Boiler Economizers

The Boiler Efficiency Calculator allows you to calculate the energy efficiency benefits of adding one type of economizer to a boiler system. Economizers are heat exchangers that transfer the heat in the flue gas to another medium‚ generally the boiler feed-water‚ although other streams are sometimes used such as make-up water. There are 2 types of economizers: non-condensing and condensing.

Non-condensing economizers

The most common are non-condensing economizers. They are heat exchanger coils‚ usually finned‚ that are located in the flue gas ducting at the exit of the boiler. Typically‚ a non-condensing economizer will raise the overall efficiency by 2% to 4%. They are designed and operate to maintain the flue gas temperature above the flue gas condensing temperature to prevent corrosion of the flue gas ducting. This is particularly important for fuels containing sulphur‚ as sulphurous compounds will form in the flue gas that will both raise the overall flue gas dewpoint and when condensation occurs will lead to the formation of sulphuric acid‚ which is highly corrosive.

Condensing economizers

Condensing economizers are designed to accommodate the corrosive fluids generated when condensing the moisture out of the flue gas. There are 2 types of condensing economizers: heat exchanger and direct contact (spray). They capture much more heat and therefore can raise the overall boiler efficiency by 10% to 15%. For condensing economizers to be the most effective‚ low temperature heat sinks are required to bring the flue gas temperature well below the flue gas condensing temperature.

The calculations to determine the efficiency of condensing economizers are complex and are not included in this version of the Boiler Efficiency Calculator.