With energy bills on a rise, companies today need to keep a close eye on their costs using monitoring and targeting so they can identify areas where energy is wasted and introduce cost saving measures.
One of the areas where sizable savings can potentially be saved is through their steam boiler.
Steam boilers are present in most industrial & commercial facilities and the energy efficiency of your boiler system centres around keeping your boiler clean and free of scale.
Water fed to the boiler is normally treated to prevent scale and corrosion formation but no matter what is done to prevent these problems, they inevitably will appear, but in a controllable way.
Boiler scaling will cause many hazards and will affect the normal operation of the boiler. It can be a hard, tenacious deposit or a softer coating of insoluble salts, which forms on boiler tubes and walls. It’s often caused by makeup water hardness, which refers to the naturally occurring calcium and magnesium ions found in water.
A reduction in energy efficiency means the boiler must burn more fuel to maintain the same output. Over time, that increased fuel demand can get very expensive.
By keeping the boiler free of scale, the unit is maintained at peak efficiency, resulting in lower fuel costs.
Scale – The Number One Issue
Water hardness is the number one contributor to boiler scale. There are other reasons for the formation of scale, but the naturally occurring ion combinations are the predominant culprits, particularly in low-pressure systems.
The essential principle is that the thicker the scale, the greater the percentage of the reduction in the energy efficiency of the system. The mineral scale not only lowers the efficiency of the device but also promotes the corrosion due to uneven heat distribution.
Preventing scale may involve, but not be limited to, filtration, pre-treatment of the water entering the boiler and chemical treatment.
Scale – The Hazards
There are a number of issues that scale build up cause, while we mentioned the reduction of efficiency, lets take a look at a few more:
Waste of fuel
When the boiler scales, the heat transfer performance of the heating surface worsens, this means the heat released by the fuel combustion cannot be quickly transferred to the pot water. A large amount of heat is taken away by the flue gas and the thermal efficiency of the boiler is reduced.
Damage the heating surface
The wasted fuel leads to an increase of temperature difference on both sides of the heating surface. The type and thickness of scale are different, and the heating surface metal temperature is different which causes great damage to the heating surface, and then causes the damage and scrap of industrial boiler.
Reduce the boiler output
After scaling has formed, to achieve the rated evaporation or rated heat production of the boiler, it needs to consume more fuel. With the increase of scaling thickness, furnace volume and grate area are certain, fuel consumption is limited, therefore, boiler output will be reduced.
Reduce the service life of the boiler
The scale on the heating surface of the boiler must be completely removed to ensure the safety and economic operation of the boiler. If the scale is not seen to the problem will get worse and the equipment will start to fail and require more maintenance, eventually leading to premature failure.
Scale – Factors that Impact Scales’ Formation
Poor maintenance of a boiler or the pre-treatment system can quickly result in scale, and create potential hazards to employees as well. Here are a few other things that can help escalate the growth of scale
System Pressure
The pressure at which a boiler operates can contributes to the amount of scale in the boilers. Industry guidelines dictate the type of chemistry and the level of pressure at which systems can run.
Boiler Design
Certain boiler designs are more susceptible to scale than others. Boiler design can contribute to the efficiency of the system. Some systems have a different heat flux rate at the tube’s surface, even though they may have the same pressure rating.
Condensate return
Condensate is formed when steam vapor returns to its liquid state. When this happens as a result of steam used in the process application, the recovered condensate can retain about 13% of the total energy of the steam vapor. If not properly monitored or treated, contaminated condensate water can contribute to scale in the system.
Pre-treatment
Pre-treating your boiler system water begins with an analysis of the water going into your system. Pre-treatment will likely include the removal of solids (suspended and/or dissolved) via filtration, softening or demineralization, and also dissolved oxygen removal via deaeration or a hot water tank. An inadequate or poor pre-treatment plan can contribute to scale and deposition due to hardness and iron.
Energy Saving Tips
Here are a few tips that you can use to help save energy and costs relating to your steam boiler:
- Have a water treatment plan in place. Ensuring the correct chemicals and maintenance is being carried out will ensure the steam being used is pure and the equipment is working as efficiently as it can be. This will ensure the boiler is working to its optimum level and not consuming wasted energy. This will also reduce the equipment downtime & maintenance costs.
- Regularly examine feedwater quality and ensure that it conforms to local industry standards.
- Regularly measure and record fuel usage, exhaust gas temperature and residual oxygen content, boiler pressure, steam output, and boiler blowdown water levels.
- Reduce steam demand
- Reduce Combustion Excess Air. Measure and control air-fuel ratio or oxygen and carbon monoxide content of flue gases from process heating equipment, this has an estimated energy savings range of 2% to 15%
- Set suitable minimum levels of fuel quality and viscosity to improve the efficiency of fuel combustion.
- Clean Heat Transfer Surfaces. Cleaning heat transfer surfaces lowers flue gas temperature and increases efficiency by improving heat transfer. Doing so can save an estimated 1% to 5%
- Set standards regarding combustion settings, boiler maintenance and inspection, and regularly inspect and maintain the boiler. Keep records of all inspections.
- Add Insulation. Heat loss is almost always a concern with boilers, which causes them to lose thermal efficiency. Line the pipes with fiberglass insulation including all valves and traps to lock in heat and boost thermal efficiency.
Further, if boiler feedwater quality is poor, blowdown water and carryover levels can increase, leading to a drop in boiler efficiency. Local feedwater quality regulations typically specify maximum levels of various elements, so refer to these when carrying out inspections.
Conclusion
Talk to the experts.
Steam boilers are large complex pieces of equipment, and the experts will be able to put you on the right track. There are a number of ways which savings can be made, from small to large amounts depending on your facility and boiler.
