Humidity sensing system

摘要

A humidity sensor and filter assembly are housed within a cylindrical barrel that is positioned in a process gas stream such as combustion flue gas. A portion of sample flue gas is conducted through the barrel and the filter assembly past the sensor located inside the filter so that accurate humidity measurements can be taken. Unwanted flue gas particulate matter accumulated on the outside surface of the filter is ejected by pulsed purge gas admitted into the filter to reverse the flow through the filter. In one embodiment a heat exchange chamber preheats the purge gas. In another embodiment the pulsed purge is supplied by a reciprocal piston contiguous with the internal volume of the filter that reverses the flow through the filter using the process gas.

主权项

1. A device for sensing humidity in a stream of process gas, comprising:
elongate cylindrical barrel constituting a main body of the device, said barrel including a process gas inlet port and an outlet port, said outlet port being in fluid communication with said inlet port through a filtration duct, said ports located within the process gas stream so as to conduct a continuous flow of a slip stream of said process gas stream past a humidity sensor; a filtration assembly comprising a filter defining an enclosed internal volume housing the humidity sensor, said assembly providing said sensor with a protective barrier against contact with solid matter within said process slip stream; a source of purge gas; a purge gas conditioning chamber within said barrel partially defined by a sidewall thereof, said chamber being so disposed as to receive a flow of purge gas originating from said source at a first end and to equalize the purge gas temperature and humidity approximately with the process gas stream by direct contact between the purge gas and the slip stream gas; and valve means for discharging said purge gas from a second end of said conditioning chamber into said filter internal volume thereby reversing the gas flow direction through the filter to clean the outer surface of the filter.