Determination of H\C and N\C in urea

Using the high methanol cold liquid temperature to determine N/C and using the gas withdrawn liquid to determine H/C are methods based on operational procedures; additionally, gas withdrawal along with syngas can be utilized to determine N/C. H/C can be combined with the high-methane off-gas to determine the synthesized liquid.

Could the master please analyze it in detail based on the levels of balance temperature for H\C and N\C in the system? What does a high value indicate? What does a low value indicate?

If the high-pressure remains constant, an increase in the temperature of the high-temperature refrigerant outlet fluid and an increase in the liquid level in the gas extraction line indicate that H\C is high. Ammonia can be added to N\C; a decrease in high-pressure pressure indicates that N\C is low, while an increase indicates that N\C is high.

This issue is generally addressed by analyzing it on a case-by-case basis. 1. Phenomenon of N/C imbalance in the high-pressure system: ① When N/C is high, both the top and bottom temperatures of the synthesis tower decrease, the carbon dioxide conversion rate increases, the high-pressure system experiences overpressure, and the steam consumption of the system rises； The overpressure temperature at medium and low pressures cannot be increased; the amount of free NH3 in the medium-pressure absorption tower C101 increases. The high-pressure ammonium methoxide pump P102 vaporizes, and in severe cases, the urea solution pump P106 fails to function properly, resulting in a disruption in the evaporation process. The evaporation temperature and vacuum level cannot be increased, forcing the system to operate in a cyclic mode. ②When N/C is low, the temperatures at the top and bottom of the synthesis tower increase, the conversion rate of carbon dioxide decreases, the pressure in the high-pressure system is low, the temperature TI1015 at the top of the synthesis tower exceeds the limit, and the steam generation volume in E105 increases. The pressure in the medium and low-pressure systems is low, and the temperature of the trays in the medium-pressure absorption tower C101 is high. When N/C is too low, the temperature of the synthesis tower drops, the temperature difference between the top and bottom decreases, and the high-pressure system experiences overpressure. E105 has a low steam generation rate, and the low-pressure ammonium methoxide condenser E108 is prone to crystallization-induced blockages. C101 is severely overheated, and the ammonia cooler E109 is prone to crystalline blockages. If not addressed promptly, methylammonium will enter the ammonia receiving tank V105, causing the high-pressure ammonia pump P101 to trip. 2. Phenomena of H/C imbalance in the high-pressure system: ① Low H/C: The liquid phase temperature TI1019 in V-101 and the temperature of the ammonia feed line entering the tower, TI1014, decrease ； The temperature at the bottom of the urea synthesis tower R101 decreases, the temperature difference between the top and bottom increases, the conversion rate of carbon dioxide rises, and the system pressure goes up. As a result, the opening degree of the pressure control valve PV1021A in the high-pressure system increases automatically; the amount of vapor generated in the high-pressure ammonium carbamate condenser E105 decreases, the stripping efficiency improves, and the steam consumption of the system is reduced. ②High H/C: The liquid phase temperature TI1019 of V-101 and the temperature of the ammonia feed line entering the tower, TI1014, increase. The temperature at the bottom of reactor R101 increases, the temperature difference between the top and bottom decreases, and the carbon dioxide conversion rate drops. As the system pressure drops, the valve in PV1021A closes automatically. The steam generation rate of the high-pressure ammonium methoxide condenser E-105 increases, resulting in an increased steam consumption by the system. The decomposition load on the medium and low-pressure systems rises, making it difficult to maintain the evaporation system. When H/C is significantly too high, the temperature difference in the synthesis tower is very small, or even non-existent, resulting in a very low conversion rate of carbon dioxide. The medium-pressure absorption tower C101 experienced severe over-temperature, as well as overpressure in both the medium and low pressure sections, forcing the evaporation process to switch to circulation mode. I hope this helps you.

This issue is generally addressed by analyzing it on a case-by-case basis. 1. Phenomenon of N/C imbalance in the high-pressure system: ① When N/C is high, both the top and bottom temperatures of the synthesis tower decrease, the carbon dioxide conversion rate increases, the high-pressure system experiences overpressure, and the steam consumption of the system rises； The overpressure temperature at medium and low pressures cannot be increased; the amount of free NH3 in the medium-pressure absorption tower C101 increases. The high-pressure ammonium methoxide pump P102 vaporizes, and in severe cases, the urea solution pump P106 fails to function properly, resulting in a disruption in the evaporation process. The evaporation temperature and vacuum level cannot be increased, forcing the system to operate in a cyclic mode. ②When N/C is low, the temperatures at the top and bottom of the synthesis tower increase, the conversion rate of carbon dioxide decreases, the pressure in the high-pressure system is low, the temperature TI1015 at the top of the synthesis tower exceeds the limit, and the steam generation volume in E105 increases. The pressure in the medium and low-pressure systems is low, and the temperature of the trays in the medium-pressure absorption tower C101 is high. When N/C is too low, the temperature of the synthesis tower drops, the temperature difference between the top and bottom decreases, and the high-pressure system experiences overpressure. E105 has a low steam generation rate, and the low-pressure ammonium methoxide condenser E108 is prone to crystallization-induced blockages. C101 is severely overheated, and the ammonia cooler E109 is prone to crystalline blockages. If not addressed promptly, methylammonium will enter the ammonia receiving tank V105, causing the high-pressure ammonia pump P101 to trip. 2. Phenomena of H/C imbalance in the high-pressure system: ① Low H/C: The liquid phase temperature TI1019 in V-101 and the temperature of the ammonia feed line entering the tower, TI1014, decrease ； The temperature at the bottom of the urea synthesis tower R101 decreases, the temperature difference between the top and bottom increases, the conversion rate of carbon dioxide rises, and the system pressure goes up. As a result, the opening degree of the pressure control valve PV1021A in the high-pressure system increases automatically; the amount of vapor generated in the high-pressure ammonium carbamate condenser E105 decreases, the stripping efficiency improves, and the steam consumption of the system is reduced. ②High H/C: The liquid phase temperature TI1019 of V-101 and the temperature of the ammonia feed line entering the tower, TI1014, increase. The temperature at the bottom of reactor R101 increases, the temperature difference between the top and bottom decreases, and the carbon dioxide conversion rate drops. As the system pressure drops, the valve in PV1021A closes automatically. The steam generation rate of the high-pressure ammonium methoxide condenser E-105 increases, resulting in an increased steam consumption by the system. The decomposition load on the medium and low-pressure systems rises, making it difficult to maintain the evaporation system. When H/C is significantly too high, the temperature difference in the synthesis tower is very small, or even non-existent, resulting in a very low conversion rate of carbon dioxide. The medium-pressure absorption tower C101 experienced severe over-temperature, as well as overpressure in both the medium and low pressure sections, forcing the evaporation process to switch to circulation mode. I hope this helps you.