Purification Technology Edition: Daily Question [2018-1-22]

The main faults of air separation units during normal operation include unstable operating conditions, potential safety hazards in the equipment, and leaks inside the cryogenic tank, among others ； Generally, failures in air separation units occur during startup and shutdown processes, such as the collapse of perlite sand

The main faults of air separation units during normal operation include unstable operating conditions, potential safety hazards in the equipment, and leaks inside the cryogenic tank, among others ； Generally, failures in air separation units occur during startup and shutdown processes, such as the collapse of perlite sand

What to do in case of an air separation unit failure? Answer: 1. Immediately close the main clean gas outlet valve on site. 2. Manually close the large rough gas valve. 3. Stop spraying methanol. 4. The main washing system operates under pressure retention. 5. Decide whether to continue with the shutdown based on the duration of the air separation unit failure.

1. Immediately close the main outlet gas valve on site. 2. Manually close the large rough gas valve. 3. Stop spraying methanol. 4. The main washing system operates under pressure retention. 5. Decide whether to continue with the shutdown based on the duration of the air separation unit failure.

Common major faults and solutions: 1. Increase in pressure difference of the main heat exchanger. To prevent an increase in the pressure difference of the main heat exchanger, it is essential to properly maintain the molecular sieve purification system to adsorb moisture, CO2, and hydrocarbons. When changing the load on the device, it is particularly important to note that neither the increase nor the decrease in the amount of process gas should be done too quickly; such changes must be made gradually to prevent certain impurities from not being absorbed by the molecular sieve and thus ending up in the main heat exchanger, which could lead to an increase in pressure difference and affect the efficiency of heat exchange. 2. Fluctuations in the expander speed. The speed of the expander in operation within the air separation unit varies between 8200 and 8700 r/min, with fluctuations of up to 500 r/min; under normal operating conditions, these speed fluctuations are within 30 r/min. This results in instability in the liquid level of the main cooler in the air separation unit, requiring repeated manual adjustments. Primarily, the valve positioner is a wear-prone component, so sufficient spare parts should be ensured. 3. Excessive hydrocarbon content at the inlet: An excessive hydrocarbon content in the air separation units within chemical plants is a fairly common phenomenon. The air intake of the air separation unit should be located as far away as possible from the production units and workshops where volatile organic compounds are produced, and placed upwind of such workshops to ensure the quality of the feed gas. 4. The gas temperature between the stages of the feedstock compressor has increased. The feedstock compressor features three stages of compression and two stages of cooling; all other components are operating normally. The most likely cause is poor heat exchange efficiency in the first-stage cooler. Given the gradual rise in temperature, it is probable that there is an obstruction on the side of the heat exchanger where the circulating water flows. Enterprises should strengthen the management of the quality of circulating water. To ensure the safety of critical equipment, workshops should install switchable cleaning filters at the entrance to the relevant areas or on the water lines of such equipment, so as to prevent the equipment from shutting down due to clogged coolers

Answer: 1. Immediately close the main outlet gas valve on site. 2. Manually close the large rough gas valve. 3. Stop spraying methanol. 4. The main washing system operates under pressure retention. 5. Decide whether to continue with the shutdown based on the duration of the air separation unit failure.

1. Immediately close the main outlet gas valve on site. 2. Manually close the large rough gas valve. 3. Stop spraying methanol. 4. The main washing system operates under pressure retention. 5. Decide whether to continue with the shutdown based on the duration of the air separation unit failure.

The handling of various types of accidents varies; in cases of DCS failures or power outages, the air compressors must be shut down

1. Immediately close the main outlet gas valve on site. 2. Manually close the large rough gas valve. 3. Stop spraying methanol. 4. The main washing system operates under pressure retention. 5. Decide whether to continue with the shutdown based on the duration of the air separation unit failure