DD283481A7 - METHOD AND ARRANGEMENT FOR OPERATING A CARBON FAN VALVE - Google Patents

Abstract

The invention relates to a method and an arrangement for operating a pulverized coal fan for the pulverized coal of a steam boiler. In this case, a dust-poor and / or a fine dust-rich Foerdergas mixture is separated and withdrawn from the edge region of the dusty coal dust-Foerdergas-mixture flowing centrally in the Ausstroemquerschnitt the Muehle and / or in a arranged after Ausstroemquerschnitt transition part and / or in Abstroemquerschnitt the UEberstesteiles. Fig. 2 {pulverized coal firing; Fan mill; Business; Coal dust Foerdergas mixture; feeders; visually unattractive gas}

Description

For this 8 pages drawings

Field of application of the invention

The invention relates to a method and an arrangement for operating a pulverized coal fan mill for the pulverized coal of a steam boiler.

Characteristic of the known state of the art

With increasing water and ballast content in the raw lignite coal occur serious consequences in the ignition and combustion in the pulverized coal of a steam boiler.

There are therefore a variety of solutions known to separate the resulting after the pulverized coal mill exhaust gas fine dust mixture small load and / or the exhaust gas fine dust mixture high load from the coal dust conveying gas mixture within the classifier or thereafter. The separated mixture is fed to particular uses, e.g. B. Brüdenbrenner (DD-PS 57276), Brüdengasableitung for condensation (DD-PS 243972), Brüdengaseinleitung in the combustion chamber or Nachschaltheizflächen (DD-PS 243329, DD-PS 251604, DD-PS 262147), Zündstaubgewinnung for pulverized coal pilot burner, extraction Flammable coal dust for auxiliary burner (DD-PS 209343, 229043), Brüdengas Sichterumgehung (DE-AS 122108, 1208158).

The disadvantages of these separation technologies within the classifier are that the classifier is to be designed according to the total Nachmühlengasstrom, high wear of the classifications occurs, special separation internals in the classifier are required by these internals a further pressure loss occurs, for the removal of the separated amounts of gas. Drive is necessary, the visual process is disturbed by the additional internals and a clear separation of the laden with particulate gas vapor from the coarse grain, in particular ballast shares, is not possible. Due to the Brüdengas-conveying gas-pulverized coal mixture within the classifier therefore considerable expenses for a vapor gas separation are required.

For these reasons, attempts have already been made to carry out a separation of the vapor gases within the mill (DD-PS 245 369, DD-PS 63957, 57276). By dissipating a large proportion of hot gas, dust drying within the mill is substantially reduced. In addition, increases with increasing gap width by Eckpanzerverschleiß the fine dust discharge; In addition, coarse dust is also discharged.

Object of the invention

The aim of the invention is to improve the grinding, visual or Feuerungsprozeß with little effort.

Explanation of the essence of the invention

The invention is based on the object. Conveying gas and / or dust immediately after beating wheel, utilizing the flow velocity for effective fire guidance To find and use for optimum operation of the pulverized coal fan mill.

This is achieved in that according to the invention separated from the edge region of the centrally flowing dusty pulverized coal conveying gas mixture in Ausströmquerschnitt the mill and / or arranged according to Ausströmquerschnitt transitional time and / or in Abströmquerschnitt the transition part a low-dust and / or a fine dust-rich conveying gas mixture and deducted.

To realize dusty and low-dust conveying gas channels and / or cold and / or hot gas channels are involved in the Ausströmquerschnitt the mill and / or arranged in a arranged after Ausströmquerschnitt transition part and / or in the Abströmquerschnitt the transition part.

embodiment

In embodiments, the invention is explained in detail. The drawings show:

Fig. 1: the representation of the pulverized coal conveying gas profile in Ausströmquerschnitt the pulverized coal fan mill

Fig. 2: the integration of a pilot burner delivery line in the transition part

3: the integration of delivery lines in the arranged according to flow cross-section of the mill transition part

Fig. 4: the integration of KohlestaubrHauptbrenner- and Brüdenbrenner delivery lines in the Ausströmquerschnitt the

Mill

5 shows the integration of delivery lines via suction cross sections arranged in the transition part

Fig.6: the integration of the cold gas channel in the transition part

Figure 7: the integration of the hot gas channel in the transition part and the hot gas channel in the mill housing with

Coal dust extraction plant

Fig. 8: the separation of sichtungs worthy cold and warm gas in the transition part to mill

Fig.9: the integration of the warm gas channel into the transition section

Rg. 10: the integration of the cold and warm gas channel in the transition part for training as Mehrkammersichter

11: the side view of FIG. 10.

The coal dust fan mill 2 has the Schlagradnabe 83, the incident slope 84, the striking wheel 87, the mill housing 88, the motor-side side wall 78, the mill door-side side wall 79, the spiral outer wall 82, the

Outflow cross-section 80 and arranged at the outflow cross section 80 transition part 3, which is designed as a diffuser,

Between the side surfaces of the impact wheel 87 and the side walls of the mill housing 88 and between the outer diameter of the striking wheel 87 and the spiral inner wall 86 and the spiral outer wall 82, the distance 90 is provided in each case.

The transition part 3 has the outflow cross section 81.

The mode of action is the following:

During operation of the mill 2, flue gas 27 is sucked axially by the impact wheel 87 and conveyed via the outflow cross section 80 into the transition part 3.

At the same time with the flue gas 27 coal 49 passes into the striking wheel 87, there is milled in Mühlehgehäuse 88 and 87 striking wheel and conveyed off as coal dust-conveying gas mixture 25 via the outflow 80.

Fördergaubaubprofil and dust distribution at Ausströmquerschnitt 80 is controlled by the following measures:

1. About the arrangement of the slope of the incidence 84 of the mill door and the associated influence of the discharge line 85 of the coal 49 in the region of the impact wheel 87;

2. About the formation of the Schlagradnabe 83 by controlling the mill flow 89 within the striking wheel 87;

3. About the diameter, the number of impact plates and the height of the impact plates of the impact wheel 87;

4. About the distance 90 between the side surfaces of the striking wheel 87 and the side walls 78; 79 of the mill housing 88 or between the outer diameter of the striking wheel 87 and the spiral inner wall 86 and the spiral outer wall 82nd

By the dimensioning, training and arrangement of these elements, the dust distribution and the gas flow 89 is influenced and generates a profile of coal dust conveying gas mixture 25 at Ausströmquerschnitt 80. In particular, the distance 90 influences the edge flow of the coal dust conveying gas mixture 25. For a given distance 90, the profile of the coal dust conveying gas mixture 25 is shown. The loading "b" (amount of dust / gas) is concentrated in the area of the spiral outer wall 82 and the motor-side side wall 78. The loading "b" has its minimum in the region of the Ausströmquerschnittes 80 on the spiral inner side 86 and in the area of the mill door side wall 79. Die Gasgeschwindigkeit " V "of the pulverized coal conveying gas mixture 25 has its maximum in the region of the outflow cross section 80 on the spiral inner side 86 and on the mill door side wall 79. The same applies to the temperature distribution" T "of the conveying gas.

The distribution described is influenced by the arrangement of the designed as a diffuser transition part 3 amplified. Does the transition part 3 as a diffuser a corresponding slope and corresponding diffuser length "L", then arises in the edge region segregation, which causes due to the formation of turbulence 77 diffused fine dust in the wall region of the diffuser bevel, while the coarse dust, the flow of coal dust This results in a relative concentration of ultrafine dust in the diffuser wall region over the cross section 81 at the outlet cross section 81 or outflow cross section in the region of the outlet of the transition part 3, as for example for the dust D _o , o63 (passage through the sieve with mesh size 0.063 mm) The main burner ignitor system has the mill 2 with the transition part 3 and the sifter 1 (Figure 2).

At the classifier 1, the coal dust channel 5 connects with slide 97 and the main burner 64 at. The transition part 3 has the diffusorfötmige extension, which opens via the outflow cross section 81 in the Zündstaubkanal 17 and the pilot burner 22.

The mode of action is the following:

During operation of the mill 2 and charging with coal 49 via the flue gas return duct 4, a conveying gas dust profile is formed in the region of the outflow cross section 80, which is enriched with dust in the area of the spiral outer wall 82. The pulverized coal conveying gas mixture 25 will flow predominantly into the classifier 1. Due to the diffuser-like widening of the transition part 3, a turbulence flow 77 with fine dust diffusion forms in the region of the high narrow cross-section 95 in the diffuser region. This fine dust is directed into the outflow cross section 81 formed by the diffuser. The high concentration of pulverized coal in the area of the spiral outer wall 82 is used to draw relatively large amounts of ultrafine dust into the outflow cross section 81 via the turbulence flow 77 and the diffuser formation via the flow of the gas 24 and to direct it to the pilot burner 22 via the ignition dust channel 17. The relative use of the exit velocities from the outflow cross section 80 of the mill 2 is hereby used to overcome even in the area of the pilot burner 22 even higher pressure losses due to the arrangement of spin bodies 96. These swirl bodies 96 or untwisted obstructions bring about a high pressure loss, but lead to a relatively good turbulence in the area of the pilot burner 22 and thus to an ignition-stable pulverized coal flame. The largest part of the pulverized coal conveying gas mixture 25 passes via the classifier 1 and the coal dust channel 5 to the main burner 64. The dust concentration via the flow of the gas 24 is further increased by the fact that a high narrow Absaugquerschnitt 95 is realized, which, however, by its arrangement is kept in the vicinity of the mill door side wall 79 of coarse dust. The coarse dust concentrates primarily on the engine side sidewall 78. The separate support burner operation of the support and / or pilot burner 22 (Figure 2) is done as follows: Closure of the slide 97 will greatly oversize the separator 97 with minimum coal feed in the cycle Pulverized coal conveying gas mixture 25 via the channel 17 to the ignition and / or support burner 22 when the main burner 64 is out of operation.

Of course, such a support operation via channels, which bypass the classifier 1 as bypasses, take place with closed Sichteraustritt directly on the main burner, with parts of the main burner can be additionally blocked off (Fig. 6).

The mill 2 is connected to the flue gas return duct 4 (Figure 3). The mill housing 88 receives the striking wheel 87. The mill housing 88 opens into an outflow cross section 80, this is formed by the spiral inner side 86, the mill door side wall 79, the spiral outer wall 82 and the motor side wall 78. The discharge cross section 80 opens into a transition piece 3, which is designed as a diffuser and a length "L The outflow cross section 81 is divided into the vapor suction cross section 91.1; 91 (obliquely hatched) and the sight dust cross section 92 (hatching is shown rotated by 90 °.) The sight dust cross section 92 opens into the pouring return channel 93, which is integrated into the flue gas suckback channel 4. The vapor suction cross sections 91.1; 91 open into the coal dust channel 5, 5.1, which are integrated into the main burner 64. The mode of action is the following:

If the mill 2 is in operation, flue gas 27 with coal 49 is conveyed via the flue gas return duct 4 into the mill 2 and discharged as pulverized coal conveying gas mixture 25 via the outflow cross section 80. The design of the distances 90 between the impact wheel 87 and mill housing 88 and the arrangement of the Schlagradnabe 83 and the coal inclination slope 84 are dimensioned so that forms a dust-laden and low-dust profile at Ausströmquerschnitt 80. Thus, in the area of the walls 78; 82 of Ausströmquerschnittes 80 form a dusty grobstaubströmung while in the region of the walls 79; 86 forms a low-dust mixture with high exit velocities. The arrangement of the diffuser bevels of the transition part 3 with a predetermined relatively large length "L" is achieved in that a turbulent flow 77 forms in the edge region of the flow of pulverized coal-conveying gas mixture 77, which leads to a strong diffuser side relative enrichment of particulate matter, eg D. _o , o63 ^r leads.

Due to the relatively high gas velocity in the area of the mill door-side side wall 79, a low-dust mixture will be produced there and the vapor suction cross-section 91 downstream of the diffuser can be made very large there. While the dust-rich coarse dust mixture concentrates on the motor-side side wall 78, for this reason the vapor-suction cross-section 91.1 is designed to be relatively narrow. The profile causes the Sichterstaubquerschnitt 92 preferably as a trapezoidal shape in the region of the spiral outer wall 82 wide and narrow in the spiral inner wall 86 is designed and thus a sufficient selection of coarse dust and fine dust or much gas to the main burner and little gas to the area Gießrücklaufkanales 93 is achieved.

Especially for the operation of this fan mill burner system with addition of limestone as an additive, this arrangement has an effect, because the limestone ground in the mill contains relatively heavy particles, which are coarsely thrown in the center of the scrubber cross-section 92 with high discharge rate directly into the semolina return channel 93. The same applies to the flow of coal dust conveying gas mixture 25 with coarse dust. The vapor suction cross sections 91.1; 91 are dimensioned so large that up to z. B. 80% of the conveying gas through the coal dust channels 5; Be promoted 5.1 to the main burner with enough ground dust and enough dust. The coarse particles of dust and lime, on the other hand, are thrown directly into the semolina return channel 93 and conveyed back to the mill 2 with little gas via the flue gas recirculation channel 4.

'Due to the strong profile formation over the Ausströmquerschnitt 80 and the design of the diffuser over the length' L 'is achieved that enough finely ground dust with the conveying gas is also offered without an additional sighting of the main burner 64 over the cross sections 91.1; only a low-gas' coarse dust mixture to the Grießrücklaufkanal 93 passes the Sichtdaubquerschnitt 92. If this Grießrücklaufgemisch still afflicted with too much gas, can order a little more visible installations in Grießrücklaufkanal 93 or by interposing a cyclone (Figure 3c) nor an exhaust pipe 44 optional in the Brüdenbrenner 63 or directly into the main burner 64. The additional diversion or derivation of further gas fractions with fine dust from the Grießrücklaufkanal 93 via a funnel-shaped design of Grießrücklaufeintrittes to Sichtstaubquerschnitt 92 (Figure 2 a), by Gasableitkanälen

or blind columns between semolina return channel 93 and the coal trunking channels 5; 5.1 (Fig. 2b) or by appropriate coupling of these measures.

The new system has the advantage that on the strong profile formation at Ausströmquerschnitt 80 and the gain of Feinststaubanreicherung on the diffuser of the transition part 3 such a strong separation of fine dust with gas and coarse dust is achieved with little gas that sichterlos a stable main burner operation in increasing the Mill performance can be driven and that in particular the strong wear effect of the limestone during operation of coal 49 and limestone on the design of the classifier 1 and the mill 2 does not adversely affect.

The main burner Brüüdenbrenner system has the mill 2 with flue gas suction channel 4 with cross section (shown hatched) and the outflow section 80 of the mill 2 (Figure 4b).

The Ausströmquerschnitt 80 is divided into the Brüdenabsaugequerschnitt 91, which z. B. is arranged as a triangle in the area of the mill door side wall 79 and spiral inner side 86, and the Sichterstaubquerschnitt 92. The Sichterstaubquerschnitt 92 opens into the transition part 3, to which the separator 1 is connected. Into the classifier 1, the coal dust channel 5 with the slider 97 and the main burners 64 is arranged. The Brüdenabsaugequerschnitt 91 is connected to the vapor channel 61 and the vapor burner 63.

The entire outflow cross section 80 of the mill 2 opens into the transition part 3 (Figure 4a). At the spiral inside diffuser-shaped extension of the transition part 3 is in the area of the mill door a flat Brüdenabsaugequerschnitt 91, which merges on the mill door side of the transition part 3 in a further Brüdenabsaugequerschnitt 91. At this slit-shaped lateral Brüdenabsaugequerschnitte 91 of the vapor channel 61 with a rectangular cross-section (shown hatched) is involved, which merges above the classifier 1 in a rectangular cross-section

 The mode of action is the following:

When the mill 2 (FIG. 4 b) is operated and the flue gas 27 enters the mill 2 via the flue-gas return channel 4, the coal-dust conveying gas mixture 25 is conveyed through the outflow cross-section 80, which is analogous to the dust profile "b" (FIG. 1) in FIG While dust-rich mixture with relatively low exit velocities corresponding to profile "b" and velocity "V" is present in the dust section cross section 92 (FIG. 1), this pulverized coal conveying gas mixture 25 with relative a lot of dust and relatively little conveying gas is conveyed via the transition part 3 in the classifier 1, there sighted and returned to the mill grit over the Grießrücklaufkanal 93 of the mill 2, while the coal dust-conveying gas mixture 25 through the coal dust channel 5 the main burner 64 as a dusty, The dust-poor mixture as Brü the mixture passes through the Brüdenabsaugequerschnitt 91 and the vapor channel 61 to the vapor burner 63 and relieves the gas side significantly the sifter 1, thereby increasing the ignition stability of the main burner 64 by deduction of a significant amount of conveying gas. The high exit velocities in the vapor suction section 91 are used in order to make the vapor channel 61 relatively long, so that at a location of the vapor burner 63, which is located above the main burner 64, the low-dust vapor mixtures injected there do not disturb the ignition of the main burner.

The additional pressure gain is used by the high exit velocities in the cross section 91 (Figure 4d) to direct the vapor mixture in a separator 35, to divert the separated particulate matter via a line 39 and z. B. a dust finger of the main burner 64zuzuute, while the exhaust gas is passed through the vapor burner 63 or an opening in the combustion chamber or in the Nachschaltheizflächen the boiler. However, it is also possible to reintroduce the vapor channel 61 into the main burner 64 or into the pulverized coal channel 5 (FIG. 4c) and thereby to produce a pulverized coal conveying gas mixture 25. This results in the advantage that a considerable amount of gas has been carried away over the cross section 91 and has bypassed the classifier 1 as a bypass. Thus, the classifier 1 can be relieved of conveying gas dust side and a lower pressure build-up in the classifier 1 will be required. This leads to an increase in the conveying gas dust throughput of the mill 2, without the temperature drops to mill 2.

By lateral extraction of the vapor mixture from the cross section 91, the further separation of dust and gas is promoted (Fig.4a). Due to the deflection of the gas, a selection can additionally be achieved here, so that the vapor channel 61 is relieved of further fine dust particles. This is achieved in particular by the fact that the Brüdenabsaugequerschnitt is arranged in the region of the diffuser-side slope and in the area of the mill door diffuser wall as a low, but wide slot, so that a forming during overflow turbulence quickly breaks off again and the dust particles of the Umlenkströmung can not follow.

When the slide 97 is closed, the conveying gas volume and the coal feed for the mill 2 are severely restricted and the majority of the grinding material of the mill 2 is repeatedly circulated via the semolina return passage 93 and thus very finely ground (FIG. 4f).

Fine-ground highly concentrated pulverized coal conveying gas mixture 25 with excellent ignition behavior is blown on the vapor burner 63 via the vapor channel 61 and vapor burner 63. This can be ignited with oil burners or other ignition devices in the cold combustion chamber and used to start the steam boiler or used as a flame-retardant support flame for partial load, holding mode and peak load. Of course, the separator 35 can be switched as Sichterbypaß (Fig.4e).

In this solution, the vapor channel 61 is passed completely into the separator 35 and its exhaust gases discharged into the pulverized coal pipe 5 or in the burner 64. Thus, the separator is operated by the pressure gain of the vapor line 61 against the pressure loss of the main flow over classifier 1.

In this case, the separated in the separator 35 fine dust can optionally bunkered for starting and supports or passed directly via Zündstaubleitungen to a support or pilot burner and burned to ignition stable. But it is also possible to initiate the exhaust gases of the separator in a Nachschaltheizfläche in the combustion chamber or in the flue gas duct until before induced draft.

The mill 2 has the transition part 3 and the following separator 1 (FIG. 5). The vapor channel 61 is arranged over the high narrow Absaugequerschnitt 95 as Brüdenabsaugequerschnitt 91. The channel 21 is integrated via the Brüdenabsaugequerschnitt 91 with the low wide Absaugequerschnitt 94.

The mode of action is the following:

If the mill 2 is charged with a flue gas stream via the flue gas return duct 4 and with coal 49, the flow formed by the coal dust conveying gas mixture 25 is formed at the outflow cross section 80 of the mill 2.

About the Brüdenkanal 61 low-dust, but gas-rich mixture should be sucked. This is achieved by the arrangement of a Brüdenabsaugequerschnittes 91 in the low-dust flow on the spiral inner wall 86 and the mill door side wall 79 by arranging a narrow, relatively high Absaugequerschnittes 95. Thus, a relatively large Absaugequerschnitt is realized in the low-dust mixture. Although the very high arrangement of the cross section over the turbulence flow 77 with fine dust diffusion relatively much fine dust passes into the vapor channel 61, this will not come through the arrangement of the Absaugequerschnittes in the field of low-dust flow.

If, on the other hand, vapor gas in the region of the gas-rich mixture flow is to be sucked out of the area of the spiral outer wall 82 or the motor-side side wall 78, then this vapor suction cross-section 91 must be designed as a low, wide suction cross-section 94. Here, despite the same cross-section 91 relatively low-dust mixture can be sucked because the turbulence flow 77 is formed only above the flow path and due to the small height of the cross section, this fine dust diffusion in the cross section 94 does not come into play. For this reason, a relatively low-dust mixture of the flow of the gas 24 will follow in the channel 21.

The Absaugequerschnitt is high as a narrow cross-section 95 or lower cross-section 94 in the region of the transition part 3 for dimensioning the Feinststaubanteiles or the total dust content of the over the flow of the gas 13; 24 sucked conveyor dust gas mixtures arranged.

The solutions provide the following benefits:

1. The high outlet energies and speeds at the mill outlet in conjunction with little dust are used to exclude low-dust gas components from the sighting and to relieve the sifter.

2. The system requires less pressure loss and thus increases mill performance.

3. The sifter can be made smaller, the wear in the sifter sinks, and the separation efficiency of the sifter increases.

4. It can be driven without being seen.

5. Without additional separation units, such. As cyclones, the classification of a pilot burner with dust accumulation is possible.

6. Wear-intensive sealing measures in the mill housing between the impact wheel and mill housing can be omitted. Elaborate fitting work of the coal incidence slope or the mill hub to equalize the dust profile over the discharge cross section can be omitted.

7. The mill can additionally be operated with limestone.

8. Brüdenbrennerkanäle and Zündstaubbrennkananäle and the bypass channels of the classifier can be arranged on existing systems without much effort.

The classifier 1 and the pulverized coal mill 2 are connected to one another via the transition part 3 (FIG. 6).

In the suction side of the mill 2 of the flue gas return duct 4 is integrated. The classifier 1 has the pulverized coal channel 5. In

the transition part 3 are above the openings 8; 9 the cold or hot gas channels 6; 7 involved, by the side parts 6.1; 7.1 and the wall parts 1.1; 1.2 of the classifier 1 are formed. The cold or. Hot gas channels 6; 7 are over the openings 10; 11 incorporated into the coal dust channel 5.

Optionally, via the opening 9 of the vapor channel 61 with vapor burner 63 additionally or instead of 7 integrated.

In the cold or hot gas channels 6; 7, the adjustable flaps 26 are arranged, the drive 30 are connected to the acted upon by the temperature measuring 29 controller 28.

The integration of the hot gas channel 33 into the transition part 3 (FIG. 7) takes place via the hood 16 and the opening 14 arranged in the outlet region 12 of the mill 2. The integration of the cold gas channel 6 into the transition part 3 (FIG. 8) adjoins the exit region 12 of the mill 2 arranged deflector 19 at.

The mode of action is the following:

Immediately from the transition part 3 after Mühlenaustritt 12 of the amount of total gas 23 is a weak with dust

laden amount of cold or hot gas 24.1; 24 via the openings 20; 8th; 9 and cold or hot gas channels 6; 7 dissipated.

Of the total gas 23, the weakly laden with dust hot gas 13 via the hood 16, opening 14 and hot gas duct 33 is discharged (Figure 7, 8). This gas 13; 24; 24.1 has only a very small proportion of coarse dust.

Due to the sampling point, this dust partial gas quantity is no longer required. With the supply of this amount of gas 13; 24; 24.1 in the pulverized coal conveying gas mixture 25 by classifier 1 or optionally in the vapor burner 63, the classifier 1 is relieved by this amount of gas (Fig. 6).

The pressure difference across the classifier 1 determines the extracted or outside of the classifier 1 in the short-circuited gases 13; 24; 24.1. The discharged gases 24.1 are increased by the dynamic flow pressure.

This reduced amount of gas in the separator 1 in turn causes a minimization of the pressure loss in the separator 1, whereby the gas quantities 13; 24; 24.1 be reduced. In the device without flaps 26 in the channels 6; 7; 33, a balance between cold and hot gas 24; 24.1 and pressure loss on the classifier 1 a. With the reduction of the sifter flow, the impact air fraction is increased and thus the proportion of fine dust after sifter 1 is increased without further installations.

Due to the lower amount of separator gas, the wear is reduced. With the classification of the slide or flaps 26 in the channels 6; 7; 33 can thus be controlled as a result of the change in pressure losses to mill 2, the amount of flue gases 27 via the flue gas return duct 4 in limits, without making costly interventions or installations in the flue gas return. It is also possible to adjust the temperature 29 to mill 2 via a controller 28 by changing the position of the flaps 26 to the predetermined target value. The wear on the channels 6; 7; 33 or flaps 26 is low, since the dust load contains mainly particulate matter with a low content of SiO ₂ .

To maintain the gas dynamics in the mill-classifier system, there is a minimum area ratio between the channels 6; 7; 33.

and area of Mahlkammeraustritts.

This achieves the following advantages:

1. Reduction of wear in the classifier.

2. Increasing the amount of fine dust by classifier through better reflection conditions.

3. Increase the Nachmühlentemperatur by increasing the intake hot gas quantity.

4. Little effort in the realization.

5. Simple control or operation.

6. No additional drives required.

7. Increase in mill output.

8. Subsequent installation possible on existing systems.

9. Reduction of the classifier by reducing the amount of gas in the classifier.

At the Mühlensaugseite 15 (Figure 9) is integrated into the transition part 3 via the opening 14 of the hot gas duct 7. In Mahlkammerseitenwandbereich 18 of the mill 2, the opening 32 is provided immediately after the Schlagradleisten 31, offset from the opening 14, in which the hot gas channel 33 is integrated with flap 26. The hot gas channel 33 is combined with the hot gas channel 7 and forms the drying channel 34. The drying channel 34 is integrated into the separator 35, which is connected via the lock 36 with the bunker 37. The trigger 38 of the bunker 37 is connected via the line 39 to the other combustion chamber 40 of the boiler arranged burner 41. The exhaust air line 42 of the separator 35 is integrated either via the line 43 into the mill 2 or via the exhaust pipe 44 and vapor burner 45 in the combustion chamber 40. The mode of action is the following:

From the mill 2 4 flue gas 27 is sucked in from the combustion chamber 40 via the flue gas return duct 4 and passes with the coal 49 to be ground in the mill 2. About the opening 14 of the transition part 3 from the pulverized coal conveying gas mixture 25 warm gas 13 with particulate 46th aspirated. Due to the mill load is discharged by the distribution of the coal 49 on the Mühlensaugseite 15 a small but fine ground amount of dust. In addition, passes through the opening 32 hot gas 47 in the hot gas channel 33 and in the hot gas channel 7. The amount of hot gas 47 is controlled by the flap 26 so that the corresponding Staubauftrockungsgrad is achieved, so that the fine dust 46 dries on the drying channel 34 sufficiently passes the separator 35. The exhaust gas 48 passes either via the line 43 back into the mill 2 or via the line 44 and the vapor burner 45 in the combustion chamber 40. In the transition part 3 (Figure 10) are on the openings 8; 9 of the partial chamber acting cold gas duct 6 and the hot gas duct 7 incorporated and form with the separator 1 the multi-chamber separator (Fig. 10; 11). In the openings 8; 9 are the adjustment flaps 50; 51 arranged. Within the channels 6; 7 are the adjustable viewing elements 52; 53 arranged. The sifter 1 has the semolina return funnel 54 and the semolina return passage 55. The channels 6; 7 also have the other semolina recycling funnels 56 and the semolina return channel 57

 The mode of action is the following:

In the mill 2 reach the flue gas 27 and the coal 49th

The Nachmühlengas 58 as coal dust-flue gas-vapor mixture is passed into the transition part 3. About the controllable adjustment flaps 50; 51 is immediately after mill 2 a low-dust gas-dust mixture 13; 24.1 deflected and acting in the part chamber view channels 6; 7 dissipated. The adjustment flaps 50; 51 are dimensioned so that they form an extension of the sifter intermediate wall in the vertical position and are centrally located at the end to the slope of the transition part 3. In the closed position are the adjustment flaps 50; 51 on the slopes of the transition part 3 and thus close the flow cross-section to the cold or hot gas ducts 6; 7th

In maximum open position, the adjustment flaps 50 extend; 51 to the vertical of the outlet cross-section 80 of the mill 2. About the so adjustable flaps 50; 51 is at the respective mill side, the hot gas 13 and cold gas 24.1 in the channels 7; 6 steered. According to the desired degree of dust, the classifier elements 52; 53 regulated. The separated coarse grain 59 of the channels 6; 7 passes over the semolina recycling funnels and channels 56; 57 in the semolina recycling funnel 54 of the classifier 1. With the partial gas part chamber direction the Nachmühlengas 58 is divided so that a large proportion of gas from z. B. 40% of the amount of visible gas as partial gas 13; 24.1 into the channels 6; 7 flows. The residual gas with a lot of dust, z. B. 80% of the total dust load, flows through the classifier 1, which is provided according to the high dust load with reinforced Sichteinbauten.

The separated semolina 59 from the channels 6; 7 is passed via Grießrückführkanal 57 directly into the flue gas return duct 4 or in the Grießrückführtrichter 54 or Grießrückführkanal 55.

With this arrangement, the partial separation of gas in a multi-chamber separator, the pressure loss over the classifier 1 is substantially reduced, the semolina short gas flow is very low through the returns in the classifier 1. This achieves the following advantages:

1. Reduction of the pressure loss of the grinding plant.

2. Small classifier training.

3. Core screening with high dust load, improved grinding fineness.

4. According to intended use individually adjustable chamber views.

5. Subsequent installation at low cost.

6. Increase of the raw lignite throughput also with increasing ash content of the raw lignite coal.

7. Treatment of low calorific value fuels.

Of course, all variants described are arbitrarily coupled together, so that in particular the separate deduction of low-dust conveying gas with much or little fine dust for Sichterumgehung, for the operation of ignition and support burner, Brüdenbrennern to increase the performance of the fan mill and its wear reduction, but also for separate Feinstauberzeugung, bunkering and storage can be used.

For the reduction in wear in the mill system, the disconnection and connection of low-dust conveying gas channels in the edge area of the flow cross-section of the mill or transition part can be used.

Thus, by switching off the conveying gas channel 6 (FIG. 6) and connecting the conveying gas channel 7, the conveying gas, but in particular the dust loading at the outflow cross section, is directed in the direction of the flue gas suction side or spiral inside

and thus increase in this area, the mill wear and a wear relief of the mill on the motor side and / or spiral outside occur.

Thus, a further reduction in wear and increase in service life of the mill can be achieved.

By adding marginal conveying gas channels occurring by leaks between the impact wheel and housing dust-free gas content can be used directly, so that expensive sealing measures can be omitted.

As a further advantageous new effect is relieved by the additional extraction of fine dust with conveying gas via additional delivery lines immediately after the spiral exit of the classifier and the semolina return of particulate matter.

This decisively improves the reflection, impact and grinding conditions in the classifier or in the mill.

Thus, the condition is given that the mill produces more fine grain without additional pressure loss.

The wear in the mill is decisively reduced.

By reducing the Grießrücklaufmengen or fine grain fractions of the mill is relatively humid semolina dust supplied for further drying. This increases the drying effect, and in addition a lower permissible temperature according to classifier for mill operation can be permitted.

Claims (33)

1. A method for operating a pulverized coal fan mill, characterized in that from the edge region of the centrally flowing dusty pulverized coal conveying gas mixture in Ausströmquerschnitt the mill and / or arranged in a Ausströmquerschnitt transition part and / or in Abströmquerschnitt the transition part, a low-dust and / or a fine dust-rich conveying gas mixture is separated and withdrawn. 2. The method according to claim 1, characterized in that generated by mill on a diffuser-type pulverized coal conveying gas mixture flow in the edge region turbulence fields or turbulence flows with ultrafine dust and withdrawn separately. 3. The method according to claim 1 and 2, characterized in that the coal dust conveying gas mixture additives, in particular limestone, are added. 4. The method according to claim 1 to 3, characterized in that the pulverized coal mill in addition to the coal ground or unground additives are allocated. 5. The method according to claim 1 to 4, characterized in that the outflow of the mill and / or the cross section of the transition part and / or the Ausströmquerschnitt the transition part are divided into separate visible and visually impaired areas and derived as separate conveying gas mixture flows. 6. The method according to claim 1 to 5, characterized in that a viscous conveying gas-dust mixture via sifter and / or cyclone and / or directly to the mill is fed again. 7. The method according to claim 1 to 6, characterized in that the conveying gas mixture is diverted from the transition part on the drive side of the mill. 8. The method according to claim 1 to 7, characterized in that the conveying gas mixture is diverted from the transition part on the suction side of the mill. 9. The method according to claim 1 to 8, characterized in that the conveying gas mixture is diverted controlled. 10. The method according to claim 1 to 9, characterized in that the conveying gas mixture is diverted flap-controlled. 11. The method according to claim 1 to 10, characterized in that in the conveying gas mixture, a part of the pulverized coal of the pulverized coal conveying gas mixture is diverted. 12. The method according to claim 1 to 11, characterized in that the conveyed off conveying gas mixture, a hot gas is added controlled. 13. The method according to claim 1 to 12, characterized in that a hot gas is diverted from the mill housing in the region of the corner armor of the mill. 14. Arrangement for operating a pulverized coal fan mill, characterized in that dusty and / or low-dust conveying gas channels are integrated into the outflow cross section of the mill and / or into a transition section arranged after Ausströmquerschnitt transition part and / or in the Abströmquerschnitt of the transition part. 15. Arrangement according to claim 14, characterized in that the channels are integrated via openings in the wall region of the transition part. 16. Arrangement according to claim 14 to 15, characterized in that the openings are arranged on the outer side and / or the motor side and / or rauchgasrücksaugseitig and / or spiral inside. 17. Arrangement according to claim 14 to 16, characterized in that the openings are formed as longitudinal and / or transverse slots. 18. Arrangement according to claim 14 to 17, characterized in that the channels are connected to main and / or vapor and / or support burners. 19. Arrangement according to claim 14 to 18, characterized in that the Ausströmquerschnitt by mill and / or the flow cross section of the transition part and / or the outflow of the transition part divided into separate outflow channels for pulverized coal conveying gas mixture and / or fine dust and / or low-dust gas is. 20. The arrangement according to claim 14 to 19, characterized in that after Sichtstaubquerschnitt visibly a semolina return with or without further Sichteinbauten, z. As cyclone, blinds, branch channels and / or channel constrictions, is arranged. 21. Arrangement according to claim 14 to 20, characterized in that the channels are incorporated in separators and / or cyclones. 22. Arrangement according to claim 14 to 21, characterized in that the mill is associated with an additional metering device for aggregates, in particular limestone, dry dust or filter dust. 23. Arrangement according to claim 14 to 22, characterized in that the transition part is formed diffuser-like. 24. Arrangement according to claim 14 to 23, characterized in that the channels are integrated on the suction side of the mill in the transition part. 25. Arrangement according to claim 14 to 24, characterized in that the channels are integrated via adjustable flaps in the transition part. 26. Arrangement according to claim 14 to 25, characterized in that viewing elements are arranged in the channels. 27. Arrangement according to claim 14 to 26, characterized in that the channels and the classifier are designed as multi-chamber view. 28. Arrangement according to claim 14 to 27, characterized in that the channels are integrated at an angle of 10 to 15 ° in the transition part. 29. Arrangement according to claim 14 to 28, characterized in that in the conveying gas duct, a hot gas duct is integrated. 30. Arrangement according to claim 14 to 29, characterized in that the hot gas duct is integrated via an adjusting flap in the region of the corner armor in the mill. 31. Arrangement according to claim 14 to 30, characterized in that a separator is connected as a bypass to the separator. 32. Arrangement according to claim 31, characterized in that the exhaust pipe of the separator is incorporated into the combustion chamber, in the Nachschaltheizflächenkanäle, the flue gas ducts to induced draft and / or in the suction side of the mill. 33. Arrangement according to claim 31, characterized in that the separator is connected to a bunker and / or support and / or Zündbrennerverbunden.