METHOD FOR EXHAUST GAS TREATMENT, AND SYSTEM COMPRISING AN EXHAUST GAS TREATMENT DEVICE

Abstract

A method for treating exhaust gas in an exhaust gas treatment device of a system may involve withdrawing exhaust gas from a processing device for mechanically and/or thermally processing an inorganic material of the system. The material to be fed to the processing device may be preheated by heat exchange with the exhaust gas. Further, a temperature of the exhaust gas entering the exhaust gas treatment device may be adjusted by adapting the exchange of heat between the exhaust gas and the inorganic material. In some examples, the exhaust gas treatment device may comprise an oxidation catalytic converter and/or a reduction catalytic converter.

Claims

1.-19. (canceled)

20. A method for treating exhaust gas in an exhaust gas treatment device of a system, the method comprising: withdrawing the exhaust gas from a processing device of the system for at least one of mechanically or thermally processing an inorganic material; preheating the inorganic material to be fed to the processing device by heat exchange with the exhaust gas; and adjusting a temperature of the exhaust gas entering the exhaust gas treatment device by adapting the heat exchange between the exhaust gas and the inorganic material.

21. The method of claim 20 further comprising adjusting the temperature of the exhaust gas entering the exhaust gas treatment device by adapting heat generation in the processing device.

22. A system comprising: a processing device for at least one of mechanically or thermally processing an inorganic material; an exhaust gas treatment device following the processing device relative to a direction of flow of the exhaust gas originating from the processing device; a material preheater disposed between the processing device and the exhaust gas treatment device in which heat transfer from the exhaust gas to the inorganic material occurs, wherein a first inlet for the inorganic material is disposed upstream of a heat exchanger stage of the material preheater relative to a direction of flow of the inorganic material through the material preheater, wherein a second inlet for the inorganic material is disposed downstream of the heat exchanger stage of the material preheater relative to the direction of flow of the inorganic material through the material preheater; and a control device for distributing the inorganic material between the first inlet and the second inlet to influence a temperature of the exhaust gas entering the exhaust gas treatment device.

23. The system of claim 22 wherein the processing device includes a heat generating device, with a heat supply from the heat generating device is adjustable by way of a control device.

24. The system of claim 23 wherein the control device is configured as a regulating device that regulates at least one of the distribution of the inorganic material or the heat supply to the exhaust gas from the heat generating device depending on a target temperature range for the exhaust gas entering the exhaust gas treatment device.

25. The system of claim 22 wherein the material preheater is configured as a cyclone preheater.

26. The system of claim 22 wherein the exhaust gas treatment device comprises a catalytic device.

27. The system of claim 26 wherein the catalytic device comprises at least one of an oxidation catalytic converter or a reduction catalytic converter.

28. The system of claim 27 wherein the temperature of the exhaust gas entering the oxidation catalytic converter of the exhaust gas treatment device is between 150 C. and 650 C.

29. The system of claim 27 wherein the temperature of the exhaust gas entering the reduction catalytic converter of the exhaust gas treatment device is between 150 C. and 420 C.

30. The system of claim 27 wherein the oxidation catalytic converter is disposed upstream of the reduction catalytic converter with respect to the direction of flow of the exhaust gas.

31. The system of claim 30 further comprising a dosing device for a reducing agent disposed between the oxidation catalytic converter and the reduction catalytic converter.

32. The system of claim 30 further comprising a cooling device for the exhaust gas disposed between the oxidation catalytic converter and the reduction catalytic converter.

33. The system of claim 32 wherein the cooling device comprises a dosing device for water or an aqueous solution.

34. The system of claim 30 further comprising: a dosing device for a reducing agent disposed between the oxidation catalytic converter and the reduction catalytic converter; and a cooling device for the exhaust gas disposed between the oxidation catalytic converter and the reduction catalytic converter, wherein the cooling device comprises a dosing device for water or an aqueous solution, wherein the dosing device for the reducing agent and the dosing device for water or the aqueous solution are configured integrally as an integral dosing device.

35. The system of claim 34 wherein the integral dosing device has no return line for a mixture comprising water and reducing agents from an injection device to a reservoir of the integral dosing device.

36. The system of claim 22 further comprising a dust removal device for the exhaust gas treatment device.

37. The system of claim 22 further comprising a dust filter for the exhaust gas that is positioned directly upstream or directly downstream of the exhaust gas treatment device in the direction of flow of the exhaust gas.

38. The system of claim 22 wherein the exhaust gas treatment device comprises a device for thermal oxidation.

39. A system comprising: a processing device for at least one of mechanically or thermally processing an inorganic material; an exhaust gas treatment device downstream of the processing device; a material preheater that is disposed between the processing device and the exhaust gas treatment device and includes at least one heat exchanger stage, wherein heat transfer from the exhaust gas to a portion of the inorganic material occurs in the at least one heat exchanger stage of the material preheater; and a control device for controlling the portion of the inorganic material that is fed through the at least one heat exchanger stage of the material preheater to influence a temperature of the exhaust gas entering the exhaust gas treatment device.

Description

[0034] In the following, the invention is explained in greater detail with reference to the illustrative embodiment represented in the drawings. In the drawing,

[0035] FIG. 1 shows a schematic representation of a system according to the invention.

[0036] The system shown in FIG. 1 is used for the production of cement clinker by firing raw cement meal in a processing device in the form of a rotary kiln 1. For this purpose, the finely ground raw cement meal, which comprises organic components, is dispersed in hot combustion gases originating from the rotary kiln 1 and an optionally present calcinator (15), with the organic components being expelled from the raw cement meal and incompletely burned.

[0037] A material preheater 2 in the form of a multistage cyclone preheater with an integrated calcinator 15 is arranged upstream of the rotary kiln 1 relative to the direction of flow of the material (raw cement meal or cement clinker). In the material preheater 2, exhaust gas from the rotary kiln 1 flows through the raw cement meal in a plurality of stages, the meal is carried along, and it is then re-separated from the exhaust gas stream in a cyclone of the respective preheater stage. As is common, the cyclone preheater has a vertical structure so that the raw cement meal, to the extent that it is carried along by the exhaust gas stream, is primarily moved opposite to the direction of gravity, and after separation in the cyclones, falls due to gravity into the next preheater stage. Other common types of preheating, e.g. by means of staged residence time reactors, are also possible.

[0038] The raw cement meal is fed via a raw cement meal feeder 3 into the system and supplied to the material preheater 2. In the process, the raw cement meal is distributed to a first inlet 4 arranged upstream of the first (in this case the upper) heater exchanger stage 6 relative to the direction of flow of the raw cement meal through the material preheater 2 and a second inlet 5. The raw cement meal fed via this first inlet 4 into the material preheater 2 therefore undergoes heat exchange with the exhaust gas in this first heat exchanger stage 6 (and all other heat exchanger stages). The second inlet 5 is arranged downstream of the first heat exchanger stage 6 relative to the direction of flow of the raw cement meal through the material preheater 2. The raw cement meal fed via this second inlet 5 into the material preheater 2 therefore does not undergo heat exchange with the exhaust gas in the first heat exchanger stage 6, but does undergo heat exchange in all other heat exchanger stages. If part of the raw cement meal does not pass through all of the heat exchanger stages, the total heat transfer from the exhaust gas to the material to be preheated remains below a system-specific and operating parameter-dependent maximum, which affects both the temperature of the preheated raw cement meal and the temperature of the exhaust gas exiting the material preheater 2.

[0039] The volume of the raw cement meal streams fed via the first inlet 4 and the second inlet 5 into the material preheater 2 can be adjusted as needed by means of a control device 7. This therefore allows adjustment as needed of the temperature of the exhaust gas exiting the material preheater 2, which is then fed to an exhaust gas treatment device 8 having a catalytic device. Specifically, the control device 7 is configured as a regulating device which, depending on a measured temperature of the exhaust gas entering the exhaust gas treatment device 8, regulates the volume of the raw cement meal flow fed into the material preheater 2 via the first inlet 4 and the second inlet 5 in such a way that the measured exhaust gas temperature is within a target temperature range. Here, this target temperature range is selected so as to achieve the greatest possible reduction rate of pollutants by means of a multilayer oxidation catalytic converter 9 of the exhaust gas treatment device 8.

[0040] A multilayer reduction catalytic converter 10 is arranged downstream of the oxidation catalytic converter 9 in the direction of flow of the exhaust. This is based on the principle of selective catalytic reduction of nitrogen oxides in particular. For this purpose, a reducing agent in the form of ammonium hydroxide is added to the exhaust gas in a known manner upstream of the reduction catalytic converter 10 (and downstream of the oxidation catalytic converter 9), which as a reducing agent is characterized in particular, compared to (the also possible use of) urea as a reducing agent, by a shorter evaporation path. In addition, on decomposition, urea would release carbon monoxide. In the reduction catalytic converter 10, the nitrogen oxides are reduced with ammonia to nitrogen and water, and THC components still contained in the exhaust gas are further reduced.

[0041] The oxidation catalytic converter 9 and the reduction catalytic converter 10 are integrated into the same housing 11 of the exhaust gas treatment device 8.

[0042] The temperature of the exhaust gas exiting the oxidation catalytic converter 9 is too high for long-term impingement on the reduction catalytic converter 10. This is the case in particular in exhaust gas treatment plants, whose exhaust gas contains clay minerals, anhydrite, and large amounts of calcite, as is common in the cement industry and in processing of ores. In particular, such high temperatures of the exhaust gas entering the reduction catalytic converter 10 would result in relatively rapid deactivation of the converter. The system therefore has a cooling device for the exhaust gas to be fed into the reduction catalytic converter 10. This cooling device is configured in the form of a dosing device 12 for water which is configured integrally with a dosing device 13 for ammonium hydroxide. A mixture of ammonium hydroxide and water is therefore fed via a common injection device 14 into the exhaust gas stream. The water introduced evaporates in the exhaust gas stream and thus withdraws thermal energy from said stream, resulting in a temperature decrease of the entire exhaust gas stream, which then also comprises the evaporated water and ammonium hydroxide. In this manner, the temperature of the exhaust gas entering the reduction catalytic converter 10 is preferably limited to a maximum of 380 C.

[0043] The adapted heat exchange, which in particular is also reduced compared to the maximum heat exchange performance of the material preheater 2, from the exhaust gas to the raw cement meal to be preheated affects not only the temperature of the exhaust gas entering the exhaust gas treatment device 8, but also the temperature of the raw cement meal entering the rotary kiln 1. In particular, this temperature of the preheated raw cement meal may be relatively low, but this can be compensated for by increased fuel conversion in one of a plurality of burners (18,19) of the rotary kiln 1or if applicableof the calcinator 15 that serve as heat generating devices. In this case, the fuel conversion and thus the heat supplied to the rotary kiln 1 and present in the exhaust can be adjusted by means of a control device or regulated by means of a regulating device. The temperature of the exhaust gas entering the exhaust gas treatment device 8 can constitute a control parameter for fuel conversion. Alternatively or additionally, other parameters can also serve as control parameters, for example a gas temperature in the optionally present calcinator 15 of the system.

[0044] In the calcinator 15, precalcining of the raw cement meal already preheated in the cyclone preheater can be carried out, and the meal is then completely fired in the rotary kiln 1 to produce cement clinker. Exhaust gas withdrawn from the rotary kiln 1 (and heated cooling air from a clinker cooler 17 arranged downstream of the rotary kiln 1 (relative to the direction of flow of the cement clinker)), which are fed to the calcinator 15 via a tertiary air line 16, are used for heating and deacidification of the raw cement meal during precalcining in the calcinator. Here, separation of material precalcined in the calcinator 15 from the exhaust gas or the cooling air takes place in the cyclone of the last heat exchanger stage of the material preheater 2.

REFERENCE NUMBERS

[0045] 1 Rotary kiln [0046] 2 Material preheater [0047] 3 Raw cement meal feeder [0048] 4 First inlet [0049] 5 Second inlet [0050] 6 First heat exchanger stage [0051] 7 Control device [0052] 8 Exhaust gas treatment device [0053] 9 Oxidation catalytic converter [0054] 10 Reduction catalytic converter [0055] 11 Housing [0056] 12 Dosing device for water [0057] 13 Dosing device for ammonium hydroxide [0058] 14 Injection device [0059] 15 Calcinator [0060] 16 Tertiary air line [0061] 17 Clinker cooler [0062] 18 Burner [0063] 19 Burner