GB2148321A

GB2148321A - Agglomerates of solid combustible materials and process for their production

Info

Publication number: GB2148321A
Application number: GB08423581A
Authority: GB
Inventors: Jacques Grootjans
Original assignee: Labofina SA
Current assignee: Labofina SA
Priority date: 1983-09-22
Filing date: 1984-09-18
Publication date: 1985-05-30
Also published as: DE3434730A1; NL8402877A; BE900611A; FR2552445A1; GB8423581D0; LU85012A1

Abstract

There is disclosed agglomerates of finely divided solid combustible material, which consist in a mixture of said combustible material and asphaltenic compound and which may be used as combustible without prior desmoking treatment.

Description

SPECIFICATION Agglomerates of solid combustible materials and process for their production The present invention relates to agglomerates or briquettes of finely divided combustible materials, more particularly to briquettes containing coal. The invention relates also to a process for producing these agglomerates or briquettes.

Large amounts of finely divided or dusty combustible materials are available in some industries, such as in coal mining where coal fines or coal breezes result from the processing of coal, e.g. washing and grinding of run-of-mine coal, or from a desintegration during storage. These fines are not easily handled and, therefore, their economic value is low.

A method for increasing the economic value of these fine particles of combustible materials consists in agglomerating them by using binders, such as coal tar, bitumen, lignosulfonates, namely calcium and magnesium lignosulfonates, synthetic resins or their mixtures and thereafter compressing into briquettes.

However, these briquettes do not always give satisfactory results. Some of them break during further handling. Other briquettes burn with evolution of an important amount of smoke. This drawback might be obviated by subjecting the briqueftes to a desmoking heat treatment. However, such a treatment requires investments, gives rise to pollution problems and increases the manufacturing costs. Furthermore, some binders are only suitable when the water content of the solid combustible is low. But coal fines contain a substantial amount of water, which may reach 20% in some cases. The water content could be decreased by a drying step, but once more this treatment leads to further expenses. On the other hand, some mixtures of coal fines and binders must be subjected to a caking heat treatment in order to produce briquettes having a satisfactory mechanical strength.An evolution of noxious gaseous products generally results from this treatment, such as (SO), in case of lignosulfonates as binders, and investments are also required to eliminate these products.

An object of this invention is to obviate these drawbacks. Another object of the invention is to provide combustible agglomerates which are easily produced and which exhibit a high strength. A further object of the invention is to provide briquettes which do not require a desmoking treatment in order to meet the usual requirements concerning the smoking properties of fuels.

According to this invention, the solid combustible briquettes comprise essentially a finely divided solid combustible and an asphaltenic compound.

The process for producing these briquettees consists in blending finely divided solid combustible with an asphaltenic compound and in compressing the blend, namely in a mould to obtain briquettes having the desired shape.

Many types of solid combustibles may be used to produce the briquettes of thins invention. These combustibles are generally waste products from various industries and are more particularly coal fines or even coal breezes. It is to be understood that the invention is not limited to the use of fine particles; it contemplates also cellulosic fibers, wood chips and other materials of low economic value.

Moreover, the invention is not limited to briquettes produced from waste materials; the briquettes may also be manufactured from usual solid combustibles which were especially ground. With regard to the user's interest, it is more advantageous to manufacture briquettes from coal, namely anthracite, optionally in admixture with a lower amount of another finely divided solid combustible. Generally, the anthracite so used will have a particle size which does not exceed about 5 mm and which may be lower than 2 or3 mm.

The therms "asphaltenic compound" are to be understood as including the product resulting from the treatment with a solvent of the residue obtained by distilling crude petroleum at atmospheric or sub-atmospheric pressure. As solvent, it may be cited propane, butane, pentane or their mixtures, the treatment being carried out either at low or at elevated temperatures. The composition of the asphaltenic compound depends mainly upon the type of treated residue and the rate of extraction with the solvent. Generally, the employed asphaltenic compound will have a penetration (according to ASTM D-5) lower than 10 ddm and which is preferably about 0.This corresponds mainly to an asphaltenic compound containing C7 asphaltene (asphaltene insoluble into n-heptane according to IP. 143) in a minimum amount of about 30% and having a softening point in the range of 90" to 1 50 C. The asphaltenic compound is a black, vitreous product.

An asphaltenic compound having a softening point higher than 1 50 C may be used and the produced agglomerates burn with evolution of a reduced amount of smoke. However, there is a risk to obtain agglomerates which are friable when they are manufactured by using a finely divided solid combustible material. The type and amount of asphaltenic compound to be used depend upon the particle sizes of the combustible material, the required mechanical strength of the agglomerates and their burning characteristics, more particularly the evolution of smoke. The skilled in the art worker can easily determine the type and amount of asphaltenic compound to be employed when he knows the type and particle sizes of the combustible.Generally, an asphaltenic compound having a softening point within the range 900.11 50C will be employed in an amount of about 4 to 6%, based on the weight of agglomerate, to produce briquettes from coals, having a particle size which does not exceed about 4 mm.

The briquettes of the invention are prepared by mixing and coating finely divided solid combustible with the asphaltenic compound and then compressing into a mould to obtain briquettes having the desired shape. The coating operation may be carried out either at room temperature, by using a ground asphaltenic compound, or applied at a higher temperature, with a melted or at least softened asphaltenic compound. The heat control of the melted compound is generally such that excess water is evaporated and, therefore, a drying step of wet coal is not required before pressing. The agglomerates may also contain some additional materials, such as oils or a lower amount of another binder.

The amount of asphaltenic compound to be used in order to obtain stable briquettes may vary within wide limits. This amount depends upon the type of solid combustible used, its particle size, the composition of the asphaltenic compound, the optional use of additional binder, etc... Satisfactory results are already obtained when the amount of asphaltenic compound is about 2.5% based on the total weight of briquette. Larger amount of asphaltenic compound may be used, as this compound has a high heating value. The combustible briquettes may contain 50% or even more than 50% of asphaltenic compound, based on the total weight of briquette.

The upper limit in percentage of this compound depends upon its sulfur content, which depends upon the sulfur content of the treated residue.

Generally, briquettes having a suitable strength and a low sulfur content are obtained when the amount of asphaltenic compound is in the range of about 2.5% to 15%, and more particularly between about 3% and about 10%, based on the weight of briquette.

The agglomerates of the invention may also contain some addivites, such as fillers, combustion improvers and the like.

The present invention is illustrated by the following, not limitative examples. The smoke index mentioned in these examples has been determined by using the following technique: Aflat cylindrical cup with a fine wire gauze bottom is placed under an invested glass laboratory funnel that functions as a hood. The stem of the invested funnel is fixed to a glass tube which acts as short chimney. An electrostatic precipitation is fixed on the top of this chimney.

A sample of the agglomerate to be tested is placed in the cup and is heated up to its ignition temperature by means of heat radiated from below by an incandescent electrical burner. The combustion air is sucked through the gauze bottom and the tested agglomerate.

The invested funnel, the glass tube and the precipitator are weighted before and after combustion of the sample. The amount of combustion products collected in these parts of the apparatus is the smoke index. This amount must not exceed 11 g per kg of combustible for a "smokeless" combustible.

The following examples show that the agglomerates or briquettes of this invention are smokeless combustibles. They can be used directly and do not require a desmoking step. Moreover, they are easily manufactured from coal fines, which were often waste products in many industries.

Example 1 An asphaltenic compound containing 35% asphaltene and having a penetration of 0 ddm (ASTM D.5) has been melted at about 11 50C and then mixed with fine particules of anthracite. The amount of asphaltenic compound was 4.5%, based on the weight of the mixture. The mixture has been poured into cylindrical molds and pressed.

Cylindrical agglomerates having a smooth, vitreous surface were obtained. They were tested for their impact strength, in comparison with similar cylindrical agglomerates prepared from a mixture of particles of the same anthracite and 35% bitumen.

The latter agglomerates had a lower resistance (formation of splinters), whilst the agglomerates of this invention remained undamaged under the same test conditions. Moreover, they had a noticeable attrition strength.

Example 2 Ruhr anthracite having a particle size which did not exceed 4 mm and a smoke index of 2 was mixed at room temperature with an asphaltenic compound having a softening point of 107"C. The mixture containing 95% by weight of coal and 5% asphaltenic compound was used to manufacture briquettes by pressing into a mold.

The smoke index of the briquettes was 9.

Example 3 The procedure of Example 2was repeated to manufacture briquettes from a mixture containing 94% Welsh anthracite (smoke index:1) and 6% asphaltenic compound (softening point : 95 C).

The smoke index of the briquettes was 9.

The crushing strength has been determined by using cylindrical briquettes. Each briquette was placed between a static plate and a mobile plate (speed : 847 micrometers per second). The direction of the compression force was perpendicular to the axis of the briquette. The crushing strength was 2.000 Newtons.

By way of comparison, commercial briquettes were tested and the best result was 1.000 Newtons.

Claims

1. Agglomerates of finely divided solid combustible material, which consist in a mixture of said combustible material and asphaltenic compond and which may be used as combustible without prior desmoking treatment.

2. Agglomerates according to claim 1, wherein the asphaltenic compound content is comprised between 2.5% and 50%, based on the total weight of agglomerate.

3. Agglomerates according to claim 2, wherein the asphaltenic compound content is comprised between 2.5% and 15%, namely between 3% and 10%, based on the total weight of agglomerate.

4. Agglomerates according to any of claims 1-3, wherein the combustible material is mainly coal.

5. Agglomerates according to any of claims 1-4, wherein the asphaltenic compound is the product resulting from the treatment with a paraffinic solvent of the residue obtained by distilling crude pertroleum at atmospheric or sub-atmospheric pressure

6. Agglomerates according to any of claims 1-5, wherein the asphaltenic compound contains from 30% to 100% by weight of alsphaltene and has a penetration lower than 10 ddm.

7. Agglomerates according to claim 6, wherein the asphaltenic compound has a penetration of 0 ddm.

8. Agglomerates according to any of claims 1-7, wherein the asphaltenic compound has a softening point in the range of 90" to 1 500C.

9. Agglomerate according to claim 1, wherein the combustible material is coal having a particle size which does not exceed 5 mm and the asphaltenic compound has a softening point comprised between 90" and 11 5 C, the amount of asphaltenic compound being comprised between 4 and 6%, based on the weight of agglomerate.

10. Process for manufacturing the agglomerates of claims 1-9, which consists in mixing and coating a finely divided solid combustible material with an asphaltenic compound and then pressing the obtained mixture into a mold to produce briquettes which have the desired shape and may be used directly as combustible without prior desmoking treatment.

11. Process according to claim 10, wherein the asphaltenic compound is used in an amount comprised between 2.5% and 50%, based on the total weight of agglomerate.

12. Process according to claim 11, wherein the asphaltenic compound is used in an amount comprised between 2.5% and 15%, namely between 3% and 10%, based on the total weight of agglomerate.

13. Process according to any of claims 10-12, wherein coal is used as solid combustible.

14. Process according to any of claims 10-13, wherein the asphaltenic compound contains from 30 to 100% by weight of asphaltene and has a penetration lower than 10 ddm.

15. Process according to claim 14, wherein the penetration of the asphaltenic compound is0.

16. Process according to claim 10, wherein the asphaltenic compound has a softening point comprised between 90" and 1 500C.

17. Process according to claim 10, wherein coal having a particle size which does not exceed 5 mm is mixed and coated with an asphaltenic compound having a softening point comprised between 90"C and 11 5 C, the amount of asphaltenic compound in the mixture being comprised between 4% and 6%, and the mixture is pressed into briquettes.

18. Agglomerates and briquettes manufactured bythe process according to any of claims 10-17.