Since the first set of high-purity nitrogen air separation equipment was developed and produced in 1978 in China's air separation market, the demand of domestic nitrogen market is growing due to economic development . The research and development and manufacturing of nitrogen production equipment have made a leap forward development in recent decades, and the production technology of high-purity nitrogen equipment has become increasingly mature and has fully realized localization.
At present, the demand areas of nitrogen products mainly include oil field nitrogen injection, petrochemical industry, synthetic fiber, synthetic ammonia, glass, steel rolling, high-tech materials and electronic industry. Generally, large-scale high-purity nitrogen equipment is mainly used for nitrogen injection in oil field; large and medium-sized high-purity nitrogen equipment is mainly used in petrochemical industry, float glass, synthetic fiber, synthetic ammonia, steel rolling and other industries; small-scale nitrogen equipment is mainly used in electronic industry.
The basic process forms of high-purity nitrogen are as follows:
1. The expansion process of back flow waste gas is suitable for the occasion of high pressure of nitrogen product. The process effectively uses the exhaust gas with pressure, which is divided into two processes: full expansion and partial expansion. The liquid produced by full expansion is larger than that produced by partial expansion, but the investment of expander will be increased.
2. The process of positive flow air expander is suitable for the occasion requiring low pressure products of nitrogen. The flow form is that the expansion air is directly expanded to close to the atmospheric pressure after being pressurized at the booster expander for direct venting. When the unit scale is large, a separate supercharger is set for boosting the expansion air to improve the product output.
Pressure swing adsorption for nitrogen production is suitable for the occasion of low nitrogen purity requirements. In general, PSA can not produce liquid. When liquid products are needed, the method of external liquefaction device shall be adopted.
3. Compared with the above processes, PSA can reduce energy consumption, but the investment is large.
At present, the most widely used processes are the back flow exhaust gas expansion process and the positive flow air expansion process, in which the positive flow air expansion is suitable for the users with large liquid consumption, and the back flow exhaust gas expansion process has the advantage of low energy consumption and the most widely used.
