Membrane Air Separation System From Dow Produces Gaseous Nitrogen On-Site, Economically

The Dow Chemical Company has announced a modular air separation system based on its advanced membrane technology. The new GENERON ® systems produce 95-99 percent nitrogen and, according to Dow, are simple and safe to operate.

As a consistent source of enriched nitrogen, the systems are expected to fill a broad range of industrial and commercial applications. This type of nitrogen is used extensively in the chemical process industry (CPI), metal producing and metalworking industries, and food processing.

On-site production of gaseous nitrogen via the GENERON system can yield significant cost savings compared with alternative sources of nitrogen.

Compared with previous methods of on-site nitrogen generation, the GENERON air separation system is a compact, self-standing unit that can operate unattended. With no moving parts, it is basically simple to maintain. The system requires no flame source, and its nitrogen product contains fewer contaminants than nitrogen generated via conventional inert gas generators (IGG).

The system also produces an oxygen- enriched stream that is properly vented or may be used for a variety of in-plant purposes.

System capacities typically range from 300 to 15,000 SCFH (standard cubic feet per hour). As a modular unit, it is a simple matter to tailor a system to current and changing needs. The entire system, including basic instrumentation, is skidmounted and is easily positioned with a forklift. The skid-mounting also facilitates relocation of the system if process needs or plant layouts change. The compact design permits a system to be installed within tightly confined spaces.

In the GENERON system, the separation of nitrogen and oxygen constituents of air depends on their relative permeability through hollow fiber membranes. Each module contains millions of these membranes wijthin a pressure case.

Gases such as oxygen exhibit a high permeability compared to nitrogen and pass readily through the membrane. Nitrogen, on the other hand, has an appreciably lower permeability rate and so a significantly smaller proportion is able to permeate the membrane. In effect, a large portion of the nitrogen is swept past the hollow fiber membrane, while all but a small percentage of the oxygen passes through.

Plant air, typically at 75-90 psi, provides the required driving force for the separation process. The pressurized air can be supplied from an existing plant air system or from a built-in auxiliary air compressor.

The compressed air enters the module through a perforated tube running lengthwise down its center.

The feed tube distributes the compressed air uniformly to the fiber bundle.

Thus, the incoming air stream is separated into an oxygen-enriched "permeate" stream and a nitrogenenriched "non-permeate" stream.

Water vapor also permeates the membrane rapidly, thus producing a dry nitrogen-enriched product stream. This stream exits the unit via a connection on the side of the module. The oxygen-enriched stream exits through the end caps to connections on each end of the module.

The GENERON air separation system consists of a number of membrane modules, connected in parallel. Installation of a unit requires only piping for compressed air feed and for outing the nitrogen to its end-use destination.

In addition to the membrane modules, a GENERON system includes an oxygen analyzer, appropriate flow meters and pressure gauges as well as a coalescing filter for removing oil droplets from the compressed air feed. No desiccant dryer is needed.

The GENERON air separation system provides a high degree of operating flexibility. If required, the system can be operated either on a continuous basis or intermittently.

For complete details on the GENERON air separation system from Dow Chemical, Circle 24 on Reader Service Card

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