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Modern drying schedules of timber buy in Ufa
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Modern drying schedules of timber

Modern drying schedules of timber

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Modern drying schedules of timber

In Russia in stage of universal implementation there are press and vacuum drying tunnels of PVSK, for qualitative wood drying with heating of stack flat electric heaters in the contact way of transfer of heat to the heat carrier. However the problems connected with complexity of management of process, use of vacuum low specific energy costs on drying set tasks whenever possible of their successful implementation in woodworking productions. In Europe and America use of cameras of this kind, were implemented still in the early eighties.

Wood drying - difficult physical and chemical process, and quality of product depends not only on final moisture content, but also on the course of process. Extremely important in the course of drying and heat treatment to avoid formations of microcracks, i. e. evacuation of intracellular moisture has to happen without destruction of cage. Drying happens to temperature increase in vacuum according to the schedule in which protection against boiling, the periods of boiling of crude acetic acid and decomposition of furfural at heat treatment is put. In the course of drying water releases cavities which under pressure of press are rumpled therefore the drying coefficient in the camera PVSK is higher and the effect of obstruction (preservation) of surface layer of wood is carried out by products of disintegration of polysugars.

In order that without difficult laboratory researches to reveal this effect, during practical operation of cameras PVSK not only surface consolidation of sawn timber but also reduction of volume on thickness exceeding real drying on the 2 - 3rd have been noted.

Results change of parameters of material of wood of pine when pressing preparation in the tangential direction are presented on fig. 2 - 4. The period of mechanical impact on sample has one order with times of relaxation of tension in structural framework therefore the effect of delay of deformations is essential. Apparently from fig. 2, in the observed period at step change of loading elastic deformations give approximately half contribution to the general final deformation of particles of wood under the surface transferring pressure. Comparison of curves 1, 4, 5 allows to draw conclusion on small influence of heterogeneous distribution of humidity on extent of pressing of the studied material in the conditions of the normal temperature and fluctuations of humidity of material within 5% . Final extent of pressing of sample practically does not depend on the modes of the appendix of loading (if the influence period by force with the maximum value more, than time of relaxation of structural skeleton). However calculations show that gradual loading promotes material consolidation, more uniform on section. For example, at identical extent of pressing ( - Y/a) the relation of volume maintenance of firm phase for the points taken in the center of sample and pressure surface near the heater plane, the most part of time is closer to unit for the 2nd and 3rd mode of loading, than for 1 (fig. 3). In fig. 4 distribution of volume maintenance of firm phase (woody substance) on cross section of sample in different timepoints is shown. Prior to process the sample had higher content of firm phase in drier border zones. The central zone which was more humidified had smaller 3 values. At preparation compression this area is deformed more intensively, than the areas located at surfaces of heaters, having smaller humidity that leads gradually to the bigger maintenance of firm phase in the center of sample. I will note also that at press surface consolidation of wood is higher in comparison with zones at wood sublayers.

Thus, the numerical analysis of mathematical model of wood pressing shows that, changing the mode of pressing it is possible to influence uniformity of distribution of firm phase in the received material.

During thermal modification there is task not only to receive dark color, but also not to lower strength characteristics of wood. Conclusion is obvious: the wood, the lower it durability is more dark. In the camera PVSK predrying of the sawn timber subjected to heat treatment as uniform process is used. It is not recommended to use wood after convective drying (the effect of stratification is observed) since moisture leaves wood crossing fibers from the center of board to its surface, and in the camera PVSK water moves lengthways on fibers and leaves sawn timber ends and there is no effect of stratification. Process of color schedule is regulated by time of decomposition (gumming) of crude acetic acid. In order that for itself to be convinced of three main properties of the thermoprocessed wood (moisture absorption reduction, dimensional stability and resistance to rotting) it is enough to make simple experiment with immersion of sample of the thermoprocessed wood in capacity with water and to measure its weight and the sizes before immersion (for the correct experiment the sample needs to be held in water of 5 - 7 days and then approximately as much time to allow it to dry at the room temperature). Results can be compared to similar measurements for the same sample from the wood which is not subjected to processing. If to place the samples (processed and raw) in different tanks with water, then in 2 - 3 days it is possible to notice that water in which there is normal tree has considerably dimmed, and by the end of experiment at all in it the mold, at the same time water in which there is the thermoprocessed sample can be got will keep the absolute transparency and by the end of "experiment".

The new technology of receiving nanocomposite of wood in the course of vacuum drying, impregnation and processing has been tested in vitro in 2010 after improvement product samples on the PVSK - 3TP laboratory commercial plant have been received. The new technology allows to make in the course of drying impregnation with the subsequent processing, and also in passing to take "extract" from the Siberian larch - raw of arabinogalaktan and digidrokvertsetin [1,4].

This statement is fair for saturants on liquid (for example - water) basis, capable in processing (for example - vacuum) to get on full depth into beat with the subsequent education in substance nanolayer time. One of such substances can be, for example fire - retarding agent [4,5]. The photo of cellular wall of wood of fir under electronic microscope with the resolution of 1: 1350 after processing by Diafos - 50 fire - retarding agent is presented on figure 6. Depth of wood processing depends on the set parameters of processing and reaches 20 - 25 mm from surface that it is enough for full processing on the required full depth of separate edged board 36 - 50 mm thick. And what if to impregnate with vanadium?

One more principle of elastic waves, is applied in the new camera PVSK - TP

It was succeeded to deal with physical essence of the field of elastic fluctuations in firm environments as a result of experimental detection of number of new, unknown earlier physical effects and the phenomena, one of which is the effect of the acoustic resonant absorption (ARA).
The effect of ARP is that at normal sonic test by harmonious signal of the plate having h thickness, at f0 frequency the part of the probing field is reoriented so that is reradiated by this plate in orthogonal (rather primary) the direction through the end faces. Communication between f0 and h is expressed by the following ratio:

f0 = Vsdv/h, where Vsdv - the speed of cross (shift) waves.

Frequency of f0 is the own frequency which characterizes the harmonic damped oscillations resulting from shock impact on h thickness plate resonator. That is that oscillatory process which was always perceived as hindrance at allocation of echo signal is, actually, spectrally connected with the extent of prozvuchivayemy object, and, so, can be used, in particular, when drying sawn timber.
It is easy to notice that is higher and higher told significantly disperses from the standard approaches to kinematic characteristics of longitudinal and cross waves. But and really, for a long time it was necessary to realize that it is illegal to characterize any type of elastic fluctuations by parameters of shift of the fluctuating particles in elastic wave, at least, as today just there are no facilities allowing to evaluate these parameters. Neither for amplitude of shift of the fluctuating particles, nor for speed or acceleration of their shift, for mechanical tension in elastic wave - sensors do not exist. Statements about suitability of any geophones for registration of this or that type of elastic waves are for the same reason absolutely illegal. That is concepts of longitudinal and cross waves have arisen is purely speculative, and were not supported with results of measurements.
In the light of consideration of properties of the field of elastic fluctuations taking into account effect of ARP it already also loses the relevance. Now it became clear that all signals having appearance of the fading harmonious fluctuation were created as a result of excitation of the relevant wood structures and transitions tree metal which have shown properties of oscillatory systems. And it does not make sense to attract to their description any type of elastic fluctuations.
When the point of view offered in the real work is standard and will be considered to be real part of the field of elastic fluctuations as longitudinal waves, and imaginary cross, also properties of the substances known under these names will be reviewed today. So, the legend that cross waves do not extend in liquid and gaseous environments has to depart in non - existence. And it is valid, as shown in work/1/, under certain conditions resonators (on cross, naturally, waves) form also in these environments. And, at last, about the reasons it is inexplicable low attenuation of signals in some cases. Without pressing here in particular, we will note only that as signals form imaginary "shock" part of the field, it is impossible to demand execution of conservation law by attenuation consideration. Practical tests were carried out in the camera PVSK - 3, resonator volume 3500kh1500kh500mm. , at frequencies of 50 and 200 Hz. , vzbuzhdayemy resonator of the vacuum pump.

It is known that the more compressibility of working environment, the is higher efficiency of transformation of thermal energy of the environment to mechanical work. In thermodynamics of two - phase flows accounting of property of the increased compressibility of the environment in two - phase flows is new. Property rather well - known to the specialists working in this area, but exclusively seldom used by them practically for the purpose of optimization of processes power - masso - and heattransfer. This main feature of two - phase flow has also formed base for development of the new direction in thermodynamics.

Steam flow at the exit from the camera has the speed equal or бόльшую the local speed of sound. The camera of drying is the heat exchanger (massoobmenniky) mixing type. As a result of exchange of the number of the movement of working bodies in the camera of drying does not become homogeneous and the speed of sound and elastic waves is transferred on compressed stack of wood (in metal more than 1000, in water is one half less, and in steam - gas and bubbles absolutely small) in the contact way. Therefore the bottom dries quicker. Thanks to the fact that the flow at the exit of the camera possesses very developed surface (it has either foggy figurative, or penno figurative structure depending on ratio of steam and water phases), the pumping device sizes repeatedly мéньшие in comparison with any heat exchangers of surface type (including lamellar) where it is possible to extinguish sound wave.

There was a wish to mention "green chemistry" as a part of which wood rectificate there is turpentine, methyl alcohol, acetone, etc. combustible substances separately. In the camera PVSK at certain temperature, exhaustion and the catalyst of oxide of aluminum with acetic aldehyde, perfect natural fuel turns out. When drying 1 cube of pine, about 20 - 30 liters of "combustible liquid", (5 cubes - 100 liters of fuel) which can be used as fuel for diesel units, power - saw benches with the diesel engine, diesel electric generators merge. Thus on "waste" it is possible to continue drying in any place without additional energy costs from own electric generator using own fuel, THIS ENERGY SAVING AND ECONOMY! ! ! .

In woodworking the concept "humidity" is used - it is the mass of water divided into dry weight.
At determination of humidity of fuel use the concept "moisture content" - it is the mass of water divided into the mass of wet fuel.
The relative humidity is the relation of amount of water to sample lump.

Absolute humidity - the relation of mass of water to the mass of absolutely dry substance of wood.

In production timber industry affairs the relative humidity is always used. Absolute humidity is applied in laboratory researches. Hydrometers are graduated in terms of relative humidity too.

Proceeding from above stated, I recommend to use hydrometers (needle) of the konduktometrichesky principle, but not the consignment notes working by the principle of densitometers.

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