Temperature Swing Adsorption — Applications and System Design

Temperature Swing Adsorption is an adsorption-based separation process in which the adsorbent is regenerated by raising its temperature, which releases the adsorbed components. In contrast to Pressure Swing Adsorption (PSA), which uses pressure reduction for regeneration, TSA uses heat input — typically from a hot regeneration gas stream.

The basic TSA cycle consists of an adsorption step, in which the feed gas passes through the adsorbent bed and the target components are retained, followed by a regeneration step in which hot gas is used to heat the bed and desorb the retained components, and then a cooling step to return the bed to adsorption temperature.

The adsorbent used in a TSA system is selected based on the component being removed and the conditions of the process stream. Molecular sieve (zeolite) materials are widely used for deep dehydration duties due to their high affinity for water vapour and ability to achieve very low dew points. Activated alumina is used for moderate drying applications. Activated carbon is used where hydrocarbon or organic component removal is required.

The choice of adsorbent also affects the regeneration temperature required. Molecular sieves typically require higher regeneration temperatures than activated alumina, which has implications for the heating system design and energy consumption.

Dehydration of natural gas is one of the most common applications for TSA systems. Water vapour must be removed from natural gas to meet pipeline specifications and to prevent hydrate formation in pipelines and process equipment operating at low temperature.

TSA molecular sieve dryers can achieve very low water dew points, making them suitable for duties where glycol dehydration does not meet the required specification, or where the gas is being processed for liquefaction or cryogenic application.

Beyond natural gas service, TSA systems are applied across a range of industrial gas drying and treating duties including instrument air and plant air drying, process gas drying ahead of cryogenic separation, removal of trace contaminants from gas streams, and drying of fuel gas streams.

In hydrogen service, TSA drying systems are used to dry hydrogen downstream of electrolysers and in other applications where a low dew point hydrogen product is required before downstream processing.

TSA system design involves selection of the adsorbent, number of beds, bed sizing, regeneration gas source and temperature, cooling arrangement and the overall cycle timing. Two-vessel systems are common, allowing one bed to adsorb while the other regenerates, though larger systems or duties with demanding cycle timing may use three or more vessels.

The regeneration gas may be a slipstream of the dry product, a separate gas source, or a combination. The energy required for heating is a key operating cost consideration and influences the design of the heating system.

Howe Baker engineers and supplies TSA systems for gas drying and contaminant removal applications. Design scope covers process design, adsorbent selection, mechanical equipment specification and control system design. TSA systems are offered as part of broader process plant packages and as standalone engineered units.