[Gasification] Empirical data on dryer systems

Sat Dec 9 13:02:37 CST 2006

Hi Tom and list.

A rotary drum dryer does not have to be expensive. We built one from a 3ft 
by 20ft long pipe. We welded 6 inch flanges inside to move the material 
along, adding small baffles that would lift the material up to drop through 
the hot air. We found an old cement mixer and welded the mechanical drive 
from it on one end and used the steel rollers to turn the pipe on. Hot air 
and wet material was loaded in one end and dry material would come out the 
other. Moisture would also escape out the exit end.

Scrounge around like we did  for parts and your cost will be mostly your own 
labor
and since we all love what we do, almost free

John Flottvik

----- Original Message ----- 
From: "Tom Miles" <tmiles at trmiles.com>
To: <gasification at listserv.repp.org>
Sent: Saturday, December 09, 2006 10:46 AM
Subject: Re: [Gasification] Empirical data on dryer systems

> Erik,
>
> There is considerable experience in fuel drying among list members. It's
> just a topic that hasn't been discussed much. People on this list who are
> developing or providing small scale gasifiers for commercial use will
> probably show you a picture of their dryer but not discuss the details.
>
> I can design one for you. That's what I do for a living. We have designed,
> installed and fixed all kinds of fuel drying and processing systems since
> the 1970s. (See: www.trmiles.com  )We have built feeders and dryers for
> gasifiers and pyrolyzers from 250 g/hr to 40 tph. Just this week I was in
> Montana with the engineer for whom we built our first gasifier fuel system
> in 1976. Others on the list have similar experience.
>
> You will find there are a variety of small scale dryer solutions. At a
> hunting and fishing resort called Snowshoe in Northern Ontario the owner
> used to generate heat and power using an Imbert gasifier. He claimed that
> split cordwood simply dried in the extremely cold winter if he left it out
> long enough.
>
> For your application a batch bin dryer or a small continuous belt dryer
> would both be suitable. Small scale chip systems usually use batch dryers.
> Or they use continuous dryers based augers, woven belts, moving floors or
> vibrating conveyors with perforated plates. They are often custom built.
>
> Rotary drum dryers like the Barr-Rosin have been the most reliable for
> industrial systems. They are usually very expensive at the small scale. 
> Drum
> dryer design and operation has changed significantly over the years. A 
> major
> cost in drying these days is emission control so exhaust gas is 
> increasingly
> re-circulated and indirectly heated systems are used.
>
> Indirect and direct steam systems where exhaust vapor is recovered are
> thermally the most efficient systems. The most innovative dryers have been
> developed in Europe in recent years. These are very expensive for North
> America. You will find a few systems like the GEA/Niro Exergy dryers in
> Denmark and Sweden.
>
> Flash or suspension drying is most suited to finely divided materials that
> are handled in suspension. They are used for fiber drying and for peat or
> other finely divided feedstocks that will typically be used in suspension
> pyrolysis or gasification, or in fluidized beds. The morphology of fine
> materials permits rapid heating and short residence times which are the
> defining characteristics of flash drying. Some semi-mechancal flash drying
> systems are now being promoted. One of my clients has a system I think 
> would
> be very suited to easily milled fuels at a small scale.
>
> Reports are available for several small scale drying studies for biomass
> fuels that have been funded by the EU and in the US by US DOE and US
> Department of Agriculture. If you develop a bibliography of these we can 
> put
> it on the web.
>
> Fuel selection, preparation, handling, sizing, drying and feeding are all
> essential topics for gasification. A FUEL topic is something that is on 
> the
> list of things to add to the Gasification website but the site is only 
> being
> developed as time permits.
>
> There is information about dryers on the message archives and on the
> website.
>
> You will find some messages referring to fuel drying by using the (Google)
> search on the http://gasifiers.bioenergylist.org .
>
> The general site search utility has been temporarily disabled due to 
> server
> problems. We expect to put it back sometime next week.
>
> Regards,
>
> Tom Miles
>
> -----Original Message-----
> From: gasification-bounces at listserv.repp.org
> [mailto:gasification-bounces at listserv.repp.org] On Behalf Of Rodenhuis, 
> E.J.
> (Erik Jan, Student TBK)
> Sent: Saturday, December 09, 2006 2:25 AM
> To: gasification at listserv.repp.org
> Subject: Re: [Gasification] Empirical data on dryer systems
>
> Hey all!
>
> Is this topic not worth considering a thought? I hoped to get some get
> some ideas and figures about dryers. Couldn't find much discussion on
> this topic in the archives Or do you just not have a clue ;-)
>
> Erik
>
> -----Oorspronkelijk bericht-----
> Van: gasification-bounces at listserv.repp.org
> [mailto:gasification-bounces at listserv.repp.org] Namens Rodenhuis, E.J.
> (Erik Jan,Student TBK)
> Verzonden: donderdag 7 december 2006 13:46
> Aan: gasification at listserv.repp.org
> Onderwerp: [Gasification] Empirical data on dryer systems
>
> Dear list,
>
>
>
> For downdraught gasification of biomass generally is assumed that the
> moisture content of the biomass is below 15% (wb). As the moisture
> content of green wood is mostly higher and I have seen sawmills use
> water-cooled band saws, you need to dry the wood waste before it is
> suitable to gasify. Main options seem to be drum drying of flash/ring
> drying.
>
>
>
> Drum Drying:
>
> -        Co-current to reduce fire hazard
>
> -        Tair,in = 230 - 1100 degr. Celsius
>
> -        Tair, out = 70 - 110 degr. Celsius
>
> -        Empirical data on energy consumption 5 - 12 GJ/ton of water
> evaporated, see poster presentation Mani:
> http://www.biocap.ca/images/pdfs/conferencePosters/Mani_S_P1.pdf
>
> -        General statements made in diverse publications: "high"
> investment cost, "low energy use"
>
>
>
> Flash Drying
>
> -        short residence time < 30 sec
>
> -        drying at lower temperatures Tair,in = 100 - 650 degr Celsius
>
> -        "low investment, high energy use"
>
>
>
> A few other systems available:
> http://barr-rosin.com/english/pdf/airstream.pdf
>
>
>
> As we have will have with a downdraught gasifier with an ic-engine some
> low quality waste energy streams are available, namely from gas cooling
> (gas-gas shell-and-tube heat exchanger) and from the exhaust gases, I am
> interested to know what the general ideas about which drying system
> suits best. There might be some other criteria like the controllability
> of the process and fire hazards.
>
>
>
> Maybe there is somebody who can give some rule of thumb for investment
> cost and energy consumption of a 1 ton/h drying system. When assuming
> that we want to dry the wood waste (let's assume chips) from MCwet 30%
> to a moisture content of 15% we need to evaporate 115 kg H2O/h.
>
>
>
> Any hints or leads to good literature on the web on this topic??
>
>
>
> Regards,
>
>
>
> Erik Jan Rodenhuis
>
>
>
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