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Advanced Carbon Molecular Sieve Technology for Nitrogen Generation
This unit is generally referred to as a nitrogen generator. Its process flow employs the Pressure Swing Adsorption method (P.S.A for short) at room temperature. Pressure Swing Adsorption is an adsorption separation process without an external heat source. According to the aforementioned principle, the carbon molecular sieve's adsorption capacity for the adsorbed components (mainly oxygen molecules) leads to adsorption during pressurization and gas production, and desorption during depressurization and exhaust, enabling the regeneration of the carbon molecular sieve. Meanwhile, the nitrogen gas enriched in the gas phase of the bed layer passes through the bed layer to become the product gas, and each step is connected to form a cyclic operation.
The cyclic operation of the Pressure Swing Adsorption process includes the following working stages: pressurization and gas production; pressure equalization; depressurization and exhaust; followed by pressurization and gas production again, and so on, forming a cyclic operation process. Depending on the regeneration method in the process flow, it can be divided into vacuum regeneration flow and atmospheric regeneration flow.
Based on user requirements, P.S.A nitrogen generator equipment can include an air compression and purification system, a Pressure Swing Adsorption system, a valve sequence control system (which also requires a vacuum pump for vacuum regeneration), and a nitrogen supply system.
Conditions to Be Controlled in Nitrogen Generation Using Carbon Molecular Sieve
1. Air Compression and Purification Process
It is essential for pure raw air to enter the carbon molecular sieve adsorption tower because particles and organic vapors entering the tower can block the micropores of the carbon molecular sieve and gradually reduce its separation performance.
Methods for purifying raw air include: 1. Keeping the air intake of the air compressor away from places with dust, oil mist, and organic vapors; 2. Passing the air through a refrigerated dryer, an adsorbent purification system, etc., and finally allowing the treated raw air to enter the carbon molecular sieve adsorption tower.
2. Concentration and Output of Product Nitrogen Gas
When generating nitrogen gas using carbon molecular sieve, its N₂ concentration and gas output can be adjusted arbitrarily according to user requirements. When the gas production time and operating pressure are determined, reducing the gas output will increase the N₂ concentration, and vice versa. Users can make adjustments based on actual needs.
3. Pressure Equalization Time
In the nitrogen generation process using carbon molecular sieve, when the adsorption in one adsorption tower is completed, the pressurized gas within this tower can be injected into another regenerated adsorption tower from both the upper and lower directions to equalize the gas pressure in the two towers. This process is called pressure equalization of the adsorption towers. Selecting an appropriate pressure equalization time can recover energy and reduce the impact on the molecular sieve inside the adsorption tower, thereby extending the service life of the carbon molecular sieve. Generally, referring to the valve switching speed, a pressure equalization time of 1 - 3 seconds is selected.
4. Gas Production Time
Based on the different diffusion rates of carbon molecular sieve for oxygen and nitrogen adsorption, the adsorption of O₂ reaches equilibrium in a short time, during which the adsorption amount of N₂ is very low. A shorter gas production time can effectively improve the gas production rate of the carbon molecular sieve, but it also increases the valve's operating frequency, so the valve's performance is also crucial. Generally, an adsorption time of 30 - 120 seconds is selected. For small-scale high-purity nitrogen generators, a short gas production time is recommended, while for large-scale low-concentration nitrogen generators, a long gas production time is recommended.
5. Operating Pressure
Carbon molecular sieve exhibits both kinetic and equilibrium adsorption effects. A higher partial pressure of the adsorbate results in a higher adsorption capacity, so pressurized adsorption is advantageous. However, excessively high adsorption pressure increases the requirements for air compressor selection. Additionally, the requirements for adsorption pressure differ between the atmospheric regeneration and vacuum regeneration processes. Considering various factors, it is recommended to select an adsorption pressure of 5 - 8 Kg/cm² for the atmospheric regeneration process and 3 - 5 Kg/cm² for the vacuum regeneration process.
6. Operating Temperature
Selecting a lower adsorption temperature as an adsorbent is beneficial for the performance of carbon molecular sieve. If possible, reducing the adsorption temperature in the nitrogen generator process is advantageous.
Product Packaging and Usage
- This product undergoes strict quality inspections according to enterprise standards before leaving the factory to ensure that quality indicators meet the requirements.
- The product is packaged in sealed plastic drums with good airtightness. It should only be opened when filling and using it to prevent moisture absorption.
- The filling should be compact, and appropriate methods can be used for compaction. Do not directly pound it with a stick.
Pressure: Lower than the N₂ pressure of the raw gas by 0.1 Mpa
Temperature: ≤40℃
System Composition
The PSA-N₂ purification unit consists of a mixer, a catalytic reactor, an after-cooler, a cyclone separator, a filter, an adsorption dryer, an oxygen analyzer, a flow meter, and a product nitrogen gas buffer tank. See the process flow diagram. Based on the actual oxygen content continuously monitored, the amount of hydrogen added to the raw gas is adjusted. To minimize excess hydrogen, a specially designed mixing device and a high-precision hydrogen control system are employed. The mixed gas then enters a catalytic reactor, where hydrogen reacts exothermically with oxygen to form water vapor. Most of the water vapor can be condensed by an after-cooler and removed by a high-efficiency water separator. Subsequently, depending on the required dew point of the product gas, a refrigerated dryer or an adsorption dryer is used for drying. A refrigerated dryer can produce product gas with a dew point of -25℃ at atmospheric pressure, while an adsorption dryer is required for a dew point below -40℃. The purity of the product gas is continuously monitored by an oxygen analyzer. When the purity of the product gas is lower than required by the customer, it is vented. The entire system is fully automated and does not require operators.
Dalian Chuangge Technology Co., Ltd
Richard Han
Doris Zhou
Headquater: 9th Floor, Century Classic Building, No.10, Xinghai Square, Shahekou District, Dalian City, Liaoning Province
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