[Gasification] Urfi's 6 ton/hr steam boiler - was: Re: Gasification Digest, Vol 8, Issue 35

[Daniel Chisholm]

On Wed, 2007-07-03 at 02:03 -0800, urfi mustafa wrote:
> Hi
> Can I replace a 6ton steam generating boiler running
> on oil with a pellet/briquette gasifier.
> Thanks
> Urfi

Hello Urfi,

By 6 ton I presume you mean 6 tons of steam per hour, i.e. roughly 12
million BTU/hour?  Do you have an idea of what sort of price you could
get pellets or briquettes for in your area, and how that would compare
to your oil prices?  This will determine what (if any) your hourly
energy savings would be, which would help decide how much you can afford
to spend to burn a cheaper fuel (capital, operating, maintenance).

Here in New Brunswick, we pay about CAD 70 cents per litre for #2 fuel
oil, which is about $19CAD per million BTU.  Wood pellets are remarkably
expensive (in my opinion) at about $250 per tonne, which is about $14.50
per million.  Unprocessed wood biomass ranges from $25 per tonne for
bark/hog-fuel to about $40 per tonne for chipped whole trees (from
species not suitable for hardwood or softwood pulp), which gives a range
of $2.50-$4.00 per million BTU for 50%-60%mc raw fuel.  I am not aware
of a local source or price for wood briquettes, but their price must
fall somewhere between that of their raw feed material and the
higher-processed wood pellets.  For the sake of argument, allow me to
assign a SWAG figure of $8 per million.  Number 6 heavy fuel oil (Bunker
C) is about $9.25CAD per million.  Natural Gas is about $13-$16 per
million.

In table form, using NB prices, here is the hourly fuel cost for a 12
MMBTU/hour boiler, using efficiency numbers I am guessing at (the
boiler's efficiency for the various fuels will depend on the usual
things such as its exhaust gas temperature, fuel moisture content, etc).


Fuel              $/mmBTU  boiler effic.    hourly fuel cost 12mmBTU/hr boiler
--------------------------------------------------------------------
bark 55%mc          2.50       65%            $46
chips 55%mc         4.00       65%            $74
briquettes 5%mc     8.00       75%           $128
#6 oil              9.25       85%           $131
pellets 5%mc       14.50       75%           $232
natural gas        14.50       88%           $197
#2 oil             19.00       85%           $268


As you can see, the economics of burning biomass depends on a great
extent to the cost of the competing traditional fuel.  If you are
replacing very-expensive #2 fuel oil, your fuel savings give you a lot
more money to spend on installing the capability to burn a cheaper fuel,
and eventually save money.

But if your oil is #6, it is actually *more expensive* (using NB prices)
to burn pellets or briquettes.

Biomass in its raw form is much, much cheaper, however the plant to burn
it is larger, more expensive and more troublesome/labour-intensive (you
must pick at least two of the preceding adjectives!).  But at least
there is the _potential_ for savings there, that is enough to at least
justify some spreadsheet work to see if a project makes sense.






-- 
- Daniel
Fredericton, NB  Canada