SK101093A3 - Granulated fuel from slurry and process for producing it - Google Patents

Abstract

The invention relates to granulated fuel from slurry, especially for fluidised-bed furnaces, in which the granulated fuels preferably have the following composition: 0.86-45 wt. % slurry dry matter, 87.34-43 wt. % coal dust (w.f.), 5.4-2 wt. % spent lime, 10 wt. % residual water and a rounded grain size of between 0 and 7 mm, a powdered grain content of < 1 % and a pourable consistency, and are produced in a single process stage in a granulating mixer, and process for producing such granulates.

Description

Technical field

The invention relates to granulated sludge fuels after clarification, in particular for fluidized bed furnaces. It further relates to a process for the production of these granules.

I

BACKGROUND OF THE INVENTION

The granulated fuels from clarification after purification were as shown in the Granulat fiir Verbrennung, Entsorge-Magazin-Entsorgungsvirtschaft, September 1990, pages 60-62. with unmarked dried material and practically granulated. The product mixture is formed so that the dry matter is above the tackiness phase of about 50% dry matter (TS) so that it can then be dried without disturbance in a special disc dryer. The product may be self-combusting, for example, in a fluidized bed furnace. The composition and properties of the dry granules are not described in detail. A disadvantage is that heat-drying, a non-combustible material, kt, ore, is necessary for the production of granules _; it has previously been dried to reduce the calorific value and, in the case of partially dried granules, the calorific value also deteriorates by evaporation of the residual water.

From the Kärschlamm in der Bundesrepublik, Abwassertechnik, Vol. 2, 1990 pages 71-74, sludge granules after clarification are known which can be depressed and which are supplemented with conditioning agents, for example lime, to increase the dry matter content. The shape of the granulate is intended to improve the handling and shelf life of the granulate and to minimize deposition costs. However, due to the fracture that due to the use of lime as a conditioning agent or as a drying agent and larger amounts of lime are necessary, these granules are less suitable for combustion due to reduced calorific value. ^;

Other processes for the production of granulated fuels are known from Recycling von Klärschlamm / Ulrich Loll, Berlin, EF-Verlag Flir Energie- und Umweittechnik GmbH, Volume 2,1989 ^:

For ESCHER-WYSS sludge drying / under 5.1.2, page 32,

and s 33 / sa sludge granulated Ί 1 and material and dryer ! 1 _Λ 1 granulate the leads

Idled dust in the mixer and wet dispensing screwdriver and articulated wheel passage into the fluid bed dryer. The drying is carried out by means of thermal energy, which is supplied in part directly by means of steam vapor, partly indirectly as saturated steam or Lerraoole to the fluidized bed dryer. The disadvantage is the high mechanical and energy expense for drying granules of up to 98% dry matter (TS ').

In TCW sludge drying (under 5.1.6, pages 39 to 41), the machine-dewatered sludge is mixed with the material that has been previously dried, conveyed by a conveyor belt to an inner cylinder of a drum dryer consisting of three concentric cylinders and transported there by a hot stream. gas (400 to 500 ° C), which enters at high speed, three cylinders and dried. From the granular dry material produced, a granulate of 2 to 4 mm is discharged from the system. The rest of the material is milled and returned to the system: even at this dimension in the process, a very high machine and energy cost for the production of the granulate is necessary.

From Umweltmagazine, May 1990, pages 50, b1, a method of burning sludge after clarification is known, in which fresh sludge is produced. It is conditioned with calcium hydroxide or carbide sludge as well as with the addition of organic flocculants or ferric chloride. Other chamber filter presses.

Dewatering is performed Instead of calcium hydroxide or carbide sludge, electrofiltration dust containing free, unused calcium hydroxide may also be used for conditioning. In this process, the granulated fuel is a disadvantage of the use of electrofiltration dust, which does not contain the heavy metals which it requires. consider waste disposal in a special way.

SUMMARY OF THE INVENTION It is an object of the present invention to provide, in order to overcome the drawbacks of the known processes, granulated sludge fuels after clarification which are optimum in terms of their composition and properties and can be produced without major mechanical and energy costs. for fluidized bed combustion.

SUMMARY OF THE INVENTION

To solve this problem, granulated fuels are proposed, the composition and properties of which are set forth in claims 1 to 3.

A further embodiment of the granulated fuel is contained in claim 4.

The object of the invention is solved preferably by a method for producing granulated fuels according to the features of claims 3 to 8.

The granulated sludge fuels after clarification according to the invention are, surprisingly, fuels with which

Banip, manipulate and sprinkle because they hardly contain release with them. With regard to their condition due to spherical dust or to their grain shape capability, they are grain shape optimal for storage, transport and fuel dosing. Their combustion is environmentally friendly both with regard to flue gases and solid residues.

The granulated sludge fuels after clarification according to the invention can be used without additional carriers and without additional fuels, since they are self-fueling. Already wet granulated fuel with a relatively high water content of up to 47% has a calorific value which is comparable to dried sludge after clarification. Thus, these wet granulated fuels can be combusted directly in the present sludge incineration plant after clarification, without having to make structural changes to the furnace system and the waste heat recovery plant. Air-dried, as dry granulated fuels, has a calorific value which is comparable to that of dry brown coal.

No expensive special machines and equipment are required for the production of the granulated fuel according to the invention. In addition to conventional pre-dewatering methods or pre-dewatering devices, only granulate mixers with feed and discharge devices, as well as a device for intermediate storage of the raw granules for circulating air drying without heat supply, are necessary.

- ^; ?

Depending on the dry matter content of the sludge after clarification (thin sludge) or the sludge after clarification of the pre-dewatered flocculation and gravity filtration, the wet granulated fuels can be produced by suitable addition of conditioning agents such as finely divided and dry coal and lime. Optionally, the desired drying can be carried out without additional energy cost by simply circulating air drying to obtain higher calorie-dry granulated fuels.

In addition to the raw sludge after clarification (thin sludge) and flocculation and gravitational dewatering of the thickened sludge after clarification, sludge after clarification may be treated in depots and digester ponds with a residual moisture content of, for example, 70-80% to self-combustible wet granular or granulated for higher calorie dry granulated fuels by simply circulating air drying.

The production of granulated fuels is preferably carried out at the point of sludge formation after clarification. However, it is also possible to carry out production at a central location, for example within the reach of smaller ones

or at the site to which the granulated fuels are to be supplied.

The preferred treatment of the granulated fuels from clarification after clarification, especially for a fluidized bed furnace, has the following composition and from 0.86 to 45% by weight. b / 83.74 to 43% by weight. c / 5.4 to 2% by weight. quicklime, 10% w / w. residual water.

Another advantageous treatment of the granulated fuel clarification, in particular for a fluidized bed furnace, of the following composition:

and / 0.8 to 40% by weight. b / 74.4 to 38% by weight. c / 4.8 to 2% by weight. quicklime and d / a · 20% by weight. residual water.

treatment of granulated / fuel furnace with fluidized bed sludge dry matter after clarification,. coal dust (anhydrous), quicklime, water.

i, 1

Also, from each computer, it shows from the slurry to the computer

Third preferred clarifications, especially for the following composition and / 0.4 to 23% by weight. b / 49, 3 to 29 wt% c / 3.3 to 1 wt%. d / 4a 47% residual

Brief Description of Drawings _f

In FIG. 1 illustrates, by way of example, some advantageous possibilities for producing self-combustible granulated fuel from sludges after clarification, as well as their further treatment to the above-mentioned caloric dry granulated fuels by simple circulating air drying.

In FIG. 2 is the course of the combustion experiment with wet granulated fuels.

I

Example 1 is cut off

To everyone in FIG. 1 is a common granulation unit, namely a granulation mixer 7, in which wet granulated fuels 12 are produced and which are supplied through a sludge charge 11 after clarification, a charge 9 with brown coal dust and a charcoal lime charge, the individual additives being matched to each other. such that the wet granulated fuels 12 have a mean humidity of between 35 and 47%.

à

In this case, the quicklime charge 10 is oriented according to the sulfur content of the lignite dust. The proportions of the amount of sludge 11 after clarification and the brown coal dust 9 have to be calculated according to the current humidity of this stream of substances in order to obtain moist granular fuels 12 with 35 to 47% moisture, which are sufficiently strong and capable of flowing. and granulated fuels 12 which are self-combustible. Alternatively, they can be further processed by drying without the need for thermal drying energy

surroundings by air, in Tower shower dryer 7 and 1 ebo drums j dry i arn i 8 when obtained higher caloric dry granulated fuels 12 with 20 to 10 % moisture or less. if it is usable waste heat can the in case of short circuit time dried i a. * 6 / e

The sludge 11 after clarification, which is introduced into the granulation mixer 1, may be thin sludge with 1.5 to 8 ‘4 dry matter (TS), which is fed from the sludge slurry tank 2. In this case, the proportion of lignite dust is determined to be reasonably high enough to produce wet granulated fuels 12 with a moisture content of up to 47%.

However, the sludge can also be further dewatered first, k

for example by flocculation or filtration 15 to 15 to 35% dry matter or gravity drainage 4 to 15 to 25% dry matter, rather than

I is introduced into the granulation mixer f. In these cases, the proportion of brown coal dust additive 9 is determined to be less than that of thin sludge tank 2 additives.

However, the sludge mixer 1 can also be fed into the granulation mixer after clarifying 2 of the depot or digester pond 5 with 20 to 35% dry matter (TS). Alternatively, the dry matter content can be further increased by the use of special other dewatering devices of known type.

Instead of the lignite dust 9, quartz lime or other dry carbon-containing materials, for example wood flour or the like, may also be introduced into the granulation mixer 1. However, it is important that the wet granulated fuels 12 are sufficiently strong and capable of flowing to be used as self-propellant fuels, or they can be made from them by air-drying higher caloric dry granulated fuels. fuels.

Exemplary embodiments of the invention

Next is using a few examples. the production of granulated fuels according to the invention described in detail.

Example 1

The sludge discharged in the clarifier with a dry matter content of 2% was flocculated with the addition of a synthetic organic β1 reagent, pre-dewatered by gravity filtration and then adjusted to a residual moisture content of 80% by pressure filtration.

1.4 kg of dewatered sludge after clarification with a residual moisture of 80% were mixed, in a granulator mixer, with 1.0 kg of finely divided dry brown coal (about 10% moisture) with the addition of 5% quicklime based on brown coal and processed to round granulates with a maximum grain size of about 4 mm. The wet granulated fuels were sufficiently strong as well as flowable and could be stored in silo without any problem. They had a moisture content of about 40% directly after production. After 24 hours of circulating air drying, granulated fuels were obtained with a moisture content of about 20% and after 60 hours with a moisture content of about 10%. Already wet granulated fuels could be burned automatically. The dry granulated fuels still contained enough moisture so that they could be handled practically without dust formation.

Examples 2 to 5

To improve dewatering and increase the filtration rate, the flocculated sludge suspension after clarification was further supplemented prior to filtration with filtration aid in the form of solid particles (0.1-0.3 mm). As a filter aid, quartz coal (Example 2), coke abrasion (Example 3), wood flour (Example 4) or brown coal dust (Example 5) were used in a ratio of 1 ^: 1 based on the present amount of dry sludge substance. As a result, a further reduction of the water content of the filter cake by 2 to 5% points to 22 to 25% of dry matter was achieved after pressure filtration. Further processing to wet or dry granulated fuels was carried out as in Example 1.

Príklad.6

1.4 kg of the slurry after clarification with 2% dry matter was mixed without pre-dewatering in a granulating mixer with 2 kg dry brown coal dust (10% moisture) and 5% quicklime (based on lignite) and processed to wet granulated fuel. The self-combustible granules had a residual moisture of 44% directly in the production. After air drying, they were rt

obtained dry granulated fuels having a moisture content of about 20%.

Pr.Lkl.ad_7

According to another mixing variant, a brown coal dust with a higher humidity of 22% was used. 0.8 kg of sludge suspension after clarification with 2% dry matter was mixed in a granulation mixer with

2.0 kg of this wetter brown coal dust with 5% quicklime, based on the amount of brown coal and processed into wet granulated fuels. These flammable? the granulates had 36.7% moisture after mixing. After 24 hours air drying, they could be used to produce dry granulated fuels with a *.

18.6%.

Example 8

The already mined sludge after clarification of 2 digester ponds with a residual water content of 79% was mixed with brown-coal dust for the production of granular fuel, which was processed

1.5 kg of sludge after clarification from the digester (79% moisture) with 1.0 kg of brown coal dust (10% moisture) p. by adding 5% quicklime, based on the amount of brown coal, in a granulating mixer for wet granulated fuels. These had a production humidity of 40.2%. After 60 hours of air drying, they were produced from dry granular fuels with a moisture content of 16.4%.

Example 9

2.1 kg of dry sludge after clarification (<1% H;: 0) was mixed in a granulation mixer with 1.5 kg of municipal sludge after clarification (80% H2O) and 5% quicklime (based on quarry sludge) and processed for self-combustible, wet granulated ¹ t fuel, capable of flowing. These exhibited a moisture content of 35% directly after production and higher calorie dry granulated fuels showed a residual moisture content of &lt; 20% after 24 'air drying.

The granulated fuels produced according to Examples 1 to 9 are obtained after the granulation process as round grain pellets with an average grain size of 1 to 4 mm. These wet granulated fuels have a water content of 35 to 47% (65 to 53% dry matter), are capable of flowing and can be mechanically loaded.

The calorific value of these raw granules is 10 to 14 MJ / kg and corresponds to the calorific value of dry clean sludge after clarification.

I

Surprisingly, they can be introduced into the fluidized bed directly by means of dosing devices without further drying and burned therein, as shown in the following example.

Example 10

Experiments with combustion of wet granules with cooking fuels (47%

H ₂ O).

The granular fuel produced from the mixture of municipal sludge after clarification and brown coal dust was also introduced into a stationary fluidized bed combustion chamber with a heat output of 300 kW as the only fuel. In these experiments about 5 tons of crude granulate were continuously burned.

Fig. 2 shows an example of temperature courses during the experiment versus time, with the digits indicating the number of hours (h) in the fluidized bed (temperature 14 of the fluidized bed), in the open space arranged above it (temperature 15 in open space) and before the next cyclone ( 16 cyclone). During the initial or heating phase a, which lasts from time D, switching on the heating burner, until time B, switching off the heating burner, the temperatures in the fluid bed and in the free space increase uniformly. At the end of the heating phase a, fuel is introduced into the fluidized bed at time C. After switching off the heater burner (moment B), the stabilization phase b begins and continues until moment A (addition of secondary air .do). Surprisingly, the heater burner continued to find that after switching off in the fluidized bed the combustion process automatically due to the added wet granulated fuel and stabilized up to point A (addition of secondary air to) so that the deposition until the end of the experiment (point E) Stable combustion phase c, during which very little temperature fluctuations occurred. It can be clearly seen that these temperature courses from the time A when the secondary V2duch was added until the end of experiment E were very uniform. The almost straight lines of the curves show that the addition of wet granulated fuels was also performed very evenly. Furthermore, it can be deduced that the burn was also intensive and even.

Further, elemental analysis is shown in Table 1 and other characteristic values of the wet granulated fuels used are summarized in Table 2. b

Table 1

Elemental analysis of wet granulated fuels dry all water to% 53%

J .1 ! in. an * anh. zvi h.vodoi ’L · 1 Water % 0, 6 - - ] 1 popo1% .14,8 4, 9 - and C% 53, 3 53.6 63.0 H% 4, 46 4, 49 5.28 'j J N% 1.38 1.39 1.63 0% ¹ 24, 5 24, 6 28.9 WITH % 0, 99 1.0 - • i j *

x / moisture in the analysis

Table 2

Characteristics of the crude granule the calorific value of the granulated fuel (wet) 10, 2. MJ / kg (Anhyd.) 21.4 MJ / kg bulk density 0.5 kg / dm ³ CaO content ‘ 2, 44% by weight

At an almost constant fluidized bed combustion temperature in the combustion phase c 720 to 740 ° C. and a suitably set room temperature of 840 to 870 ° C with the addition of secondary air, the emission values given in Table 3 below occurred. ~~

Table 3

Emission value

WHAT  35 until 40 mg / m NOx : 80 until 130 mg / m no ₂ 5 until 15 mg / m

Solid samples taken from the cyclone involved further confirmed that a sufficiently large burn of wet granulated fuels was detected. The carbon contents in the ash samples varied between C = 2.7% by weight. up to 3.7% by weight.

Claims (1)

PATENT CLAIMS 1. Granular fuels from sludge after clarification, in particular for fluidized bed furnaces, characterized in that the granulated fuels have the following composition: and / 0.4 to 45% by weight. b / 83.74 to 29% by weight. c / 5.4 to 1% by weight. quicklime, d / - 47% by weight. residual water, (e) have spherical grains of 0 to 7 mm in size, 1 'the proportion of grains in the form of flour <1% with a flowable consistency as well as (f) are obtainable by a single process step in a granulating mixer. . 2. Granular fuels according to claim 1, characterized in that they have the following grain distribution: size 0 until 0, 63 mm = 0.4 y 0, 63 until 1.0 mm = 32.3 1; 0 until 2, Ó mm 46.9 % 2, 0 until 4.0 mm = 19.8 % > 4.0 mm = 0.6 K. Third process manufacturing granulated fuels by one from claims 1 or 2, ' v y s ! n a č u j ú c i sa t ý m. that the 0.8 kg up to 1.4 kg of municipal sludge after clarification (thin kal) with 1.5 to 8.0 dry matter, 2.0 kg of brown coal dust with 10 to 20% water content and 0.10 kg of quick lime are shaped in a granular blend into spherical wet granulated fuels, capable of flowing, with 35% to 47% and, if appropriate, these are then air-dried for 10 to 60 hours to dry granulated fuels with a residual moisture content of 20 to 10%. T A process for producing granulated fuels according to claim 1, characterized in that the municipal sludge, after clarification (thin sludge), is pre-drained by the addition of organic or &quot; inorganic flocculants by gravity teach 15 to 25% dry matter, 1.2 kg to 1.5 kg of pre-dewatered sludge after clarification, 1.5 kg of brown coal dust with 10 to 20% water content and 0.05 kg of quick lime granulation cleaners. 5. A method according to claim 3, characterized in that the municipal sludge, after clarification (thin sludge) with or without the addition of flocculating agent, is dewatered in advance by machine to 25 to 35% dry matter, 1.5 kg to 1.8. kg of pre-dewatered sludge after clarification, 1.0 kg of brown coal dust with 10-20 20 water content and 0.05 kg of quick lime are introduced into the granulation mixer. Method according to claim 3, characterized in that the pre-dewatered sludge after clarification is mixed in the filtration stage using coal stony, coke abrasion, wood flour or lignite as a filtering agent in a ratio of 1 = 1 and pressurized. sfiitruje. 7. A process according to claim 3, characterized in that the municipal sludge (thin the sludge is thickened in digester ponds to 20 to 35% dry matter and 1.2 to 1.8 kg of concentrated sludge after clarification, 1.0 kg of brown coal dust with 10 to 20% water content and 0.05 kg of quick lime are introduced into the granulation mixer. 8. A method for the production of granular fuels according to claim 5, you are the th značujúci ^1, in place of _t lignite dust is used as dry matter carboniferous powder, wood flour or other finely divided dry substance containing carbon. I • 14. I t List of reference numbers granulation mixer 1 ¹ thin slurry tank 2 flocculation and filtration 3 gravity drainage 4 digester pond 5 circulating air silo 6. Even tower shower dryer 7 drum dryer 8 brown coal dust 9 quicklime 10 sludge after clarification> 11 wet granulated fuels 12 dry granulated fuels 13 fluid bed temperature 14 free space temperature 15 cyclone temperature 16, addition of secondary air to A heater burner from B addition fuel “to C heating burner to D end of experiment E initial phase or heating phase and stabilization phase b stable combustion phase cit fe