Regarding the flooding phenomenon that occurs when increasing the load on a distillation system
Thread Content
Recently, a bottleneck in terms of difficult dosage addition was identified in the distillation system. 1. When increasing the feed to the pressurized tower via the predicted flow rate, the pressure difference in the pressurized tower gradually increases. If the synthesized crude methanol is added entirely to the system, the pressure difference in the pressure column remains high, ultimately leading to flooding. 2. This issue arises when attempting to resolve the flooding problem in the pressure column; to reduce heat input to the column and maintain its stable operation, it is necessary to decrease the feed rate and heat input. At the same time, the overall temperature and pressure in the pressure column are low, which results in an excessively low temperature at the bottom of the atmospheric pressure column and an excessive level of alcohol in the residual liquid. If the temperature at the bottom of the atmospheric pressure column is maintained while increasing the heat input to the pressurized column, this will lead to flooding in the pressurized column. 3. The designed forecast flow rate was 45 m3/h; after it was increased to 42 m3/h, a high pressure difference began to occur in the pressure tower. When the forecast flow rate was raised to 43 m3/h, significant flooding occurred in the pressure tower. The current issue is that increasing the throughput to improve the prognosis, while ensuring that the pressure column does not experience flooding, allows for an increase in the distillation load. I ask those with expertise to analyze and identify the root cause of this problem. Parameter design data / Actual data Parameter design data / Actual data Feed temperature of pre-tower (°C): 60 / 50.2 Top temperature of atmospheric tower (°C): 64 / 60.2 Top temperature of pre-tower (°C): 65 / 68.6 Bottom temperature of atmospheric tower (°C): 109 / 100 Bottom temperature of pre-tower (°C): 85 / 75.2 Top pressure of atmospheric tower (MPa): 0.03 / 0.016 Top pressure of pre-tower (MPa): 0.05 / 0.015 Bottom pressure of atmospheric tower (MPa): 0.08 / 0.009 Bottom pressure of pre-tower (MPa): 0.08 / 0.019 Reflux temperature of atmospheric tower (°C): 40 / 57.2 Reflux temperature of pre-tower (°C): 40 / 44.5 Temperature of low-pressure steam (°C): 160 / 178.5 Feed temperature of pressurized tower (°C): 120 / 80 Pressure of low-pressure steam (MPa): 0.5 / 0.56 Top temperature of pressurized tower (°C): 122 / 106.5 Bottom temperature of pressurized tower (°C): 134 / 115.8 Top pressure of pressurized tower (MPa): 0.56 / 0.372 Bottom pressure of pressurized tower (MPa): 0.65 / 0.359 Reflux temperature of pressurized tower (°C): 117 / 105.7
Recently, a bottleneck in terms of difficult dosage addition was identified in the distillation system. 1. When increasing the feed to the pressurized tower via the predicted flow rate, the pressure difference in the pressurized tower gradually increases. If the synthesized crude methanol is added entirely to the system, the pressure difference in the pressure column remains high, ultimately leading to flooding. 2. This issue arises when attempting to resolve the flooding problem in the pressure column; to reduce heat input to the column and maintain its stable operation, it is necessary to decrease the feed rate and heat input. At the same time, the overall temperature and pressure in the pressure column are low, which results in an excessively low temperature at the bottom of the atmospheric pressure column and an excessive level of alcohol in the residual liquid. If the temperature at the bottom of the atmospheric pressure column is maintained while increasing the heat input to the pressurized column, this will lead to flooding in the pressurized column. 3. The designed forecast flow rate was 45 m3/h; after it was increased to 42 m3/h, a high pressure difference began to occur in the pressure tower. When the forecast flow rate was raised to 43 m3/h, significant flooding occurred in the pressure tower. The current issue is that increasing the throughput to improve the prognosis, while ensuring that the pressure column does not experience flooding, allows for an increase in the distillation load. I ask those with expertise to analyze and identify the root cause of this problem. Parameters Design Actual Data Parameters Design Actual Data Feed temperature of pre-tower (°C): 60 50.2 Top temperature of atmospheric tower (°C): 64 60.2 Top temperature of pre-tower (°C): 65 68.6 Bottom temperature of atmospheric tower (°C): 109 100 Bottom temperature of pre-tower (°C): 85 75.2 Top pressure of atmospheric tower (MPa): 0.030 0.016 Top pressure of pre-tower (MPa): 0.050 0.015 Bottom pressure of atmospheric tower (MPa): 0.080 0.009 Bottom pressure of pre-tower (MPa): 0.080 0.019 Reflux temperature of atmospheric tower (°C): 40 57.2 Reflux temperature of pre-tower (°C): 40 44.5 Temperature of low-pressure steam (°C): 160 178.5 Feed temperature of pressurized tower (°C): 120 80 Pressure of low-pressure steam (MPa): 0.5 0.56 Top temperature of pressurized tower (°C): 122 106.5 Bottom temperature of pressurized tower (°C): 134 115.8 Top pressure of pressurized tower (MPa): 0.560 0.372 Bottom pressure of pressurized tower (MPa): 0.650 0.359 Reflux temperature of pressurized tower (°C): 117 105.7
You’d better check whether there are already problems with your tower from the start – it might have a certain degree of liquid overflow, and I think in most cases it doesn’t operate properly from the very beginning when load is applied