Precautions of using oxygen molecular sieve in small medical oxygen generators

Feasibility and precautions of using oxygen molecular sieve in small medical oxygen generators

I. Feasibility analysis

Functional complementarity

Lithium molecular sieve (LiLSX): Highly efficient and selective adsorption of nitrogen (N₂), it is the core material for purifying oxygen (N₂/O₂ selectivity ≥6).

13X-HP molecular sieve: Preferentially adsorbs water (H₂O) and carbon dioxide (CO₂) to protect lithium molecular sieve from contamination.

Synergistic effect: When layered loading, 13X-HP pre-treated gas can extend the life of lithium molecular sieve and improve system stability.

Applicable scenarios

High humidity/high CO₂ environment: When gas pretreatment needs to be strengthened, 13X-HP can reduce the load of lithium molecular sieve.

Cost-sensitive equipment: 13X-HP is relatively low in price, and mixed use can reduce some costs (but the efficiency loss needs to be weighed).

II. Mixed use scheme

1. Recommended scheme: layered filling

Upper layer (inlet end): 13X-HP molecular sieve (accounting for 20%-30%), adsorbing H₂O and CO₂.

Lower layer (main adsorption layer): lithium molecular sieve (accounting for 70%-80%), dedicated to N₂ adsorption, ensuring oxygen purity ≥90%.

Separation measures: Use porous support plates or metal grids to isolate the two layers to avoid physical mixing.

Not recommended scheme: physical mixing

Competitive adsorption: 13X-HP will partially adsorb N₂ (N₂ capacity ≥8ml/g), reducing the efficiency of lithium molecular sieve.

Regeneration conflict: 13X-HP regeneration temperature (200°C) is incompatible with lithium molecular sieve (300°C), resulting in incomplete regeneration.

Powdering risk: particle friction accelerates molecular sieve wear and blocks air flow channels.

III. Key points

Filling parameter optimization

Filling height: The thickness of the lithium molecular sieve layer must be ≥30cm (5L model) to ensure sufficient adsorption capacity.

Airflow distribution: Add a guide plate or flow equalizer to prevent partial overload caused by bias flow.

Regeneration control

Segmented regeneration:

First regenerate 13X-HP at 200°C (15-20 minutes).

Then regenerate the lithium molecular sieve at 300°C (30-40 minutes).

Regeneration gas flow direction: flow from bottom to top, and regenerate the main adsorption layer first.

Inlet pretreatment

Dryer: The inlet dew point needs to be <-40°C (silica gel or molecular sieve pretreatment).

Filter: Remove particulate matter (<0.01 μm) and oil mist to avoid clogging the molecular sieve pores.

Performance monitoring

Oxygen purity: Real-time monitoring (≥90%), check the molecular sieve or pretreatment system when the purity decreases.

Pressure drop detection: normal range 50-150 Pa/m, abnormal increase requires checking for blockage or pulverization.

IV. Risks and countermeasures

Risk Cause Solution

Oxygen purity <90% 13X-HP competes for adsorption of N₂ or regeneration is insufficient Increase the proportion of lithium molecular sieve to ≥70%, regenerate in stages

Abnormal increase in pressure drop Molecular sieve pulverization or uneven airflow Check loading uniformity and replace pulverized molecular sieve

Regeneration efficiency decreases Mixed regeneration temperature conflict Independently control regeneration temperature and time

Equipment certification failure Mixed design does not pass medical standard verification Communicate with FDA or announcement agency in advance

VI. Maintenance recommendations

Monthly inspection: molecular sieve pulverization, sealing, sensor accuracy.

Quarterly replacement: pre-desiccant and filter.

Annual deep maintenance: completely replace molecular sieve and calibrate control system.

VI. Conclusion

Feasible but requires strict design: Layered loading of 13X-HP (≤30%) + lithium molecular sieve (≥70%) can meet medical requirements (≥90% purity).

Avoid physical mixing: Mixed packing can lead to reduced efficiency and stability risks.

Priority compliance: Facilities with FDA 510(k) or ISO 13485 certification are required to submit validation data for the mixing scheme.

Recommended actions:

Test the actual performance of layered packing (purity, pressure drop, life) on a prototype.

Work with molecular sieve suppliers (such as XINTAO) to optimize packing parameters.

Ensure that the regeneration system supports temperature stage control.