GB1591198A - Component for coking mixtures - Google Patents

Description

(54) COMPONENT FOR COKING MIXTURES (71) We, SUMITOMO METAL INDUSTRIES LIMITED, a Japanese Corporation of 15, 5-chome, Kitahama, Higashi-ku, Osaka City, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the production of a composition for forming coke suitable for shaft furnaces, and particularly relates to the use of carbonaceous substances which hitherto have been unsuitable for the production of such cokes. The invention also relates to coke obtained by the use of such coke forming composition.

Such coke is obtained by coking a coking coal, for instance by first forming a briquette of such coking coal with a binder, carbonizing the briquette and coking the carbonized briquette in a coke oven. High quality coking coal is however increasingly difficult to obtain; Coke suitable for shaft furnaces is usually of granular size of more than 25 mm. Powdered coke is unsuitable as a raw material for the use of coke for such purposes.

A method of utilizing coal by gasification is under current examination. However it is so difficult to gasify coal completely so that in most instances a char i.e. a product obtained by heating non-caking coal, is produced as a residue. Such a coal gasification char is also unsuitable for use as a raw material for cokes, and is in fact used as fuel.

The reason why powdered coke and coal gasification char are not utilized as raw materials for the production of coke for shaft furnaces is largely because they have no effective melting point and thus do not react with the molten components in the coking coal with which they are mixed to form coke, and also because they are porous and are therefore not susceptible to being coated with the molten components in the coking coal. Thus coke produced from such raw materials tends to have insufficient strength.

The present invention is directed to the use of carbonaceous substances which have not hitherto been used as a component of coke for shaft furnaces, namely powdered coke, coal gasification char, coal liquefaction residue coal, petroleum coke and semi-dry-distilled char, by mixing with an aromatic pitch.

The invention provides a process for providing a composition for forming after briquetting and subsequent carbonizing a coke suitable for shaft furnaces, comprising mixing and heating at least one finely crushed carbonaceous substance selected from coke, coal gasification char, coal liquefaction residue coal, petroleum coke and semi-dry-distilled char, with at least one aromatic pitch, the said heating step being effected at a temperature above the melting point of the said aromatic pitch, whereby the said carbonaceous substance becomes impregnated with the said aromatic pitch, and adding a caking coal to the impregnated material thus obtained to form a mixture thereof.

The said aromatic pitch may be a coal tar, coal tar pitch, or pitch obtained by heat-treating or solvent-extracting an asphalt.

Preferably the said carbonaceous substance is crushed to an average granularity of less than 1 mm, particularly less than 0.5 mm.

The said carbonaceous substance may with advantage be impregnated with the aromatic pitch which has a hydrogen/carbon ratio of less than 1.0.

In particular the process of the invention is one wherein from 50 to 95 parts of the said carbonaceous substance having an average granularity of from 0.25 to 0.5 mm. are impregnated with from 5 to 50 parts of the said aromatic pitch.

In carrying out the process of the invention the inert carbonaceous substance is finely crushed to form a powder thus increasing the surface area thereof so as to increase the rate of impregnation into the internal pores thereof by the aromatic pitch.

To ensure that the powdered material is effectively impregnated with the aromatic pitch, it is necessary that the pitch should have a sufficient fluidity and thus an essential feature of the invention is that the mixing is effected at a temperature above the melting temperature of the pitch. If in carrying out the method of the invention the powdered carbonaceous substance and aromatic pitch are mixed under pressure, the rate of impregnation will be increased.

By the practice of the present invention the meltability required by the coke component will be provided and the coating effect by the molten component with other components e.g.

coking coal, will be improved.

The accompanying drawing provides a schematic illustration of the steps of the method of the present invention. In the drawing 1 indicates a hopper for storing the powdered carbonaceous substance, 2 indicates a crusher for crushing the said carbonaceous substance from hopper 1, 3 indicates a heating tank for heating the aromatic pitch, 4 indicates a heater-mixer for mixing and heating the mixture of powdered carbonaceous substance and aromatic pitch.

The coking component thus formed is thereafter passed along line a to the mixer 5 wherein it is mixed with a mixing raw material for a coke e.g. a caking coal, to provide raw material according to the invention for the formation of a coke suitable for shaft furnaces.

The invention is hereinafter particularly described by the following Examples which include comparative Examples.

Example 1 3 samples of a component for forming coke were each made from 70 parts of a powdered coke unsuitable for a coke for shaft furnaces, finely crushed to an average granularity of 0.5 mm. with the fine crusher 2 of apparatus in the drawing previously referred to, and 30 parts of a coal tar series soft pitch of hydrogen/carbon atomic ratio of 0.58 and melting temperature of 53"C. and which were mixed for 5 minutes at temperatures of 30 , 50 and 60"C.

respectively in the heating mixer 4. The mixed products thereby obtained were then each mixed with 30% of a caking coal derived from 3 separate caking coals as set forth in Table 1.

The compositions were then carbonized in a test coke oven. The strength of the cokes thereby obtained was then measured and compared with a coke derived wholly from the coal composition of Table 1 and the results are set forth in Table 2.

Table 1 Industrial analysis Button Mixing values (in No) index proportions (C.S.N.) (Wt.%) Ash Volatile Fixed matter carbon U.S. strong 6.2 17.6 74.9 8 25 caking coal Medium strength 7.2 25.1 65.8 7 1/2 55 caking coal Weak caking 8.3 36.6 51.9 5 20 coal Table 2 Test No. 1 2 3 4 Caking coal 100 70 70 70 Mixing 30"C. heated mixture 30 proportions 50"C. heated mixture 30 (wit.%) 60"C. heated mixture 30 DI 30 93.2 76.3 83.4 93.3 Coke drum 50 strength DI 150 82.3 54.7 73.6 82.5 15 Table 2 indicates that when compared with the drum strength of the coke of Test No. 1 in which the coke was made only from the basic caking coal, the coke drum strengths of Test Nos. 2 and 3 in which the mixed products mixed at heating temperatures of 30 and 50"C.

with 30% of the coal used, were too low to be used as a coke for shaft furnaces. However the coke of Test No. 4 prepared by mixing a component with 70% of basic coal, the said component obtained at a heating/mixing temperature of 60"C. is not inferior to coke derived wholly from basic coal, and is of high quality.

Example 2 Table 3 shows the coke strengths of cokes formed from mixtures of the caking coal of Table 1 and powdered coke (Tests 5,6 and 7) and formed from mixtures of the said caking coal and various amounts of the 60"C. heated mixtures of Example 1, i.e. the mixture heated tb produce the coking component used according to the invention.

Table 3 Test No. 5 6 7 8 9 10 11 Caking coal 98 96 94 90 80 70 60 Proportion Powdered coke 2 4 6 (wt. O/o) 60 C. heated 10 20 30 40 mixture (7) (14) (21) (28) DI 30 92.6 87.3 78.2 94.2 93.7 93.3 92.1 Coke drum 15 strength DI 150 80.3 73.5 60.6 83.1 82.7 82.5 80.6 15 The numeral in parentheses shown below the proportion of the 60"C. heated mixture is the proportion in the coking component occupied by powdered coke based on the total raw material used for forming the final coke.

Table 3 shows that when the powdered coke was simply mixed in the basic coal, as in Tests 5, 6 and 7, with increase of the mixing rate, the coke strength was reduced, but in the case of the 60"C. heated mixture of the present invention, as in Tests 8, 9 and 10, when the mixing amount was small, the coke strength was little influenced and the coke quality was high.

However as in Test No. 11 when the mixing amount was higher than 40%, the coke strength tended somewhat to become reduced. This is considered to be due to the fact that the powdered coke was so high that only about 20% of the 28% could successfully be impregnated with the aromatic pitch.

Example 3 Cokes were formed from 70 parts of a coal gasification char of 6.5% volatile matter by-produced from a coal gasification process and 30 parts of a gasification pitch of a hydrogen/carbon atomic ratio of 0.67 and melting temperature of 68"C. obtained as a by-product from a coal gasification process. The components were mixed for 5 minutes at a temperature of 80"C. in a heating mixer, and the mixed product obtained was mixed with a caking coal of composition shown in Table 4 to make a moulded coke (briquette). The coke strengths are shown in Table 5, which also shows the strength of a coke obtained when the coal gasification char was simply mixed with the caking coal, and a coke obtained from caking coal alone.

Table 4 Ash Volatile Button Proportion (in %) matter index (into) (in O/o) (CSN) Soviet Union-produced 8.1 14.0 1 50 slightly caking coal Australia-produced 9.3 29.6 Not 15 non-caking coal caked Vietnam-produced 7.6 8.7 Not 10 non-caking coal caked Canada-produced 9.0 26.7 6 15 quasi-strong caking coal U.S.-produced oil 0.5 10.9 Not 10 coke caked Table5 Test No. 12 13 14 15 16 17 18 Caking coal 90 85 80 75 40 20 Coalgasifi- 5 10 15 cation char Propor- 80"C. heated 50 70 90 tion mixture (35) (49) (63) (Wt,"ro) Coal tar 7 7 7 .7 7 7 7 pitch Tar 3 3 3 3 3 3 3 Coke DI 30 96.3 96.0 92.3 88.3 96.9 96.5 93.7 Drum 15 Strength DI 150 84.7 84.2 79.6 72.4 85.2 84.6 81.4 15 The numeral in parentheses shown below the proportion of 80"C. heated mixture is the proportion occupied by the coal gasification char based on the total raw material used for the final coke.

As shown in Table 5, in the case when the coal gasification char was simply mixed in the basic caking coal, as in Tests, 13,14 and 15, the coke strength becomes reduced with increase of the proportion of char used, i.e. it is only in the case of 5 % coal gasification char of Test 13 that there was obtained almost the same strength as Test 12 in which a formed coke was made from the basic caking coal. However in the case of a formed coke made by mixing the 80"C.

heated mixture according to the present invention, as in Tests 16, 17 and 18, the strength of the formed coke is slightly reduced only in Test 18 in which the basic coking coal was not present, and favourable coke strengths as high or higher than of the basic formed coke are obtained in Tests 16 and 17.

Table 7 indicates that, as compared with the drum strength of the coke of Test 19 in which the coke was made only from the basic caking coal, the coke drum strenghts of Tests 20 and 25 in which the mixed products A and F having 3% and 70% of the mixed amount of soft pitch shown in Table 6 were mixed are so low that the cokes of Tests 20 and 25 are not of a quality which can be used as of a coke for shaft furnaces. However the cokes of Tests 21, 22,23 and 24 prepared by mixing the mixtures B, C, D and E in which the mixing amount of soft pitch shown in Table 6 was 5 to 50%, are not inferior in the strength to the coke prepared from the basic coal and are of a high quality.This is due to the porosity of the powdered coke being normally 45 to 55 %, when the impregnation of soft pitch into the pores of the powdered coke is less than 10% in respect of such porosity as in the case of the mixture A, the effect of the present invention is not exhibited and when the soft pitch, the amount of which is twice as much as the porosity, is mixed as in the .case of the mixture F, the effect of the present invention is lowered. The above mentioned tendency can also be seen with the coal gasification char given in Example 3. Therefore a favourable mixing rate is in the range of 95 to 50% of inert carbonaceous substance and 5 to 50% of aromatic pitch.

Table6 Mixture A B C D E F Powdered coke 97 95 70 60 50 40 Soft pitch 3 5 30 40 50 60 Table 7 Test No. 19 20 21 22 23 24 25 Basic coal 100 70 70 70 70 70 70 Mixture A 30 Mixture B 30 Mixture C 30 Proportion in Mixture D 30 Wt.% Mixture E 30 Mixture F 30 Coke DI 30 93.2 88.7 92.0 93.3 93.8 92.8 89.2 drum 15 strength DI 150 82.3 70.4 80.6 82.5 82.7 81.0 77.6 15 As evident from the above explanation, even if the raw material mixture in the case of the present invention is mixed with the basic coal, a favourable coke strength as high as or higher than of the basic coal will be obtained.

WHAT WE CLAIM IS: 1. A process for providing a composition for forming after briquetting and subsequent carbonizing a coke suitable for shaft furnaces, comprising mixing and heating at'least one finely crushed carbonaceous substance selected from coke, coal gasification char, coal liquefaction residue coal, petroleum coke and semi-dry-distilled char, with at least one aromatic pitch, the said heating step being effected at a temperature above the melting point of the said aromatic pitch, whereby the said carbonaceous substance becomes impregnated with the said aromatic pitch, and adding a caking coal to the impregnated material thus obtained to form a mixture thereof.

2. A process according to Claim 1, wherein the said aromatic pitch may be a coal tar, coal tar pitch, or pitch obtained by heat-treating or solvent extracting an asphalt.

3. A process according to Claim 1 or Claim 2, wherein the said carbonaceous substance is crushed to an average granularity of less than'1 mm.

4. A process according to Claim 3, wherein the said carbonaceous substance is crushed to an average granularity of less than 0.5 mm.

5. A process according to any of Claims 1 to 4, wherein the said carbonaceous substance is impregnated with an aromatic pitch having a hydrogen/carbon atomic ratio of less than 1.0.

6. A process according to any of Claims 1 to 5, wherein from 50 to 95 parts of the said carbonaceous substance having an average granularity of from 0.25 to 0.5 mm are impregnated with from 5.to 50 parts of the said aromatic pitch.

7. A process according to Claim 1, substantially as hereinbefore described.

8. A composition for coking mixtures obtained by a process according to any of Claims 1 to7.

9. A coke obtained by briquetting a composition as claimed in Claim 8 and carbonizing the briquettes to form a coke.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. normally 45 to 55 %, when the impregnation of soft pitch into the pores of the powdered coke is less than 10% in respect of such porosity as in the case of the mixture A, the effect of the present invention is not exhibited and when the soft pitch, the amount of which is twice as much as the porosity, is mixed as in the .case of the mixture F, the effect of the present invention is lowered. The above mentioned tendency can also be seen with the coal gasification char given in Example 3. Therefore a favourable mixing rate is in the range of 95 to 50% of inert carbonaceous substance and 5 to 50% of aromatic pitch. Table6 Mixture A B C D E F Powdered coke 97 95 70 60 50 40 Soft pitch 3 5 30 40 50 60 Table 7 Test No. 19 20 21 22 23 24 25 Basic coal 100 70 70 70 70 70 70 Mixture A 30 Mixture B 30 Mixture C 30 Proportion in Mixture D 30 Wt.% Mixture E 30 Mixture F 30 Coke DI 30 93.2 88.7 92.0 93.3 93.8 92.8 89.2 drum 15 strength DI 150 82.3 70.4 80.6 82.5 82.7 81.0 77.6 15 As evident from the above explanation, even if the raw material mixture in the case of the present invention is mixed with the basic coal, a favourable coke strength as high as or higher than of the basic coal will be obtained. WHAT WE CLAIM IS:

1. A process for providing a composition for forming after briquetting and subsequent carbonizing a coke suitable for shaft furnaces, comprising mixing and heating at'least one finely crushed carbonaceous substance selected from coke, coal gasification char, coal liquefaction residue coal, petroleum coke and semi-dry-distilled char, with at least one aromatic pitch, the said heating step being effected at a temperature above the melting point of the said aromatic pitch, whereby the said carbonaceous substance becomes impregnated with the said aromatic pitch, and adding a caking coal to the impregnated material thus obtained to form a mixture thereof.

2. A process according to Claim 1, wherein the said aromatic pitch may be a coal tar, coal tar pitch, or pitch obtained by heat-treating or solvent extracting an asphalt.

3. A process according to Claim 1 or Claim 2, wherein the said carbonaceous substance is crushed to an average granularity of less than'1 mm.

4. A process according to Claim 3, wherein the said carbonaceous substance is crushed to an average granularity of less than 0.5 mm.

5. A process according to any of Claims 1 to 4, wherein the said carbonaceous substance is impregnated with an aromatic pitch having a hydrogen/carbon atomic ratio of less than 1.0.

6. A process according to any of Claims 1 to 5, wherein from 50 to 95 parts of the said carbonaceous substance having an average granularity of from 0.25 to 0.5 mm are impregnated with from 5.to 50 parts of the said aromatic pitch.

7. A process according to Claim 1, substantially as hereinbefore described.

8. A composition for coking mixtures obtained by a process according to any of Claims 1 to7.

9. A coke obtained by briquetting a composition as claimed in Claim 8 and carbonizing the briquettes to form a coke.