Application of Density Meter and PH Meter in Measurement

1 The cause of slurry fouling It is well known that during the course of forming a gypsum after a series of reactions, limestone slurry will have a lot of soft dirt or hard dirt if the PH value of the slurry changes violently or the oxidation degree decreases; even when the concentration of the final product of gypsum exceeds At the absorption limit of the slurry, the gypsum begins to deposit in the form of crystals. When the relative saturation concentration reaches a certain value or higher, many suspended nuclei are formed. Such nuclei are easily adsorbed on the inner wall of the vessel or pipeline. , resulting in system fouling or blockage of the piping system.

2 Slurry Measurement and Washing System Introduction Wudang's desulfurization density meter design uses electromagnetic type; PH meter is a glass tube electrode type, easy to wear, which requires the system medium flow speed can not be too high, and the slurry in the tiny Nucleation at a low flow rate and easy attachment to the surface of measuring instruments and pipes, or even plugging of pipes, is a time-critical flush.

At present, the flushing of the density meter and PH meter is based on the condition that the gypsum slurry pump is stopped (system flow is shown in Figure 1). The specific control concept is: First, stop the pump; then, close the pump outlet. Finally, the industrial water flushing door is opened for flushing (Note: The pipelines in the system are all equal-diameter, the pH meter is an adjustable manual door, and the normal opening is 30%-45%, so as to ensure the normal flow density of the medium. If the unit load is high for a long period of time, the pump cannot be stopped for flushing, which results in unavoidable errors for the measurement, and also poses a great hidden danger for the safe and stable operation of the system.

3 The necessity of increasing the online water flushing The desulfurization system is designed based on the sulfur content in the fuel is 0.6%, the sulfur dioxide content at the inlet of the desulfurization system is 1400mg/Nm3, and the sulfur dioxide content in the limit operation inlet is not more than 1800mg/Nm3. In fact, with the shortage of fuel supply, the existing coal source can not meet the design requirements, resulting in a great deviation of the inlet sulphur dioxide content from the design value. Taking August of 2007 as an example, the sulphur dioxide content of the desulfurization system of Wudian Company often exceeds 290mg/ Nm3 exceeded the instrument's maximum measurement limit, and the average inlet sulfur dioxide content in August exceeded 2200 mg/Nm3. Under such conditions, due to the rapid increase in the density of the desulfurization absorber tower, the bottom of the absorber tower will excessively deposit crystal nucleus or scales, which will inevitably aggravate the pipeline wear of the circulation pump, increase the current of the stirrer, and long-term operation of the slurry pump. and many more. In addition, densitometers and pH meters do not work properly, resulting in serious distortion of the measured data. For example, when the pH is low, the sulfite solubility sharply increases, the sulfate solubility slightly decreases, and gypsum is generated and precipitated in a large amount in a short time. , produce hard scale. The decrease in the solubility of high-sulfite sulfite can cause sulfite to precipitate and produce soft dirt. When operating at alkaline pH, calcium carbonate hard scale is produced. Seriously affect the safe and stable operation of the system. In addition, the maintenance of the density meter PH meter is greatly increased. In view of the above reasons, it is necessary to increase the density meter and PH meter online flushing system in the desulfurization system.

4 transformation program description 4.1 flushing pipeline transformation 4.1.1 in the slurry back absorber installed before the new valve 1 (electric switch type);

4.1.2 install a flush tee and new valve 2 (electric switch type) on the horizontal pipe below the current density meter branch;

4.1.3 install a large and small flush control valve 3 (electric switch type) in the current density meter bypass branch;

4.1.4 Installation of Tee and New Valve 4 (Electric Switch Type) in Front of the Original Flushing Door

4.2 Flushing scheme After the flushing door and pipeline reformation are completed, two online flushing methods are designed in a sequential manner. The specific flushing scheme is as follows:

4.2.1 Small flushing: Automatic flushing every four hours, first confirm the closure of the density meter, PH sample total sampling valve, then close the new valve 2 and add the new valve 3, open the new valve 1, and finally open the new valve 4 When the densitometer is flushed and timed, the new valve 2 is opened after three minutes, the new valve 1 is closed, the pH meter is rinsed, and the flushing is completed after five minutes. After the new valve 4 is determined to be closed, the new valve 1 and the newly added valve 3 are opened. Finally, the total sampling valve is opened, and the density meter and the pH meter are put back into operation.

4.2.2 Large flushing: Set as a 24-hour flush as required. This type of flushing enhances the flushing of the densitometer. First, make sure to close the density meter and the PH meter total sampling valve. Then close the new valve 2 and the new valve 3, open the new valve 1, and finally open the new valve. 4 Wash the densitometer and record it. Open it after eight minutes. Add new valve 3, close the new valve 1, and simultaneously flush the densimeter and PH meter. After 11 minutes, this time the end of the flush. After the new valve 4 is determined to be closed, the new valve 1 and the new valve 2 are opened. Finally, the total sampling valve is opened and the system is put back into operation. According to actual needs, an automatic termination system is designed for large flushing. When flushing is unnecessary, it can be terminated directly.