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

A 3-rotor drying system for producing technical air having a dew point below −30° C. comprising a first, a second, and a third rotary desiccant dryers, each rotary desiccant dryer comprising a drying sector and a regeneration sector, the rotary desiccant dryers arranged in sequence and sharing a common regeneration-air flow path for passing regeneration-air through the respective regeneration sectors of the rotary desiccant dryers and a common intake-air flow path for passing intake-air through the respective drying sectors of the rotary desiccant dryers for dehumidifying the intake-air to product-air having a very low dew point;

• wherein a mixing point for return-air from a location of use is arranged on the common intake-air flow path between the first and the second rotary desiccant dryer, thereby defining:
• a product-air flow path for providing dehumidified product-air having a very low dew point to the location of use downstream from the mixing point for return-air, and where on the product-air flow path the drying sector of the first rotary desiccant dryer is arranged, and
• a first section of the common intake-air flow path upstream from the mixing point for return-air for providing intake-air to the mixing point, and where on the first section of the common intake-air flow path the drying sector of the second rotary desiccant dryer is arranged;
• wherein a splitting point for intake-air is arranged between the mixing point for return-air and the second rotary desiccant dryer on the first section of the common intake-air flow path, from which splitting point intake-air is diverged as regeneration-air along the common regeneration flow path;
• wherein a purge sector and the regeneration sector of the first rotary desiccant dryer are arranged on the common regeneration-air flow path such that the regeneration-air first traverses the purge sector and subsequently the regeneration sector via a heater arranged on the common regeneration-air flow path between the purge sector and the regeneration sector;
• -wherein the regeneration sector of the second rotary desiccant dryer is arranged subsequent to the regeneration sector of the first dryer on the common regeneration-air flow path, and
• where upstream on the common intake-air flow path and downstream on the common regeneration flow path from the second rotary desiccant dryer is arranged the third rotary desiccant dryer, where on the regeneration-air flow path between the second and the third rotary desiccant dryer is arranged an inter-heater for inter-heating regeneration-air prior to traversing the regeneration sector of the third rotary desiccant dryer;
• the 3-rotor drying system further comprising a return-air flow path for providing return-air from the location of use to the mixing point for return air and one or more of pumps, bellows, or fans,
• wherein the 3-rotor drying system further comprises at least one filter arranged on the common intake-air flow path for removing airborne particles from the intake-air, and
• wherein the at least one filter comprises at least a first, a second and a third filter, each respective filter arranged downstream from a preceding respective third, second, and first rotary desiccant dryer in ascending order of filter class.