Industrial Plate Heat Exchanger Scaling Cleaning Services

Plate heat exchanger scaling cleaning method:

1, The choice of cleaning agent

Cleaning agent selection, the current use of acid washing, which includes organic and inorganic acids. Organic acids are: oxalic acid, formic acid and so on. Inorganic acids are: hydrochloric acid, nitric acid and so on. According to the heat exchanger scaling and process, material and scale composition analysis:

(1) heat exchanger circulation area is small, the internal structure is complex, cleaning fluid if precipitation is not easy to discharge.

(2) heat exchanger material is nickel-titanium alloy, the use of hydrochloric acid as a cleaning fluid, easy to produce strong corrosion of the plate, shortening the service life of the heat exchanger.

Through repeated tests found that the choice of formic acid as a cleaning fluid is very effective. Add buffer and surfactant in the formic acid cleaning solution, the cleaning effect is good, and can reduce the corrosion of the cleaning solution on the plate sheet. Through the chemical test study on the scale sample, it was shown that formic acid could effectively remove the scale. Through the acid immersion test, found that formic acid can effectively remove the scale attached to the plate, at the same time it is small on the corrosion of the heat exchanger plate.

2, The basic principle of scale removal

(1) dissolving effect: acid solution is easy to react with calcium, magnesium, carbonate scale, generating soluble compounds, so that the scale is dissolved.

(2) stripping effect: acid solution can dissolve the metal surface oxides, destroy the combination with scale. Thus, the scale attached to the surface of the metal oxide stripping. And fall off.

(3) gas lifting effect: acid solution and calcium, magnesium, carbonate scale reaction, produce a large amount of carbon dioxide. Carbon dioxide gas in the process of overflow. For difficult to dissolve or dissolve the slow scale layer, has a certain lift power, so that the scale from the heat exchanger heated surface off.

(4) loosening effect: for containing silicate and sulfate mixed scale, due to calcium, magnesium, carbonate and iron oxides dissolved in the acid solution, the residual scale will become loose, it is easy to be flowed by the acid solution flushed down.

3,Cleaning scale process requirements

(1) pickling temperature: enhance the pickling temperature is conducive to improving the descaling effect, if the temperature is too high will exacerbate the corrosion of the pickling solution on the heat exchanger plate, through repeated tests found that the pickling temperature is controlled at 60 ~ E is appropriate.

(2) pickling solution concentration: according to repeated tests, pickling solution should be formic acid 81.0%, water 17.0%, buffer 1.2%, surfactant 0.8% of the concentration of the preparation, the cleaning effect is good.

(3) pickling method and time: pickling method should be static immersion and dynamic circulation combined method. Pickling time for the first static immersion 2h, and then the dynamic cycle 3 ~ 4h. In the pickling process should be sampled frequently pickling concentration, when the difference between the two adjacent concentration of the test is less than 0.2%, it can be considered that the end of the pickling reaction.

(4) passivation: after the end of pickling, plate heat exchanger surface scale and metal oxides are dissolved off the vast majority of the exposure of brand new metal, easy to corrode, so after pickling, heat exchanger plate passivation treatment.

4, Cleaning scale specific steps

(1) flushing: before pickling, the heat exchanger first open flushing, so that the heat exchanger internal no mud, scale and other impurities, so as to improve the effect of pickling, but also to reduce the acid consumption of pickling.

(2) Pour the cleaning solution into the cleaning equipment, and then injected into the heat exchanger.

(3) pickling: the heat exchanger will be filled with acid solution static immersion 2h. then continuous dynamic cycle 3 ~ 4h. during which every 0.5h alternating positive and negative cleaning. After pickling, if the pH value of the acid solution is greater than 2, the acid can be reused, otherwise, the pickling solution should be diluted and neutralized after discharge.

(4) alkali washing: after the end of acid washing, with NaOH, Na, PO, softened water prepared in a certain ratio, the use of dynamic circulation of the heat exchanger for alkali washing, to achieve acid-base neutralization, so that the heat exchanger plate is no longer corrosive.

(5) water washing: after the end of alkaline washing, with clean softened water, repeatedly rinse the heat exchanger for 0.5h, the residue in the heat exchanger thoroughly rinsed.

(6) Records: the cleaning process, should strictly record the time of each step to check the cleaning effect. In short, after cleaning, the heat exchanger should be pressurized test. Qualified before use.

5, Prevent plate heat exchanger scaling measures

(1) operation of the water quality, the water in the system and the softening tank in the softened water for strict water quality testing, qualified before injecting into the pipe network.

(2) When the new system is put into operation, the heat exchanger should be separated from the system for a period of time after the cycle, and then the heat exchanger into the system to avoid impurities in the pipe network into the heat exchanger.

(3) In the whole system, in addition to the dirt separator and filter should be cleaned from time to time, but also should be kept clean in the pipe network to prevent the heat exchanger from clogging.