With the development of social economy, the air separation plant is in the trend of large-scale development. Air separation plant, as a large energy consumption user, is affected by domestic environmental protection and resource problems. It has great significance on the development of enterprises and the improvement of economic benefits to select a reasonable compressor driving mode.
At present, many compressors of large-scale air separation plant are driven by steam turbine. Industrial steam turbine has the characteristics of axisymmetric high-speed rotation, so the operation is stable, the wear is small, and the continuous operation time is long. However, the installation and commissioning of steam turbine are relatively complex, the requirements for heating and production system are high, the start-up and shutdown process is complex, the cycle is long, and the one-time investment is large.
In the field of air separation, the starting modes of motor mainly include direct starting, reactor starting, autotransformer starting and LCI soft starting. In large-scale air separation plant, the motor starting mode of compressor unit is usually autotransformer starting and LCI soft starting. Compared with LCI, the impact of autotransformer startup on power grid and motor is greater, but the system structure is simple and the cost is relatively low. The impact of LCI soft start on power grid is very small, at the same time, it can reduce the impact of instantaneous large current on the motor and fully protect the motor. But the start-up is more complex and the cost is relatively high.
According to the current level of steam and electricity price, from the perspective of energy consumption, turbine drive occupies a certain advantage. However, the level of energy consumption ultimately depends on the price level of steam and electricity. If the price of electricity drops further or the price of steam rises, the energy consumption of motor driven will be lower than that of turbine driven.
The investment of turbine driven compressor unit for large air separation plant is significantly higher than that of motor driven compressor unit, but the energy consumption cost of turbine driven compressor unit is relatively low at the price level of conventional steam and electricity and considering the long-term operation of the plant. Once the price of steam and electricity exceeds the balance point of energy consumption, motor drive will be more competitive for large air separation plant.