Dryer for lacquering facility

Abstract

The invention relates to a dryer for a lacquering facility: a) having a dryer housing, in which heated air is circulated, b) having an exhaust air line for a exhausting exhaust air from the dryer housing; c) having a combustion unit, which is connected to the exhaust air line, and which is used for thermal post-treatment of the exhaust air from the dryer housing and for providing hot air to a heat exchanger; d) wherein said heat exchanger is set up to supply said dryer housing with heated fresh air; and wherein e) at least one heating unit for heating the air circulated in said dryer housing is associated with said dryer housing. It is provided according to the invention that a combustion air supply of the heating unit is connected so it communicates with the dryer housing.

Claims

1. A dryer for a painting facility a) having a dryer housing, in which heated air is circulated; b) having an exhaust air line for removing exhaust air from the dryer housing; c) having a thermal combustion device, which is connected to the exhaust air line and which serves for thermal post-treatment of the exhaust air from the dryer housing and for providing heating air to a heat exchanger; d) the heat exchanger being set up to supply the dryer housing with heated fresh air; and e) at least one heater for heating the air circulated in the dryer housing being associated with the dryer housing, wherein f) a combustion air supply of the at least one heater is connected in a communicating manner to the dryer housing and is configured to intervene in a supporting manner with regard to a preheating and partial thermal treatment of the exhaust air from the dryer housing such that the thermal combustion device is capable of being deliberately under-dimensioned in capacity to a part-load of the capacity of the dryer, only.

2. The dryer of claim 1, wherein the at least one heater has an exhaust gas line for removing exhaust gases, which leads into the exhaust air line.

3. The dryer of claim 1, wherein at least one adjustable throttle device is arranged in the exhaust gas line of the at least one heater and/or in the exhaust air line upstream of the point where the exhaust gas line leads into the exhaust air line.

4. The dryer of claim 1, wherein an air supply line of the at least one heater has at least one branch for providing to the at least one heater a first exhaust air partial flow serving as a combustion air flow and a second exhaust air partial flow serving as a useful air flow.

5. The dryer of claim 1, wherein the at least one heater has a useful air inlet and a useful air outlet, which are connected in a communicating manner to the dryer housing.

6. The dryer of claim 1, wherein a plurality of heaters are arranged along the dryer housing.

7. The dryer of claim 6, wherein an air inlet and an air outlet are connected in a communicating manner in each case to air shafts arranged laterally on the dryer housing and provided with air-permeable wall sections.

8. The dryer of claim 1, wherein a hot air outlet of the heat exchanger is connected to an end region of the dryer housing.

9. The dryer of claim 1, wherein at least one heater is arranged above the dryer housing.

10. The dryer of claim 1, wherein a transverse extent of the at least one heater corresponds to a part of a transverse extent of the dryer housing.

11. The dryer of claim 1, wherein the thermal combustion device is designed for part-load operation of the dryer.

12. The dryer of claim 11, characterised in that the thermal combustion device is designed to produce 75 percent of the heating power required for maximum operation, based on maximum utilisation of the dryer.

13. The dryer of claim 1, wherein a hot air outlet of the heat exchanger is connected to a lock region of the dryer housing.

14. A dryer for a painting facility a) having a dryer housing, in which heated air is circulated; b) having an exhaust air line for removing exhaust air from the dryer housing; c) having a thermal combustion device, which is connected to the exhaust air line and which serves for thermal post-treatment of the exhaust air from the dryer housing and for providing heating air to a heat exchanger; d) the heat exchanger being set up to supply the dryer housing with heated fresh air; and e) at least one heater for heating the air circulated in the dryer housing being associated with the dryer housing, wherein f) a combustion air supply of the at least one heater is connected in a communicating manner to the dryer housing and the thermal combustion device is designed for part-load operation of the dryer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic illustration of a dryer having a thermal post-combustion device and a plurality of heating units,

(2) FIG. 2 shows a perspective illustration of a module of the dryer according to FIG. 1, provided with a heating unit,

(3) FIG. 3 shows a first sectional illustration of the module according to section plane A in FIG. 2,

(4) FIG. 4 shows a second sectional illustration of the module according to section plane B in FIG. 2.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(5) While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail one or more embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated.

(6) The dryer 10 illustrated schematically in FIG. 1 comprises a dryer housing 12, through which motor vehicle bodies (not illustrated) can be guided in continuous operation. Heated air is supplied to the dryer housing 12, in order to initiate and/or accelerate a drying process of a paint coating applied to the motor vehicle body and/or bring about crosslinking of the paint coating. In a cross-sectional plane oriented perpendicularly to the plane of the drawing in FIG. 1, the dryer housing 12 has a substantially rectangular cross-section, as can also be seen from the illustrations of FIGS. 2 to 4.

(7) Above the dryer housing 12 are arranged a thermal post-combustion device 14, as well as a plurality of identically constructed heating units 16 and a heat exchanger 18.

(8) The thermal post-combustion device 14 is a gas burner which mixes the exhaust air from the dryer housing 12, which air is provided via an exhaust air line 20 and an exhaust air fan 22 intended for conveying the exhaust air, with natural gas and burns the mixture. This results in a temperature increase, whereby the pollutants present in the exhaust air can be at least partially neutralised. The exhaust air treated by heating in the thermal post-combustion device 14 is delivered to the heat exchanger 18, intended for heating fresh air which is provided to the dryer housing 12. The fresh air is supplied via a fresh air fan 24 to the heat exchanger 18 and from there via fresh air lines 26 to the dryer housing 12, preferably at the entrance and exit of the dryer housing 12.

(9) The design of the thermal post-combustion device 14 is chosen such that a quantity of heat can be provided to the dryer housing 12 which is required for operation of the dryer 10 with approximately 75 percent utilisation. In addition, the thermal post-combustion device 14 is dimensioned such that the temperature attainable therein still reaches the temperature value required for the exhaust air withdrawn from the dryer housing 12, at maximum heating power of the thermal post-combustion device 14 and 75 percent utilisation of the dryer 10.

(10) In order to be able to ensure the supply of thermal energy sufficient for the drying and also the temperature necessary for the exhaust air purification in the thermal post-combustion device 14 during full-load operation, the heating units 16 are provided, and they are arranged as compact gas burner units on the roof of the dryer housing 12. Each of the heating units 16 has supply air and useful air lines 28, 31 connected in a communicating manner to the dryer housing 12. A combustion air line 34 branches off from the supply air line 28 and leads into a schematically illustrated burner 36 of the heating unit 16. There, the exhaust air from the dryer housing 12 flowing in through the combustion air line 34 is supplied, via a fuel line (not illustrated), with natural gas, which is burnt together with the exhaust air in the burner 36. The exhaust gases released in the process are passed through a heat exchanger 38 inside the heating unit 16 and discharged via an exhaust gas line 32, which is connected as a collecting line to all the heating units 16 and leads into the exhaust air line 20 at a junction 42.

(11) With the aid of the heat exchanger 38, a portion of useful air withdrawn from the dryer housing 12 via the supply air line 28 and a useful air line 30 branching off therefrom is heated, it being drawn in by means of a conveying fan 40 and after passing through the heat exchanger 38 and the conveying fan 40 being led via the useful air line 31 back into the dryer housing 12.

(12) During part-load operation of the dryer 10, the heat provided by the thermal post-combustion device 14 is sufficient for thermal treatment of the exhaust air and heating of the fresh air in the heat exchanger 18 to the required operating temperature of the dryer 10. Since the thermal post-combustion device 14 optimised for part-load operation cannot guarantee the heat supply alone during full-load operation of the dryer 10, the heating units 16 are activated in this case and supply additional heat to the dryer housing 12. Through the removal of exhaust air from the dryer housing 12 via the supply air lines 28 and the division, provided there, into a useful air flow and a combustion air flow, a part of the air circulated in the dryer housing 12 is intensely heated in the burners 36 of the heating units 16 during the combustion. Thus, already in the heating units 16, partial neutralisation of the pollutants accumulated in the exhaust air is guaranteed. The hot exhaust gas from the heating units 16 is supplied to the exhaust air line 20 via the exhaust gas line 32. As a result, the mixture composed of exhaust gases of the heating units 16 and the exhaust air withdrawn directly from the dryer housing 12 via the exhaust air line 20 has a markedly increased temperature level. Thus, during full-load operation and with a substantially constant heat supply in the thermal post-combustion device 14, the required temperature necessary for neutralising the exhaust gases can be maintained, despite the markedly higher exhaust air volume flow.

(13) In part-load operation, the dryer 10 is therefore operated solely with the heat supply of the thermal post-combustion device 14 and with capacity of the latter for exhaust gas post-treatment of the exhaust air from the dryer housing 12. In the case of full-load operation, the heating units 16 intervene in a supporting manner both with regard to the heat supply to the dryer housing 12 and with regard to the preheating and partial thermal treatment of the exhaust air from the dryer housing 12.

(14) The dryer 10 schematically illustrated in FIG. 1 is constructed from a plurality of dryer modules 44 connected in series, as illustrated in more detail in FIGS. 2 to 4. The dryer module 44 comprises a dryer housing section 15 and a heating unit 16 arranged on the roof of the dryer housing section 15. The dryer housing section 15 has a two-shell design. A dryer tunnel 46 is in this case bounded by vertically oriented perforated walls 48, floor plates 50 and ceiling plates 52. Formed between the perforated walls 48 and the outer walls 54, arranged spaced therefrom, are exhaust air shafts 56 and supply air shafts 58 which are in each case separated by bulkheads 61. These shafts serve for drawing off exhaust air from the dryer tunnel 46 and for supplying useful air to the dryer tunnel 46, respectively.

(15) The heating unit 16 is accommodated in an insulated housing 60 which, for its part, lies on the ceiling plates 52 of the dryer housing section 15. The heating unit 16 has a transverse extent perpendicular to a longitudinal axis of the dryer module 44 which is less than the transverse extent of the dryer housing section 15, so that a region accessible for maintenance work remains on both sides of the heating unit 16. Provided in the housing 60 are a first partition wall 62, a filter wall 64 and a further partition wall 66, the function of which will be explained in more detail below.

(16) Attached to an end-side outer wall 68 of the housing 60 is the burner 36, which is connected in a communicating manner to the exhaust air shaft 56 via the combustion air line 34 configured as a rectangular shaft and which additionally has a fuel line 70. In the burner 36, the exhaust air drawn off from the exhaust air shaft 56 through the combustion air line 34 is mixed with natural gas, supplied through the fuel line 70, and burnt. The exhaust gas released in the process is passed through the heat exchanger 38 and subsequently flows via the exhaust gas line 32 to the exhaust air line 20 (not illustrated in FIGS. 2 to 4).

(17) Attached to a second end-side outer wall 72 of the dryer housing section 15 is an electric motor (not visible), the motor shaft of which is connected in a rotationally fixed manner to a fan wheel 74 of a radial fan. The fan wheel 74 is arranged between the outer wall 72 and the partition wall 66, terminating at its front side with the partition wall 66. An intake opening, arranged in the partition wall 66, for the radial fan allows exhaust air to be drawn in through the filter wall 64. The exhaust air thus flows out of the dryer tunnel 46 through the perforated walls 48 into the exhaust air shaft 56. From there, a predominant part of the exhaust air is led past the heat exchanger 38 as useful air and heated in the process. Subsequently, the useful air flows through the filter wall 64, made of a porous filter cloth, behind which the fan wheel 74 creates a negative pressure. Owing to the pressure conditions caused by the rotating fan wheel 74, the heated and filtered air subsequently flows off into the supply air shafts 58. From there, the heated useful air can enter the dryer tunnel 46 again through filter mats 78 provided at the rear side of the perforated walls 48 and arranged spaced from the perforated walls 48.

(18) In the cross-sectional illustration of FIG. 3 it can be seen how the exhaust air drawn off from the dryer tunnel 46 through perforated walls 48 flows into the exhaust air shafts 56 and from there across ceiling plate 52 in the direction of the heat exchanger 38. A part of the exhaust air is drawn off into the combustion air line 34 by the burner 36 and used for the combustion of the burnable gas. The remaining exhaust air volume flow passes through the filter wall 64 (not illustrated) owing to the sucking action of the fan wheel 74, in order subsequently to flow into the supply air shafts 58 after flowing around the ceiling plate 52, in the manner illustrated in FIG. 4. From the supply air shafts 58, the heated useful air flows through the filter mats 78 of the perforated walls 48 into the dryer tunnel 46.

(19) In order to guarantee a compact configuration of the heating unit 16 and achieve an advantageous flow of the filtered and heated useful air, a floor 80 (visible in FIGS. 2 and 4) arranged spaced from the ceiling plates 52 of the dryer housing 12 is provided between the partition wall 62 and the partition wall 66. This floor 80 enables a distribution of the air flow, drawn in by the fan wheel 74, into the supply air shafts 58 arranged on both sides of the dryer tunnel 46.

(20) It is to be understood that additional embodiments of the present invention described herein may be contemplated by one of ordinary skill in the art and that the scope of the present invention is not limited to the embodiments disclosed. While specific embodiments of the present invention have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention, and the scope of protection is only limited by the scope of the accompanying claims.