Wood gas - for more than just a boiler

[renewablejohn]

Cogeneration is a terrific idea. Having a large back-up power source is attractive in case of an outage. Electricity via gasification does not seem at first blush to be overly complicated. It seems to be mostly about cooling and filtering the gas before it gets to the the intake manifold. Then keeping up a frequent maintenance schedule.

However there are some questions that come to mind; like:
1. How much pyrolized woodgas can one divert to electrical production without materially impacting the efficiency of heating. Perhaps by using really small diameter splits you could maximize gas production.
2. Where do you drill in to connect the gas outlet tube without breaching the water jacket? These gasifiers are expensive and you would not want to wreck one with ill-conceived experimentation. It would be good if we could back out of the experiment gracefully if it proved too cumbersome or it didn't work as expected.

I think the easier route is to use a woodgas kit like the GEK to power a water cooled generator giving you the electricity as the primary energy source. Then plumb in the water cooled generator into the central heating system with a heat exchanger on the exhaust pipe for further heat recovery.

 

[Ugly]

I think the easier route is to use a woodgas kit like the GEK to power a water cooled generator giving you the electricity as the primary energy source. Then plumb in the water cooled generator into the central heating system with a heat exchanger on the exhaust pipe for further heat recovery.

I'm going to have to agree and disagree with with you...

First off, I agree that it would be easy. But then I'd be dependant on an internal combustion enging for primary heat... not a good idea imo for several reasons.
-actual BTU recovery is questionable even with a water jacketed exhaust which is actually a difficult thing to do well
-engines break and are difficult to change when plumbed in place. Especially at forty below with the wife glaring at you from the kitchen window.

The GEK kits are interesting and great for experimentation. That's as far as it goes. Practical long term gas production is going to have to come from something a bit more robust, designed from materials that will last as long as I need. Most of these wood gas boilers have a long life with few moving parts, easy to keep a spare blower, seal or even refractory casting around. Further, if generation is a secondary need (which it is in a grid tie arrangment) a downed engine can be left to languish for an at leaisure swap or repair. Finally wood gas used in a boiler directy doesn't require filtration as it consumes it's own tars etc... my filtration needs would be limited to just a small engine and and (potentially) an open flame heat pump (air conditioner) resulting in a less complex and easier to maintain system.

Regards,
Ugly

 

[leaddog]

I haven't really looked into this but I was wondering if it wouldn't be easier to just produce the wood gas, filter it, and then pipe it to the generation unit and any excess pipe to a gas boiler. I don't know if it is posible to burn in a gas boiler but it seems like it should. I thought it was a fairly simple thing to produce wood gas and it seems like you could then have three seperate componets so you could have spares to swap and none of them would be overly complicated.
leaddog

 

[Ugly]

I haven't really looked into this but I was wondering if it wouldn't be easier to just produce the wood gas, filter it, and then pipe it to the generation unit and any excess pipe to a gas boiler. I don't know if it is posible to burn in a gas boiler but it seems like it should. I thought it was a fairly simple thing to produce wood gas and it seems like you could then have three seperate componets so you could have spares to swap and none of them would be overly complicated.
leaddog

I may end up reverting to a clean wood gas (filtered) boiler type system based on low pressure nozzles (like methane burners that already exist). I have two months to consider and then I’m building something. By that I mean I’m putting down the pad and putting up the building while I also start on building the design I settle on.

Leaddog, yeah as you can see where I quoted myself earlier, that's already one of my three approaches. The attraction to having the entire thing boiler centric is the ability to consume unflitered gas for what is really the primary goal heat/DHW and just dealing with smalls amounts of filtered gas for seconday purposes. A standard methane burner system designed for low pressure gas works fine from a gassifier if the gas is filtered....

 

[renewablejohn]

Ugly

I hope you are right with regard to the boiler system consuming the tar which is produced. I have looked at many commercial plants of the 250kw to 750kw electric generation size and despite assurances from the manufacturers the achilles heal has always been tar build up whilst burning the woodchip. If you can crack the problem I will be first in the queue as it would be a neat solution.

 

[Ugly]

Ugly

I hope you are right with regard to the boiler system consuming the tar which is produced. I have looked at many commercial plants of the 250kw to 750kw electric generation size and despite assurances from the manufacturers the achilles heal has always been tar build up whilst burning the woodchip. If you can crack the problem I will be first in the queue as it would be a neat solution.

We agree 100%. Tar build up from gasification is the major problem in all the designs. But I've yet to see tar build up in these boilers where secondaries run pretty much directly from primaries. They do crack the tar because the gas hasn't the chance nor need to cool and cendense prior to consumption. The minor draw of wood gas I envision taking before secondary ignition would still require filtration.

When I look where the gas is drawn down into the seconday from above I just wonder if I can safely and efficiently remove some wood gas at that point. Thoughts I started with are dual secondary chambers, size adjustable secondary chambers, stacked primaries (one on top of the other with a divertable nozzle set in the upper primary such that gas can be drawn into the boilers normal secondary or sent off to the filtration unit for external use)... all of these approaches have their pros and cons.

People here have posted some thoughts and insight that have tweaked me along (pleasantly) for the past few days. I think it's a solvable problem, I'm not saying I'm the one to do it, just that it can likely be done. Maybe even by me if I'm diligent and resourceful....

 

[Duetech]

Tar collection might possibly be simplified with a large air/air type heat exchanger sort of like a flat plate heat exchanger. Orient the large exchanger so that it would allow condensation and collection of the tars at the bottom with valved outlets with removable screw-on (?) canisters. Possibly use the blower intake from the gasifier, at least partially, to cool the producer gas and tars and use the heat from the tars and producer gas to preheat the intake air for the gasifier for more efficient gasification. Re-introduction of the tars in to the primary chamber for complete burning would have to be factored in and that might be achievable by use of the preheated intake air that keeps a vat of tars warm enough to flow without solidifying so it can feed the fire. The overall efficiency should pique some though with the burning of the otherwise annoying tars.

What all has to be filtered out of the raw producer gas besides tar? Ash and other matter could conceivably be collected on the "plates" and drip down with with the tars thereby using the tars as the filter medium. The air/air exchanger would have to be large enough to allow "slow" moving hot air to be most effective for condensation purposes. Nominal humidification of the exhaust gasses might be required for higher condensation collection in times of dual purpose venues and that would address peak efficiencies but might go a long way towards gas purification. (?)

 

[Ugly]

Thanks to those who have responded - I think I have a couple ways to proceed with this thanks to some input.

One lesson I learned by reviewing the threads for other home brewed rigs (here and all over the net) is that people type "I wish I would have" quite a bit - so I'm mindful of that.

The first stage is to prototype and get a base line so I'm going to build a disposable (non-pressurized) water jacket style downdraft gassifier from boiler plate and cheap materials. I have enough on hand to complete several if need be. The goal here is to enable testing of modular secondary burn chamber castings in such a way that I garner some insight into what happens in the primary and secondary chambers when I start drawing off unburnt gas from the primary. This will be a very basic downdraft design with manual controls -I already have a firetube heat exchanger of about the right size that I used for testing the ability to draw heat from the exhaust gas of a stationary diesel.. reuse reuse reuse and only then recycle right?.... My prototype needs to last a couple months

As to the riddle of drawing off unburnt gas I'm going to test several approaches such as;
cast ceramic pipe to existing style ceramic nozzle - test coming though the side and the bottom
self cleaning cast ceramic slide valving - embedded sliding ceramic plates within the bottom primary chamber ceramics to redirect gas flow
a balanced vacuum approach where I try and suck wood gas from rear bottom of the primary chamber using either/or mechanical engine vacuum or induced vacuum

I'll be doing a lot of casting by the looks of things so thanks in advance to my neighbour T. for the unrestricted use of her kiln and expertise until the project is over.

I'll reuse my cyclone and filter system from the modified Imbert gassifier for drawn off wood gas. Since I built it all to be modular, it's the least hassle (if it works of course) and will give me an honest/reasonable/reproducible/comparable measure of what kind of product I get out of it vs the traditional gassification unit.

Like usual, I'll build it all on one of the dual axle open bed trailers so I can work on it indoors (it's really cold here) and then cart it away from humanity before the explosions (oops- I meant test firings) burn down the shop. I'll likely start in three weeks for the prototype, I'm doing extensive and much needed repairs in my Dad's rentals at the moment.

Kudos to a certain data centric member for demonstrating the need to measure more accurately in my prototyping that I had intended to. Experience is great, data is easier to transfer.

Anyone have any ideas on checking the atmospheric pressure in/at different points in the secondary chamber and firetubes? My concern of course is the heat would pretty much eat any standard instrument alive....

I also have hopes this prototyping leads to the ability to do some materials testing of various ceramic products... has anyone ever done any business with these guys? http://www.cotronics.com/vo/cotr/index.htm

The flexible ceramic products look very interesting....

Regards,
Ugly

 

[Duetech]

Tried the url. Didn't work. fyi. Never heard of them though. Thanks for the interesting topic and the great input. Please keep us posted from time to time. Just for grins how about a remote starter for when you try the gas vacuum?

 

[Ugly]

Tried the url. Didn't work. fyi

Thanks Cave
fixed... blond moment....

 

[Fred61]

Hey Ugly,
There are a lot of words in the posts above and I haven't re-read the whole thread so this subject may have been discussed. I was sitting here thinking how beautiful the flame on the EKO is and how many oil boiler manufacturers would be envious of it. I recalled this discussion and a thought came to mind. I think I recall you stating in one of your posts that you had played with steam so I wanted your thoughts on an idea: Would it be possible to slide some sort of pressure vessel into the lower chamber of the EKO and capture the heat and make steam. Seems to me that it would be a good way to take advantage of the gassifier's power with the least amount of modifications. Any heat not used to make steam would heat the boiler water.

 

[Ugly]

Hey Ugly,
There are a lot of words in the posts above and I haven't re-read the whole thread so this subject may have been discussed. I was sitting here thinking how beautiful the flame on the EKO is and how many oil boiler manufacturers would be envious of it. I recalled this discussion and a thought came to mind. I think I recall you stating in one of your posts that you had played with steam so I wanted your thoughts on an idea: Would it be possible to slide some sort of pressure vessel into the lower chamber of the EKO and capture the heat and make steam. Seems to me that it would be a good way to take advantage of the gassifier's power with the least amount of modifications. Any heat not used to make steam would heat the boiler water.

That's a great thought, I don't think it's been specifically touched upon. The pressure vessels you're talking about already exist in steam boilers in two ways; firetubes and watertubes. If the goal were steam, you could make quite nice steam with a wood gassification boiler designed for the purpose, since as you say the flame and heat are there for sure.

I had a great time playing with a (purchased) newly fabbed steam engine. I had a helping hand from a steam engineer from the merchant marines (he'll be 88 this year) and I used scrubbed and cleaned wood gas as a fuel source. What the experience taught me is, it's a really expensive thing to get into and when I thought about the complexities of scaling it up, I realized how impractical it is due to regulations, steam boiler operators certs and the huge costs involved. Modern reasonable sized steam engines would last forever, but the costs of buying are huge and the only way to defray that cost is to manufacture your own. I don't have a full metal shop, just a few welders and a lathe and I'm not an expert.

So I put it aside because of A) the large upfront costs B) the bureaucratic red tape C) The safety concerns for casual operators

It's a great technology, but I decided against it for small scale use.

Cheers
Ugly

 

[cguida]

Hello Ugly,

Pretty soon you're going to think I'm stalking you through your threads. I hope you don't find this tedius, but the other night I was reading at my new-favorite website http://stove.ru Igor Kuznetsov has designs for just the kind of woodburning appliance that you are describing.

"Each bell [heat accumulating chamber] is combined with the firebox through dry joint and an opening in the uper part and is provided with a separate output in the lower part into the chimney, another bell or fume chamber. Each bell can be provided with a heat exchanger in the form of water boiler registers, air heater, retort for fuel pyrolysis [emphasis added], technological materials, equipment, devices, etc. Gas-generator heat-producing device can be of various functional purpose and capacity. For example, gas-generator boiler for private house heating, including that of periodic action."
(batch feed -- after you read enough of this Russified English, you get to know the lingo...

Anyway, this sounds like exactly what you are looking for -- and you wouldn't have to butcher up a 10-15 thousand dollar (West) European boiler.

It could be that the answer to the home co-generation problem might be a truck-load of bricks from the local building supply place -- in may ways straight out of the 19th century, just with innovative design.

In any event, the investigation continues. Hope you found this helpful, or at least interesting.

Regards,
Smee

 

[Ugly]

Hello Ugly,
Pretty soon you're going to think I'm stalking you through your threads. I hope you don't find this tedius, but the other night I was reading at my new-favorite website http://stove.ru Igor Kuznetsov has designs for just the kind of woodburning appliance that you are describing.

Stalking? Not at all, Forums are for discourse and the point of examing the subject matter in public is to invite insight and the capture of disparate information across disciplines in an environment not usually enjoyed by a standard engineering process. In other words, let 'er rip.

Anyway, this sounds like exactly what you are looking for -- and you wouldn't have to butcher up a 10-15 thousand dollar (West) European boiler.It could be that the answer to the home co-generation problem might be a truck-load of bricks from the local building supply place -- in may ways straight out of the 19th century, just with innovative design.

In any event, the investigation continues. Hope you found this helpful, or at least interesting.

Regards,
Smee

Just for the record, I don't think cutting up an existing unit is the way to go at this stage. My intention is to build a modular boiler plate prototype and start experimenting. When I have the balance I want I'll spend the bucks and have what I think works fabricated by myself and others. If I get a couple years in and I'm satisfied, I'll implement across everything we own/rent as THE SOLUTION (sound dramatic music here) The only thing really holding me back from starting today is the reality of an Ontario winter and a reno project on our rental apartments.

Nice finds of information in both threads and both thoughts are relevant to what I'm trying to accomplish. I mentioned previously I was considering a multi chamber approach to the overall design and your post and those concepts by Kuznetsov have sort of sent me back in that direction in my thinking. One of the reasons I was considering a modified wood gas boiler type design is just that they are quite compact and easy to locate out in the field or even relocate at a later date. The asthetic value is poor admittedly.

Effectively it looks like he's wrestled with all the things I'm thinking and found a way to implement them into what he builds. Hopefully using concepts like his (I'm not ashamed to borrow) I can implement this in the package I want.

The stuff that guy builds looks like it will outlive me by a huge margin. Even in Russia, that kind of craftsmanship must cost a kings ransom... unreal work. I wish I could read Russian now lol... Still I'm going to spend a lot of time staring at some of those drawings and trying to figure out what the anglo translation means.

Thanks for the info
Ugly

 

[Mushroom Man]

The idea of using a "western European" gasifier as a source of syngas is not that weird. After all, they have created an efficient tool for the creation of syngas. The challenge is to capture enough of it to:
1) not impair water-heating
2) retain efficiency
3) produce enough syngas for generating meaningful amounts of electricity for a domestic user

Where there is a will, there is a way.

As governments in North America get serious about small alternative energy generation projects, attractive programs are likely to appear that will make this type of project financially attractive. It is already attractive on an intellectual basis.

While drilling a hole in the lower door is not an attractive option at present; it might become a lower risk option, if the grid was willing to pay $0.15 per kilowatt for my power. A wind generator is already high on my list of additions to the farm. If it could be coupled with syngas generated power from switchgrass (our mushrooms will grow on switchgrass next year), the icing would be on the cake.

This thread is compelling

Thanks Ugly.