PSA nitrogen generator with gas chromatograph for food packaging nitrogen filling

PSA nitrogen generator with gas chromatograph for food packaging nitrogen filling

Introduction to Principles

Pressure swing adsorption gas separation technology is an important branch of non cryogenic gas separation technology, which is the result of people's long-term efforts to find simpler air separation methods than cryogenic methods. In the 1970s, the West German mining company Essen successfully developed carbon molecular sieves, paving the way for the industrialization of PSA air separation nitrogen production. Over the past thirty years, this technology has developed rapidly and become increasingly mature, becoming a strong competitor in the field of cryogenic air separation for small and medium-sized nitrogen production.

Pressure swing adsorption nitrogen production is a process that uses air as raw material and carbon molecular sieves as adsorbents. By utilizing the selective adsorption properties of carbon molecular sieves for oxygen and nitrogen in the air, the pressure swing adsorption principle (pressure adsorption, pressure reduction desorption, and regeneration of molecular sieves) is applied to separate oxygen and nitrogen at room temperature to produce nitrogen gas.

Compared with cryogenic air separation nitrogen production, pressure swing adsorption nitrogen production has significant characteristics: adsorption separation is carried out at room temperature, the process is simple, the equipment is compact, the footprint is small, the start and stop are convenient, the start-up is fast, the gas production is fast (generally around 30 minutes), the energy consumption is low, the operating cost is low, the degree of automation is high, the operation and maintenance are convenient, the dismantling is easy, no special foundation is required, the nitrogen purity of the product can be adjusted within a range, and the nitrogen production is ≤ 2000Nm/h. But so far, except for the PSA nitrogen production technology used by American air supply companies, which can produce high-purity nitrogen with a purity of ≥ 99.999% without the need for secondary purification (imported at a high price), domestic and foreign peers generally only use PSA nitrogen production technology to produce pure nitrogen with a purity of 99.9% (i.e. O2 ≤ 0.1%), and some companies can produce 99.99% pure nitrogen (O2 ≤ 0.01%). Higher purity is possible from PSA nitrogen production technology, but the production cost is too high and users find it difficult to accept. Therefore, using non low-temperature nitrogen production technology to produce high-purity nitrogen also requires a secondary purification device.

PSA nitrogen generator with gas chromatograph for food packaging nitrogen filling

Three nitrogen production methods and their characteristics

The modern industrial nitrogen production method uses air as raw material to separate oxygen and nitrogen. There are currently three main methods, namely cryogenic air separation, molecular sieve air separation (PSA), and membrane air separation.

1. Deep cold air separation for nitrogen production

Cryogenic air separation for nitrogen production is a traditional nitrogen production method with a history of nearly 90 years. It uses air as raw material, undergoes compression and purification, and then uses heat exchange to liquefy the air into liquid air. Liquid air is mainly a mixture of liquid oxygen and liquid nitrogen. By utilizing the different boiling points of liquid oxygen and liquid nitrogen (at 1 atmosphere, the former has a boiling point of -183 ℃, while the latter has a boiling point of -196 ℃), they are separated through liquid air distillation to obtain nitrogen gas. The cryogenic air separation nitrogen production equipment is complex, occupies a large area, has high infrastructure costs, requires a large one-time investment in equipment, has high operating costs, produces gas slowly (12-24h), has high installation requirements, and has a long cycle. Taking into account factors such as comprehensive equipment, installation, and infrastructure, the investment scale of PSA units with the same specifications for equipment below 3500Nm3/h is 20% to 50% lower than that of cryogenic air separation units. The cryogenic air separation nitrogen production unit is suitable for large-scale industrial nitrogen production, while medium and small-scale nitrogen production appears uneconomical.

2 Molecular Sieve Air Separation for Nitrogen Production

Molecular sieve air separation for nitrogen production is a method that uses air as the raw material, carbon molecular sieve as the adsorbent, and applies the principle of pressure swing adsorption to selectively adsorb oxygen and nitrogen using carbon molecular sieve to separate nitrogen and oxygen. It is commonly known as PSA (Pressure Swing Adsorption) for nitrogen production. This method is a new nitrogen production technology that rapidly developed in the 1970s. Compared with traditional nitrogen production methods, it has the characteristics of simple process flow, high degree of automation, fast gas production (15-30 minutes), low energy consumption, adjustable product purity within a large range according to user needs, convenient operation and maintenance, low operating costs, and strong device adaptability. Therefore, it is highly competitive in nitrogen production equipment below 1000Nm3/h and is increasingly popular among small and medium-sized nitrogen users. PSA nitrogen production has become a method for small and medium-sized nitrogen users.

Three membrane air separation for nitrogen production

Membrane air separation for nitrogen production is another new type of nitrogen production technology that rapidly developed abroad in the 1980s, and its promotion and application in China has only been around for the past three to four years. The basic principle of membrane air separation for nitrogen production is to use air as the raw material, and under pressure conditions, utilize gases with different properties such as oxygen and nitrogen to have different permeation rates in the membrane to separate oxygen and nitrogen. Compared with other nitrogen production equipment, it has the advantages of simpler structure, smaller volume, no switching valves, less maintenance, faster gas production (≤ 3 minutes), and convenient capacity expansion. It is suitable for small and medium-sized nitrogen users with nitrogen purity ≤ 98%, and has a good cost performance ratio. When the purity of nitrogen is above 98%, its price is more than 15% higher compared to PSA nitrogen generators of the same specifications. From the above, it can be seen that MnZn ferrite production enterprises should adopt what gas supply method and technology, conduct technical and economic analysis based on the enterprise situation, and choose the best gas supply plan.