A modular compressed-gas dryer including in series: an inlet module, a precooler/reheater module, an evaporator module, and a sump module. The modules form columns where at least one column has a filtration chamber. Further provided are a gas outlet and gastight seals between modules. The system creates a first and second set of heat transfer passages where refrigerant passes through the second set in a heat exchange relationship in a direction perpendicular to incoming gas passing in the first set. The filtration chamber conducts chilled gas from the first set to a third set of heat transfer passages. The third set extends through the precooler/reheater in heat exchange relationship with the first set. Chilled gas passes in heat exchange relationship in a direction perpendicular to the incoming gas so that the incoming gas chilled in the evaporator exchanges heat with the incoming gas in the precooler/reheater.