FI79157B - Gas-infra red float dryer - Google Patents

Abstract

A gas-infra red float dryer that includes one or more infra red units in a row, whereby the track (W) that runs through the treatment interstices (A, B) of these is dried from both sides. The dryer includes supporting blower units which lift the track (W) without coming into contact with it while it passes through the treatment interstices (A, B) of the dryer. The system includes at least one or more gas-infra units (10, 20) whose infra-radiating units (11R, 21R) and/or surfaces delimit the tracks treatment interstice (A and B). Outflow air channels (16a, 26a and 16b, 26b) open onto the aid treatment interstice (A, B), through which the combustion gases from the gas-infra units that enter the treatment interstices (A, B) as well as the blower air flow (F2) are conducted away for recirculation and/or to a heat reclamation system (30). The dryer includes pre-blower units (13, 14, 15, 23, 24, 25) in conjunction with the gas-infra red units (10, 20), through the cracks of whose nozzle (18) -lifting gusts are blows (F2) to lift the track (W) to be dried without coming into direct contact with it.<IMAGE>

Description

79157 1 Gas-infra-fluidized bed dryer Gasinfra-svMvtork and / or a heat recovery system, and said dryer comprises foil blowing units in connection with the gas infrastructure units, through the nozzle slots of which support blows are blown which non-contact support the web to be dried.

The present invention relates to the drying of a paper web, a paperboard web or other similar moving web. A typical application of the invention is the drying of a paper web in connection with its coating or surface sizing.

20 It is known from the paper webs to be coated either by separate coating machines or by on-machine devices integrated in the paper machines or by surface gluing devices operating in the drying section of the paper machine so that the web to be coated is applied to the final bushing e.g. one drying cylinder group as a post-dryer. A typical application of the present invention is the intermediate dryer after the coating device just mentioned, to which, however, the invention is not limited.

It is already known that the so-called fluid bed dryers for drying contacts-30 paper web, paperboard web or the like. Fluidized bed dryers are used, for example, in paper coating equipment after a blade, roll or silk coating to non-contact to support and dry the wet web of coating material.

35 Various drying and support air blower nozzles and their configurations are used in fluidized bed dryers. Said blow nozzle grooves 2 79157 1 can be divided into two groups, namely overpressure or float nozzles and vacuum or foil nozzles.

The previously known most commonly used fluidized bed dryers are based exclusively on air blowing. For this reason in part, the fluidized bed dryer becomes quite bulky, because the working distance of the fluidized bed dryer must be relatively long in order to obtain a sufficiently high drying power. In part, these disadvantages are due to the relatively low energy density of drying in air drying.

10

Various dryers are already known which are based on the effect of radiation, in particular infrared radiation. The use of infrared radiation has the advantage that the radiation has a relatively high energy density, which increases as the wavelength decreases. The use of infrared dryers for drying the paper web 15 has been hampered by e.g. the risk of fire because the temperatures of the infrared radiators and their surroundings become quite high in order to achieve sufficiently short-wave drying radiation.

As is already known in infrared dryers, thermal energy is conducted to the device either as electricity or natural gas. The price ratios of electricity and natural gas vary, so the affordability of their use also varies. Electric infra dryers require cooling air, while gas infra requires combustion air, which at the same time can act as cooling air.

25 With regard to the state of the art most closely related to the invention, reference is made to Valmet Oy's FI announcements 75 008 and 75 009.

The object of the present invention is, above all, to further develop the previously known gas dehumidifiers, although certain embodiments of the invention may also be suitable for use in electrical infrared, which, however, do not achieve all the advantages provided by the invention.

The previously known infrared dryers have had room for development, especially in terms of air technology and non-contact web support in the drying interval and the solution of web flutter problems.

The object of the present invention is therefore to provide a new device based on infrared drying and air drying, but in which the contactless air support of the web in the drying gaps is also implemented so that the web in no case comes into contact with the generally very hot surfaces delimiting the drying intervals.

It is a further object of the present invention to provide a new infrared dryer combined with air drying so that the web can pass safely and without fluttering through the infrared dryer also in intermittent conditions.

It is a further object of the invention to provide an infrared dryer which has a relatively high specific evaporation power and which can also utilize the combustion air and circulating air of the gas infrared radiators for drying so as to maximize heat transfer.

It is a non-essential additional object of the invention to provide a gas dehumidifier in which the dried web both passes inside the dryer and leaves it more stably and without fluttering.

20

In order to achieve the above and later objects, the invention is mainly characterized in that the device comprises a first foil unit arranged on the inlet side of the first infra unit and a opposite foil unit previously arranged on the inlet side of the web, the latter foil unit there is a second foil unit between the second infra-unit on the same side of the web, which together with the infra-unit on the other side delimits the outlet channel, on the outlet side of the web there are foil units, one of which, together with the pre-existing infra unit, delimits the exhaust duct, said exhaust ducts being connected to the exhaust fan of the air system; suction channel and that said foil units on both sides of the web face each other in phase shift so that at the foil units there is an outlet channel on the opposite side of the web.

4 79157 1 The gas infra-fluid dryer according to the invention always has a vacuum bearing surface opposite the suction opening, which contributes to the fact that the driveability and stable track travel do not depend on the intake air volume, but the track runs stably at a certain small distance from the foil bearing surface.

In the invention, it is possible to use double-sided gas infiltration without the risk of excessive heating of the web, because the foil nozzles effectively break the boundary layers.

10

The gas infra-fluidized bed dryer according to the invention has a similar recirculating air system as the previously known gas-heated fluidized bed dryer. If necessary, a separate heat source, eg a gas burner, can also be used to heat the blowing air.

15

In the gas infrastructure fluidized bed dryer according to the invention, the humidity level of the circulating air is made considerably higher than in the prior art Lei dryers, and thus a more economical heat recovery system can be connected to the dryer. The higher moisture level 20 is due to the higher specific evaporation, i.e. the higher energy density.

In the following, the invention will be described in detail with reference to some embodiments of the invention shown in the figures of the accompanying drawing, to the details of which the invention is in no way narrowly limited.

Figure 1 shows a schematic side view of a first embodiment of the invention.

30

With the gas-infrared fluidized bed dryer shown in Fig. 1, the web W entering the dryer in the direction W and leaving the direction W is dried without contact. The dryer comprises successive infrared drying intervals A and B formed between the upper unit 10 and the lower unit 20.

The first infrared drying interval A is formed between the gas infrastructure units 11a and 21b. Respectively, a second infrared drying interval B is formed between the two opposite gas infrastructure units 11b and 21b. The infrastructure units 5 79157 1 118,218,110 and 21b are gas infra known per se to which combustion air is introduced in the direction of the arrows F 1. Combustion of the gas generates infrared radiation and flue gases, both of which are represented by arrows R marked in treatment intervals A and B.

5

The dryer according to the invention also includes foil nozzle units which act mainly as non-contact supporting supports for the web. According to Fig. 1, a first upper foil unit 13 is connected to the front side of the first upper infra unit 11a, and a second upper foil unit 14 is connected to the front wall of the second upper infra unit 11b, respectively. before the first separate foil unit 23, a second foil unit 24 connected to the rear wall of the first infra unit 21 and a third foil unit 25 connected to the rear wall of the second infra unit 21b. The foil units have foil nozzles 18, respectively. 28 and the bearing surfaces 17 in the direction of travel of the web W, resp. 27, which will be located at a short bearing distance from the top and bottom surfaces of the web W. There is a first air outlet duct 16a between the infra units 11a and 11b of the upper unit 10 and a second outlet duct 16b between the infra unit 11b and the foil unit 15, respectively. Accordingly, the subunit 20 has a first outlet passage 26a and a second outlet passage 26b between the first foil unit 25 and the first infra unit 21a between the second foil unit 24 and the second infra unit 21b.

The system 25 supplied through the supply air foilyksikköjen 13,14,15,23,24,25 inside the blow-boxes in the direction of the arrow and is blown against the web W in the direction of the arrows F ^ kannatuspuhalluksina, which is a kind of dry-tusvaikutuskin. Residual flows are taken from the drying intervals A and B in the direction of the arrows F1 via the outlet channels 16a and 16b, 26a and 26b, respectively. These exhaust flows F1 consist of both hot flue gases R and air blows F2. When exhaust air ducts 16 and 26 are used according to the invention, a controlled gas exchange and a large heat transfer to the web are obtained in the drying intervals A and B. In addition, the heat content of the gas streams taken through the exhaust air ducts 16 and 35 26 is recovered in the heat recovery system 30. Some of the air taken through the exhaust ducts 16 and 26 can be returned to the air circulation as blown air F 2.

6 79157 1 The processing intervals of the infra units are limited on both sides of the web by opposite infrared radiation surfaces or areas, which are schematically indicated in Fig. 1 by reference numerals 11R and 21R. These areas or surfaces consist of rows of gas burners burning gas flames and / or other radiant surfaces heated by said gas flames. The control elements and the gas burners are known per se and need not be described in more detail in this connection.

The system shown in Figure 1 is such that all the foil nozzle-10 met 18,28 blows (arrow F2) in the direction of travel of the web W. This is advantageous in that the track is blown away from the hot radiating surfaces of the infrastructure units in the event of a breakdown.

The speed F2 of the blows coming from the nozzles 18 is generally in the range 15 to 20 ... 45 m / s, preferably in the range 30 to 35 m / s. The velocity F 1 of the gas flows through channels 16 and 26 is generally in the range of 5 to 10 m / s. The width of the nozzle openings 18 (nozzle gap) is generally in the range 2 ... 5 mm. The width of the drying intervals A and B, i.e. the distance of the bearing surfaces determined by the gas burners from the plane of the web passing between them, is generally in the range of 6 to 15 mm.

Infrared dryers and foil units extend over the entire width W of the web to be dried. Although the web W is shown to run horizontally in Figure 1, the invention can of course also be implemented in such a way that the web runs vertically either upwards or downwards or upwards or downwards.

In the infra units according to the invention, control devices can be used with which the power of infrared drying in the transverse direction of the web is controlled in order to adjust the transverse moisture profile of the web 30. Various measuring and control devices can be connected to the air system related to the invention, with which the system is regulated and its operation is controlled and possibly optimized. The measuring and control system may also include various devices for measuring the properties and transverse profiles of the web, from the measurement signals of which the dryer according to the invention is controlled.

I) 7 79157 1 The following are claims which, within the scope of the inventive idea defined by it, the various details of the invention may vary and differ from those set out above only by way of example.

5 10 15 20 25 30 35

Claims (4)

A gas infrared dryer, comprising gas inflow units (10,20), whose infrared elements (11R.21R) and / or surfaces limit the treatment spaces (A and B) of the web 5 to which outlet air ducts (16a, 26a and 16b, 26b) open respectively, through which channels the combustion gases of the gas inlets that reach the treatment interstices (A, B) and the blowing air streams (F ^) are conducted for recirculation and / or to a heat recovery system (30), and which dryer comprises foil blowing units 10 (13, 14,15,23,24,25) in connection with the gas inflow units (10,20), through which nozzle cracks (18) blow out support blisters (F (), which contact-free support the web (W) to be dried, characterized by the device comprising a first filing unit (13) arranged on the front side of the first infrastructure unit (11a) on the entrance side (W) of the web and prior to this an opposing filing unit (23) arranged on the entrance side (W) of the web, that latter foil assembly (23) together with the web In the following infrastructure (21a), a first outlet channel (26a) limits that between the first infrastructure (11a) and the second infrastructure (11b) on the same side of the path (W) there is a second foil unit (14), which together with the infrastructure (11a) on the same side as this one limits an outlet channel (16a), that in relation to the aforementioned infrastructure units (11a, lib) between the infrastructure units (21a and 21b) on the opposite side there is a foil unit (24), which together with the other aforementioned infrastructure (21a) limits an outlet channel (26b), that on the output side (W) of the path (W) there are foil units (15,25), one of which together with the infrastructure (lib) before it limits an outlet channel ( 16b), that said outlet ducts (16a, 26a, 16b, 26b) are joined by a suction duct (42, 43) to the outlet blower (33) of the air system (43, 43) (Figure 1) and that said foil units 30 (13, 14) , 15,23,24,25) are in phase shift on both sides of the web (W) in such a way that at The foil units have an outlet duct (16b, 26a, 26b) on opposite sides of the web (W) (Figure 1). 1 Patent claim Dryer according to Claim 1, characterized in that the air streams (F 2) to be sucked from said outlet air ducts (16a, 26a and 16b, 26b) are partly fed to the blower (33) to the heat recovery system (30) and to a part sucked by a second li