Desulfurization pump wear problem
The desulfurization slurry circulating pump is a large-scale equipment after the relay heat exchanger and booster fan of the desulfurization system. It’s usually a centrifugal type. It directly draws the slurry from the bottom of the tower for circulation. It’s the pump with the largest flow rate and the most demanding conditions in the desulfurization process, and corrosion and abrasion often cause its failure. Its characteristics mainly include:
(1) Strongly corrosive
In a typical limestone (lime)-gypsum desulfurization process, the pH value of the slurry at the bottom of the tower is generally 5-6, and the pH value can reach 6-8.5 after adding desulfurizer (the pH value of the circulating pump slurry and the operating conditions of the desulfurization tower. It is related to the addition point of the desulfurizer); Cl- can be enriched in more than 80,000mg/L, and it will be strongly corrosive under low pH conditions.
(2) Strong abrasiveness
The slurry at the bottom of the desulfurization tower contains a large number of solid particles, mainly fly ash and desulfurization medium particles. The particle size is generally 0-400μm, 90% or more is 20-60μm, and the concentration is 5%-28% (mass ratio). These solid particles are highly abrasive.
In the desulfurization system, the slurry conveyed by the circulating pump often contains a certain amount of gas. In fact, the slurry conveyed by the centrifugal circulating pump is a gas-solid-liquid multiphase flow, and the influence of the solid phase on the pump performance is continuous and uniform, and the influence of the gas phase on the pump is far more complex and more difficult to predict than the solid phase.
(4) The working conditions of common desulfurization pumps
PH value: 5.5
Solid content of slurry: 8~17%
Main ingredients: CaSO4**642; 2H2O
The desulfurization pump impeller and pump casing are subject to medium corrosion and solids erosion and wear during long-term operation. The impeller life cycle is about one year, and the pump casing can be used for more than one year, but local corrosion and wear are severe.