Cryogenic Air Separation for Nitrogen Production
Cryogenic air separation (CES) is a traditional nitrogen production method with a history of several decades. It uses air as feedstock, which is compressed, purified, and then liquefied into liquid air through heat exchange. Liquid air is primarily a mixture of liquid oxygen and liquid nitrogen. Taking advantage of the different boiling points of liquid oxygen and liquid nitrogen (at 1 atmosphere, the former boils at -183°C, and the latter at -196°C), nitrogen is obtained by separating them through distillation.
Molecular Sieve Air Separation for Nitrogen Production
Using air as feedstock and carbon molecular sieves as adsorbents, this method utilizes the pressure swing adsorption (PSA) principle to selectively adsorb oxygen and nitrogen, thus separating them. This method is a relatively new nitrogen production technology that rapidly developed in the 1970s. Compared to traditional nitrogen generation methods, it boasts advantages such as a simple process flow, high automation, rapid gas production (15-30 minutes), low energy consumption, adjustable product purity within a wide range to meet user needs, convenient operation and maintenance, lower operating costs, and strong adaptability. Therefore, it is highly competitive among nitrogen generation equipment below 1000 Nm³/h and is increasingly welcomed by medium and small-sized nitrogen users. PSA nitrogen generation has become the preferred method for medium and small-sized nitrogen users.
Membrane Air Separation Nitrogen Generation
Using air as raw material, under certain pressure conditions, oxygen and nitrogen are separated by utilizing their different permeation rates within a membrane. Compared to other nitrogen generation equipment, it has advantages such as simpler structure, smaller size, no switching valves, less maintenance, faster gas production (≤3 minutes), and convenient capacity expansion. It is particularly suitable for medium and small-sized nitrogen users with nitrogen purity ≤98%, offering the best performance-price ratio. However, for nitrogen purity above 98%, its price is more than 15% higher than that of a PSA nitrogen generator of the same specifications.
VRM (Vacuum-Retaining Unit) Nitrogen Generation
This system replaces the traditional air compressor compression process with a vacuum pump. The system draws gas from a sealed chamber as feed gas, which is then fed into an integrated unit for oxygen and nitrogen separation. The oxygen is discharged, and the nitrogen is returned to the sealed chamber via a circulation system, repeating the cycle. The equipment operates at pressures below 0.1 MPa, classifying it as atmospheric pressure equipment. This eliminates the need for pressure vessels and special pressure equipment control and registration. The process design, which replaces pressure vessels, results in a simpler and more streamlined system configuration, ensuring both safety and economic efficiency during operation.