WO2018073239A1

WO2018073239A1 - Method and installation for cleaning pre-heater exhaust gases of an installation for the cement and/or mineral industry

Info

Publication number: WO2018073239A1
Application number: PCT/EP2017/076463
Authority: WO
Inventors: Anna Ivanova DINKOVA; Valentina BORDEI; Timo Stender; Björn Olaf Dr. ASSMANN
Original assignee: Thyssenkrupp Industrial Solutions Ag; Thyssenkrupp Ag
Priority date: 2016-10-17
Filing date: 2017-10-17
Publication date: 2018-04-26
Also published as: DE102016119695A1

Abstract

In the method according to the invention for cleaning pre-heater exhaust gases of an installation for the cement and/or mineral industry by reducing the concentration of gaseous pollutants, the pre-heater exhaust gases first undergo high-temperature filtration for reducing the dust content, followed by a first exhaust gas treatment by selective catalytic reduction and a subsequent second exhaust gas treatment by regenerative catalytic oxidation. The installation according to the invention for cleaning pre-heater exhaust gases (1) for the cement and mineral industry by reducing the concentration of gaseous pollutants contains a high-temperature filter (2) for reducing the dust content of the pre-heater exhaust gases, an SCR catalytic converter (3) for selective catalytic reduction of the pre-heater exhaust gases, and arranged downstream of the SCR catalytic converter a regenerative oxidation catalytic converter installation (4) for regenerative catalytic oxidation of the pre-heater exhaust gases.

Description

Process and plant for the purification of preheater exhaust gases from a plant of the cement and / or mineral industry

The invention relates to a method and a plant for the purification of preheater exhaust gases from the cement and mineral industries by reducing the concentration of gaseous pollutants.

In plants of the cement and minerals industry, inorganic materials such as cement raw meal, limestone, magnesite and dolomite are subjected to a thermal heat treatment, wherein in particular a preheater is used. In the preheater, the material to be treated is preheated by a heat exchange with exhaust gases. The exhaust gases leaving the preheater contain, in addition to a high dust content in the range of usually 50 to 120 g / Nm, a high proportion of nitrogen oxides and carbon monoxide and gaseous organic substances which according to current air pollution regulations must not be blown into the atmosphere without purifying the exhaust gases.

From DE 20 2010 018 000 Ul a device for denitrification of flue gases with at least one catalyst for the catalytic reduction of nitrogen oxides is known, wherein the exhaust gases are raised in a heat exchanger to a first temperature level. In order to achieve the still missing temperature level for the denitrification, a stage for the regenerative afterburning of the carbon monoxide is still provided, whereby additional external energy is used.

The invention has for its object to perform the reduction of the concentration of gaseous pollutants with a reduced energy demand.

According to the invention this object is solved by the features of claims 1 and 9.

In the inventive method for purifying preheater exhaust gases of a plant of the cement and / or minerals industry by reducing the concentration gaseous pollutants, the preheater exhaust gases are first subjected to a high-temperature filtration to reduce the dust content, followed by a first exhaust treatment by selective catalytic reduction and a subsequent second exhaust treatment by regenerative catalytic oxidation.

The plant according to the invention for purifying preheater exhaust gases from the cement and mineral industries by reducing the concentration of gaseous pollutants includes a high-temperature filter for reducing the dust content of the preheater exhaust gases, an SCR catalyst for selective catalytic reduction of the preheater exhaust gases and a regenerative oxidation catalytic converter arranged downstream of the SCR catalytic converter. Plant for regenerative catalytic oxidation of preheater exhaust gases.

The preheater exhaust gases in the high-temperature filtration expediently still a temperature in the range of 200 ° C and 400 ° C, preferably from 250 ° C and 350 ° C. The high-temperature filter may in particular have an electrostatic precipitator or filter cartridges. The dust content of the preheater exhaust gases before the high-temperature filtration is usually 120 to 50 g / Nm (grams per standard cubic meter) and in the high temperature filtration is preferably less than 3 g / Nm 3, preferably less than 2 g / Nm 3, most preferably less than 1 g / Nm reduced. The lower the dust load of the exhaust gas entering the SCR catalytic converter, the lower the risk of clogging due to the depositing dust. To improve the selective catalytic reduction, a reducing agent, in particular an ammonia-containing reducing agent, can be added to the exhaust gas before the SCR catalyst. The formation of the SCR catalyst takes place, for example, with vanadium as the active component. According to a particular embodiment of the invention, the high-temperature filter for dust reduction can be equipped with filter cartridges, which also form the SCR catalyst at the same time. In this case, the catalytic material can be processed directly in the base material of the filter cartridge, so that the preheater exhaust when flowing through the filter cartridge to the catalytic materials. Alternatively, however, the filter candle may also be coated with catalytic material.

For the subsequent catalytic oxidation, for example, an oxidation catalyst doped with noble metals as the active component is used. In particular, for the oxidation of methane, however, comparatively high temperatures of greater than 400 ° C are required. However, the temperatures after preheater usually do not have this temperature level. According to the invention, therefore, first the denitration in the SCR catalyst, which is preferably carried out in a temperature window of 250 ° C to 350 ° C. By using the high-temperature filtration, the preheater exhaust gases do not have to be cooled down before dedusting and then raised again to the temperature level required for denitrification.

It is therefore only appropriate for catalytic oxidation to increase the temperature of the preheater exhaust gases and indeed to a temperature range of 350 ° C to 780 ° C, preferably 400 ° C to 700 ° C, most preferably 500 ° C to 600 ° C.

The raising of the temperature of the Vorwärmerabgase takes place in particular by means of heat displacement in at least one heat storage module, wherein in the flow direction of the preheater exhaust preferably at least one upstream and a downstream heat storage module are provided. The oxidation catalyst may be formed in one or more layers and is equipped for example with precious metals as the active component.

If desired, after the regenerative catalytic oxidation, activated carbon may be added to the preheater exhaust gases for mercury removal. Furthermore, the oxygen content of the preheater exhaust gases in the first and second exhaust treatment is in the range of 2 to 10%, preferably 3 to 8%, most preferably 4 to 6%. To use residual heat still contained in the preheater exhaust gas, a heat recovery stage (for example for exhaust gas flow or water heating) can be connected to the regenerative oxidation catalytic converter system.

The SCR catalyst, the oxidation catalyst and the heat storage modules can in particular be formed with honeycomb bodies, wherein preferably all honeycomb bodies have an identical honeycomb structure. The honeycomb bodies have the advantage that they can be flowed through well and at the same time offer a large surface area for the catalytic reactions.

Further embodiments of the invention are explained in more detail below with reference to the further description and the drawing.

In the drawing show

1 is a block diagram of the system according to the invention for the purification of preheater exhaust gases,

2 shows a block diagram of a plant of the cement and mineral industry with a plant according to the invention for purifying the preheater exhaust gases with an SCR catalyst arranged downstream of the high-temperature filter,

3 shows a block diagram of a plant of the cement and minerals industry with a plant according to the invention for purifying the preheater exhaust gases with an SCR catalyst integrated in the high-temperature filter,

4 shows a schematic representation of a regenerative oxidation catalytic converter system according to a first exemplary embodiment,

Fig. 5 is a schematic representation of a regenerative oxidation catalyst system according to a second embodiment and

Fig. 6 is a schematic representation of a regenerative oxidation catalyst system according to a third embodiment. The plant for the purification of preheater exhaust gases 1 of the cement and minerals industry shown in FIG. 1 consists of a high-temperature filter 2 for reducing the dust content of the preheater exhaust gases, an SCR catalyst 3 for the selective catalytic reduction of the preheater exhaust gases and a regenerative arranged downstream of the SCR catalytic converter 3 Oxidation catalyst unit 4 for the regenerative catalytic oxidation of preheater exhaust gases.

The high-temperature filter 2 is designed in particular as an electrostatic filter or has a plurality of filter cartridges. The preheater exhaust gases 1 flow through the high-temperature filter 2 at a temperature in the range of 200 ° C to 400 ° C, preferably from 250 ° C to 350 ° C. This temperature essentially corresponds to the temperature of the preheater exhaust gases when leaving the preheater. Thus, preferably no previous active cooling takes place by air or water quenching. The dust content of the preheater exhaust gases 1 is reduced in the high-temperature filtration of usually 50 to 120 g / Nm to less than 3 g / Nm 3, preferably less than 2 g / Nm 3, most preferably less than 1 g / Nm 3. The separated dust 5 can be returned to the actual manufacturing process.

The dedusted preheater exhaust gases then flow through the SCR catalyst 2 doped, for example, with vanadium, in which case a reducing agent 6, in particular an ammonia-containing reducing agent, is added. Subsequently, a catalytic oxidation of carbon monoxide and gaseous organic pollutants takes place in the regenerative oxidation catalyst system 4. The residual heat remaining in the preheater exhaust gas after the regenerative oxidation catalytic converter system 4 can be utilized in an optional heat recovery stage 7 following the regenerative oxidation catalytic converter system 4, for example for exhaust gas power generation or water heating.

Fig. 2 shows a block diagram of a plant of the cement and minerals industry, in which the plant described above for cleaning the preheater exhaust gases is integrated. The plant comprises a preheater 8, a furnace 9 and a cooler 10, wherein the exhaust gases of the furnace 9 flow through the preheater 8 for preheating raw meal 11 and leave the preheater as preheater exhaust gases 1 at a temperature level of typically 200 ° C to 400 ° C. The reducing agent 6 required for the SCR catalyst may be added to the preheater exhaust at or immediately before the SCR catalyst. But there is also the

Possibility to introduce the reducing agent 6 at the upper end of the preheater 8.

After the optional heat recovery step s 7, the preheater exhaust gases are used in a raw material mill 12, crushed in the raw material 13 to the raw meal 11 and dried at the same time. This reduces the temperature of the

Preheater offgases at about 80 to 120 ° C. If the raw material mill is not available, the preheater exhaust gas is passed through a cooling tower 14, wherein previously activated carbon 15 can be added to reduce mercury.

The exhaust gas cooled in the raw material mill or in the cooling tower 14 is then removed from the dust 17 (+ possibly activated carbon) in a dedusting filter 16 before it reaches the atmosphere via a chimney.

3 shows a block diagram of a plant of the cement and mineral industry, which differs from the embodiment of FIG. 2 only in that the high-temperature filter and the SCR catalyst are formed by a high-temperature catalytic dedusting plant 20. The catalytic

High-temperature dedusting system 20 can be equipped to reduce dust with filter cartridges, which also form the SCR catalyst at the same time. In this case, the catalytic material can be processed directly in the base material of the filter cartridge, so that the preheater exhaust gas strikes the catalytic materials when flowing through the filter cartridge. Alternatively, however, the filter candle may also be coated with catalytic material.

4 shows a schematic representation of the regenerative oxidation catalytic converter system 4 according to a first exemplary embodiment. It has an example doped with precious metals oxidation catalyst 21, wherein in Flow direction 22 of the preheater exhaust gases 1 each have at least one upstream and a downstream heat storage module 23, 24 are provided, which may be formed in one or more layers. The preheater exhaust gases are intended to be heated by the upstream heat storage module 23 in the flow direction and that to the temperature required for the catalytic oxidation in the range of 400 ° C to 750 ° C. If the heat of the heat storage module 23 is not sufficient for this, a further heating can take place via the fuel gas feed 19. The oxidation on the oxidation catalyst 21 also releases additional heat, so that the temperature of the preheater exhaust gases after the oxidation catalyst is even higher (for example, by 200 to 250 ° C higher). As soon as the heat of the heat storage module 23 is no longer sufficient or after a predetermined time, the flow direction of the preheater exhaust gases through the regenerative oxidation catalyst system is reversed, so that the exhaust gases in the following flow through the heated heat storage module 24, before they reach the oxidation catalyst 21.

5 shows a variant of the regenerative oxidation catalytic converter system with three channels, which each have a heat exchanger module 23.1, 23.2 or 23.3 and in each case an oxidation catalytic converter 21.1, 21.2 or 21.3. About a non-illustrated flap system, the preheater exhaust gases can always flow through two of the three channels according to the principle explained for Fig. 4. The third channel should primarily prevent emission peaks arising when switching the flaps.

Finally, FIG. 6 shows a variant of FIG. 5 in which the three channels are equipped in each case with a heat exchanger module 23.1, 23.2 and 23.3, respectively, which have flaps 25.1, 25.2, 25.3, 25.4 and 25.5 with a common oxidation catalyst 21.4. are interconnectable.

Claims

claims:

1. A process for the purification of preheater exhaust gases (1) a plant of the cement and / or minerals industry by reducing the concentration of gaseous pollutants, the preheater exhaust gases are first subjected to a high-temperature filtration to reduce the dust content and then a first exhaust gas treatment by selective catalytic reduction and a subsequent second exhaust treatment by regenerative catalytic oxidation, wherein the preheater exhaust gases (1) in the high-temperature filtration have a temperature in the range of 200 ° C and 450 ° C.

2. The method according to claim 1, characterized in that the dust content of the preheater exhaust gases (1) is reduced in the high-temperature filtration to less than 3 g / Nm.

3. The method according to claim 1, characterized in that the

Preheater off-gas (1) before the selective catalytic reduction, a reducing agent is added.

4. The method according to claim 1, characterized in that the temperature of the preheater exhaust gases (1) is raised in the regenerative catalytic oxidation to a temperature range of 350 ° C to 780 ° C.

5. The method according to claim 5, characterized in that the raising of the temperature of the preheater exhaust gases (1) by means of heat displacement in at least one heat storage module (23, 24) and optionally takes place by external fuel.

6. The method according to claim 1, characterized in that the

Sauer toffgehalt the preheater exhaust gases (1) in the first and second exhaust treatment in the range of 2 to 10%.

7. The method according to claim 1, characterized in that the

Preheater offgas (1) after regenerative catalytic oxidation activated carbon (15) is added to the mercury removal process.

8. Plant for the purification of preheater exhaust gases (1) a plant of the cement and minerals industry by reducing the concentration of gaseous pollutants with

a high-temperature filter (2) for reducing the dust content of the preheater exhaust gases in the temperature range of 200 ° C and 450 ° C,

- An SCR catalyst (3) for the selective catalytic reduction of the preheater exhaust gases and

- A downstream of the SCR catalyst (3) arranged regenerative oxidation catalyst system (4) for the regenerative catalytic oxidation of the preheater exhaust gases.

9. Plant according to claim 8, characterized in that the

High temperature filter (2) has an electrostatic precipitator or filter cartridges.

10. Installation according to claim 8, characterized in that the regenerative oxidation catalyst system (4) comprises an oxidation catalyst (21) and in the flow direction of the preheater exhaust gases (1) each have at least one upstream and a downstream heat storage module (23, 24).

11. Plant according to claim 10, characterized in that the first and the second heat storage module (23, 24) are formed one or more layers.

12. Plant according to claim 8, characterized in that the regenerative oxidation catalyst system (4) heat recovery stage s (7) connects to the use of remaining in the preheater exhaust residual heat.

13. Plant according to claim 8, characterized in that the

High-temperature filter (2) for dust reduction is equipped with filter cartridges and the SCR catalyst (3) is formed by catalytic filter cartridges.

14. Plant according to claim 8, characterized in that the SCR catalyst (3), the oxidation catalyst (21) and the heat storage modules (23, 24) are formed with honeycomb bodies, wherein preferably all the honeycomb body having an identical honeycomb structure.