Steam generation in waste heat boilers

When waste heat recovery boilers are used with process heating furnaces, they fail to get prime attention from their owners and operators. It may be that the plant managers have no training in boiler operation or hazards, and they try to operate the waste heat boiler with no licensed fireman or engineers. That can lead to a catastrophic steam explosion. 

When waste heat boilers are used with steel reheat furnaces, they are often fed gases that are far above the boiler design temperature. Depending on the tightness of the furnace, 2300 F gases may reach the boiler every time there is more than a 15-min 

The major boiler safety concern is maintaining proper water level. Some sections of fire-tube boiler s plate or tube sheet may sometimes not be protected with water backing—when water level is below the gauge glass. 

It is imperative that this compartment, which provides a passage of gases to the very highest fire tubes, have water above it all times. If not, the plate will overheat, its strength will decrease, and the boiler will fail with explosive violence. Water-tube boilers have all heat-exposed surfaces water backed, but control of their water level is more difficult because the water-tube boiler has much less water in its system per unit area of heat transfer surface. Hence, fire-tube waste heat boilers are more widely used for waste heat boilers. Petrochem plants have had good success with water-tube waste heat boilers. 

The feed water supply is most important to protect against boiler failure. Complete dual systems to the de-aerator are essential. When the water level falls to near the bottom of the water level gauge glass, the source of heat to the boiler must be removed immediately Unlike ffiel-fired boilers, where removal of the heat sources is generally not complicated, removal of the heat source from a waste heat boiler applied to a steel reheating furnace may involve large dampers that move slowly and do not shut tightly. 

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