DE10036774A1 - Furnace used for thermally cleaning waste gases produced during the treatment of workpieces has an eddying effect in the region of the combustion chamber so that waste gases produced - Google Patents

Abstract

Furnace (10) comprises a process chamber (12) for the thermal treatment of a material (18) inserted into the process chamber; a burner (26) arranged in a combustion chamber (14); and a hot gas channel (16, 17) for introducing as gas mixture burned in the combustion chamber into the process chamber. An eddying effect is produced in the region of the combustion chamber so that waste gases produced in the process chamber during the thermal treatment are suctioned off from the chamber into a flame of the burner as a consequence of the eddying effect. An Independent claim is also included for a process for thermally cleaning waste gases. Preferred Features: The burner is structured so that a flame produced by the burner expands in a plane vertical to the longitudinal axis of the burner.

Description

The invention relates to an oven with a process chamber for thermal treatment of an introduced into the process chamber Good, with a burner and arranged in a combustion chamber with a hot gas channel for introducing one into the combustion chamber burned gas mixture into the process chamber.

The invention also relates to a method for thermal Purification of exhaust gases that occur during the thermal treatment of a good introduced into a process chamber of a furnace.  

The thermal treatment of workpieces often results Exhaust gases that contain polluting pollutants and due to the stricter legal requirements no longer are allowed to get into the open without being cleaned. In hardening shops, for example wise arise when tempered, with an oil film covered steel parts exhaust gases that contain oil vapors during exhaust gases containing solvents when drying in paint shops attack. But also with other thermal treatment processes such as when roasting or burning out mold cores in of the foundry technology, environmentally harmful exhaust gases arise must be subjected to cleaning.

Both mechanical processes are used for cleaning which the exhaust gases are passed through a filter as well chemical processes for use. In the chemical process has in particular the so-called thermal afterburning Gained meaning. Here, the exhaust gases over a certain period of time at high temperature (approx. 800 ° C) kept, with constant supply of oxygen. at the high temperatures react in the exhaust gas Pollutants with the oxygen, being the reaction products in the essential carbon dioxide and water. These substances can then be safely released to the environment.

A furnace and a method of the type mentioned are out known from EP-B1-0 306 695. The oven described there has a combustion chamber that is connected to a hot gas duct with a Process chamber for thermal treatment of a broken in there ten good things. In addition to the hot gas duct is also an exhaust duct is provided, via which in the process chamber Exhaust gases are introduced into the combustion chamber. On  burner arranged in the combustion chamber holds with its Flame pulse starts a flow cycle at which hot gas from the combustion chamber into the process chamber and the one created there exhaust gases are returned to the combustion chamber.

Thermal afterburning takes place in this known furnace however not exclusively in the combustion chamber, but additionally also in one connected to the combustion chamber Post combustion chamber instead. The afterburning chamber borders thereby in such a way to the combustion chamber that it with this is heated, which in the afterburning chamber for thermal afterburning required temperatures without additional heating means can be achieved. However, it is additional post-combustion chamber required only for this reason Lich, because the thermal afterburning in the combustion chamber only runs incompletely. Only as a result of the additional Exhaust gases stay in the post-combustion chamber there is sufficient decomposition of the exhaust gases.

From DE-A1-30 31 935 is a furnace for thermal post-processing known combustion, also in a combustion chamber generated hot gas via a hot gas channel into a process chamber arrives. The exhaust gases generated in the process chamber become with With the help of an induced draft fan led back into the combustion chamber and burned there thermally. If the pollutant concentration tion in the exhaust gases exceeds a predetermined level a tangential burner switched on, in the flame of which swirl exhaust gases introduced and thermally decompose. A disadvantage of this furnace, however, is that in addition to the burner an additional burner for the thermi Afterburning must be provided.

The object of the invention is therefore, an oven of the beginning mentioned type in such a way that the above described disadvantages can be avoided. In particular, the No need for thermal afterburning a post-combustion chamber or additional burners hen. The object of the invention is also a method specify where the disadvantages mentioned avoided become.

In a furnace of the type mentioned above, this task solved according to the invention in that a Suction can be generated in a region of the combustion chamber is in extension of the longitudinal axis of the burner, and that Exhaust gases from thermal treatment in the process chamber arise as a result of the suction effect from the process chamber into a Flame of the burner to be sucked.

In a method of the type mentioned at the outset, this task is solved by the following steps:

• a) Burning a gas mixture in a combustion chamber under Use of a burner arranged therein, through which creates a suction effect in an area of the combustion chamber which is located in the extension of the longitudinal axis of the burner det;
• b) introducing the burned gas mixture into the process chamber via a hot gas duct;
• c) sucking the exhaust gases from the process chamber into a flame of the Burner due to the suction created by the burner;  
• d) at least temporarily deriving a portion of gases contained in the combustion chamber ( 14 ) via an outlet.

It has been shown that through various, even closer to explanatory measures is possible in an area before Burner to create a suction effect by the exhaust gases from the Process chamber sucked directly into the flame of the burner become. In this context, the Understood effect that a negative pressure compared to that in pressure prevailing in the process chamber. The exhaust gases can the process came, for example, through an opening in one wall separating the combustion chamber, but also above arbitrarily designed channels or pipes from the Process chamber are sucked into the area mentioned. It it is only necessary to ensure that the corresponding combustion chamber opening or mouth in or close enough the area from which the suction effect originates.

Due to the suction effect, at least for spatially narrow neighboring combustion and process chambers, the need that in the process chamber exhaust gases with the aid of a blower lead back into the combustion chamber. Most of all, however through the central feed of the exhaust gases immediately before the front end of the burner reaches the combustion chamber sucked exhaust gases completely into those generated by the burner Flame and due to the very high prevailing there Temperatures almost completely decomposed in a short time become. A post-combustion chamber can therefore, provided that there are no special circumstances, such as unusual strict legal exhaust gas regulations, usually waived become.  

It is also advantageous that in the furnace according to the invention thermal afterburning not only after preheating time, but already at the start of operations. This is due to the fact that the exhaust gases are directly in the Flame and not in a chamber to be heated decomposed, as is the case with the furnace, for example is known from the aforementioned EP-B1-0 306 695.

Most types of burners have a rotational symmetry cal, e.g. B. cylindrical, basic shape, so that the Brennerlängsach se coincides with the axis of symmetry of the burner. Most of time the gas is also supplied in this direction. Of that too distinguish is the direction in which the gas to be burned flow out of the burner mouth. This direction can lead to Burner longitudinal axis inclined or even perpendicular to it, such as this is the case for example with some swirl burners. at Burners whose basic shape is not or only approximately rotating is symmetrical, the axis is the burner longitudinal axis defined that passes through the burner and that is vertical to a combustion chamber wall in which the burner is installed is.

In one embodiment of the invention, it is particularly imminent moves if the burner is designed so that one by the Burner generated flame essentially in one plane spreads perpendicular to the longitudinal axis of the burner.

This has the advantage that burners designed in this way are self-sufficient dig create a suction effect in an area of the combustion chamber, which is in the extension of the longitudinal axis of the burner. By the almost radial spreading of the flame occurs in the  Center, d. H. in the area extending the Brenner Pass axis, a negative pressure, because the spreading in the plane Flame carries gases away from there.

In a further development of this embodiment, the burner designed as a swirl burner.

This has the advantage that the twists from the Gases flowing through the burner provide particularly good mixing of the sucked in exhaust gases with the flame and a uniform Flame spread is guaranteed within the combustion chamber.

In another embodiment of the invention are in the Combustion chamber deflection means arranged with which a flame out spread in a direction to the burner longitudinal axis essentially vertical plane is forced.

This has the advantage that the suction effect due to the the deflection of the flame-setting Coanda effect Lich is increased. This means that burners can also be used their design-related suction effect alone is not effective full suction of the exhaust gases from the process chamber is sufficient would.

In an advantageous development of this embodiment as a deflecting means, a deflector is provided, which is opposite the combustion chamber end face of the burner is arranged.

This has the advantage that with the help of the deflector practically all types of swirl or flat flame burners  Flame spread is forced to produce the desired suction effect leads.

It is preferred if the deflector has one with the Process chamber connected exhaust duct, the combustible mers mouth is located within the area in which the suction effect can be generated.

This has the advantage that additional pipes or the like. can be dispensed to the exhaust gases from the process chamber in the area where the suction is generated.

It is particularly preferred if the deflecting body Partition between the process chamber and the combustion chamber forms.

This has the advantage that it is structurally particularly simple Way, the thermal separation effect between the process chamber and the combustion chamber and the deflection to produce the suction effect is united in one component.

In an advantageous further development of this embodiment the deflecting body has a first, facing the combustion chamber Section and a second, facing the process chamber Section on, the first section being a higher tempera resistance to turbidity than the second section.

Such a structure of the deflector from parts with below Different material properties allow an optimal Adaptation to the functions of the deflector as one Partition, on the other hand as a deflecting agent for those from the burner generated flame. While the combustion chamber side  Section of the deflector due to the in the combustion chamber prevailing very high temperatures from a particular temperature resistant material should be made for the process chamber side portion of the deflector Material with lower temperature resistance, however better thermal insulation properties can be selected. Good thermal insulation makes it too strong Heat coupling between the combustion chamber and the process chamber avoid making the temperature in the process chamber easier becomes controllable.

The hot gas duct can be used for this purpose provided pipe connection between the combustion chamber and the Process chamber to be executed. In a particularly preferred However, the hot gas duct is developed through a gap formed between the deflector and an interior clothing one of the process chamber and the combustion chamber the housing remains.

This has the advantage that an oven according to the invention in essentially only from a housing and one fastened in it Deflector can consist of the inside of the housing Combustion chamber and the process chamber divided. At least partially remaining gap between the deflector and the Inner lining of the housing then forms the hot gas duct of the Oven.

In another embodiment of the invention, the Combustion chamber an outlet from which with a heat exchanger Preheating the combustion air supplied to the burner connected is. So the hot combustion products,  the thermal afterburning in the combustion chamber emerge, used in an effective manner to help the Preheat the combustion air supplied to the burner. The energy love The furnace can be considerably reduced in this way.

In a further advantageous embodiment of the invention is the hot gas duct through shut-off means at least partially shut off.

This has the advantage that the temperature in the process chamber regardless of the burner output within a short time can be reduced.

In a preferred development of this embodiment A control device provided for regulating the shut-off means hen, of a temperature arranged in the process chamber temperature data can be fed. This allows the Compliance with a temperature setpoint or a temperature setpoint curve in the process chamber without human intervention realize.

An embodiment of the invention is in the drawing shown and is described in more detail in the following description explained. It shows

Figure 1 in a longitudinal section an oven according to the invention in a simplified representation.

Fig. 2 shows the burner shown in Figure 1 in an enlarged section;

FIG. 3 shows a section along the line II-II through the burner shown in FIG. 2; and

Fig. 4 is a greatly simplified perspective view of another burner which is suitable for use in the furnace of Fig. 1.

In Fig. 1, an oven designed according to the invention is designated by 10 in total. The furnace 10 shown is intended for tempering steel parts and is part of a hardness reianlage, which has, inter alia, several ovens, quenching basins and conveyors arranged one behind the other. The material to be thermally treated, indicated by the rectangles 18 in FIG. 1, is covered due to a previous quenching process with an oil film which is evaporated in the furnace 10 in a process called tempering and is to be removed thereby.

For this purpose, in the manner of a continuous process, the material 18 is guided through a process chamber 12 of the furnace 10 on rollers 20 , which rotate in the direction indicated by the arrows 22 , in the direction of the arrow 24 . About the Prozesskam mer 12 is a combustion chamber 14 which is connected to the process chamber 12 via two hot gas channels 16 , 17 .

A burner 26 is arranged in the combustion chamber 14 , the longitudinal axis 28 of which is oriented perpendicular to the wall of the combustion chamber 14 . A combustion gas to be burned can be fed to the burner 26 via a gas feed line 30 . The burner 26 is also connected to an air supply line 32 which is guided via a heat exchanger 34 , so that the air supplied to the burner 26 can be preheated.

The process chamber 12 and the combustion chamber 14 are formed by a suitably lined housing 35 of the furnace 10 , which is divided into two chambers by a rectangular deflector 36 arranged inside the housing 35 . The process chamber-side part 38 of the deflector 36 consists of a thermally insulating material, while the combustion chamber-side part 40 is made of a high-temperature resistant material. The deflector 36 is provided in its center with a central through hole which forms an Abgaska channel 42 for exhaust gases formed in the process chamber 12 . The combustion chamber-side mouth 44 of the exhaust gas duct adjoins a suction region 45 , which is located in the combustion chamber 14 as an extension of the burner longitudinal axis 28 .

In the exemplary embodiment shown, the deflection body 36 merges seamlessly into the housing 35 in the direction facing the viewer and on the opposite side and is anchored therein. On the other two sides, gaps remain between the deflection body 36 and the inner lining of the housing 35 , which gaps form the two hot gas channels 16 , 17 . The two hot gas channels 16 , 17 can be shut off continuously by means of flaps 46 , 48 , as a result of which the temperature in the process chamber 12 can be changed. For this purpose, the control flaps 46 , 48 are connected to a control device 50 , which in turn receives temperature data from a temperature sensor 52 arranged in the process chamber 12 . The temperature data can be transmitted between the temperature sensor 52 and the control device 50 in a wired or wireless manner.

The combustion chamber 14 is also provided with an outlet 54 which is connected to a chimney 56 via the heat exchanger 34 .

The function of the furnace 10 according to the invention will now be explained in the following.

The burner 26 generates a flame which does not propagate in the longitudinal direction 28 of the burner 26 , but rather at an angle or even perpendicular to it. The burner 26 , which is described below with reference to FIGS. 2 and 3, is a conventional swirl burner, as is known, for example, from DD-A1-268 046 or DD-A1-210 412. The flame generated by the burner 26 is deflected sideways by the deflecting body 36 such that it spreads essentially in a plane perpendicular to the longitudinal axis 28 of the burner. The hot gas generated then flows into the process chamber 12 in the direction indicated by the arrows 60 due to the pulse generated by the flame.

Since the flame does not spread in the direction of the burner longitudinal axis 28, but approximately perpendicular thereto, is formed immediacy bar upstream of the burner 26 in extension of the longitudinal axis of the burner 28, a suction area 45 in which the pressure due to the entrained gas from the flame is lowered. The outgoing suction through this suction area 45 causes exhaust gases from the process chamber 12 (see arrows 62 ) to be sucked in through the exhaust duct 42 into the suction area 45 and from there are entrained by the flame generated by the burner. Since the arrangement shown in FIG. 1 is approximately radially symmetrical in the area of the burner, the sucked-in exhaust gases are distributed uniformly in the burner chamber filled by the flame. This also ensures that no exhaust gas passes the flame and thus only partially burned to the outlet 54 and finally reaches the surroundings via the chimney 56 .

In the illustrated embodiment, the temperature in the process chamber 12 is about 650 ° C and in the combustion chamber 14 about 1000 ° C. To regulate the temperature in the Prozesskam mer 12 , the flaps 46 , 48 are used, with which the two hot gas channels 16 , 17 can be shut off completely or partially. The position of the control flaps 46 , 48 required for setting a target temperature is determined by the control device 50 using the temperature data supplied by the temperature sensor 52 .

The thermally post-combusted exhaust gases, after having been reheated in the combustion chamber 14 , reach the process chamber 12 of the furnace 10 again via the hot gas channels 16 , 17 . In part, they also escape through the outlet 54 and give off part of their heat to the heat exchanger 34 , as a result of which this amount of heat is still available to the process.

In FIGS. 2 and 3 of the burner is shown in a longitudinal section and a section along the line II-II 26th The burner 26 is a swirl burner that generates a swirled flame that spreads out flat from the burner opening 68 . Swirl burners are therefore sometimes referred to as flat flame burners.

The burner 26 has an outer tube 70 and a double-walled inner tube 72 received coaxially therein. The outer wall of the inner tube 72 is provided with a nozzle 74 , through which gas can be introduced into the space 76 formed by the walls of the inner tube 72 . The space 76 is closed towards the burner opening 68 by a gas swirl ring 78 which is provided with through bores 80 all around. Through the through bores 80 , gas can escape from the intermediate space 76 into a mixing space 81 located below the gas swirl ring 78 .

A nozzle 82 formed on the outer tube 70 serves for supplying combustion air into an intermediate space 84 formed between the outer tube 70 and the inner tube 72 . At the lower end of the intermediate space 84 , baffles 85 are fastened between the outer tube 70 and the inner tube 72 , which, as can be clearly seen in FIG. 3, are arranged inclined to the longitudinal axis 28 of the burner. The combustion air supplied via the connecting piece 82 thereby receives a swirl when entering the mixing chamber 81 and entrains the gas emerging from the through bores 80 in such a way that a flame flowing in the direction of the arrows 86 is formed. The flame lies flat against a burner block 88 , which widens like a funnel in front of the burner opening 68 . As a result, the burner longitudinal axis 28 of the above-mentioned suction area 45 forms ahead of the torch 26 in extension from. In order to strengthen the swirl of the flame, the through bores 80 in the gas swirl ring 78 can also be designed to be inclined in a corresponding manner to the longitudinal axis 28 of the burner.

In Fig. 4, an alternative embodiment for a burner is shown in a greatly simplified perspective presen- tation, which is suitable for the furnace according to the invention in addition to conventional swirl or flat flame burners. The longitudinal axis 128 of the burner 126 is predetermined by the direction of the gas feed line 130 and the air feed line 132 . At the lower end of the two feed lines 130 , 132 there is a mixing chamber 90 in which the gas to be burned is mixed with the air. Several arms 92 extend from the mixing chamber 90 in the radial direction, ie perpendicular to the longitudinal axis of the burner. At the end of the arms 92 , nozzles 94 are provided, from which the gas / air mixture flows out in the direction indicated by the arrows 96 . In this way, the burner 126 creates a flame that spreads in the plane defined by the arms 92 .

The gas / air mixture flowing out at the nozzles 94 entrains the gas in the vicinity of the nozzles 94 , so that when the upper part of the burner 26 is inserted into a housing 35 of the furnace 10 as shown in FIG. 1 a suction area 145 forms the underside of the burner 126 .

To produce a swirl effect, the arms 92 can have an additional curvature, so that the gas flow emerging from the nozzles 94 receives an additional Tangentialkom component.

In the burner 126 shown in FIG. 4, an additional deflector 36 is fundamentally not necessary, since the suction region 145 forming below the burner 126 is generally so pronounced that the exhaust gases arising in the process chamber 12 can be extracted. However, if the arms 92 of the burner shown in FIG. 2 are not arranged perpendicularly, but at a smaller angle than 90 ° to the longitudinal axis of the burner, the flames do not form in one plane, but along a conical surface. In these cases, it may be appropriate to use a deflector 36 , as shown in FIG. 1, to reinforce the suction effect.

Claims (15)

1. A furnace (10) having a process chamber (12) for the thermal treatment of an introduced into the process chamber (12) Good (18), with a being arrange in a combustion chamber (14) th burner (26, 126) and with a hot gas duct (16 , 17 ) for introducing a gas mixture burned in the combustion chamber ( 14 ) into the process chamber ( 12 ), characterized in that a suction effect in a region ( 45 , 145 ) of the combustion chamber ( 14 ) can be generated by the burner ( 26 , 126 ) is in the extension of the longitudinal axis of the burner ( 28 , 128 ), and that exhaust gases that arise during thermal treatment in the process chamber ( 12 ), due to the suction effect from the process chamber ( 12 ) into a flame of the burner ( 26 , 126 ) are sucked ( 62 ). 2. Oven according to claim 1, characterized in that the burner ( 26 , 126 ) is designed such that a flame generated by the burner ( 26 , 126 ) spreads substantially in a plane perpendicular to the longitudinal axis of the burner ( 28 , 128 ) , 3. Oven according to claim 2, characterized in that the burner ( 26 ) is designed as a swirl burner. 4. Furnace according to one of the preceding claims, characterized in that in the combustion chamber ( 14 ) deflection means ( 36 ) are arranged, with which a flame propagation in a to the burner longitudinal axis ( 28 , 128 ) is substantially perpendicular right plane. 5. Oven according to claim 4, characterized in that a deflecting body ( 36 ) is provided as the deflecting means, which is arranged opposite the combustion chamber-side end of the burner ( 26 , 126 ). 6. Oven according to claim 5, characterized in that the deflecting body ( 36 ) has a verbun with the process chamber ( 12 ) which exhaust duct ( 42 ), the combustion chamber-side mouth is arranged within the region ( 45 , 145 ) in which the suction effect can be generated is. 7. Oven according to one of claims 5 or 6, characterized in that the deflector ( 36 ) forms the partition between the process chamber ( 12 ) and the combustion chamber ( 14 ). 8. Oven according to claim 7, characterized in that the deflecting body ( 36 ) has a first, to the combustion chamber ( 14 ) send section ( 40 ) and a second, to the process chamber ( 12 ) facing section ( 38 ), the first section ( 40 ) has a higher temperature resistance than the second section ( 40 ). 9. Oven according to one of claims 5 to 8, characterized in that the hot gas channel ( 16 , 17 ) is formed by a gap between the deflector ( 36 ) and an inner lining of the process chamber ( 12 ) and the combustion chamber ( 14th ) receiving housing ( 35 ) remains. 10. Oven according to one of the preceding claims, characterized in that the combustion chamber ( 14 ) has an outlet ( 54 ) which is connected to a heat exchanger ( 34 ) for preheating the combustion air supplied to the burner ( 26 , 126 ). 11. Oven according to one of the preceding claims, characterized in that the hot gas channel ( 16 , 17 ) by at least blocking means ( 46 , 48 ) can be at least partially shut off. 12. Oven according to claim 11, characterized in that for regulating the shut-off means ( 46 , 48 ) a control device ( 50 ) is provided, from a temperature sensor ( 52 ) arranged in the process chamber ( 12 ) temperature data can be supplied. 13. A method for the thermal purification of exhaust gases which arise during the thermal treatment of a material ( 18 ) introduced into a process chamber ( 12 ) of a furnace ( 10 ), characterized by the following steps:

• a) Burning a gas mixture in a combustion chamber ( 14 ) using a burner arranged therein ( 26 , 126 ), through which a suction effect in a loading area ( 45 , 145 ) of the combustion chamber ( 14 ) is generated, which is an extension of the Longitudinal burner axis ( 28 , 128 );
• b) introducing ( 60 ) the burned gas mixture into the process chamber ( 12 ) via a hot gas channel ( 16 , 17 );
• c) sucking ( 62 ) the exhaust gases from the process chamber ( 12 ) into a flame of the burner ( 26 , 126 ) due to the suction effect generated by the burner ( 26 , 126 );
• d) at least temporarily deriving a portion of gases contained in the combustion chamber ( 14 ) via an outlet ( 54 ).

14. The method according to claim 13, characterized in that a flame propagation in a to the burner longitudinal axis ( 28 , 128 ) substantially perpendicular plane with the help of in the combustion chamber ( 14 ) arranged deflection means ( 36 ) is forced. 15. The method according to any one of claims 13 or 14, characterized in that the burner ( 26 , 126 ) supplied Ver combustion air is preheated in a heat exchanger ( 34 ) in which the via the outlet ( 54 ) from the combustion chamber ( 14 ) derived Gases give off at least part of their heat.