The characteristics of the medium conveyed by the desulfurization slurry circulating pump (multistage pump) in the power plant
The slurry circulating pump is one of the most important equipment in the power plant desulfurization system equipment. Its main function is to continuously circulate the slurry in the absorption tower so that the sulfur dioxide in the flue gas is completely absorbed.
The characteristics of the medium conveyed by the desulfurization slurry circulating pump in operation
The slurry circulating pump is one of the vulnerable parts, which is mainly affected by the acid corrosion, wear and cavitation of the slurry. Generally, the service life of the slurry circulating pump is about 3 years, and the impeller needs to be replaced in about 1 year.
1. Highly abrasive
The slurry at the bottom of the desulfurization tower contains a large number of solid particles, mainly fly ash, calcium sulfite (CaS03 · Sweep 20), calcium sulfate (CaS04 · 2H20), the particle size is 0 ~ 400μm, 90% above is 20 ~ 60μm, the concentration is 5% to 28% (mass ratio), these solid particles (especially Al203, SiO2 particles) are highly abrasive.
2. Strongly corrosive
In a typical limestone-gypsum desulfurization process, the pH of the slurry at the bottom of the tower is generally 4-6, which is an acidic environment; when the concentration of Cl ions in the absorption tower exceeds 20,000 mg/L, a strong pH will be generated under low pH conditions. Corrosive.
3. Cavitation
In the desulfurization system, the slurry conveyed by the desulfurization slurry circulation 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. The effect of the solid phase on the pump performance is continuous and uniform, and the impact of the gas phase on the pump is far more complex and more difficult to predict than the solid phase. When the liquid delivered by the pump contains gas, the flow rate, head, and efficiency of the pump will decrease. The greater the gas content, the faster the efficiency will decrease. As the air content increases, additional noise and vibration occur in the pump, which can cause damage to the pump shaft, bearings and seals.
The accumulation of gas at the pump suction inlet and the back of the blades will cause the flow resistance to increase or even cut off, and then worsen the working conditions. The amount of cavitation must be increased, the gas density is small, the specific volume is large, the compressibility is large, and the rheology is strong , Small centrifugal force and poor conversion energy performance are the main reasons for the deterioration of pump working conditions. The test shows that when the gas volume (volume ratio) in the liquid reaches about 3%, the performance of the pump will drop sharply. When the inlet gas reaches 20% to 30%, the pump is completely cut off. The centrifugal pump allows the air content (volume ratio) limit to be less than 5%.
