Solid Fired Furnace - Process Heater??

[ryan1975]

Anyone have any experiece/references/thoughts on process heating with a solid fuel - coal, solid waste (bagasse - sugarcane waste).

I am a Chem Eng and not a furnace expert but in a recent discussion with two furnce experts was told that process heating with solid fuels would be extremely difficult and not a standard application (generally only used for boilers).

I know that boilers that are solid fueled are well established. Can anyone enlighten me on solid fuel process heaters.

Thanks,
Ryan

 

[mbeychok]

ryan1975:

From the technology viewpoint, process heaters could certainly use solid fuels like coal or bagasse. However, from the environmental viewpoint, it would probably be much, too much expensive. For example, in the USA, UK, Canada and other countries, you would have to meet very stringent air pollution regulations and solid waste disposal regulations.

Large power plants include furnace bottom ash handling and disposal equipment. They also include electrostatic precipitators for fly ash removal from the furnace flue gases ... as well as flue gas desulfurization scrubbers. And then there regulations limiting the discharge of nitrogen oxides and mercury (in the flue gases) that require more capital expenditure.

The cost of all that equipment would certainly make the use of furnaces burning solid fuel for process heaters uneconomical ... especially so if oil or natural gas is available.

Milton Beychok
(Visit me at www.air-dispersion.com)
.

 

[ryan1975]

Thanks very much for the input Milton.

Do you happen to have any examples of process heaters using either coal or bagasse (most intersested in bagasse)? Or know of companies that deal in this technology.

Are environmental regulations for a process heater more stringent then a boiler?

Thanks again,
Ryan

 

[dcasto]

I'd go with a steam generator and use steam as the heat transfer medium. This also gives the ability to have mutiple boilers that could burn other fuels.

If you insist on direct fired, the cotrols woulb be complex, a heater by-pass system for temperature controls with maybe a air cooler in case of to m uch excess heat from the heater and a minimum flow through the heater.

Google biomass boilers

 

[rmw]

Google the words "Konus-Kessel", follow the links and enjoy some reading on topics that you are asking about.

I have had experience with their thremal oil heater fired by waste wood. It was a good product.

rmw

 

[ryan1975]

dcastro - the difficulty of control is exactly the key concern we were disucssing (also problems with avoiding hot spots on the tube wall). Thanks for the input.

rmw - I looked at the Konus-Kessel link - interesting. A hot oil heater is another option we are considering - likely DowthermA for our temp requirements. In your experience firing with waste-wood what was your firing efficiency. Did you have concerns limiting tube wall temps with waste wood fuel?

Thanks,
ryan

 

[djack77494]

In the paper & pulp industry, black liquor, which is best described as a slurry, is fired into a furnace as a fuel.

 

[rmw]

Ryan,

The unit was fired two ways. One was with an indirect furnace separated from the oil heater tube banks and that didn't work. The furnace was then built immediately below the coiled tube section with the upper furnace wall beng like a center tube fire tubed boiler stood on its end. The gas path was up then down and back up through three concentric rings of oil piping. That was the original design and it worked the best. The add on furnace was a disaster. Wall temperature never was a problem. The radiant heat transfer ended up being more important than previously thought.


If we even figured firing efficiency I don't remember it. We weren't as concerned with efficiency as we were with burning up all the waste wood generated in the plant through the debarking operation as well as the trimmers flaker waste, etc. It was an OSB plant.

The oil circulation was maintained at a predetermined point through the furnace loop which guaranteed a minimum tube velocity. The oil to process was blended with furnace loop oil.

rmw

 

[NCCaryME]

Hi rmw, just curious if you could tell me which OSB mill this was?