1. Field of the Invention
This invention relates to the measurement of the flow rate of weak cell liquor produced in a chlor-alkali cell. It further concerns the use of a weir-type flow meter for the purpose indicated.
2. Description of the Prior Art
In the operation of a cell room containing a plurality of chlor-alkali cells, it has not been usual to determine, regularly and with accuracy, the rate of production of weak cell liquor from an individual cell. When such a determination has been made, it has been usual to use merely a bucket and stop watch. Such a practice is inconvenient and somewhat dangerous, in that it involves the handling of a hot (approximately 90.degree. Centigrade) solution of caustic.
The rate of production of weak cell liquor from an individual cell gives an important indication of how well or poorly an individual cell is currently performing. In one kind of commercial cells of the diaphragm type, the flow rate of weak cell liquor being withdrawn from the cell may range from about two to seven liters per minute. In other cells, the range may be somewhat different. Typically, a cell which has recently been renewed by having its diaphragm replaced will give a flow rate on the higher end of the range mentioned above, and as the cell operates for several weeks or months, the observed flow rate tends to decrease. From time to time, it is possible, in the operation of a diaphragm-type cell, to adjust (increase slightly) the level of the head on the anolyte side of the cell and thereby increase the flow rate. Ultimately, however, because of the buildup of a gel or of insoluble particles of alkaline-earth hydroxides which are formed because of alkaline-earth metal ions contained as an impurity in the brine fed to the cell, the rate of flow through the diaphragm decreases, even when the maximum available head is used, to a value such that further operation becomes uneconomical. In order to keep a cell room containing a great number of such individual cells operating on a smooth and satisfactory basis, it would be highly desirable to have a convenient means whereby the rate of flow of weak cell liquor leaving each individual cell could be easily and conveniently determined.