SE538976C2 - Method and apparatus for dehumidifying a drying air flow - Google Patents

Abstract

. A part fl desolate (21) is diverted from a circulating drying air fl desolate (2) closed in a drying chamber (1), sucked through and dehumidified in a package (7) and remixed in the drying lu desiccation via fl spout (23) and spreading duct (24). The package is built up with frames (4) covered with a diffusion-open cloth (3) and spacer boards (5,6) for a steam transfer via diffusion between the drying compartment and the outer air (9) cross-acting package. External lids are sucked through the package via fl genuine (91) and pressure mist-enriched, heated and steam-saturated out into the open directly or via a shower tower (92) for heat recovery in a sprinkled water fl desert (95). (fi gur ld)

Description

Method and device for dehumidifying a desiccant.

The present invention relates to a method for dehumidifying a drying air fl closed circulating within a drying chamber via steam diffusion to the outside air through a number of diffusion layers comprising parallel layers of diffusion-open cloth between delimiting heat-insulating columns of stagnant air with a side air of the outer air.

Objects of the invention are drying chambers of various kinds and types of drying goods, which today work with hot air drying and air exchange with external air vapor separation.

The invention uses a technique according to the preamble above, which is known from central Swedish patent 03 02197-9. The patent specification describes the technique designed as a pleated construction filling a wall surface of a chamber dryer for wood.

Test with a timber dryer of 80 kbm with dry temperature maximized to + 70 ° and converted by filling the door hole with 60 sqm of weekly diffusion area was as follows: the heat demand from boiler and boiler was reduced by 35% and the drying time was shortened 35% with regular heat delivery. The drying process is self-regulating in internal humidity climates and against varying external temperatures. The very high efficiency is essentially independent of varying outer temperature between summer and winter and of the degree of drying. The desired drying speed during different phases of the drying of the drying goods is controlled by means of the supply heat effect.

Despite the interesting result, the very conservative industry is callous towards such a "simple" and unsanctioned solution. It is also not easy in dangerous drying chambers to use this wall surface. Various solutions to fill the gate hole with a superficial diffusion device have not been heard.

The object of the invention is to achieve a breakthrough for the technology by rationalizing a production and easy replacement of the diffusion surface considered as a consumable, to streamline the steam exchange between drying air and outer air in a compact package which is docked to the openings in the dryer housing. to optionally and easily recover the dryer heat in a water fl desert.

This object is achieved in a manner characterized in that the diffusion layers are formed by winding a weft of the cloth a number of half turns over rectangular wooden frames, by connecting the cloth-covered frames along their long sides first on vertically set, whole or divided spacer boards and along sine card sides to others. upright, whole or split spacer boards, whether combined lying, sloping or standing on a pallet for a vapor transfer between the drying air and the outer air cross-flowing package and by part fl fate being deflected out of drying air fl fate via a hole in the drying chamber outer casing su .

The invention is described below in connection with the figures. Figures 1a illustrate the method in perspective. Figures 2a-c illustrate operating conditions. Figures 3 a-c show sections and planes when installing in a timber dryer.

According to Figure 1a, a diffusion surface is formed by winding a wad of endifusion-open cloth 3 a number of half turns over rectangular wooden frames 4 into cloth-covered frames 4 '. The frames comprise long sides 41, short sides 42 and cut-outs 43. Between the frame parts 41,42,43 two-surface surfaces 4 ”are formed in opposite corners in the form of a triangle, which is each dimensioned to about 1/6 the frame surface and which according to fi gur lb is less or more or preferably completely sealed against lu fl leakage across the fabric layers 3. The covered frames 4 ', 4 ”connect fi gur lc along their long sides 41 to first upright, entire or split spacer boards 5 and along their short sides 42 to other raised edge set, whole or split spacer boards 6 and joined together according to fi on a pallet 56 to a package 7 for steam transfer between hot-humid drying cabin fi 21 and outer air 9 cross-flowing.

The package 7 is parked along the outer casing of a drying chamber 1 preheating air drying of a drying material 11 with a closed circulation of a drying air closed in the drying chamber 2. A considerably smaller part one or two spouts 23 and a transverse air duct extending air diffuser duct 24. External air 9 is sucked through the package and forced out with spout 91 in it heated by condensing vapor to steam and saturated with steam. The entire drying heat is found in this fl fate and can be recovered in a sprinkled water fl fate 95 by passage via a shower atom92.

The wood parts 4,5,6 are exposed to significant shrinkage / swelling during the drying cycle. Lying on a heating arm according to fi gur lc, the entire package 7 can free-shrink / swell. With the frames mounted standing according to Figure 3a, the joining parts according to Figure 1b suitably with two frames 4 screwed to halved, second spacer boards 6 and screwed together with whole, first spacer boards 5 into a stiffened, wood-saving unit. The double frames are screwed onto the pallet with a space between them for shrinkage / swelling, which is airtight with a gasket 61 between the halves of the spacer boards 6.

Based on casting fabric as fabric material 3 and delivered on a roll of 3.2 m width, the frames discussed below are made to a suitable handling format of 3.1 x1.6 m, each with a diffusion area of 4.5 sqm with the frames compared to frames with a width / length ratio of 1: 3.

For the diffusion surface, the following applies per square meter. The vapor velocity is proportional to the back pressure difference called the driving pressure between the vapor pressure in fl deserts 21 and 9 and inversely proportional to the number of layers of cloth 3. An undesirable gap between the deserts across the surface is proportional to the locally over surface varying pressure difference between the number of layers called p and vice versa Pressure drop and leakage increase with the square of the air velocity in the den deserts.

The purpose of the invention is to replace an air exchange between the drying air and the outside air with a closed drying air circulation. Therefore, the leakage must be minimized. A first step is to calmly and well-distributedly suck the fates through the package 7 at low speeds.

The above-mentioned relationship is illustrated in reference to Figures 2 a-c. Figure 2a shows the frame 4 'with the format as above covered with two layers of cloth with the drying air 21 sucked along the short sides 42 with the pressure drop = 10 and the outer air sucked along the longitudinal sides with a pressure drop = 10. 16 points show the local pressure differences between the fl fates. Against two opposite frame corners inside the surfaces 4 ”, these increase sharply and in proportion thereby air leakage.

In table, ur gur Zb, a frame A is compared with the entire frame surface clad with two layer cloth with a frame B with 2/3 of the surface = X clad with two layers, half the surface 4 ”= Y clad with 4 layers of cloth and half the surface 4” = Z covered with 6 layers of cloth, a frame C with two layers of cloth and the surface 4 ”completely lu fi and vapor-tight, for example via cover with building foil.

The conclusion of the study shows that the relationship between steam and air / leakage increases from frame Avia B to C by a factor of 1.4 and 2.2, respectively, which with equal leakage means that the speed in frames B and C can be increased by a factor of 1.18 and 1.5 respectively. The effect of this with the variants A, B, C for the whole package 7 is shown in table fi gur 2c, where gap width corresponds to half distance board 5 plus half distance board 6 and where air width denotes the sum gap widths and where mass fl destinies 21, 9 and steam transfer are equal. Frame C is chosen as the lucky winner with a significantly reduced dimension on the package 7, gap width and tree dimensions 5 and 6 and not least on the road section for the steam reduction between fl fates. The vapor diffusion between the fls 21,9 is proportional to the difference in vapor pressure between them, which is reduced from inlet to outlet in the package 7. The average value over a frame 4 'here called the driving pressure becomes decisive for the total fl flow of vapor flowing. A study of a single-vapor pressure table shows that the outer 9 is significantly more efficient in that the vapor with a low vapor pressure increase than the drying air 21 is to lose steam with a low vapor pressure drop and thus that a mass fl desiccant air fl desolation should be matched to a significantly smaller radius. the drying air is driven between the longitudinal sides 41 and the outer air between the short sides 42 and that the short sides are dimensioned substantially smaller than the long sides.

With a mass ratio of 4: 1, 4 kbm drying air of 104 g steam with 26g / kbm from a state 160g / 250 mbar to a state l34g / 208 mbar is lost while 1 kbm outside air takes up the amount of steam 104 g from an annual average state of + 5 ° / 5g / 5mbar 46 ° via 23 g of mist condensing steam to a saturated state + 5 1 ° / 87g / 130 mbar. One drive pressure = 230-65 = 165 mbar is obtained, about 2/3 of the input value for the fates. With a ratio of 5: 1, 1 kbm of outside air takes up 130 g by heating 50 ° via 25 g of vapor condensing to mist to a saturation state + 55 ° / 105g / 160 mbar and an increased temperature quality in heat recovery in the shower tower 92. This is done at the expense of a reduced drive pressure = 230-82 = 148 mbar. Further reduction of the outside air is limited by the fact that a substantial vapor pressure must remain against the drying air at the exit of the package. 7 With winter cooling, -20 °, the following is obtained: 34g of vapor condensing steam to a saturated state of + 48 ° / 75 g / l 12 mbar. One drive pressure = 230 -60 = 170 mbar is obtained. The changes are very marginal in contrast to the conventional lu fi exchange technology, whose efficiency drops by about 20%.

In reference to Figures 3 a-c and the data mentioned above, the invention applied to the timber dryer mentioned in the preamble and replacing the functional but impractical test installation mentioned in the preamble is illustrated in the port opening. Condition in the drying air 2 is per kbm 160g / 250 mbar. Drying speed = 300 kg steam / h. In the test installation, the diffusion area = 60 sqm with 4 layers of canvas 3. Coated with large den fates, the driving pressure is closest to 245 mbar and steam fl the width 300/60 = 5 kg / sqm, h. The test installation is replaced by a package 7 with the same performance: The package 7 is in a first example according to figure 3a built with standing frame type C of the mentioned format 3.1x1.6 m, with two layers of fabric 3 and and 3 sqm diffusion surface and is operated with the mentioned to 2/3 reduced driving pressure and ratio 4: 1 in mass fates. Resulting steam fl fate = 2 / 3x2x5 = 6.6 kg / sqm, h and perram C = 3 x 6.6 = 20 kg / h. Thus, 15 frames are required.

With 26 g pin / kbm, part fl the fate becomes 21 of the drying loop fi 2 = 11,500 kbm / h = 3.2kbm / s. With an employed lu fi speed = 1.5 m / s, the flow area = 2.14 sqm is divided into 15 3.15 m long columns of 45 mm.

With an uptake of 104 g / kbm, the outside air is driven fl the fate with 2,900 kbm / h = 0.8 kbm / s and with the air speed = 1.1 m / s and a flow area of 0.73 sqm divided into 15 1.55 m long gaps with gap width = 33 mm. the package is equal to the fates.

The package 7 is hereby built 15x (45 + 33 + 22) = 1500 mm.

With mass fates in a ratio of 5: 1 and a form change to 1: 3 of the frame of type C to 1.3x3.9 m with retained surface and pressure drop, the result is: The number of frames increases with decreasing drive pressure as above by a factor of 165/148 to 17 frames. Drying air: air velocity = 1.65, flow area = l _95 sqm distributed over 17 3.85 m long slits of 30 mm Exterior air: Flow = 0.64 kbm / s, air velocity = 0.96 m / s flow area = 0.67 sqm distributed over 17 1.25 m long slits and 32 mm.

The package is based 17x (30 + 32 + 22) = 1440 mm extended by a factor of 1.25. The pretreatment air advantageously cooperates with shorter wavelengths for diffusion, long-distance distance and an increased temperature quality from + 51 ° to + 55 ° for single heat recovery in a shower head 92, which can be used for heating or secondary drying of biomass or the like.

It is concluded that the width / length ratio in the frame 4 'should be 1: 3 in order of magnitude and the mass fl ratio in outer air / drying air in order of magnitude 1: 5.

Furthermore, the effect of the number of layers of canvas 3 is highlighted. An increase from two to three layers means that, for example, 16 frames may be increased to 24 to compensate for a 2/3 reduced steam fl fate per unit area. At the same time, with maintained fl fates, flow rates, pressure drops and leakage, the gap widths are reduced from, for example, 60 mm to 40 mm and the package width from 16x84 = 1340 mm to 24x63 = 1520 mm. To 2/3 reduced wavelength for a to 2/3 reduced force fl fate facilitates diffusion fl fate by a factor of 9/4.

The corresponding result is a misalignment from two to one layer of fabric 8 frames, 120 mm gap widths and a package width = 8x142 = 1140 mm. Doubled road sections and steam fates complicate the diffusion fate by a factor of 4. The conclusion is chosen between two or three layers of fabric.

The package was lifted into an insulated box 8 via a removable front 81. The box according to gur 3b, for example, is mounted on a service aisle 12 which is often present in front of your dryers 1 The box is connected with the hole 22 to the drying air 13 with a pressure equalized to the atmosphere via diffusion surface. The atmospheric pressure in the region is maintained independently of the reversal of drying air fl destiny 2. Part fl destiny 21 is sucked through the hole, via the box, package 7 and the box with said fl spigots 23 and is pressed via a strategically placed spreading duct 24 to remix air drying det destiny 2.

According to Figure 3 c, the front 81 is at all points farther than the package, which is easily parked, whereupon a frame 93 for air intake of the outer air 9 with nets and rain and wind protection and a frame 94 bellows-connected with fl age 91, which pushes it in, is pushed towards the package ends. heated, misted and saturated fl the fate of the outer air fi in the shower tower 92.

The figure shows a shower chamber 92 common to two chambers 1, as the mixer drying heat from two drying processes operating in different phases. The water fate 95 can optionally be switched on or off depending on whether its heat is needed or not.

Temperature difference over the frame surface = + 70 ° / + 25 ° = 45 °. The frame area is 15x4.5 = 70 sqm. U-value for two-layer with air gap = 2.5 w / sqm °. The loss of sensitive friends = 70x 45x 2.5 = 8 kw in relation to the latent value in the steam transport of 0.65x300 = 195 kw and the drying process in chamber 1 with an efficiency of 203/300 = 0.68 kwh / kg water. When the drying material 111 is finally dried with a driving pressure reduced to 1/3, the relationship becomes sensitive / latent = 8/65 with efficiency = 0.73 kwh / kg, which means a very marginal deterioration.

An installation in the timber dryer as above replaces the usual air change with the accompanying effect. Climate control and basing are disconnected. Normal rapid heating with a high heating effect of the wood to "working temperature" with its risks of drying cracks is eliminated. The state of the dryer is self-regulated in that the latent heat in the moisture migration and the diffusion is always in balance with the heat supplied and the temperature rise of the dryer. This self-regulates an optimal humidity climate and provides uniform heating / drying from the start. Efficiency is optimally high with varying outside temperature and drying rate. With the installed heating effect, drying takes place approx. 35% faster without deterioration in quality, which saves the more expensive fl genuine energy and enables an increase in sales of approx. 50%. The entire drying energy can be efficiently recycled to the industrial tower.

Turned into figures, an energy gain of 10,000 dri fi hours of approx. 1000MWh worth approx. SEK 300 'is obtained. An increased turnover gives an additional large profit as well as an utilization of 2000 Mwh recycled heat.

The package 7 may be considered a consumable, where especially the fabric 3 has a limited shelf life of about 10,000 driítt hours while wood lasts longer. A package change takes place quickly from the outside without any effect on the operation and at an extremely marginal cost. Material cost for the package is approx. SEK 600 for the fabric and SEK 1800 for the wood material.

Claims (3)

Method for dehumidifying a drying air fl desert (2) closed circulated within the drying chamber (1) via steam diffusion to outer air (9) through a number diffusion layer comprising parallel layers of diffusion open cloth (3) preferably in the form of fi bed cloth and of quality casting cloth where a part fl 21) of drying air fl and outer air (9) is driven along both sides of the layers characterized in that the diffusion layers are formed by winding a wad of cloth a number of half turns over rectangular wooden frames (4), by connecting the deducted frames (4 ') along their long sides (41 ) spaced first, full or split spacer boards (5) and along their short sides (42) to second vertical, full or split spacer boards (6), of which are brought together lying, inclined or standing on a pallet (56) into a vapor transfer between drying air and external air cross-flowing package (7) and by the part fl fate being deflected from the drying air flow via a hole (22) in the outer casing of the drying chamber, sucked through the package and remixed as itorklu fifl ödet via organs (23,24). Method according to claim 1, characterized in that two triangularly shaped frame surfaces (4 ") along opposite corners of the fabric-covered frames (4 ') each comprising about 1/6 of the frame surface less or more or preferably completely tightly against air leakage across the layers of said fabric (3). ). Method according to claims 1-2, characterized in that said long sides (41) are substantially longer than the short sides (42) and in that said part fl desert (21) is sucked the intermediate long sides with a mass fl desert significantly larger than the mass fl desert of outer air (9), which with fl true (91) sucked between the short sides. Method according to Claims 1 to 3, characterized in that mist-enriched, heated and vapor-saturated outer air 9 (9) is exchanged in a free-flowing shower head (92) against a sprinkled water 95 (95) before a discharge in the open air. Method according to claims 1-4, characterized in that the ratio in mass fl of external air / drying air is of the order of 1: 5. Device for dehumidifying a desiccant air according to the method of claim 1, wherein the device comprises a drying chamber (1) with a casing and a cross-current package (7) docked to the drying chamber casing for steam transfer between drying air and outer air via a diffusion layer. diffusion-open cloth (3), in which the diffusion layers are formed by winding a web of the cloth a number of half turns over rectangular wooden frames (4), by connecting the cloth-covered frames (4 ') along their long sides (41) to first vertically set whole or divided parts. spacer boards (5) and along their short sides (42) to others on high-edge, whole or split spacer boards (6), in that the fabric-covered frames (4 ') are joined together lying, inclined or standing on a pallet (56) to an evaporator transfer between drying air and external air cross-flowing package (7) and in that the device comprises the package (7) parked within a single heat insulator, along the outer part of the drying chamber (1) eyelet mounted, box (8) with removable front (81), in that the device is arranged to deflect via a hole (22) the outer casing of the dryer duct a part fl desiccant of drying air which is sucked through the package (7), by having a kt (23) and an air diffuser duct ( 24) are arranged to remix the part fl in dry air fl and that the device comprises an air intake (93) connected to the package for outside air and a fl true (91) pre-flow of mist-enriched, heated and steam-saturated air in the open directly via passage via a shower enclosure (92) in countercurrent to a sprinkled water fl desert (95).