The present invention relates to an assembly for installation into a support structure comprising a spray drying chamber and a product separator , or a section thereof or a frame therefor , to form a spray drying apparatus that can be used to produce a spray-dried product and an outlet gas using a liquid feed and a drying gas. The present invention also relates to a method of producing the assembly, a process for producing the spray drying apparatus comprising installing the assembly into a support structure, a method of spray drying using the spray drying apparatus, and a method of reusing the spray drying apparatus comprising uninstalling the assembly from the support structure and installing a new assembly.