Moisture extractor system for gas sampling

An apparatus for sampling gas obtained from a stream of products of combustion, the apparatus comprising:

• a probe tube having a tip positionable in the stream of products of combustion;
• a sample dryer tube connected in fluid communication with an end of the probe tube opposite the tip;
• a purge gas tube having the sample dryer tube received therein along a lengthwise axis of the purge gas tube, the purge gas tube and the sample dryer tube defining a space therebetween;
• a source of purge gas which urges a purge gas through the space in a first direction;
• a sample pump which urges through the sample dryer tube in a second direction opposite the first direction a sample of gas obtained from the stream of products of combustion via the probe tube;
• and
• a sensor which detects a constituent in the sample of gas exhausted from the sample dryer tube, wherein:
• the purge gas entering the space contains less water vapor than the sample of gas;
• the sample dryer tube is formed at least in part of a hydrophilic membrane;
• and
• water vapor contained in the sample of gas is conveyed through the hydrophilic membrane part of the sample dryer tube to the purge gas flowing in the space so that the purge gas exhausted from the space contains more water vapor than the purge gas entering the space and the sample of gas exhausted from the sample dryer tube contains less water vapor than the sample of gas entering the sample dryer tube.

A gas sampling apparatus comprising:

• a source of dry purge gas;
• a sample dryer tube positioned inside a purge gas tube, the purge gas tube and the sample dryer tube defining a space therebetween for receiving a stream of dry purge gas from the source of dry purge gas;
• a sample pump connected to obtain a sample of gas from a stream of products of combustion and to cause the obtained sample of gas to flow through the sample dryer tube;
• and
• a heater for maintaining a temperature of the sample of gas entering the sample dryer tube one of at and above a dew point temperature of water in the sample of gas, wherein:
• the stream of dry purge gas in the space flows in a direction opposite the sample of gas in the sample dryer tube;
• the purge gas entering the purge gas tube contains less water vapor than the sample of gas;
• and
• the sample dryer tube is formed at least in part of a hydrophilic membrane that enables water vapor contained in the sample of gas to be conveyed therethrough to the stream of dry purge gas thereby reducing the amount of water vapor in the sample of gas.