Unidirectional Dual Zone
Historically, unidirectional refiner plates provided some energy savings at the expense of reduced pulp strength properties. Over time, the development of on-line measurement techniques has led to significant plate design improvements.
The key to unidirectional plate design performance is the pulp residence time inside the actual refining zone. The J&L Stabilizer design incorporates many design advances that contribute to higher throughput and pulp strength properties.
- Good Fiber Quality
- Enables Higher throughput
- Improved Refiner Stability
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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.