Compressed condensate membrane separation, suitable for medium and high concentration organic waste gas

When selecting a treatment process for VOCs exhaust gases, concentration is a key criterion. When the concentration is low, the condensation recovery efficiency is not ideal and the economy is not obvious; when the concentration is too high,activated charcoaladsorption saturation is too fast,RTOCombustion is faced with the safety risk of high calorific value. The applicable concentration range of compression condensation membrane separation process is relatively clear-medium and high concentration range (above 1000 mg/m).

Why is it more suitable for high concentration?

The condensation method requires that the inlet gas concentration is sufficiently high. The partial pressure of the organics in the gas is proportional to the total pressure and the mole fraction. The higher the concentration, the higher the saturated vapor pressure at the same condensation temperature, the greater the amount of condensable. When the concentration is above 2000 mg/m, most VOCs can be effectively liquefied by three-stage condensation. When the concentration is low, the temperature needs to be reduced to a lower level to achieve the same recovery rate, and the energy consumption increases significantly.

Membrane separation is also concentration-driven. The organic partial pressure difference between the two sides of the membrane is the driving force of the osmosis process. The higher the inlet gas concentration, the greater the partial pressure difference on both sides of the membrane, and the corresponding increase in permeation flux and concentration multiple. The research shows that the membrane VOCs recovery technology is mainly used in the concentration of more than 1% of VOCs gas recovery, can recover aromatics, alkanes, olefins, halogenated hydrocarbons and so on.

Concentration Adaptation Logic for Combinatorial Processes

For waste gas with a concentration of more than 1000mg/m³, most of the organic matter can be liquefied by compression and condensation to reduce the concentration to the appropriate range of membrane separation, and then the residual tail gas is deeply enriched by the membrane module to form a complete concentration conversion chain. For the concentration of VOCs exhaust gas in the range of 500-6000ppm, the study found that when the condensing pressure is 0.55MPa and the condensing temperature is -10 to -15 ℃, the combined process can achieve a balance between the recovery efficiency and the operating energy consumption.

How high is the appropriate concentration?

The compression-condensation membrane separation process is especially suitable for the recovery of medium-to high-concentration organic waste gas with inlet concentrations of 10000 to 100000 ppm (about 10-100g/m³). For the exhaust gas with low concentration, the membrane module can be used for pre-concentration before entering the condensation unit, so that the gas concentration entering the condensation unit is in the economic recovery range. Suitable for chemical, pharmaceutical, printing, storage tank area and other high concentration exhaust gas scene. It is recommended to complete the exhaust gas detection before selection, and match the process parameters according to the concentration and components.