Importance of Heat Exchanger and Tips to Increase its Efficiency

 Importance of Heat Exchangers in Steam Boilers:

In a boiler system, the hot-water radiators harness heat from hot gas jets, but initially, the water needs to absorb the heat energy from the gas. The heat exchanger safely allows the passing of heat energy from gas to the water. If water is heated directly from the gas, the flames would be extinguished by the water. The basic principle of the heat exchanger is that it allows the transferring of the heat without transferring the fluid (liquid or gas) carrying the heat. The surfaces through which heat passes are called heat transfer surfaces. Heat transfer takes place in the steam boiler, where hot gasses from the combustion of fuel transfer levels of intense heat through the steam boiler tubes to produce steam.

The build-up of any hindering material such as scale, corrosion products, or micro-organisms on heat transfer surfaces slows down the heat exchange.

Indications of Issues in Heat Exchangers:

Several indicators point towards issues in heat exchangers and require prompt actions. Some of them are as follows,

Black Soot:

Black soot around the furnace is a clear sign that the gas is not burning properly. Unhealthy and incomplete combustion leads to dirty soot around the furnace. It usually leads to a damaged heat exchanger or an issue with the burner or furnace flame.

Unpleasant Smell:

Although gasses such as carbon monoxide are odorless, any strange or unpleasant odor near the furnace or air ducts requires professional attention. Cracked heat exchangers can leak combustion gasses into the boiler system that can cause a clear and present odor. In such situations, it is crucial to immediately turn off the heating system and seek professional help to diagnose the situation.

Water Surrounding the Furnace:

If water is found on the floor near the furnace, it may indicate a problem with the heat exchanger. Whether it is condensation or a cracked heat exchanger, seek professional help right away to determine the cause.

Outdated System:

If there are complaints of other aging problems with the furnace, such as wear and tear, loud noises, it is ideal to have a professional diagnose the entire steam boiler system.

How to Increase the Efficiency of the Heat Exchanger in Steam Boiler?

 The ideal method to reduce the operating expenses in a process plant is by using and maintaining energy-efficient equipment

• The major heat loss in the boiler heat exchanger is caused by the boiler water. Therefore, it is necessary to ensure that heat exchangers generate as minimal exhaust or flue gas as possible. Maintaining the minimal temperature within the heat exchanger accelerates the steam boiler efficiency.
• Using an economizer allows the facilities to use the otherwise wasted hot exhaust gas for heating the feed-water. It helps in saving fuel and preventing the hazardous effects of feeding the steam boiler with cold water.
• Tune the burner regularly as boiler efficiency is also impacted by insufficient air. Proper combustion needs sufficient oxygen in the boiler. In the case of insufficient air, the carbon within the fuel is incompletely oxidized, leading to carbon monoxide production. It causes a reduction in fuel efficiency and less heat because fuel is not burned completely. Less air also generates smoke, soot, and carbon monoxide that cause hazardous conditions.
• Installation of a VFD (variable frequency drive) offers significant power savings due to the use of circulation pumps and fans that leads to controlled flow.
• Insulate valves to prevent valve exposure and avoid heat loss that can make boiler rooms unbearably hot. Insulating the boiler valves helps in increasing boiler room comfort and reducing burn risks.
•  Maintaining a clean waterside that is free of leaks. It requires regular and proper water treatment and inspection of mud legs or drums as it ensures efficient heat transfer from metal to water. If the steam boiler is not blown-down regularly, the scale accumulates on the heat transfer surface, hindering the heat transfer.
•  Reducing excess air for efficient combustion as insufficient air could lead to incomplete combustion. Excess amounts of air can cause different inefficiencies, such as reduced combustion.
• Removal of the soot and build-up on the fireside of the boiler tube. It is found particularly in older boiler heat exchanger equipment. Soot and grime in the boiler tube reduce the heat transfer rate and cause the equipment to operate harder, thus increasing fuel use.
• Recover heat through the blowdown. The blowdown valve eliminates boiler water consisting of both insoluble and soluble solids. It helps to reduce the level of dissolved solids that leads to boiler scale. However, it also removes hot water, which in turn wastes energy. A blowdown heat exchanger or a flash tank aids in recovering lost energy and improving the efficiency of the boiler system.
• Reduce carry-over to avoid impurities and ensure proper levels of BTU content at end-use.

Impact of poor heat transfer in the steam boiler:

• A 5% reduction in heat transfer leads to the plant achieving only 95% of its potential output. 
• An increase in energy consumption as pumping costs increase because water must be circulated more rapidly in an attempt to restore cooling efficiency.
• Overheating causes tube failures and other system components. It requires immediate shutdown of the equipment as it may cause injury to personnel working in the area of a failure.

Conclusion:

Rakhoh Boilers are one of the leading manufacturers of industrial steam boilers in Pune since 1983. Over 38+ years, Rakhoh has successfully installed more than 3000 boilers in 26 countries worldwide. We also provide excellent boiler services like energy audit, boiler automation, steam trap assessment, annual boiler maintenance, fuel conversion, etc.

For more details on our products and services, visit www.rakhoh.com