DE4402773A1 - Flue gas desulphurisation in power station fired with lignite dust - Google Patents

Abstract

Process for operating a flue gas desulphurisation unit for a power station fired with lignite dust is claimed, in which a lime-water suspension is produced and introduced into the S-contg. flue gas via a gas scrubber and sulphate-enriched water is produced. The process comprises quenching and diluting quicklime with the circulating sulphate-enriched water to form a suspension, which is fed to the bottom of the gas scrubber.

Description

The invention relates to a method for operating a Flue gas desulfurization system for a brown coal dust mine fired power plant.

For the flue gas desulfurization of a lignite dust erten power plant is z. B. a limestone-water suspension sion and a flue gas scrubber sulfurization plant in the SO₂-containing flue gases introduced (wet process).

For the preparation of the suspension, this is the case with Desulfurization produces sulfate-enriched water in one Circulation process used (e.g. DE 37 14 092).

The advantage is that with one satisfactory level of desulfurization sulfate-enriched water is reused and thus the Water balance of the flue gas desulfurization plant is not being affected.

The disadvantage, however, is that a high one Limestone requirements as well as a high expenditure for transport and Warehousing is required.

A reduction in the effort can be achieved in that the preparation of the quicklime suspension is used, because of a much improved reactivity as well as cheap Stoichiometry occurs during the desulfurization process.

However, the use of quicklime requires that the Quicklime is extinguished with fresh water (low sulfate water) must become. (G. Pohl: "On the influence of SO₄ ions in Extinguishing white lime ", ZKG 8 (1955), p. 393).

The use of fresh water for the production of this However, suspension requires an additional water requirement in addition to the need for rinsing processes at Flue gas desulfurization (droplet separator, gypsum wash).

As a result, the maximum possible amount of fresh water in the Circulation exceeded or there would have to be an additional one Amount of circulating water to be disposed of, so that a total the effort is increased again.  

However, if the sulfate-enriched water is used to extinguish the If quicklime is used, grit will occur. Out for this reason, water with a sulfate content greater than 300 mg / l classified as unsuitable for extinguishing quicklime (U. Wittneben: "Investigations of the particle own of suspended lime hydrates ", ZKG, 10 (1980) p. 26).

The invention has for its object a largely wastewater-free technology of flue gas desulfurization and Reduction of expenditure on absorbents and water to reach.

Through a large number of long-term attempts surprisingly found that quicklime used with the circulated sulphate-enriched water deleted and diluted to suspension and in itself introduced in a known manner in the bottom of the scrubber becomes.

This ensures that when deleting the Quicklime with the sulfate-enriched water Grief occurs, but the reactivity of the sun prepared suspension is surprisingly given. The reactivity of the suspension so produced is comparable to one made with low sulfate water Suspension.

The invention will be explained in more detail using an exemplary embodiment explained. The accompanying drawing shows that System diagram for the flue gas desulfurization of a lignite-dust-fired power plant.

The flue gas desulfurization system has the gas scrubber 1 with flushing water line 2 , flue gas duct 3 , clean gas duct 4 and the gas scrubber suspension line 11 and the oxidation air line 12 .

The gas scrubber 1 is connected via line 5 to the complex of quicklime extinguishing system, suspension receiver and metering device 6 , via line 7 to the hydrocyclone 8 and via line 9 to the circulating water tank 10 . The quicklime slaking system, suspension receiver and metering device 6 are connected via the conveyor system 13 to the storage container 14 and via the line 15 to the circulating water container 10 . The upper run 16 of the hydrocyclone 8 is connected via the line 17 to the circulating water tank 10 or directly to the quicklime fire-extinguishing system, suspension receiver and metering device 6 or to the gas scrubber 1 . The hydrocyclone 8 is connected via the line 18 to the belt filter 19 and the line 20 to the circulating water tank 10 . The belt filter 19 has the conveyor section 21 .

The mode of action is as follows:

The quicklime 22 is conveyed from the reservoir 14 via the conveyor system 13 into the quicklime-extinguishing system, suspension template and metering device 6 and through the pumped via line 15 sulfate enriched circulation water 23 having a sulfate content of greater than 300 mg / l from the circulation water tank 10 or directly from the line 17 deleted. The sulfate-enriched circuit water 23 is used to produce the suspension 24 . The suspension 24 is conveyed into the gas scrubber 1 via the line 5 . The scrubber suspension 25 is conveyed via line 11 into the upper part of the gas scrubber 1 with the internals (not shown) and brought into contact with the flue gases 26 introduced via the flue gas duct 3 from the incinerator, not shown.

At the same time, oxidizing air 27 is introduced via line 12 and flushing water 29 is introduced discontinuously via line 2 .

The following reactions occur:

• 1. quicklime 22 with sulfate-enriched circulating water CaO + H₂O → Ca (OH) ₂
• 2. The offset with the suspension 24 suspension scrubber 25 with oxidizing air 27, flue gases 26 and rinsing water

The reactivity of the suspension 24 is characterized by the following:

When using sulfate-enriched circulating water 23 there are reaction mechanisms

• a) Sulphate contents above the solubility product:
  Coating the Ca (OH) ₂ / CaO particles with a gypsum shell
• b) Sulphate levels below the solubility product:
  Active centers on the surface cause the Ca (OH) ₂ / CaO particles to surround themselves with a sulfate shell.

Both reaction mechanisms cause a coarsening (gritting) of the grain spectrum of the suspension 24 without their reactivity having a negative effect on the desulfurization process.

The reaction product 29 passes via line 7 into the hydrocyclone 8 , in which sulfate-enriched water 30 and gypsum sludge 31 are separated.

The sulfate-enriched water 30 passes via line 17 into the circulating water tank 10 or directly into the quicklime slaking system, suspension receiver and metering device 6 and the gypsum sludge 31 via line 18 onto the belt filter 19 . After the gypsum sludge 31 has been dewatered, the water 32 is likewise conveyed via the line 20 into the circulating water tank 10 . The dewatered gypsum 33 is removed via the conveyor line 21 . The desulfurized flue gas 34 is removed via line 4 .

If the sulphate-enriched circulating water 23 for extinguishing the quicklime 22 in the quicklime quenching system, suspension receiver and metering device 6 is introduced at a temperature greater than 35 ° C., an improvement in the grain structure of the suspension 25 can be achieved.

To improve the extinguishing process, 23 surface-active substances are introduced into the circulating water.

To improve the reactivity of the suspension 24 , the semolina in the suspension is selected in a hydrocyclone, a filter and / or a thickener (not shown) and then ground or comminuted by introducing shear forces during the extinguishing and / or dilution process.

The following advantages are achieved by the invention:

• 1. The use of quicklime is generally used Flue gas desulfurization for lignite-fired Steam boiler enables and the permissible water balance adhered to.  
• 2. The use of quicklime enables a reduction the investment and operating costs (energy saving) compared to the use of limestone in the Flue gas desulfurization from lignite-fired Steam boilers.
• 3. To delete quicklime and to Suspension production is the sulfate-enriched Circulating water used, so that by saving water optimizes the water balance becomes.

Reference list

1 gas washer
2 rinse water pipe
3 flue gas duct
4 clean gas channel
5 line
6 quicklime extinguishing system, suspension template and dosing device
7 line
8 hydrocyclone
9 line
10 circulating water tanks
11 scrubber suspension line
12 Oxidation air line
13 conveyor system
14 storage containers
15 line
16 upper reaches
17 line
18 management
19 band filter
20 line
21 conveyor line
22 quicklime
23 circulating water
24 suspension
25 laundry suspension
26 flue gas
27 Oxidation air
28 rinse water
29 reaction product
30 water
31 gypsum sludge
32 water
33 plaster
34 flue gas.

Claims (7)

1. A method for operating a flue gas desulfurization system for a lignite-dust-fired power plant, wherein a lime-water suspension is produced and introduced into the sulfur-containing flue gases via a gas scrubber and a sulfate-enriched water is produced, characterized in that quicklime is used, with the circulated sulfate-enriched Water is extinguished and diluted to a suspension and introduced into the bottom of the gas scrubber in a manner known per se. 2. The method according to claim 1, characterized in that the sulfate-enriched water with a temperature greater 35 ° C is introduced into the extinguishing process. 3. The method according to claim 1, characterized in that sulfate-enriched water with a sulfate content greater 300 mg / l is introduced. 4. The method according to claim 1, characterized in that surface-active sulfate-enriched water Substances are added. 5. The method according to claim 1 to 4, characterized in that that the sulfate-enriched water after Hydrocyclone overflow of the flue gas desulfurization system is removed. 6. The method according to claim 1 to 5, characterized in that that the semolina in suspension with a hydrocyclone, a filter and / or a thickener is selected and are then ground up.   7. The method according to claim 1 to 6, characterized in that that the semolina in the suspension by introducing Shear forces during the extinguishing and / or Dilution process.