Gypsum/Wallboard Industry
Food & Beverage Industry
Pulp & Paper Industry
Boilers
 







 

THE CHALLENGE
The Gypsum/Wallboard Industry and related facilities utilize a very large amount of heat in various areas. Heat is needed to calcine the CaSO4 . 2(H2O) “rock” to CaSO4 . 1/2(H2O) “plaster of paris” as well as to dry and set the wall board after forming. The hot and humid process gas generated from both the calciner(s) and kiln dryer(s) have frequently been vented to atmosphere, due largely to the limitations of traditional heat recovery equipment (fouling, etc.). Separately, the heat requirements of the calciner(s) and the dryer(s) are normally supplied using direct-fired air heaters.

THE ANSWER
The Direct Contact Inc.(DCI) Heat Recovery System overcomes the limitations of traditional heat recovery equipment and links the heat contained in a portion of the calciner exhaust stream (chosen to take advantage of the higher wet bulb temperature) with a circulating “hydronic” loop. The patent-pending design of the heat recovery vessel recovers both the latent and the sensible heat in the gas stream and sends it to process or the “hydronic” loop in the form of very hot water.  This loop passes through hot water-air heaters to preheat combustion air feeding the calciner(s) and the dryer(s)

THE DIRECT BENEFITS
The overall heat efficiency of the Gypsum/Wallboard process increases dramatically while the waste streams emitted from the process are reduced at the same time. Energy savings can quickly add up to offset the initial purchase and installation cost of the Direct Contact Inc.(DCI) Heat Recovery System and start to contribute to the mill’s bottom line profitability. Another consideration is that a significant amount of water is condensed as the hot and humid calciner exhaust is cooled and reduces the mill’s overall makeup water requirement (typically used to re-hydrate the Gypsum).

Additional benefits can be realized when other hot water requirements are considered (e.g. heating of mill makeup water going to the forming process, preheating of Boiler Feedwater, etc.). Similar results are anticipated for facilities and systems used in the manufacture of Ceiling Tiles and Fruits or Egg Cartons.