openspaceman

I cannot help with costs, they belong to firms I do work with. The quadtrack wasn't liked as it didn't feed as well as the others, appeared to have a high CofG and seemed a bit flimsy for the rough and tumble of utility arb. Service and back up from both firm's is excellent but getting spares for the greenmechs is a hassle.

You mean the TR6? Now that the teething problems have settled down it seems to be well liked. I have only used one for 30 minutes but the lads rate it. I do like the Jensen spider though, it has similar controls to the Forst, and I think it's better than the greenmech 1928s but possibly not as good as the bigger older 223?? for ground capability,

Yes I think it has to be wrapped in plastic and buried back on the site it came from. Otherwise it's to go to a licensed site and they charge separately for the estimated plant content and a lesser amount for the soil, as this does not have the landfill tax because it's inert. There are cases where the soil has been sterilised in situ with steam and also by being excavated and heat treated but I've never found out the results. It was a field I tried to get involved in but didn't get antwhere with the big waste companies.

Steph, I doubt many toxins survive the high temperature of a clean burning furnace, Products of Incomplete Combustion ( soot and smoke) do tend to have carcinogenic properties and are implicated in acute repiratory infections (the major cause of infant mortality in households cooking with wood in the undeveloped world). This is how smokers contract lung cancer, the sooty particles are small enough to embed in the lung tissue. Also woody biomass has a fairly low mineral content and little heavy metals. So whole tree woodchip is cleaner than most coals to burn. What is true of bark needles, leaves and buds is that they have higher moisture content and higher ash. Therein lies the problem for a hot furnace, because 50% of the ash is species of compounds derived from the alkali metals, Potassium, calcium and some phosphorus these end up on the grate or in the flyash ( most phosphorous compounds leave as a gas so I doubt they feature in this problem), they have a strange property in that they lower the melting point of the remaining silica in the ash. This is similar to glass making where soda is added to sand to make it melt earlier. Now this fused ash causes a few problems, one it oozes over the grate and blocks air passages as clinker and the other is that it is carried as droplets onto the heat exchanger surface where it sticks to them and cuts heat transfer. This is more common on furnaces burning agricultural residues, like straw, which have much higher ash content. There are a number of fixes for this but the pragmatic one is to use crude technology and put up with the problems. This is why in the rush for NFFOs 20 years ago Fibrowatt invested in 1940s steam ship boiler designs for their power stations. Apparently one could see the slag dripping off the superheater tubes. I think it is also the reason the advanced fluidised bed design at Slough Heat and Power was often broken. As I said the green bits do contain the trace elements but chlorine is not significant (other than in certain agri residues like beet pulp IIRC). Whilst it sounds like chlorophyll contains chlorine it doesn't. The words both drive from the Greek for green. Chlorophyll is an organic compound whose structure is similar to haemoglobin ( the compound which carries oxygen in our blood) but with a magnesium content rather than the iron in blood. Whilst burning biomass is a major source of dioxin in the air I think this is from open fires and particularly seasonal burning of grassland rather than burning woodchip. Generally I don't think stoves and boilers emit much and they don't get hot enough to synthesise dioxins from mineral salt on the timber i.e. dioxins are most likely formed by incompletely burning an organic compound containing chlorine, PVC and neoprene being common culprits. This sounds like slagging but you have also identified one of the problem of fines in the woodchip, it blocks the interstitial spaces which the primary air needs to get through to pyrolyse and gasify the wood on the grate. This also causes hot spots where newly formed char then burns out at 2000C rather than gasifying to CO at 1100C. So the grate gets hot enough to oxidise and the ash liquefies producing the slag that interferes with the grate. Yes it's composting which is a form of slow combustion, as John says the spores can be a health hazard plus of course you are losing calorific value. In the days when we had big chip stockpiles for paper making it would be compacted by dozers in layers, like silage in a clamp, to squeeze out the air spaces. You'll need to get the chip down below 25% and probably as low as 17% to stop these moulds working. To some extent the heat from the composting will carry other moisture away with it ( aerobic composting turns the biomass to CO2 and water vapour which rises as a saturated gas, I've never done the sums but this CO2+H2O can probably accommodate more water as it rises through the heap. Some of the conditions will be anaerobic and methane will be given off. This is why some wood chip heaps are covered in a fleece, it keeps the surface warm, so water doesn't condense and run back into the heap and allows vapour through but is not permeable to rain or dew. From the little I hear now they have limited success. Apart from forced drying the best bet is to chips after a summer drying in the round. Arb arisings have to be chipped and transported green and my first move would be to screen it to remove fines <2mm and the longer >100mm if I could figure the economic means to do so. Arb waste ship also tends to be poorer quality with jagged edges and this combined with the mould means the angle of repose in a silo can be negative, the silo looks full but there's an empty cavern over the sweep auger. My virtual friend Alex addresses this problem with innovative reciprocating wall and travelling augers for his feed system.

I think 9 probably allows for air space, trolleys and passages. There is no ideal, it's down to heat source, air movement costs, time. I think your figure is to do with kilning lumber without degrade, this does not matter with firewood, although sweet chestnut does shatter at higher temperatures. Easy way to check is with an electric oven, set it to your desired temperature and put one log in, you'll need to get it out and weigh it frequently which will aslo ensure enough air changes but my guess is that if the oven is set to 70C to allow loss of 10C from your heat source you will barely do it. Consider that you have to do two things, deliver enough hot dry air to the surface to evaporate water and get heat into the middle of the log to get the water there to move, it's this last bit that is the problem. A sycamore woodchip will dry in 2 hours at 40C in dry air but a 6 inch log will take a week. 12000 @ 50% means 6000kg water and 6000kg oven dry wood 7500kg wood at 20% contains 1500kg water you need to remove the difference. 50kW is already a rate of energy use so the per hour would be a rate of change of power. Your numbers are OK but you haven't allowed for the time taken between delivery of heat to the wood surface and that heat getting to the wet core and migrating liquid to the surface. They would wouldn't they (paraphrasing Mandy R-D). Commercial operators won't concern themselves with the workings, they'll look at the "box", cost the inputs and price the outputs and see if they can sell that at a profit.

It was the expansion under constant pressure that he was looking at, to reduce shock loads. Though he considered coal dust and some sort of lock hopper I didn't think he used it, opting for peanut oil instead. I think Sulzer went into production for him first. He was using an aerosol ( compressed air) to inject it and this robbed some of the volumetric efficiency. I imagine this was because high pressure liquid pumps were hard to make and maintain. Again this problem of injection into a high pressure was one reason for the use of semi diesels, particularly in boats. Internal Fire museum in Wales is the place to look at some of these early designs and Paul can talk one through all the developments.

6metre container 2.4 by 2.4 outside, what inside? Say a usable 28m3 at <50% stacking ratio as the stillages have worse edge effects, so at best 14 solid, in practice we only achieved 18 solid m3 in 12 metre container. Why this choice? OK but it means you have delta T losses across two heat exchange surfaces. ..and do what with this low grade heat, the humid air will be less than 70C and yet another delta T loss across the heat exchanger, you'll be lucky to recover it at more than a few degrees above ambient. Even power stations dumping heat to a cooling tower just vent it. How do you arrive at that? Sensible You need to redo your sums, to reduce 12000kg of 50% mc wwb to 20% you need to take out 4500 kg of water and at 75 degrees this will need around 0.65kWh of heat per kg of water, best you might hope to achieve is a 50% of you heat input even optimistically you have to deliver 5.85MWh into the kiln plus losses through the kiln surfaces. You need a premium market to justify the capital and O&M costs, can be well worth doing if you have a commercial bent.

We agree I disagree, it's a comparison of it's resistance to auto-ignite, the spark still ignites it and the flame front then runs through the mixture. A low octane rated fuel will reach it's autoignition point from the heat caused by the high pressure developed in front of the flame. This detonation causes a sudden rise in pressure which can damage the engine. The ideal is for the flame front to progress quickly through the mix and then the hot gas pushes the piston down. The opposite is true of diesel which has a low octane rating and a high cetane rating, this means it burns at a fairly low temperature but as the diesel is sprayed in over a few milliseconds the pressure build up is controlled by the rate at which the fuel droplets are burned. Oddly Rudolph's aim was to counter the shock that spark ignition engines suffered with poor fuels by introducing the fuel gradually rather than premixed. I disagree, the flame speed will be the same, it could possibly burn cooler (as you say lower calorific value, but this could be down to the weaker mix). Agree Actually high leaded fuels did have an advantage for 2 strokes if they overheated or the petroil mix was lacking oil, they ran a bit longer before they seized.

Why? Ethanol has a higher octane rating than any petrol. Generally the higher the octane rating the lower the calorific value. That's why a JAP 500 grasstrack bike had to have 40% bigger main jet. Engines are better designed nowadays, so a cooking 4 stroke motorbike engine then would typically have a compression ratio of 9.5:1 and a carburettor that was always near enough right. Hence a pre disposition to pinking (detonation of stagnant fuel:air mix in advance of the flame front). Better control of fuel:air mix, better mixing better turbulence (squish) in the combustion chamber means a 9.5:1 engine can run on 95 octane rating. My wife's MG only gets 95bhp out of 1800cc, pinks on anything less than 99 octane rating and is outperformed by my pug 206 diesel. Generally compression pressures are lower in 2 strokes as the compression doesn't properly start until the transfer ports are closed, so 2 strokes traditionally work on lower octane fuels.

I agree but it's quicker to tip a load of chips than unload cord. Also no need to strap the load down. Cord is cheaper to dry in stack without contamination.

These people were always a help to me when they were just off the A3 Briggs & Stratton Engines years back I got my Enfield spares from the sister company

It's not so much the wood that's burning hot, it's that the wood at the grate has turned to char, this them reacts with primary air to get the high temperature which heats the grate. Even then the grate doesn't melt, it gradually oxidises. That's why a cast iron grate lasts longer, the sites for oxidation are filled with little graphite crystals which protect the iron. The grate is cooled by incoming primary air. As you say, dry wood doesn't need much primary air because it has a far higher volatiles content than a coal fire. Little primary air means little cooling effect.

What will be interesting is to see a photo of the crossection to see how the two fungi have walled each other off.

You have made your decision but I wondered if anyone cared to debate the surmountable problems of burning chipped arb arisings domestically. Capital cost is the issue. I said that moisture content was the major problem but talking to Farmer Rod today he pointed out that dry woodchip can get so hot on his grate that the ash actually melts and fuses to the grate, something I'd only seen on small burners using coke.

This has been said ever since I can remember chippers being used, that chips will become a scarce commodity and that too many woodchip boilers with cause the price to rise. It has never really happened, though it still might. At present in the SE there is a glut and few firms are paying for wood to chip. Those that do seem to only want round wood that has seasoned in the stack for their woodchip customers. Many of the small arb firms' yards that I am aware of are not accessible for Stobarts 44 tonners. The prime reason for an arb firm chipping wood is to reduce the size of the heap (increase the bulk density) and simultaneously load the truck. They do not aim to produce a nice chip like an angled disc chipper does and they want it to keep loading when the knives get a bit blunt, which again reduces overall chip quality. Incidentally chipping all the branchwood reduces bulk density compared with separating cord wood out and loading it separately, the trade off is ease of loading against vehicle capacity (rather than payload). We could discuss why this unsuitability for stokers is the case, I guess most will realise that arb arisings contain leaves and needles that push up the moisture content but there are other things about them that need to be considered when used in a chip stoker.

How have you calculated this? Capital plus O&M plus cost of wood? Do you mean for travelling on the road with timber or on your own land? 50 tonne/annum work would keep an old County from rusting up.

The Kob I quoted cost £300k plus quite a lot of snagging to rectify feed problems. It had a 10k replacement sweep auger 6 months before the system was sold. BTW as my chip stoker has not enough load I just fill it with a broken pallet and some arb waste logs, that heats the 3tonnes of water up to 80C in 2-3 hours .

If you have logs and the accumulator then I don't see much advantage in going to chip unless you have a large silo, even then do you need a system that you won't attend daily. Of course even automatic chip stokers need de ashing and tube cleaning so they are not labour free in between fills. The chap who has my 10" TP on long term borrow successfully ran a little 70kW Baxi and a bigger one whose name escapes me, all on dead hedgerow elm. Now he runs a big biogas plant so has no need of woodheat. But how much for pellets? Pellets essentially move the capital expense from the chip feeder to the pellet mill but the mill expects to recoup the investment. Last year I saw a 4 year old 500kW system by Kob get knocked down for £8k, secondhand chip stokers are cheap.

I'll need to be more careful then, anyway a few I saw last week, I wonder if it's a good year or just that I'm taking more notice now. An old boundary oak, previous years a home to hornets amongs other things, note the grass growing from an old branch wound. Inonotus dryadeus on an oak buttress between a golf club car park adjacent to a fast B road, note the old fruiting body beside. This ash with what I take to be hispidus leans from a cottage garde on a windy B road where traffic often queues to go over a canal crossing. I take it the yellow on the spiders web is spores?

Which fruiting bodies on trees have guttation?

I don't do formal tree inspections but I do site mapping, often with reference to SSSIs, TPOs and conservation areas. I use a program called mapmaker, the professional version is 30day free trial and then it loses a bit of functionality and runs as a gratis version. I find it adequate and intuitive. I have used the database functions but not much. I can layer georeferenced photos on it but for illustration I usually pin them to a KML file for viewing in Google earth. If I need a bit more detail I license a OS map for the duration of the project.

I guestimated about 10% when we were working out whether there was enough energy in the waste to dry the logs. I wanted to try something like this lifter that sold on ebay 261240252757, I used to see them at farm sales for about 8o quid in the 80s

Durham man flu coming on?

I was trying to add a bit of detail to cover problems that may arise in future. I use a private firm and the cost tends to be about £70 each visit, my local authority wanted to charge £230 for the initial registration and inspection visit, that's alright if you're having a lot done but expensive for a few windows or a stove and flue.

I'd like to visit if you intend using it with a pole pruner