DE3008481A1 - CLEANING METHOD FOR A FILTER SYSTEM FOR DUSTY GAS WITH REDUCING PROPERTIES AND FILTER SYSTEM HERE - Google Patents

Description

Cleaning process for a filter system for dusty Gases with reducing properties and a filter system for this

The invention relates to filter systems for dust-containing gases, the chemical composition of which has reducing properties confers.

The invention relates to cleaning processes for such systems and also to the systems performing these processes.

Such dusty gases are often found in electrometallurgy Industry. According to the currently applicable standards against environmental pollution, these must contain dust Gases are filtered.

These dusty gases are therefore filtered in filter systems with one or more filter elements. These filter elements have one of the dusty gases hit

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upstream area and. a downstream area, the dust settling on the upstream surface.

Consequently, the filter element or elements must be cleaned periodically to remove those located on the upstream Surface deposited layer of dust. This process is called cleaning.

It is known that this cleaning process is well carried out by pneumatic devices generally supplied with air,

Under these conditions the mixture can become dusty Gas (which has reducing properties) and air (which has oxidizing properties) have explosive properties which represent a significant danger due to the electrostatic phenomena that are present at the moment cleaning can occur.

A cleaning process that occurs by peeling off the layer of dust (cake) that is on the upstream surface of each Filter element is deposited, generates electrostatic Charges that give rise to electrostatic phenomena that produce electrical discharges.

It has already been suggested to use the cleaning process a neutral gas (e.g. nitrogen). However, one then encounters operating cost problems.

The object of the invention is to avoid recourse to an expensive neutral gas.

The object of the invention is in detail to create a cleaning method and a filter system, their operating costs is below those of previously known systems, with the same level of security against the risk of explosion.

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The object of the invention is also to create a system at which enables the recovery of thermal energy, which is particularly important for feeding metal refining devices can then be used if it is a filter system in an electrometallurgical complex.

This object is achieved according to the invention by the subjects of claims 1 and 5-

It is preferably between the combustion chamber and the pneumatic one Cleaning device arranged a heat exchanger, the transition of thermal energy between the Yerbr burngasen and a fluid to be heated.

The invention thus cleans the system with an inert gas mixture that results from the reaction from the reducing dedusted gas and an oxidizing gas results, the inert gas mixture not being an explosive mixture can form:

- neither with the reducing, dedusted gas that is taken up by the filter system located downstream of the filter element (s),

- nor with the reducing dust-containing gas that is taken up by the filter system located upstream of the filter element or elements .

In addition, this inert gas mixture is generated at the location of the plant and in precisely the required amount.

Ultimately, the production of this inert gas mixture creates that from the combustion of the reducing dedusted gas with an oxidizing gas (which is formed by air can be) results, a thermal energy partially in the circuit traversed by the fluid to be heated is recovered.

According to a particularly advantageous application of the invention the filter system is used to absorb reducing dust

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containing gases from an annealing furnace for metals, the fed by a calcining furnace, which in turn receives:

- the reducing dedusted gas from the filter system,

- a heated oxidizing gas from a downstream of the combustion chamber located heat exchanger,

- a mineral or metal oxide melt and

- if necessary, an addition of heated oxidizing gas, which is heated in a heat recuperator, which is removed from the dusty gases before they enter the filter system is crossed.

It can thus be seen that the filter system according to the invention in an electrometallurgical complex can lead to significant energy savings.

It is now a special embodiment of the invention compared to the filter systems with several filter cells being investigated are each equipped with at least one filter element traversed by the dusty gas.

If the filter system, as stated above, has several filter cells, the cells are known to be cleaned individually, d. H. one cell is separated and the filter element or elements of that cell are cleaned while the others Cells stay active.

This particular embodiment of the invention is characterized in that before separating the filter cell and before the cleaning of the filter cell by means of the inert gas mixture coming from the combustion chamber in countercurrent is purged by the gas mixture, and that the purging is carried out under such conditions that the purge gas mixture the atmosphere of the filter cell is completely renewed without causing the loosening of the dust layer on the is deposited upstream of the filter element or elements of the filter cell surface.

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If necessary, before cleaning the filter cell, it is again placed under the same gas mixture in countercurrent Conditions flushed so that the gas mixture accompanies the falling of fragments from the dusty layer to the emptying device in the lower zone of the filter system.

To carry out this particular embodiment of the invention • contains the filter system in a manner known per se:

- several filter cells provided with at least one filter element traversed by the dusty gases,

- An inlet housing common to the filter cells, the one on the side of the surface located upstream of the filter elements arranged and with a feed with ptaubhaltigern gas connected is,

- an outlet container for each filter cell, which is arranged on the side located downstream of the filter elements,

- A collecting container common to the filter cells, which is controllable via an independent one for each filter cell Closure device is connected to each outlet container and is connected to an outlet for dedusted gases, and

- Pneumatic using the inert gas mixture from the combustion chamber Cleaning devices for cleaning the filter element or elements of each filter cell, the cleaning devices are independently controllable for each filter cell,

characterized by flush inlet devices for flushing with the inert gas mixture from the combustion chamber, the gas mixture being sent in countercurrent to each outlet container the flushing inlet devices being controllable independently for each outlet container and with an inert gas mixture be fed such that when the flush inlet devices are open, the countercurrent flow of the gas mixture a complete renewal of the atmosphere respective filter cell without causing the loosening of the dust layer on the upstream of the or the Filter elements of the filter cell located surfaces is deposited.

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It can thus be seen. That, thanks to the invention, the inert Gas mixture in the first place fills the outlet container of the respective filter cell, through the filter element or elements of this Filter cell and passes through the layer of dust deposited on the upstream of the filter element or elements without their To bring about detachment, and finally expands in the part of the filter cell that the respective filter element or elements surrounds.

You can therefore use exactly the amount of inert gas mixture, which is suitable and avoids any risk of explosion in the filter cell during cleaning so that this inert gas mixture fills the entire filter cell.

Partially separating partitions are preferably provided in the inlet container, which the filter element or elements of the filter cells - but without isolating them.

Thanks to this arrangement, the demarcation of the inert gas mixture favored around the filter element or elements of each filter cell.

The invention is described, for example, with reference to the drawing. It shows:

1 shows a schematic view of a first embodiment of a filter system according to the invention;

Fig. 2 is a schematic view of a further embodiment of the invention;

3 shows a schematic view of a further embodiment of a filter system according to the invention;

4- a detailed view of a variant of the embodiment of Fig. 3.

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Fig. 1 shows as an example a filter system for a dusty Gas from a plant, not shown, the chemical composition of which gives it reducing properties.

This gas is fed to the filter system through a line 1.

The filter system contains one or more filter elements 2 (only one of which is shown in FIG. 1). The filter element 2 has an upstream face 2a hit by the dusty gas and a downstream face 2b.

The dust is deposited on the upstream surface 2a.

In FIGS. 1 and 2 it is assumed that the filter element 2 is formed by a sleeve held by a partition 3 will.

The filter element 2 is surrounded by a housing 4 which is divided into two parts by the partition 3, namely: - in an upstream part 4a into which the dusty gases are introduced,

- In a downstream part 4b in which the dedusted gas is collected.

The dedusted gas is withdrawn from the filter system by a suitable device, such as one or more fans 5.

To carry out the cleaning of the filter element or elements 2, a cleaning process is periodically carried out for removal the layer of dust deposited on the upstream surface 2a of the filter element 2.

This cleaning process is carried out by a pneumatic device 6.

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The pneumatic cleaning device is known. Your working principle is based on the supply of a burst of gas (generally air) into the downstream part 4b of the housing 4. This gas surge creates one or more inflations of the filter element 2 from its downstream face 2b to its upstream face 2a.

According to the invention, cleaning takes place by removing the dust-free Gas at the outlet of the downstream part 4b of the housing 4, this gas is oxidized in a combustion chamber 7 and the inert gas mixture resulting from this oxidation is used to clean the filter element 2, wherein the cleaning device 6 is consequently fed by the gas mixture.

The combustion chamber 7 thus receives on the one hand (at 8) the reduced dust-free gas removed in the upper part 4 and on the other hand (at 9) oxidizing gas, which can advantageously consist of air.

A heat exchanger 10 enables thermal energy to be transferred between that through the combustion gases from the combustion chamber 7 formed inert gas mixture and a fluid circulating in a circuit 11 and to be heated.

Figure 2 shows an embodiment of the invention in a particular one found in the electrometallurgical industry Use. In FIG. 2, the same reference numerals denote the same elements as in FIG. 1.

The filter system is supposed to absorb reducing dusty gases from a tempering furnace 21 for metals, which in turn is fed by a calcining furnace 22.

The reducing, dust-free gas from the filter system is routed :

- On the one hand to the cleaning device 6 after it was previously oxidized in the combustion chamber 7 and in the heat exchanger 10

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was cooled, and

- on the other hand (at 23) to the calcining furnace 22, which also (at 24) receives a charge of mineral or metal oxides.

The calciner 22 receives (at 25) an oxidizing gas (generally air) which after cycling 11 of the heat exchanger 10 is heated.

To complete the supply of oxidizing gas to the calciner 22, the calciner receives (at 26) one Addition of oxidizing gas (air) in the external recuperator was heated, which was traversed by the dust-containing gases before they were fed to the Ifilteranlage.

A filter 28 completed by an “ultrafilter 28a is advantageously provided upstream of the cleaning device 6.

In FIGS. 3 and 4, the same reference numerals designate the same elements as in Fig. 1. Fig. 3 and 4 show a filter system having a plurality of filter cells 31a, 31b, 31c ... _t

Each filter cell 31a, 3 "Ib, 31c ... is with at least one Filter element 32 is provided, for example with a filter with a sack or bag (only one of these filter elements is shown in FIG. 3 2 visible).

The filter element 32 is traversed by a dust-containing gas in the direction shown by the arrows F.

According to the method according to the invention, before the separation the filter cell to be cleaned 3 ^ -a and before cleaning the gas mixture from the combustion chamber 7 rinses the filter cell in countercurrent in the manner shown by the arrow G. Direction and opposite to the direction shown by the arrow F through the inert gas mixture from the Combustion chamber 7 made. This rinsing takes place in countercurrent

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under such conditions that the inert purge gas mixture completely renews the atmosphere of the filter cell 31a without to cause a loosening of the dust layer on the upstream surface 32a or the filter elements 32 of the filter cell 31a is deposited.

According to a preferred embodiment, after cleaning the filter cell 31a this again in countercurrent with the same Inert gas mixture flushed under such conditions that the gas mixture the falling off fragments of the dust layer to the emptying device 33 in the lower zone of the filter system.

To carry out the process, the filter system contains:

- filter cells 31a, 31b, 31c, each of which is provided _with at least one filter element 32 traversed by a dusty gas flow,

- An inlet container common to the filter cells 31a, 31b »31c 34- »the one on the side of the upstream surface 32a of the filter elements 32 is arranged and provided with a supply 35 for dust-containing gas,

- for each filter cell 31a, 31b, 31c an outlet container 36a, 36b, 36c on the side of the downstream surface 32b (opposite to the upstream surface 32a) of the filter elements 32,

- A collecting container common to the filter cells 31a, 31b, 31c 37, which has independently controllable closure devices 38a, 3Sb, 38c with each outlet container for each filter cell 36a, 36b, 36c is in communication and is connected to an evacuation 39 for dedusted gas,

- A pneumatic cleaning device 40, which works with the inert gas mixture from the combustion chamber 7,. For the or the filter elements 32 of each filter cell 31a, 31b, 31c, the cleaning device 40 for each filter cell 31a, 31b, 31c is independently controllable, and

the emptying devices 33 in the lower zone of the inlet tank 34 ·.

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This filter system also contains inlet devices 41a, 41b, 41c for purging through the inert gas mixture the combustion chamber 7 »with the gas mixture being sent in countercurrent to each outlet container 36a, 36b, 36c. the Rinsing inlet devices 41a, 41b, 41c are independently controllable for each outlet container 36a, 36b, 36c fed with an inert gas mixture in such a way that when the flushing inlet devices 41a, 41b, 41c are open, the in Countercurrent flow of the inert gas mixture results in a complete renewal of the atmosphere of the respective filter cell 31a generated without causing the loosening of the dust layer on the upstream surface 32a of the or the filter element 32 of the filter cell 31a is deposited.

A pneumatic device fed with an inert gas mixture is used to form the pneumatic cleaning device 40 43 (an additional high pressure source in Fig. 3 or a compressor 45 driven by a motor 450 in Fig. 4) provided, which generates a throughput of inert gas mixture, the lifting and loosening of the upstream located surface 32a of the filter element 32 of the respective filter cell 31a can bring about deposited dust layer, when the pneumatic device 43 is in communication with the filter cell.

For this purpose, the pneumatic device 43 is via cleaning inlet devices 46a, 46b, 46c connected to each outlet container 36a, 36b, 36c, the purification inlet means are freely controllable for each outlet container 36a, 36b, 36c.

The system is operated in the following way.

1. The system is completely in the filtration state:

- the locking devices 38a, 38b, 38c are open,

the inlet devices 41a, 41b, 41c for purging with inert gas and also the cleaning inlet devices 46a, 46b, 46c are closed.

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2. Preparation for cleaning the filter cell 351a:

- It is on the locking device 38a for control their closing.

3- Cleaning the filter cell 31ar

- The flushing inlet device 41a of the filter housing 31a is opened for the first rinse,

the rinsing inlet device 41a is closed, while the cleaning inlet device 46a of the filter housing 31a is opened to connect the filter housing to the additional source 44 or to the compressor 45 (after commissioning of the motor 450) for loosening the cake,

the cleaning inlet device 46a is closed.

4. Remove dust from filter cell 31a:

- The emptying device 43 is put into operation, which for this purpose in the lower zone of the plant or of the inlet container is provided, with the emptying device 43 common to all or each of the filter cells can be arranged under a filter cell,

- The first rinsing of the filter cell 31a is possibly continued by reopening the flushing inlet device 41a of this filter cell.

5- Complete return of the system to the filter status:

- the rinsing inlet device 41a of the filter cell 31a is closed,

the closing device 38a of the filter cell 31a is acted upon to control its closing.

For controlling the closure devices 38a, 38b, 38c ..., the rinsing inlet devices 41a, 41b, 41c, the cleaning feed devices 46a, 46b, 46c and, in the case of FIG. 4, the motor 450 of the compressor 45, a programming device '47 can be used.

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In the Pall of Fig. 4, the compressor 45 is always powered by the engine 450 powered. There is then a reservoir 451 at the outlet of the compressor provided.

This arrangement enables the required flow rate for the actual one to be injected in a very short time Cleaning process.

At the outlet of the source for the combustion chamber 7 there can be a check valve 42a be arranged. This arrangement simplifies the operation of the system by allowing it to close of the rinsing inlet devices 41a, 41b, 41c are superfluous during the cleaning phase.

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Claims (12)

Dr. F. Zumstern sen. - Dr E. Assniann - Dr. Γ4. Koenigsberger Dipl.-Phys. R. Holzbauer - Dipl.-Mg. F. Kiingseis & ii - Dr. F. Zumstein jun. PATENTANWÄLTE 80O0 Munich 2 · Bräuhausstrasse 4 · Telephone Collective No. 225341 - Telegramme Zumpat · Telex 529979 Case PL / SH-0060 80 05 AIR IUDUSTEIE 19-21 »Avenue Dubonnet, 92401 COURBEVOIE, France Patent claims 1. Cleaning procedure for a sub-system for dusty Gases with reducing properties, characterized by the removal of dust-free gas at the outlet of the filter system, by oxidizing the gas and using the one resulting from the oxidation inert gas mixture for cleaning the filter element or elements of the filter system. 2. The method according to claim 1, characterized by transmitting the thermal energy between the combustion gases and a fluid to be heated prior to feeding the cleaning device the filter system. 3 · Method according to claim 1 or 2, applicable to a Filter system with several filter cells, which are provided with at least one filtering element that is to be cleaned Separate the filter cell and then clean the filter element (s) of this filter cell, 030038/0773 characterized in that before separating the filter cell and before carrying out its cleaning the inert gas mixture coming from the combustion chamber causes the filter cell to flow countercurrently through the gas mixture is purged, 'and that the purging is carried out under such conditions that the purge gas mixture the The atmosphere of the filter cell is completely renewed without causing the loosening of the dust layer on the is deposited upstream of the filter element or elements of the filter cell surface. 4. The method according to claim 3j, characterized in that before cleaning the filter cell, apply it again with the same gas mixture in countercurrent under such conditions is flushed that the gas mixture the falling of fragments from the dusty layer to the emptying device accompanied in the lower zone of the filter system. 5 · Filter system for dusty gases with reducing Features, with a pneumatic cleaning device for cleaning the filter element (s), characterized in that the cleaning device (6) is fed with an inert gas mixture which consists essentially of combustion gases from a combustion chamber (7), which is the outlet of the filter system withdrawn reducing dedusted gas (at 8) and oxidizing gas (at 9) receives. 6. Filter system according to claim 5 »characterized in that between the combustion chamber (7) and the pneumatic cleaning device (6) a heat exchanger (10) is arranged, which allows a transfer of thermal energy between the Combustion gases and a fluid to be heated (which circulates at 11). 7 · Filter system according to claim 5 or 6, for removing reducing dusty gases from a quenching and tempering furnace for metals fed by a calcining furnace 030038/0773 becomes, thereby. marked that the Calcining furnace (22) accommodates: - (at 23) the reducing dedusted gas from the filter system, - (at 25) a heated oxidizing gas from a heat exchangers (10) and located downstream of the combustion chamber (7) - (at 24) a batch of mineral or metal oxide. 8. Filter system according to claim 7, characterized in that the calcining furnace (at 26) has an addition of heated receives oxidizing gas, which is heated in a heat recuperator (27), from the dusty gases whose entry into the filter system is traversed. 9 · Filter system according to one of claims 5 to 8, characterized characterized in that at least one filter (28, 28a) is arranged upstream of the cleaning device. 10. Filter system according to one of claims 5 to 9 with in on known way: several filter cells provided with at least one filter element traversed by the dusty gases are. - An inlet housing common to the filter cells, the one on the side of the upstream of the filter elements Is arranged on the surface and connected to a feed with dusty gas, I- an outlet container for each filter cell, which is on the is arranged downstream of the filter element side, - a collecting container that is in common with the filter cells connected to each outlet container via a controllable closure device that is independent for each filter cell and is connected to an outlet for dedusted gases, and - using the inert gas mixture from the combustion chamber 030038/0773 pneumatic cleaning devices for cleaning the or the filter elements of each filter line, where the Cleaning devices for each filter cell can be controlled independently, gekennzei.ch.net through flush inlet devices (41a, 41b, 41c) for purging with the inert gas mixture from the combustion chamber (7), the gas mixture being sent in countercurrent to each outlet container (36a, 36b, 36c) the flushing inlet devices (41a, 41b, 41c) independently for each outlet container (36a, 36b, 36c) are controllable and fed with an inert gas mixture in such a way that when the flushing inlet devices are open are, the countercurrent flow of the gas mixture a complete renewal of the atmosphere of the respective filter cell (31a »31b» 31c) generated without the Dissolve the dust layer on the upstream of the filter element or elements (32) of the filter cell located surface (32a) is deposited. 11. Filter system according to claim 10, characterized in that the pneumatic cleaning device (40) consists of a pneumatic device (43) for generating a throughput of inert gas mixture, which is a lifting and Can cause loosening of the dust layer on the upstream of the filter elements (32) of the filter cell (31a, 31b, 31c) located surface (32a) is deposited. 12. Filter system according to claim 11, characterized in that ■ the pneumatic device (43) via cleaning feed devices (45a, 46b, 46c) is connected to each outlet container (36a, 36b, 36c), and that the cleaning supply means (45a, 46b, 46c) are freely controllable for each inlet container (36a, 36b, 36c). 030038/0773