IE911640A1

IE911640A1 - Combustible agglomerates comprising a granular carbonaceous¹combustible material and a binder and process for their¹manufacture

Info

Publication number: IE911640A1
Application number: IE164091A
Authority: IE
Original assignee: Combustibles De Normandie
Priority date: 1990-05-16
Filing date: 1991-05-13
Publication date: 1991-11-20
Also published as: NO911891D0; EP0457635A1; RU2016048C1; FR2662172B1; NO911891L; FR2662172A1

Abstract

Fuel conglomerate comprising a granular solid carbonaceous fuel material and a binder, characterised in that the said fuel material comprises granular lignite coke and in that the said binder consists of starch containing anthracite fines.

Description

Combustible agglomerates comprising a granular carbonaceous combustible material and a binder and process for their manufacture The present invention relates to combustible 5 agglomerates comprising a granular solid carbonaceous combustible material and a binder; it also relates to a process for the manufacture of such agglomerates.

Solid carbonaceous combustible materials are nowadays employed in the most diverse fields and espe10 cially in many industrial processes, in particular in processes for steel manufacture or recarburisation of steels and irons, where they are used as a source of energy, of reducing material and/or of carburising agent.

In the case of these metallurgical processes use is currently made, as combustible material, of granular lignite coke which is generally obtained by milling lignite, followed by its coking, this lignite coke being characterised by a high brittleness, a granular structure, a bulk density of the order of 0.5 and a very high specific surface which can be up to 300 m2/g.

However, the use of lignite coke in the above metallurgical processes presents some disadvantages. Thus, for example, the introduction of this coke into converters through side chutes is awkward since, because of its low density, it is difficult to make it enter the bulk of the molten metal. In addition, because of its pulverulent state, some of this coke is lost as a result of its ignition at the entry of the converter. Moreover, and still because of its pulverulent state, its conveying, its handling and its storage are tricky.

The Applicant Company has therefore attempted to bring this lignite coke into a denser, nonpulverulent form capable of being introduced into converters in order to enter easily the bulk of the molten metal therein merely by gravity. It has therefore carried out an indepth study with a view to producing agglomerates from lignite coke and a binder, it being necessary for these agglomerates to have sufficient mechanical strength to enable them to be handled under relatively severe conditions .

Since these studies showed that the use of a binder consisting solely of starch resulted in agglome15 rates which were not very satisfactory from the viewpoint of their mechanical strength, the Applicant Company has attempted to use starch in combination with a reinforcing filler, it being necessary for such a filler to fulfil four conditions, namely to have a high specific mechani20 cal strength, to demonstrate a high adhesiveness towards starch, to be compatible with lignite coke, whose very high specific surface makes it quite a special product and, preferably, to be itself combustible to limit ash formation.

It has thus succeeded, according to the invention, in developing an agglomerate, of the briquette, nut or pellet type, having the desired properties and comprising a granular solid carbonaceous combustible material and a binder, in which the said combustible material comprises the abovementioned lignite coke and the said binder consists of starch within which anthracite fines are distributed, acting as a reinforcing filler for the matrix formed by the starch.

In this agglomerate the lignite coke will be preferably chosen to have a particle size not greater than 5 mm, the anthracite fines having, for their part, preferably a particle size of the order of 0.5 to 4 mm.

Furthermore, the proportion by weight of lignite 10 coke, of starch and of anthracite fines within the agglomerate according to the invention is advantageously from 60 to 90 % (preferably 65-80 %), 5 to 10 % and 5 to 30 % (preferably 10 to 25 %) respectively, a particularly preferred composition being as follows: lignite coke 72 % by weight, anthracite fines 20 % by weight, starch 8 % by weight.

The starch used according to the invention may be chosen from starches of all kinds and especially from natural starches, for example from corn or from wheat, and natural starches which have been made soluble in water by a cooking-extrusion treatment.

The process according to the invention for the continuous or noncontinuous manufacture of the agglomerate described above is characterised in that it comprises: - blending, preferably at a temperature of 100 to 110°C, of appropriate quantities of lignite coke, of anthracite fines and of starch, with water employed in a quantity of 15 to 40 %, preferably 15 to 35 % by weight, of the sum of the weights of the lignite coke and of the anthracite fines, - treating the resulting paste to bring it into the form of agglomerate, and - drying the agglomerate obtained.

The water employed in this process is advantageously used partially in the form of liquid and partially in the form of superheated steam, for example at a temperature of 150 to 200°C, especially 185°C, the relative proportions of liquid water and of steam being chosen so that the mixture to be blended is at a temperature of 100-110°C.

The treatment of the paste to bring it into the form of agglomerate relies on conventional agglomeration techniques described extensively in the literature; they may be especially briquetting, extrusion and pressure compacting techniques .

As for drying, this advantageously consists in subjecting the agglomerate to stoving, preferably in a oven with hot air circulation at 110-130°C.

The agglomerate according to the invention has very good cohesion, it being possible for its compressive mechanical strength to reach values of the order of 150x10s Pa.

To illustrate the invention, an example of manufacture of the agglomerate according to the invention is given below, no limitation being implied.

Into a blender comprising horizontal arms integrally attached to a vertical shaft rotating at revolutions/min are introduced, on the one hand, 72 kg of lignite coke, 20 kg of anthracite fines and 8 kg of natural wheat starch and, on the other hand, 20 kg of hot water at a temperature close to 100 °C. Furthermore, superheated steam at 185°C is introduced into the blender through nozzles distributed over the entire height of its side wall, the quantity of steam injected by these nozzles being chosen so that the blended mixture has a temperature of the order of 100-110°C.

After a residence time of the said mixture in the blender of preferably at least 3 min 30 s the resulting paste is removed from the base of the blender and taken to a compacting device of the roller press type which has cavities imparting the desired shape to the agglomerates.

The agglomerates thus obtained are then deposited on a metal belt running through an oven with hot air circulation at 110-130°C, the speed of travel of this belt being chosen so that the residence time of the said agglomerates inside the oven is at least 2 hours.

The resulting dried agglomerates have a bulk density of the order of 0.7 and a compressive strength, measured by means of a compressometer of the Sahut Conreur type, of the order of 150x10s Pa.

IE 911640 - 6 -

Claims

1. Combustible agglomerate comprising a granular solid carbonaceous combustible material and a binder, characterised in that the said combustible material 5 comprises granular lignite coke and in that the said binder consists of starch containing anthracite fines.

2. Agglomerate according to Claim 1, characterised in that the lignite coke has a particle size of not more than 5 mm. 10

3. Agglomerate according to Claim 1 or 2, characterised in that the anthracite fines have a particle size of 0.5 to 4 mm.

4. Agglomerate according to one of the preceding claims, characterised in that it contains from 60 to 90 % 15 by weight of lignite coke.

5. Agglomerate according to one of the preceding claims, characterised in that it contains from 5 to 10 % by weight of starch.

6. Agglomerate according to one of the preceding 20 claims, characterised in that it contains from 5 to 30 % by weight of anthracite fines.

7. Agglomerate according to one of the preceding claims, characterised in that it contains, by weight, 65 to 80 % of lignite coke, 5 to 10 % of starch and 10 to 25 25 % of anthracite fines.

8. Process for the manufacture of the agglomerate according to one of Claims 1 to 7, characterised in that it comprises: - blending, at a temperature of 100-110°C of appropriate quantities of granular lignite coke, of anthracite fines and of starch, with water employed in a quantity by weight equal to 15-40 % of the sum of the weights of the lignite coke and of the anthracite fines, - treating the resulting paste to bring it into the form of agglomerate, and - drying the agglomerate obtained.

9. Process according to Claim 8, characterised in that the water is used partially in the form of liquid and partially in the form of superheated steam.

10. Process according to Claim 8 or 9, characterised in that the drying is carried out by stoving in an oven with hot air circulation at 110-130°C.

11. An agglomerate according to Claim 1, substantially as hereinbefore described.

12. A process for the manufacture of an agglomerate according to Claim 1, substantially as hereinbefore described

13. An agglomerate according to Claim 1, whenever manufactured by a process claimed in a preceding claim.