WO2002009853A1 - Method and device for cleaning installations designed to remove nitrogen and fitted with catalysts - Google Patents

Abstract

The invention relates to a method and device for cleaning installations, preferably DENOX reactors in cement works, glass works, metallurgy plants, power plants and cement garbage incineration plants, which are designed to remove nitrogen and are fitted with catalysts. The aim of the invention is to provide a dust blower which dispenses with the disadvantages of prior art, has a robust design, and requires little maintenance and investment. The invention is characterized in that the cleaning is carried out by means of one or several dust blowers, provided with rakes (3) radiating upwards or downwards while the DENOX reactor (17) is in operation with hot and/or cold compressed air in an alternating or constant direction of flow of cleaning gases. In order to carry out the inventive method, one or several dust blowers are fitted with double rake constructions (10) having nozzles (11) which blow in an opposite direction. The double rake constructions (10) are coupled to each other by means of two T-shaped connecting frames (12) and have a reversing valve (4) arranged in between the double rake constructions (10) in a compressed air feed pipe (16).

Description

 METHOD AND DEVICE FOR CLEANING STICKING EQUIPMENT EQUIPPED WITH CATALYSTS

The invention relates to a method and an apparatus for cleaning denitrification plants equipped with catalysts, preferably DENOX reactors, in cement, glass, metallurgy, power plant and waste incineration plants.

In various thermal systems, it is known to remove caking and / or dust deposits using so-called soot blowers. These sootblowers work with compressed air or steam as the blowing medium and have a one-sided rake construction with nozzles.

To reduce the consumption of blowing medium and to reduce the erosion on heating surfaces when operating a soot blower with a lance-shaped blowing tube with nozzles for the discharge of blowing medium supplied under pressure, it is known that the nozzles are combined to form a nozzle group with a nozzle length and are arranged along the blowpipe with an axial distance corresponding to the group length or a multiple thereof (DE 196 47 868).

Also known is a guide bearing for an axially and rotatable sootblower tube (DE 196 03 614).

In addition, a waste heat boiler with a pipe wall bushing for a soot blower lance is described, in which the elongated hole of the soot blower box is sealed by a sliding plate attached to the lance (DE 195 33 908).

A method and a device for controlling sootblowers is known, wherein the sootblowers are activated at intervals for a cleaning process and a cleaning medium, in particular a gas, water vapor or water, against the components to be cleaned with a predetermined cleaning intensity per unit area of the surfaces to be cleaned Eject one or more nozzles each (DE 195 02 104).

The cleaning intensity per unit area is set individually for each cleaning process and for each soot blower or each group of soot blowers by the speed of movement and / or the pressure of the cleaning medium and / or the repetition frequency depending on the observed cleaning effect in current and / or in previous cleaning processes are regulated.

The cleaning effect is observed in each cleaning process on the basis of significant measured values, and the respective cleaning parameters are adapted in accordance with the measured cleaning effect in the current cleaning process and / or in later cleaning processes.

A method and a device for operating a boiler system with sootblowers is known, the heat exchanger surfaces of the boiler being freed of deposits at intervals by individual or group-activatable sootblowers (DE 195 02 097). A regular cleaning process is carried out in such a way that not the maximum possible cleaning of the heat exchanger surfaces, but rather a weaker cleaning while leaving residual deposits, at least in some areas of the heat exchanger surfaces to be cleaned, in that, during regular cleaning processes, a maximum pressure below that required for complete cleaning ( P _m ax.) Pressure (p) and / or a process speed (v) above the minimum speed required for complete cleaning (v _m i _π .) And / or a repetition frequency below the maximum repetition frequency (n _max .) ( n) is used.

All known sootblowers have in common that only one-sided cleaning of impurities is possible either upwards or downwards. If the blower is switched off or if it goes out of operation due to an unscheduled pressure drop, it returns to its initial state. When restarting, the blower starts from the starting point and repaints partially cleaned surfaces.

The one-sided arithmetic training of existing wind instruments causes that

- more blowers have to be installed in the system,

- more drives are required,

- the measurement and control engineering effort increases,

- an increased space requirement is required for the blowers in the plant, - increased operating and investment costs are incurred and it is difficult or impossible to respond to changing flow directions in the reactor. The invention has for its object to develop a dust blower that eliminates the disadvantages of the prior art in a robust and low-maintenance design with a low investment.

This is achieved according to the invention in that the cleaning is carried out by means of one or more dust blowers, each with rakes radiating upwards and / or downwards, during operation of the DENOX reactor with hot and / or cold compressed air with changing or constant flow direction of the gases to be cleaned ,

In systems with changing flow directions in the reactor, the blowing direction is changed by a changeover valve. The cleaning is carried out continuously or pulsating. The blower can be operated with cold or hot compressed air. Operation with hot compressed air has the advantage that a considerable saving in the amount of compressed air to be made available can take place, since hot compressed air takes up a larger volume than would be the case with cold air.

In an advantageous manner, the cold compressed air in the existing reactor is heated in countercurrent by the gases to be cleaned. The cleaning can be carried out upwards, downwards or in both directions. To protect against any escaping reactor gases, the dust blower is acted upon with sealing air in the area through which the reactor wall is passed, the action being effected either from a separate fan or from the existing compressed air network. The charging from a separate fan is more economical due to its mostly higher pressure level.

When the dust blower comes to a standstill, it is supplied with purge air for nozzle cleaning.

In an acidic environment of the exhaust gases to be cleaned, it is advantageous to heat the sealing and / or purge air in order to avoid or reduce corrosion on the fan.

The double rake construction is arranged at a variable distance from the surface of the catalysts (top and bottom edge).

The fan's purge and purge air inlets are connected to each other via a line. If the compressed air level in the feed line of the blower drops below a predetermined level, the blower would be operated uneconomically, so that operation only above this level makes economic sense. In the event of a drop below the level, the blower is switched off and remains at the given point until activation occurs when the predetermined level is reached. This avoids unnecessary teaching and double trips of the wind player.

It is possible to add compressed air either during the forward or backward movement of the fan in the reactor.

The device for cleaning removal devices equipped with catalytic converters, preferably DENOX reactors, as a blower loaded with compressed air, which has a drive, a suspension designed as a roller construction and rake with nozzles, is characterized in that one or more dust blowers with one or Several double rake structures, which have nozzles with opposite blowing directions, are equipped, the double rake structures being coupled to one another via two T-shaped connecting frames and having a switchover valve between the double rake structures in a compressed air supply line. The changeover valve located at the end of the compressed air supply line has a mechanical design without a separate seal with two cylindrical outlets and a continuous push rod equipped with a valve sealing washer, which optionally closes the outlets. Arranged downstream of the changeover valve is a bypass line symmetrically formed around the push rod, which connects the changeover valve to a row of rakes of the double rake construction.

An output of the changeover valve is connected to the upper and an output to the lower row of calculations.

In order to protect the nozzles of the double rake construction from contamination, it remains in its starting position between a plurality of protective covers, preferably of an angular design.

The nozzles have outlets with a convergent and divergent cut (oval) which are designed with different diameters. The diameter is chosen larger with increasing distance to the catalyst surface and smaller with decreasing distance. The dust blower according to the invention has the following advantages:

1. For the first time, simultaneous or mutual cleaning of upper and lower soiled surfaces is possible thanks to the double rake construction.

2. The dust blower can easily adapt its blowing effect to changing gas flow directions in the system.

3. Fewer blowers are needed for the same cleaning effect.

4. This means that fewer drives and measuring and control technology are required.

5. The operating and investment costs are significantly reduced by less used blowers and the changed driving and cleaning regime.

6. The use of hot compressed air heated in your own system considerably reduces the amount of compressed air required.

7. In addition, signs of corrosion of the parts of the dust blower that reach into the system are reduced to a minimum.

8. The special pressure-dependent control of the dust blower leads to a continuous progress of the cleaning process with high efficiency.

9. This dust blower is very variably adaptable to a large number of application areas, such as cement, glass, metallurgy, power plant and waste incineration plants.

The invention will be explained in more detail below using an exemplary embodiment. It shows:

Fig. 1 - the entire dust blower fitted into the system wall on average

Fig. 2 - the double rake construction in a spatial view Fig. 3 - the double rake construction in longitudinal section

Fig. 4 - the double rake construction in cross section

The wall of the DENOX reactor 17 has openings for a dust blower, which has a drive 1, a central tube 2, computing arms 3, a changeover valve 4 and roller holders 5. The sealing air supply 6 is arranged in the area of the wall box 7. The purge air enters the blower via the purge air valve 6 arranged in the area of the drive 1. The double rake construction 10 has two T-shaped connecting frames 12 for the rakes arranged in pairs, in which the nozzles 11 are located.

The push rod 14 is guided through the changeover valve 4 and has stops on both sides and protrudes from the changeover valve 4. The push rod 14 is designed to be movable in the horizontal direction and has a valve sealing disk connected to it via a web, which is in each case via one of the two cylindrical ones when the double rake construction 10 moves forwards or backwards and the push rod 14 hits the wall of the DENOX system Push outputs 13 of changeover valve 4 so that they can be optionally closed.

If the valve sealing disc is between the two cylindrical outputs 13 of the changeover valve 4, both double rake structures 10 are pressurized with compressed air.

The overall task of the dust blower system is to use compressed air to clean the honeycomb catalysts of a DENOX reactor through which flue gases from a cement rotary kiln flow.

The compressed air is generated by a compressor system and stored in a boiler. If necessary, the compressed air flows from there via a heat exchanger arranged in the DENOX reactor into the blowing medium line 16 and from there via the central tube 2 into the changeover valve 4. From this the compressed air passes via the cylindrical outlets 13 and the symmetrical bypass line 15 and / or Connection line 18 into the computing arms 3 with the nozzles 11. The differential pressure measurement across the reactor (inlet - outlet) serves as an indicator of the direction of flow and thus the procedure of the dust blower system.

If flow through the DENOX reactor 17 from top to bottom, only the two computing arms 3 are supplied with blowing medium via the changeover valve 4, ^• blow the direction of the flue gas flow.

If the flow through the DENOX reactor 17 is from bottom to top, only the other two computing arms 3 are supplied with blowing medium. This mode of operation makes it possible to economically clean the DENOX reactor 17.

Since the predominant flow direction will be from top to bottom, the computing arms 3 have been equipped with nozzles 11 of different sizes. The computing arms 3 with nozzles 11 pointing downward have a diameter of preferably 4 mm, with nozzles pointing upwards a diameter of preferably 6.3 mm.

Furthermore, the pressure transducer in the blowing medium line 16 enables the blowing process to be interrupted when the blowing pressure falls below a preset value by closing an electropneumatic ball valve and switching off the dust blower drive 1. When the set blowing pressure is reached again, the electro-pneumatic ball valve opens and the dust blower drive 1 continues to operate. When the end position is reached (blowing path ended), the electropneumatic ball valve is closed and the dust blower drive 1 moves into its end position without spraying blowing medium, if it has not yet reached it due to the driving style.

When the end position is reached, the mechanical blow valve 8 of the dust blower drive 1 is closed.

In the rest position of the dust blower, the raking arms 3, which are directed against the direction of the flue gas, are subjected to rinsing air via the purging air valve 6 in order to prevent dust from entering the raking arms 3.

The wall boxes 7 of the dust blowers are supplied with sealing air 9 from the same line in order to prevent smoke gases from escaping in the wall passage of the DENOX reactor 17 in the event of a fault. The dust blower drives 1 are fastened to the reactor wall by means of a rope pulley system. The difference in elongation between the dust blower and the blowing medium line 16 is compensated for by the use of flexible steel hoses. List of the reference symbols used

1 drive

2 central tube 3 rake arm

4 changeover valve

5 roll holder

6 purge air valve

7 wall box 8 blow valve

9 Air purge

10 double rake construction

11 nozzle

12 T-shaped connection frame 13 cylindrical outlet

14 push rod

15 symmetrical bypass

16 bals medium / compressed air line

17 DENOX reactor 18 Connection line

Claims

claims 1. Process for cleaning denitrification plants equipped with catalysts, preferably DENOX reactors, by means of a blower operated with compressed air and having rakes with nozzles, characterized in that the cleaning by means of one or more dust blowers, each with upward and / or below radiating rake (3) is carried out during operation of the DENOX reactor (17) with hot and / or cold compressed air with changing or constant flow direction of the gases to be cleaned. 2. The method according to claim 1, characterized in that with changing flow directions, a change in the blowing direction is realized by a Umschaltven- valve (4). 3. The method according to claim 1 and 2, characterized in that the cleaning is carried out continuously or pulsating. 4. The method according to claim 1 to 3, characterized in that heating of cold compressed air in the DENOX reactor (17) is realized in countercurrent to the gases to be cleaned. 5. The method according to claim 1, characterized in that the dust blower is acted upon by sealing air (9). 6. The method according to claim 5, characterized in that the application of sealing air (9) is carried out from a separate fan. 7. The method according to claim 5, characterized in that the dust blower from the existing compressed air network with sealing air (9) is applied. 8. The method according to claim 1 to 4, characterized in that the dust blower is acted upon at a standstill with purge air (6) for nozzle cleaning. 9. The method according to claim 1, 4, 5 and 8, characterized in that the barrier (9) and / or purge (6) exposure to the exhaust gases to be cleaned in the DENOX reactor (17) is realized by heated compressed air. 10. The method according to claim 1, characterized in that the computing arms (3) to the surface of the catalysts (upper and lower edge) are arranged at a variable distance. 11. The method according to claim 1 to 10, characterized in that the blower is activated from a predetermined compressed air level. 12. The method according to claim 1 to 11, characterized in that the blower is stopped when the compressed air drops below a predetermined level. 13. The method according to claim 1 to 12, characterized in that the blower continues to operate when the old compressed air level is reached again without additional training trip at the old location. 14. The method according to claim 1 to 13, characterized in that the compressed air addition is carried out only with a forward or backward movement of the fan. 15. Device for cleaning removal devices equipped with catalytic converters, preferably DENOX reactors, by means of a compressed air-operated and rake with nozzles, as well as a drive and a blower designed as a roller construction, characterized in that one or more dust blowers with one or more Double rake structures (10) which have nozzles (11) with opposite blowing directions are equipped, the double rake structures (10) being coupled to one another via two T-shaped connecting frames (12) and between the double rake structures (10) in a compressed air supply line (16) have a changeover valve (4). 16. The apparatus according to claim 15, characterized in that the changeover valve (4) is provided in a mechanical design without a separate seal with two cylindrical outputs (13) and a continuous push rod (14) formed with a valve sealing disc. 17. The apparatus of claim 15 and 16, characterized in that after the changeover valve (4) is arranged around the push rod (14) symmetrically formed bypass line (15). 18. The apparatus according to claim 15 to 17, characterized in that an output of the switch valve (4) is connected to the upper and an output of the switch valve to the lower row of calculations. 19. The apparatus according to claim 15 to 18, characterized in that the double rake structure (10) remains in its starting position between several, preferably angularly formed, protective covers. 20. The apparatus according to claim 18 to 19, characterized in that the nozzles (11) of the double rake construction (10) are designed with convergent and divergent outlet (Laval). 21. The apparatus according to claim 15 and 20, characterized in that the nozzles (11) are formed with different diameters. 22. The apparatus of claim 15, 20 and 21, characterized in that the diameter of the nozzles (11), depending on their distance from the catalyst surface, is larger or smaller. 4 pages of drawings