PD™–Series Gas Dryers
Perma Pure PD-Series™ gas dryers are multi-tube Nafion® gas sample dryers designed for high flow, high performance gas drying applications. These dryers can be used to dry to -45°C without removing other compounds. Applications for PD-Series gas dryers include gas sample conditioning for continuous emissions and process monitoring. In these applications, sample gases flowing through the Nafion® tubing are dried without removing any of the sample analytes. PD-Series dryers are also used as moisture exchangers in fuel cell applications. Fuel cell exhaust gases transfer their moisture and heat to the dry inlet gases (primarily hydrogen). Finally, PD-Series gas driers can be used in small scale process applications. Process applications take advantage of one or more of the unique properties of Nafion®: highly efficient and selective moisture exchange, ion exchange capabilities, and extreme corrosion resistance.
- Flow rates up to 40 l/m
- Operating temperatures to max. 120° C
- Operating pressures to 45 psi (absolute)
- Straight or coiled configuration
- Corrosion resistant
- Standard dew points to – 25° C, with lower values possible (contact factory)
- No loss of analytes
- No moving parts
PD-Series dryers consists of a bundle of 0.030″ O.D. Nafion® tubes housed within a single large tube shell. Feed gas flows within the Nafion® tubes while water vapor absorbs into the tubular membrane walls and is removed. Moisture permeating the tubing is carried away by a dry purge gas within the shell that flows counter-current to the feed. Purge gas should be instrument quality air (-40°C dew point) or nitrogen flowing at two to three times the sample flow rate.
Perma Pure offers the PD-Series dryer with three sizes of Nafion® tubing and in a variety of lengths and connection types. Choose the size based on your flow rate and dryness requirement and build your PD dryer according to the selection guide and the part number table below:
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Recommended Sample Gas Flow Rates:
2-10 lpm: PD-050T Series
4-20 lpm: PD-100T Series
10-40 lpm: PD-200T Series
PD Gas Sample Dryer Performance Curves
The Performance curves above are based upon an inlet dew point of 20°C. For conditions higher than ambient temperature, it is assumed that the first half of the dryer will be used to bring the dew point down to ambient. For this reason, read the value of the next shorter dryer. For example, a stream with an initial dew point of 50°C, flowing at 2 slpm; a PD-50T-24 should yield an outlet dew point of -6°C, the performance of the 12″ unit. Visit the Purge Gas Configurations page to learn more about the purge methods Perma Pure customers deploy in their equipment.
Calculating PD Series Pressure Drop
PD-50T;
ΔP (psid) = 0.0056 * Flow rate (splm) * Length of dryer (inches)
PD-100T;
ΔP (psid) = 0.0028 * Flow rate (splm) * Length of dryer (inches)
PD-200T;
ΔP (psid) = 0.0014 * Flow rate (splm) * Length of dryer (inches)
PD Series Dimensions
| Model Number | Overall Length | Active Length | Port-to-Port | Shell |
| PD-50T-12MPS, MPP | 15.3″ | 12.5″ | 11.8″ | 9.7″ |
| PD-50T-24MPS, MPP | 23.3″ | 20.5″ | 19.8″ | 17.7″ |
| PD-50T-48MPS. MPP | 47.3″ | 44.5″ | 43.8″ | 41.7″ |
| PD-50T-72MPS, MPP | 71.3″ | 68.5″ | 67.8″ | 65.7″ |
Perma Pure has created a series of short video presentations to describe the basic functionality of some of our products. The videos are posted below.
Nafion Tubing Basic Functionality
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Perma Pure MD and PD Gas Sample Dryers Basic Functionality
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