A new heating system for the air pre-purification of air separation units

Abstract

A new heating system is disclosed to reduce the regeneration heating electric consumption for air pre-purification of air separation units. The new heating system is of great energy-saving significance, as air separation units are energy-intensive installations that account for a considerable proportion (around 4.97 %) of China's total national electricity consumption. Unlike the traditional electric heater, the new heating system integrates components such as a compressor, a heat exchanger, and an expander to meet the heat requirement of the pre-purification unit, while also providing cooling capacity to reduce the refrigeration load of the pre-cooling system of an air separation unit, thereby realizing the efficient comprehensive utilization of electric energy. Furthermore, a regenerator is employed to enable the continuous operation and downsizing of the system. Mathematical models were established for each process in the new heating system, and then the simulation and calculation were carried out based on the field data of an industrial-scale air separation unit. Inlet and outlet parameters and power of the compressor, expander, and heat exchanger were obtained. The temperature and pressure bed profiles of the regenerator and the temperature history curves of the cold and hot ends of the regenerator were obtained. Then, the energy-saving effect of the new heating system relative to the traditional electric heater was obtained. In addition, an economic evaluation of the new heating system was conducted based on its energy-saving effect. The conclusions drawn are as follows: compared with a traditional electric heater, the new heating system can save about 55.5 % of electric energy, and the payback period of the new heating system retrofitted from a traditional electric heater is about 2.3 years.