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Currently from what I've read ethanol is roughly equivalent to burning natural gas to produce charcoal from wood.

If anyone is interested I can post several studies.


Judging from the wealth of data produced, it can safely be said that EtOH is either net energy neutral, net energy positive, or net energy negative.  Pick the dataganda that fits your needs.

i.e. : Lies, damned lies, and statistics.

The indisputable fact is that EtOH is currently net economically negative, and government subsidization of the corn crop first and EtOH production second is the only thing making it financially feasible.  

Ostensibly the reason is to foster EtOH production to get money into R&D for the cellulosic process that should be both energy and economically net positive.

However, how often does the government kill a subsidy?


Hmm... I'd be interested if anyone knows of any plants burning fuel ethanol in the boilers of their ethanol plants!:)

I think we all have to understand that Fuel Ethanol is all about having an alternative at any price.  Just because gas and oil are better options today, doesn't mean that they will be tomorrow.  Oh.. hang on, we could import from Brazil 51c cheaper :)


Interesting you ask that.  None of the plants that I worked on burnt ethanol in their boilers.  They had burners capable of using natural gas or number 2 fuel oil.


That was fairly tongue in cheek, but it does say something about the cost of those energy sources.  I have seen very attractive pricing for contracting energy supply to on-site wood chip gasification plants.

jistre - Are you in EtOH operations or design?


I helped on a couple of EtOH in the eighties and the US Gov't would only give the incentives if we fired the boilers with coal.  Try starting up a coal fired boiler in Iowa in the dead of winter (to get the tax write-offs by the close of the calender year)


Well ethanol was in my last project, but I was involved in plant design on various stages of a 100MMGPY, and a 50MMGPY project.


And if one were to fire with enthanol, you'd still have to have an alternative start-up fuel to boot up the process.

And speaking of wood chips, I was also involved in a waste wood pelletizing plant (the fuel from which went to help fire a coal-fired central heating system) that came pretty close to making economic sense.  The wood raw material was a true pesky waste that had to be disposed of in some manner. The pelletizing plant added enough value to make hauling the fuel to a boiler able to burn it, marginally worthwhile, and actually environmentally green.


I've recently been working on utilities and mechanical services for a couple of plants, one wet mill and one dry.  

There doesn't seem to be a lot of information out there for designing the utilities - useful stuff such as load profiles for boilers and chillers.  Given that the core technology is usually from mash prep to DDE, it is surprising that the information seems so hard to get.


Well, all I can say about information is that our client was VERY touchy about releasing any information about any part of its process, even to us at some points.

I have to think it's because fermentation and distillation are such well known processes that these companies are terrified to give out any information lest their own special twist on making moonshine leaks out.


Need to query the really old guys living in the Appalachians (N.Ga, the Carolina's) they may not know much about boilers but I bet they know their mash.  Their offspring moved on to pot cause it's less work.

I recollect we flew a brewmeister over from Europe to help get our fermentation going in the dead of winter.



You state: "There doesn't seem to be a lot of information out there for designing the utilities - useful stuff such as load profiles for boilers and chillers"

Uuuummmmmm... mass and energy balances developed from flowsheets.... Chemical Engineering 101..???

You gets yer load then you buys yer boiler....

What am I missing here ??




I can see where KiwiMace is coming from.

The process flow on the fermentation side of these plants can be extremely complicated.  As you're dealing with biologicals, until you get to DD&E, you have to be prepared to do anything at any time with the live cultures to keep the bugs going.  Heat them, cool them, feed them, stir them, burp them, move them forward in the process, return them to an earlier point in the process, read to them... they are delicate and FINICKY. On top of that, you throw in batch/continuous process parameters and your actual utility load needs in fermentation can end up being very hard to nail down.  

Once you get to distillation, then the operation of the plant becomes more of a typical chemical plant running as a relatively unchanging continuous process, but before you get to that point, the flow of material and energy through fermentation can be a nightmare to untangle.


Yeah, it's not a difficult matter to find a peak load and throw a chiller at it that matches...  

If you know the load profile under a range of operating conditions, such as winter start ups and hot summer days, then you can specify an efficient turndown and consider other, more cost effective, strategies to meet the total requirement of the system.

Having only a peak load severely limits the possible solutions.



If you are unsure of the peak laod, design a multi-boiler/multi chiller installation with a mind to turn down and unit efficiencies at partial load.

Over time, 95% of the cost of the utility is energy (natural gas or power) not the capital investment of the equipment. Two units, each rated at 75% of the peak can work.

Another option to consider (even at the prelimnary deisgn stage) is to allow space and interconnecting piping for a temporary (rental) boiler and/or chiller.





Yes, which is the standard approach when operating blind.  What I am trying to establish is the best solution, not a versatile solution.


It's definitely the sort of thing that experience on one plant could help you to refine the design of the second plant.

However, a lot of these operators and process design firms are very protective of their designs and won't give out any information regarding their plants. If you've got several in a row coming up, you might be able to optimize the design through the successive plants and perhaps come up with some retrofits for the first designs by the time you reach the end, but as for getting any information about existing plants from other sources, that might be a bit rough to accomplish.


I saw the question above:
>Hmm... I'd be interested if anyone knows of any plants burning fuel ethanol in the boilers of their ethanol plants!:)

and had to post the following piece from the air permit of a Kentucky bourbon distillery:
-----------begin snip-------------
Emissions Unit 08 (09-001) Indirect Heat Exchanger
Horizontally-opposed-natural gas-fired indirect heat exchanger
Secondary fuel: Distillate oil (#2 and #4 fuel oil)
Tertiary fuel: Off spec alcohol
Maximum continuous rating: 176 MMBtu/hr
Construction commenced: 1972
-----------end snip--------------

It is being done


KiwiMace's question above (3rd post) is profound.  We'll know when these biofuel plants make sense, from an energy balance viewpoint, when they are burning their own product at some stage in the processing as their own preferred fuel. I probably won't live to see it.    


It's my belief that the ethanol isn't used as fuel in the boilers mainly because it's more economical for the plant to buy fuel and sell the ethanol than it is for them to just use the ethanol.

However, as of recently, I bet that the economic benefits are disappearing, and the energy balance questions become more important.


When the biofuels become inherently (relatively) cheap, they will fuel the process because they are already at the producing site, just like oil refineries now consume some of their process fluids to fuel the process (as opposed to, say, importing intrinsically cheaper coal to fire the process).

Perhaps then the economic distortion caused by government intervention can be appreciated.

Not to mention the environmental disaster fuel EtOH from corn is rapidly becoming.   


I did mention that the question was tongue in cheek...  

The obvious answer is that we have to get our energy sources into a form in which it can be used in it's intended purpose.  

Natural gas is a wonderful energy source (while we have it) but it suffers from low volumetric efficiency, and it can't be added to liquid petroleum based fuels to reduce pinking.

Whether we should be driving injected NG cars might be cause for another forum.


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