CN101722554B - Vacuum-drying method for wood - Google Patents
Vacuum-drying method for wood Download PDFInfo
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- CN101722554B CN101722554B CN2009102429152A CN200910242915A CN101722554B CN 101722554 B CN101722554 B CN 101722554B CN 2009102429152 A CN2009102429152 A CN 2009102429152A CN 200910242915 A CN200910242915 A CN 200910242915A CN 101722554 B CN101722554 B CN 101722554B
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- 239000002023 wood Substances 0.000 title claims abstract description 102
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- 238000001291 vacuum drying Methods 0.000 title claims abstract description 25
- 238000001035 drying Methods 0.000 claims abstract description 132
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Abstract
The invention discloses a vacuum-drying method for wood, which sequentially comprises the following steps of: sawing the wood into wood blocks with required length; stacking the wood blocks in a drying chamber; preheating the wood blocks to a preset temperature; and vacuumizing the drying chamber, wherein the vacuumizing is realized by controlling the absolute pressure for vacuumizing according to the requirements of temperature for the wood equilibrium moisture content in different drying stages, so as to dry the wood blocks in the vacuum state according to the temperature and absolute pressure which adapts to the wood equilibrium moisture content, wherein the absolute pressure P is obtained according to the relation among the equilibrium moisture content (EMC), the temperature T and the absolute pressure P. The method of the invention enables the wood to be heated uniformly, obviously shortens the time required by the wood preheating process and the drying process and greatly enhances the production efficiency for wood drying.
Description
Technical field
Patent of the present invention relates to a kind of method for drying wood, particularly a kind of drying means of undersized log.
Background technology
According to the china natural resources situation, in the quite a long time, the raw material of China's forest product industry product development will be given birth to small dimension wood based on the speed of giving birth to the short period of felling in turn in 5～10 years from now on.In the Application and Development of solid wood furniture with the finishing field, will be small dimension wood essence, deep processing, improve an effective way of small dimension wood comprehensive utilization ratio and added value.
Because the improvement of dwelling house and living condition, people are growing to the demand of furniture, and simultaneously because the enhancing of environmental consciousness and to the yearning of nature, increasing people wishes that the living space of oneself can more approaching nature, and solid wood furniture becomes the row of first-selection.And small dimension wood is through reasonably dry and processing, supporting furniture such as chair, stool, bed, sofa and platform, a few class furniture both can directly be made into, can give full play to again, ingenious some characteristic of utilizing small dimension wood, as flexibility, taperingness, colourful forms such as circle, ellipse, semicircular section, or directly revolve the parts of making solid wood furniture.For texture, small dimension wood goods that color and luster is more attractive in appearance, can adopt transparent coating, to show the native texture and the color and luster of timber,, also be a kind of pattern of natural formation even if be counted as the knot of defective, can give a kind of cordial feeling of people; Neither pollute indoor environment, kept the timber natural characteristic again, satisfy people and return Piao and return genuine psychological needs.
But, at present owing to seriously do not limited the extensive use of undersized log at the efficient drying means of undersized log.Mostly known drying method at Logs of small diameter is to be undertaken by conventional drying equipment and technology, the arid cycle that its subject matter of bringing is not only Logs of small diameter is long, and seasoning defect drying defect is serious, as easily producing gross distortion and cross shake in the dry run, particularly the Logs of small diameter drying is difficult, yield rate is low for mixing firmly, and the dry mass of Logs of small diameter directly affects the dimensional stability by the undersized log product processed.
Prior art makes timber carry out dry method under vacuum state in research and development, vacuum drying advantage is that the boiling point of water under vacuum condition reduces, the timber internal pressure is higher, thereby can accelerate rate of drying at a lower temperature, shorten arid cycle, guarantee dry mass, be particularly suitable for the good permeability or the easy timber of shrinkage, and the drying of the bigger hard broad-leaved wood of thickness.
For example, existing vacuum drying of wood method comprises continuous vacuum drying and batch (-type) vacuum drying, the mode of heating of wherein traditional continuous vacuum drying is by hot plate timber to be heated continuously, and its shortcoming is owing to mainly by conduction pattern timber is heated, so drying efficiency is lower; The batch (-type) vacuum drying is to adopt vacuum, normal pressure to hocket in timber drying, so energy consumption is bigger.
For example, Granted publication number is for disclosing a kind of drying and processing method of undersized log in the Chinese patent of CN1046886C, this method is processed into undersized log the log profile of maximum gauge in the level of footpath, mill part by selected figure again and lack circle, utilize cutting machine to cut sth. askew into isometric segment body then along the angled end-face of above-mentioned residue section bar, each segment body sticks with glue agent according to selected figure and pieces together the whole sheet material of composition, and this sheet material periphery tightens with jig, sends into drying equipment at last and carries out the drying processing.Be characterized in solving that undersized log is difficult to dry the processing and the problem that can not fully utilize on a large scale, arid cycle is shorter relatively, and dry run does not exist end check, splitting or entire crack problem.
And for example, Granted publication number discloses a kind of vacuum drying of wood case in the Chinese utility model patent of CN2436899Y.This vacuum drying of wood case comprises casing, vavuum pump, vacuum degree control device, and we leaves the casing top, is placed with seal cover above, and heating plate is arranged in the casing, and heating plate connects recirculation heater.During use, alternately be placed in the casing with timber to be dried is parallel with heating plate, place seal cover at the casing top, open and produce negative pressure in the vavuum pump casing, seal cover recessed compressing timber plate and heating plate, recirculation heater is supplied with deep fat or hot water in heating plate simultaneously, with the timber heat drying.Is to prevent that sheet material is out of shape in dry run with this device to the withering advantage of timber, and recirculation heater continues to the heating plate heat supply, further energy efficient.But this device is not suitable for Logs of small diameter, when with it Logs of small diameter being carried out the drying processing, can not avoid the problem of its flexural deformation and cross shake.
Summary of the invention
The objective of the invention is to provide a kind of drying means of timber at above prior art problems, this method by making the drying medium convection current to the timber heat supply.
According to first aspect present invention, the vacuum drying method of timber comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages, calculating and control and wood equilibrium moisture content and temperature adapt vacuumizes absolute pressure, handles so that according to temperature that adapts with wood equilibrium moisture content and absolute pressure juggle is carried out drying at different drying stages.
According to second aspect present invention, the vacuum drying method of timber comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages, calculating and control and wood equilibrium moisture content and temperature adapt vacuumizes absolute pressure, handles so that according to temperature that adapts with wood equilibrium moisture content and absolute pressure juggle is carried out drying at different drying stages;
Wherein, the relation by equilibrium moisture content EMC, temperature t and absolute pressure p in the following formula obtains described absolute pressure p:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (1)
X=lnt, y=lnp, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝228.0686?b＝-39.151482?c＝111.51028?d＝-2.7974235?e＝23.077616
f＝-17.970629?g＝0.866796?h＝1.8109251?i＝-1.1816787?j＝1.457619。
According to third aspect present invention, the vacuum drying method of timber comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages, calculating and control and wood equilibrium moisture content and temperature adapt vacuumizes absolute pressure, handles so that according to temperature that adapts with wood equilibrium moisture content and absolute pressure juggle is carried out drying at different drying stages;
Wherein, the relation by equilibrium moisture content EMC, temperature t and absolute pressure p in the following formula obtains described absolute pressure p:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (2)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝-412.70559?b＝340.35847?c＝16.528319?d＝-84.776089?e＝4.0013776
f＝1.8420135?g＝7.0445816?h＝0.5331407?i＝0.4498705?j＝0.8659198。
According to fourth aspect present invention, the vacuum drying method of timber comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, comprising:
In different drying stages, temperature and absolute pressure are finely tuned;
Equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages obtains the pairing wood equilibrium moisture content of described temperature and absolute pressure, makes it the requirement of realistic wood equilibrium moisture content.
According to fifth aspect present invention, the vacuum drying method of timber comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, comprising:
In different drying stages, temperature and absolute pressure are finely tuned;
Equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages obtains the pairing wood equilibrium moisture content of described temperature and absolute pressure, makes it the requirement of realistic wood equilibrium moisture content;
Wherein, obtain described wood equilibrium moisture content EMC by following formula:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (1)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝228.0686?b＝-39.151482?c＝111.51028?d＝-2.7974235?e＝23.077616
f＝-17.970629?g＝0.866796?h＝1.8109251?i＝-1.1816787?j＝1.457619。
According to sixth aspect present invention, the vacuum drying method of timber comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, comprising:
In different drying stages, temperature and absolute pressure are finely tuned;
Equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages obtains the pairing wood equilibrium moisture content of described temperature and absolute pressure, makes it the requirement of realistic wood equilibrium moisture content;
Wherein, be calculated as follows described wood equilibrium moisture content EMC:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (2)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝-412.70559?b＝340.35847?c＝16.528319?d＝-84.776089?e＝4.0013776
f＝1.8420135?g＝7.0445816?h＝0.5331407?i＝0.4498705?j＝0.8659198。
Because therefore the present invention can be divided into temperature a plurality of stages from low to high to drying stage by above-mentioned equation accurate Calculation wood equilibrium moisture content, temperature or absolute pressure, thereby improves drying of wood effect.
Drying stage of the present invention can be divided into temperature five or five above drying stages from low to high.
Characteristics of the present invention are, utilize the relational expression of equilibrium moisture content EMC, temperature t and absolute pressure p, calculate the absolute pressure of taking out vital qi corresponding fast with computer with temperature, thereby can control the dry run of timber more accurately, in addition, can also in timber drying, obtain wood equilibrium moisture content, thereby help controlling timber drying according to temperature and absolute pressure.In addition, because the above-mentioned wood equilibrium moisture content equation of the present invention can be by Computing, can calculate the equilibrium moisture content under certain temperature and pressure in real time, therefore can divide the drying of wood stage carefullyyer, be that drying stage can be more, thereby the convenient timber of controlling better gets dryly, improves drying effect.
The advantage applies of the inventive method is in the following areas:
1, the present invention continues heat supply in the mode of convection current to timber by making drying medium, and make the flow direction of drying medium and the vertical consistency of juggle, comparing drying medium flows to and the horizontal consistent mode of heating of juggle, can guarantee along whole material heap section juggle to be heated more equably, promoted the transmission of the vertical moisture of juggle, therefore timber is heated evenly, and timber warm and required time of dry run have significantly been shortened, compare the existing drying of wood time and can significantly shorten, improved the production efficiency of the drying of wood greatly; In addition, the moisture in the timber vertically moves along timber, can not increase the moisture gradient of lumber thickness direction, has therefore also avoided the lumber thickness direction to change the seasoning defect drying defect that is caused because of moisture gradient.
3, the present invention can pure superheated steam (low temperature) as drying medium, adopt the mode of convection current that timber is continued heat supply, and under controlled vacuum condition, timber is carried out drying, on the one hand, because vacuum action, accelerated moisture the moving of timber inside, and made the moisture boiling vaporization that (generally is lower than 85 ℃) at a lower temperature, avoided the infringement to timber that may cause because of high temperature action for a long time; On the other hand,, utilize superheated steam that bigger exothermic coefficient is arranged, make timber obtain sufficient heat continuously, carry out dry run continuously owing to can continue heat supply to timber;
4, the present invention has adopted the heat-exchange device that heating and cooling are used, and can by cooling water being fed heat-exchange device the desiccated wood in the engine cavity be cooled off rapidly after timber drying finishes, and has therefore improved production efficiency greatly.
Description of drawings
Accompanying drawing 1 is the schematic diagram of timber dryer of the present invention;
Accompanying drawing 2 is the front view of the drying device of timber dryer of the present invention;
Accompanying drawing 3 is the vertical view of the drying device of timber dryer of the present invention;
Accompanying drawing 4 is the side view of the drying device of timber dryer of the present invention;
Accompanying drawing 5 is the equilibrium moisture content figure of drying medium under the vacuum state.
Description of reference numerals: description of reference numerals: 1. first valve; 2. second valve; 3. cooling fan; 4. cooler; 5. water-ring vacuum pump, 6. body; 7, radiator; 7a. radiator inlet; 7b. radiator outlet; 8. vacuum delivery line; 9. condenser; 10. the 3rd valve; 11. condensate collector; 12. the 4th valve; 13. tubing pump; 14. cooling water tank, 15. the 5th valves; 16. the 6th valve; 17. the 7th valve; 18a. first group of radiator; 18b. second group of radiator; 19. heat-insulation layer; 20. closing door; 21. hold down gag; 22. log-wagons; 23. fixed bar; 24. circulating fan; 25. boring parting bead; 26. dividing plate; 27. material heap; 28. dress material section; 29a. first fen chamber; 29b. second fen chamber; 30. the arrival end of condenser; 31. the outlet side of condenser; 32. the cooling water inlet of condenser; 33. the coolant outlet of condenser; 34. the inlet of cooler; 35. the outlet of cooler.
The specific embodiment
With reference to the accompanying drawings, describe the equipment of enforcement method for drying wood of the present invention and the specific embodiment of method for drying wood of the present invention in detail.
Method for drying wood of the present invention is based on the further investigation of the inventor to wood equilibrium moisture content under the vacuum state, the inventor finds under study for action, there are the corresponding relation of determining in wood equilibrium moisture content under the vacuum condition and temperature and absolute pressure, thereby obtain the approximate accounting equation of following two result of calculations of wood equilibrium moisture content under the vacuum condition.
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (1)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝228.0686?b＝-39.151482?c＝111.51028?d＝-2.7974235?e＝23.077616
f＝-17.970629?g＝0.866796?h＝1.8109251?i＝-1.1816787?j＝1.457619。
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (2)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝-412.70559?b＝340.35847?c＝16.528319?d＝-84.776089?e＝4.0013776
f＝1.8420135?g＝7.0445816?h＝0.5331407?i＝0.4498705?j＝0.8659198。
Put it briefly, the vacuum drying method of timber of the present invention comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages, calculating and control and temperature adapt vacuumizes absolute pressure, handles so that according to temperature that adapts with wood equilibrium moisture content and absolute pressure juggle is carried out drying at different drying stages.
Said method is suitable for according to accounting equation control absolute pressure.
On the other hand, the vacuum drying method of another kind of timber of the present invention comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, comprising:
In different drying stages, temperature and absolute pressure are finely tuned;
Equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages obtains the pairing wood equilibrium moisture content of described temperature and absolute pressure, makes it the requirement of realistic wood equilibrium moisture content.
This method is suitable for according to wood equilibrium moisture content fine setting temperature and pressure.
Specifically, the present invention utilizes this accounting equation that following four kinds of method for drying wood are provided.
First kind of method for drying wood comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length; 2) juggle is piled up in hothouse; 3) juggle is carried out preheating, make juggle be warming up to predetermined temperature; 4) to vacuumizing in the hothouse, equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages, calculating and control and wood equilibrium moisture content and temperature adapt vacuumizes absolute pressure, handles so that according to temperature that adapts with wood equilibrium moisture content and absolute pressure juggle is carried out drying at different drying stages;
Wherein, the relation by equilibrium moisture content EMC, temperature t and absolute pressure p in the following formula obtains described absolute pressure p:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (1)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝228.0686?b＝-39.151482?c＝111.51028?d＝-2.7974235?e＝23.077616
f＝-17.970629?g＝0.866796?h＝1.8109251?i＝-1.1816787?j＝1.457619。
Wherein, drying stage is divided into temperature a plurality of stages from low to high, such as the drying stage more than five or 5.
Second kind of method for drying wood comprises: the juggle that 1) the timber sawing is become to require length; 2) juggle is piled up in hothouse; 3) juggle is carried out preheating, make juggle be warming up to predetermined temperature; 4) to vacuumizing in the hothouse, equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages, calculating and control and wood equilibrium moisture content and temperature adapt vacuumizes absolute pressure, handles so that according to temperature that adapts with wood equilibrium moisture content and absolute pressure juggle is carried out drying at different drying stages;
Wherein, the relation by equilibrium moisture content EMC, temperature t and absolute pressure p in the following formula obtains described absolute pressure p:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (2)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝-412.70559?b＝340.35847?c＝16.528319?d＝-84.776089?e＝4.0013776
f＝1.8420135?g＝7.0445816?h＝0.5331407?i＝0.4498705?j＝0.8659198。
Wherein, drying stage is divided into temperature a plurality of stages from low to high, such as the drying stage more than five or 5.
The third method for drying wood comprises: the juggle that 1) the timber sawing is become to require length; 2) juggle is piled up in hothouse; 3) juggle is carried out preheating, make juggle be warming up to predetermined temperature; 4) to vacuumizing in the hothouse, comprising: in different drying stages, temperature and absolute pressure are finely tuned; Equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages obtains the pairing wood equilibrium moisture content of described temperature and absolute pressure, makes it the requirement of realistic wood equilibrium moisture content; Wherein, be calculated as follows described wood equilibrium moisture content EMC:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (1)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝228.0686?b＝-39.151482?c＝111.51028?d＝-2.7974235?e＝23.077616
f＝-17.970629?g＝0.866796?h＝1.8109251?i＝-1.1816787?j＝1.457619。
Wherein, drying stage is divided into temperature a plurality of stages from low to high, such as the drying stage more than five or 5.
The 4th kind of method for drying wood comprises: the juggle that 1) the timber sawing is become to require length; 2) juggle is piled up in hothouse; 3) juggle is carried out preheating, make juggle be warming up to predetermined temperature; To vacuumizing in the hothouse, comprising: in different drying stages, temperature and absolute pressure are finely tuned; Equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages obtains the pairing wood equilibrium moisture content of described temperature and absolute pressure, makes it the requirement of realistic wood equilibrium moisture content; Wherein, be calculated as follows described wood equilibrium moisture content EMC:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (2)
X=lnt, y=ln p, t be Celsius temperature (℃), p is absolute temperature (MPa)
a＝-412.70559?b＝340.35847?c＝16.528319?d＝-84.776089?e＝4.0013776
f＝1.8420135?g＝7.0445816?h＝0.5331407?i＝0.4498705?j＝0.8659198。
Wherein, drying stage is divided into temperature a plurality of stages from low to high, such as the drying stage more than five or 5.
Characteristics of the present invention are, utilize the relational expression of equilibrium moisture content EMC, temperature t and absolute pressure p, calculate the absolute pressure of taking out vital qi corresponding fast with computer with temperature, thereby can control timber drying more accurately, in addition, can also in timber drying, obtain wood equilibrium moisture content, thereby help controlling timber drying according to temperature and absolute pressure.
Below in conjunction with accompanying drawing drying equipment of the present invention and technology thereof are elaborated.
As shown in Figure 1, drying equipment of the present invention is made up of drying device, heating and cooling system, vacuum condensation system, cooling water recirculation system.
With reference to Fig. 1,2,3 and 4, drying device has body 6, and the inwall of body 6 is established heat-insulation layer 19, and inner formation cross section is the cavity of rectangle, the end sealing of cavity, and the other end is established closing door 20 to be opened/closed.Body 6 internal cavities comprise three parts of longitudinally arranging, shown in Fig. 2 and 3, and space between the dress material section 28 in the middle part of promptly comprising, dress material section 28 and the blind end and the space between dress material section 28 and the closing door 20.
Wherein, dress material section 28 is used to settle material heap 27 to be dried, shown in Fig. 3 and 4, dress material section 28 is separated into isometric minute chamber 29a of two cardinal principles longitudinally be arrangeding in parallel and 29b by being positioned at intermediate membrane 26 on body 6 longitudinal centre lines, settles log-wagons 22 among branch chamber 29a and the 29b separately; In the space between dress material section 28 and blind end, first group of radiator 18a and circulating fan 24 be arranged in parallel; In the space between dress material section 28 and closing door 20, second group of radiator 18b is set.
Shown in Fig. 2 and 4, log-wagons 22 have the vertical fixing bar 23 that base plate and at least 1 group are arranged on its both sides respectively, connect one deck ground level at the base plate last layer and pile up the material heap, separate by many boring parting beads 25 between layer and the layer, establish vertical boring of a plurality of negotiable drying mediums in each parting bead 25, as shown in Figure 4, the boring percent opening of parting bead 25 is 10%～80%.
Heating and cooling system are arranged in the cavity of body 6 inside, by two groups of radiators is that first group of radiator 18a and second group of radiator 18b form, wherein, second group of radiator 18b is arranged in the space of adorning between material section 28 and the closing door 20, and is positioned on the longitudinal centre line of body 6; First group of radiator 18a and circulating fan 24 are arranged in the space between dress material section 28 and the blind end, circulating fan 24 is positioned on the longitudinal centre line of body 6 substantially, and first group of radiator 18a can comprise two radiators (the one group of radiator that is positioned at circulating fan 24 front sides only is shown among Fig. 3) that lay respectively at circulating fan 24 front and back sides.
Wherein, first group of radiator 18a and second group of radiator 18b have respectively heat supply medium inflow radiator radiator inlet 7a and for by radiator and with the heat exchange of body internal cavity after the radiator outlet 7b (only showing the entrance and exit of first group of radiator among the figure) of medium outflow, the external valve 17 of radiator inlet 7a, the external valve 1 of radiator outlet 7b.
Circulating fan 24 shown in Fig. 3 is in abutting connection with first group of radiator (18a), also it can be arranged in abutting connection with second group of radiator (18b), second group of radiator (18b) can be a radiator that is positioned at the circulating fan front side, also can comprise two radiators that lay respectively at both sides, circulating fan front and back.
The vacuum condensation system is positioned at the bottom of drying device, is made up of condenser 9, water-ring vacuum pump 5, condensate collector 11, valve 12, valve 10 and connecting line.Wherein, the arrival end of condenser 9 links to each other with vacuum export mouth 8, the outlet side links to each other with the end of bleeding of water-ring vacuum pump 5, and the condensed water discharge outlet of condenser 9 links to each other with the inlet of condensate collector 11 through valve 12, and the outlet of condensate collector 11 links to each other with valve 10.
Cooling water recirculation system is positioned at a side of drying device, is made up of tubing pump 13, cooler 4, cooling fan 3, cooling water tank 14, valve and connecting line.Wherein cooler 4 is positioned at cooling water tank 14 tops, and cooling fan 3 is positioned at top one side of cooler 4; Cooling water tank 14 links to each other by the cooling water inlet of pipeline with condenser 9, the coolant outlet of condenser 9 links to each other with the inlet of tubing pump 13, the outlet of tubing pump 13 links to each other with cooler 4 inlets through valve 15, and the cooling water that is flowed out by cooler 4 outlets flows into cooling water tank 14 by deadweight.
The following describes and adopt vacuum drying of wood equipment of the present invention that timber is carried out the dry course of work.
1, piling
To treat dried Logs of small diameter or sheet material as requested length block into juggle, the length that makes each juggle is 5-15 with the scope of the ratio of its average diameter value or thickness, then with its longitudinally one deck connect on the base plate that one deck level is deposited in kiln truck 22, establish boring parting bead 25 between every layer, the kiln truck 22 that will be mounted with Logs of small diameter or sheet material juggle stacking then pushes the dress material section of body 6 internal cavities, pile up the vertical consistency of the vertical and body 6 of the juggle on kiln truck 22 this moment, then closing door 20 is closed by hold down gag 21.
2, to the timber preheating
Under normal pressure, Logs of small diameter or sheet material juggle stacking are carried out preheating, ratio according to preheating time (h) and juggle diameter (cm) is 1～2h: 1cm, as diameter is that be 10-20 hour the preheating time that the juggle of 10cm then needs, make the temperature of juggle reach 50-60 ℃, preheat temperature is than the high 5-10 of temperature ℃ of the drying schedule phase I usually).
ON cycle blower fan 24, and in first group of radiator 8a and second group of radiator 8b, send into heating agent respectively by first group of radiator 8a and second group of radiator 8b heating agent inlet 7a separately, flow out by its heating agent outlet 7b separately after making heating agent flow through first group of radiator 8a and second group of radiator 8b.The temperature of heating agent is controlled at 90-95 ℃.Effect by circulating fan 24 makes first group of radiator 18a and second group of radiator 18b distribute heat, impels drying medium convection current in body 6 cavitys, to quicken the preheating of timber.
Because what adopt among the present invention is vertical piling, therefore can guarantee along whole material heap section sawn timber to be heated more equably than traverse cycle.
3, the drying of wood
By the vacuum condensation system internal cavities of body 6 is vacuumized, with absolute pressure be controlled at 0.1～0.01MPa (vacuum is 0～-0.09MPa).
Circulating fan 24 is by being positioned at first group of radiator 18a and second group of radiator 18b of dress material section 28 both sides, the pure superheated steam that makes temperature as drying medium be about 40-85 ℃ flows through cavity between dress material section 28 and body 6 blind ends successively, pile up the branch chamber 29a of juggle, adorn the cavity between the closing door 20 of material section 28 and body 6 and pile up the branch chamber 29b of juggle, as shown in Figure 4, thus by the drying medium convection current to the juggle heat supply.Since juggle vertically with body 6 vertical consistencies, the section that therefore makes it possible to pile along whole material equably heats juggle and makes its drying; Simultaneously can be under the vacuum condition that changes desiccated wood.
When in this way timber being carried out drying, on the one hand, because the effect of vacuum, accelerated moisture, and made moisture be lower than boiling vaporization under 85 ℃ the temperature, avoided the infringement to timber that may cause because of high temperature action for a long time the moving of timber inside; On the other hand, timber is continued heat supply, utilize the drying medium superheated steam that bigger exothermic coefficient is arranged, make timber obtain sufficient heat continuously, carry out dry run continuously.
At timber in process of vacuum drying, along with the change of environmental pressure makes the inner barometric gradient that forms of timber.Under certain pressure when the timber temperature near or when surpassing the boiling point of the water under the corresponding pressure, water vapour will produce rapidly, barometric gradient causes flowing of water.
Afterwards, utilize the accounting equation of wood equilibrium moisture content under the vacuum condition, temperature and absolute pressure numerical value in the control body 6, for example, in order to make drying medium reach 8% equilibrium moisture content, when baking temperature was controlled to be 80 ℃, then controlling absolute pressure was 0.062MPa, that is to say the absolute pressure that controls environment according to temperature and equilibrium moisture content.Need to prove that in timber drying, the regulation and control of drying medium state are carried out according to drying schedule.Drying schedule is meant in the dry run, regulates the parameter list of medium temperature, pressure etc. in the hothouse according to different drying stages.Common drying stage is according to being divided by the changes phase of seasoned wood moisture content.At the different moisture content stages, corresponding temperature of stage and equilibrium moisture content are therewith arranged, by the absolute pressure that controls environment, the equilibrium moisture content that makes the environment correspondence is all the time less than timber moisture content at that time, can make the moisture in the timber be in evaporating state all the time, till meeting the requirements of moisture content.
Shown in Figure 5 for the absolute pressure being the equilibrium moisture content figure under the vacuum state drawn of ordinate.The absolute pressure (P) of the temperature (T) of medium and environment of living in can utilize Fig. 5 to find therewith the corresponding equilibrium moisture content numerical value of state (Arabic numerals at curve middle part are represented equilibrium moisture content, unit: %) as long as know.For example: when medium temperature is 80 ℃, the absolute pressure of environment be 0.06MPa (vacuum for-0.04MPa) time, the corresponding equilibrium moisture content numerical value of state is 8.1% therewith, therefore according to Fig. 5, in order to reach 8.1% equilibrium moisture content, when baking temperature is set at 80 ℃, require the absolute pressure of environment to be controlled to be 0.06MPa.
In fact, need carry out drying stage by stage to the timber of moisture content higher (as 90-100%) and progressively reduce moisture content, and each stage according to drying schedule (the equilibrium moisture content starting point of common drying schedule is 14～16%).Coming progressively regulating and controlling temperature and absolute pressure, is 8-10% thereby make it finally reach the target moisture content.If timber pairing equilibrium moisture content of environment when high-moisture percentage is too low, then can cause timber top layer water evaporates too fast, easily produce such as seasoning defect drying defects such as table split, therefore stage by stage drying progressively to reduce the moisture content purpose be to prevent to treat that timber generation table splits.
In whole dry run, reduction along with moisture content, by the temperature of adjusting drying medium and the absolute pressure of environment of living in, make the pairing equilibrium moisture content of drying medium state be lower than timber moisture content at that time all the time, this can make, and moisture is in evaporating state all the time in the timber, until reaching whole moisture content.
4, cooling discharge
When the end of timber is moisture when reaching requirement 8-10%, in heat-exchange system, feed 20 ℃ of condensed waters, to realize fast prompt drop, discharging when the timber temperature is reduced to below 40 ℃.
Method for drying wood of the present invention is applicable to all timber, such as shirt wood plank, cottonwood plank stuff etc.
Although above the present invention is had been described in detail, the invention is not restricted to this, those skilled in the art of the present technique can carry out various modifications according to principle of the present invention.Therefore, all modifications of doing according to the principle of the invention all should be understood to fall into protection scope of the present invention.
Claims (4)
1. the vacuum drying method of a timber comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages, calculating and control and wood equilibrium moisture content and temperature adapt vacuumizes absolute pressure, handles so that according to temperature that adapts with wood equilibrium moisture content and absolute pressure juggle is carried out drying at different drying stages;
Wherein, the relation by equilibrium moisture content EMC, temperature t and absolute pressure p in the following formula obtains described absolute pressure p:EMC=a+bx+cy+dx
2+ ey
2+ fxy+gx
3+ hy
3+ ixy
2+ jx
2Y (1)
X=lnt, y=lnp, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝228.0686?b＝-39.151482?c＝111.51028?d＝-2.7974235?e＝23.077616
f＝-17.970629?g＝0.866796?h＝1.8109251?i＝-1.1816787?j＝1.457619。
2. the vacuum drying method of a timber comprises following step of carrying out in turn:
1) the timber sawing is become to require the juggle of length;
2) juggle is piled up in hothouse;
3) juggle is carried out preheating, make juggle be warming up to predetermined temperature;
4) to vacuumizing in the hothouse, comprising:
In different drying stages, temperature and absolute pressure are finely tuned;
Equation according to temperature, pressure and wood equilibrium moisture content relation in the different drying stages obtains the pairing wood equilibrium moisture content of described temperature and absolute pressure, makes it the requirement of realistic wood equilibrium moisture content;
Wherein, obtain described wood equilibrium moisture content EMC by following formula:
EMC＝a+bx+cy+dx
2+ey
2+fxy+gx
3+hy
3+ixy
2+jx
2y (1)
X=lnt, y=lnp, t be Celsius temperature (℃), p is absolute pressure (MPa)
a＝228.0686?b＝-39.151482?c＝111.51028?d＝-2.7974235?e＝23.077616
f＝-17.970629?g＝0.866796?h＝1.8109251?i＝-1.1816787?j＝1.457619。
3. vacuum drying of wood method as claimed in claim 1 or 2, wherein, described drying stage is divided into temperature a plurality of stages from low to high.
4. vacuum drying of wood method as claimed in claim 1 or 2, wherein, described drying stage is divided into temperature five above drying stages from low to high.
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