Key points for operating membrane separation devices in high-temperature and high-humidity areas: Reference for sites in East China and South China

The same membrane separation oil and gas recovery device, when placed in the high-temperature and high-humidity areas of East China and South China, exhibits significantly different operational performance compared to sites in the north: in summer, the tank area temperature is high, leading to an increase in oil and gas concentration; humidity is high, raising the risk of condensation on the membrane surface; and the load of the condensing unit and defrosting cycle also need to be adjusted accordingly. These differences are not due to equipment quality issues, but rather changes in operating conditions, which require corresponding adjustments in operational management. This article breaks down the impact of high-temperature and high-humidity operating conditions on the device into different stages and provides seasonal operational key points, which can be directly implemented by the operation and maintenance teams at East China and South China sites.

What changes have been brought about by high temperature and humidity

Two things have changed: firstly, temperature - in summer, the gas phase temperature inside the tank is high, the saturated moisture content is large, and the oil and gas concentration is higher under the same gas volume, resulting in a simultaneous increase in the heat load of the condensation section and the permeation load of the membrane; secondly, humidity - if the air moisture content is high and the dehumidification before the membrane is ineffective, moisture will condense on the membrane surface with the airflow, masking the membrane performance in the short term and accelerating the aging of the separation layer in the long term. For ester media, there is an additional layer: esters undergo slow hydrolysis in hot and humid environments, causing the acidity index on the recovery side to drift. These two factors determine that the pre-treatment configuration for devices in high-temperature and high-humidity areas should be one level higher than that for northern stations.

How to enhance membrane pre-desiccant dehumidification

Dehumidification is a key process in operation and maintenance in high-temperature and high-humidity areas: a cold dryer plus a filtration section are configured before the membrane, and the dew point is verified according to local summer operating conditions, rather than the annual average value - the design is calculated based on the annual average value, which becomes apparent during the rainy season and typhoon season. The dew point, temperature before the membrane, and pressure difference are recorded daily, with increased frequency during high humidity seasons; when the dehumidification effect decreases, first check the refrigerant pressure of the cold dryer and the drainer. The defrosting cycle of the condensation section is adjusted seasonally, with the interval shortened during high-load periods in summer; the temperature before the membrane is controlled within an allowable range, and the temperature transition section is frequently checked to prevent low-temperature exhaust gas from carrying fog droplets into the membrane.

How to adjust seasonal operation

Operating parameters are adjusted seasonally: In summer, the frequency of inspections is increased, with a focus on monitoring the dew point before the membrane and the condensation temperature level; the temperature level of the condensing unit is adjusted upward with the temperature, to avoid the refrigeration system operating at full capacity for extended periods; in winter, some stations in South China still face high humidity issues, so the dehumidification section is not shut down. Data is compared on a monthly basis: under the same turnover volume, the trends of power consumption, recovery volume, and pressure difference are observed across seasons, allowing for early detection of anomalies. The plum rain season in East China stations and the humid days in South China are periods of harsh operating conditions throughout the year, so spare parts and filter materials should be prepared in advance, rather than waiting for exceedances before rushing to repair.

Reference for operational key points

Maintenance management checklist

1. Record the dew point before the membrane daily, and increase the frequency to once per shift during high humidity seasons;
2. Draw weekly trends for pressure difference and vacuum degree, and check for pre-treatment in case of sudden changes;
3. The monthly maintenance includes the inspection of the drainer and refrigeration pressure of the refrigeration dryer;
4. The condensation and defrosting cycle is adjusted seasonally, with the interval shortened in summer;
5. Complete the inventory of filter materials and sealing parts before the rainy season;
6. Compare quarterly performance calibration data with initial values for early assessment of attenuation.

Frequently Asked Questions

How significant is the impact of high humidity on membrane lifespan?

Condensation of moisture on the membrane surface can temporarily reduce flux and, in the long run, accelerate the aging of the separation layer. The lifespan of the membrane can vary significantly between devices with proper pretreatment and those that fail to maintain it. Therefore, the investment in pre-membrane dehumidification cannot be omitted.

What should we do if electricity consumption is high in summer?

The increase in temperature and gear settings, as well as the shortening of defrosting cycles, are all seasonal costs, and the key lies in the accounting of recovery volumes. When considering electricity consumption in summer alongside recovery volumes, most stations still achieve a balanced result.

Can the experience from the north be directly applied?

The parameters can be referenced, but the thresholds need to be recalibrated: dew point, defrosting, and temperature and position settings should all be rechecked according to local summer operating conditions. Copying parameters from the north can lead to problems during high humidity seasons.

This article is compiled by Luoyang Wohong Petrochemical Equipment Co., Ltd., which provides design, manufacturing, and operation and maintenance services for condensation recovery, membrane separation recovery, and complete solvent recovery equipment to chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please feel free to contact us for discussion.