Table of Contents

1		Introduction
2		Is it for me?
3		How much does it cost?
4		What are the benefits?
5		Step by step guide
6		Case studies
7		Where Can I find out more?

Step by step guide

1. Do not waste energy
2. Observe the color of the fumes coming out the chimney. If they are dark, the boiler is emitting fuel instead of burning it. This can be due to a shortage, poor distribution of the combustion air, or to insufficient atomisation of the fuel.
3. You can easily avoid unburned fuel. For liquid fuels, adjust and clean the burners to obtain an adequate atomisation. Control the viscosity of the fuel, preheating it if you need to reduce it (very common with fuel-oil). For gas fuels, correctly adjusting the burners should be enough to obtain better performance.
4. Pale fumes do not guarantee correct operation. It could be an excess of air, that also implies a cost because too much heat is coming out the chimney, instead of being used for heating.
5. If the combustion gases leaving the boiler have a temperature higher than 230°C, you should consider using these gases to preheat the water or the air for combustion. The payback period for the required equipment is only 1 or 2 years and the savings obtained can be very significant.
6. The recovered heat could be used for different equipment. For instance, it could be used for drying processes.

How can you make use of the energy of the hot gases?

If the combustion gases go out with a temperature higher than 230°C, you should consider using them to increase the efficiency of the boiler.

Combustion air preheating: air preheaters are special gas-air heat exchangers.

• Gases cannot be cooled below 150-175°C, because of the corrosion effects that could take place due to sulphuric acid condensation. Fuels with low sulphur content, such as natural gas or LPG, do not have this problem.
• There is a huge variety of economisers and preheaters. Consult a specialist to determine the most appropriate one for each case, taking into account the potential savings and the maintenance required.
• Check for any heat losses

In addition to the heat losses through the chimney, there are always other losses that should be minimised, such as the losses through walls and drain valves.

• To reduce energy losses through walls, fire resistand and surface insulating materials should be checked, by increasing their thickness or replacing them with better alternative materials. This will avoid energy looses, accidents and uncontrolled gases due to the sealing effect.
• Losses in drain valves can be reduced by rationalising the amount of them, improving the quality of the feeding water and recovering its sensible heat.
• Use fuel efficiently
• Heat transfer surfaces (pipes) must be kept clean in order to maximise fuel use.
• Consult a service technician. He can help you identify improvement measures to increase the efficiency of your equipment.
• You could also learn to control the boiler operation yourself. Commercial flue-gas analysers can help you saving fuel. The cost of such analysers is similar to fuel costs for a 1MW boiler operating for 40 hours.
• Check the possibility of changing your fuel to a more advantageous one or one from cheaper sources (wastes, biomass etc)
• Reviewing the system and mantaining it in a good state will save money. Drain the circuits to get rid of air, check pumps and fans, and test the adjustment of control systems. Where possible, use automatic controls. All this advice could help you save more than you might think.
• Take always into account that boilers working at partial load have a much lower efficiency. This is why installing several small boilers instead of one big one should be considered. In this way, the number of working boilers (all of them at maximum efficiency) can be chosen according to demand. This breaking-up of power is a very common technique used for boilers with powers of 300kW and above.
• If there are several boilers, it is highly recommended that the most efficient ones work all the time in steady state conditions, while the less eficcient ones are used to absorb the heat demand changes.
• Fluid transport also consumes energy

Every boiler needs additional equipment for fuel transportation (pumps, fans, compressors etc), which are usually large electricity consumers. Energy saving measures tehrefore also be applied to them.

Check the design

• Shorten pipe lengths as much as possible.
• Avoid sudden narrowing or widening, unnecessary bends and derivations.
• Choose circular sections - although they are a little bit more expensive.
• Select pipes with the maximum suitable diameter and the minimum internal roughness.
• Install valves with low load losses.
• For dense liquids, pump them slightly warmed.
• Keep your installation in good order to avoid depositions.
• Regulate the flow with variable speed motors rather than with flow restrictors.
• If the efficiency is low, replace the boiler with a high efficient one.

High efficient boilers (low temperature or condensation) can lead to 10-20% fuel savings, especially working at partial loads.