Drying system for product-air having a very low dew point

A 3-rotor drying system (30,40,50) for producing technical air having a very low dew point comprising three rotary desiccant dryers (2,21,22), each rotary desiccant dryer (2,21,22) comprising a drying sector (2a,21a,22a) and a regeneration sector (2b,21b,22b), the rotary desiccant dryers (2,21,22) arranged in sequence and sharing a common regeneration-air flow path (9) for passing regeneration-air through the respective regeneration sectors (2a,21b,22b) of the rotary desiccant dryers (2,21,22) and a common intake-air flow path (6,7) for passing intake-air through the respective drying sectors (2a,21a,22a) of the rotary desiccant dryers (2,21,22) for dehumidifying the intake-air to product-air having a very low dew point;

• wherein a mixing point (1) for return-air is arranged on the common intake-air flow path (6,7) between a first (2) and a second (21) rotary desiccant dryer, thereby defining
• a product-air flow path (7) for providing dehumidified product-air having a very low dew point to a location of use (4) downstream from the mixing point (1) for return-air, and where on the product-air flow path (7) the drying sector (2a) of the first rotary desiccant dryer (2) is arranged, and
• an intake-air flow path (6) upstream from the mixing point (1) for return-air for providing intake-air to the mixing point (1), and where on the intake-air flow path (6) the drying sector (21a) of the second rotary desiccant dryer (21) is arranged;
• wherein a splitting point (12) for intake-air is arranged between the mixing point (1) for return-air and the second rotary desiccant dryer (21) on a first section (6a) of the intake-air flow path (6), from which splitting point (12) intake-air is diverged as regeneration-air along the regeneration flow path (9);
• wherein a purge sector (2c) and the regeneration sector (2b) of the first rotary desiccant dryer (2) are arranged on the regeneration flow path (9) such that the regeneration-air via an air flow path (9e) first traverses the purge sector (2c) and subsequently the regeneration sector (2b) via a heater (5) arranged on the regeneration flow path (9) between (9b) the purge sector (2c) and the regeneration sector (2b);
• wherein the regeneration sector (21b) of the second (21) rotary desiccant dryer is arranged subsequent to the regeneration sector (2) of the first dryer (2) on the regeneration flow path (9), and
• where upstream on the intake-air (6) flow path and downstream on the regeneration flow path (9) from the second rotary desiccant dryer (21) is arranged an initial rotary desiccant dryer (22), where on the regeneration flow path (9) between (9d) the second (21) and the initial (22) rotary desiccant dryer is arranged an inter-heater (53) for inter-heating regeneration-air prior to traversing the regeneration sector (22b) of the initial rotary desiccant dryer (22);
• the 3-rotor drying system (30) further comprising a return-air flow path (8) for providing return-air from a location of use (4) to the mixing point (1) for return air and one or more air moving means.