DD275518A1 - METHOD FOR DRYING RAW BROWN COAL AND LIMESTONE - Google Patents

Abstract

The invention relates to the grinding and simultaneous drying of lignite coal and limestone for the production of lime dust homogeneous mixed lignite dust for the firing of large steam generators under the aspect of flue gas desulfurization. The features of the invention are that the limestone is semi-dried for itself and the lime dust thus obtained in particular metered addition to the lignite coal together with the same again and thus mixed homogeneously mixed in the resulting lignite dust. Fig. 1

Description

For this 1 page drawings

Field of application of the invention

The inventive solution is in with lignite-fired steam generators of heating and thermal power plants' with the effect of him the frame flue gas desulphurisation by the Kalkadditivverfahren the limestone in the course of the mill drying the lignite simultaneously Mahlten and mix homogeneously in meal-drying lignite dust.

Characteristic of the known state of the art

According to EP patent 150501 (F23 K, 1/00), a method and an apparatus for producing a homogeneous mixture of coal dust and lime dust or dolomite dust has become known, according to which using a vertical air-flow mill with integrated classifier raw coal and limestone or dolomite stone assigned in the task area in front of the mill in the same ratio about dosing and transport equipment of the airflow mill.

In this case, the components to be jointly mated are metered into the one and the same fan mill.

The disadvantage here is that both components have different grinding behavior and that, accordingly, that component which is poorer aufmahlbar compared to the other, having a proportionately higher return from the classifier, which does not take into account that the same component - that is the lime in this case or dolomite brick has a different visual behavior from coal due to its higher specific gravity.

By the SU patent 751419 (B02 C, 13/13), it is known to blow the coarse material retained by the separator of a fan mill for re-grinding in the grinding chamber of the fan mill, so as to favor its grinding.

Object of the invention

In flue gas desulphurization by the Kalkadditivverfahren the desulfurization effect is to be improved.

Explanation of the essence of the invention

The objective is to be achieved by the technical task, according to the different grinding and viewing behavior of limestone and lignite coal to adjust the grinding conditions with respect to a finer Körnungsbandes of lime dust and improved homogeneity of lime dust and lignite dust.

The solution to the problem is that the raw lignite and the limestone are firstly separately dried and then that the resulting lime dust in the whole or a coarse fraction thereof is once more ground-dried as an additive to the lignite coal.

In a further embodiment of the solution of the problem either the separate mill drying of raw lignite and limestone in separate mills or in one and the same mill can be carried out in parallel, and it can be separated in a separate air classifier in two or more grain fractions and then the lime dust thus obtained only the coarse grain fractions are ejector-like introduced directly into the grinding room for raw lignite or in the return for coal semolina.

embodiment

The inventive method is explained below with reference to three figures on a sheet drawings.

Fig. 1 shows the grinding plant 1 with a driven by a shaft 24 beater 20 and with a co-rotating cutting disc 7 separate grinding chambers 2; 3. At the tangential outlet nozzle 4 from the grinding chamber 2, the line 5 is integrated with controller 6. In the grinding chamber 3 is a cutting disc 7 and a Einblasekegel. 8

The outlet nozzle 9 of the grinding chamber 3 opens into the separator 10. From the separator 10 is a semolina return line 11, which opens into the return suction 12 of the grinding chamber 3. In the lower part of the Rücksaugschachtes 12 a Kohleleitblech 13 is connected.

FIG. 2 shows another variant in the manner in which the line 5 with regulator 6 is incorporated into the semolina return line 11 of the classifier 10 in an ejector-like manner.

FIG. 3 shows a variant according to FIG. 1 with an increased ballast gas throughput.

The line 5 after the grinding chamber 2 with the controller 6 opens into a separation cyclone 14. The separation cyclone 14 is connected on the gas side via the line 15 with the separator 10 for coal dust. On the dust side, there is an optional connection via the line 16 into the semolina return line 11 or via a line 17 into the injection cone 8.

operation

At low Kalkstaubstrom 18, the total amount is conveyed to the grinding chamber 2 via the line 5 in the grinding chamber 3.

According to the demand, the volume control is carried out by the controller 6 (FIGS. 1 and 2). Separated from the raw lignite stream 19, the millbase of the grinding chamber 2 is passed through the outlet nozzle 4 and regulator 6 to ensure a uniform distribution of good over the Einblasekegel 8. In this way, the ground lime dust is mixed in a uniform distribution with the coal dust stream 21. With this circuit of the coupled grinding chambers 2; 3, only a partial stream of the grinding plant 1, the ground from the grinding chamber 2 teilzerkleinerte lime dust again together with the lignite dust 19 in Gesamtkörnungsband. Thus, a much finer lime dust than the outgoing coal in the lignite dust stream 21 coal dust is achieved. The mixture already takes place in the grinding chamber 3, wherein a uniform, fine and homogeneous mixture with a high reaction surface is formed.

It is also possible, according to FIG. 2, to inject the lime dust gas mixture guided in line 5 into the semolina recycling line 11 or to introduce it in an ejector manner.

The corresponding junction 22 of the semolina return line 11 in the return duct 12 secures the introduction into the grinding chamber 3, since the relatively fine lime dust is entrained with the sucked flue gas 23.

The mode of operation for higher lime dust flow 18 after the grinding chamber 2 is shown in FIG. 3.

This Kalkstaubstrom 18 is fed into a Klassierzyklon 14. The Klassierzyklon 14 is designed so that a desired graining belt with the exhaust gas flow 25 discharged from the Klassierzyklon 14 upwards and is introduced at the Sichteraustritt via the nozzle 26 in the classifier 10 for coal dust.

The segregated Kaikstaub 27 with low conveying gas can be passed via the line 17 into the grinding chamber 3 or via the line 16 in the semolina return line 11.

In this way it is ensured that a reduction in the Nachmühlentemperatur in the grinding chamber 3 is extremely low.

In particular, it is advantageous if the water content of the raw lignite is high and the post-mill temperature is power-limiting for the furnace. A two-stage grinding is performed only for a set in Klassierzyklon 14 graining belt, with the result of a reduction in wear. The Klassierzyklon 14 works without additional drives, since the pressure difference between the outlet nozzle 4 and separator 10 ensures good separation. A lock 28 after the Klassierzyklon 14 prevents uncontrolled gas transport into the grinding chamber. 3

Claims (4)

claims: 1. A process for grinding drying of lignite coal and limestone in the presence of hot inert gases, characterized in that the limestone is firstly semi-dried and that then the so-dried lime dust in the totality or a coarse fraction thereof, together with the lignite coal is once again ground-dried. 2. The method according to claim 1, characterized in that the limestone by itself and the lignite coal are ground-dried with lime dust with flue gases. 3. The method according to claim 1, characterized in that the separately ground-dried lime dust is classified in the presence of flue gases. 4. The method according to claim 1, characterized in that the separately ground-dried lime dust is combined with provided for the after-grinding coal grit or is blown directly into the grinding chamber for coal dust.