CH615991A5 - Dryer with separate drying chambers, with indirect heating, in particular for bricks - Google Patents

Description

The present invention relates to a dryer with separate drying chambers, with indirect heating, usable in general for all those products or substances that require total or partial drying, and in particular for 15 bricks.

It is known that in order to obtain an optimal drying of the bricks it is necessary that the humidity and the temperature are regulated according to a priori fixed values and determined according to theoretical and practical considerations.

20 Various types of dryers are known (with chambers, tunnels and others) in which a main collector is provided through which a fluid heated by known means is provided.

The ducts that bring heat to each core or to each drying zone depend on the aforementioned collector according to the type of dryer considered; said heat is transferred directly (then) the fluid is a gas) or indirectly (in this case the fluid can be water, steam, or other gases still) by means of known heat exchangers.

30 In both solutions, the heat content of the fluid leaving the drying area or from the heat exchanger which heats a drying area and is expelled, is very high and negatively affects the thermal efficiency of the dryer and this represents a significant drawback 35 which the present invention intends to overcome.

Further dryers are known in which the last drying chamber, the one at a higher temperature than the remaining chambers, is heated by means of a known type.

The hot air-hot water vapor mixture which forms 40 in the aforementioned chamber is sent to the heat exchangers (placed in series) of the chambers which precede at ordinarily lower temperatures; with the aforesaid heat exchangers heat is transferred to the drying chambers by also exploiting the latent heat of condensation of the water vapor contained in the hot air saturated in the cooling which took place through the exchangers themselves.

The exchange surface of each heat exchanger is determined so as to evaporate a predetermined rate of water contained in the bricks arranged in the 50 drying chamber where the same exchanger is provided; the hot and humid air which is present in the aforesaid chamber is continuously evacuated (for the reasons described above) and this represents a considerable drawback for the considerable quantity of heat transported by the aforementioned mixture.

55 Some of the aforementioned drawbacks have been overcome in the patent filed in the name of the same Applicant to the Italian patent application number 3487A / 76 in which a dryer of the type comprising at least two separate drying chambers not communicating with the outside 60 has been defended. maintained at different temperatures characterized in that it comprises: first heat exchanger means, communicating with a first drying chamber at a higher temperature, fed by the humid hot air not saturated with water vapor contained within the same first chamber. 65 ra, said heat exchanger means being provided for lowering the temperature of the humid hot air at least until the saturation of water vapor of the same humid hot air; second heat exchanger means, located inside the

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second drying chamber, placed in series with the aforementioned first heat exchanger means and supplied by hot air saturated with water vapor from the first heat exchanger means, called second heat exchanger means, provided with means for discharging the vapor of water condensed in them, flowing into the first drying chamber to send back into it the air saturated with water vapor that feeds them.

With the aforementioned dryer, in steady state, in any drying chamber, the heat necessary to evaporate a predetermined amount of water contained in the bricks placed to dry in the same chamber, is almost totally recovered and transferred, indirectly, to the drying chamber which above; moreover, this contributes to considerably improving the thermal efficiency of the dryer, since the heat transferred to any chamber, excluding the last one, is mainly due to the latent heat of condensation of the water vapor, the temperature of the hot air saturated of water vapor leaving the heat exchangers inside the aforementioned chamber is not much lower than the hot air of the following chamber (at higher temperature) and into which it flows. With the aforementioned dryer, no part of the heat transported by the hot air leaving the heat exchangers of the last drying chamber is recovered (the higher temperature one heated indirectly with known heat exchangers), nor any part of the heat contained in the hot air exiting the brick cooling chamber placed in line with the last drying chamber and this represents a drawback overcome by the present invention.

Another drawback, also overcome by the present invention, consists in the fact that no part of the heat transported by the air heated in the cooling of the first heat exchanger means is recovered in the aforementioned dryer.

The main object of the present invention is to overcome the drawbacks described above and in particular to provide a dryer which is structured so as to allow both the recovery of the heat transported by the hot air heated in the cooling of the bricks and by the hot air leaving the heat exchangers of the last drying chamber and the indirect transfer of the aforesaid heat to the drying chambers.

Another object of the present invention is to provide a dryer which satisfies the previous purpose and which also allows the recovery of the heat of the air heated in the cooling of the aforementioned first heat exchanger means.

Said objects and still others, are all achieved by the dryer according to the invention, comprising a plurality of adjacent and in-line drying chambers, separated, thermally insulated from each other, and with the outside, and further comprising at least one cooling chamber of the bricks in line and adjacent to the last drying chamber, said drying chambers being maintained at different temperatures ordinarily increasing from the first to the last drying chamber, of which the last drying chamber, the one with the highest temperature, is heated indirectly by means of heat exchangers, characterized in that it comprises: a plurality of interspaces suitable for at least partially wrapping each drying chamber, each of said interspaces being provided with at least two inlet and outlets for hot air respectively; a first collector, originating from the said cooling chamber of the bricks and flowing outwards with the terminal part, said first collector communicating with the outflow ports of the aforementioned cavities and with the inflow outlets of a part of the aforementioned cavities arranged consecutively starting from from the first drying chamber; a second collector communicating with one end with the outlet of the heat exchangers of the last drying chamber and leading, with the remaining end, into the first collector, said second collector also communicating with the inflow outlets not communicating with the aforementioned first collector and being supplied with hot air coming from said heat exchangers of the last drying chamber, and in turn supplying said inflow outlets communicating with it and the first collector with hot air; said first collector being further fed by the hot air coming from said cooling chamber of the bricks and from the outflow mouths of the aforementioned cavities, and in turn feeding the inlet outlets communicating with it.

The above characteristics and advantages of the invention will become clearer from the detailed description that follows of a preferred but not exclusive embodiment of the dryer in question, illustrated only by way of non-limitative example in the accompanying drawings, wherein: fig. 1 shows the top view of a horizontal section, according to the plane A-A of figs. 4a and 4b taken together, of the final portion of the dryer in question; the same figure also shows the view of the horizontal section of the initial portion of the same dryer, obtained with a plane (not shown) coinciding with the plane A-A;

fig. 2 shows the top view of a horizontal section, according to the plane B-B of figs. 4a and 4b taken together, of the final portion of the dryer in question; the same figure also shows the view of the horizontal section of the initial portion of the same dryer, obtained with a plane (not shown) coinciding with the plane B-B;

fig. 3 shows the top view, according to the plane G-G of figs. 4a and 4b taken together, of the final portion of the dryer; in said fig. 3 is also visible part of the third-last drying chamber (not obtainable from figs. 4a, 4b) which is structurally identical to the penultimate drying chamber;

fig. 4a shows the side view of a vertical section of the last drying chamber of the dryer and of the adjacent cooling chamber of the bricks, obtained with the two planes C-C of fig. 3;

fig. 4b shows the side view of a vertical section, according to the plane F-F of fig. 3, of the penultimate and last drying chamber of the dryer;

fig. 5 shows the side view of a vertical section, according to the plane H-H of fig. 2, of two chambers of the dryer not including neither the first nor the last;

fig. 6 shows the transverse view of a vertical section, according to the plane D-D of fig. 2, of the last drying chamber of the dryer;

fig. 7 shows the transverse view of a vertical section, according to the plane E-E of fig. 3, of the penultimate drying chamber of the dryer.

The aforementioned figures indicate the hot air flows affecting the dryer in question; more precisely:

R indicates the flow of hot air coming from the brick cooling chamber 54 and flowing into the collector 47;

with T the flow of hot air which, after having affected the heat exchangers 7 of the drying chamber 12, flows into the manifold 41 through the vents 40;

with Z the flow of hot air from the chamber 12 which, after having affected the external exchangers 21 and

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extensions 26 associated with chamber 11, returns again to chamber 12;

with V the flow of hot air which is taken from the outside and after having lapped the heat exchangers 21 flows, through the ports 46, into the manifold 47;

with S the flow of air that affects each interspace 50 enters the same interspace through the ports 51 and then flows, through the ports 52, into the manifold 47.

The aforementioned figures show a brick dryer, consisting of a plurality of drying chambers separated from each other by two doors 2 and not communicating with the outside; for understanding the present invention, the first drying chamber (the one with the lower temperature), the penultimate, the last drying chamber (the one with the higher temperature) and the cleaning chamber have been indicated with 10, 11, 12 and 54 respectively brick cooling.

On the floor 3 of the dryer and bilaterally with respect to the longitudinal axis of the same dryer, there are two pairs of tracks 4 for supporting and guiding the wheels of trolleys 42 each of which is loaded with a predetermined quantity of bricks 42a.

To limit the heat dispersion of the drying chambers towards the outside, the longitudinal wall 5 of the dryer, made of masonry, is made up of two parts between which a cavity 6 of air is left which, as is known, is a bad heat conductor.

The aforesaid last drying chamber 12 (the one with the higher temperature) is heated indirectly by means of two pairs of heat exchangers 7 arranged bilaterally with respect to the longitudinal axis of the dryer and near the walls 5 of the same chamber 12. Each of the aforementioned exchangers of heat 7 is constituted by a plurality of vertical tubes 8 which flow at the top into a supply manifold 9, and at the bottom into a collection manifold 13. The aforesaid exchangers 7 are fed with hot air T heated according to known techniques.

Said hot air T is conveyed to the aforesaid heat exchangers 7 by means of two ducts 14, one for each exchanger, located above the drying chamber 12 (see fig. 2); each conduit is placed in communication with the underlying supply manifold 9 of the corresponding heat exchanger 7, by means of three pipes 15.

The collection manifold 13 flows into the lower end part of a vertical channel 16 whose upper end part, through holes 40, communicates with a collector 41 arranged above the last and penultimate drying chamber 12 and 11 and whose function will be clarified below.

The temperature and speed of the hot air T which feeds the heat exchangers 7, together with the exchange surface of the exchangers themselves, must be chosen so that the quantity of heat transferred to the last drying chamber 12 is such as to allow, for a predetermined time, to evaporate a predetermined rate of water contained in the bricks arranged inside the same chamber 12; to improve the heat exchange between the hot air of the chamber 12 and the bricks 42a, fans 43 have been provided arranged inside the chamber 12, which create air currents directed against the bricks.

The air Z contained inside the chamber 12 (not communicating with the outside) heats up and humidifies.

Since the temperature in the chamber 12 must be constant, (to prevent the hot humid air Z contained in the same chamber from saturating with water vapor, which would prevent any further evaporation of water from the bricks), the same hot humid air Z not saturated with water vapor, it is conveyed to an intake manifold 19 by the suction action of a fan 20 arranged in the same manifold 19.

The fan 20 feeds a heat exchanger 21, of a known type, arranged above the dryer 1 with the aforesaid humid hot air Z not saturated with water vapor. 5 The aforesaid heat exchanger 21, invested by a current of cold air V created by a fan 22, is sized so as to decrease the temperature of the humid hot air Z until it saturates with water vapor.

The aforementioned cold air stream V is sucked in from the outside (by means of the fan 22 through a suction port 22a provided in a duct 44 and conveyed (warmer) by means of two ducts 45 and 46 in a manifold 47 arranged above the the dryer 1 and whose function will be explained in detail below (for the mutual connection between the ducts 44 and 46 see figs. 4 and 5).

The humid hot air Z saturated with water vapor leaving the heat exchanger 21, always by means of the fan 20, is conveyed into two ducts 23 which initially diverge and subsequently arrange themselves parallel to each other and equidistant from the longitudinal axis of the 'dryer (see fig. 2); valves 23a are provided in the diverging sections of the ducts 23 to regulate the speed and flow of hot air.

25 Each of the aforementioned ducts 23, in the section parallel to the axis of the dryer, is made communicating by means of three vertical pipes 24 with the supply manifold 25 of a heat exchanger 26 arranged inside the penultimate drying chamber Ile parallel to the axis of the ES-30 drier.

Since the humid hot air Z which feeds the two heat exchangers 26 is already saturated with water vapor, the further drop in temperature to which the same hot air Z is subjected when passing through the heat exchangers 26 35 (consisting of a plurality of vertical tubes connecting the supply manifold 25 with a collection manifold 27) leads to condensation of water vapor; the water produced by the aforesaid condensation is conveyed to the outside by means of a discharge duct 28 provided at the bottom in the collection manifold 27.

The water vapor that condenses inside the heat exchangers 26 wets the internal surfaces of the exchangers themselves, considerably increasing the heat transmission coefficient through the walls of the exchanger 45 and this allows, as is known, to limit the surface of exchange of the exchanger with the same temperature difference between the exchange surfaces and with the same heat transmitted through the same exchange surfaces.

Furthermore, since the heat transferred by the heat exchangers 26 to the penultimate drying chamber 11 is mainly due to the latent heat of condensation of the water vapor which condenses, the temperature of the hot humid air Z saturated with water vapor which it collects in the collection manifold 27 is not much lower than the temperature of the hot humid air Z leaving the last chamber 12 (on average 8-10 ° C less); said temperature difference, of course, can be further decreased by increasing the speed of the hot air Z through the heat exchangers 26 and this by acting on the valves 23a.

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The heat transferred to the chamber 12 (from the heat exchangers 7) must be spent almost entirely to evaporate a predetermined rate of water contained in the bricks arranged in the same chamber; the relative humidity does not increase as hot humid air Z feeds the heat exchangers 21 and 26 before being sent back to the same chamber 12 and in the latter condenses the same aliquot of water evaporated from the bricks arranged in the chamber 12 .

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With the dryer running, the heat necessary to evaporate the aforementioned rate of water from the bricks of the chamber 12 is almost entirely transferred (apart from the heat transferred outside by the exchangers 21 which averages around a few percent of the total heat exchanged and the small and inevitable outward dispersions) to the chamber 11 by means of the heat exchangers 26; it follows that the difference between the heat carried by the hot humid air 7 leaving the chamber 12 and the air saturated with water vapor sent to the chamber 12 is practically coincident with the heat transferred (by means of the heat exchangers 26)

to chamber 11; this is extremely advantageous for the overall efficiency of the dryer.

In the chamber 11, similarly to the chamber 12, fans 43 are arranged whose function is the same as for the fans 43 of the chamber 12.

From the above fig. 1 it can be noted that the last chamber 12, separated from the penultimate chamber 11 by means of the two doors 2, extends towards the chamber 11 by means of two compartments 29, each of which is delimited laterally on one side by walls 5a of an interspace 50 la whose function will be clarified below, on the opposite side by a wall 30 which also delimits laterally the space 38 between the two doors 2, and finally by a wall 31 provided laterally with an opening coaxial with the corresponding collection manifold 27; the walls 30 and 31 of each compartment 29 are made with thermally insulating material to avoid condensation of water vapor on them.

What has been described for the drying chambers 12 and 11 (respectively the last and the penultimate of the dryer) occurs for the chamber 11 and the third to last drying chamber (not visible in figs. 1 and 2); that is, the hot air Z not saturated with water vapor of the chamber 11 feeds the heat exchangers arranged in the third last drying chamber after supplying external heat exchangers placed on the roof of the dryer, and having the same function as the exchangers 21 visas for room 11.

Ultimately what happens between the chambers 12 and 11, i.e. the forced closed-loop circulation of hot humid air between the chamber 11, the heat exchangers 21, the heat exchangers 26 and the chamber 12, takes place between the chamber Ile la third-last drying chamber. Thus chain up to the first chamber 10 in which the internal and external heat exchangers 26 visible in figures 1 and 2 are supplied by the hot air of the second chamber 32.

The temperature and humidity inside the first chamber 10 are regulated to the desired value by sending an appropriate quantity of humid hot air of the same chamber 10 in forced circulation with closed loop (by means of a fan) through a heat exchanger 34 sized in so as to transfer a predetermined amount of heat to the outside and to condense a predetermined rate of water vapor to precisely regulate the temperature and humidity inside the chamber 10 to the desired values.

From figs. 1, 4a, 4b, 6 and 7, it is noted that each drying chamber is surrounded by an interspace 50 which affects the floor and the top of each chamber and the side walls of the same chamber parallel to the walls 5 of the dryer; the interspace of each drying chamber extends laterally until it affects the two compartments 29 associated with each chamber.

Each cavity 50 (see Figs. 3, 4a, 6 and 7) is provided with two series of inlet ports 51 arranged symmetrically with respect to the axis of the dryer 1 and two outflow ports 52 which are also symmetrical with respect to the aforementioned axis.

The inflow ports 51 of the penultimate and last drying chamber 11 and 12 communicate with the collector 41; the inflow ports of the remaining cavities communicate with a manifold 47 (see fig. 3). The outlets 52, located at a greater distance from the axis of the dryer 1 with respect to the outlets 51, communicate with the manifold 47; between the inflow ports 51 and outflow 52 of each drying chamber there is a valve 53 provided, as will be clarified below, for regulating the speed and the flow rate of hot air S circulating in the aforementioned cavity.

From figs. 6 and 7 and more clearly from fig. 3, the particular conformation of the aforementioned manifolds 41 and 47 is noted.

The manifold 41 originates above the last chamber 12 in correspondence with the holes 40 which flow into it; it has a width less than the width of the dryer 1 and extends in length so as to affect the last and penultimate chamber and then flows into the collector 47. The collector 47 which has the same height as the collector 41 and is laterally delimited by walls 55 in line with the walls of the dryer, it originates at the brick cooling chamber 54 and initially develops bilaterally to the collector 41 to then occupy the entire width of the dryer; the end part of the same manifold 47 communicates with the outside through evacuators 56.

The manifold 41 is fed by the hot air T leaving the heat exchangers 7 of the last chamber 12 and in turn feeds the inflow outlets 51 of the last and penultimate chamber 12 and 11, finally flowing into the manifold 47; the manifold 47 is also fed by the air R heated to cool the bricks located in the cooling chamber 54, by the hot air S coming from the outflow ports 52, by the hot air V heated in the cooling of the heat exchangers 21 outside the drier and in turn feeds, with hot air S, the inflow ports 51 of the cavities 50 from the first to the third last drying chamber.

As seen above, in normal operation in any drying chamber, the heat necessary to evaporate a predetermined rate of water contained in the bricks is almost entirely transferred, indirectly, to the preceding drying chamber.

The heat lost by the external exchangers 21 in their cooling, the heat necessary to heat the bricks and relative supports, and the inevitable heat dispersion through the walls delimiting each drying chamber, is compensated, in each drying chamber, by the heat transferred in indirectly to the same chamber with the hot air S circulating in the relative cavity; the quantity of heat transferred to each chamber is adjustable by acting on the relative valve 53. Ultimately, by acting only on valves 53 and 23a, the temperature in each drying chamber can be adjusted to the desired value and this is optimal for the brick drying process .

From what has been described above, it is clear that the invention in question fully satisfies the aims of the introduction; in fact the dryer is structured so as to allow both the recovery of the heat transported by the hot air R heated in the cooling of the bricks, by the hot air V heated in the cooling of the external exchangers 21 and by the hot air T leaving the heat exchangers. heat 7 of the last drying chamber, both the transfer, in an indirect and adjustable way, of the aforementioned heat to the drying chambers and this allows to increase the thermal efficiency of the dryer and to regulate to the desired value, together with the internal heat exchangers 26 and outside 21 of each drying chamber, the temperature in each drying chamber.

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Claims (6)

615991 1. Dryer with separate drying chambers, with indirect heating, in particular for bricks, comprising a plurality of adjacent and in-line, separate drying chambers, thermally insulated from each other and with the outside, and further comprising at least one cooling chamber (54) of the bricks (42a) in line and adjacent to the last drying chamber (12), said drying chambers being maintained at different temperatures, neatly increasing from the first to the last drying chamber, of which the last drying (12), the one at higher temperature, is heated indirectly by means of heat exchangers (7), characterized in that it comprises: a plurality of interspaces (50) adapted to wrap at least partially each drying chamber, each being of said interspaces (50) provided with at least two inlets (51) and outflow (52) for hot air respectively; a first collector (47), originating from the said cooling chamber (54) of the bricks and flowing outwards with the terminal part, said first collector (47) communicating with the outlets (52) of the aforementioned cavities (50) and with the inflow ports (51) of a part of the aforementioned cavities (50) arranged consecutively starting from the first drying chamber (10); a second collector (41) communicating with one end with the outlet of the heat exchangers (7) of the last drying chamber (12) and leading, with the remaining end, into the first collector (47), said second collector (41 ) also communicating with the inflow outlets (51) not communicating with the aforementioned first manifold (47) and being supplied with hot air from the said heat exchangers (7) of the last drying chamber (12) and supplying in turn, with hot air, the said mouths inflow (51) communicating with it and the first collector (47); said first manifold (47) being further fed by the hot air coming from the cooling chamber (54) of the bricks and from the outlets (52) of the aforementioned cavities (50), and in turn feeding the inlets (51 ) communicating with it. Dryer according to claim 1, comprising, for each of the drying chambers from first to penultimate, first heat exchanger means (21) located outside the corresponding drying chamber and communicating with the adjacent drying chamber at higher temperature from which they are fed with hot humid air not saturated with water vapor contained in the same adjacent chamber, said first heat exchanger means (21) being provided for lowering the temperature of said hot humid air at least until the saturation of water vapor of the same hot air, and second heat exchanger means (26), located inside the said corresponding drying chamber, placed in series with the first heat exchanger means (21) and fed by the hot air saturated with water vapor from the said first heat exchanger means (21), said second heat exchanger means (26) communicating with the aforesaid adjacent room drying at higher temperature to return the saturated air of water vapor which feeds them, characterized in that the aforementioned first manifold (47) is also supplied by the cooling air of the aforementioned first heat exchanger means (21). 2 3. Dryer according to claims 1 and 2, characterized in that it comprises adjustment means (53) for regulating the speed and flow rate of the hot air in the aforementioned cavities. Dryer according to the preceding claims, characterized in that each of the aforementioned cavities (50) wraps at least partially not more than one drying chamber. 5. Dryer according to claims 1, 2 and 3, characterized in that the aforementioned manifolds (47) and (41) are located above the drying chambers. 6. Dryer according to claims 1, 2 and 3, characterized in that the first collector (47) is initially consisting of two equal branches arranged bilaterally to the second collector (41). I