Maguire: Super-high-capacity LPD ™ dryer cuts energy costs

A new model of the Maguire (R) Low Pressure Dryer (TM) (LPD (TM)) with five times the maximum capacity of the next-largest LPD unit makes the substantial cost savings, reduced heat history, and other advantages of vacuum drying available to a vast new range of plastics processors, it was announced today by Maguire Products, Inc., which will introduce the model at NPE 2003 (Booth 9101).
The new Maguire LPD-1000 resin dryer accommodates processing machine throughputs up to 1000 lb/hr. (450 kg/hr). Like smaller LPD models, it requires one-sixth of the time and as little as 20% of the energy needed by conventional hot-air/desiccant dryers to properly dry resin. Until now, these advantages were unavailable for processing operations with hourly outputs in the range of 200 (90 kg) to 1000 lb.

Some examples of such operations are:

Polyester (PET) preforms and bottles. While throughputs of these parts typically exceed 500 lb. (225 kg) per hour, until now the highest-capacity LPD dryer was the LPD-200, for thgroughputs up to 200 lb. (90 kg) per hour.

High-volume extrusion of sheet, film, and other products.
‘The availability of a high-capacity vacuum dryer is a real breakthrough for producers of PET performs and bottles because vacuum drying subjects resin to 85% less exposure to elevated temperatures than conventional hot air/desiccant dryers,’ said B. Patrick Smith, vice president of sales and marketing. ‘This means substantially less property degradation as measured by falloff in intrinsic viscosity and by discoloration.’
Dimensional Scale-Up with Capacity Increase Is Less than for Desiccant Dryers
While the increase in throughput between the LPD-200 and the LPD-1000 is five-fold, the scale-up in dimensions is proportionally less. The new dryer is 58 in. wide, 58 deep, and 80 high (147 by 147 by 203 cm), compared with 31 by 32 by 70 in. (79 by 81 by 178 cm) for the LPD-200. The LPD-1000 can be deployed as a beside-the-press dryer, be mezzanine-mounted above the processing machine, or serve as a central unit equipped with multiple take-away ports for multiple processing lines.
‘The lowest-capacity LPD dryer is smaller to start with than a conventional dryer of equivalent throughput rating, and the difference becomes greater as capacity increases,’ said Smith. ‘Because of its simpler design, smaller batch size, and shorter drying cycle, the LPD can be scaled up without the substantial increases in the size and weight required for a desiccant dryer. There are no drying hoppers or desiccant bends, and the blowers required are much smaller. The massive hardware of a large-capacity desiccant dryer and the size of the structural components required to support it make this conventional equipment far more expensive than an equivalent LPD machine.’
Unique Technology Is Key to Energy Savings, Speed of Drying, and Speed of Color Change
The LPD dryer differs radically from conventional hot-air/desiccant dryers in two ways: 1) instead of flowing hot, dry air over the pellets to slowly draw the moisture out, the patented LPD dryer uses vacuum to reduce the boiling point of water, quickly turn the moisture into water vapor, and literally pull the water vapor from within the pellets; and 2) the LPD dryer carries out heating and vacuum drying simultaneously in separate stations, making possible small batches while in effect transforming a batch process into a continuous one that keeps pace with the throughput of the plastics processing machine.
The small batch size and short drying cycle of the LPD dryer make it possible to shorten Monday morning cold startups from several hours to less than an hour, adding that much more to weekly production time. Also increasing productivity is the three-station indexing system of the dryer, which makes possible color and material changes on the fly, eliminating downtime.
Another source of cost savings is the elimination of desiccant, which, in a conventional dryer, becomes saturated and must be regenerated by a heating and cooling process so it will
again be able to absorb moisture. The energy used in this process is lost to the ambient environment. In addition, desiccant degrades over time and must be replaced on a regular basis.
Besides the LPD-1000 and LPD-200 models, Maguire also offers the LPD-100 (which accommodates processing-machine throughputs of up to 100 lb/hr. or 45 kg/hr) and the LPD-30 (30 lb/hr. or 13.6 kg/hr).

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