| 摘要 |
<p>An eductive flow loop has an inlet leg conduit projecting into an exhaust stack and an outlet leg conduit. A sample of gaseous combustion by-products is withdrawn from the exhaust stack into the inlet leg conduit and flows to the outlet leg conduit. A portion of the sample is drawn through a convective flow loop conduit and a gas sensing device and back to the outlet leg conduit and therefrom back into the exhaust stack. A counterflow device is positioned in the outlet leg conduit between the exhaust stack and the convective flow loop conduit. The counterflow device includes a portion of the outlet leg conduit that communicates with the exhaust stack and a blowback conduit connected to the outlet leg conduit. A stop member is movably positioned in the blowback conduit. When the fluid pressure in the blowback conduit is greater than the pressure of the gas sample flow, the stop member moves into the outlet leg conduit to block flow to the exhaust stack. Fluid flow is thus directed from the blowback conduit through the outlet leg conduit in a direction opposite to the normal direction of flow of the gas sample through the eductive and convective flow loop conduits. The counterflow of fluid dislodges particulate matter that builds up on the inner wall of the loop conduits when wet and dirty gas is sampled by the gas analyzer and/or prevents an explosive mixture of gases from entering the gas analyzer.</p> |
