Gas fired vs. electric calciners -- which is better?

[Bill3142]

Does anyone have any experience with electric calciners in the 24" diameter range vs gas fired? The problem with gas fired is that there are so many controls, balancing valves and burner parts, something is always not working or out of tune. It seems to me that an electric calciner has "one dial" to turn temperature up or down and greatly simplifies control. I would expect far fewer maintenance issues and significantly greater control with electric. I realize the heating elements go bad and the connections tend to wear out, but that could be managed by overhauling the calciner every few years. The other thing that people make a big deal about is fuel cost. My understanding is that gas is 35-40% efficient and electric about 70% efficient. For a 24" calciner, that works out to about ~$40k/year more for electric. Not really a big deal in the scheme of things, and can be far outweighed by costs of downtime, maintenance and product quality associated with gas.

 

[moltenmetal]

What temperature is this calciner operating at?

The thermal efficiency of a piece of gas fired equipment operating at high temperature is greatly determined by what other uses you may or may not have for the hot flue gas exiting the hot part of the unit. Combustion air preheat is only part of the duty. If you have nothing else to use that hot flue gas for, the efficiency can be very poor indeed.

Electric, on the other hand, is 100% efficient at generating heat at any temperature you need. The only efficiency loss you have with an electric unit is if you use an intermediate medium (air, steam etc.) to transfer the heat to the thing you're heating. But of course, electricity isn't heat- it's basically thermodynamic work on tap. It can only be produced from heat with a substantial loss.

For small duties we always prefer electric for the practical reasons you've stated.

 

[Bill3142]

Moltenmetal, thank you for your response. Where is your breakpoint for small duty? We have a 12" rotary electric calciner and that makes sense. Seems to me that the additional fuel cost to run a 24-30" electric calciner is more than offset by improved runtime. Our temps are typically 500-1000C.