The Exhibitor (1957)

As Winter Approaches A Preheater Suggests A Way To Save On Fuel Used on an oil-fired sectional boiler, the Boston Air Preheater introduces a stream of heated secondary air around the burners to burn the heavier fractions of the hydrocarbons that linger at the outer edges of the flame. The valves pictured on the outside of the fire door provide positive control of the amount of incoming secondary air. The Boston Air Preheater is shown in an oilfired boiler application. Heated by radiation, the preheating chamber heats the incoming secondary air to over 400 degrees Fahrenheit. The heated air helps provide maximum fuel combustion, reduces smoke and soot. UEL savings of up to 25 per cent and a marked reduction in smoke and soot, it is said, can be obtained from the Boston Air Preheater, recently introduced in the U. S. by The Preheater Corporation of America. The low-cost unit, which is usually installed in the fire door of the boiler, supplies preheated secondary air over the fire bed or burners for maximum combustion of the fuel. The Boston Air Preheater consists of two basic sections, an adjustable air intake valve that extends outside of the fire door, and a preheating chamber made from a special heat-absorbing alloy mounted on the inside of the door. The air is drawn through the intake by the normal boiler updraft, circu¬ lates through a labyrinth of hot surfaces in¬ side the preheating chamber, and is deliv¬ ered evenly over the fire bed or burners at a temperature of over 400 degrees Fahrenheit. The preheating chamber is heated by radia¬ tion that would normally be lost, so it con¬ sumes none of the fuel energy usable for operating the boiler. The Preheater is designed for use with low or high-pressure, oil, coal, or coke-fired boil¬ ers of the induced-draft, forced-draft or steam-blast type. During the past 10 years, more than 50,000 of these units have been in¬ stalled in Europe in apartment houses, com¬ mercial buildings, theatres, ships, and indus¬ trial plants. Different models are available for all types of boilers. In normal boiler operation, cold primary air is usually admitted through the primary draft or introduced through blowers. How¬ ever, the cold air has two negative effects that prevent it from effecting maximum fuel combustion: its temperature is too low to cause effective combustion of the unburned gases and volatile matter, and it cools the flame and the heat transfer surfaces. As a result, extra fuel is required to heat the air, and the unburned hydrocarbons coming into contact with the cooled boiler walls form soot. The Boston Air Preheater, on the other hand, introduces secondary air at temperatures high enough to promote maximum combustion of the unburned carbon monoxide and the heavier hydrocarbon fractions that linger at the outer edges of the flame and normally settle out as soot or smoke. Introduction of the heated secondary air makes it possible to cut down the intake of fuel-wasting cold primary air. The increased turbulence cre¬ ated by the incoming heated air also aids combustion. Because the rate of combustion is in¬ creased, and the flame hotter and more lumi¬ nescent, more heat is transfered to the tubes by radiation rather than by the less efficient conduction or convection methods. This in¬ crease in heat transfer efficiency reduces the amount of heat wasted through the stack with the flue gases. The elimination of soot on the tubes also increases the efficiency of heat transfer. Meanwhile, tubes and joints last longer because they are no longer exposed to radical temperature changes. The Boston Air Preheater can usually be installed in one day, without interruption of service. Because the unit has no moving parts outside of minor valve adjustments, it is free from the possibility of breakdown and ex¬ pensive maintenance, it is said. The unit is being used successfully in in¬ stitutional, marine, and industrial applications in England, with users reporting average sav¬ ings of 18 per cent. One installation in the U. S. is on the coal-fired steam boiler at a Fabian theatre on Staten Island, New York, where fuel savings over the period of one heating season amounted to approximately $1600. BOSTON AIR PREHEATER PE-8 PHYSICAL THEATRE • EXTRA PROFITS DEPARTMENT of MOTION PICTURE EXHIBITOR October 9, 19 57