EthanD.net

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| Gasification |

| Project Journal |

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| Conclusions |

4/13/09 - I haven't had time to get very far into the electrical power half of this project that's required for it to be CHP, but now Josh and I are diving into it. We have decided to building a stirling engine using old air cylinders to run a generator that will supply our electric power. I will most likely be adding a new branch to this website to follow the stirling engine project, as it will be a big project on its own.

4/12/09 - The wood chip system is now supplying all domestic hot water for our house! Last night we did the final plumbing required, and made the switch. The heat storage tank is now at 140 degrees and a bit more burning will have it up to our targeted operating temperature of 180. So far the gasifier has consistently been able to increase the temperature of the tank 20 degrees in a two hour burn.

3/19/09 - Well ski season has been winding down and over the last week or so i've finally been able to get back into the project. All the plumbing in and around the storage tank, as well as around the boiler has been completed. yesterday I wired up one the differential controller that tells the pump when to circulate water from the tank out to the boiler to be heated. When the temperature at the boiler becomes 15 degrees higher than the water in the bottom of the tank, the pump switches on. I also installed a barometric damper in the chimney after the heat exchanger to control the effect of the draft on the gasifier. This should prevent the over firing we saw when my sister was running her tests in December.

Tonight we ran completed the first burn that was actually heating the water in the storage tank. After 1 hour of burning the temperature in the 800 gallon tank rose about 10 degrees. 800gal = 6400lbs x 10degrees/hr = 64,000BTU/hr being absorbed into the tank. This is right on target for our house.

during this test the fuel consumption was approximately 1 cubic foot/hr, which is about 20lbs/hr. 20lbs/hr x 6000btu/lbs = 120,000btu/hr of chip being burnt. so we were capturing about half of the heat being released. This confirms what we already knew: we need a new boiler/heat exchanger with more surface area that can get more of the heat out. Its also possible that with some tuning of the secondary air, as well as the new barometric damper, we can get a bit more heat out of the chips.

12/08/08 - My sister Hannah is working on an efficiency study of our gasifier system for a class at Dartmouth. Today she came up with several thermocouples and a thermal camera to collect some data. This was the first burn we've done with the installed gasifier and water circulating in the boiler. As it turns out, the affect that the nine foot chimney has on the fire is very big. It took off at a whopping burn rate of 70lbs of chips per hour. That's about 420,000 btu/hr going in, and at a water flow rate of 5gal/min we were only able to get out 96,000btu/hr. It is possible that with a lower flow rate we could have extracted more, but we were a little scared to slow it down for fear of producing steam in the boiler. The fire was too hot for our system!

From gasifier_test12_08_08

Alot of valuable information was learned. For one, we learned that the fire can be controlled (without loss of optimum gasification) by changing the draft. This works because controlling the draft is basically controlling the suction on the fire, it is different than, say, just controlling the primary air. Also, because the fuel is gravity fed, and the fire can take it as it needs it, it will automatically optimize its fuel to air ratio. Having realized this after today's burn, it's evident that we need to reduce the draft on our system.

12/02/08 - Today we got the boiler mounted on the gasifier, and all hooked up to the chimney. Then we did a test burn with the boiler dry, so no water being circulated. We wanted to test this because if the power ever went out while a fire was going, the boiler would rain, and it would have to be able to survive "running dry". The test burn was amazing. With no water cooling the chimney, and nine feet of insulated chimney on top of it, the gasifier burn like crazy! The entire boiler was cherry red after about 30min of burning... that's a good 60lb hunk of steel, most of which doesn't even directly contact the flue gas. Based on this I would predict that it is approaching the melting point of steel (~2700 degrees F) in the secondary burn zone! Hopefully we never have to run it dry for very long! I think that with the increased draft of the tall chimney we will be able to use a much larger boiler, and extract around 100,000btu/hour.

At this point its all come down to plumbing. The pipes are layed between the boiler and the storage tank, and both are ready to plumb together. After that its just some indoor plumbing to get the wood system linked with our existing system.

11/21/08 - The last few weeks have gotten really busy and project work kind of got kicked to the backseat for awhile. My dad and I have been doing some preliminary plumbing work to make the switch over to the new system a bit smoother. Most recently we have been rushing to get insulated pipes buried out to the furnace shed before the ground freezes. We are using 1 inch PEX encased in a foam box made of "blueboard" insulation, with expanding foam sprayed in around it to hold it all together. this setup will insulate quite well, and be much cheaper than the commercially available insulated PEX that is commonly used for outdoor boilers.

I have also been experimenting with refractory compounds to line the fire box and secondary burn areas of the gasifier. I have found a type of cement made by "FireComp" that can be purchased from McMaster-Carr for about 1$/lb. It's rated for up to 5000 degrees F, which beats any type of metal. My initial tests have shown that it is very easy to work with, and it bonds with steel, so it could potentially be troweled on the inside of a steel firebox to protect it. One of the biggest things i've learned so far in this project is that to burn wood as efficiently and cleanly as possible, you can't try to control or slow down the fire; You have to let it burn flat out with the right amount of air in the right places. I think that ceramic based refractory cement is the only long term way to confine an uncontrolled fire so its heat can be captured.

10/29/08 - Last weekend my dad and I built a 7' x 7' shed next to our house to house the gasifier. It came out very nice, and in fact is big enough that we may even be able to store some chips in it as well. |click here for pictures of the shed|. The 800 gallon tank is now under construction, and should be done this weekend if all goes well. |Click here for pictures of the tank|.

10/20/08 - We tested the new fire tube boiler today, and had amazing results. We played around with the flow rate a bit and recorded the following data:

Obviously it is a wood fire, and thus the burn rate is not constant, so certain data points may have been taken during a hot period, and some during a relatively cold period. Regardless 40,000-60,000 BTU/hour is right on target for our application.

|Click here for pictures of all Boiler/heat exchanger prototypes|

10/16/08 – The boiler is nearly finished, but I ran out of gas for my welder yesterday and the local shop won’t be able to get me a refill until tomorrow! In the mean time we have been finalizing the design for a heat storage tank. Yesterday we received a custom PVC tank liner made by Royal Liner. We plan to build a large wooden barrel type tank using vertical 2x10s (I have just added more on this to the heat storage page.)

10/10/08 – We have designed the next boiler. Based around materials we already have I have designed an 8x8x24” tank with nine 2x2” square steel ducts up through it. It will hold a little under 3 gallons of water and have about 1700 sq. in. of surface area between the hot gases and water. With a flow rate 6gpm this should be able to extract plenty of heat without boiling over… and of course there will be relief valves…

10/6/08 - The 5’ jacketed stack boiler was tested today… we had the flow rate set a little low, and due to the very thin water jacket it boiled over very suddenly, I narrowly missed a shower of scalding water. We learned that the flow rate has to be quite high for a boiler like this. Even with our boiler over we were able to get a few data points, and I estimate we could have gotten 50,000btu/hr out of this boiler with the proper flow rate. Unfortunately we threw this prototype together really quick and it isn’t fit for another test

10/1/08 – Over the last few weeks several test burns have been completed using a prototype boiler to extract heat. It is a 30gal drum with a stack up the center. It holds about 100lbs of water, and we were able to extract 20,000-25,000 BTU/hr. This is about 20% of the BTU’s worth of wood that was burning, and stack temps were still over 1000degrees, after the boiler. Still it is a data point that we can work with.
            The next gen. boiler should be testable tomorrow. It is a 5’ dia, 5’ long stack, fully jacketed with a 1/2” thick jacket of water.

Update 9/27/08- a fairly "polished" prototype of the gasifier has been completed, and several very successful test burns have been made, including a successful demo at the Shelburne Farms fall harvest festival! ( Click Here for the Burlington Free press article.)

Currently I am working on prototype boilers to get the heat out of the stack and into water. We are also designing an 800 gallon cylindrical water tank that will serve as heat storage. Pages for these new development s will be coming up in the Biomass CHP section soon.

9/12/08 – Legs were welded to the frame to provide a more stable base. The diagonal Baffle part that was designed previously was cut and welded into the firebox.

9/10/08 – Added an experimental diagonal plate behind the fuel baffle to keep baffle/fuel cooler, and direct flow of gas up the stack better… test burn was successful!! Know I just need to weld a permanent piece in. Also we determined that very small, but regular tapping on the grate solves a lot of the ash problem.

9/5/2008 – I spent the week working on the newer/sturdier v-draft prototype. 3/16” thick steel firebox, angle frame, and Stainless stack. We did a test burn on woodchips this evening and results were as follows: Started strong, 30inch/hour burn rate. Slowed to more like 20-25inch/hour. Was drawing secondary in some leaks around the stack and hopper flanges. These will need to be fixed, but also means we aren’t’ giving it enough secondary. Also, it seems a diagonal plate behind the fuel baffle would help guide the gas up the stack, keep the baffle cool, and allow for another preheated secondary air inlet.

Contact: edreissigacker@gmail.com

Copyright Ethan Dreissigacker 2008