Boilers are used in a range of manufacturing industries, as well as oil and gas, to provide heat to an industrial process via the transfer of water. Instead of discharging flue gases/vapour from a boiler directly, efficiency can be improved by passing the gases through a heat exchanger, called an economiser.
The gases can then be used to heat feedwater prior to being pumped to the boiler, saving fuel to raise steam and improving thermal efficiency of the boiler. Economisers can also be used for liquid feeds into chemical reactors.
Sectors and common applications
- Manufacturing, oil and gas − with heat exhaust processes including tube boilers, with vertical stacks or horizontal gas flows as well as condensers.
- Estimated energy savings in 2014 across sectors was 14 PJ/pa.
|No.1. Energy saving potential|
|1.1 Level of energy efficiency||13.5/15|
|1.2 Market prospect||2/10|
|1.3 Energy saving potential||5/10|
|2. Technical practicality|
|2.1 Innovative or advanced nature||15/25|
|3. Economic characteristics|
|3.1 Investment per unit energy||8/10|
|3.2 Payback period||6/10|
|3.3 % of Industry $ gross added value||5/5|
|4. Social characteristics||3/5|
Mackay Sugar Ltd planned a boiler economiser replacement. The benefits to the company will be improvements to the heat recovery of the combustion process and hence reduce fuel consumption. The current economiser on the No. 1 boiler is in poor condition and has led to a number of tube leaks. The reliability of the unit deteriorated to the point that it was unused in the previous crushing season.
The direct result of this was a 28 per cent reduction in steaming capacity of the boiler and an increase in the rate of bagasse consumed in the boiler. Replacement of the economiser is expected to cost $1.2 million and will bring greater boiler efficiency and increased export of electricity from the site. The overall payback of the project is expected to be 1.4 years.
The crushing capacity of MSF Sugar Ltd’s Tableland Mill is limited by the boiler capacity and the boiler furnace volume. Installation of a boiler economiser would increase the potential boiler efficiency from 58 to 65 per cent without the need to upgrade the induced draft fan. The boiler steam rate could be increased by 10 per cent whilst maintaining the same bagasse firing rate.
Other companies that have identified boiler economisers as a source of energy savings include:
For more information, see: