DE1927839A1 - Drying installation for ordinary ceramics - Google Patents

Abstract

The apparatus comprises a number of drying chambers, in which the material being dried is subjected to a circulation medium. The drying installation has one or more hot air chambers operating with moist air as the circulation medium having a relative humidity of 50-80%, and a vapour chamber operating with slightly superheated steam. Various heating media are fed to the circulation media in the upper chambers of the hot air and vapour chambers. Dry hot air at 60-80 degrees C is fed to the hot air chambers, and highly superheated steam at 200-300 degrees C to the vapour chamber.

Description

The invention relates to a drying system for in particular heavy clay products. There are three different types of methods for efficiently drying the wet bricks developed, the large-scale drying, the chamber drying and the tunnel drying.

In the case of large-scale drying, the briquettes are placed on shelves and exposed to the action of still air or air currents that flow through rotating cylinders with vertical nozzles, horizontally blowing air slots, up and down air slots arranged at a supply air source or in the aisles between the shelves - and moving fans are generated. This type of drying, apart from the fact that it takes up a lot of space and takes up a long time, has considerable disadvantages. The briquettes are only dried well in those parts of the stack that are swept by the air flow. Inside the pile , however, wet nests remain, the drying of which means a considerable extension of the drying time, usually by two

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Insufficiently dried briquettes suggest a different degree of shrinkage between the surface and the core after firing, and that creates tension that leads to hairline cracks. These are going to give rise to complaints and can, if they go through the Going through moldings will cause the moldings to become unusable after firing, i.e. H. Are committee.

The drying that is predominantly used today is chamber drying, which can be used for all sound qualities. With this type of drying are in one, preferably in several Chambers of six to twenty m in length are used to place the moldings coming from the press and placed on supporting timber by means of a trolley retracted into the chambers, placed on ledges on the side walls and then subjected to drying. This requires depending on the amount and type of dry goods and depending on the length of the chamber, two to five days.

To reduce the drying time, drying air is continuously passed lengthways through the chamber or chambers, which is circulated by means of fans arranged in a return duct. : ■;:

The circulated dry air is supplied with dry hot air from a hot air duct, the amount of which depends on that in the drying chamber desired temperature can be regulated by means of a flap or in a similar manner. The resulting during the drying process Moist air, which is continuously supplied with hot air, is partly discharged into the open air or partly for re-heating fed to an air heater. It is also known to use steam-air heaters in the return duct for heating the circulating air to be provided.

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The chamber drying that has been customary up to now has considerable disadvantages. The circulating air flowing through the chambers is subject to a sharp drop in temperature on its way from entry to exit and at the same time a strong increase in moisture. The consequence of this is that those located near the entry of the circulating air Moldings are dry much earlier, often several days earlier, than those at the outlet of the circulating air Moldings. Since the duration of the drying period depends on the time required to dry the briquettes at the outlet, overall, the drying time is unnecessarily extended. As the for the evaporation of the contained in the formations The moisture required heat requirement is 950 to 1,100 kgcal / h even with the most modern chamber drying systems Extending the drying time results in excessive heat consumption.

In addition, the holes or other openings in the briquettes are usually located transversely to the circulating flow. Also at no matter how strong the current may be between the opposing ones Parts of the moldings do not form a sufficient pressure difference. This means that the The core of the molded product remains more humid than the outer surface for a long time, and the same adverse effects occur as discussed with respect to large volume drying.

In the case of tunnel dryers, the briquettes on supporting grids are preferred Longitudinally movable frames with appropriate spaces placed next to, on top of and behind one another and are used in the longitudinal or transverse direction through the tunnel hot air flowing through it. This warm air is circulated in a similar way to the chamber dryer and partly under Discharge of moist exhaust air through a return duct added or generated hot air to the desired drying temperature brought. These well-known tunnel dryers, which run approx.

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15Om are long have disadvantages similar to those above explained chamber dryer. With them, too, the briquettes are dried differently, since here the ones on the outside Dry briquettes faster than the internal briquettes, so that in turn all the circulated drying air up for drying the briquettes lying in the most unfavorable place through the tunnel, as well as on the already dry ones Formations must be passed. The dry season is therefore in turn lengthened by the time required to dry the moldings lying in the most unfavorable place.

During the entire dry season, the part of the circulating air discharged into the open air as exhaust air occurs considerably Heat losses because the dry air has a heat content of approx. 60 to 80 Kcal / kg. Finally flows through in In tunnel dryers, the circulated drying air generally does not touch the holes or other openings in the briquettes, see above that here, too, the possibility of the formation of damp spots inside the moldings and thus the risk of the formation of There are shrinkage cracks in the subsequent firing. Incidentally, the business interruptions during the weekends are a nuisance the drying process is so strong that an unacceptably large amount of waste is often produced.

The invention relates to drying systems for ceramic, in particular Coarse ceramic products with several drying chambers in which the dry goods are moved by fans Circulating medium is exposed and the circulating medium to supplement the amount of heat consumed during drying continuously a heating medium is added, and it aims at the disadvantages of the chamber dryer and tunnel dryer described above to avoid.

It consists first of all in that the drying system has one or

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several with humid air from 50 to 80 $ relative humidity has warm air chambers working as a circulating medium and a steam chamber working with slightly superheated steam as a circulating medium, and that different heating media are supplied to the circulating media in the upper mixing chambers of the chambers, namely with the warm air chamber (s) dry warm air from 60 to 80 ° and with the steam chamber strongly superheated steam of 200 up to 300 °.

It has been shown that by combining several warm air chambers with a steam chamber a substantial reduction of the drying times with a simultaneous strong reduction of the necessary heat energy is achievable. It has proven to be particularly practical when the ratio of the heated air Part of the available drying room to the part of the drying room operated with superheated steam 2: 1 is. In other words, it is advisable to use two thirds of the drying chambers or two thirds of the tunnel length as hot air dryers, and a third of the drying chambers or a third of the tunnel length to be designed as steam dryers.

According to the invention, the drying system for obtaining the as The heating medium for the strongly superheated steam used for the steam chamber is preferably an oil-heated counter-current steam superheater trained steam superheater, the circulating medium continuously fed from the upper mixing chamber of the steam chamber will. Since the same medium is constantly circulating in this arrangement and there is still little space in the counterflow steam heater claim and can be assembled closely with the steam chamber, so only short lines are required, works the system is very economical, d. H. with very good thermal efficiency.

In a meaningful development of the invention, the system

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for obtaining the heating medium for the hot air chamber or ₀ chambers serving hot air at least one, preferably formed as a bag heat exchanger air heater on the one hand continuously Umwälzmedium from the "or the mixing chambers of the hot air chamber or chambers and on the other hand, is supplied from the system itself derived heat media This also significantly improves the heat balance of the system.

It is of particular value if, according to the invention, part of the heat medium originating from the system itself is removed from the chamber extracted exhaust steam is. Experience has shown that the exhaust steam withdrawn from the steam chamber provides such a considerable amount Proportion of that required for the heating medium of the Tfiämaekasomern Thermal energy that saves up to $ 30 of the energy previously required will.

In a structural manner that enables close assembly, the exhaust steam removed from the steam chamber is, for example, replaced by a Steam-air heater designed as a lamellar heater passed through, in one of the heating medium for the warm air chamber flowed through, is arranged leading to the upper mixing chamber of this chamber pipe.

For the same purpose, the pocket heat exchanger becomes one end the exhaust air discharged from the upper mixing chamber of the warm air chamber, the exhaust steam heated by the lamellar air heater Steam chamber and possibly the flue gas of the countercurrent steam superheater while supply air is supplied and exhaust air is discharged at the other end. This arrangement has in addition to the structural Simplification has the advantage that the heat contained in the flue gas of the countercurrent steam superheater can also be used can.

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The utilization of the steam-_ It is used when drying chamber stored thermal energy The exhaust air from the cooling chamber is fed to the heating medium of the warm air chamber until the temperature of the Dry food has dropped to approx. 60 °.

A very simple structural design of the invention, which can easily be retrofitted in chamber dryers and tunnel dryers, is that the mixing chambers extending over the entire length of the drying chambers are each closed off by a partition opposite the lower drying chambers and several equally spaced as suction on both sides Centrifugal fans contain designed fans, which are connected via upper suction openings with a longitudinal channel each serving to supply the heating medium and via lower suction openings arranged in the partition wall with the lower drying room.

Preferably, regulating flaps that open and close alternately are hinged to the partition walls on both sides, a lateral downward flow of the mixed with the heating medium Cause circulation medium along the material to be dried, and that arranged on the underside of the material to be dried guide plates that direct the circulating medium down to the middle of the dry material and in this -vertically upwards.

Since with this design alternating increasing and decreasing currents of the circulating medium from the side across and lengthways to which the dry material and from bottom to top are passed through the dry material, there is a completely uniform Drying of all bricks so that the drying time is reduced. The above-mentioned guidance of the circulating currents still has the advantage that, regardless of the position of the briquettes, their holes and other openings are penetrated by the circulating medium.

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are flowing, so the previously occurring damp window be avoided inside the stack.

Further structural features of the invention emerge from the following description of an embodiment of a drying system according to the invention with three in a row arranged tunnel-like chambers, one operated with warm air Drying chamber, a drying chamber operated with superheated steam and a cooling chamber, which are based on the schematic Drawings is explained.

In these show

Pig. 1 a dry comb in cross section,

Pig. 2 the steam drying chamber and the cooling chamber with the associated heating and conveying units and the lines indicated by dash-dotted lines in side view and

Pig. 3 the hot air drying chamber with the heating and conveying units connected to it and the lines indicated.

In Pig. 1 is the structure of one of the tunnel-like drying chambers shown, it being noted that the steam drying chamber essentially coincides with the hot air drying chamber.

The drying chamber 1 is in a lower drying room 3 and an upper mixing room 4 are divided. In the lower drying room 3 are movable in the longitudinal direction , Abetzwagen 5 housed, the ten to twelve on top of each other have support grids 6 placed on webs for contactless placement of Pormlingen 7. Down next to the sales channels and below the lowest support grids 6 there are guide plates 8.

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arranges, which serve to bring the circulating medium flowing from above to below under the briquettes 7 and to pass through it from bottom to top.

In the upper mixing space 4, which extends along the top along the chamber 1, fans 9 designed as double-sided suction centrifugal impellers are installed at regular intervals of, for example, three to four meters, each with a suction opening 10 for sucking in a heating medium and one in the partition 2 Suction opening 11 for sucking in the circulating medium from the drying chamber 1 are assigned. The heating medium is fed to the suction opening 10 through a channel 12 which is connected to a distribution channel 13 extending over the length of the drying chamber 1. The circulating medium introduced into the mixing space 4 through the suction opening 11 is mixed with the heating medium in the mixing space 4 in order to replace the amount of heat consumed during drying in this way. The mixing space 4 is connected by means of transverse channels 14 to a collecting channel 15 into which the amount of the circulating medium displaced by the supply of the heating medium is diverted. The circulation medium heated by the heating medium in the mixing space 4 is fed into the lower part 3 of the drying chamber 1 through flaps 16 hinged to the side of the partition 2, which extend over the entire length of the drying chamber 1 and are periodically opened and closed by a worm drive 17 cause increasing and decreasing currents of the circulating medium. The suction through the suction opening 11 and the flaps 16 as well as their movements are dimensioned in such a way that the circulating medium flows through the drying chamber at a rate of from zero to a maximum of 12 m / sec. fluctuating speed and experiences a decrease in its temperature by about 6-10 °. This temperature loss is compensated for by adding the heating medium to the distribution channel 13. The amount of the supplied heating medium is not shown by means of one arranged in the supply line to the distribution channel

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Adjustable flap, preferably such that on each 4 - 6m circulating medium 1 m heating medium come.

The liquid withdrawn from the formations during drying in the shape of hot steam is through an additional line 18 discharged from the mixing space 4 ;.

As already mentioned above *, the structure described above for the tub air drying chamber A and for the steam drying chamber B is the same. Mmern This K a mainly differ from each other in that the Umwälzmedium the steam drying chamber B blended heating medium is greatly superheated steam, while the admixed the Umwälzmedium the hot air drying chamber A heating medium a very essential drying chamber by exhaust steam of the steam B of heated part of the Umwälzmediums DER chamber A is. -

The cooling chamber C is correct except for the lack of the mixing chamber and the means for processing and guiding the heating or circulating medium structurally coincide with the two chambers A and B. It is supplied with outside air in any way, and through the inside air heated to the dry material is drawn in through a connection 19 and can be mixed with the heating medium of the warm air drying chamber A.

With reference to Figs. 2 and 3, the generation, supply and distribution the heating media of the drying chambers A and B are described. Here, the structurally matching parts of the warm air drying chamber A and the steam drying chamber B with the same Designated reference numerals, which, however, by indices a and b must be distinguished from one another.

The generation of the heating medium in the form of superheated steam from 200 - 300 ° for the steam drying chamber B is used, see. Fig. 2,

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a countercurrent steam superheater 22, heated by means of an oil burner 20 and equipped with an induced draft fan 21, of the type as described and illustrated, for example, in German patent application P 16 79 378.5. A part of the circulating medium of the drying chamber B is removed from the collecting duct 15-u by means of a centrifugal fan 25 and fed to the superheater 22. The superheated steam generated in this is fed to the drying chamber B via the distribution channel 13-I ₅ as a heating medium. The superheated steam generated by evaporation in chamber B is sucked out of the mixing space 4 ^ of chamber B by means of a conveying fan 24 and used to heat the heating medium of the warm air drying chamber A in the manner described below.

The heating medium for this chamber A is fed to the distribution channel 13 _{O of} this chamber via a pipe 25 which is equipped with an axial fan 26, a lamellar steam air heater 27 and a side inlet 28.

The finned steam air heater 27 is the one from the mixing chamber 4b of the steam drying chamber B removed by the conveyor fan 24 Part of the circulating medium is fed in via a line 18. In the inlet 28 is from the cooling chamber C through the nozzle 19 removed warm air via a line 29 temporarily introduced. The removed from the collecting channel 15a of the chamber A part of the The circulating medium of this chamber is used together with that from the lamellar steam heater 27 exhaust steam and with that from the countercurrent steam superheater 22 through the draft fan 21 derived and fed through a line 30 flue gas by means of a fan 31 a pocket heat exchanger fed. This, in a corresponding number of adjacent, oppositely flowed through pockets made of metal dfer glass divided exchanger has a pocket width, for example from 10 - 15 mm, a height of 500 to 1000 m and a length

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from 4 "to 6 m. One end of it is the one conveyed by the fan 31 Exhaust air, steam and flue gas mixture are supplied, while fresh air is supplied at the other end by means of nozzles 33, 34 and exhaust air is discharged by means of a nozzle 35. The exhaust gas flowing through one part of the pockets of the exchanger 32, The steam and flue gas mixture heats the fresh air flowing through the secondary pockets in the opposite direction, and then the fresh air in the channel 25 by the lamellar steam air heater 27 further heated to about 70-80 ° and together with the via the line 29 Exhaust air fed into the inlet 28 is fed to the cooling chamber G via the collecting duct 13a and the mixing chamber 4a as a heating medium will.

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Claims (12)

192783S Claims IJ Drying system for ceramic, especially coarse ceramic products with several drying chambers, in which the material to be dried is exposed to a circulating medium moved by fans, a heating medium being continuously added to the circulating medium to supplement the amount of heat consumed during drying, characterized in that the drying system has one or more having humid air of 50 relative to 80 $ moisture acting as Umwälzmedium hot-air chambers (a) and one with a slightly superheated vapor working as Umwälzmedium steam chamber (B), and that the Umwälzmedien different in upper mixing chambers (4a> 4b) of the chambers (a, B) Heating media are supplied, namely with the warm air chamber or chambers (A) dry warm air from 60 to 80 ° and with the steam chamber (B) strongly superheated steam from 200 to 300 °. 2. Drying system according to claim 1, characterized in that one third of the available Otockenraumes, d. H. So the drying chambers of chamber dryers or the length of tunnel dryers, as a steam chamber (B) and two Thirds are designed as warm air chambers (A). 3. Drying system according to claims 1 and 2, characterized in that that they are used to obtain the heating medium for the steam chamber (B) serving strongly superheated steam preferably designed as an oil-heated countercurrent steam superheater (22), the continuously circulating medium is fed from the upper mixing chamber (4b) to the steam chamber (B). - 14 009849/1 1 U ' 192783 4. Drying system according to claims 1 TdIs 3, characterized in that that they serve as a heating medium for the warm air chamber or chambers (A) serving as warm air at least has an air heater (32), preferably designed as a pocket heat exchanger, on the one hand circulating medium from the mixing chamber or chambers (4a) of the warm air chamber or chambers (A) and on the other hand the system itself is supplied with heat media. 5. Drying system according to claims 1 to 4 _S, characterized in that part of the heat medium originating from the system itself from the steam comb he (B) is extracted exhaust steam. 6. Drying system according to claims 1 to 5 »characterized in that that the exhaust steam withdrawn from the steam chamber (B) is formed, for example, as a lamellar heater Steam-air heater (27) is passed through, in one of the heating medium for the warm air chamber (A) through which there is a pipe (25) leading to the upper mixing chamber (4a) of this chamber. 7. Drying system according to claims 1 to 6, characterized in that that the pocket heat exchanger (32) at one end is the one from the upper mixing chamber (4a) of the warm air chamber (A) discharged exhaust air, the exhaust steam from the steam chamber (B) heated by the lamellar air heater (27) and, if applicable, the flue gas of the countercurrent steam superheater (22) are supplied, while on the other hand supply air (33, 34) is supplied and exhaust air (35) are discharged. 8. Drying system according to claims 1 to 5 »characterized in that that the heating medium of the warm air chamber (A) in the pipe (25) additionally warm exhaust air from a cooling chamber (G) System is supplied. 009849/1114 - 15 - 9. Drying system according to claims 1 to 8, characterized in that that the mixing chambers (4a, 4b) extending over the entire length of the drying chambers (A, B) through one partition wall (2) each is closed off from the lower drying rooms (3) and several at equal intervals arranged, designed as double-sided suction centrifugal fans (9), which over upper suction openings (10) each with a longitudinal channel (13) serving to supply the heating medium and via lower, in the intermediate wall (2) arranged suction openings (11) with the lower drying room (3) are in communication. 10. Drying system according to claims 1 to 9> characterized in that alternating on both sides of the partition walls (2) hinged opening and closing control flaps (16) are that a lateral downward flow of the circulating medium mixed with the heating medium along the material to be dried (7) cause, and that on the underside of the material to be dried (7) baffles (8) are arranged, which the circulating medium guide it down to the middle of the material to be dried (8) and in it vertically upwards. 11. Drying system according to claims 1 to 10, characterized in that that the upper mixing chambers (4a, 4b) by means of side channels (14) with longitudinal channels (15a, 15b) for receiving the exhaust air or the exhaust steam are connected. 12. Drying system according to claims 1 to 11, characterized in that that the mixing chamber (4) of the steam drying chamber (B) with one or more outlets (18) for the through the evaporation of the moisture of the dry material displaced exhaust steam is provided. 009849 / 1-114 Blank page