Methods for reducing the nitrate content in magnesium nitrate during the production of concentrated nitric acid using the magnesium nitrate method
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In the production of concentrated nitric acid using the magnesium nitrate method, the dilute magnesium nitrate coming out of the bottom of the concentration tower contains some nitric acid or nitrogen oxides, resulting in a \"nitrogen-containing\" composition. The higher the level of nitrogen content, the greater the corrosivity. Let’s first discuss ways to reduce this nitrogen content
High nitrate content in dilute magnesium solution: Causes and solutions ① Low amount of steam used for heating – increase the steam supply to the heater. ② Concentration of dilute magnesium nitrate is too high or too low – reduce or increase the amount of concentrated magnesium nitrate. ③ Low negative pressure in the tower – increase the negative pressure appropriately. ④ Liquid level in the heater is too high or too low – contact the pump operator to adjust it to the normal range. ⑤ The magnesium solution contains many impurities, resulting in poor dehydration performance – regenerate or replace it. ⑥ Many packing materials in the tower are damaged； Replace the packing ； The dispersing disk in the dispersing disk tower does not disperse evenly. ⑦ The liquid phase temperature in the heater is low; increase the steam supply, slightly open the bypass valve of the steam trap, and discharge inert substances. ⑧ The steam trap in the heater is blocked, preventing condensate from being discharged, which leads to pressure buildup. Cleaning, discharge ⑨ High amount of acid returning – reduce the amount of reflux ⑩ High tower load – decrease it appropriately ⑾ Fouling on the heater tubes, insufficient heat transfer area, steam taking a shortcut – shut down the system for maintenance
The explanation is quite comprehensive, but one more point worth noting is the leakage in the concentrated nitric acid condenser. To maintain the concentration of the concentrated acid, it is necessary to increase the ratio of ingredients used or enhance the reflux process; therefore, any leakage in the concentrated nitric acid condenser requires immediate shutdown for repair, otherwise the consequences will be severe.