(4) Improving boiler efficiency

The operating mechanism of boiler combustion cycles, such as the purge period and the control method (timer or mechanical control), varies according to the boiler manufacturer. However, making drastic changes to this mechanism is almost impossible.This is because the mechanism is related to safety.
[Fig.1] shows the operation status of a boiler introduced in the previous lecture.

The purge ratio in this condition was 59%. To increase the thermal efficiency of the boiler by improving the 41% (100 - 59) combustion ratio, it is necessary to generate the desired amount of steam by decreasing the number of ignitions.This can be achieved by limiting the combustible time period.
Since the boiler in this plant heats up an aqueous solution such as that for a plating bath, a decrease of the bath temperature is not likely to occur owing to this extremely high specific heat. By considering this factor, we operated the boiler by limiting the boiler combustion time to 15 minutes in every hour. [Fig.2] shows the operation results of this experiment.We installed a timer on the boiler control panel to limit the combustible time period to 15 minutes per hour.

Surprisingly, the fuel consumption has drastically dropped to one-third of that for conventional use.As proven in this example, using the boiler as intended by the manufacturer may not be the best way when it comes to the heat-saving measures. Some companies thoroughly consider the characteristics of their own plants and take advantage of these characteristics to save heat efficiently.