Questions regarding the desorption and relief system of the CO2 stripping urea plant
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What impact does a high or low ratio of the process condensate from the ammonia tank to the low-pressure steam introduced at the bottom of the second desorption tower have on the desorption and hydrolysis process? What consequences will this have for the entire desorption system?
If it is too high, steam is wasted and the water content in the system increases before it returns; if it is too low, ammonia and carbon dioxide are not fully separated in the stripping tower and end up in the hydrolysis tower, resulting in a high ammonia content in the waste liquid from separation, which makes it impossible to recycle. Therefore, the vapor-liquid ratio cannot be too high nor too low – it needs to be adjusted based on the actual conditions
When the concentration in the ammonia tank is high, increasing the vapor-liquid ratio appropriately facilitates the separation of ammonia, sulfur dioxide, etc.; meanwhile, the vapor-liquid ratio also needs to be adjusted accordingly as the load changes. The specific adjustment of this vapor-liquid ratio should be based on the final conductivity value and the water content in the purified gas phase; that is, while avoiding environmental incidents, it is also necessary to take into account the amount of water returning to the high-pressure system.