Methods for detecting and/or measuring the concentration of oxygen in aqueous liquids such as boiler feed water

摘要

In a process for detecting and measuring the oxygen content of aqueous liquids (e.g. boiler feed water), the liquid is treated with an inert gas, and the gas (then containing absorbed oxygen) is brought into contact with a galvanic cell, which generates a current proportional to the oxygen content of the water. The apparatus used is first calibrated with water containing known amounts of oxygen. An inlet 19 for the water under test is sealed into a chamber 18, connected through a vertical tube 20 to the base of a chamber 1 from which the water flows away through a device 22 for maintaining a constant head. Within the chamber 1 is mounted a galvanic battery, the cathode 7 of which is sensitive to oxygen, generating a current measured between the electrodes 9, 11. The top of the chamber 1 is connected to a generator for hydrogen 23, and to a vessel 14 containing palladium-aluminium catalyst, mounted above the water inlet chamber 18. In operation, the apparatus is filled with hydrogen, bubbles of which are drawn into tube 20 by the downward flow of water, and absorb at least some of the oxygen contained in the water. The water is discharged through the constant level overflow 22, and the mixed gases flow around the galvanic cell and pass into the catalytic chamber 14 where any oxygen combines with hydrogen by silent burning, leaving oxygen-free hydrogen for re-cycling. The loss of hydrogen gas draws up acid from the bottom of the tube 24 to contact an electrode 27 which with electrode 28 is connected to a battery generating hydrogen. When the hydrogen is replaced, the back pressure forces the acid below the electrode 27. Any excess pressure is vented through the valve 31. The galvanic cell is of the type described in Specification 707,323, and in the preferred form consists of silver wire cathode, an anode of finely-divided cadmium and dilute potassium hydroxide.