Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
THERMAL PLANT
Document Type and Number:
WIPO Patent Application WO/2019/016751
Kind Code:
A1
Abstract:
A thermal plant (1) provided with a box-shaped frame (5) supporting a combustion chamber (10), a heat exchanger (20) aerially connected to the combustion chamber (10); an air supplying device (30) aerially connected to the heat exchanger (20); an exhaust duct (40) aerially connected to the heat exchanger (20) and air pre-heating members (50) for the air supplied to the heat exchanger (20); the air- supplying device (30) comprising a space (32) where a rotor (34) is arranged, the rotor being configured to take air from the outside of the space (32) and to supply it to the heat exchanger (20); the air supplying device (30) being carried by the frame (5) above the combustion chamber (10), and the air pre-heating members (50) comprise a first conductive partition (52) carried by the frame (5) in a fluid-tight manner between the combustion chamber (10) and the space (32), so as to keep them thermally connected.

Inventors:
BARBIERI, Roberto (VIA DOSSO 52/E, CAMPODARSEGO, 35010, IT)
Application Number:
IB2018/055381
Publication Date:
January 24, 2019
Filing Date:
July 19, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
AGREX SPA (VIA BALLA, 55/57, VILLAFRANCA PADOVANA, 35010, IT)
International Classes:
F24H3/00; F23C7/06; F23J15/06; F26B17/00
Domestic Patent References:
WO2015052364A12015-04-16
WO2003008887A22003-01-30
Foreign References:
US2109876A1938-03-01
US4771707A1988-09-20
GB2495274A2013-04-10
Attorney, Agent or Firm:
RONCUZZI, Davide (Via Antica Zecca 6, Ravenna, 48121, IT)
Download PDF:
Claims:
CLAIMS

1. A thermal plant (1) provided with a box-shaped frame (5) supporting a combustion chamber (10), a heat exchanger (20) aerially connected to said combustion chamber (10); air supplying means (30) aerially connected to said heat exchanger (20) ; an exhaust duct (40) aerially connected to said heat exchanger (20) and air pre-heating means (50) for the air supplied to said heat exchanger (20) ; said air supplying means (30) comprising a space (32) where a rotor (34) is arranged able to take air from the outside of said space (32) and to supply it to said heat exchanger (20) ; wherein said air supplying means (30) are carried by said frame (5) above said combustion chamber (10), and characterized in that said air pre-heating means (50) comprise a first conductive partition (52) carried by said frame (5) in a fluid-tight manner between said combustion chamber (10) and said space (32), so as to keep them thermally connected.

2. Plant according to claim 1, characterized in that said heat exchanger (20) comprises a plurality of tubes (22) contained inside a heating chamber (24) aerially connected to said space (32) , to said combustion chamber (10) and to said exhaust duct (40) .

3. Plant according to claim 2, characterized in that said heat exchanger (20) comprises a first collector (26) carried by said frame (5) below said combustion chamber (10) and aerially connected thereto, and a second exhaust collector (28) carried by said frame (5) at the top, at the side of said space (32); said tubes (22) being vertically arranged and aerially connected to said first collector (26) and to said second collector (28) .

4. Plant according to claim 3, characterized in that said heat exchanger (20) comprises fume extraction means (60) aerially connected to said second collector (28) .

5. Plant according to claim 4, characterized in that said heating chamber (24) comprises air conveying means (240) for the air supplied from said space (32) to said heat exchanger (20), suitable, in use, to convey air along a substantially sinusoidal path inside said heat exchanger (20) .

6. Plant according to claim 5, characterized in that said conveying means (240) define an air supplying area (24') facing said space (32), an air heating area (24'') above said first collector (26) and an air exhaust area (24''') facing said exhaust duct (40) inside said heat exchanger (20) .

7. Plant according to claim 6, characterized in that said conveying means (240) comprise a second partition (2400) carried by said frame (5) transversally to said tubes (22) below said first collector (26) so as to divide said heating chamber (24) at the top.

8. Plant according to any one of claims 4 to 7, characterized in that said fume extraction means (60) comprise at least one sucker (62) carried by said frame (5) above said exhaust area (24''') at opposite side from said space (32) with respect to said second partition (2400) .

9. Plant according to any one of claims 3 to 8, characterized in that said first collector (26) and said second collector (28) respectively comprise a first lid (260) and a second lid (28) for inspecting said tubes (22) .

10. Plant according to any one of the previous claims, characterized in that said frame (5) is movable by means of wheels (80) .

11. A dryer (100) for granular products, characterized by comprising a container (110) for said granular products and a thermal plant (1) for supplying heated air to said container (110); characterized in that said thermal plant (1) is constructed according to what described in at least one of claims 1 to 10.

Description:
THERMAL PLANT

DESCRIPTION

The present invention relates to a thermal plant. In particular, the present invention relates to a thermal plant that can be used for producing heat for technical uses. In more detail, the present invention relates to a thermal plant that can be used for producing heat for technical uses and is configured to be indifferently installed in drying devices or in industrial plants for the heating thereof.

BACKGROUND TO THE INVENTION

In the field of heat production for technical purposes, the use of thermal plants is well known; these plants are provided with a burner, whose combustion chamber is supplied with fossil fuel, usually coal; the fumes produced at high temperature are used for drying products or heating environments indirectly, through a heat exchanger. Not including herein the case of tube bundles whose fumes are used for drying products destined to be used as food not for people, as they are contaminated by the drying fumes, the heat exchangers for plants like that described herein comprise a plurality of parallel tubes (a tube bundle) , arranged between a supply collector and an exhaust collector, and a unit forcing air to transversally pass the space where the tube bundle is arranged, so that the air absorbs heat and can be used for the purposes described above. For the sake of practicality, this air will be called herein "technical air", for distinguishing it from the air taken from the outside. The heated air is forced to the outside by means of a suction unit, and is used for the technical purposes mentioned above (drying products or heating environments) . In the plants like those described, the tubes of the heat exchanger are usually arranged horizontally above the combustion chamber and are supplied by means of a duct connecting the combustion chamber and the heat exchanger. The air passing through the tube bundle of the heat exchanger is therefore the same air sucked inside the plant; this means that this air enters the tube bundle at outside temperature, thus causing a quick decrease in the inlet temperature, i.e. a very disadvantageous temperature gradient for the heat exchanger between the inlet collector and the exhaust collector, as this thermal gradient jeopardizes the tubes' useful life and decreases the heating step yield.

Moreover, combustion waste are suspended in the fumes generated by the combustion, like, just by way of non limiting example, ash, gases, fuel particulate matter. In particular, fuel particulate matter is chemically very active and tends to adhere to the side walls of the tubes, causing the corrosion thereof; moreover, it tends to agglomerate the carbon particles transported by the fumes. This waste accumulation causes a progressive reduction in the opening (free cross-section) of the tubes, thus reducing the flow rate thereof and jeopardizing the plant efficiency, requiring maintenance to recover the original opening, i.e. the original flow rate. The slower the speed of the fumes {in the tubes), the greater the waste adhesion to the tubes, and therefore the corrosion thereof, because the slow speed reduces the sweep-away effect.

Moreover, the waste adhesion degree is higher when the fume temperature is lower than the temperature required for the plant operation in steady-state condition, for example when the use of the plant is ending. If the tubes contain members increasing the fume turbulence, in order to maximize the time the fume pass through them and thus the heat transmission to the technical air, the waste deposition is facilitated, and the maintenance described above shall be performed very often; this means more stops of the plant and a reduced economical yield thereof.

It should be also taken into account that it should be useful to use biofuel for the burner, in order to minimize the ecological impact of the plant . The use of biomass especially minimizes the amount of carbon dioxide to the atmosphere resulting from combustion, with respect to fossil fuels; however, given the same thermal power introduced, in the case of biomass it is necessary to burn masses that are almost double with respect to the coil mass necessary to have the same thermodynamic result. This is an inconvenience, that entails greater costs for transporting the fuel and supplying it to the thermal plant; therefore, it is necessary to improve as much as possible the plant thermal balance, in order to optimize the economical advantage of using biomass. Any measure aiming at this allows to solve the problem of energetically optimizing this kind of thermal plants and makes the use of biomass economically advantageous for producing hot air for technical purposes.

Thermal plants according to the state of the art are known from the documents WO 2015/052364 Al, US 2 109 876 A, US 4 771 707 A, WO 03/008887 A2, and GB 2 495 274 A.

SUMMARY OF THE PRESENT INVENTION

The present invention relates to a thermal plant. In particular, the present invention relates to a thermal plant that can be used for producing heat for technical uses. In more detail, the present invention relates to a thermal plant that can be used for producing heat for technical uses and is configured to be indifferently installed in drying devices or in industrial plants for the heating thereof.

An object of the present invention is to provide a thermal plant that is easy and economical to be constructed, suitable to solve the problems of the prior art described above, as well as other problems that will be more apparent from the description below.

According to the present invention a thermal plant is provided, whose main features will be described in at least one of the appended claims.

A further object of the invention is to provide a dryer provided with a thermal plant that is easy and economical to be constructed, suitable to solve the problems of the prior art described above, as well as other problems that will be more apparent from the description below.

According to the present invention a dryer is further provided, whose main features will be described in at least one of the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

Further characteristics and advantages of the thermal plant and the dryer of the invention will be more apparent from the description below, set forth with reference to the attached drawings, that illustrate at least one non- limiting embodiment, where identical or corresponding parts are identified by the same reference numbers. In particular:

- figure 1 is a schematic perspective view of a thermal plant according to the present invention;

- figure 2 is a schematic side elevation view of the plant of figure 1, in use, with some parts removed for the sake of clarity;

- figure 3 is a schematic perspective view of figure 1, with some parts removed for the sake of clarity; - figure 4 is a schematic perspective view of a dryer provided of the thermal plant of figure 1; and

- figure 5 is a schematic plan view of figure 1 showing an enlargement of a detail thereof.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In figure 1, number 1 indicates, as a whole, a thermal plant provided with a box-shaped frame 5 equipped with wheels 80 in order to be easily transportable where necessary.

The plant 1 may be used for equipping a dryer 100 for drying granular products and is provided with a container 110 for the products, shown only in figure 4. In addition, from the description below it will be clearly apparent that the plant 1 can be also used to supply technical air at a given temperature to an industrial plant or to any other installation for living or industrial purposes selectively and without the need for any modifications. To this end, the plant 1 comprises a plurality of insulated panels 6 carried by the frame 5 and connected, at the respective sides, to one another and to the frame 5, in a known and not shown manner, for thermally delimiting, i.e. insulating, a parallelepiped-shaped space 7. According to figure 2, the plant 1 further comprises, inside the space 7 and supported by the frame 5, a combustion chamber 10, a heat exchanger 20 arranged at the side of the combustion chamber 10 and aerially connected thereto; an air supplying device 30 carried by the frame 5, arranged above the combustion chamber 10, at the side of the heat exchanger 20 and aerially connected thereto. The plant 1 further comprises, inside the space 7 and supported by the frame 5, an exhaust duct 40 arranged inside a chamber 70 provided at the side of the heat exchanger 20 at the same height as the air supplying device 30 and aerially connected to the heat exchanger 20. With particular reference to figures 1 and 5, the plant 1 comprises a fuel supplying group 2 having a hopper 3 connected to the combustion chamber 10 through a duct 3' supplied by an auger 3' ' or any other functionally similar member. With reference to figure 1 again, the hopper 2 is above a fan 4 that can be actuated by a rotary actuator 4' and is configured to supply air to the combustion chamber 10 through a duct 4''.

Above the combustion chamber 10, the space 7 has a supplying chamber 32, below simply called space 32, that is open both at the top and at the side towards the heat exchanger 20 and is engaged by the air supplying device 30. The air supplying device comprises an expansion member 36 containing a rotor 34 that can be actuated by means of an actuator 31 provided above a grilled top 33 of the space 32. The expansion member 36 extends substantially like a spiral and is constituted by a box-shaped body 37 provided with axial openings 38, only one of which is shown in figure 2. The box-shaped body 37 partially engages the space 32 that, for this reason, has two side portions 320 that are free and, in view of what described above, open at the top. The rotor 34 is therefore suitable to take air from the inside of the side portions 320 through the openings 38 of the expansion member 36, and to supply it to the heat exchanger 20.

With reference to figure 2 again, the plant 1 comprises a pre-heating member 50 suitable to increase the temperature of the air taken from the outside and to be supplied to the heat exchanger 20 by means of the air supplying device 30, in order to graduate the air temperature increase and avoid thermal shocks of the tubes 22, limiting the thermal stresses thereof. The pre-heating member 50 comprises a first conductive partition 52 carried by the frame 5 in a fluid-tight manner between the combustion chamber 10 and the space 32, in order to keep them thermally connected. It should be useful to note that the rotor 34 sucks air from the side portions 320 that are axial with respect to, and aerially connected to, the rotor 34. From a thermodynamic viewpoint, the side portions 320 are an upward prolongation of the combustion chamber 10, at lower temperature .

In view of what described above, the air taken by the rotor 34 between the side portions 320 of the space 32 may be heated by means of the first partition 52, through contact and irradiation, according to the temperatures of this first partition 52.

The heat exchanger 20 comprises a heating chamber 24 provided with a plurality of tubes 22 and aerially connected to the space 32, the combustion chamber 10 and the exhaust duct 40. In figure 2, the tubes 22 are arranged vertically between a first collector 26, carried at the bottom by the frame 5 and aerially connected to the combustion chamber 10, and a second collector 28, carried at the top by the frame 5 at the side of the space 32. With particular reference to figures 1-3, the heat exchanger 20 comprises fume extraction members 60 that are aerially connected to the second collector 28.

The heating chamber 24 comprises a second partition 2400, carried by the frame 5 transversally to the tubes 22 below the first collector 26, in order to subdivide, at the top, the heating chamber 24 into an air supplying area 24' facing the space 32, an air heating area 24'' above the first collector 26, and an air exhaust area 24''' facing the exhaust duct 40. The second partition 2400 can thus be intended as a conveying member 240 suitable to force the air supplied to the heat exchanger 20 to follow a substantially sinusoidal path between the tubes 22 (inside the heat exchanger 20) between geometrically determined thermal areas with given and gradually increasing temperatures, thanks to the use of the suckers 62 arranged on the exhaust area 24'' '.

The fume extraction means 60 comprise at least one sucker 62 carried by the frame 5 and, in particular, by a sheet 5' delimiting at the top the first collector 26, above the exhaust area 24''' at opposite side from the space 32 with respect to the second partition 2400. Actually, in the embodiment of figure 5, two suckers 62 are provided, both facing the tubes 22 in the exhaust area 24'''. In this way, the fumes produced in the combustion chamber 10 are also guided to the end of the first collector 26 opposite to the combustion chamber .10. This allows to supply hot fumes to the tubes 22 in an homogeneous manner, independently of the transverse position of the tubes 22 with respect to the first/second collector 26/28. This solution allows to prevent fumes from stagnating in the first collector 26, which would result in the accumulation of particulate matter or the like, and thus allows to increase the efficiency of the thermal plant 1 when producing technical air.

Especially in order to solve the problem of stagnation particulate matter brought by the fumes in the first collector 26 and the problem of maintaining the tubes for removing the agglomerates of carbon particles transported by the fumes, the first collector 26 and the second collector 28 comprise, respectively, a first lid 260 and a second lid 280; by removing these lids, in a known manner, it is possible to inspect the tubes 22, to blow pressurized air to the ends of the tubes, to remove any members axially increasing the fume turbulence in the tubes 22, and to remove any scaling by means of adequate tools. The use of the plant 1 described above is clearly apparent from the description above and does not require further explanations. However, it should be useful to specify that the plant 1 can be operated, and therefore can supply hot air at a given temperature, by adequately adjusting the amount of fuel supplied to the hopper 2 and the air flow supplied to the combustion chamber 10 through the air inlet 3, as well as the fume flow through the tubes 22, by acting on the suckers 62 (that can be selectively actuated singularly or in pair) as well as the flow of air taken by the expansion member 36 from the side portions 320 of the space 32. In particular, during the ignition of the thermal plant 1, in order to minimize the amount of heat taken from the fumes and thus facilitate the thermal balance of the combustion chamber 10, it should be useful to actuate only one sucker 62, actuating the second one only when the thermal plant 1 is operating in steady-state condition. Lastly, it is clearly apparent that variants and modifications can be done to the thermal plant 1 and the dryer 100 comprising it, described and illustrated herein, without however departing from the protective scope of the invention .

In view of what described above it is clearly apparent that the particular arrangement of combustion chamber 10, air supplying device 30, heat exchanger 20 and exhaust duct 40, and the sinusoidal path of the fumes inside the heat exchanger 20 due to the presence of the second partition between the tubes 22, make the thermal plant 1 particularly suitable for an economically advantageous use of biomass for producing hot air for technical purposes.