WO2010124702A1

WO2010124702A1 - Method and apparatus for fuel treatment in a cement clinker firing process

Info

Publication number: WO2010124702A1
Application number: PCT/EP2009/003145
Authority: WO
Inventors: Johann Trenkwalder
Original assignee: Schwenk Zement Kg
Priority date: 2009-04-30
Filing date: 2009-04-30
Publication date: 2010-11-04

Abstract

The invention relates to a method for fuel treatment in a cement clinker firing process, wherein a fuel containing moisture is dried in a fuel dryer using a preferably preheated drying gas, wherein the drying gas is introduced into a clinker cooler connected downstream of a rotary tubular kiln used for the cement clinker firing process and heated to a temperature of 500ºC or more, in particular 700ºC or more, with 800ºC or more being particularly preferred. The drying gas is preheated indirectly by way of a fluid, such as a thermal oil.

Description

METHOD AND DEVICE FOR FUEL PREPARATION IN THE CEMENT LINK BURNING PROCESS

The invention relates to a process for fuel treatment in the cement clinker firing process in which a moisture-laden fuel is dried in a fuel dryer with a preferably preheated drying gas, and a device designed to carry out such processes.

The production of cements comprises, in addition to the recovery and processing of the starting materials, the firing thereof into cement clinker as well as the joint grinding of this burned clinker with gypsum and, if appropriate, other admixtures to form cement. To carry out the burning process today almost exclusively rotary kilns are used. In these plants, a multi-stage countercurrent process is operated with a rotary kiln as a central process stage. In the rotary kiln, the starting material is heated up to the partial melt in the area of the rotary kiln firing and the formation of the clinker phases is made possible by this sintering. The rotary kiln is usually preceded by a Zyklonvorwärmanlage whose construction depends on the desired Preparation of the starting material is executed. In this case, the Zyklonvorwärmanlage on the one hand the preheated raw material and on the other hand fed in countercurrent to the exhaust air from the rotary kiln. In addition, a calcination stage is arranged in newer designs between preheater and rotary kiln, in which the calcium carbonate of the preheated with Zyklonvorwärmanlage Brenngut is already largely deacidified before entering the rotary kiln. The necessary energy can be supplied to the calciner via an additional firing.

In the known combustion processes, secondary fuels of lower quality, such as sewage sludge or the like, are used in addition to high-quality fuels. These secondary fuels usually have a high moisture content and should be dried prior to combustion in order to increase the overall efficiency of the rotary kiln plant. For this purpose, fresh air is sucked in conventional drying systems and possibly preheated. After leaving the secondary fuel dryer, it often happens that the used as drying gas preheated fresh air with gaseous emissions, such as odors, organic C-compounds od. Like., Is loaded, and subjected to the elaborate filtering or treatment processes before release into the environment got to. This can also include an energy-consuming thermal afterburning of the drying gas loaded by the drying process.

In view of these problems in the prior art, the invention has for its object to provide a method for fuel processing in the cement clinker burning process available, which is easy to carry out without environmental pollution. According to the invention, this object is achieved by a development of the known method, which is characterized essentially in that the drying gas introduced into a one used for the cement clinker burning process rotary kiln clinker cooler and to a temperature of 500 ⁰ C or more, esp. 700 ⁰ C or more, more preferably 800 ⁰ C or more, is heated. Thereby, all during the drying process in the drying gas enriched gaseous emissions, such as odors, organic C-compounds od. Like., Are completely decomposed. For this purpose, at least one blower for sucking and blowing in the humidified drying gas is placed in the recuperation zone of the clinker cooler. In this region of the clinker cooler immediately following the rotary kiln, a static grate is usually mounted, in the direction of flow of the clinker the first movable grate of the clinker Clinker cooler follows. In terms of process technology, combustion air preheating for the clinker burning process is primarily carried out in this region of the grate cooler.

According to a further aspect of the invention it is provided that the drying gas cooled and moistened by the drying process before being introduced into the clinker cooler to a minimum of 10 ⁰ C, preferably at least 20 ⁰ C, more preferably 30 ⁰ C or more, above the dew point of the moistened Drying gas temperature is warmed up. By providing this according to a further aspect of the invention heating of the humidified drying gas ensures that no moisture condensed from the drying gas and this drying gas can be further treated in the rotary kiln plant, without reacting to any appreciable extent with the fired cement clinker. Further, by warming up the drying gas, the intake air temperature of the grate cooler fan increases.

The communicated to the furnace system combustion air is thus available at a higher temperature, so that the proposed in the invention to facilitate the disposal of the drying gas preheating also contributes to energy savings in the clinker burning process. As a result, the energy consumption associated with the preheating can for the most part be used profitably for the clinker burning process.

To avoid undesirable reactions with the cement clinker in the clinker cooler, the heated drying gas may be subjected to a treatment process, such as a filtering process, prior to introduction into the clinker cooler. This treatment, esp. Filtering primarily serves the dedusting and can be designed accordingly simple. A reduction of gaseous emissions, such as odors, organic C compounds od. Like. In the drying gas is not required in view of the clinker cooler caused heating of the drying gas in the course of the filtering process.

The drying gas can be supplied to the fuel dryer via a fresh air intake. In this case, the drying gas for preheating to go through one, two or more preferably arranged in the fuel dryer heat exchanger. For preheating the drying gas emitted in the clinker cooler from the fired cement clinker energy can be used profitably, if the heat exchanger with a heated by means of extracted from the clinker cooler exhaust air fluid, such as a thermal oil is charged. This fluid, in turn, can be heated in a heat exchanger charged with the cooler exhaust air.

By the described multi-stage design of the preheating of the cooler exhaust air via a first heat exchanger to the preferably executed as thermal oil fluid and then from the fluid via one or more arranged in the fuel dryer heat exchanger on the example. In the form of fresh air drying gas is a temperature stabilization with the help of the thermal oil used to preheat the drying gas, so as to effect overall process stabilization. In addition, the thermal oil can be conveyed through lines with a relatively small cross-section to the fuel dryer. To effect the heating of the thermal oil, the radiator exhaust air must be conveyed only over a relatively short distance through pipelines with a large cross-section to the heating of the thermal oil serving heat exchanger. As a result, the overall investment required for the devices used to carry out the method according to the invention is reduced.

The warming of the moistened drying gas provided according to the invention can also take place in a heat exchanger arranged downstream of the fuel dryer, wherein this warming up process can also be effected with the fluid heated with the cooler exhaust air, which is fed to the downstream heat exchanger for heating the drying gas. The cooler exhaust air taken from the clinker cooler is usually used to preheat the raw meal to be supplied to the cyclone preheating system. For this purpose, the clinker cooler can be connected via a corresponding cooler exhaust air line with a raw meal preheating.

In order to utilize the heat contained in the cooler exhaust air for preheating the drying gas, if necessary with the aid of a heat transfer fluid, a part of the cooler exhaust air can be performed in carrying out inventive method via a bypass line connected via two branch points with the cooler exhaust main line. In the context of the invention, the proportion of the outgoing air guided via the bypass line can be set to a value in the range from 10 to 100% of the total radiator exhaust air as a function of the exhaust air temperature, the exhaust air quantity and the desired flow temperature of the fluid. For this purpose are in the bypass line and / or from the bypass line bridged section of the radiator exhaust air duct arranged corresponding throttle. Additionally or alternatively, it can also be thought to introduce fresh air into the bypass line for adjusting the exhaust air temperature. In the bypass line can be arranged on the one hand with the cooler exhaust air and on the other hand serving for heating the fluid heat exchanger. It has proved to be favorable in terms of obtaining a particularly high efficiency when the fluid in the heat exchanger by at least 30 ⁰ C, preferably 40 ⁰ C or more, esp. 50 ⁰ C or more, is heated. If a thermal oil is used as the fluid, this thermal oil in the arranged in the bypass line heat exchanger from a temperature of about 120 to 140 ⁰ C, esp. About 130 ⁰ C, to a temperature of about 170 to 190 ⁰ C, esp 180 ⁰ C, to be heated. Simultaneously, the cooler exhaust air is in the heat exchanger in view of obtaining a particularly high efficiency advantageously by 50 ° C or more, esp. 80 ⁰ C or more and cooled. In this case, the cooler exhaust air from a temperature in the range of 200 to 300 ⁰ C, esp. About 250 ⁰ C, to a temperature in the range of 140 to 200 ⁰ C, esp. About 170 ⁰ C, cooled.

As can be deduced from the above explanation of inventive methods, a device suitable for carrying out a method according to the invention comprises a fuel dryer operable to dry a fuel with a preferably preheated drying gas and one for introducing the drying gas from the fuel dryer into a clinker cooler connected downstream of a rotary kiln, esp the recuperation zone of the clinker cooler, designed line arrangement. According to a further and independently claimed aspect of the invention, a device for fuel treatment in the cement clinker burning process is provided with a fuel dryer for drying the fuel with a preferably preheated drying fuel dryer, wherein the fuel dryer, a warm-up device, such as a heat exchanger is connected downstream, for warming up the by the drying process, if necessary, cooled and humidified drying gas to a temperature above the dew point of the drying gas. In the line arrangement designed for introducing the drying gas into the clinker cooler, a treatment arrangement, in particular a filter arrangement designed for cleaning the drying gas, such as a filter arrangement designed for dedusting the drying gas, can be arranged. Additionally or alternatively, the treatment arrangement may also have a condensation arrangement, so as to avoid the introduction of an excessively large amount of water in the clinker cooler. According to the invention it is provided that the drying gas in the heat exchanger downstream of the fuel dryer by a temperature of 10 ⁰ C, preferably at least 20 ⁰ C, more preferably at least 30 ° C, from a temperature in the range of 30 to 60 ⁰ C, esp. About 45 ⁰ C, to a temperature in the range from 60 to 80 ⁰ C, esp. About 70 ⁰ C _{1 is} warmed up.

In devices according to the invention, the fuel dryer may have at least one heat exchanger to which the drying gas and, on the other hand, a heated fluid, such as a thermal oil, heated with the aid of cooler exhaust air drawn from the clinker cooler, can be supplied. For heating the fluid, on the other hand, a heat exchanger which can be charged with the cooler exhaust air can be used, the further heat exchanger being expediently arranged in a bypass line to a cooler exhaust line connecting the clinker cooler with a preheating system, in particular a raw meal preheating system, connected upstream of the rotary kiln.

As already explained above, in the context of the invention it has proved particularly expedient with regard to process stabilization and the reduction of investment costs if the heating device connected downstream of the fuel dryer with a fluid heated with the aid of cooler exhaust air drawn off from the clinker cooler, such as thermal oil, is fed.

The invention will be explained with reference to the drawing, to which reference is expressly made with respect to all essential to the invention and in the description unspecified highlighted details. The sole figure of the drawing shows a schematic representation of a device according to the invention.

The device shown in the drawing comprises as a central part of a rotary kiln 10. The rotary kiln 10 is fed via a Zyklonvorwärmanlage 20 with a grinding device 22 crushed raw meal. The cement clinker fired from the raw meal in the rotary kiln 10 is cooled in a clinker cooler designated as a whole by 30. For this purpose, the clinker cooler 30 is supplied via cooling fan 32, 92 cooling air. Part of this cooling air is preheated in the clinker cooler 30 and fed via a vent line 40 to a raw meal processing device 22, such as a grinder. Another part of the cooling air is introduced from the recuperation zone of the clinker cooler as combustion air or secondary air in the rotary kiln. For processing the fuel required for the clinker burning process, a fuel dryer 60 is provided. hen. The fuel dryer 60 is designed as a belt dryer and comprises a conveyor belt 61 to which moisture-laden fuel, such as sewage sludge, is supplied. The fuel may have a moisture content of 20% or more.

For drying the fuel to a moisture content of 5% or less, the fuel dryer 60 is supplied with fresh air. This fresh air is preheated by means of one, two, three or more heat exchangers 62 arranged in the fuel dryer 60. The heat exchangers 62 are fed via a line system 52 with a fluid realized as thermal oil. This fluid is heated with a arranged in a bypass line 46 to the exhaust pipe 40 heat exchanger 50. The bypass line 46 is connected via branching points 42 and 44 with the exhaust air line 40 for the deducted from the clinker cooler 30 radiator exhaust air. It comprises two throttle valves 43 and a fan 45. For adjusting the amount of cooler exhaust air discharged through the bypass line 46, a throttle valve 48 is also provided in the section of the cooler exhaust line bridged by the bypass line 46. Further, a fresh air supply line 47 for supplying fresh air is provided in the cooler exhaust air line. Also in the Frischluftzuführleitung 47, a throttle valve 49 is arranged for adjusting the amount of fresh air. The amount of cooler exhaust discharged through the bypass line 46 may be up to 100% of the total exhaust air drawn from the clinker cooler 30 through the cooler exhaust line. The amount of diverted into the bypass line 46 radiator exhaust air can be adjusted depending on the moisture content of the fuel to be dried and the necessary heat extraction.

In the heat exchanger 50, the cooler exhaust air from a temperature in the order of 200 to 300 ⁰ C, esp. About 250 ° C, to a temperature in the range of 150 to 200 ⁰ C, esp. 170 ⁰ C, cooled. At the same time in the heat exchanger 50, the thermal oil supplied to the heat exchanger 50 via the line system 52 from a temperature in the range of 100 to 150 ⁰ C, esp. About 130 ⁰ C, to a temperature of 150 to 200 ⁰ C, esp. 180 ° C, heated. The thus preheated thermal oil is supplied to the heat exchangers 62, with which the sucked fresh air is warmed up for the purpose of fuel drying. The withdrawn from the fuel dryer 60 drying air is heated by means of another, the fuel dryer 60 downstream heat exchanger 70. It can be assumed that the drying air leaves the fuel dryer 60 with a temperature in the range of 30 to 60 ⁰ C, esp. About 45 ⁰ C, and in the heat exchanger 70 to at least 10 ⁰ C, preferably at least 20 ⁰ C, especially preferably about 25 ⁰ C, above the dew point of the humidified during the drying process air is warmed.

After leaving the heat exchanger 70, the drying air at a temperature in the range of 50 to 90 ⁰ C, esp. About 70 ⁰ C ₁ on. The thus heated drying air passes through a treatment arrangement 80, such as a filter arrangement used for dedusting the drying air and / or serving for dehumidifying the drying air condensation arrangement, and is introduced via a line system 90 and radiator fan 92 in the clinker cooler 30. In this case, the introduction of the heated drying air takes place in the region of the static grate or the grate 1, ie in the recuperation zone of the clinker cooler 30. In this area, the drying air is at a temperature of 500 ⁰ C or more, esp. 800 ⁰ C or more, heated, so as to decompose all contained in the drying air gaseous emissions such as odors, organic C-compounds od. Like. Entire. The line assembly 90 can also be supplied with fresh air via a fresh air flap 94. The introduction of the warmed-up drying air takes place in a region of the clinker cooler 30 in which, above all, combustion air preheating for the clinker burning process is to be ensured. By introducing already preheated drying exhaust air, the intake temperature of the supplied air increases. The combustion air passed to the furnace system is then available at an elevated temperature.

Claims

1. A process for fuel treatment in the cement clinker burning process in which a moisture-laden fuel in a fuel dryer (60) is dried with a preferably preheated drying gas, characterized in that the drying gas in a used for the cement clinker burning process rotary kiln (10) downstream clinker cooler (30) and heated to a temperature of 500 ⁰ C or more, esp. 700 ⁰ C or more, more preferably 800 ⁰ C or more, is heated.

2. A process for fuel treatment in the cement clinker firing process in which a moisture-laden fuel is dried in a fuel dryer (60) with a preferably preheated drying gas, esp. According to claim 1, characterized in that the cooled by the drying process and moistened drying gas, preferably before the introduction into a one used for the cement clinker burning process rotary kiln (10) downstream of the clinker cooler (30), to an at least 10 ⁰ C, preferably at least 20 ° C, more preferably 30 ⁰ C or more, which is above the dew point of the humidified drying gas temperature is warmed up.

3. The method according to claim 2, characterized in that the heated drying gas prior to introduction into the clinker cooler (30) is subjected to a treatment process, such as a filtering process.

4. The method according to any one of the preceding claims, characterized in that the drying gas for preheating at least one heat exchanger (62) passes through.

5. The method according to claim 4, characterized in that the heat exchanger (62) with a by means of from the clinker cooler (30) withdrawn radiator exhaust air heated fluid, such as a thermal oil, is charged.

6. The method according to claim 5, characterized in that the fluid is heated in a on the other hand with the cooler exhaust air fed heat exchanger (62).

7. The method according to claim 5 or 6, characterized in that the moistened drying gas is preferably heated in a fuel dryer (60) downstream heat exchanger (62) with the heated with the cooler exhaust fluid.

8. The method according to any one of claims 5 to 7, characterized in that the radiator exhaust air for heating the fluid flows through a bypass line (46) of a cooler exhaust main line.

9. The method according to any one of claims 6 to 8, characterized in that the fluid in the heat exchanger (62) by at least 30 ⁰ C _1, preferably 40 ° C or more, esp. 50 ⁰ C or more, is heated.

10. The method according to any one of claims 6 to 9, characterized in that the clinker cooler exhaust air in the heat exchanger (62) by 50 ⁰ C or more, esp. 80 ° C or more, is cooled.

11. An apparatus for carrying out a method according to one of the preceding claims, comprising a fuel dryer (60) which can be charged for drying a fuel with a preferably preheated drying gas, characterized by one for introducing the drying gas from the fuel dryer (60) into a rotary kiln (10). Downstream clinker cooler (30) designed line arrangement (90).

12. The apparatus of claim 1 1, characterized by a the fuel dryer (60) downstream and the clinker cooler (30) upstream of the heating device, such as a heat exchanger (70), for heating the cooled by the drying process and moistened drying gas.

13. The apparatus of claim 1 1 or 12, characterized in that the line arrangement (90) is assigned to a treatment, in particular filters, the drying gas designed treatment arrangement, such as a filter assembly (80).

14. The device according to one of claims 11 to 13, characterized in that the fuel dryer (60) has at least one heat exchanger (62), on the one hand, the drying gas and on the other hand with the aid of from the clinker cooler (30) withdrawn radiator exhaust air heated fluid can be supplied ,

15. The apparatus according to claim 14, characterized by a further for the heating of the fluid with the radiator exhaust air operable heat exchanger (50).

16. The apparatus according to claim 15, characterized in that the further heat exchanger (50) in a bypass line (46) to a clinker cooler (30) with an optionally a raw meal treatment plant containing exhaust air system connecting cooler exhaust line (40) is arranged.

17. Device according to one of claims 12 to 16, characterized in that the fuel dryer (60) downstream of the heating device (70) with a by means of the clinker cooler (30) withdrawn radiator exhaust air heated fluid, such as a thermal oil, is fed.

18. A device for fuel treatment in the cement clinker burning process, esp. According to one of claims 11 to 17, with a fuel for drying the fuel with a preferably preheated drying fuel dryer (60), characterized by a fuel dryer (60) downstream heating device, such as a heat exchanger (70), for heating the drying gas possibly cooled and moistened by the drying process.