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openspaceman

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Everything posted by openspaceman

  1. Good point, I have a skip depot just up the road from here, they reckon to redirect most skips containing just inert brick rubble, soil etc and screen it into hardcore, the fines do get mixed in with soil and sold as top soil. The give-away is the musty smell as you rake it in.
  2. That would be a good benchmark for comparing drying costs, we can assume the full capacity and a single use (as the poly tunnel is probably cheaper than other covered storage before the customer puts it in their storage). Correct me where I am wrong So: £1220 amortised over 5 years and 250 bulked m^3 which is 125 solid m^3 and 50 tonne of oven dry wood per annum. In UK under cover the best equilibrium moisture content we can expect is 10% and in the winter 20% is probably realistic in an unheated store. Let's say we end up with 62.5 tonnes of firewood On a simple rate of return calculation ignoring interest that's £3.9 per tonne of product and represents a cost of £6.50 per tonne of moisture removed. In 2000 my target cost for the fast dryer was £10/tonne moisture removed on a 24 hour cycle. The production cost is a bit irrelevant to the drying equation unless you have to either borrow or allow for the cash flow, i.e. how much do you charge for the labour and wood cost which you may not see a return on for 6 months. If it's waste wood and wet weather working when wages have to be paid anyway you may ignore it. On the other hand if you buy in wood at £50/tonne wet and process it using staff employed for the purpose then it is significant. The real question is how much more is a 1m^3 bag of seasoned wood worth to you than the same unseasoned and then what is a 1m^3 bag of seasoned firewood worth to you on the day before Christmas eve when you only have unseasoned cordwood left in stock.
  3. They did, it had a folding bottom wheel and was 36", VXF I think
  4. I cannot directly make the comparison but a 7 plate 350 rwd transit crewcab chassis has a maximum payload of 1652kg, with a very lightweight body and 3/4 tank of fuel it weighed 2100kg. A substantial toolbox is about 75kg. There's not too much to worry about the back axle as it can carry 1829kg including the body. Front MAM is 1750 rear 2450kg There is far less latitude with single wheel FWD as the sum of the axle weights is 3500. IIRC the crewcab with seats weighs 150kg more than the same LWB single cab. The brochure including weights is available on the ford website, I don't have a copy at home but can check if you want more info.
  5. The initial combustion is as a pyrolysing fire, only enough air gets to the pyrolysis zone to sustain it, the pyrolysis offgas from this is what burns in the flame. As the pyrolysis front gets to the bottom then it works as a normal updaraught fire, to keep it in gasifying mode the primary air velocity and hence volume has to increase significantly. The problem is that the temperature in the can goes up from about 600C for pyrolysis to over 1100C. Steel cans can just about survive the lower temprature but will spall off iron oxide at the higher temperautres and even stainless won't do much better. The interesting thing with these TLUD devices is that they won't work with wood withmoisture content of more than about 25% but with dry wood they produce charcoal if the fire is snuffed as the pyrolysis zone reaches the bottom.
  6. Yes, any wood burns well dry, Turkey Oak is drought tolerant and I think this is because it can store so much water in the stem, and draw on it, This is possibly the reason it shakes badly and has such a high tangential to radial shrinkage . We found it would rot insiode it's bark before it dried, a bit like birch if left out in the round.
  7. I don't know but it was the peltier coolers that drove down the cost of the bismuth teluride devices. I know purpose designed TEGs will have a higher conversion than reverse driven TECs, Caterpillar built a 5kW pile running off a large truck engine exhaust. I've looked back at the discussion when this stove was developed by people visiting Aprovecho, there was a presentation around October 2009. Looking at the website and diagrams it seems the two models are based on different principles, the camping stove is a development of Tom Reeds fan powered TLUD stove which I think is still in production in India, this was itself a developement of the Reed-Larson natural draught device. I did miss one vital point about this and that is it does recuperate heat passing through the TEG. It still lacks the secondary burning/premixing area noramlly associated with TLUD stoves. The other ( home stove ) is simialrly a modification of the Aprovecho Rocket stove.
  8. If it's a common managed under the 1925 law and property act then it could be considered legitimate air and recreation as long as the tree is not damaged.
  9. It uses a semiconductor Thermo Electric Genertor. This one probably uses the Peltier effect device as found in those 12V beer cooler fridges, in reverse. These Thermo Electric Coolers are only good for about 400C so interesting to see how it stands abuse. I guess they'll convert about 3% of the heat flux through them. I see these in the skip at the civic amenities site when people fling them after they wake to find their car battery dead. You can buy similar things that sit on a log burner to run a fan. Philips promoted a better made one for the third world and launched it in India, like this one it didn't account for the heat diverted from the cooking. Where there is a need for a clean cook stove there is not the wealth to pay for this, Improved cookstoves are typically sun 1USD made from tincanium and their life is measured in months. Cleanest tend to be top lit updraught devices but there are a number of siple devices promoted, they chifly work by controlling excess air and maintaining temperature in the combustion area for the flame to burn out. This one has no space for a burning flame. The electronics is interesting as I expect the raw voltage is ~1V and they must step this up to give the 5V usb output. About 2 billion people depend on biomass cookstoves and they're far behind Mr. Zuckerberg's tribe of 0.9billion.
  10. Yes We used to love it for pulp as it was heavy, so fewer pieces per trailer load
  11. Yes Less easy to service and height becomes an issue as debris builds up between the rollers. I prefer rails and a lift out section for the door to close. I've wanted to try a system with cheap home made flanges wheels and scaffold pole rails.
  12. A mate and I considered doing this, calling it green coal, we lost enthusiasm. Meat mincer from northern tools. Char dust is abrasive so don't expect long life. Starch paste from boiled potato waste I also made some turd like offerings using glycerin from biodiesel production and char and sawdust, gave up on that when someone told me the fumes from poor combustion were nasty.
  13. Can you get a year's logs in it? To my mind this looks a very good use of solar energy to season wood. Would it be worth erecting one of these on piers to increase capacity or would the wind loading be too great? How many years use out of the covering? Can you reckon a cost per M3 of solid wood seasoned? The thing about seasoning a luxury good like firewood logs is the increased value can easily exceed the change in fuel value. On the industrial scale the plant design allows for clean burning and the energy cost of venting steam up the chimney is a small proportion of the whole. As far as I can see there is little incentive to supply dry woodchip to the big users, who pay about £30/tonne as long as the wood is <45%mc wwb. So little incentive to dry this now. When NFFOs were first announced a large wood burning power station did commission a gas oil powered converted grain dryer because the premium on electricity generated from wood was great and gasoil relatively cheap. How much it's worth spending per M3 solid wood for a luxury market is the interesting question. At the small scale the polytunnel looks appealing, get larger and the logistics all change. The physics stays the same though and the simple fact is 0.7kWh of energy leaves the system with every kg of moisture that leaves the logs. If you want big scale then you need an accelerated process to get the water out and match your throughput. A big business wants to keep output up to meet demand whatever the vagaries of the weather for drying. At this end of the business we decided the capital cost of the containment meant the drying cycle had to be less than 24 hours, the only quick way of meeting this was high temperatures because the limit wasn't the ability to move the water vapour away from the logs but the rate of migration of the moisture from the logs and the ability to deliver the necessary energy into the log. Having a client that was adept with the grant system was the crux.
  14. It shouldn't be much of a surprise, consider a car engine, it works at near a perfect mix of fuel and air but there are only milliseconds to complete the combustion. As there is not quite perfect consumption the hot gases ( about 500C) travel on to the catalytic converter. Now as I said previously the catalyst just seems to lower the threshold at which a chemical reaction takes place. So any surviving oxygen molecules and any remaining part burned fuel can have a second chance to meet on the catalyst and combine. Of courser then their energy is given up as heat in the catalytic converter. A couple of points here, if one cylinder misfires persistently then all its fuel and oxygen end up burning in the cat, which will get very hot. The other is that prior to cats being mandatory lean burn petrol engines were being developed, these were challenging diesel engines for economy. However a catalytic converter would be receiving far too much oxygen to fuel gases from a lean burn and hence legislation made put paid to their development. Running on from this you'll begin to see that fuels burn in fixed ratios of fuel to air, e.g. one carbon atom requires 1 oxygen molecule (this is two oxygen atoms) but because air consists of 21% oxygen and 78% Nitrogen you have to supply 5 times more volume of air to get the right amount of oxygen. The correct ratio of fuel to air is known as the stoichiometric ratio. This stoichiometric mix is what is needed for a car engine. Wood is more difficult to burn but we have much more space and time to complete the combustion, we don't want smoke ( which is products of incomplete combustion) so we increase the opportunity for an oxygen molecule meeting a fuel molecule. We do this by adding excess air and maximising the three Ts, retention Time for the reactions to complete in the burner, Turbulence to increase mixing and the chances of an oxygen molecule to meet the fuel and Temperature to provide the energy to dissociate the molecules and facilitate complete combustion.
  15. If by burn you mean a fast oxidising process giving off heat then there are many instances of this where there is no flame. A flame is an area of combining gases and from that one can deduce that most flames from a woodfire will be secondary combustion. So yes if you allow fuel gases out of the stove/fire and up the flue then they can burn on top of the chimney pot when they meet air. The conditions would have to be right though and this means either some sort of flame holding or temperatures above the auto ignition point. I posted a little while back about a blue flame on the pot from CO being produced in a chimney fire. In the absence of high temperature or flame holding, then you need something to drop the temperature threshold at which the reaction can take place (actually you can add a support fuel but that;s even more wasteful). This is what a catalyst does. Thermal oxidisers for reducing organic smells from factories or waste treatment facilities seem to be surface effect combustion using catalysts. I think the videos show a rather simple effect, the before smoke is black, implying lack of air in the fire, the simple solution is to add more secondary air at the stove. I cannot see further oxidation taking place above the stack without it getting very hot and this would imply a colossal waste of fuel. The other thing is the device is shown above a chimney pot that already has some sort of air entry at its base. If this device does do any good it's to do with controlling draught rather than any combustion effect. The smoke indications are fairly simple: If you see white smoke it's small droplets of condensed vapour, mostly water but if the fire is hot but smouldering then some pyrolysis products as well. As it turns yellowish then you are getting pyrolysis products probably with some Products of Incomplete Combustion. Brown to black and you are sending lots of PICs up the flue because the hot fire is pyrolysing the wood and the products for this are starting to burn in a secondary flame but are starved of air. Looking at the flame it will be purpley near the tip and tailing off into black. As the air conditions get better the sooty PICs decline but are still emitted as a blue haze. Even with a good air supply it's difficult to do better than this with wet wood and natural draught because the flame is being quenched before it can complete. No smoke indicates good combustion temperatures but not necessarilly complete combustion as a lot of CO may still be present. I see there has been another death from CO poisoning from a barbecue left near a tent door which shows how insidious CO poisoning can be. The dangers from burning charcoal are exacerbated because all the normal warnings from woodsmoke, the acrid smell, are missing.
  16. What worries me about these, compared with asulam (which I thought some consortium had got a special licence for continuing special use) is that the bruising will be done in the nesting season, their site shows heather and the three main indicator species are all ground or near ground nesting. Mind when we were motor manual harvesting just the rolling of car tyres favoured grass over bracken for the season. I once attended a lecture by a bracken "expert" he reckoned he had sample plots that had been cut for 18 years and still bracken persisted.
  17. No but most treated softwood is done badly. The stake fails and gets abandoned or worse burned. At least chestnut degrades gracefully. Old chestnit fencing is also good firewodd as though it dries slowly it resists re wetting, so the above ground bit remains dry. I'm burning some old pales at home now. Surprising for a May bank holiday. I reiterate charring is likely to reduce the life of the stake.
  18. Heath and the populations it supports is globally rare, as are bluebell woods, just a band in northern Europe. Would it? In SE England it would be predominantly pine for centuries and this is a species that hardly was planted before the Jacobite era. It had been displaced by broadleaves a few thousand years before. Different species and that's what biodiversity is all about.
  19. Whilst it's true char is recalcitrant and resists rotting, and that's why it is a good candidate for reverting atmospheric CO2, it is also porous and shrinks tangentially and radially by over 10%, depending on heat and species, this means fresh wood is exposed to microbes via cracks.
  20. With or without butt plate? Would a loan suit?
  21. Given the same ply rating I think radials beat crossplies for most things, like economy and grip There is one advantage of crossplies and that is they withstand sidewall damage better.
  22. I made a cheap one that differed slightly from this in that I used a ford coundty wheel with a bush in the middle. A length of car exhaust wass free to slide in this and air from an old cylinder vacuum blew down into a hole created by boring with a saw. As it burned the pipe fell to the soil beneath. Trouble was it took quite a while to burn and stump gobblers were readilly available by 1984. Also fires in general were frowned upon by then. The big dead pine stump it was most successful on gave the householder a fright as we left it running overnight and he was awakened about 4:00 by the noise of a roaring jet and an orange glow filling his room. There was a long flame from the flue ( I had no termination on it and the plastic hose attached to the exhaust pipe was reduced tothe helical wire reinforcement) by the time we turned in to work the stump was gone, even tunneled out some laterals. The soil had turned from grey bagshot sand to red which I guess was the iron in the soil changing valecy.

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