Practical Exercise on Purification Technology Version [052]

Consumption: (1) Nitrogen is stripped and vented out of the system. (2) Acidic gases are vented out of the system. (3) The water at the bottom of the methanol-water separation tower is drained out of the system. (4) Carried out of the system with the process gas. Measures: (1) Increase the ammonia supply to the ammonia cooler. (2) Lower the methanol flash temperature. (3) Lower the temperature of acidic gases.

1. Acid gas consumption – this amount is relatively high. The main ways to reduce such consumption are to lower the temperature of the acid gas leaving the system and to reduce the volume of acid gas exiting the system. There is no need to elaborate on reducing the temperature of acidic gas leaving the system; to decrease the amount of acidic gas exiting the system, it is important to pay attention to the system temperature – it must not be too low, as this will lead to a significant increase in the amount of acidic gas. 2. There are no specific methods to control the methanol carried in the system’s exhaust gases, nor the methanol contained in the carbon dioxide exiting the system. Pay attention to the operating condition of the overhead demister in the system and the pressure of the stripping tower. 3. In the initial washing stage, methanol is removed from the hydrogen gas in the system; some companies do not include this amount of methanol in their methanol consumption figures, as there are methods available for its recovery. 4. Volatilization from the methanol storage tank. Generally, methanol storage tanks are open; on one hand, it is necessary to control the temperature of the tank, and on the other hand, it is necessary to control the amount of nitrogen in the tank. Additionally, the contaminated methanol in the system should be returned to it as soon as possible for reuse, to prevent increased volatilization due to long-term storage.

Consumption: (1) Nitrogen is stripped and vented out of the system. (2) Acidic gases are vented out of the system. (3) The water at the bottom of the methanol-water separation tower is drained out of the system. (4) Carried out of the system with the process gas. Measures: (1) Increase the ammonia supply to the ammonia cooler. 2) Lower the methanol flash temperature. (3) Lower the temperature of acidic gases.

Consumption: (1) Nitrogen is stripped and vented out of the system. (2) Acidic gases are vented out of the system. (3) The water at the bottom of the methanol-water separation tower is drained out of the system. (4) Carried out of the system with the process gas. Measures: (1) Increase the ammonia supply to the ammonia cooler. (2) Lower the methanol flash temperature. (3) Lower the temperature of acidic gases.

Consumption: 1. Nitrogen is stripped and vented out of the system. 2. Acidic gases are vented out of the system. 3. The drainage at the bottom of the methanol-water separation tower is led out of the system. 4. Carry out of the system with the process gas. Measures: 1. Increase the ammonia supply to the ammonia cooler. 2. Reduce the methanol flash temperature. 3. Reduce the temperature of acidic gases.

Consumption: (1) Nitrogen is stripped and vented out of the system. (2) Acidic gases are vented out of the system. (3) The water at the bottom of the methanol-water separation tower is drained out of the system. (4) Carried out of the system with the process gas. Measures: (1) Increase the ammonia supply to the ammonia cooler. (2) Lower the methanol flash temperature. (3) Lower the temperature of acidic gases. ...

Consumption: (1) Nitrogen is stripped and vented out of the system. (2) Acidic gases are vented out of the system. (3) The water at the bottom of the methanol-water separation tower is drained out of the system. (4) Carried out of the system with the process gas. Measures: (1) Increase the ammonia supply to the ammonia cooler. (2) Lower the methanol flash temperature. (3) Reduce the temperature of acidic gases

Consumption: (1) Nitrogen is stripped and vented out of the system. (2) Acidic gases are vented out of the system. (3) The water at the bottom of the methanol-water separation tower is drained out of the system. (4) Carried out of the system with the process gas. Measures: (1) Increase the ammonia supply to the ammonia cooler. (2) Lower the methanol flash temperature. (3) Lower the temperature of acidic gases.

(1) The nitrogen is stripped and vented out of the system. (2) Acidic gases are vented out of the system. (3) The water at the bottom of the methanol-water separation tower is drained out of the system. (4) Carried out of the system with the process gas.

Methanol loss: purified gas, carbon dioxide, acidic gases, exhaust gas, wastewater. Among them, there is a relatively higher amount of carbon dioxide products and exhaust emissions. 1. Increase the load on the chiller to its maximum level, in order to reduce the temperature of the circulating methanol as much as possible, thereby minimizing the amount of methanol vapor carried away by the purified gas, CO2 gas, and exhaust gases. 2. Strictly control the methanol content in the wastewater at the bottom of the methanol-water separation tower to remain within the specified process parameters. 3. Ensure that the mesh demisting devices in the methanol washing tower, CO2 desorption tower, and hydrogen sulfide concentration tower are in good condition and provide effective demisting performance. 4. Implement enhanced filtration of methanol in the system to keep the pressure differences across various towers within the specified limits, thereby preventing incidents of liquids being carried along with the gases. 5. The liquid level in the acidic gas separator should not be too high, to avoid the situation where liquids are carried along with the acidic gases.