AT523972A1 - Process for cleaning flue gases from cement clinker production, and process and device for producing cement clinker - Google Patents

Abstract

The invention relates to a method for cleaning flue gases from cement clinker production, with the steps: heating the flue gases to a reaction temperature of a catalyst (19, 20; 28, 29), in particular a denitrification catalyst and/or an oxidation catalyst, cleaning, in particular converting nitrogen compounds and /or oxidizing gaseous hydrocarbons and/or carbon monoxide and/or ammonia from the flue gases heated to the reaction temperature with the catalyst, recovering heat from the cleaned flue gases, compensating for losses during heat recovery from the cleaned flue gases, introducing a gas flow from cement clinker production into the Flue gases before cleaning with the catalyst, so that the losses in recovering the heat of the cleaned flue gases are at least partially, preferably essentially completely, compensated. The invention also relates to a method and a device for producing cement clinker.

Description

The invention relates to a method for cleaning flue gases from cement clinker production, with the steps:

Heating the flue gases to a reaction temperature of a catalyst, in particular a denitrification catalyst and/or an oxidation catalyst,

Purification, in particular conversion of nitrogen compounds and/or oxidation of gaseous hydrocarbons and/or carbon monoxide and/or ammonia, of the flue gases heated to the reaction temperature with the catalyst,

recovering heat from the cleaned flue gases, and

Compensating for losses in recovering the heat of the

cleaned flue gases.

The invention also relates to a method for the production of

cement clinker.

Finally, the invention relates to a device for producing cement clinker comprising:

a kiln for burning raw materials into cement clinker,

a preheating stage for preheating the raw materials with flue gases from the furnace,

a clinker cooler for cooling the cement clinker,

a cleaning stage with a catalyst for cleaning the flue gases, in particular a denitrification stage with a denitrification catalyst for denitrifying the flue gases, with a heat exchanger for heating the flue gases before cleaning the flue gases, with heat recovery for recovering heat from the cleaned flue gases and with an equalization stage at least partial compensation of losses in the return

recover the heat of the cleaned flue gases.

In the production of cement clinker, the raw materials required for the formation of cement clinker are heated in rotary kilns to temperatures of 1350°C to 1700°C. The raw materials are usually preheated in a preheating tower consisting of several cyclones arranged one behind the other before they reach the rotary kiln. The flue gases flow through the pro-

production process in countercurrent to the material flow.

frequently accompanied by losses.

In the cleaning system of US 2009/130011 A1, therefore, burners are provided in the head space, with which the losses are

be equalized.

In the process of AT 507 773, on the other hand, the losses of the heat displacement of the heat exchange are compensated by regenerative thermal post-combustion of the carbon monoxide and the gaseous organic substances in the exhaust gases. Combustion temperatures in the range of approx. 750°C to 900°C are provided for in regenerative thermal post-combustion. With this method, the energy consumption for heating the flue gases could advantageously be significantly reduced. The disadvantage, however, is that the procedure is sensitive. So

In particular, the carbon monoxide or organic content must be checked

Compounds in the flue gases are sufficient to compensate for heat transfer losses and such

to enable autothermal operation of the system.

DE 10 2014 106387 describes a further development of this method, in which the reaction temperature range of the catalyst is maintained by heating and/or cooling the flue gases, the heating and/or cooling of the flue gases being used for this purpose

Air or flue gases can be introduced into the flue gases.

A cement clinker plant is also known from EP 2 545 337 B1, in which cooled flue gas is fed to an SCR plant for catalytic denitrification. For this, it must be heated to at least 230°C-270°C. It is therefore first fed to a recuperator, to which denitrified flue gas exiting the SCR system is fed in countercurrent, so that heat is transferred from the denitrified flue gas (clean gas) to the flue gas to be denitrified (raw gas). The flue gas that is to be denitrified and exits the recuperator is fed to another heat exchanger in order to heat it up further. The heat required to heat the flue gas is supplied to this heat exchanger via a thermal oil as a heat transfer fluid, which has been heated in another heat exchanger with the heat generated in the furnace during the combustion process, for example by the heated coolant for the clinker cooler. Thus, in this prior art, a heat transfer is achieved via a heat transfer fluid. However, this version works with higher energy

energy losses. In addition, the expenditure on equipment is high.

Against this background, the object of the present invention consists in eliminating or alleviating at least individual disadvantages of the prior art. Accordingly, the invention aims in particular to keep the energy requirement for the cleaning stage of the cement clinker plant as low as possible, but to reduce influences on the process to a minimum.

ren.

This task is accomplished by a method with the steps of

Claim 1, a method for producing cement clinker comprising the steps of claim 9 and an apparatus having the features of claim 10 solved. Preferred embodiments are

specified in the dependent claims.

Accordingly, the following process step is carried out in the process according to the invention:

Introduction of a gas stream of cement clinker production in the flue gases, so that the losses in recovering the heat of the cleaned flue gases at least partially, preferably in

Essentially fully balanced.

The device according to the invention for the production of cement clinker is characterized in that the equalization stage has a device for introducing a gas stream of the cement clinker production

position with a temperature in the flue gases.

According to the invention, the losses in heat transfer from the cleaned flue gases (clean gas) to the flue gases to be cleaned (raw gas) are at least partially compensated for by heating the flue gases with a gas flow produced during cement clinker production. When introduced into the flue gases, the gas flow has a temperature of 200 to 800 degrees Celsius (°C), in particular 250 to 450°C, which is higher than the reaction temperature of the catalyst. By mixing the gas stream with the flue gases, the temperature of the flue gases is increased to such an extent that the losses in recovering the heat from the cleaned flue gases are at least partially, but preferably essentially completely, compensated. The heat input via the gas stream is therefore regulated in the method in such a way that the heat recovery losses are at least partially, preferably essentially completely, compensated. If the heat recovery losses are fully compensated, an autothermal operation of the cleaning stage can be carried out, in which preferably no fossil fuel-fired burner for supplying energy to the cleaning stage is required

is used.

In order not to overload the catalytic converter, it is beneficial if the gas flow is filtered with a hot gas filter before it is introduced into the flue gases. Since the gas stream can be at a high temperature to compensate for the heat displacement losses, a hot gas filter is preferably used. If the filter is designed as a hot gas filter, the exhaust gases with a temperature of more than 265 degrees Celsius (°C), in particular more than 300°C, can be filtered. The hot gas filter can be a cyclone, an electrostatic precipitator or a filtering separator with a ceramic or metal filter medium. In a filtering separator, solids are separated on the filter medium, such as ceramic or metal, and cleaned and discharged if necessary. With this design, the exhaust gases do not need to be cooled before they are filtered. A ceramic filter is preferably used as the hot gas filter. For example, as

Ceramic silicon carbide can be provided.

Depending on the design, the catalyst can be a catalyst material selected from titanium dioxide, vanadium pentoxide, tungsten dioxide or

have a mixture thereof.

In a first embodiment, the exhaust air of a clinker cooler is used as the gas flow of the cement clinker production, the exhaust air being removed via a first connecting line from the

clinker cooler is removed.

In a second embodiment variant, a part is used as the gas flow

the waste gases from cement clinker production, in particular the waste gases from a kiln bypass, are used, with part of the waste gases from cement clinker production being conveyed via a second connecting line, in particular

particularly from the furnace bypass.

In a preferred embodiment, the flue gases are conveyed in alternating directions through a first duct having a first heat storage module for heating the flue gases to the reaction temperature of the catalyst and having a first catalyst, a connecting space, in particular a head space, and a

second channel with a second catalyst and with a

passed second heat storage module. The first and second channels are preferably arranged essentially parallel to one another. Furthermore, it is favorable if the connection space is designed as a head space, which is arranged at an angle different from 0 and 180 degrees, in particular essentially at a right angle, to the first and second channel. As a result, the raw gas inlet and the clean gas outlet are arranged in close proximity to each other. Preferably, the first and second channels are substantially vertical and the headspace is substantially horizontal. Depending on the design, a third, in particular a fourth and a fifth, duct can also be provided, which connects to the first and the second duct via the connecting space

connected is.

In this embodiment, the first and second heat storage module are designed as regenerators. The flue gases flow through the first and second ducts and the connecting space between them in alternating directions. Depending on the design, a ceramic material can be provided as the heat storage mass of the regenerators. In a first operating position, the first heat storage module is used to heat up the flue gases before the first catalytic converter and the second heat storage module is used to recover the heat from the cleaned flue gases after the second catalytic converter. The directional information refers to the flow direction of the flue gases. By switching the direction of flow, the functions of the regenerators are swapped. In a second operating position, the second heat storage module is therefore used to heat up the flue gases upstream of the second catalytic converter and the first heat storage module is used to recover the heat from the cleaned flue gases downstream of the first catalytic converter. Therewith

a quasi-continuous operation can be made possible.

In this embodiment, it is advantageous if the gas flow from the production of cement clinker is introduced into the connecting space between the first and the second channel. In this way, the heat displacement losses are compensated for in a targeted manner in the connecting space between the first and second ducts. In order to

can the favorable temperature profile in the cleaning stage

be respected. In the first operating position, in which the flue gases are fed into the first duct and discharged from the second duct, the gas flow is preferably introduced only into a section of the connecting space adjoining the first duct, but not into a section of the connecting space adjoining the second duct . Advantageously, a longer mixing section can be achieved in this way. If the direction of flow of the flue gases is reversed in the second operating position, the gas flow can only flow into the section of the connecting space adjoining the second duct, but not into the section of the connecting space adjoining the first duct

be introduced.

The connection space is preferably free of a burner for

Burning fossil fuels, such as natural gas.

The gas stream is preferably introduced into the flue gases via an injection grid. The injection grid preferably extends over the entire cross section of the headspace. Depending on the version

the injection grid can be arranged essentially vertically.

The purification process in the embodiment variants described above can be part of a process for the production of cement clinker. Thus, the process for producing cement clinker has at least the following steps:

burning of raw material to cement clinker in a kiln, in particular in a rotary kiln,

Purification of flue gases produced in the furnace with a

drive according to one of the variants described above.

The invention is explained below with reference to the drawings

illustrated embodiments further explained.

Fig. 1 shows a cement clinker plant according to the invention with a cleaning stage for cleaning the flue gases, in which the losses in recovering the heat of the cleaned flue gases by introducing clinker cooler exhaust air into a headspace of the

Cleaning level to be compensated.

be initiated.

Fig. 3 shows an embodiment variant of the cleaning stage, in which one denitrification catalyst per channel of the cleaning

level is provided.

Fig. 4 shows a further embodiment of the cleaning stage, in which one oxidation catalyst per channel

the cleaning stage is provided.

Fig. 5 shows a further variant in which in each channel of the cleaning stage a denitrification and an oxida

tion catalyst are provided.

In Fig. 1, a plant 1 for the production of cement clinker from raw material in the form of raw meal is shown schematically. The plant 1 has a (rotary kiln) furnace 2 . The rotary kiln 2 is connected to a clinker cooler 3 on the one hand and to a preheating stage 4 on the other hand. The preheating stage 4 has several cyclones 5 with which the raw material is preheated. For this purpose, the raw material is fed into the uppermost cyclone 5 of the preheating stage 2 via a material feed. The preheated raw material enters the rotary kiln 2, in which the raw material for the production of cement clinker is burned. The kiln exhaust gases or flue gases produced during combustion are conducted through the preheating stage 4 against the flow of the raw material. Furthermore, the system 1 can have a calciner (not shown). After the preheating stage 4, the flue gases can be fed via a riser 6 ("downcomer duct") into a raw mill 7, in which the raw material can be ground and dried with the help of the flue gases. The resulting raw meal can be fed to a silo, which is connected to the material feed for the preheating stage. Alternatively, after preheating stage 4, the flue gases can be

device 8, such as an evaporative cooler, cooled

will. The flue gases are then dedusted in a furnace filter 9 . Filter dust separated in the furnace filter 9 can be fed into the silo. Clinker is discharged from the rotary kiln 2 and is cooled in the clinker cooler 3 in particular with air. Part of the air flow leaves the cooler 3 as exhaust air.

As can also be seen from FIG. 1, the plant 1 also has a bypass line 10, with which a part of the flue gas emerging from the rotary kiln 2 is diverted, bypassing the preheating stage 4. The bypass gas is fed into a bypass filter 11, with which the bypass gases are dedusted. In this way, in particular, chlorides bound to the dust

be removed.

As can be seen from FIG. 1, a cleaning stage 12 for cleaning the flue gases between the dedusting in the furnace filter 9 and the release to the environment via a chimney 13 is also provided. The cleaning stage 12 in the variant of FIG. 1 can be seen in detail in FIG. Accordingly, the cleaning stage 12 in the embodiment shown has a first channel 14, a second channel 15 and a head space 16 between the first channel 14 and the second channel 15. However, at least one further channel can also be provided. In the embodiment shown, the head space 16 is arranged substantially at right angles to the first channel 14 and the second channel 15 . A first heat storage module 17 is arranged in the first channel 14 and a second heat storage module 18 is arranged in the second channel 15 . In addition, a first catalytic converter 19 is arranged in the first channel 14 and a second catalytic converter 20 is arranged in the second channel 15 . The cleaning stage 12 also has valves 21 with which the direction of flow through the cleaning stage 12 can be reversed. In the operating position shown, the flue gases A are fed to the first channel 14 and, after cleaning, are discharged from the second channel 15 . By switching the valves 21, the flue gases A can first be supplied to the second channel 15 and, after cleaning, be discharged from the first channel 14. Thus the smoke

gases A cleaning stage 12 in alternating directions, where

the first 17 and second heat storage module 18 as regenerators

are trained.

The following explanations relate to the operating position shown, in which the first heat storage module 17 is designed as a heat exchanger 22 for heating the flue gases before cleaning the flue gases and the second heat storage module 18 is designed as a heat recovery unit 23 for recovering heat from the cleaned flue gases. However, another embodiment of the cleaning stage 12 can also be provided, in which the heat exchanger 22 and the heat recovery 23 are formed by a recuperator, for example by a plate heat exchanger, in which the cleaned flue gas heats up to the to be cleaned

emits smoke.

In addition, a compensation stage 24 is provided to compensate for the losses that are unavoidable when recovering the heat from the cleaned flue gases. The equalizing stage 24 has a device 25 for introducing a gas stream from cement clinker production at a temperature above the reaction temperature of the catalysts 19, 20 into the flue gases within the head space 16 between the first 14 and the second 15 channel. The device 25 is preferably designed as an injection grid, which preferably extends over the entire cross section of the

Headspace 16 extends.

Before the gas stream is introduced into the head space 16 , the gas stream is dedusted with the aid of a hot gas filter 26 . In particular, a ceramic filter can be used as the hot gas filter 26

the.

In the variant of FIG. 1, the exhaust air from the clinker cooler 3 is used as the gas flow, the exhaust air having a first

Connecting line 27a is deducted from the clinker cooler 3. In the variant of FIG. 2, part of the exhaust gases from the furnace by-

passes 10 for compensation of heat displacement losses in

cleaning level 12 is used. To this end, the part

of the exhaust gases from cement clinker production via a second connection

tion line 27b deducted from the furnace bypass 10.

Cleaning stage 12 can be used for different cleaning tasks

are used.

In the variant of FIG. 3, the catalytic converters 19, 20 are designed as denitrification catalytic converters 28 in order to carry out an SCR (“Selective Catalytic Reduction”) for converting nitrogen oxides NOx into harmless compounds before they are released via the chimney 13. As usual, a reducing agent such as ammonia, urea and/or ammonium can be introduced into the flue gases upstream of the SCR catalytic converter (seen in flow direction).

the.

In the variant of FIG. 4, the catalysts 19, 20 as

Oxidation catalysts 29 formed.

In the variant of FIG. 5 are both denitrification catalysts

28 and oxidation catalysts 29 are provided.

Claims (10)

Patent Claims: 1. Process for cleaning flue gases from cement clinker production, with the steps: Heating the flue gases to a reaction temperature of a catalytic converter (19, 20; 28, 29), in particular a denitrification catalytic converter and/or an oxidation catalytic converter, Purification, in particular conversion of nitrogen compounds and/or oxidation of gaseous hydrocarbons and/or carbon monoxide and/or ammonia, of the flue gases heated to the reaction temperature with the catalyst, heat recovery from cleaned flue gases, compensating for losses when recovering heat from cleaned flue gases, marked by Introduction of a gas stream of cement clinker production in the flue gases, so that the losses in recovering the heat of the cleaned flue gases at least partially, preferably in Essentially fully balanced. 2. The method according to claim 1, characterized by: filtering the gas flow with a hot gas filter (26) before Introducing the gas flow into the flue gases. 3. The method according to claim 2, characterized in that as Hot gas filter (26) a ceramic filter is used. 4. The method according to any one of claims 1 to 3, characterized in that the exhaust air of a clinker cooler (3) is used as the gas flow of the cement clinker production, the exhaust air via a first connecting line (27a) from the clinker cooler (3) is subtracted. 5. The method according to any one of claims 1 to 3, characterized in that a part of the exhaust gases from the cement clinker production, in particular the exhaust gases of a kiln bypass (10), are used as the gas flow, the part of the exhaust gases from the cement clinker production via a second connecting line (27b), in particular from the furnace bypass. 6. The method according to any one of claims 1 to 5, characterized in that the gas stream of cement clinker production an injection grid is introduced into the flue gases. 7. The method according to any one of claims 1 to 6, characterized by Conducting the flue gases in alternating directions through a first duct (14) with a first heat storage module (17) for heating the flue gases and with a first catalytic converter (19), a connecting space, in particular a head space (16), and a second duct (15) with a second catalyst (20) and with a second heat storage module (18). 8. The method according to claim 7, characterized in that the gas stream of the cement clinker production in the connecting space (16) between the first (14) and the second channel (15) fed is directed. 9. A method for producing cement clinker with the steps: burning raw material into cement clinker in a kiln, cleaning of the kiln (2) resulting flue gases with a A method according to any one of claims 1 to 8. 10. Device for the production of cement clinker, comprising: a kiln (2) for burning raw materials into cement clinker, a preheating stage (4) for preheating the raw materials with flue gases from the furnace, a clinker cooler (3) for cooling the cement clinker, a cleaning stage (12) with a catalyst (18, 19) for cleaning the flue gases, in particular a denitrification stage with a denitrification catalyst (28) for denitrifying the flue gases, with a heat exchanger (22) for heating the flue gases before cleaning the flue gases, with a Heat recovery (23) for Heat recovery of the cleaned flue gases and with a Compensation stage (24) for at least partially compensating for losses when recovering the heat from the cleaned flue gases, characterized in that the equalizing stage (24) has a device (25) for introducing a gas flow from cement clinker production into the flue gases having.