Ronning’s Indirect Drying solution combines emission control, quality, and efficiency into a single package.

The Ronning Indirect process uses intermediate heat for recuperative thermal oxidization of dryer emissions, providing a solution that can be driven completely with biomass energy.  The solution is operating in very challenging waste processing applications and is effective at allowing large-capacity dehydration facilities to operate as a minor source.

The Indirect Fired Three Stage Dryer System uses super-heated steam as the primary drying medium and keeps the ingredients being dried completely separate from the combustion process. Therefore, this system is ideal for delicate and high-value ingredients.

InDirect Flow Diagram

The furnace can utilize various alternative fuels, working as the heat source for drying and as a recuperative thermal oxidizer, heating steam to approximately 700 deg. F. 

The steam and product are induced by a primary fan through a rotating Ronning Three-Stage Dryer Drum where drying product is presented to the steam flow through showering from mini-panel flights and conductive heat transfer fins. Water evaporates from the product as steam and is either recycled into the furnace or recirculated and heated through the heat exchanger.  Water vapor exits the drying drum at a temperature of approximately 230 deg. F. 

The integral thermal oxidation in this system not only saves on upfront capital costs for a regenerative TO, it also saves operational costs with lower horsepower requirement and fewer maintenance issues requiring shut downs.