In the air separation plant, the main heat exchanger is the key equipment to ensure the performance of the whole set of equipment. The function of the main heat exchanger in the molecular sieve pre purification process air separation equipment is to ensure the temperature difference at the hot end to be kept at the design value by recovering the cold quantity of the backflow gas, provide sufficient expander gas to expander, make up for the cold quantity loss of the equipment, and provide the raw gas under the design condition for the lower tower.
A brief introduction of several factors that affect the temperature difference at the hot end of the main heat exchanger;
1.Performance of molecular sieve adsorber:
Air short circuit caused by external factors such as poor adsorption performance which may exists when the molecular sieve adsorber is not filled with enough molecular sieve, the bed is unevenand the incomplete regeneration of molecular sieve, molecular sieve leakage due to manufacturing reasons and other factors, the temperature difference and resistance at the hot end of the main heat exchanger will rise.
2.Expander efficiency:
The pressure, temperature, flow and other parameters of the expansion air out of the main heat exchanger are all the given values during the design of the main heat exchanger. If the state of the expansion air out of the main heat exchanger is normal, and the temperature after the expansion is higher than the design value, the temperature difference at the hot end of the main heat exchanger will be larger and larger if increase the expansion amount to maintain the operation of the air separation equipment, resulting in the damage of the operation condition of the air separation and the failure of normal operation. Maintenance of the expander is the most common method to solve the large temperature difference at the hot end of the main heat exchanger.
3.Running cooling loss:
Running cooling loss is a process parameter estimated by experience. Its actual value is generated according to the size of air separation unit, the performance of equipment itself and the external environment. The difference between the set value of running cooling loss and the actual value directly affects the temperature difference at the hot end of the main heat exchanger.Usually, when the air separation equipment is abnormal, people often start from the main heat exchanger to find out the cause of the abnormal, and accurately analyze the external factors that affect the performance of the main heat exchanger, which is the best way to solve the abnormal situation of air separation equipment.
