Study On The Changing Laws Of Technical Parameters For Multi-Machine Synchronous Running During The Process Of Air Seperation

Air separation is important productive process in industry to produce high-purity oxygen, nitrogen, argon and other industrial gases. The air separation plant is key equipment of many industries, such as iron&steel industries, chemical industries and so on. With the rapid economic development, the design and manufacturing of air separation equipment is tended to the direction of large-scale, low-energy consumption gradually. However, the air separation industries in our country have to depend on the products of foreign companies in the key equipment, such as large compressors, expanders, etc.It’s frequent to use only one set of thermal performance parameters (the inlet pressure and temperature, and the outlet pressure) in the calculations of design for the compressor or expander used in the air separation plant. This differs from the conditions of the practical work. In fact, the environment in which the air separation plant works is always variable. Some of the changes are regular changes with Periodicity or proximate Periodicity. The change of the environmental parameters will lead to the variation of the load of the working parts for the compressor or other critical equipment inevitably. Therefore, it is necessary to investigate the changing rule of multi-units synchronous running state parameters to provide the reliable load data for the design of the critical parts in the system when the air separation plant works in changing environment. This papetr explores the change laws of the thermal performance parameters for the air compressor, booster and booster braked expander when they work in changing environment. The main works and contributions are decribed as follows:(1) Taking one of40000m3/h air separation plants as an exsample, the paper analyzes the air separation process and esatablishes the mathematic model of the plant, in which the equation of state for gases is amended.(2) A software simulation model of the air separation whole process is built by uising Aspen HYSYS and numerical analysis is conducted. Then, the paper discusseses the influence of the environmental parameter and inter-stage cooling water flow on the outlet thermodynamic parameters of the compressor, as well as the effect of the changes of the low pressure air, high pressure air and the expanded air on the whole process. The results show that the changes of the environmental parameters and inter-stage cooling water flow make a profound impact on the outlet thermodynamic parameters of the compressor. This impaction can change the parameters of low pressure air, high pressure air and the expanded air.(3) A dynamic model of multi-unit synchronous running system is established, which is composed of an air compressor, a booster and a booster braked expander. Analysis is conducted to explore the change laws of the parameters of every stage in the air compressor, the booster, the booster/expander of the booster braked expander when the pressure, temperature or humidity in the inlet of the air compressor change. The results show that the compression ratio of the compressor varies with the inlet parameters, which results in the change of tbe thermodynamic parameters for all the units after the air compressor.