How Efficient is an old-style coal-fired steam boiler?

[Xodion]

I've been looking around for any hint of this kind of thing, for a story I'm planning to write, and while I can ignore discrepencies between, say, actual history and events in my story, my inner scientist won't let me ignore this!

The situation is as follows; imagine an early industrial revolution era steam boiler, like the ones used in early steam locomotives, burning coal found on and near the surface of the ground (lignite, sub-bituminious, not quite sure on that either). I can find the energy values of coal, and efficiencies of modern steam boilers, but nothing about old ones, so I would like to know is:

1. How much of the energy from the coal would actually reach the steam as useful kinetic energy?

2. How quickly do the boilers go through coal, and how much would they need to keep it burning for an hour without getting too hot or too cold?

These are complex questions, I know, which is why I need help with them!

 

[Bob S]

Hi Xodian-
Conventional coal fired utilities are about 10,000 BTU per kilowatt-hour output (about 32% efficiency). Some modern ones may be as low as 8,000 Btu per kilowatt-hour output. The major limit to maximum efficiency is thermodynamic; Carnot (Rankine) cycle. See
http://en.wikipedia.org/wiki/Rankine_cycle
Bob S

 

[sir-pinski]

It is difficult to give a definitive answer to these questions as there are many factors that can affect the efficiency of an old-style coal-fired steam boiler. However, there are a few key points to consider.

Firstly, the efficiency of a steam boiler is determined by the amount of heat energy that is converted into mechanical energy, which in turn produces steam. This is known as the thermal efficiency and is typically expressed as a percentage. In general, older steam boilers had lower thermal efficiencies compared to modern ones due to advancements in technology and design.

Secondly, the type of coal being used can also greatly impact the efficiency of the boiler. As you mentioned, lignite and sub-bituminous coal are lower quality coals and therefore may not produce as much heat energy compared to higher quality coals like anthracite. This means that more coal would need to be burned to produce the same amount of steam, resulting in lower efficiency.

Furthermore, the design and maintenance of the boiler can also play a significant role in its efficiency. For example, if the boiler is not properly insulated, a significant amount of heat energy may be lost through the walls and pipes, reducing the overall efficiency.

To answer your first question, it is difficult to determine the exact amount of energy that would reach the steam as useful kinetic energy without knowing the specific design and condition of the boiler. However, in general, the thermal efficiency of an old-style coal-fired steam boiler would likely be around 50-60%.

Regarding your second question, the rate at which the boiler goes through coal and how much is needed to keep it burning for an hour would depend on the size and design of the boiler, as well as the quality of the coal. However, it is safe to say that these boilers would require a significant amount of coal to produce steam for an hour, as they were not as efficient as modern boilers.

In conclusion, an old-style coal-fired steam boiler would likely have a lower thermal efficiency compared to modern boilers. It would also require a significant amount of coal to produce steam for an hour, and this amount would vary depending on the specific design and condition of the boiler. Keep in mind that these are generalizations, and the efficiency of a particular boiler would need to be evaluated based on its individual characteristics.