Newbie drying question

[lawyer_sawyer]

Is there a best type of drying?

going through this board I have seen several different types of drying and am getting a little confused.  ???

After reading this section of the forum I have come up with 4 different types of drying.  If I have read this right of course 

* Air drying
   * outside
   * inside
* Solar Kiln
* Dehumidification Kiln
* Vac Kiln

these are at least the types of drying I have seen discussed regularly on this board.
More questions and confusions are:
* Are any of those I have listed duplicated.  Is a solar kiln just a different type of kiln that is just utilizing solar power?
* Are any of those listed usually used for a specific application.  Is one types used when making lumber or boards for interior finished uses where another is just to make lumber for rough construction.
* Are there any limitations on what a specific type of kiln can do.  (i.e. size of load, thickness of woods, moisture content)
* apart from the solar kiln which is the next cheapest to run if you were going to do production
*are some better for hardwoods and some better for softwoods?


One final question.  If you were limited to having one kiln to meet all of your needs which would you all pick.

Thanks
and I will keep trying to find all the posts already on this.

[Ga_Boy]

You are on the right track.

Here are the types of kilns:

Conventional
DH
Vac
Solar

There are a few others that are hybrids such as RF/Vac and microwave but these are commercial units that produce millions of BF per year.  So I will exclude these unless you are ready to invest a million or so in your operation.

Air drying is most commonly done outside, now there are hybrids of this as well.  You can simply sticker your material outside and let nature take its course.  It is best to cover the stack with plywood to prevent damage.  If you move the material under a roof this can be referred to as shed drying.  In a drying shead some incorporate controls to regulate the MC loss perday so that the predefined rates are not exceeded. 

There are several books you should read "Drying Hardwood Lumber" and "Kiln Operators Manual"  Both are PDF's that can be down loaded. 

As for which is best, the answer to that lies in how much coin you want to invest and what your market is.  I would say the most popular type on the FF is the DH units.  As for me, until I attended a Kiln Operators course I was programed to buy a DH unit.  After the course I built a conventional kiln.

Read this and kick it around then ask more questions.

[scsmith42]

Counselor, you've posed some great questions, but the answers will vary depending upon a lot of factors.

Can you tell us your business application?  This would help others to give the best advice.  For instance, drying 8/4 pine for a high volume commrecial lumber may yield a recommendaiton for a conventional kiln, versus drying lower volume 4/4 oak for local sales may yield a recommendation for a DH kiln.

Thx.  Scott

PS:  Good luck preparing for, and taking your Bar exam!

[oakiemac]

I'd be curious why Mark (Ga boy) went with a conventional?? ???

the limitations on the kilns all depend on the size that you buy. I have a small DH unit that holds 1000bf and a larger unit that holds 3000bf. I believe (could  be wrong) that the DH units are easier to run and maintain and less chances of screwing things up also less chances of getting case hardening and getting stress in the lumber.
I'm sure Den and Don Lewis will pipe up. They both know quite a bit and are much more of an expert then I am.

Solar kilns are designed to use the sun to heat but are much slower then other kilns.
Vacuum kilns are very fast but require more capital investment up front and are more maintenance intensive.
Conventional kilns?? I won't comment because i'm not too familar with them. I beleive that they are much more energy intensive then the DH.

[crtreedude]

Solar kilns might actually be more effective here - or some mix. The angle of the plastic "receptor" up there would have to be 45 degrees - down here it would be 10.

According to my reading, the tropics is one place where solar kilns are used commercially. I know of an opperation with more than 100,000 BF capacity of solar kilns.

[Larry]

The big boys in the Midwest all run conventional steam kilns...lot of em over 100,000 board foot capacity.  Fuel is wood waste.  Electric Al is one of a few with a small conventional kiln.

One of the mills I'm familiar with had a huge, ever growing sawdust mountain when they were running two circle saws.  Never ran out of fuel for the kiln.  They only use the circle saws now for head rigs feeding a grade re-saw.  There sawdust mountain has shrank to a mole hill and they have to buy fuel now.  Don't know if that is economical or not.

My thoughts...solar is cheap but very slow.  DH is expensive to operate and not really fast either.  Vacuum and conventional have high start up costs.  Vacuum has advantages with thick stock.  DH is pretty simple to operate and doesn't require a lot of attention.

I have a solar kiln and a DH kiln.  Think I'll always have a solar kiln.  Would like to buy a new Nyle DH.  Wouldn't mind building a small wood fired conventional kiln either...but laws on burning are becoming more and more restrictive.

[Ga_Boy]

Steve,


I selected a conventional unit over a DH because I could use my wood waste as fuel to fire the kiln.

I also use the heat from my wood waste to heat my shop and house.  I was a little more in start up cost but the risks were minimal.  Also when I need to open a second kiln I still have the capaicty on my furnance to fire the second kiln.

With a conventional unit I can take material green from the saw and put it right into the kiln.




Mark

[lawyer_sawyer]

Thank you for the responses so far.

to clarify the application aspect.....I don't know!!!
I have been working on a business plan with parts of spread sheets here and there and this was a part that I have been working on in my spare time trying to learn about.  I just got lost in the information.

I like the idea of a conventional kiln being able to be run off of an outdoor boiler.  This source of heat is something I plan to have when I do find that place to start a business...which is still sadly in the planning stages.

But to try and identify application.  I would have to say that I would like to be able to do up to 3000 bf.  either for my own personal building uses or for resale.  I would also like to have the option to load right from a saw and not take more than a month with a full load.  of course if that would require more than one that is always an option as well in the long run though, I guess.

Not really having a market I wish I could say I am going to be cutting mostly x/4 but I can't.  rather I can say I would likely be cutting a multitude of widths and thicknesses and so would probably need a kiln that is flexible enough that i could do different thicknesses if that is possible.  not sure it is. 

I haven't found any links in the search and maybe I am not narrow enough on my searches that explain how each works and how each overcomes the degrade question.

kinda an aside question but is there one that gets hotter than others during the drying process?

again thanks for the answers so far.
Jake
LS

[scsmith42]

Jake, based upon your information I would narrow your quest down to either a DH or solar kiln.  The CapEx for a vacume or conventional would probably be too high, and keeping the conventional kiln "fed" with waste wood would occupy a lot of time versus the operational ease of the solar or DH.

I would suggest that you start by looking into the solar option.  Albeit slower than DH, it has the benefit of a very low OpEx and CapEx similar to DH.  If you build it with some forethought, you can always convert it to DH in the future.

The size of your load is sometimes proportional to the drying rate of the species.  For instance, SYP is a group 1 softwood and can withstand a drying rate that is approximately 4X faster than similarily dimensioned red oak.  Consequently, a Nyle 200 kiln may be able to dry 3K bd ft of red oak in a load, but only 1K of pine due to the more aggressive drying rate.  However, the 3K of oak will take 60 - 90 days to dry, versus 25 or so for the pine, so in reality your annual production volume is the same.

DH has the advantage of being able to rise the temperature enough to "set the pitch" and sterilize the load (24 hours at 160 degree F); but I don't think that you can achieve the same thing with solar.

Re thicknesses, the thicker the wood, you ahve to dry it exponentially slower. I.e., 8/4 does not dry twice as slow as 4/4, it's more like 2.7 times slower if you're going to maintain the quality.

Also, because the drying rate is dependant upon species and thickness, your loads need to be compiled accordingly.  In a perfect world, you would run a load through of all 4/4 pine, the next load may be 8/4 pine, the next one 4/4 oak, etc.  It is generally not a good practice to mix 4/4 and 8/4 or 12/4 lumber in the same load, as you risk damaging the thicker lumber if you dry to fast.

If you're looking to start this business as a potential augment to a law practice, I would suggest that you start small and create a business plan around what you can accomplish on weekends, as your law weekdays are typically 12 hours or more.  Over time, if the wood business is financially and emotionally satisfying,  you can expand as the opportunity and demand arises.

There are many users on FF that are vastly more experienced than I, and they may chime in with different recommendations, so good luck sifting through all of the feedback!

Good luck. Scott

[Don_Lewis]

There is no best type of drying.

All drying approaches work but some are better suited to an operation than others. For some, the idea of saving a penny or two a board foot in energy costs is well worth them spending a few hours a week extra. That is a matter of personal preference sort of like the idea that some will spend a lot of time making sure their operation is neat and attractive while others could care less, or some like to drive a vehicle that is shiny and fully tricked out and others will not care one way or the other what their truck looks like. People can produce great lumber either way.  This is a business that allows people to do their own thing and make a living, providing you turn out a good product.

Don't get too hung up on the machinery. Think about log supply, markets, how you plan to go to market, what you think has a market opportunity etc. Then think about the machinery that will allow you to meet that need in the way that suits the market, your lifestyle and your future plans.

Good luck

[oakiemac]

You can use waste wood heat on a DH also. Just you wouldnt reap the benefits as much with a conventional type.

[lawyer_sawyer]

Thanks everybody for your answers to this
sorry I haven't been on for awhile but it has definitely given me more to think about at least when it comes to defining what I will need in regards to what I hope to achieve.

thanks again
Jake
LS