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PET Energy-Saving Drying Systems

Today, most new PET drying systems sold are based on using a desiccant wheel dryer. There is no doubt that the wheel dryer provides significant energy, space and maintenance savings over a system using a conventional dual bed desiccant dryer and PET processors recognize the advantages of wheel dryers.

The key components of the new PET Desiccant Wheel Drying systems are:

• Desiccant wheel dryer
• Multi-zone drying hopper
• Electric or optional gas-fired process heater
• Cyclone
• Self-cleaning "pulse"-type dust collector

One manufacturer limits the required equipment to the components listed above, controls energy-saving features automatically and claims better efficiency, lower initial cost and reduced lifetime maintenance. In this system, patented features automatically adjust drying hopper outlet temperature as well as and blower and desiccant wheel speed to save energy and ensure process consistency.

Another manufacturer recommends that, in order to achieve maximum efficiency, two dryers, two gas-fired process heaters, two cyclones and two “pulse-type” dust collectors are required. In addition, this system currently requires personnel to monitor readings from multiple probes and make manual adjustments to temperature set points in the controller.

Some manufacturers offer both dual flow and single flow dryers and hoppers. The Single Flow systems are typically used for PET applications with a high percentage of virgin resin such as preforms. Dual Flow systems are typically used in applications that include a crystallizer.

The advantage of using of a gas-fired process heater depends entirely on the electric cost per kwh for the processor and the size of the dryer. The larger the dryer throughput - the greater the savings. PET processors with throughputs of 2500 lb./hr., or more, per line stand to gain most. If the price of electricity is $.07/kwh, savings are noticeable but if the price is closer to $.10/kwh (the national average) savings can be outstanding - with an ROI of 10-18 months, depending on dryer throughput.

Energy Rebates have become quite popular in recent years. Depending on where you plant is located, there may be county, state, federal or energy company rebates available to greatly offset the cost of new, energy-saving equipment. Some dryer manufacturers are prepared to help you find the source of these rebates and help provide the energy-saving documentation required to capitalize on the rebate programs.