Corrosion of the desulfurization slurry circulation pump

Generally, there are three main causes of damage to the impellers of slurry circulation pumps: cavitation, wear, and corrosion. Its characteristics are as follows: Cavitation: It generally occurs at the inlet, as this is the low-pressure area of the pump; the fluid vaporizes due to the low pressure or vacuum in the pump inlet, resulting in cavitation. The holes that form are usually large in size. Wear: It generally occurs on the outlet side of centrifugal pumps, or on the outside of axial flow pumps (mixed-flow pumps), as the relative flow velocity in these areas is high, leading to rapid wear. Corrosion: It initially manifests as small, uniform spots that gradually grow larger; therefore, it affects the entire impeller as well as other components made of the same material. 　　 By the way, whether the filter screen of the slurry circulation pump is actually useful is also a matter of debate. Filters are useful for preventing loosely installed nozzles or similar components from falling off during operation and entering the slurry circulation pump, thereby causing damage. However, if the filter becomes clogged during operation, it can easily lead to vaporization in the slurry circulation pump, which in turn results in equipment damage. :victory:

The desulfurization slurry circulation pump is a large-scale device in the desulfurization system, following the heat exchanger and the booster fan; it is usually of centrifugal type. This pump draws slurry directly from the bottom of the tower for circulation, and it is the pump with the highest flow rate and the most demanding operating conditions in the desulfurization process. Corrosion and abrasion often lead to its failure. Its main characteristics are as follows: 1. Cavitation resistance: In desulfurization systems, the slurry pumped by the circulation pump often contains a certain amount of gas. In fact, the slurry transported by centrifugal circulation pumps is a gas-solid-liquid multiphase flow; the effect of the solid phase on pump performance is continuous and uniform, whereas the effect of the gas phase on the pump is much more complex and harder to predict ； 2. High abrasiveness: The slurry at the bottom of the desulfurization tower contains a large amount of solid particles, mainly fly ash and desulfurization medium particles. The particle size ranges from 0 to 400 μm, with over 90% falling within the 20 to 60 μm range; the concentration is 5% to 28% (by mass). These solid particles (especially Al2O3 and SiO2 particles) possess high abrasiveness ； 3. High corrosivity: In the typical limestone (lime)-gypsum flue gas desulfurization process, the pH value of the slurry at the bottom of the tower is generally between 5 and 6; after the desulfurizing agent is added, the pH value can reach 6 to 8.5 (the pH value of the slurry in the circulation pump depends on the operating conditions of the desulfurization tower and the point at which the desulfurizing agent is added) ； Cl- can be enriched to over 80,000 mg/L, and under low pH conditions, it exhibits strong corrosivity. Solution: The issue can be resolved using polymer composite repair technology