Corrosion and protection of petrochemical concrete structure cooling towers

The last edit to this post was made by Wang Wei2 on 2023-10-22 at 18:30. I disagree with this view; I tend to agree with my own perspective. The dissolution equilibrium of carbon dioxide in water follows Henry’s law, while the dissolution equilibrium of calcium carbonate is affected by the blowing action of fans, which reduces the partial pressure of carbon dioxide in the gas phase and disrupts these equilibria, thereby causing corrosion of concrete through dissolution. The hydrolysis of carbonate ions occurs in two steps. The first step is CO3²¯ + H2O == HCO3¯ + OH¯, and the second step is HCO3¯ + H2O == H2CO3 + OH¯. @qugd @leo_0088 @huachan2006 @slayerstar @Zhongyuanren @li*nji @ACHUAN @zhjnavy015 @wamj6566

The last edit to this post was made by qugd on 2023-10-23 at 09:36. Regarding the issue in the post you mentioned, @*nht1, I believe the main cause of damage is the temperature differences between day and night as well as between seasons due to the cold climate in that area; the idea that carbon dioxide accelerates corrosion is completely unfounded. With so many petrochemical plants in the south, why is corrosion not as apparent under the same carbon dioxide conditions? In cold regions, water freezes and expands, causing the ice crystals formed in the tiny gaps in the cement to widen those gaps. This process of weathering occurs day after day, year after year. The moisture conditions around the circulating water towers make this weathering process even more frequent and intense. This is the result of such processes: there are few large, intact separate rocks in the mountains of the north. Of course, this can be avoided by ensuring that the water from the circulating water tower does not fall on the surrounding concrete structures as much as possible, but this is precisely the normal operating environment of the circulating water tower. Applying a coating for coverage or laying a layer of waterproof material yields the same result. Chemical effects play a certain role in facilitating this process, but when it comes to the frequent changes in ice-water conditions in gaps in cold regions, they are not the main factor.

In my opinion, this is due to the accelerated weathering caused by the climate/meteorological conditions in the Daqing area. In the south, where there are also open-loop cooling towers, the weathering and corrosion of the concrete structures are not significant, and the main reason for this is the absence of an ice period. As for the extent of the impact of carbon dioxide in the air, it is difficult to quantify; however, one can refer to structures such as cement-based piles and pedestals in ordinary commercial buildings – the rate of weathering there is not that fast. You can take a look at the cement-hardened surfaces and various structures in the areas surrounding Daqing Refining and Chemical Industry as well as Daqing Petrochemical. The effect of ice crystals on accelerating weathering requires conditions of frequent temperature fluctuations – that is, temperatures above zero during the day and below zero at night. This daily cycle of melting and freezing **accelerates the weathering of concrete structures, and this is a typical situation in the cold regions of the northeast. It is even foreseeable that the sun-facing side of the circulating cooling water tower may experience more weathering than the shaded side.

Having seen everyone’s discussions, they are quite good; I hope everyone will participate in the exchanges.

I would like to propose a hypothesis: under identical conditions, if this phenomenon occurs only in the concrete surrounding the fan when it accelerates, then that must be the cause. If we compare the situations in the north and the south, it’s possible that ice crystal expansion leads to freezing cracks; experiments for comparison can be conducted, or cooling towers under similar operating conditions can be used for comparison between the north and the south, with photographs taken to examine the details such as stone weathering. I am more focused on the effect of cold shock during stormy weather on the rapid release of thermal stress. I welcome experts to discuss this together. @Wang Wei2 @qugd @PeopleFromZhongyuan