The use of submerged combustion technology in a variety of industries to replace traditional but inefficient methods of industrial liquid heating is helping to reduce CO2 and heat emissions to the atmosphere. Photo shows a SubCom™ system recently installed at Konica’s manufacturing plant in Whitsett, North Carolina.

How Submerged Combustion Works
The principle of submerged combustion is very simple: take a glass of water and a straw, blow air into the straw and watch the bubbles rise to the surface.Now imagine that the bubbles are very hot.As they rise to the surface, they heat or evaporate the water in the glass.

In practice, a fuel/air mixture delivered at an elevated pressure is discharged and ignited in a cylindrical combustion chamber submerged in a solution. The combustion is completed within the confines of the chamber; the positive pressure and the flow of the products of combustion prevent the solution from reentering the chamber.

The hot products of combustion — at 2500-3000°F — are discharged into the solution through a series of orifices located around the circumference of the combustion chamber near its bottom end. As the hot bubbles contact the solution, their thermal energy is released through heat and mass transfer.The gas bubbles collapse and become 100% saturated with the evaporated liquid. As the bubbles rise to the surface they cool, while the temperature of the surrounding solution increases.

In a typical single stage submerged combustion system, the temperature of the gas leaving the solution is equal to the temperature of the liquid.In a two-stage system the stack temperature is lower than the solution discharge temperature. It is, in fact, possible in certain conditions to achieve a stack temperature lower than the ambient air temperature.

Industry Applications
As the technology has been refined and improved over the years,SubCom™ systems have been applied to a wide range of industrial process, a few of which are described below: