Ion-exchange membrane double-effect counter-current falling-film evaporation
Thread Content
Recently, a strange problem has arisen in production: our plant uses two-effect counter-current falling-film evaporation with a capacity of 50,000 t/year. Recently, there have been significant fluctuations in the flow rate of the finished alkali output from the first stage. The flow rate returns to normal when the liquid level in the first stage is reduced (originally, at a liquid level of 17%, the alkali flow rate was 17,500 kg/h; now it can only reach 10,000 kg/h. Only when the liquid level in the first stage is increased to 24% can the flow rate reach 17,500 kg/h). We performed the following inspections on the system: replaced the level gauge of the first effect, inspected the heating chamber, the alkali pump of the first effect, and so on. Logically, the alkali flow rate should be under manual control (with a slight negative pressure in the first stage and a concentration of 45%), and it shouldn’t be related to the liquid level in the first stage! (The level of the first effect is only related to the valve that transfers material from the second effect to the first effect)! ! ! ? ? ?
I have indeed encountered such problems before; if there are any solutions, please let me know. I’m eager to learn more! Thank you
At the moment, I can think of only one possibility: when the liquid level is too low, the flow rate of the falling film circulation pump is insufficient (is there any blockage at the pump inlet?) ), the flow rate of the circulation pump is insufficient, which results in an inadequate film-forming flow rate in the falling-film heating chamber; as a consequence, the evaporation capacity decreases and the amount of product output is reduced. Other possible causes have not been considered yet. The building is mainly designed to address this issue; everyone might as well share their insights. I also work in evaporation design, so I’d like to learn from others
The problem still exists; the liquid level is still controlled at 24%, while the actual value is 17%, which means it is outside the specified range. But nothing else seems abnormal! Strange! !