Views:0 Author:Site Editor Publish Time: 2020-05-25 Origin:Site
Before the cleaning, test the plate heat exchanger for leaks and check for internal leakage (the medium leaks from the high pressure side to the low pressure side): drain the medium on both sides of the plate heat exchanger, and charge the reverse phase nitrogen to be cleaned to operating pressure After holding the pressure, leave an open shower or exhaust hole on the other side. If the pressure does not drop, the sealing performance is good. Or check each place where the plate heat exchanger is likely to leak. If an internal leak is found, the plate heat exchanger plate needs to be repaired or replaced.
Wash the plate heat exchanger with hot water (about 50 ℃), control the outlet pressure and flow of the cleaning pump to run under the conditions allowed by the plate heat exchanger, and wash out the scale attached to the plate as much as possible until the plate heat exchanger There is no obvious turbidity at the outlet. Washing with hot water is not only beneficial to reduce the dosage of chemical agents, but also shorten the time of chemical cleaning.
1) Pickling liquid formula. The dosage of nitric acid is 3% -5%, the dosage of LXg-001 is 0.1%, and the temperature is normal temperature.
2) Pickling process conditions and operation. Add circulating cooling water and LX9-O01 corrosion inhibitor in the acid tank to dissolve. Start the pumping cycle and add nitric acid in portions after 20rain to make up about 3% to 5% pickling solution. At the same time, 3 stainless steel hanging pieces were hung in the acid tank to measure the corrosion rate. The pickling time is preferably 2-3h, generally no more than 3h. Judgment of the end point, if the scale mainly composed of calcium carbonate, it can be seen that the foam disappears, the liquid level in the tank drops, the turbidity no longer rises, and the acid concentration is stable to determine the cleaning end point. At the end of cleaning, the hanging piece should be taken out in time to observe the corrosion and calculate the average corrosion rate. Table 2 is the analysis data at the end of the cooler cleaning.
After the pickling is completed, the residual acid solution of the system is discharged to a temporary storage tank for neutralization and discharge. Add a large amount of fresh water to the tank for circulating cleaning. After draining and replenishing until the pH value becomes neutral, stop replenishing and discharging. After pickling, dry the equipment with nitrogen or compressed air. Rinsing is to further replace the residual acid in the plate heat exchanger. According to the cleaning flow chart, the one-pass method for rinsing is more efficient and effective than the circulating method.
If the plates of the plate heat exchanger are corroded under scale, a system evaluation is required to determine the cleaning plan or other measures. 3) Analysis items and frequency during chemical cleaning. Total iron: analyzed once before pickling, then 2 times / h; acid concentration: 2 times / h; turbidity: 2 times / h.