FI77260B - KOKSBRIKETTER. - Google Patents

Description

77260

briquettes

Koksbriketter

In the production and processing of coke, small pieces and crushed coal are always formed, which small fractions are less in demand than larger coke pieces. Small fractions have therefore become a problem due to the fact that they easily produce surplus situations and the price of al-5 odor.

For this reason, there has long been an interest in finding use for these small fractions. One of the proposed methods in this case has been the briquetting of small fractions, in which case the briquettes thus prepared are then used in the same way as large-sized coke.

The same problem as for coke has also occurred when it comes to coal, and when we talk about coke in the following, this term also means coal and charcoal.

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A number of prior patents deal with methods for making coke briquettes and compositions of such briquettes. When preparing coke briquettes, a fine coke material is mixed with some kind of binder, e.g. cement or cement mixtures, bituminous products, lime, sulphite-20 or sulphate-containing organic binders.

Certain binders, such as cement or cement mixtures, have been found to be unsuitable because they do not burn because the briquette as a whole receives poor heat exchange with respect to weight or because the briquette is considered to be difficult to burn. Other binders, such as bitumen products and organic binders, release unhealthy gases or harmful by-products when burned. Most binders also produce fairly large amounts of ash and waste products.

30 It is also common ground that the cost of the binder and the briquetting process must be relatively small, since the usability of the briquettes decreases with their price. As soon as the cost of producing briquettes, including binder, starts to send the price difference between small fractions and coarse fractions of the same fuel, the consumer will buy coarse coke or coarse coal before more or less untested briquettes. The cost of manufacturing briquettes has certainly been the reason why many briquette patents have never been used on a large scale.

Another problem that is also taken into account in certain of said prior patents is that the briquettes can break due to heat 10 and pressure, and in other words have poor "refractory" or heat resistance. Much of the coke consumption takes place in shaft furnaces. In this case, the low fire resistance of the briquettes can become a critical problem, as the briquettes down in the kiln begin to be exposed to high temperatures while being subjected to compression from the column above the material 15 to be heated or melted, e.g. Briquettes with low fire resistance then crumble and close the gap, which causes problems that are completely obvious to a person skilled in the art. In addition to this, the large fuel surface is exposed to upward warming flue gases, which causes a very strong reduction of the carbon dioxide in the flue gases, and the process produces large fuel losses. This is probably the reason why briquettes have not hitherto been commonly used in shaft kilns.

According to a previously patented method, coal pitch is used as a binder for coke particles. The pitch is coking after briquette formation. Such briquettes have proven to be very interesting for certain purposes, but they require strikingly high prices due to the expensive manufacturing process, and these bri-30 chains are therefore not interesting except for potentially specific uses.

It is an object of the present invention to solve the problems associated with previously known briquettes and to provide a briquette which can be produced at a reasonable cost while having sufficient fire resistance to be used in shaft kilns. The invention has arisen from the development of coke briquettes, in particular for shaft furnaces, for smelting mineral 77260 from mineral wool production, but this use is clearly no more different from other uses than it can be predicted that the briquette according to the invention is also suitable for such other uses.

According to the invention, the briquette consists of at least three components: the first component consists of particles of coke or carbon or both, the second component consists of a hydraulic binder, preferably cement. It is already known to use both components together in a similar context. As a third and characteristic component of the invention, the briquette also contains a fine-grained, oxide, mineral component, e.g. rock flour.

The mode of action of the invention is probably that the cement together with the fine-grained, oxidic, mineral component forms a matrix which surrounds and binds together the coke or carbon particles. This matrix can be formed by a suitable selection of ingredients so that it becomes strong enough to be used in both cold and warm conditions.

Briquette gains more strength if the finest coke-20 or carbon particles are avoided, e.g., by screening out such particles. The desired result is already achieved if only those particles that are less than 2 mm are screened out. However, a substantially better result is obtained if coke and carbon particles less than 5 mm are removed, at least for the most part. The upper size limit for coke or carbon particles is mainly a matter of practice 25. A suitable limit is 25 mm. Particles larger than 25 mm have a completely satisfactory sales value and it is therefore not advisable to include such particles in briquettes.

The fine-grained, oxalic, mineral material should preferably not be rougher than 2 mm.

Of course, the strength of the briquettes increases within certain limits as the cement content increases. It has been found that the cement content must be at least 7% of the dry weight of the briquettes. The upward limit is more economical than technical quality, but above a certain limit, which can be set at about 35%, the strength of the briquette no longer increases to such an extent that it would still make sense to further increase the cement content.

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Depending on the type of fine-grained, oxide, mineral material used, certain limits can also be determined. Experience and extensive experiments have shown that practically useful briquettes can rarely be obtained with a fine-grained, oxidic, mineral-5 material content of less than 15%, calculated on the dry weight of the briquette.

It is self-evident that a material is chosen as the fine-grained, oxidic, mineral component which does not otherwise damage the process but which, on the contrary, is advantageous to the process. In the case of mineral wool production, for example, it is generally desired to add limestone or dolomite to the base material, which is usually of the basalt type. Slag, e.g. steel slag, preferably alkaline steel slag may also be selected. It is also possible to add to the fine granule, oxide, mineral component or in addition more special types of ingredients, e.g. oxides, which make the melt or slag easier to drain.

Waste is always generated in the production of mineral wool. Some of this waste-20 is fibrous and poses a waste problem due to its bulky nature. However, this waste has the necessary fine-grained property and the fibers of the waste have a reinforcing effect on the briquettes. Thus, if fibrous mineral wool waste is added to the fine-grained, oxidic, mineral material of the briquette, at least in part, considerable advantages can be obtained both in terms of the strength of the briquettes and the problem of getting rid of the waste.

Surprisingly, it has been found that the additive which is added to the melt in the production of mineral wool with the oxide constituents of the briquettes is clearly more homogeneous and distributed more rapidly in the final product than if they had been added separately. This is probably due to the fact that the coke particles or the carbon particles, respectively, leave pores on combustion which make the reaction surface very large. For this reason, it is suitable to add a relatively large proportion of these mineral wool additives with briquette-35 tea, which of course then penetrates back into the coke or resp.

the share of carbon sequestration. However, the proportion of coke or carbon particles must not be less than 30% of the dry weight of the briquettes.

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Another important advantage can be obtained with the briquettes according to the invention. The fact of the matter is that the exhaust gases from coke-fired shaft furnaces regularly contain sulfur, which produces a strong and unpleasant odor. This can be eliminated by combustion, with the carbon monoxide present in the exhaust gases forming the main fuel. However, carbon monoxide usually needs to be supplemented with some other fuel, such as gas or oil. Now that the briquettes are made with a body made of coke or coal particles, the exhaust gases are enriched with volatile substances derived from coke or coal so that no additional fuel is required. Not less than 10 Z

the coke / coal mixture must consist of carbon particles so that an apparent effect is observed. If it turns out that more than 50% of the carbon particles would be needed, it is better to use both coal briquettes and coke briquettes or possibly carbon briquettes alone at the same time.

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In the following, the invention is illustrated by a few examples. During the development work, it has been proved that briquettes with a compressive strength of 2 less than 2943 kPa (30 kp / cm) are not strong enough to withstand weighing and loading into the furnace. Thermal strength is determined after heating the briquettes to 900 ° C within one hour. Development work has shown that briquettes with a thermal strength of less than 981 kPa (10 kp / cm) after such heat treatment have little chance of functioning properly.

25 Example 1

The mixer mixes coke, piece size 2-25 mm 810 kg (60 Z) 30 Portland cement 175 kg (13 Z) sand 365 kg (17 Z) total 1350 kg

The briquetting takes place in a concrete product molding machine, whereby the briquettes 35 are formed into cubes with an edge length of about 8 cm. The wet cubes were stored for 12 days, after which they were dried for one day at 60 ° C.

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The compressive strength of the briquettes in the cold state was measured to be 2639 kPa 2 (26.9 kp / cm), which value was the average of six briquettes.

In order to measure the thermal strength of the briquettes, they were subjected to 5,900 ° C for one hour, after which they were allowed to cool for 24 hours before the thermal strength was measured, giving a value of 2246 kPa (22.9 kp / cm), which was six briquettes. average.

Briquettes of the same composition have a compressive strength in cold 2 slightly below the indicated value of about 2943 kPa (30 kp / cm) while the thermal strength is well above the given reference value of 981 kPa 2 (10 kp / cm).

The following Tables A and B further provide a number of examples of different blends for making briquettes and provide composition, compressive strength, thermal strength, strength evaluation, and notes.

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TABLE A

Eg Coke Portland cement Aggregate 5 _____ r— kg% kg% kg% species 2 I 810 60 175 13 365 27 Lime flour | 10 3 j 810 60 175 13 135 10 slag j | 230 17 sand 2 mm j 4! 1080 80 270 i 20 - - - j 5 868 65 175 j 13 297 22 sand 2 mm 6! 945 70 108 I 8 243 18 Fly ash and l 15: | 54 4 lime flour; ! | 7 j 945 70 108 j 10> 135 10 slag ! | I 135 10 | SiO '; ! ! ; ! /

8 | 945 70 i 68 i 5 1 270 20 i lime flour I

! 1 and 67 5 | slag! I; ! j 20 9 · 945 70 162 j 12 \ 243; 18 | Rockwool- j ί | ! ! 1 sawdust flour j 10 | 945 70 ί 135 \ 10 \ 135 S 10 'lime flour j i! I! ί j t | 135 J 10! Si0o! : f 1 \ 11: 675 I 50 I 310! 23 365 S 27 sand 2 mm

1} '! (I

25 12} 1080 I 80 175 [13 95 | 7 slag * I i: 13 743 j 55 135 i 10 202] 15 lime flour ί 270> 20 slag; 's * i; 14 j 405! 30 j 472 i 35) 473 35 sand 2 mm 15 ί 945! 70 | 135 10! 68 Ϊ 5 kuona i ί i 30 ί; j i 202 j 15 Rockwool- I | ; I ί | poiste ** il; j_i I__ *) wastes from wet separation of mineral wool 8 77260

TABLE B

Eg compression- heat- compression- & Note.

5 strength strength thermal strength_ kPa kPa approved not approved 2 2551 1148 x coke 2-25 mm 10 3 3895 3345 x coke 2-25 mm ί j 4 3188 j 421 x coke 2-25 mm j

ί 5 2207 I 765 x coke 0-25 mm J

I! ί 6 2963! 1030 x coke 2-25 mm i ί?

15 I! I

li *) S

7 3404 I 892 x 'coke 2-25 mm I i *) j with doubt, j 892 near ί! limit value t ί 20 j 8 j 2502 334 x j coke 2-25 mm I 9 j 1050 451 x; coke 2-25 mm s I i! ! 10 j 3092 1334 x coke 2-25 mm 25 j! 11 1481 1109 x coke 2-25 mm f »12 2384 441 x coke 2-25 mm; | 13 1246 912 x coke 2-25 mm f ί 30! 14 3326 2011 x coke 2-25 mm, i too expensive | j relative to low; to a coke content of i i 35; 15 2972 1001 x J coke 2-25 mm 1 _____I_! 9 77260 2

The measured compressive strength is slightly below the recommended value of 2943 kPa (30 kp / cm) in Examples 1, 2, 5, 8 and 12. As for Examples 9, 11 and 13, the compressive strength clearly gives a reputable value. Examples with accepted compressive strength values are Examples 3, 4, 6, 7, 5, 10, 14 and 15.

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As for the thermal strength, which must be at least 981 kPa (10 kp / cm), we have obtained the acceptable values for this in Examples 1, 2, 3, 6, 10, 11, 14 and 15, while the thermal strength is in Examples 4, 5, 8, 9, 12 and 13 10 slightly below the accepted value. Examples 7 and 13 have a thermal strength between 883 and 981, and this must be considered an acceptable value because a certain margin of error is present.

The examples in which we obtained both the approved compressive strength in the cold t-15 and the approved thermal strength are Examples 3, 6, 10, 14 and 15 and, with certain doubts, also Example 7. Thus, the composition of the briquettes should be within the following values:

coke (or coal / coke mixture) 30 - 75 Z

20 cement 8 - 35 Z

filler 15 - 35 Z.

Claims (5)

77260 A briquette, preferably intended as an additional fuel in shaft furnaces for melting a mineral in mineral wool production, comprising particles of coke or carbon or both and a hydraulic binder, such as cement, characterized in that the hydraulic binder is present in a concentration of at least 8%, coke and / or carbon is present in a concentration of 30-75% of the dry weight of the briquette, so that the fine particles in the coal and / or coke have been removed as far as possible and replaced by a fine-grained, oxidic, mineral material such as sand, slag, stone flour , fly ash, limestone flour, Dolo mite flour, silica, sawdust or other wastes from mineral wool production, 20 that the coke and / or carbon particles are mainly greater than 2 mm or preferably greater than 5 mm. 1 Claims Briquette according to Claim 1, characterized in that the coke and / or carbon particles form a mixture of coke and carbon, the proportion of carbon being 10 to 50%. Briquette according to Claim 1 or 2, characterized in that the binder consists of cement and is at least 8-35% by dry weight of the briquette. 30 Briquette according to one of Claims 1 to 3, characterized in that the fine-grained, oxidic, mineral component has a grain size of less than 2 mm. Briquette according to one of Claims 1 to 4, characterized in that the fine-grained, oxide, mineral component is present in an amount of at least 15 to 35 X of the dry weight of the briquette.