Kiln Drying Forum

Wood Drying Topics => General Discussion => Topic started by: Brooklyn on June 05, 2014, 07:12:39 AM

Title: Request Input on possible Kiln Purchase
Post by: Brooklyn on June 05, 2014, 07:12:39 AM
Hello all,

I work at a reclaimed lumber company and recently we have been trying to expand our interests and consequently, our processing capabilities. We had an original interest in acquiring a kiln for drying our reclaimed lumber in order to stabilize it (lower MC, Kill infestations etc) but during research we also stumbled across thermally modified wood.

Is there a kiln that can be used to both dry and thermally modify wood using either the thermowood or plato process? I specify the process because these require only the addition of steam and heated air and can be used directly on green wood.
Is anyone aware of any small-scale (apx 2000-8000 bdft capacity), operational models within the United States?

We had already initiated conversation with a dealer from out of country before developing an interest in TMW and its processing. I would greatly appreciate insight from any individuals with more experience than I, in operating, utilizing or purchasing a kiln. 
Below are excerpts from a conversation with the salesman, her responses to my questions are in blue. I have also included an attachment describing the kiln's process and detailing the variety of kilns offered. Please use both to give honest insight and feel free to recommend other options. 

1. Can it be utilized in thermal modification of wood, such as the hydro-thermo plant in the following link?
Hydro-Thermo Plants (

I saw your website that is drum oven, and our machine is rectangular oven. You can find the picture of our dryer in attachment.
Our vacuum wood dryer is adopts high frequency heating and vacuum dewatering, it is can be used for drying furniture wood, the final moisture content will approx keep on 6%, and we can't be utilized in thermal modification of wood, if no water of wood, there is no toughness, so it can't be used for furniture. Could you tell me what are you use the thermal modification of wood to do?

We plan to thermally modify both green and reclaimed lumber for use in decking, siding, flooring, etc. We believe it is an emerging market.

Your plan is great. That is indeed a very good market.

1. I don't know about the thermally modify you said, But if you would like the timber for use in decking, siding, flooring, Our dryer is no problem.
Our dryer is high frequency generator heating principle and vacuum dewatering, It can be uniform heating and speedy drying without cracking, Square shape volume saving.

Vacuum drying can adopt low-temperature drying, can also be used in high temperature drying. Low temperature drying is the advantage of easy control of wood drying defects. But the low temperature drying can not effectively eliminate stress in wood, although the water content reached the requirements, but the wood itself, stress is not eliminated, the wood will still appear the phenomenon of deformation in the using process. After high temperature treatment of wood will eliminate the internal stress of wood, wood occurred during deformation phenomenon can be eliminated basically, should pay attention to this point when purchasing equipment.

2. How does the pricing of your dryer compare with others?

We are professional manufacturer of wood drying machine. We have a 3/4/6/8/10/12/15/20 cubic meters in diffferent size and different price.

3.Can you ensure that your high-speed drying technique is not damaging to the woods structural integrity?

High vacuum timber dryer adopts high frequency drying, inside and outside of wood timber is heated at same time, uniform heating, high speed drying, short time and good quality, which can keep the timber nature color, meanwhile, the timber is aerated under the vacuum environment, non-cracking, especially applied for the thick and hard precious wood, wet wood

4. Do you have any operational models of your kiln in the United States?

Sorry there are not operational models of our dryer in the United States at present. Our engineer have more than twenty years experience in domestic. Most of Furniture company is using our dryer for drying their timber with good results in domestic. And our overseas market, such as Uganda, Japan, New Zealand, Thailand, Vietnam, southeast Asia etc. They all have our equipment. The guest feedback use effect is very good. So our equipment is very popular both at home and abroad. If you want to know more clearly welcome you to our factory for visiting more live demonstration operation.

5.  You mentioned the cubic meter capacities, would you mind sending me the actual dimensions in (Length x Width x Height) format? Please also include the associated pricing for comparison.

 Pls kindly find the specifications of dryer details in attachment for your reference.

6. What is your voltage requirement for operation? 
About the voltage requirement, We can adjust the voltage according to your requirements in production

I still have not received any pricing information. Could you please include the base kiln cost for each product.

Also, given that you have no working models in the United States, do you have any experience transporting your product over long distances? What would be the cost of this transport?

You mention that the voltage requirements are adjustable, but they still must operate within a certain range to be able to power the kiln, what is the minimum and maximum operating requirement. We are not in an industrial park and run off of electricity so this information cannot be forsaken as it could become a major expenditure in the future.

(Awaiting a reply on these last questions)

I realize this is quite intensive and greatly appreciate anyone who is willing to take a stab at it.

Title: Re: Request Input on possible Kiln Purchase
Post by: PhilM on September 02, 2014, 06:42:38 AM
As I think you are discovering, there are more questions than answers when it comes to the thermal treatment process.  The fact that there may not be any of these systems in the US only makes your investigation that much more difficult. 

I have to admit I am not familiar with the process that these thermal treatment companies use, but I think it is a combination of heat and steam, perhaps above 1 atmosphere pressure which would require a treating cylinder.  Although I am not familiar with their particular process, years ago I did a study on the effects of heat on the strength and hygroscopic properties of wood at various moisture contents. 

Companies that sell either thermally treated wood or thermal treated wood processes claim a lot of benefits.  Some of these claims include decay resistance, moisture resistant, increased strength.  But I urge you and your boss to look at these claims with a good deal of objectivity.  Heat treated wood will indeed reduce the hygroscopicity of the wood which may improve the wood strength at a given equilibrium moisture content.  So, what I am suggesting goes something like this:  take two matched pieces of wood, one is heat treated while the other is not treated (our control piece).  If they both come to moisture equilibrium at the same relative humidity, the control sample may be at 10%MC while the treated sample might be at 8%MC (treatment has reduced the hygroscopicity of the treated wood).  Since dryer wood is stronger, if everything else were equal, the 8% piece would be slightly stiffer and stronger (but not a great deal more).  But, not everything else is equal because heat treatment at very high temperatures or for very long periods of time will degrade the wood cellulose resulting in lower strength directly attributable to the heat treatment. 

I have not visited your company so I do not know if you have any kilns or if you already have any steam source.  If I were building a small dry kiln (without thermal treatment) capabilities and did not have a steam supply, I would consider a small kiln that does not require steam to heat it.  This will reduce your capital expenditure (no boiler required) while making sure the market will support your sterilized and dry lumber.

My recommendation is for your company to focus on kilning the lumber, and leave the thermal treatment process consideration until later.  I suspect there will be a large difference in required capital between kiln and the thermal treatment, and hence the thermal treatment would represent a much larger risk.
Title: Re: Request Input on possible Kiln Purchase
Post by: MichaelM on September 02, 2014, 08:40:21 AM
Go here for more ThermoWood information than you can use.

Heat treatment is quite different from kiln drying.  The following is pasted from above source - - -

The ThermoWood process can divided into three main phases:
– Phase 1. Temperature increase and high temperature kilning
The kiln temperature is raised at a rapid speed using heat and steam to a
level of around 100ºC. Thereafter the temperature is increased steadily to
130ºC during which time the high temperature drying takes place and the
moisture content in the wood reduces to nearly zero.
– Phase 2. Intensive heat treatment
Once the high temperature kiln drying has taken place the temperature
inside the kiln is increased to a level between 185ºC and 230ºC, once the
target level has been reached the temperature remains constant for 2-3
hours depending on the end-use application.
– Phase 3. Cooling and moisture conditioning
The final stage is to lower the temperature down using water spray systems
and then once the temperature has reached 80-90ºC re-moisturising and
conditioning takes place to bring the wood moisture content to a useable
level over 4%.

I have to agree with Phil - unless this is in your business plan and you have a market for the product, it might be a good idea to stick to kiln drying.