openspaceman

I definitely second that.

I know where you're coming from and @Woodworks is saying much the same but here in Sunny Surrey I was pulling softwood from my log shed in the low teens , I've very little left to test but I'll look to do a test. Yes but as I mentioned some posts back the equilibrium moisture content verses relative humidity is not a line but an area bounded by two ogives, one is the path the drying takes as timber dries and the other as it readsorbs moisture, I have found an image from a research paper on mahogany as an illustration, so it is to illustrate the principal only: Equilibrium moisture content of mahogany wood as a function of relative humidity at 25°C. Filled and open symbols correspond to the adsorption and desorption states, respectively. If you interpolate using 90% RH as the average maximum humidity a log will experience in the middle of a stack ( given that it takes time for the whole log to reach equilibrium) you will see it settles at 16% mc but the same log being dried from green settles at 19%. Again there is the problem is that the basis on which the moisture content is being measured is not stated. What it means is that the water from 25% down is weakly bonded to the wood structure and energy is needed to release the water molecules from that bond hence the drying line is higher than the wetting line.

I possibly have not followed whether the tipper motor and ram were both transferred to the vehicle. If they were the heaviest loading would be when the pressure relief blew off and at this point the motor would be struggling and running slower and taking a higher current but no more than when on the other vehicle. On most of these electric-hydraulic pumps the spool valve and relief valve are built into the motor pump unit.

Fairy nuff I'd missed that but the OP hasn't said where the 700 degree temperature was recorded, I can easily reach 700C in a bed of glowing coals but agree a flue temperature that high would make the steel glow bright red.

It's ill thought out but it must be aimed at garage forecourt and garden centre sales. It may push people to buying from reputable log sellers. There has always been legislation about smoke and I've never known of it to be prosecuted for domestic fires, or generally other fires. I'll cite non smoking as being a successful campaign where legislation was used after education and peer pressure had made it unacceptable in restaurants (public transport bans preceding this). Then we have the dogs fouling of land act and its successor, a masterpiece of ill intended consequences, while I'm glad the verge outside my house is seldom fouled I am incensed by poo bags in the countryside where I would prefer to see the shit.

weigh it. I cut a piece as near under 30g and weigh it on a postal scale, note the weight and stick it in the microwave for 1 minute. note the weight let it cool a bit if it is steaming and repeat until you observe no further reduction. that stable weight is then the oven dry weight and it should pick up a gram or so over the next few hours. The original moisture content is the original weight minus oven dry weight divided by the original weight.

Have you turned american most, even oldies like me, have grown accustomed to using SI units.

I've not got anything against the idea, after all all modern gas boilers have a balanced flue to do this but you need 4 or 5 air changes an hour in any case so using air from the room just ensures some of this.

Graphs like that don't tell me much without a bit more context. Even so the green band of the curve seems to have been selected arbitrarily and doesn't indicate much reduction below 25%. When Tom Reed told me that 12% was optimum it made no sense to me, after all petrol and diesel have insignificant water content and burn with low particulates, alcohol burns with low particulates and it is partially oxygenated like wood. I'd love access to a lab to investigate stuff like this but I do have a few observations from my own fire. One is that if the fire is hot but turned down fairly low with a bed of hot char and I reload it with a couple of big medium sized logs without altering the air control after a few minutes the inverted flame from the air bleed at the rear middle of the fire quickly fill the firebox. I can go outside and see a faint dark haze from the fire. This I know to be because the secondary burn is too rich. The solution is to close the air control till the bleed air can "catch up" with the offgas being produced as the hot firebox pyrolyses the logs. The evolution of pyrolysis offgas has exceeded the ability of the air supply to completely burn it. I can also crack the door open to allow a supply of secondary air but this simultaneously supplies more primary air and causes the power to shoot up.This does not happen with damper logs because the energy needed to evaporate the water damps down the pyrolysis. I can see exactly the same if I put a piece of birch on in the same conditions, it's like throwing a plastic wrapper on, the air supply cannot keep up with the evolution of gases from the oily bark for a short while. In practice it's not a problem because it means the stove is already producing 4kW and doens't need reloading yet and then only a piece at a time.

Why should there be? Most of them will be specified for G30W30 and the power stations were accepting 45%mc. Mind on the installations I worked on which were supposed to burn G30W30 I never measured a sample drier than 40%. The thing to remember that it's not dryness that decides how clean wood burns its the combination of the time the wood and offgases have to reside in the fire, the turbulence that causes mixing of the gases and the temperature the various species of chemical produced in reactions are subject to. A big installation can satisfy all these ans still burn wet wood, a small domestic stove cannot.

I find with my Morso that if the door catch is not pushed in firmly it sucks air past the door seal which makes the fire run away. With the modern stoves there is an air inlet above the firebed which is permanently open, this is so there is always enough secondary air to burn any offgas from the fire in a clean flame. In older stoves you could choke off all the air and the heat in the firebed would pyrolyse any remaining logs, the offgas then condensing as tarry soot on the glass and chimney.

I see the Lucas mill I did some help with is listed at Petersfield. Run by Frank Spooner and Tom Hartley, good lads but I've not seen them working.

Syngas doesn't form at less than 800C and then it will be too contaminated with other products to be syngas with wood as a rawstock. The portmanteau word comes from synthesis gas which was fairly pure H2 and CO used to form other more useful organic chemicals, like petrol, from coal. Below about 330C the whole thing is endothermic and the early products are highly oxygenated so no good as a fuel, You have to be up in the 300-440 range for pyrolysis to be self sustaining and give an offgas which will support combustion, in the absence of a support fuel. You can use the exhaust from a spark ignition engine to pyrolyse wood but then it is difficult to keep a flare (necessary for controlling smoke and pollution) We heated wood in the output of a vegetable oil gasifier and fed the offgas to a small gas turbine but only ran it briefly, long enough to produce nice logwood charcoal though. Ideally we would have liked to heat the wood with the turbine exhaust and then dry the wood downstream from that.

This is the main point and why most firewood is hardwood. In point of fact softwood has more energy per kilo than hardwood at the same moisture content. It has a higher initial moisture content than most hardwoods and tends to be 30% more bulky. I burn whatever comes out of the woodshed as it comes out. I fill it with what I bring home in the back of the vitara off jobs whether hard or soft but tend to not bother with willow or poplar because they take up too much space.

it's been nigh on fifty years since I did any courses on electrical engineering but it depends what type of generation you are meaning, as I said the average losses between generator and consumer are 7+%. Most coal fired station back then were high temperature steam turbines and managed a bit less than 40% but the generators had low operating and maintenance costs. Some standby plants were diesel and had better thermal conversion efficiency but high O&M costs, then there were peaking plants which cost a fortune to run, often open cycle gas turbines based on early jet engines, at a time when the consumer paid 7p/kWh these cost about 50p/kWh to run. When the internal fire museum acquired one of these after 30 years in service, from Princetown IIRC, it had only a few hundred hours on the clock. Nowadays the best combined cycle gas turbine sets, which supply the bulk of our fossil fueled power manage just short of 60% thermal conversion efficiency. We still get about 15% of our power from our nuclear power (plus quite a lot we import from France which is mostly nuclear powered) and these have a lower thermal conversion efficiency than coal fired as the boilers are run more conservatively . That's a marketing thing, power generators pay way less for gas then we do and most of their costs are in sales and distribution. I currently pay about a quarter of the price of a kWh of electricity for my gas but they do different jobs.

It's a simple economic proposition, if the dried wood attains a higher price in the market place than the cost of the drying, the heat source is immaterial. Anyway the waste from a logging operation probably amounts to over 5% of the raw material so burning it for a kiln makes sense. Actually about 15 years ago a government agency was burning gasoil to dry wood for Tilbury power station in order to get renewable Obligation Certificates and that was naughty. I wonder how much sawnwood kilning requires in the scheme of things, obviously I think it should be done with sawmill waste. It's a bit of a no brainer but there's good reason to use waste wood at the point of production in any case where its heat can be used. I agree with the first part and think I can answer the second; power loss in the grid and distribution runs at about 7.7% but this shouldn't impact any consumer as the voltage will be maintained at the substation, any circuits further from the substation will tap the transformer at a higher voltage to make up for losses.

I'd need to see some figures for particulates per MJ of heat at various power settings released before I'd accept there were benefits in wood this dry. From what I remember wood at 12% mc wwb can be burned the cleanest but it's not BATNEEC

I'm sure it is and equally sure it stems from use of high moisture content wood and the habit of turning down the fire to "keep it in".

Firstly I am a fan of using the natural drying processes, especially making use of the greenhouse effect of a transparent kiln but I did conceptualise a high temperature kiln which we built for a supplier of firewood. I still think this is a way forward but making more use of waste heat. Not necessarily, and as has been pointed out we use little coal for electricity. the effluent from a coal plant can be cleaned and because it is running constantly the thermal conversion efficiency is optimised. When the electricity is used to charge a battery and then discharged to drive a car's motor I guess the conversion from power station to wheel is around 70% and is fairly constant. Whereas a IC engined car is operating at lower efficiency overall unless at constant speed.

I was thinking more of IBC crates or potato boxes, I have no experience myself as I cut split and stack mine by hand for my own use and seem to have no problem getting them dry enough in a summer season. When I sold logs 30 years ago they were nowhere near 20% but then it was common to see a wisp of blue smoke from chimneys, a lot has changed in pollution awareness since.

Ok but for extraction 2-3m is better so an extra cross cutting will be needed another operation and another Easily enough over a summer to get dry, much better if under a roof, in sections as small as that, not so in the round. Another operation How does that compare labour wise to processing freshly harvested wood to size and dumping it into ventilated containers in one hit, moving under a roof, preferably transparent, and then taking them from store and delivering them in one hit?

The quote @Paul in the woods gave shows the reasoning. I have mentioned it before in relation to how moisture meters are calibrated. @Stere I don't know but have always suspected they are calibrated on a dry weight basis, I don't have one but I suppose I should get one to check. In practice the dryer the wood is the nearer they get to the same reading. @Woodworks the page you quoted has this example "(For example, if a piece of wood weighing 100 kg contains 50 kg of water, the moisture percentage is then 100%)". The calculation of 50kg moisture divided by 50kg of oven dry weight giving 100% mc shows they are using a dry weight basis, it would be 50% on a wet weight basis.

I'm glad you found that, it confirms that the equilibrium moisture content tables you are reading are based on the moisture content on a dry weight basis so if we take as an example for you of 90% RH and 10 degrees C from your chart that gives an equilibrium moisture content of ~23% dry weight basis, which is a moisture content of 18.7 on a wet weight basis, quite a bit under the 20% target.

it's a variation of Parkinson's law which says work expands to fill the time available, in the same way if you fit a bigger bookshelf you will buy more books. I saw this when I started driving, many folk still had no cars and the local factory workers mostly bussed, walked or cycled to work. Once cars were common people would compete for work further than 5 miles or so, then the M25 was built and it became feasible to commute a few towns away, so my schoolmate took a job in East Grinstead which had been a 2 hour trek but was now 55 minutes and it was his time (and higher pay) which were the considerations rather than fuel consumption.

What worries me about this chart is that woodworkers and joiners generally use moisture content referenced to the dry weight of wood, for burning we usually reference the wet weight of wood and I cannot see on this site which moisture content they are using. So for instance if we have a mass of wood which consists of 20kg of water and 80kg of oven dry wood then a joiner might say that's 20/80=25% mc dry weight basis whereas I would say that's 20/100=20% mc wet weight basis. Also there is a hysteresis so as a log regains moisture content at a given RH and temperature it tends to maintain a lower moisture content than the same wood being dried in the same conditions. It is of course in the ballpark of gnat's piss but laws do need to be precise. BTW does anyone know how this 2m3 is defined, is it a bulk load or solid wood?