Richard C Hill Boiler Design

[SuperYeti]

So I've been doing a ton of research, and am looking at building a boiler based on the Richard C Hill Wood gasifier boiler similar to the one @Hobartian has built: https://www.hearth.com/talk/threads...-based-on-the-design-by-richard-c-hill.68593/

I have a few questions after seeing his, and the original design, that I'm hoping someone on here can help me answer.

• What are the benefits or drawbacks to using a square burn and secondary chambers instead of cylindrical?
• How do I determine burn chamber size to fire tube to secondary chamber proportions?
• In the original documentation from Richard, he mentions using Plicast 27 and 20 for liners, with some fire bricks, and then a vermiculite casing, is there any reason I can't build the chambers and fire tube out of hard fire bricks?
• Instead of vermiculite, I'd like to encase the whole unit in steel, one to match the hopper, and make a cleaner look, and also for durability, and the ability to rebuild the internals later if needed. I was thinking of building in a few pieces, 1 box for the 2 chambers and the fire tube, the hopper, the heat exchanger, and having them join together with some bolts and some stove gasket making it relatively easy to disassemble for cleaning and maintenance purposes, and then using a fire brick tube and chambers, surrounded by either insulating fire bricks, or refractory insulation matte. How would I determine how much matting I need to keep the outside of the rig at a safe temperature?
• I see the original design, and @Hobartian recommended using http://www.ebay.com/sch/i.html?_kw=GAST+REGENAIR+BLOWER+R1102 for the intake blower, what should I be looking for in ideal characteristics for the induced draft blower on the exhaust?
• If i go with my idea of a steel casing, do I need to give a separation between the casing, and the primary and secondary air inlets to prevent heat transfer to the outer shell?

Once I get my head wrapped around the design a bit more, I can CAD it up, and start building, I'm very excited!

Any help or insight is greatly appreciated.

Thanks
Warren

 

[peakbagger]

Too bad you aren't in Maine. Dick Hill who I believe is 97 still does a radio show on occasion with one of the Hearth.com Members, "Tom in Maine" so you could ask him yourself.

Unfortunately they don't stream the show but here is a link to the website http://www.hotandcold.tv/radio.html

I expect that you would want to look for past posts on the Jetstream which is one of the licensees of the Hill patent and incorporated improvements. Dumont also sold a version but I don't see posts on them as often. Whatever you do get a good hot water storage tank, many of the commercial units were yanked as they were pricey and the installers went cheap on storage tanks by using 275 gallon oil tanks. The tanks rusted out in few years and when they failed many folks just stop using the boilers.

edited to correct dicks age - thanks Tom

 

[tom in maine]

• What are the benefits or drawbacks to using a square burn and secondary chambers instead of cylindrical?

Convenience and turbulence. It would be a simple matter to make it out of firebrick. Round is apt to induce more turbulence and better mixing of the wood gas and air.

• How do I determine burn chamber size to fire tube to secondary chamber proportions?

I know DIck and I had done this by trial and error. You have the luxury of copying others.

• In the original documentation from Richard, he mentions using Plicast 27 and 20 for liners, with some fire bricks, and then a vermiculite casing, is there any reason I can't build the chambers and fire tube out of hard fire bricks?

He wanted round chambers and castable gets that done easily.

• Instead of vermiculite, I'd like to encase the whole unit in steel, one to match the hopper, and make a cleaner look, and also for durability, and the ability to rebuild the internals later if needed. I was thinking of building in a few pieces, 1 box for the 2 chambers and the fire tube, the hopper, the heat exchanger, and having them join together with some bolts and some stove gasket making it relatively easy to disassemble for cleaning and maintenance purposes, and then using a fire brick tube and chambers, surrounded by either insulating fire bricks, or refractory insulation matte. How would I determine how much matting I need to keep the outside of the rig at a safe temperature?

Dick likes mixing stuff with cement. I think he is a frustrated mason. Vermiculite cement has structure and is CHEAP. All his Vermiculite cement commercial units had a steel shell. Only prototypes did not.

• I see the original design, and @Hobartian recommended using http://www.ebay.com/sch/i.html?_kw=GAST+REGENAIR+BLOWER+R1102 for the intake blower, what should I be looking for in ideal characteristics for the induced draft blower on the exhaust?

That is a forced draft blower. The forced draft blows air in on the fire and mixes the wood gas and air up, causing it to impinge
on hot refractory surfaces. The induced draft fan pulls all the exhaust through the unit.
The fan you mention produces rather high pressure and will help get things very hot. Imagine a car engine running lean on fuel.
Induced draft fans can be problematic if there is not a clean burn. Soot and creosote can throw it off balance. That being said, I would suggest something akin to a oil system power vent fan like a Tjernlund HS series. Be aware these are not sold for wood devices, but they do work.

• If i go with my idea of a steel casing, do I need to give a separation between the casing, and the primary and secondary air inlets to prevent heat transfer to the outer shell?

Good question. It should be insulated and a small air space is not a bad idea. The combustion zone gets very hot regardless of insulation.
A water jacket is ideal.

BTW, Dick was 97 in October. He has had some health issues, but was on the radio last week, sounding great! Maybe wood burning adventures leads to longevity??

 

[flyingcow]

Tom,

Listened to your show last week. Dick sounded as good as usual.

 

[SuperYeti]

• What are the benefits or drawbacks to using a square burn and secondary chambers instead of cylindrical?

Convenience and turbulence. It would be a simple matter to make it out of firebrick. Round is apt to induce more turbulence and better mixing of the wood gas and air.

• How do I determine burn chamber size to fire tube to secondary chamber proportions?

I know DIck and I had done this by trial and error. You have the luxury of copying others.

• In the original documentation from Richard, he mentions using Plicast 27 and 20 for liners, with some fire bricks, and then a vermiculite casing, is there any reason I can't build the chambers and fire tube out of hard fire bricks?

He wanted round chambers and castable gets that done easily.

• Instead of vermiculite, I'd like to encase the whole unit in steel, one to match the hopper, and make a cleaner look, and also for durability, and the ability to rebuild the internals later if needed. I was thinking of building in a few pieces, 1 box for the 2 chambers and the fire tube, the hopper, the heat exchanger, and having them join together with some bolts and some stove gasket making it relatively easy to disassemble for cleaning and maintenance purposes, and then using a fire brick tube and chambers, surrounded by either insulating fire bricks, or refractory insulation matte. How would I determine how much matting I need to keep the outside of the rig at a safe temperature?

Dick likes mixing stuff with cement. I think he is a frustrated mason. Vermiculite cement has structure and is CHEAP. All his Vermiculite cement commercial units had a steel shell. Only prototypes did not.

• I see the original design, and @Hobartian recommended using http://www.ebay.com/sch/i.html?_kw=GAST+REGENAIR+BLOWER+R1102 for the intake blower, what should I be looking for in ideal characteristics for the induced draft blower on the exhaust?

That is a forced draft blower. The forced draft blows air in on the fire and mixes the wood gas and air up, causing it to impinge
on hot refractory surfaces. The induced draft fan pulls all the exhaust through the unit.
The fan you mention produces rather high pressure and will help get things very hot. Imagine a car engine running lean on fuel.
Induced draft fans can be problematic if there is not a clean burn. Soot and creosote can throw it off balance. That being said, I would suggest something akin to a oil system power vent fan like a Tjernlund HS series. Be aware these are not sold for wood devices, but they do work.

• If i go with my idea of a steel casing, do I need to give a separation between the casing, and the primary and secondary air inlets to prevent heat transfer to the outer shell?

Good question. It should be insulated and a small air space is not a bad idea. The combustion zone gets very hot regardless of insulation.
A water jacket is ideal.

BTW, Dick was 97 in October. He has had some health issues, but was on the radio last week, sounding great! Maybe wood burning adventures leads to longevity??

Tom this is awesome, thank you. I'm just waiting to hear back a supplier for ceramic mat insulation to see if the price is right, and will start drafting my plans up. Once I'm done, I'll pop back in and show, and would love to get some feedback on my ideas. I really appreciate your help, and talk to you soon.

 

[SuperYeti]

Too bad you aren't in Maine. Dick Hill who I believe is 97 still does a radio show on occasion with one of the Hearth.com Members, "Tom in Maine" so you could ask him yourself.

Unfortunately they don't stream the show but here is a link to the website http://www.hotandcold.tv/radio.html

I expect that you would want to look for past posts on the Jetstream which is one of the licensees of the Hill patent and incorporated improvements. Dumont also sold a version but I don't see posts on them as often. Whatever you do get a good hot water storage tank, many of the commercial units were yanked as they were pricey and the installers went cheap on storage tanks by using 275 gallon oil tanks. The tanks rusted out in few years and when they failed many folks just stop using the boilers.

edited to correct dicks age - thanks Tom

Thanks peakbagger. My plan is to use probably a 500 gal propane tank, insulated for hot water storage. I've been finding some of those pretty reasonably priced on craigslist and such. Dick mentions in his original plans suggests either a sodium chromate or a nitrate-borate mixture in the water to help counteract corrosion, @Hobartian also used tannin's for protection, but thank you for the reminder .

 

[hobbyheater]

So I've been doing a ton of research, and am looking at building a boiler based on the Richard C Hill Wood gasifier boiler similar to the one @Hobartian has built: https://www.hearth.com/talk/threads...-based-on-the-design-by-richard-c-hill.68593/

I have a few questions after seeing his, and the original design, that I'm hoping someone on here can help me answer.

• Instead of vermiculite, I'd like to encase the whole unit in steel, one to match the hopper, and make a cleaner look, and also for durability, and the ability to rebuild the internals later if needed. I was thinking of building in a few pieces, 1 box for the 2 chambers and the fire tube, the hopper, the heat exchanger, and having them join together with some bolts and some stove gasket making it relatively easy to disassemble for cleaning and maintenance purposes, and then using a fire brick tube and chambers, surrounded by either insulating fire bricks, or refractory insulation matte. How would I determine how much matting I need to keep the outside of the rig at a safe temperature?

Jetstream's refractory liner.

The liner inside of a sheet metal box. The material between the liner and the box is vermiculite.

There is no vermiculite between the liner and the bottom of the box - the metal is burnt away. If you have no insulating vermiculite between refractory and the steel, the metal in places will get red hot.

 

[SuperYeti]

Jetstream's refractory liner.
View attachment 167554

The liner inside of a sheet metal box. The material between the liner and the box is vermiculite.

View attachment 167555

View attachment 167556
There is no vermiculite between the liner and the bottom of the box - the metal is burnt away. If you have no insulating vermiculite between refractory and the steel, the metal in places will get red hot.

Thanks for the pics hobbyheater. I had definitely thought about that, my plan is from outside to inside to use a layer of insulating fire brick, then a layer of high density fire bricks for the bottom, then on the sides a layer of ceramic mat insulation (granting it has a low enough thermal conductivity) then a layer of high density fire bricks. I think this should give me good thermal properties, while standing up to the rigors of getting loaded with wood and burning etc.

Hobbyheater do you have any dimensions, or know where i can find some of that Jetstream refractory base? I'd like to do some comparisons to the original stick furnaces to try and understand what changes were made to make the original design better.

Thanks

 

[hobbyheater]

Thanks for the pics hobbyheater. I had definitely thought about that, my plan is from outside to inside to use a layer of insulating fire brick, then a layer of high density fire bricks for the bottom, then on the sides a layer of ceramic mat insulation (granting it has a low enough thermal conductivity) then a layer of high density fire bricks. I think this should give me good thermal properties, while standing up to the rigors of getting loaded with wood and burning etc.

Hobbyheater do you have any dimensions, or know where i can find some of that Jetstream refractory base? I'd like to do some comparisons to the original stick furnaces to try and understand what changes were made to make the original design better.

The only dimensions that I could give you would be those of the sheet metal box. It will be many years before the current boiler is in need of rebuild as it is only over a year old.
The refractory that I use to make tunnels is " Dukast 3000"and I get it from;

Inproheat Industries LTD
680 Raymur Ave,
Vancouver BC
V6A 2R1

Tel 604 254 0461

On another forum I did a thread on the installation of the new Jetstream. Google search " Jetstreams out with the old "

 

[SuperYeti]

The only dimensions that I could give you would be those of the sheet metal box. It will be many years before the current boiler is in need of rebuild as it is only over a year old.
The refractory that I use to make tunnels is " Dukast 3000"and I get it from;

Inproheat Industries LTD
680 Raymur Ave,
Vancouver BC
V6A 2R1

Tel 604 254 0461

On another forum I did a thread on the installation of the new Jetstream. Google search " Jetstreams out with the old "

Awesome, Inproheat is who I ended up finding for the ceramic mat I'm looking at, they're about a 45 min drive from me. Are you in the lower mainland?

 

[SuperYeti]

The only dimensions that I could give you would be those of the sheet metal box. It will be many years before the current boiler is in need of rebuild as it is only over a year old.
The refractory that I use to make tunnels is " Dukast 3000"and I get it from;

Inproheat Industries LTD
680 Raymur Ave,
Vancouver BC
V6A 2R1

Tel 604 254 0461

On another forum I did a thread on the installation of the new Jetstream. Google search " Jetstreams out with the old "

So I think I found your thread: (hmm can't seem to post the URL here...)

Those pictures are great. Looking at the design, it looks like the charge air pipe is fed through the top of the secondary chamber to pre-heat the air, and there's no secondary air?

 

[hobbyheater]

Awesome, Inproheat is who I ended up finding for the ceramic mat I'm looking at, they're about a 45 min drive from me. Are you in the lower mainland?

Port McNeill ,Northern Vancouver Island.

 

[hobbyheater]

So I think I found your thread: (hmm can't seem to post the URL here...)

Those pictures are great. Looking at the design, it looks like the charge air pipe is fed through the top of the secondary chamber to pre-heat the air, and there's no secondary air?

No secondary air needed. Once the refractory base starts to glow yellow in color and the air passes through the tunnel,nothing is un-burnt.
This picture was taken at -5 c, the boiler is at full burn, the air is just hot enough to be uncomfortable to breath with no wood smoke odor.

 

[maple1]

Always great to see that pic once in a while.

 

[SuperYeti]

No secondary air needed. Once the refractory base starts to glow yellow in color and the air passes through the tunnel,nothing is un-burnt.
This picture was taken at -5 c, the boiler is at full burn, the air is just hot enough to be uncomfortable to breath with no wood smoke odor.
View attachment 167622

@tom in maine if I'm going with something closer to Dick's original design for the unit, do you see any reason why I need secondary air? It looks like the only main difference in the air handling between the Jetstream and the original is lack of secondary air, and using a single vacuum blower with a venturi induced draft. I'm guessing the additional airflow from the way the air handling is laid out negates needing that secondary?

 

[SuperYeti]

No secondary air needed. Once the refractory base starts to glow yellow in color and the air passes through the tunnel,nothing is un-burnt.
This picture was taken at -5 c, the boiler is at full burn, the air is just hot enough to be uncomfortable to breath with no wood smoke odor.
View attachment 167622

@hobbyheater, what temperatures do you see on the outside of your Jetstream when it's in use? I'm trying to determine what a safe exterior temperature to shoot for with my design is. It looks like if I run hardened fire brick, and then 6" of the ceramic blanket insulation I can expect an ambient temperature on the outside of the burn chambers somewhere in the neighborhood of 180F, this could serve double duty to heat the shop as well, but might be wasting too much energy and I may have to look at using a vermiculite insulating layer if it can get the temperatures lower.

Thanks
Warren

 

[hobbyheater]

Always great to see that pic once in a while.

It's my favorite!

 

[hobbyheater]

@hobbyheater, what temperatures do you see on the outside of your Jetstream when it's in use?
Warren

195 F to 261 F

 

[SuperYeti]

195 F to 261 F

Awesome, thank you. Do you insulate the outside of the refractory base, or only the upper portion of the unit?

 

[hobbyheater]

Awesome, thank you. Do you insulate the outside of the refractory base, or only the upper portion of the unit?

Only the upper portion.

 

[SuperYeti]

Only the upper portion.

Awesome, I think my plan is just about ready to draft now, looks like I can go with 4" (I'll probably do 4.5 as thats what the bricks i'm looking at come in) of hardened fire brick for the 2 chambers, and then depending on price either 4" of ceramic blanket, or 4.5" of insulating fire brick, with insulating fire brick on the bottom all encased in a steel shell, then the hopper and heat exchangers on top of that. This is the thermal conductivity calculation given to me by InProHeat on 4" of ceramic blanket.