脱硫泵中的应用
Application of desulphurization pump
脱硫浆液循环泵是脱硫系统中继换热器、增压风机后的大型设备，通常采用离心式，它直接从塔底部抽取浆液进行循环，是脱硫工艺中流量最大、使用条件最为苛刻的泵，腐蚀和磨蚀常常导致其失效。其特性主要有：
The desulphurization slurry circulating pump is a large equipment after the heat exchanger and the turbocharging fan in the desulphurization system. It is usually used in centrifugal type. It directly extracts the slurry from the bottom of the tower to carry out circulation. It is the largest and most demanding pump in the desulfurization process. Corrosion and abrasion often lead to its failure. Its characteristics are as follows:
（1）强磨蚀性
(1) strong abrasiveness
脱硫塔底部的浆液含有大量的固体颗粒，主要是飞灰、脱硫介质颗粒，粒度一般为0～400µm、90%以上为20～60µm、浓度为5%～28%（质量比）、这些固体颗粒（特别是Al2O3、SiO2颗粒）具有很强的磨蚀性
The slurry at the bottom of the desulphurization tower contains a large number of solid particles, mainly particles of fly ash and desulphurization medium, the size of which is generally 0 ~ 400µ m, over 90% are 20 ~ 60µ m, the concentration is 5% ~ 28% (mass ratio), and these solid particles (especially Al2O3, SiO2 particles) have strong abrasiveness.
（2）强腐蚀性
(2) strong corrosiveness
在典型的石灰石（石灰）-石膏法脱硫工艺中，一般塔底浆液的pH值为5～6，加入脱硫剂后pH值可达6～8.5（循环泵浆液的pH值与脱硫塔的运行条件和脱硫剂的加入点有关）；Cl-可富集超过80000mg/L，在低pH值的条件下，将产生强烈的腐蚀性。
In the typical limestone (lime) gypsum process desulphurization process, the pH value of the general bottom slurry is 5~6, and the pH value can reach 6 ~ 8.5 after adding the desulfurizer (the pH value of the circulating pump slurry is related to the operating conditions of the desulfurizer and the addition point of the desulfurizer); the Cl- can be enriched over 80000mg/L and will produce a strong value under the low pH value. Corrosive。
（3）气蚀性
(3) cavitation erosion
在脱硫系统中，循环泵输送的浆液中往往含有一定量的气体。实际上，离心循环泵输送的浆液为气固液多相流，固相对泵性能的影响是连续的、均匀的，而气相对泵的影响远比固相复杂且更难预测。当泵输送的液体中含有气体时泵的流量、扬程、效率均有所下降，含气量越大，效率下降越快。随着含气量的增加，泵出现额外的噪声振动，可导致泵轴、轴承及密封的损坏。泵吸入口处和叶片背面等处聚集气体会导致流阻阻力增大甚至断流，继而使工况恶化，必须气蚀量增加，气体密度小，比容大，可压缩性大，流变性强，离心力小，转换能量性能差是引起泵工况恶化的主要原因。试验表明，当液体中的气量（体积比）达到3%左右时，泵的性能将出现徒降，当入口气体达20%～30%时，泵完全断流。离心泵允许含气量（体积比）极限小于5%。
In the desulfurization system, the slurry transported by the circulating pump often contains a certain amount of gas. In fact, the slurry conveyed by a centrifugal pump is gas solid liquid multiphase flow, and the effect of solid phase on pump performance is continuous and uniform, and the influence of gas relative pump is far more complicated and more difficult to predict than solid phase pump. When the liquid in the pump contains gas, the flow, lift and efficiency of the pump decrease. The greater the gas content, the faster the efficiency decreases. With the increase of gas content, additional noise and vibration of the pump will result in damage to pump shaft, bearing and seal. The accumulation of gas at the inlet of the pump and the back of the blade leads to the increase of flow resistance resistance and even the disconnection, and then the deterioration of the working condition. It must increase the amount of cavitation, the gas density is small, the volume of specific volume is large, the compressibility is large, the rheological property is strong, the centrifugal force is small, and the poor conversion energy performance is the main cause of the pump condition deterioration. The test shows that when the gas (volume ratio) in the liquid reaches about 3%, the performance of the pump will fall, and when the inlet gas reaches 20% to 30%, the pump is completely broken down. The allowable air volume (volume ratio) limit of centrifugal pump is less than 5%.