Energy and Emissions Reductions

Ronning works extensively with clients to deliver solutions that maximize energy savings and reduce emissions.  Our process-evaluation consulting service helps you understand how to improve your drying process by identifying heat losses and quantifying potential heat recovery processes.

Call with your process specifications and we will estimate the amount of heat recovery available for your operation.

 

Heat Losses and Efficiency

The efficiency of a heating/drying process can be improved by reducing the heat losses.  The primary heat losses in a dryer system are: 
1) Water vapor exiting the stack
2) Dry gas exiting the stack.  

 

Waste Heat Recovery Solutions

Water vapor heat loss can be significantly reduced by: 
1) recovering the latent heat of evaporation in a condensation process.  This process requires the stack gas humidity to be above a threshold value.  When a pound of water vapor is condensed, approximately 1,000 Btu of heat are recovered.
2) reducing the stack gas temperature.  When the temperature of a pound of water vapor is reduced 50°F, about 23 Btu of heat are recovered.

Dry gas heat loss can be reduced in two ways: 
1) reduce the stack gas temperature. When the temperature of one pound of dry stack gas is reduced 50°F, about 12 Btu of heat are recovered.
2) reduce the quantity of dry stack gas.  When the quantity of dry stack gas is reduced by one pound, about 40 Btu of heat are recovered.

 

Rotary Pre-Dryer Heat Recovery Evaporator

Ronning’s rotary Pre-Dryer Heat Recovery Evaporator recovers the latent heat of evaporation in a condensation process.  Of the four methods of heat recovery, the quantity of heat recovered by this method is the highest.

Waste Heat Recovery

Stack Gas Recycle with Ronning Blending Chamber

When properly applied, Stack Gas Recycle reduces the dry gas heat loss by replacing excess air with recycle stack gas.  The Ronning Blending Chamber is specifically designed to apply Stack Gas Recycle to rotary dryer systems.  An additional benefit of this process is a reduction in the flow rate of stack gas to the emission control system.

Heat Recovery in Direct-fired Systems

In Direct-fired Drying Systems, the Ronning Blending Chamber increases stack gas recycle to maximum levels, increasing combustion efficiency and requiring smaller Thermal Oxidation systems, which results in lower capital and operating costs.

Direct Fired Dryer System

The Ronning Blending Chamber reduces the heat loss about 40 Btu for each pound of excess air that is replaced by stack gas, while maintaining the dryer inlet temperature at an acceptable value.

When Stack Gas Recycle is maximized in a Direct-Fired Dryer System, the humidity of the stack gas is high enough that waste heat recovery is possible using a Thin Stillage Evaporator.  This process recovers about 1,000 Btu of heat for each pound of water vapor that is condensed.

Both of these processes reduce the flow rate of stack gas to the emission control system.

Heat Recovery in Indirect-fired Systems

The Ronning Indirect-Fired Dryer System separates the products of combustion and the dryer exhaust into two separate flow streams.  The process increases the humidity of the stack gas to its maximum possible value and allows a Rotary Waste Heat Evaporator and a Thin Stillage Evaporator to recover the maximum quantity of heat.  The Ronning Indirect-Fired Dryer System incorporates integral thermal oxidation of the remaining dryer exhaust gas, eliminating the need for a separate, end-of-pipe Thermal Oxidizer.

In Indirect Drying Systems, we recover heat from the super heated steam dryer exhaust by condensing the water vapor in a Rotary Waste Heat Evaporator and a thin stillage evaporator. These systems recover a high percentage of the Indirect fired Dryer heat input and increase capacity while conserving water and energy.

Indirect Fired Dryer System