| 摘要 |
PURPOSE:To wash a density measuring tube during the operation of a waste liquor thickener by providing a circuit to store and operate density signals. CONSTITUTION:A liquid level signal is corrected to attain a true liquid level by storing a density signal D1, obtained by measuring a head H1 with a density sensor 2, in a store circuit 5 before a density sensor valve 3 is closed and a washing valve 4 is opened, in the case a washing signal of the density measuring tube 1 is given, and further measuring a head H2 in a waste liquor thickener 7 with a stored signal D2 by means of a liquid level sensor 6. After washing is over, the density sensor valve 3 is opened for comparison of a newly opened density signal D1 and the stored density signal D2, and if the result is D1<D2, the liquid level correction is carried out by the stored density signal D2, while if D1>=D2, the liquid level correction is carried out with the new density signal D1 to attain the true density. As a result, washing of the density measuring tube 1 is feasible during the operation of the waste liquor thickener 7.
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