Is anyone out there burning softwood in a gasifier --e.g. EKO 60 -- this time of year?

[cguida]

Is anyone out there burning softwood in a gasifier --e.g. EKO 60 -- this time of year?

I'm continuing to look for a solution to the problem of how to get through the winter efficiently and cleanly with junk softwood. Aparently the Froeling boiler doesn't have anything against soft wood. Maybe the other European gasifiers work well enough on soft wood too, in the right circumstances. I'm particulary interested in the EKO 60 because it takes 2-foot wood, which would make a difference if you are trying to burn a low-density fuel like junk spruce and fir.

So is there anybody out there who is actually getting by on softwood with an EKO-60 or something similar? Coiuld you describe your heating system, and tell us how your day goes with softwood? For example -- in the course of an average 10 degree day ( (that's 10 degrees cold -- not a 10-degree-day...), how often do you have to make a trip to the basement to fill the boiler? Roughly how many cords of softwood do you figure you need to get through a winter?

Also, a property of softwood is that it drys out fast. But it's also quick to absorb moisture, like on a rainy day even when it doesn't actually get wet. Do you have to take special care to keep it in a low-humidity place? Or are changes in ambient humidity irrelevent as far as a gasifier is concerned.

Based on my experience this year, I can tell you that trying to get through a winter with a conventional waterjacket boiler on softwood is, shall we say, labor intensive. I was going to try to make it to January 1 on softwood. But we ran out on Dec 15; switched to Tamarak, and then eventually the hard stuff. Softwood was good for not more than about 2 hours, so it was like tending a wood stove. (With the right hardwood, I might go 3-4 hours.) Also, it was sometimes tough to charge up the storage tank and heat the house up at the same time.

So I'm looking for a better way to use what I have in my woodlot. If you are using softwood, I'd be interested in your experience.

Thanks
Smee

 

[Piker]

I burned a little pine (not sure exactly what species) earlier in the year. Burn times were significantly shorter with it than using hickory or hard maple. Maybe around 40% shorter I would guess. The pine I was using had 2" and 3" stubs left sticking out all around it, and didn't stack up in the firebox very good... But it's basically just simple math... 28 or 29 million Btu's per cord of hickory... 19 or 20 million Btu's per cord of pine. If you can get it stacked up the same, you should get around 30% shorter burn times.

I played around with about 3/4ths of a cord of it, and found that the best use of it was to just burn it when I was around to load the fire. Second best was to mix it in with some decent hard stuff. I have gotten into the habit of tending a small fire when I am home by adding just a piece or two at a time while maintaining a generous coal bed... this keeps the efficiency up, especially on an oversized boiler. The pine really works well doing this because it burns fast and hot... as soon as you put a couple pieces on a hot coal bed, you get instant gasification and the water temp goes up in a hurry. I mean, you get that with any wood you throw on a good coal bed, but the pine seems to burn the hottest. The drawback is that it doesn't keep the best coals... so even in this scenario, it seems to pay to throw at least one piece of hardwood in now and then to maintain a solid coal bed.

One thing I noticed about burning strictly pine was that the boiler would tend to run a little hotter towards the end of a load of wood. The boiler didn't seem to idle as well compared to using hardwoods... or even softer hardwoods like soft maple or even quaking aspen. I never had an overheat problem, but it seemed like I was getting a larger proportion of the heat load satisfied by the upper chamber alone, which will reduce overall efficiency.

hope this is helpful in some way.

cheers

 

[pybyr]

Jebatty has mentioned here on Hearth that he burns mostly pine, with no problems.

I am burning some red pine mixed in with hardwoods- I figure that a blend is probably best.

Some say that gasifiers extract more BTUs from a given type of softwood than other burning methods on a wood-by-wood apples to apples basis, on the theory that they can combust all the volatile stuff that usually is just a mess or smoke with other forms of burning. I am not sure that anyone has really documented that, though.

 

[jebatty]

Almost all of my wood for the Tarm is pine, pine slab wood or aspen (popple). Makes no difference to me whether it is +30F or -30F. My wood is dry, usually two full summers of seasoning in a woodshed with good ventilation. It is the wood I have and the wood I burn.

 

[Tree farmer]

my comments are about the same, I burn hemlock, pine and spruce on the weekend when I can reload after 6hrs. It is best to mix a few hardwood pieces with the load to end up with a good coal bed. Not sure what you would get for softwood burns with an eko 60 though, but its got to be way better than what you currently describe

 

[Duetech]

I'm kind of like Tree farmer. Pine is for evenings after work and weekends when I can spend time for more frequent loading. Helps save the hard wood for the more serious or lengthy burns. Pine gives the btu's but about 6 hr max for burns.

 

[jebatty]

For example—in the course of an average 10 degree day ( (that’s 10 degrees cold—not a 10-degree-day...), how often do you have to make a trip to the basement to fill the boiler? Roughly how many cords of softwood do you figure you need to get through a winter?

Winter where I live is cooold - we had 19 nights below freezing in Dec and 20 in January; 2 January nights hit -36F. I have 1000 gal storage, and typically one burn/day on the really cold days, 1-2 loads of wood. The first load does a good burn for about 3-5 hours with little idling; the second load, if needed, will go longer because storage water temp is higher and there will be more idling. Each heating situation is unique (temp, winds, sq ft, comfort levels, insulation, etc.). If I compare the Tarm to the prior water jacket OWB I used, I estimate I'm burning 1-4 - 1/3 of the wood I burned before.

Also, a property of softwood is that it drys out fast. But it’s also quick to absorb moisture, like on a rainy day even when it doesn’t actually get wet. Do you have to take special care to keep it in a low-humidity place? Or are changes in ambient humidity irrelevant as far as a gasifier is concerned.

All my wood is stored either in a covered wood shed, or after stacking with a piece of corrugated metal on top to keep the rain/snow off. It dries well and stays dry. Ambient moisture, at least in MN, has no discernible effect. All wood stored covered outside where we live will end up with about 18% MC.

Softwood was good for not more than about 2 hours, so it was like tending a wood stove. (With the right hardwood, I might go 3-4 hours.) Also, it was sometimes tough to charge up the storage tank and heat the house up at the same time.

Heat output per pound is nearly the same for all woods, with the resinous pines actually having more btu's/lb than most hardwoods. By volume aspen (popple) and some pines are only about 1/2 the btu's of some oaks and hickory. I don't see why you should have any more difficulty heating with softwood vs hardwood, other than the fact you have to refuel more often. They both turn out the heat. If you are having trouble getting the heat you need, then there are many factors which need to be considered as the cause of what you are experiencing. A few are:
-- btu (output) of the boiler: is it rated for your heat load? Do you know your heat load?
-- plumbing lines between the boiler and the zone manifold: keep in mind that 1" lines are sized for about 8 gpm and 80,000 btuh; 1.25" lines about 14 gpm and 140,000 btuh; 1.5" lines about 22 gpm and 220,000 btuh. Are your lines sized properly for your heat load? (assumed delta-T = 20) Is your circ sized to move the gpm? I made big mistakes in this area, now largely corrected, and have learned a lot regarding pump head and circ sizing.
-- total pump head and circulator sizing: this is a stickler which can easily end up being full of mistakes for the do-it-yourself or inexperienced HVAC person. You need to be reasonably accurate in calculating pump head and then matching a circ in the middle of its curve to provide the gpm you need to meet your heat load. If your lines are undersized it is not a simple matter to increase your gpm simply by putting in a higher capacity circ unless it is rated for increased head cause by increase in gpm. Pump head increases about by the square of the gpm increase.

 

[cguida]

That's good news, Jebatty!

Tell me more! On an average brisk day in January, lets say... you get up and (presumably) fill the boiler and get it going again after the night. How long will this first loading last? Will the fire go out and then you run off the tank till evening, or what? Will the fire eat that first load all at once while dumping the heat into the tank? Or will it sort of 'porpose' along on some kind of duty cycle -- burning hot for awhile, then idling, then starting itself up again off and on for 10-12 hours?

I must say this 'Stop and Go' action gives me pause when I contemplate burning softwood. An idling softwood fire sounds like an invitation to creosote and an eventual chimney fire, doesn't it? With the Memco, you really only get one pulse of heat. Then the fire burns out and you make a new one...

I guess the real questions are: How many times in 24 hours in January do you load the boiler; and roughly how much wood do you burn in the course of a year? Do you burn softwood in your house stove too?

 

[cguida]

Sorry Jebatty -- looks like our replies crossed. I read your first; then went out to the barn to check for lambs; then sent reply witout checking to see what else was on this thread.
Turns out I had saved a post you made on flat plate heat exchangers from almost exactly a year ago. That was helpful then, and this latest is directly relevent to a problem I might be having -- namely moving enough heat in and out of the tank. I have a 40 plate 12x5; 1 inch lines. Problem is, I am feeding it form the house side with a 3/4 inch line. I really don't have any good way of knowing how it is working except to watch how long it takes to charge the tank -- deg/hour temperature rise. The Memco (rated 120btu), burning good hardwood, and having satisfied all the house-heat needs, can raise the thousand gallon tank maybe 2.5 to 4 degrees/hour. Does this sound anywhere near right? I meant to ask people how many degrees/hour they can raise their tank temperatures just to get some idea of how it should go.

In actaul practice, we are pleased with the system when we burn good dry wood. Lately we get up at 5am; load the boiler; load it again around 7am, and just forget everything and run off the tank during the day. Then we make a fire around 4 or 5, and keep it going well till 10 or 11pm. After that, it's up to the tank till morning. This if for a 7000sf house (although we don't heat it all equaly). We don't have any gounds for complaint, really; except that I'd like to skip the 6 or 7 cord of hard wood, which costs money.

That 6-hours/load figure that people mention sounds pretty good to me. That would be a BIG improvement over what I'm doing now.

Now I have to re-read your post, and chew on it alittle.

 

[jebatty]

...40 plate 12x5; 1 inch lines...from the house side with a 3/4 inch line...Memco (rated 120btu)...having satisfied all the house-heat needs, can raise the thousand gallon tank maybe 2.5 to 4 degrees/hour. Does this sound anywhere near right? ...how many degrees/hour they can raise their tank temperatures just to get some idea of how it should go.

Approximations:
On the boiler side to the hx, 1" line, how long is the total run (round trip)? If I assume 100' (50 feet from boiler to hx and return), that is about 13' head. A 5 x 12 x 40 can move about 28 gpm at 5 psi pressure drop, which means about 14 gpm at 1.25 psi pressure drop, that is 2.9' head. Then have to add for elbows, etc. Total head = 16'+. On this approximation, you could move about 140,000 btuh at delta-T = 20F. A Taco 0011 can move about 17 gpm at 16' head, or about 14 gpm at 19' head. What circ do you have, what does its pump curve show based on these (or other) approximations?

If your total 1" line is 150', then your line head is about 20'. This changes the calculations. At 23' head a Taco 0011 can move only about 10 gpm = 100,000 btuh at delta-T = 20.

You then also need to do the house side at 3/4" to calculate head with your circ to determine how many btuh you can move through your hx. 3/4" is rated at 4 gpm = 40,000 btuh (delta-T = 20F) for maximum heat transfer. Is the 3/4" your limiting factor?

As to how long to raise the temp in a storage tank, not an easy answer. How big is the tank, what is the insulation, how many btuh are you moving into the tank, is the tank the only draw on the btuh? You can calculate this by multiplying tank gallons by 8.35 lbs/gal for each degree. If you have a 1000 gallon tank = 8350 lbs, for a 5 degree rise you need 5 x 8350 = 41750 btu (assume no losses). At 41750 btuh, it would take one hour to raise the tank 5 degrees (no losses).

 

[cguida]

Thanks for considering this heat transfer problem. Very impressive -- how you seem to have these figures at your fingertips. Is this what you do for a living? Me -- I have only the vaugest idea what head pressure is.

I also get a kick out of this -- [the old TV commercial -- very serious voice: "It's 11pm...]" Do you know what your Heat Load is?"
And I have to admit -- I don't really know. This place has a Peerless 160k BTU boiler, and in previous years that has always been enough with no strain. So the max heat load has to be something less than 160k. Otherwise the boiler would have been running all the time, right?

The Memco boiler was not exactly a well-considered design decision. It just worked out that a friend sold it to us for 350 bucks in 2001. It's only lately that we've been trying to think about things alittle more systematically.

Now, about the Tank Heat Transfer. Basically, based on what you say about a 3/4 inch line, it looks to me like things are working just about as could be expected given the physical layout.

The tank is a home-made immitation SSTS-type; unpressureized. There's a short (10-12 feet) 1-inch line to the pump (Bell&Gosset;NFO) and heat exchanger, and another 10 feet back to the tank. I don't thing there's any problem here.

On the house side, the wood boiler keeps the oil boiler warm, and the oil boiler supplies the zones -- one of which is now the other side of the heat exchanger (3/4 inch line; Taco 007 pump). This line isn't all that long -- maybe 20 feet total. There are a number of elbows, but nothing outrageous. No idea what the head pressure might be.

But get this: since I fiddled with the air vent on the backflow preventor on this line, it seemed to me that we got more flow and the charging rate for the tank went up a degree or two. Lets say it's now between 3 and 4 degrees/hour. At about 8.3k btu/degree, the heat being transfered down that line might be in the range of 24.9k to maybe 33.2k -- not great; but not that far off from your theoretical guestimation of 40k BTUh. If there is a bottleneck, the 3/4 line is probably it.

So far lately, we can draw the tank down to 150-140 during the day, and get it back up to 175 in the evening before we go to bed. This seems reasonable, but I don't have any other experience to compare with.

I need to study up on the whole idea of head pressure -- what it means and how to guestimate it. Meanwhile, if it turns out I need a faster re-charge time could I just get a bigger pump that would fit in the Taco 007 space? Or alternatively, could I take another unusued zone, and run it in parallel with the first 3/4 inch line -- thus have a theoretical 1-1/2 inch equivalent line to the heat exchanger?

 

[jebatty]

how you seem to have these figures at your fingertips. Is this what you do for a living?

I'm a home experimenter who is foolish enough to believe that he can do almost anything he sets his mind to. It's only in the last month or two that pump head has come into focus for me. I installed my Tarm in the summer of 2007, first fired it in Sept 2007, and constantly have relied upon Hearth.com, leads learned from the posts, questions answered, and Google to find more, to learn about hydronic systems. I erroneously thought a 3/4" line with a Taco 007 could handle 140,000 btuh through a 5 x 12 x 30 plate hx. Not. I've changed to a 1" line, still not really enough, but does handle what I need, with a Grundfos UPS 15-58FRC operating on HI.

Meanwhile, if it turns out I need a faster re-charge time could I just get a bigger pump that would fit in the Taco 007 space?

Yes and no. You do need to determine the btuh you want, then determine pump head at the flow rate needed to deliver the btuh you want, then get the circ that delivers this in about the middle of its curve. If you find that pump head is too great at the needed flow rate, then move backwards to the pump head you can reasonably meet with the circ you choose to get. Look at the pump curve for the head you can meet and you will have gpm. Remember, at delta-T = 20, btuh = 20 x gpm x 500. Delta-T = 20 is pretty common in hydronic systems: boiler output about 180, rturn about 160.

Or alternatively, could I take another unusued zone, and run it in parallel with the first 3/4 inch line—thus have a theoretical 1-1/2 inch equivalent line to the heat exchanger?

You can run parallel lines, but 2 - 3/4" lines do not equal 1 - 1-1/2" line. Two 3/4" lines will deliver just about the same flow as a 1" line.