Biomass, Biobricks - Gasification

[Mushroom Man]

With cordwood, it seems necessary to have a bed of coals before gasification occurs.

I saw in another thread where a troubled EKO owner was encouraged to get biobricks for a test to see if his problems stemmed from incorrect settings or high moisture wood.

Is it necessary to burn biomass (biobricks or biomass pellets) with a bed of coals created by wood or pellets or coal or charcoal in order to achieve gasification in the secondary chamber?

 

[pybyr]

Pellets would need something under them in order to not fall or blow down through the nozzle.

I tried some "eco logs" a couple of years ago, and was underimpressed

I think that the idea that you 'need a bed of coals before gasification occurs" is overstated. I can put some splintered pallet-slat pine kindling across my nozzle, with a split log on either side, and two pieces of pallet slat forming a V on either side of the split kindling, with some small splits placed on top, and have gasification occurring in less than 5 minutes from initial ignition. The bed of coals is desirable, but not necessary.

 

[henfruit]

A little newspaper a little pine alot of splits big and small to give me a full fire box .one propane torch up the nozel and we have gassification in under 10 min.

 

[Hydronics]

I have found that the temperature of the refractory is a big factor. Getting the room temp boiler gasifying takes a good deal longer than a hot one that ran out of fuel.

 

[Piker]

If there are coals left in a boiler from the previous firing, they will come back to life very quickly and provide enough heat to induce the secondary burn very quickly. Basically, the coals are your refractory until your refractory gets hot. Kindling placed around the nozzle on startup produces coals very quickly which climb in temperature fast enough to get secondary combustion happening in a few minutes.

Biobricks made from wood do create coals, but not like chunk wood does. They are a more flakey and fragile coal, but they do the trick. Wood biobricks can be burned all by themselves in a gasifier, and they cause an extremely hot secondary combustion. But not all biomass bricks are equal...

I have not had any luck with the grassy biomass. It will produce a tremendous amount of gas when placed on top of a hot bed of coals, but once the coals are gone, so too is the secondary combustion. Part of the issue with the grassy biomass is the ash content... perhaps 7X that of wood. Once the ash builds up on the refractory at the base of the firebox, the refractory in essence becomes insulated from the heat of combustion and cannot maintain a high enough temperature to produce a secondary burn... at which point you just get tons of smoke rolling out the chimney. From what I have read, the grassy biomass also produces more caustic acids than wood... which can wear away at boiler plate more quickly on a unit that isn't properly maintained.

cheers