EP0594650A1

EP0594650A1 - Granular fuel made from liquid manure, and a method of manufacturing the fuel

Info

Publication number: EP0594650A1
Application number: EP92913619A
Authority: EP
Inventors: Walter Hey; Ingo Romey; Hans Jürgen PALM
Original assignee: Bergwerksverband GmbH
Current assignee: Bergwerksverband GmbH
Priority date: 1991-07-15
Filing date: 1992-06-27
Publication date: 1994-05-04
Also published as: HUT71546A; DE4123368C1; HU9400111D0; WO1993002163A1; SK3494A3; CZ8594A3

Abstract

L'invention concerne des granulats combustibles à base de purin, notamment pour foyers à couches fluidisées, ces granulats présentant de préférence la composition suivante: 0,86 à 45 % en poids de substance sèche du purin, 83,74 à 43 % en poids de poussière de charbon (w.f.), 5,4 à 2 % en poids de chaux vive, 10 à 48 % en poids d'eau résiduelle, et ayant une granulométrie sphéroïdale comprise entre 0 et 7 mm avec une proportion de grains pulvérulents < 1 %, lesdits granulats présentant une consistance fluide et étant fabriqués en une seule étape dans un mélangeur à granuler, ainsi qu'un procédé de fabrication de tels granulats.The invention relates to manure-based fuel aggregates, in particular for fluidized bed hearths, these aggregates preferably having the following composition: 0.86 to 45% by weight of dry substance of the manure, 83.74 to 43% by weight of coal dust (wf), 5.4 to 2% by weight of quicklime, 10 to 48% by weight of residual water, and having a spheroidal particle size between 0 and 7 mm with a proportion of powdery grains < 1 %, said aggregates having a fluid consistency and being manufactured in a single step in a granulating mixer, as well as a process for manufacturing such aggregates.

Description

Fuel granules from manure and process for their production

The invention relates to fuel granules from liquid manure, in particular for fluidized bed furnaces. It also relates to processes for the production of such granules.

Fuel granules from sewage sludge are known from the publication "Granulate for incineration", Entsorga-Magazin - Entsorgungwirtschaft, September 1990, pages 60 to 62. These fuel granules consist of mechanically pre-dewatered sewage sludge, which is mixed intimately in a compulsory mixer with a dry material, not specified, and is practically granulated. The mixture produced is such that the dry substance lies above the adhesive phase of approx. 50% dry substance (TS), in order to then be dried in a special disc dryer without problems. The product can run independently, e.g. B. in a fluidized bed furnace, are burned. The composition and properties of the dry granules are not reported in detail. It is disadvantageous that thermal drying is required to produce the granules, non-combustible dry goods reduce the calorific value and, in the case of partially dried granules, the calorific value is deteriorated by the water evaporation of the residual water.

From the publication "Sewage sludge in the Federal Republic", Abwassertechnik, Issue 2, 1990, pages 71 to 74, granules made of sewage sludge which are suitable for landfill are known, which are used to increase the TS content with conditioning agents, e.g. Lime. The granulate shape is intended to improve manageability and storability and to minimize landfill costs. Since larger amounts of lime are required as a result of the use of lime as a conditioning agent or drying agent, these granules are, however, less suitable for combustion because of the reduced calorific value.

From "Recycling of sewage sludge" / Ulrich Loll, Berlin, EF-Verlag für Energie- und Umwelttechnik GmbH, volume 2, 1989, further processes for the production of fuel granules are known: In ESCHER-WYSS sludge drying (see 5.1.2 .., pages 32, 33), the sludge is granulated in a mixer using partly already dried material and dust separated in the dryer, and the wet granulate is fed via a dosing screw and a cell wheel lock fed to a fluid bed dryer. The drying is carried out by thermal energy, which is partly introduced directly into the fluidized bed dryer via steam vapors, partly indirectly through saturated steam or thermal oil. A disadvantage is the great mechanical and energy expenditure for drying granules up to 98% S.

In the TCW sludge drying (see 5.1.6., Pages 39 to 41), machine-dewatered sludge is mixed with already dried material, conveyed with a conveyor belt into the inner cylinder of a drum dryer consisting of three concentric cylinders, and from there with one Hot gas stream (400 - 500 ° C) entering at high speed is transported through the three cylinders and dried. The granulate is withdrawn from the system by 2 to 4 mm from the granular dry material produced. The remaining material is crushed in a mill and returned to the system. This method also requires a very high level of mechanical and energy expenditure for the production of the granules. From Umweltmagazin, May 1990, pages 50, 51, a process for the combustion of sewage sludge is known, in which the fresh sludge is conditioned with hydrated lime or carbide sludge and organic flocculants and iron (III) chloride are added. Further dewatering takes place by means of chamber filter presses. Instead of hydrated lime or carbide sludge, it is also possible to use electrostatic filter dust for conditioning that contains free, unused calcium hydroxide. However, this method does not produce fuel granules. The heavy metals contained therein, which require the disposal of hazardous waste, are considered to be disadvantageous when using electrostatic precipitator dust.

Similar problems as for the disposal of raw sewage sludge (thin sludge) exist for the disposal of liquid manure from animal husbandry companies.

The present invention is based on the object, while avoiding the disadvantages of the known methods, of proposing fuel granules from liquid manure which are optimized with regard to their composition and properties and which can be produced without high mechanical and energy expenditure and which are particularly suitable for combustion are suitable in the fluidized bed. To solve this problem, fuel granules are proposed, the composition and properties of which are set out in claims 1 to 3.

A further development of the fuel granules is contained in subclaim 4.

The object of the invention is achieved with respect to advantageous production processes for the fuel granules by the features of claims 5 and 6.

According to a proposal that is not yet part of the previously published prior art (German patent application P 41 11 442.6), it is known to produce fuel granules from raw sewage sludge (thin sludge). Surprisingly, it was found that comparable fuel granules can be produced from manure.

The fuel granules of liquid manure according to the invention are surprisingly fuels which are distinguished by excellent handling, since they contain hardly any dust or release them when handled. Because of their free-flowing properties due to their rounded grain shape, they are ideal for storage, transport and fuel metering. Their combustion is comparatively environmentally friendly both with regard to the smoke gases and solid residues. They have a calorific value that is comparable to dry lignite. The fuel granules of liquid manure according to the invention can be used in fluidized bed furnaces without additional carrier substances and without additional fuels, since they are very suitable as a self-propelled fuel for this type of furnace. Even the moist fuel granules with a comparatively high water content of up to 48% have a calorific value which is comparable to dried sewage sludge. These moist fuel granules can thus be burned directly in existing sewage sludge incineration plants without having to make structural changes in the furnace and waste heat system. Air-dried, as dry fuel granules, they achieve a calorific value that is comparable to dry lignite.

No costly special machines and devices are necessary for producing the fuel granules according to the invention from liquid manure. In addition to the usual pre-dewatering methods and devices, all that is required is a pelletizing mixer with feed and discharge devices, and optionally devices for the intermediate storage of the moist fuel granules for circulating air drying without supplying thermal energy.

Depending on the dry matter content of the liquid manure (thin sludge), the moist fuel granules can be produced by the appropriate addition of conditioning agents such as finely divided and dry coal and lime. These self-combustible, moist fuel granules can be poured and stored, so that they can be dried without additional energy expenditure is possible by simple circulating air drying in order to obtain higher-calorie dry fuel granules.

The production of the fuel granules is expediently carried out at the location of the manure. However, it is also conceivable to carry out the production at a central point, for example in the catchment area of smaller livestock farms or at the location where the fuel granules are fed to the combustion.

In FIG. 1 of the drawing, some preferred options for producing the self-combustible fuel granules from liquid manure are shown by way of example, and their further development into higher-calorie dry fuel granules by simple forced-air drying.

FIG. 2 shows a temperature profile of a burning test with moist fuel granules.

In a granulation unit, namely a granulation mixer 1, moist fuel granules 12 are produced from the slurry stored in a slurry tank 2. For this purpose, the granulating mixer 1 is charged with the starting materials via a slurry feed 11, a lignite dust feeder 9 and a quicklime feed 10, the individual ingredients being matched to one another such that the moist fuel granules 12 produced by the granulating mixer 1 have an average moisture content of between 37 and 48%. The addition of quicklime 10 is based on the sulfur content of the lignite dust 9. The proportions of liquid manure 11 and lignite dust 9 are to be calculated as a function of the respective moisture of these material flows in order to obtain moist fuel granules with a moisture content of 37 to 48% that are sufficiently strong and free-flowing (non-sticky and non-lubricating) and self-combustible. You can, if necessary, without using thermal drying energy, only by forced air drying, for. B. in a circulating air silo 6, in a tower trickle dryer 7 or in a drum dryer 8, are further treated until they have become higher-calorie dry fuel granules 13 between 20 and 10% moisture or less. If waste heat is available, this may shorten the drying time.

The manure 11 to be fed to the granulating mixer 1 can have 1.5 to 12% DM. The proportion of lignite dust is to be measured depending on the water content of the slurry in order to obtain moist fuel granules 12 between 37 and 48% moisture.

Instead of lignite dust 9, hard coal dust or other carbon-containing dry matter, for example wood flour or the like, can also be added to the granulating mixer 1 in appropriate proportions in order to produce combustible moist fuel granules 12 in a self-sufficient manner. It is important, however, that the moist fuel granules 12 are sufficiently firm _ Q _

and must be free-flowing in order to be easy to handle, be it for direct use as a self-propelled fuel or, if necessary, in order to be able to produce fuel granules 13 from it by circulating air drying.

The production of fuel granules according to the invention from liquid manure is described in detail below using two examples. Another example relates to a combustion attempt.

Example A

1.85 kg of a pig manure in the state of production with 6.5% dry matter are mixed with 2 kg dry lignite (10% moisture) and approx. 7% quicklime (based on the lignite) in a granulating mixer and processed into granules. The use of flocculants or the like is not necessary. These self-combustible, moist fuel granules have a moisture content of approx. 48% immediately after manufacture and are free-flowing. If necessary, high-calorie dry fuel granules are made from it, with a moisture content of 20% being reached after about 80 hours of air drying. Example B

2.5 kg of a manure made from cattle with a dry matter content of 10.2% (without the use of flocculants) are mixed with 2.6 kg of dry lignite (10% moisture) and approx. 7% quicklime (based on the lignite content) in a granulating mixer mixed and processed into granules. These self-combustible, moist fuel granules have a moisture content of 48% after manufacture and are free-flowing. If necessary, higher-calorie dry fuel granules can be made from it, whereby a moisture content of 20% is reached after 80 h of air drying or 14% after 100 h.

Example C

Combustion tests with moist fuel granules from manure

(48% H ₂ 0)

Wet fuel granules produced from a mixture of liquid manure and lignite dust were fed into a stationary fluidized bed combustion chamber with a thermal output of 300 kW as the sole fuel. In these tests, about 5 t of granules were incinerated continuously. 2 shows, by way of example, the temperature profiles during the experiment as a function of time, the numbers indicating the number of hours (h) in the fluidized bed (fluidized bed temperature 14), in the free space arranged above (free space temperature) 15) and before the downstream cyclone (cyclone temperature 16). During the start-up phase 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 fluidized bed and in the free space rise approximately uniformly. Towards the end of the heating phase a, the fuel feed into the fluidized bed is started at time C. After the heating burner has been switched off (time B), the stabilization phase b begins, which continues until time A (secondary air addition "on"). Surprisingly, in the fluidized bed, after the heating burner was switched off, the combustion process carried itself out of the moist fuel granules added and stabilized up to time A (secondary air addition "on"), so that from there until the end of the experiment (time E) a very stable combustion phase c was present, in which only very small temperature fluctuations were displayed. It can be clearly seen that these temperature profiles were very uniform from the time A at which the secondary air addition was switched on until the end of the test E. The almost straight curves show that the addition of the moist fuel nulate is also done very evenly. It can also be deduced from this that the burnup was intensive and even.

An elementary analysis is shown in Table 1 below, and further characteristic data of the moist fuel granules used are compiled in Table 2.

Table 1

Elemental analysis of wet fuel granules

Total water 47% dry residue 53% i.an, wf waf

*) wet with analysis Table 2

Characteristics of the granules

Calorific value of the fuel granules (moist) 10.2 MJ / kg

(wf) 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 of 720 to 740 ° C and a corresponding free space temperature of 840 - 870 ° C, the emission values set out in Table 3 were obtained with the addition of secondary air.

Solid samples taken from the downstream cyclone confirmed that a sufficiently high burnout of the moist fuel granules was ensured. The carbon contents in the ash samples were between C = 2.7% by weight and 3.7% by weight.

B E Z U G S Z E I C H E N L I S T E

1 granulating mixer

2 slurry tanks

6 air silo

7 tower trickle dryer

8 drum dryers

9 Lignite dust application

10 Selling calves

11 slurry application

12 moist fuel granules

13 dry fuel granules

14 fluidized bed temperature

15 Free space temperature

16 cyclone temperature

A Secondary air addition "on"

B Heating burner "off"

C fuel feeds "on"

D heating burner "on"

E End of experiment a start-up phase or heating phase b stabilization phase c stable combustion phase

Claims

1. Fuel granules from liquid manure, in particular for fluidized bed combustion, the fuel granules having the following dry substance composition:

a) 0.86 to 45% by weight of liquid manure dry matter, b) 83.74 to 43% by weight of coal dust (f.f.) and c) 5.4 to 2% by weight of quicklime,

characterized in that

d) E. 10% by weight of residual water are contained in the granules and e) they have a rounded grain size between 0 and 7 mm, a flour grain fraction <1% and a free-flowing consistency, and f) in a single process step are produced in a granulating mixer.

2. Fuel granules from liquid manure, in particular for fluidized bed furnaces, the fuel granules having the following dry substance composition:

a) 0.8 to 40% by weight of liquid manure dry matter, b) 74.4 to 38% by weight of coal dust (w.f.) and c) 4.8 to 2% by weight of quicklime,

characterized in that

d) _ <20% by weight of residual water are contained in the granules and they e) have a rounded grain size between 0 and 7 mm, a flour grain fraction <1% and a free-flowing consistency, and f) in a single process step in a granulating mixer are manufactured.

3. Fuel granules from liquid manure, in particular for fluidized bed combustion, the fuel granules having the following dry matter composition:

a) 0.4 to 23% by weight of liquid manure dry matter, b) 74.4 to 38% by weight of coal dust (w.f.) and c) 4.8 to 2% by weight of quicklime,

characterized in that

d) <_ 48% by weight of residual water are contained in the granules and they e) have a rounded grain size between 0 and 7 mm, a flour grain fraction <1% and a flowable consistency, and f) in a single process step in one Granulating mixers are made.