Practical Exercise on Purification Technology Version [021]

The main reason for the sharp rise in the catalyst bed temperature is: ① An increase in the oxygen content in the raw gas fed into the catalyst bed.   ② The load increases suddenly, and regulation is not timely, such as a sudden rise in carbon monoxide levels in gas.    ③ Due to improper operation, the temperature regulation bypass line was reduced in size or closed.   A sudden rise in the temperature of the catalyst bed will reduce the catalyst’s activity, cause reverse sulfidation of the conversion catalyst, and even damage the catalyst. Therefore, it is necessary to identify the cause immediately and take prompt action: ① Appropriately open the temperature control bypass valve. ② Adjust the inlet temperature of the converter. ③ If oxygen is present in the gas, production should be reduced; if necessary, an emergency shutdown should be carried out, while notifying the upstream units to identify the cause and take corrective action

The main reason for the sharp rise in the catalyst bed temperature is: (1) the high oxygen content in the water gas fed into the shift converter. (2) A sudden increase in carbon monoxide in water gas, with untimely adjustment. (3) Improper operation: the temperature adjustment bypass line is reduced in size or closed

① The oxygen content in the raw gas entering the catalyst bed increases. ② The load increases suddenly, and regulation is not timely, such as a sudden rise in carbon monoxide levels in gas. ③ Due to improper operation, the temperature regulation bypass line was reduced in size or closed.

1. A sharp increase in the amount of gas supplied, 2. A sudden decrease in the volume of gas circulating, 3. A sudden improvement in the composition of the gas entering the tower, 4. Improper operation

Reasons for a sudden increase in the catalyst bed temperature: 1. Sudden increase in the amount of make-up gas. An increase in the amount of make-up gas leads to an increase in the heat generated during ammonia synthesis; if this cannot be adjusted in time, it results in a sudden rise in the catalyst bed temperature. This phenomenon often occurs in production due to too rapid addition of the material and failure to communicate in a timely manner when adding it. 2. Sudden decrease in the circulation gas volume: A reduction in the circulation gas volume increases the contact time between the gas and the catalyst, bringing the ammonia synthesis reaction closer to equilibrium. As a result, the heat generated by the reaction increases, causing a sudden rise in the temperature of the catalyst bed. In production, a sudden decrease in the volume of circulating gas is often caused by failures in the circulation machine. 3. The composition of the gas entering the tower improves rapidly; factors such as the hydrogen-to-nitrogen ratio shifting from being too high or too low to an appropriate level, a decrease in the ammonia content of the inlet gas, and a reduction in inert gases are all beneficial to the ammonia synthesis reaction, leading to an increase in the temperature of the catalyst layer and a decrease in system pressure. 4. Improper operation or untimely adjustment – If the opening degree of the cold auxiliary valve is too small, if the opening degree of the circulation pump circuit valve or system bypass valve is too large, or if the power of the electric furnace is increased too quickly, all of these can cause a sudden rise in the temperature of the catalyst bed. 5. Low level of waste boiler liquid: An excessively low level of waste boiler liquid, to the point of a \"dry boiler\" condition, can cause increases in the temperature of the secondary outlet, the waste boiler outlet, and the circulation heater. This in turn leads to an increase in the temperature of the heat exchanger below the synthesis tower; as a result, the incoming gas absorbs a large amount of heat in the lower heater, causing its temperature to rise sharply. At this point, if the secondary line of the tower is continuously increased in size, the gas flow rate in the main line will decrease gradually, the cooling air supply to the waste heat exchanger will reduce, the liquid level will continue to drop, and the temperature of the catalyst bed will keep rising. It plunges production into a vicious cycle.

①The oxygen content in semi-water gas increases as it enters the catalyst bed. ②The load increases suddenly, and adjustments are not made in a timely manner; for example, the increase in dosage is too rapid, or the CO content in the semi-water gas rises suddenly without corresponding adjustments to the amount of steam added. ③The steam pressure drops or the gas system is overpressured, resulting in a reduced amount of steam being supplied or no steam at all being supplied. ④There is a fault with the inter-stage water spraying in the medium-pressure furnace; the water flow is reduced or no water is sprayed. ⑤The hot water pump is evacuated, resulting in a reduction in the amount of steam recovered from the semi-water gas at the outlet of the saturation tower.

The main reason for the sharp rise in the catalyst bed temperature is: ① An increase in the oxygen content in the raw gas fed into the catalyst bed. ② The load increases suddenly, and regulation is not timely, such as a sudden rise in carbon monoxide levels in gas. ③ Due to improper operation, the temperature regulation bypass line was reduced in size or closed.

1. Sudden increase in make-up gas volume: An increase in the make-up gas volume leads to an increase in the heat generated during ammonia synthesis; if this is not adjusted in a timely manner, it results in a sudden rise in the temperature of the catalyst bed. This phenomenon often occurs in production due to too rapid addition of the material and failure to communicate in a timely manner when adding it. 2. Sudden decrease in the circulation gas volume: A reduction in the circulation gas volume increases the contact time between the gas and the catalyst, bringing the ammonia synthesis reaction closer to equilibrium. As a result, the heat generated by the reaction increases, causing a sudden rise in the temperature of the catalyst bed. In production, sudden decreases in the volume of circulating gas often occur due to failures in the circulation machines. 3. An improvement in the composition of the gas entering the tower – such as a change in the hydrogen-to-nitrogen ratio from being too high or too low to an appropriate level, a decrease in the ammonia content in the gas entering the tower, and a reduction in inert gases – all contribute to the ammonia synthesis reaction, leading to an increase in the temperature of the catalyst layer and a decrease in system pressure. 4. Improper operation or untimely adjustment – If the opening degree of the cold auxiliary valve is too small, if the opening degree of the circulation pump circuit valve or the system bypass valve is too large, or if the power of the electric furnace is increased too quickly, all of these can cause a sudden rise in the temperature of the catalyst bed. An excessively low level of liquid in the waste pot, to the point of a \"dry pot\" condition, causes temperatures to rise in the secondary outlet, the waste pot outlet, and the circulation heater. This further leads to an increase in the temperature of the heat exchanger located below the synthesis tower; as a result, the incoming gas absorbs a large amount of heat in the lower heater, causing its temperature to rise sharply. At this point, if the flow rate in the secondary line of the large tower is increased, the gas flow rate in the main line will decrease gradually, the cooling air supply to the waste boiler will reduce, the liquid level will continue to drop, and the temperature of the catalyst bed will keep rising. It plunges production into a vicious cycle.

1. The oxygen content in the raw gas entering the catalyst bed increases； 2. A sudden sharp increase in load without timely adjustment, such as a sudden rise in carbon monoxide levels in gas ； 3. Improper operation: the temperature adjustment bypass line is reduced or closed.

1. Oxygen is present in the gas; 2. The load increases suddenly, and adjustments are not made in time, such as an excessive increase in the amount of gas supplied or a sudden rise in carbon monoxide levels in the gas. 3. The load drops sharply, the space velocity decreases, and the heat is not removed in time