November 4, 2019
The origin of steam generation goes back several hundred years to the development of the kettle-type boiler in the late 1700s. Rudimentary at best, it would be almost a century later before George Babcock and Steven Wilcox launched the steam generation industry with the introduction of their hand-fired, coal powered steam boiler.
An improved tube and tile design in the mid-1900s allowed for not only an increase in boiler size and capacity but improved thermal efficiency as well. While boiler choice varies according to the customized needs of the facilities they serve, one constant remains: the continued need for thermal efficiency.
The good news is that improved efficiency doesn’t necessarily mean an expensive capital overhaul. Improving boiler combustion by even a few percentage points can translate into substantial savings for building owners while helping contribute to decreased emissions.
In a perfect world, we’d be able to extract all the energy available in fuel, however, 100% combustion is realistically unachievable for boiler operation. Even a slight variance in any one of the three reactants — fuel, temperature and oxygen — can impact the chemical process needed to sustain combustion.
Combustion efficiency increases with increased reactant temperature, increased surface area, increased chemical energy, and increased vapor pressure. Too little oxygen can lead to fireside sooting, air pollution, and potentially explosive gases while too much oxygen can make it difficult to maintain a consistent ignition temperature.
Water, while not a reactant, must also meet certain criteria in order to be used effectively to generate heat. Careful consideration should be given to the quality of the feed water as all water contains varying amounts of dissolved and suspended matter and dissolved gasses.
Finally, every boiler design is unique with its own requirements for optimal efficiency. The challenge is then for boiler operators to commit to really understanding the needs of their system. A trustworthy partner who can help navigate boiler variances is always recommended in addition to the below considerations.
Proven steps to improve boiler efficiency
- To help minimize excess air cushion, fine-tune the boiler under varying ambient and load conditions by monitoring the boiler’s flue gas temperature and oxygen content. You can do this by performing a weekly carbon dioxide efficiency test to manually adjust the percentage of air needed for optimal fuel combustion.
- For forced draft boilers, consider installing an automatic combustion control system for consistent fuel combustion.
- Use condensate from a steam boiler to minimize the use of cold water which must be heated before use. Condensate also helps reduce component corrosion and scale build-up within the system.
- Preheat both feed and makeup water by using waste heat
- You can also recover heat from the exhaust to preheat makeup water. However, take care not to remove too much heat as the flue gases could condense, causing corrosion.
- Preheat combustion air to compensate for large temperature difference between the ceiling of your boiler room and your boiler’s intake air location.
- Insulate the boiler to reduce its hot air loss.
- Replace old and inefficient burners or burners that are oversized for your needs. A modern and properly sized burner can help improve efficiency by up to 5%.
- Increase heat transfer by inserting metal baffles into fire tube boilers. The baffles, known as turbulators, slow down the combustion gases by increasing the surface area of the boiler.
- Install soot blowers to help keep the fire-side surface of solid fuel or oil-fired boilers clean.
- Even if you engage one or more of the above options to increase efficiency, always have your system inspected annually. It’s both a safety and an efficiency measure.
Please consult a knowledgeable partner before engaging in any efficiency improvements. A reputable company will conduct a boiler system audit to evaluate first if your system is losing energy and second determine the cause(s) of any inefficiencies. Good energy management always minimizes heat loss, saving you money while improving troublesome emissions.
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