PSA Plants Types

Pressure Swing adsorption has undergone rapid changes as the technology of separation processes advanced with the passage of time. It is very important to choose the correct Pressure swing adsorption system that exactly caters to the specific requirqment in terms of production needs like quality, etc. The following parameters play an important role in determining as to which type of PSA system to opt for:

 

Unit Capacity: For example a typical four Bed system will be used when requirement is less than 5,000 Nm3/h of feed rate. Medium to large-capacity PSA units are employed i.e. greater than 50,000 Nm3/h of feed for maximum product recovery.
Unit Cost: As the the cost of a PSA unit increases with the increase in pressure equalisations, smaller PSA units are preferred that utlizes one or two equalisations at the expense of little recovery loss. The investment costs needed to be combined with the value of the product gas to find the exact gas recovery system that incurrs the lowest overall cost.

 

The following table can be taken as a guideline to choose a PSA system based on the ratio of feed and offgas pressures vis-a-vis the feed gas flow rate. The Pressure Swing Adsorpotion units for feed gas rate are in the range of 5,000 - 50,000 Nm3/h.

 

Feed and offgas pressure:

The adsorption pressure is fixed by two ways-

 

For example taking the case of Hydrogen recovery, the range of feed pressure hovers between 10 and 40 bar. It is to be noted that a high feed gas pressure is the choice when it comes for high hydrogen recovery with low investment expenditure. Here, the pressure drop from feed to product is comparatively small, also the product is found available at a pressure of 0.5 bar lower than the feed gas. Offgas pressures typically range between atmospheric -10 bar. This is the most influencing parameter on hydrogen recovery. It has been generally found that lower is the offgas pressure, morer the hydrogen recovery a possibility, and with it obviously comes lower the investment costs for a fixed production rate. A 4:1 minimum ratio must be maintained by the absolute feed pressure with the absolute waste pressure.

 

Composition of the Feed Gas: The PSA process are geared to handle feed gas with a large variety of impurities. Generally the process performance changes with the adsorption-desorption properties of a specific componenton the selected adsorbent. The table below gives a description of the impurities in

Product Purity: Some advantages with respect to product gas recovery and investment expenditure can be gained at the expense of a less-strict purity specification.

 

 

 

 

 

Tags:- Pressure Swing Adsorption Types, Types Of PSA System

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