Block Arch Efficiency

[CaptT820]

We run a block arch in the driveway as well with 4 steam pans. The arch portion of the firebox area is lined with firebrick. My blocks are filled with sand as I have a ready supply. The sand helps the thermodyamics of the blocks and helps keep the heat in. Its very rustic but very effective. 6-inch diameter flue pipe with damper is 10-feet tall, supported by guy wires. The firebox is just cinderblock, you can fancy it up with fire bricks and help the efficiency as i did last year, just didnt have the time this year. Our "door" is just a piece of 1/2" concrete board that I had lying around, this could be improved, but it was free. The firebox has a grate I made from high strength rebar. The grate has never even warped with proper welding and has 6-inches of clearance underneath. The biggest key to burning hot and keeping the pans boiling is to add a blower. I use a Vent-Tech 6-inch inline blower with a piece of 18-inch long stove pipe directly under the grate with a rheostat to control the fan. We went from a ~4 GPH evaporate rate to 8-9 GPH evaporate rate. You do have to feed the fire more often, but it burns much hotter, and even after 10 hours of boiling I never cleaned the coals out once, as they burn almost completely. Hope this helps.

[woodsy]

We run a block arch in the driveway as well with 4 steam pans. The arch portion of the firebox area is lined with firebrick. My blocks are filled with sand as I have a ready supply. The sand helps the thermodyamics of the blocks and helps keep the heat in. Its very rustic but very effective. 6-inch diameter flue pipe with damper is 10-feet tall, supported by guy wires. The firebox is just cinderblock, you can fancy it up with fire bricks and help the efficiency as i did last year, just didnt have the time this year. Our "door" is just a piece of 1/2" concrete board that I had lying around, this could be improved, but it was free. The firebox has a grate I made from high strength rebar. The grate has never even warped with proper welding and has 6-inches of clearance underneath. The biggest key to burning hot and keeping the pans boiling is to add a blower. I use a Vent-Tech 6-inch inline blower with a piece of 18-inch long stove pipe directly under the grate with a rheostat to control the fan. We went from a ~4 GPH evaporate rate to 8-9 GPH evaporate rate. You do have to feed the fire more often, but it burns much hotter, and even after 10 hours of boiling I never cleaned the coals out once, as they burn almost completely. Hope this helps.

I like that idea of filling the blocks w/sand. Hadn't thought of that. Should make good insulation and maybe moderate the heat on the blocks.
My 3' x 4' long unmortared block arch on a slab in its second year is showing a lot of heat damage/cracked blocks . It holds together OK still but
looking to improve on it some. Good boil rate 7-8 gal. hr cranking . Firebrick is pricey though . Probably $150.00 to do a 2 1/2 rows sides and back.
Was wondering about furnace cement on the block faces if that would hold on or not.
Like the OP, we are trying to save money by boiling our own, only about 3 gals syrup year

[CaptT820]

I found a guy on Craigslist in Woburn, MA that supplies high end firebrick and insulation to the commercial boiler industry. His prices were good and he has an amazing selection. You can buy the firebrick rated for a number of different temperatures from 2200 to 3200 degrees F. He also has an impressive supply of commercial grade insulation in all different thicknesses, a little of this goes a long way. The sand in the block arch helps along with some vertical rebar pieces anchored to the ground. The sand and the firebrick together allow the blocks to last longer before cracking. I also add a 4-ft long piece of aluminum angle iron (1"x1") that is screwed to the top layer of blocks along each side of the evaporator to set the steam pans on. It makes it much easier to get the pans in and out.
Still block arching for now, but we went from 2.4 gallons of syrup last year to 6.25 gallons this year. Thank god for the new homemade RO unit.

[Matt H]

It's been a few weeks now. Thanks again to your suggestions and experience offered! Anyway, I got a chance to try a leaf blower this weekend and it created some wicked heat. During a non-blower scenario and dry wrist size wood only the 2 front pans boil and the 3rd pan might slightly simmer. With the blower idling and mixing dry and green wrist size wood, all 4 were boiling and the stove pipe was too hot to touch. Things kept me busy and I didn't get a chance to measure gph, but am guessing it was somewhere north of 11gph.

Most cost effective features so far have been the leaf blower (maybe $2 per hour), using dry wrist sized wood (free), lining cement blocks with landscape pavers (free), and 4-5" depth in steam pans (free). The first 3 make fairly good sense but I may need to further explain the 4th. Most folks suggest using a 1-2" depth and this is best for most setups (just bottom of pan contacts arch's hot air). These steam pans are sunk into the arch using a framework. This, by no planning of mine, has created more heated surface area. So by maintaining a 4-5" sap depth we've been able to take advantage of the sides of the pans being heated.