DE4226726A1 - Drum treating brown coal smoke gases - is located within smoke passage of brown coal-fired boiler with lime crusher and conveyor, optimising temp. and application of lime in treatment of effluent sulphurous gases - Google Patents

Abstract

The assembly to remove sulphur from a brown coal-fire water boiler uses effluent heat in a rotating drum reactor with lime milk and an additive suspension. The rotating double-walled drum (1) is located with its conveyor and crusher in the steam boiler smoke (20) gas effluent passage. The lime milk (19) injection jet (8) is centrally located in the inlet. An inlet for lime and/or abrasive substance is located in the lower section of the drum, and/or a water inlet (28) and a further lime inlet (26) in the drum upper section. A lime milk pipe enters a settling tank (13) in the lower drum section (11). The settling tank (13) is linked to a mixer vessel (10) by a pipe bearing the caustic solution (14), which supplies the injection jet group (8) via a pump (18). A solids drainage channel (15) is located in the lower drum end (11) sector. This is linked to a vessel (25) via a mill (16) and pipe (36), which charges the lime inlet (26) for the drum (1). USE/ADVANTAGE - The assembly neutralises sulphur compounds from smoke gases emitted by burning brown coal. The assembly maintains steady conditions and temperature which maximise the binding role of the lime.

Description

The invention relates to a device for desulfurization of flue gases from a lignite-fired steam boiler Use of waste heat from the boiler gases.

To achieve a high degree of integration of the Limestone additive for desulfurization of the flue gas after a furnace charged with raw lignite, e.g. B. a coal dust burner for steam boilers is a big one Limestone additive reaction area required. The means that the limestone becomes a very expensive small grain size is ground. However, it was found that the surface thus obtained reacts, but the core of the limestone additive particles still has a high reactivity, however remains unused. For this reason, the information the reactive core of the limestone additive particles following technologies applied:

• 1. return to the reaction process; extremely low Effect (DD-PS 2 15 241, 237 477);
• 2. Extension of the reaction zone; no essential Effect (DE-OS 31 28 903);
• 3. reactivate in a steam stream; little effect (DE-OS 35 26 857);
• 4. grind in a steam stream; good effect, however high effort (DD-PS 2 18 563);
• 5. grind outside of the reaction process; quality Effect, but high effort (DE-OS 33 19 791, DD-PS 2 23 364);
• 6. grind in a two-step process; quality Effect, but high effort (DE-OS 35 10 669).

Due to the high expenditure for fine grinding or re-grinding was also tried, broken Use limestone additive according to the following technologies:

• 1. Discharge of the broken limestone additive after the reaction and subsequent grinding and recycling; low improved effect and high effort (DD-PS 85 821);
• 2. Discharge of the broken limestone additive after the reaction and regeneration and repatriation; slightly improved Effect and high effort (DE-OS 33 47 468).

To ensure a high degree of integration of the limestone additive achieve, therefore, despite the high effort Fine dust grinding of the limestone additive carried out.

A washing method for cleaning is also known Exhaust gases, the first separation stage in the scrubbing circuit a classification, preferably with hydrocyclones, the Washer suspension is switched on and that Classifying coarse material together with the coarse ash and the additive is subjected to a wet grinding while the Classification fine is introduced into a second one Thin turbidity accumulates, which goes back into the washer and on Thickened product is created that drains and is removed (DE-OS 38 08 374).

The expenditure on equipment and the control are very high. There is a high material flow circulation with the corresponding Pipeline and pumping effort.

A method and a device are also known for desulfurization by burning Raw lignite generated flue gas flow, being broken Limestone additive before, in and / or after a reaction zone is introduced, and the limestone additive in the Reaction zone continuously circulated, crushed as well  sighted and in a media stream, e.g. B. flue gas or Hot air flow, thrown back as well as reaction-exhausted and reactive limestone additive Particle is discharged from the media stream (DD-PS 2 71 278). The limestone additive particles are part of the Combustion process. The reaction takes place in the Combustion chamber with the disadvantages of being incomplete Mixing, the risk of burning lime at high Flames or combustion chamber temperatures. Not completely reacted lime particles get into the Exhaust gas ash removal system.

The invention is based, for one Flue gas desulfurization process consistently good Requirements regarding the integration and To achieve temperature conditions.

This is achieved according to the invention in that the itself well-known rotatable double-walled, with transport and Crushing rings equipped and with the flue gas flow loaded drum in the exhaust duct of the steam boiler is arranged, in the region of the drum inlet centrically an injector group for milk of lime, in A limestone and / or abrasive and / or water supply and in the upper drum part further limestone inlets are arranged.

The entire drum has a chamber housing in which the heating medium flows. Inside the drum Lime milk and limestone initiated under simultaneous Addition of abrasives.

The lime milk is sprayed into the flue gas stream Limestone with abrasive and water is in the Bottom drum supplied. With the rotation of the drum a crushing of the limestone and at the same time one Dissolve into lime milk, which in turn is injected.  

At the same time, material that cannot be shredded is used Remove the end of the drum and feed it to a grinding plant.

The invention is based on a Embodiment will be explained in more detail.

In the flue duct 1 of a small boiler there is a rotatable drum 2 with the screw-like transport and size reduction rings 3 . Around the entire drum 2 there is the air housing 4 with the individual chambers 5.1 ; 5.2 ; 5.3 , the air supply duct 7 and air discharge duct 6 . In the center of the drum 2 or in front of the drum there is the injector group 8 , which is connected to the mixing container 10 via the line 9 . At the end of the drum 11 there is the lime milk line 12 with the settling tank 13 and lye line 14 and the solids discharge duct 15 with a mill 16 .

Mode of action

The flue gases 17 from the steam boiler are passed into the drum 2 . Immediately in front of the drum, lime milk 19 is simultaneously injected via the nozzle group 8 by means of the pump 18 . The lime milk is carried along with the flue gas stream 20 . Heavy solid particles 21 fall into the lower drum part 22 . Limestone 24 is also supplied from the container 25 via the transport line 26 and water (lime milk) 27 via the line 28 to the drum front part 23 . With the rotary movement 29 of the drum 2 and the size reduction and transport rings 3 , the mixture of limestone 24 , solid particles 21 and water 27 is conveyed to the end of the drum 11 . With this transport, the limestone is crushed and dissolved, whereby there is a permanent veil of lime milk 31 on the inside wall of the drum 32 . At the end of the drum 11 , the lime milk 30 obtained is fed via line 12 to a settling tank 13 , from which the "clean" lime milk 33 is fed via line 14 to the mixing tank 10 without solid particles and is injected again accordingly. Solid particles 34 enter the mill 16 via the channel 15 . The ground lime fractions 35 reach the container 25 via the line 36 and thus again pass through the dissolving and comminuting process within the drum 2 . At the same time as the desulfurization process, air (water) 37 is conducted into the air housing 4 via the air supply nozzle 7 and flows through the individual chambers 5 with simultaneous heat absorption via the drum jacket 38 .

The amount of air can cool the drum wall 32 well below the dew point, since acid corrosion by the lime milk veil 31 cannot occur. As a result of this cooling or the maximum possible air heating, the flue gases 17 can be used for maximum thermal purposes. The equipment for comminution, desulfurization and heat can be arranged in a cascade and is particularly suitable for smaller boiler systems. With the appropriate size, the flue gas stay and thus the desulfurization time are extended via flue gas guide devices 39 inside the drum. These internals 39 are also protected against acid corrosion by the lime milk veil.

List of the reference symbols used

1 exhaust duct
2 drum
3 shredding ring
4 air housings
5.1 Single chamber
5.2 Single chamber
5.3 Single chamber
6 air discharge duct
7 air supply duct
8 injector group
9 line
10 mixing containers
11 drum end
12 Lime milk line
13 settling tanks
14 lye line
15 solids discharge channel
16 mill
17 flue gas
18 pump
19 lime milk
20 flue gas flow
21 solid particles
22 lower drum part
23 front part of the drum
24 limestone
25 containers
26 Transport line
27 water (milk of lime)
28 line
29 rotary motion
30 lime milk
31 lime milk veil
32 inner drum wall
33 "clean" lime milk
34 solid particles
35 ground lime
36 line
37 air (water)
38 drum casing
39 flue gas control device

Claims (5)

1. Device for the desulfurization of flue gases from a lignite-fired steam boiler with waste heat utilization in a reactor acted upon by a limestone additive and an additive suspension, which is designed as a rotatable drum, characterized in that the known rotatable double-walled, equipped with transport and size reduction rings and the drum ( 1 ) charged with the flue gas stream ( 20 ) is arranged in the flue gas duct of the steam boiler, an injection nozzle group ( 8 ) for milk of lime ( 19 ) centrally in the area of the drum inlet, a limestone and / or abrasive and / or water supply (in the lower part of the drum) 28 ) and a further limestone supply ( 26 ) are arranged in the upper drum part. 2. Device according to claim 1, characterized in that in the lower region of the drum end ( 11 ) in a settling container ( 13 ) opening lime milk line is attached. 3. Apparatus according to claim 2, characterized in that the settling tank ( 13 ) via the drain line ( 14 ) is connected to a mixing tank ( 10 ) which feeds the injection nozzle group ( 8 ) via a pump ( 18 ). 4. The device according to claim 1, characterized in that in the lower region of the drum end ( 11 ) a solid discharge channel ( 15 ) is arranged, which is connected via a mill ( 16 ) and line ( 36 ) to the container ( 25 ) which the Limestone feed ( 26 ) for the drum ( 1 ) feeds. 5. The device according to claim 1, characterized in that the double wall of the drum ( 1 ) is designed as an air housing ( 4 ) with individual chambers ( 5 ) and air supply nozzle ( 7 ) and air discharge nozzle ( 6 ).