Energy conservation today, is not only an economical necessity but also an environmental compulsion. Fuel is a significant cost element in Petroleum and Petrochemicals, Fertilizers and other Process Industries. With exponential rise in the energy consumption and consequent surge in the crude oil prices, energy conservation measures have become even more relevant
Fired Heaters are major consumers of energy and it is of utmost importance to increase their thermal efficiency to the highest possible level. Preheating of combustion air is the best option to raise a heater’s thermal efficiency. The Industry norms have changed over the years and thermal efficiencies of 90-92% have become imperative for the heaters.
It is essential to design and operate heaters to dispose off flue gases at lowest possible temperature. Typically, flue gases leave the convection section of the heaters at around 350 to 450°C and an air pre-heater can bring down this temperature to around 180 – 200°C, resulting in ~10% increase in the efficiency (1% increase in efficiency for every 20°C drop in flue gas temperature). The temperature of flue gas can be brought down further to around 160°C or less in a glass tube air pre-heater, resulting in further efficiency improvement of ~2% or more.
Many fired heaters even today are operating at thermal efficiency of 75-80% or lower. These heaters can be considered for retrofitting with new air pre-heaters to raise the thermal efficiency to maximum level. At today’s cost of energy, the pay off period for an air pre-heater system could be less than a year, besides the advantage of controlled pollution.