zone/Radial Feed Grooves for less plugging, better flow and better plate life
- Multiple Zones for placing sub surface dams at ID and surface dams at OD, or vary dam density
- Strategically Placed Dams provide better de-shiving/capacity
- Overhung adjusts hydraulic flow
- Underhung adjusts hydraulic flow and saves energy
- Low to High Bar Edge Crossings
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Refiner Plate Design
Different refiner applications require different plate designs as system optimization is undertaken.
Fiber treatment, hydraulic capacity and breakage resistance are three critical parameters that must be considered when designing and applying low consistency refiner plate patterns.
A paper mill can optimize its low consistency refining operations on two fronts:
- Monitoring and eliminating as many detrimental hydraulic, mechanical and process conditions as possible.
- Ensuring that the proper plate designs and alloys have been selected.
By working together with our papermakers, J&L Fiber Services seeks to develop strategies to optimize the unique needs and performance of a particular paper mill.
Given the difficulties of being able to control all of the many process variables, refiner plate design becomes extremely critical. The key design parameters, relative to delta P (refiner pressure control) are: groove depth, groove profile, number of bars & total pumping angle.
The intensity of refining that is required will determine the bar width/groove relationship,or pitch. However, groove width should be altered to optimize the throughput rate. This can be done without changing the pitch or intensity by altering the bar width correspondingly.
A special caution when altering groove depth for flow control: While no appreciable negative effect will occur when groove depth is reduced for lower flow rates, increasing groove depth poses some risks. First, it is less efficient than increasing groove width. Second, it can have a negative effect on energy efficiency, because increasing groove depth increases the no-load energy required to spin the rotating element in the stock slurry.
Bar angle is significant to the extent that it affects the delta P and is a tool for hydraulically balancing the refiner.
The relatively infrequently used practice of running the low consistency refiner plates in the holdback position can effectively compensate for low flow conditions which are detrimental to fiber quality, plate life, etc. During holdback, the intersecting bar angle between the rotor and the stator is moving towards the center line of the refiner rather than towards the periphery of the disc, as in pumping position. Holdback will increase the turbulence in the grooves and the plate gap.