What is an economizer and how does it improve boiler efficiency?

• A. A device that cools steam to condense moisture.
• B. A filter that removes minerals from feedwater.
• C. A safety device to relieve pressure.
• D. A heat exchanger that preheats feedwater using residual heat from flue gases, reducing fuel consumption.

Answer: (D)

An economizer is a heat exchanger that uses the remaining heat in the flue gases to preheat the boiler feedwater before it enters the boiler. By raising the feedwater temperature, less energy is needed to convert it into steam, so the boiler can produce the same steam with less fuel. This improves overall boiler efficiency, lowers fuel costs, and can reduce emissions because less fuel is burned for the same output. It also helps reduce thermal stress on the boiler by warming the feedwater gradually.

The other devices mentioned aren’t economizers: a device that cools steam to condense moisture is a condenser, a filter that removes minerals from feedwater is a water treatment filter, and a safety device to relieve pressure is a pressure relief valve.