Patent Publication Number: US-4318779-A

Title: Method of manufacture of blast furnace cokes containing substantial amounts of low grade coals

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention: 
     The present invention is directed to a method of manufacturing an effective blast furnace coke, and more particularly to a method of manufacturing an effective blast furnace coke which contains a substantial amount of low grade coal. 
     2. Description of the Prior Art: 
     It is well known that blast furnaces, and especially large sized blast furnaces, require high quality cokes to sustain their operation. At the same time, however, due to the current global shortage of good quality coals, the price of effective blast furnace cokes has gone up. In order to compensate, the coke industry has developed a number of manufacturing processes for the production of blast furnace cokes which can utilize low grade coals, e.g., non-coking coals or poorly coking coals (these being the coals which account for most of the available coals and are the cheapest in cost, but which heretofore have not been considered suitable for use as raw material coals for the manufacture of blast furnace cokes). However, none of these processes have been found to be totally acceptable. 
     For example, the following manufacturing processes have been developed which make use of low grade coals: a preheated coal charging process (coaltek system or precarbon system) wherein some or all of either a coking coal or a blended coal, which consists of a coking coal and a low grade coal, is preheated at temperatures of from 200° C. to 350° C. and then charged into the coke oven (see Japanese Patent Publication No. 23495/46, published on July 5, 1971); a partial briquette charging process wherein briquettes containing low grade coal are added to a blended coal to be charged into the coke oven (see Japanese Patent Publication No. 7375/46, published on Feb. 24, 1971); a caking substance adding process wherein a charging coal is prepared by adding artifical coking coal or a caking substance to blended coal (see JA-OS 85803/53, laid open for public inspection on July 28, 1978); and a selective pulverization process wherein a coking coal of a kind which has its coking property segregated according to its grain size distribution is pulverized by use of a sieve (see Japanese Patent Publication No. 45763/49, published on Dec. 6, 1974 and Japanese Patent Publication No. 19321/53, published on June 20, 1978). 
     The above noted preheated coal charging process is believed to provide enhanced strength to the produced coke because the bulk density of the coal charged into the coke oven is increased and the spaces between adjacent coal particles are decreased, and also because the 100° C. zone is totally absent or short during the vaporization of the moisture, the heating rate in the plastic zone is lowered, the thickness of the plastic layer is expanded, and the possibility of adjacent coal particles coalescing is enhanced. Although the blending ratio of the low grade coal is variable with the particular kind of coal being used, it is thought to have a limit of 20% by weight (hereinafter indicated simply in %). 
     In the case of the above-noted partial briquette charging process, various views have been advanced as to the mechanism which leads to the manifestation of its effect. A typical theory is that expansion of the briquettes in the coking process causes compaction of the coal surrounding the briquettes, which results in an improvement in the coking property. When the blending ratio of briquettes is 60%, incidentally, the bulk density of the coal charged in the coke oven reaches its peak and the stength of the produced coke is improved to the greatest extent. In the operation of this system on a commercial scale, however, the segregation which occurs in the briquettes in the coke oven results in difficulties in discharging the produced coke from the coke oven. Thus, the blending ratio of briquettes is said to be generally limited to about 30%. The proportion of low grade coal which can be blended in total amount of the charging coal is about 20%, though it is variable with the type of low grade coal which is used. 
     The above-noted caking substance adding process aims to overcome the fluidity problems and improve the quality of the produced coke by the addition of a caking substance. The quality of the caking substance, therefore, is important. Since the caking substance is generally higher in cost than the coal, the proportion of the caking substance economically desirable for addition to the charging coal is generally limited to about 10%. For this reason, the blending ratio of low grade coal is said to be about 20%. 
     The above-noted selective pulverization process aims to improve the coking property of the charging coal by pulverizing coking coal of a kind which has its coking property segregated according to its grain size distribution, screening the pulverized particles through a sieve 3 to 6 mm in mesh size and pulverizing again the course particles retained on the sieve, whereby the inert particles which reduce the coking property and are concentrically present in the coarse-particle zone will be uniformly distributed throughout the charging coal. 
     With any of the processes described above, however, the highest possible blending ratio for the low grade coal in the charging coal is about 20%. Thus, the need of developing a method capable of producing a blast furnace coke containing low grade coal in an increased blending ratio has become pressing. Research and developments, thereto, are being promoted on this subject from various angles. 
     It is, therefore, an object of this invention to provide a method for the manufacture of blast furnace coke by blending low grade coal with coking coal in a high blending ratio. 
     Another object of the present invention is to provide a method for the manufacture of blast furnace coke by the operation of the partial briquette charging system without necessitating any special means for the prevention of segregation. 
     SUMMARY OF THE INVENTION 
     According to the present invention, which combines the partial briquette charging system with the requirement that the total moisture content of the blended coal be lowered to at or below 4%, as the segregation of briquettes in the coke oven is decreased, the blending ratio of briquettes can be increased to 40% in an actual commercial operation without necessitating any special means for preventing the segregation. In addition, the effect of the addition of the caking substance in the briquettes can be promoted and the blending ratio of low grade coal can be notably increased, i.e., by keeping the total moisture content in the briquettes at 4% or below. 
     Further, this invention allows the blending ratio of the low grade coal to be increased to a still higher level by a procedure which comprises pulverizing coking coal of a kind which has its coking property segregated according to its grain size distribution (such as Australia and Canada origin), mixing the fine particles which have passed the sieve with the other coking coal, blending not less than 65% of the resultant mixture with not more than 35% of low grade coal to produce a blended coal, treating the blended coal so as to keep the total moisture content thereof at or below 4%, separately preparing briquettes comprising not less than 10% of coking coal, not more than 90% of low grade coal and a binder and/or caking substance, blending not less than 60% of the aforementioned blended coal with not more than 40% of the briquettes and thereafter carbonizing the resultant blend. The effect of this invention is additionally improved when the briquettes have their total moisture content adjusted to a level of not more than 4% and when the coarse particles retained on the sieve after pulverizing of coking coal of a kind which has its coking property segregated according to its grain size distribution are again pulverized and used as a substitute for the coking coal in the blended coal or the coking coal in the briquettes. 
     Other objects, characteristics and advantages of this invention will become apparent from the further disclosure of invention found herein below and considered in conjunction with the accompanying drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic diagram of the test apparatus used in Example 2 of the specification and 
     FIG. 2 is a graph showing the relationship between the total moisture content of the briquettes and the coke strength as discussed in Example 3. 
    
    
     DETAILED DESCRIPTION OF THE INVENTIVE EMBODIMENTS 
     In the following description of this invention, the terms indicated below will be used as defined correspondingly. 
     By &#34;coking coal&#34; is meant strongly coking coal to weakly coking coal. 
     By &#34;low grade coal&#34; is meant non-coking coal or poorly coking coal which has the properties of CSN (FSl) 0-2, flowability index 0-10 D.D.P.M., and total dilation index (Audibert Arnu dilatometer) of 0, and which has heretofore been refused acceptance, i.e., has been considered unsuitable, for use in the manufacture of blast furnace coke. 
     By &#34;blending coal&#34; is meant a coal which includes coking coals or a mixture consisting of desired proportions of coking coal and low grade coal and has been adjusted to have a CSN in the range of 3 to 9 and volatile matter in the range of 25 to 33%. 
     By &#34;charging coal&#34; is meant a coal which has been prepared by solely using blended coal or by mixing blended coal with briquettes or a caking substance and is ready to be charged into a coke oven. 
     By &#34;briquette&#34; is meant a product obtained by blending coking coal and low grade coal in a desired blending ratio, adding a caking substance and/or binder to the resultant blend, kneading the mixture and molding it in a unform shape under a roll press. 
     By &#34;caking substance&#34; is meant an aromatic bituminous substance. For example, coal pitch, asphalt pitch and those pitches which are obtained by heat-treatment or solvent-extraction of coal tar, asphalt, bottom oil remaining after removal of the 230° C. fraction from coal tar (hereinafter referred to as &#34;road tar&#34;), coal pitch, petroleum heavy oil, etc., can be utilized as the caking substance. They may be used in conjunction with solvents such as coal tar, road tar, propane-deasphalting asphalt (PDA), etc. They are invariably capable of improving the coking property and are generally added in a blending ratio of 1 to 30%. 
     The binder is used for the purpose of enabling the briquettes to retain their original shape. Coal pitch, asphalt, road tar, coal tar, etc., can be used as binders and are generally added in a blending ratio of 5 to 15%. 
     The first embodiment of this invention comprises causing a blended coal, prepared by mixing not less than 80% of coking coal with not more than 20% of low grade coal, to be preheated or dried to adjust the total moisture content thereof to at or below 4%, separately preparing briquettes by combining not less than 10% of coking coal, not more than 90% of low grade coal and a binder and/or caking substance, then mixing not more than 40% of the briquettes with not less than 60% of the blended coal having an adjusted total moisture content of not more than 4%, and thereafter carbonizing the resultant blend. 
     In the first embodiment of this invention, the segregation of briquettes occurs less than in the ordinary blended coal (having a total moisture content of 8%), the blending ratio of briquettes can be increased to up to 40%, even when the manufacture is practiced on a commercial scale, and the blending ratio of low grade coal can be substantially increased because the blended coal is adjusted such that its total moisture content is lowered to 4% or below. When the total moisture content of the briquettes is additionally lowered to at or below 4%, the thickness of the plastic layer in the plastic zone is increased similarly to the charging coal involved in the preheated coal charging process, the effect of the addition of caking substance is promoted and the blending ratio of the low grade coal can be increased. Consequently, nearly one half the entire amount of the charging coal can comprise low grade coal. 
     The upper limit to the blending ratio of low grade coal in the blended coal destined to have its total moisture content lowered to or below 4% is fixed at 20%. The reason for this upper limit of 20% is that the coke strength of the blended coal becomes insufficient (note: under special conditions the blending ratio of low grade coal can exceed 20%). 
     The upper limit to the blending ratio of low grade coal in the coal material of the briquettes is fixed at 90%. The reason for this limit is that the coke strength becomes insufficient when the blending ratio of low grade coal exceeds 90%. 
     The upper limit to the total moisture content of the blended coal is fixed at 4%. The reason for this limit is that the coke strength of the blended coal becomes insufficient, the segregation of the briquettes increases, and the blending ratio of briquettes is consequently lowered when the moisture content exceeds 4%. 
     The blending ratio of briquettes can be increased by adjusting the total moisture content of the blended coal as described above. As already described, the blending ratio of low grade coal is further increased when the total moisture content of the briquettes is additionally lowered to at or below 4%. 
     The preparation of briquettes having a total moisture content of not more than 4% may be practiced by first kneading the coal material having its total moisture content suitably adjusted in advance and then forming the coal material into briquettes under a roll press, or by first forming the coal material into briquettes under a roll press and then treating the briquettes to have their total moisture content adjusted. The effect of the adjustment of total moisture content is the same regardless of which of the two methods described above is used. 
     The second embodiment of this invention comprises pulverizing coking coal of a kind which has its coking property segregated according to its grain size distribution, screening the pulverized coal through a sieve, pulverizing further the coarse particles retained on the sieve, then mixing the fine particles collected under the sieve, another coking coal and low grade coal to produce a blended coal and thereafter adjusting the total moisture content of the resultant blend. It may alternatively comprise pulverizing coking coal of a kind which has its coking property segregated according to its grain size distribution, screening the pulverized coal through a sieve, further pulverizing the coarse particles retained on the sieve and using the pulverized particles as a substitute for the coking coal in the briquettes. 
     Specifically, according to the second embodiment of this invention, in the manufacture of blast furnace coke by the carbonization of the charging coal prepared by blending the blended coal with the briquettes, the coking coal of a kind which has its coking property segregated according to its grain size distribution is first pulverized and the pulverized coal is screened through a sieve, the fine particles collected under the sieve are mixed with another coking coal, not less than 65% of the resultant mixture and not more than 35% of low grade coal are combined to form a blended coal, and the blended coal is treated to have its total moisture content lowered to at or below 4%. Separately, briquettes are prepared with not less than 10% of coking coal, not more than 90% of low grade coal and a binder and/or a caking substance. Thereafter, not less than 60% of the aforementioned blended coal and not more than 40% of the briquettes are blended and subjected to carbonization. 
     The preheated coal charging process has the effect of increasing the bulk density of the charging coal in the coke oven, promoting the compaction of the coal particles, and assisting in the action of mutual fusion between the low molecular weight portion and the higher molecular weight portion in the plastic zone. When this process is used in combination with the aforementioned selective pulverization system, a synergistic effect is achieved in that the dispersion of the low molecular weight portion is promoted in the course of preheating because the inert particles which are inhibitory of the coking property and concentrically present in the course particles portion are allowed to be uniformly distributed throughout the blended coal. As a result, the blending ratio of low grade coal can be notably increased. Moreover, since the total moisture content of the blended coal is adjusted to, similarly to that in the first embodiment, at or below 4%, preparatorily to the mixing of the blended coal with the briquettes, the segregation of briquettes in the coke oven is decreased, the blending ratio of the briquettes during the commercial operation of the invention can be increased up to 40% without necessitating any special means for precluding the segregation, and the blending ratio of low grade coal can be increased. 
     Also in the second embodiment, when the total moisture content of the briquettes is additonally adjusted to at or below 4%, the addition which is made as one of the effects of the preheating to the thickness of the plastic layer in the plastic zone furthers the possibility of adjacent coal particles being united and permits the blending ratio of the low grade coal in the briquettes to be proportionately increased. The effect just described when additionally adding the caking substance during the preparation of briquettes is advanced and the blending ratio of low grade coal in the briquettes is further increased. When the coarse particles retained on the sieve are pulverized again and are added into the briquettes, the amount of the fine particles collecting under the sieve is changed and the blending ratio of low grade coal in the blended coal is increased. 
     For the reasons described in detail above, the present invention, which uses a specific combination of steps, permits manufacture of blast furnace coke from a charging coal containing up to 50% of low grade coals. 
     In the second embodiment, the upper limit to the blending ratio of low grade coal in the blended coal is fixed at 35%. The reason for this upper limit is that the coke strength becomes insufficient when the blending ratio of low grade coal exceeds 35%. 
     The reasons for and the effects of fixing the upper limit to the blending ratio of low grade coal in the briquettes at 90%, adjusting the total moisture content of the blended coal at or below 4% and fixing the upper limit to the total moisture content of the briquettes at 4% are the same as those of the first embodiment. 
     Working examples of the present invention will now be given to illustrate the effects of the invention. 
     EXAMPLE 1 
     A blended coal, A, formed solely of coking coal and a low grade coal, B, indicated in Table 1 were blended in varying ratios indicated in Table 2, treated with a fluidized bed 300 mm in diameter to acquire respectively prescribed tool moisture contents, placed in 18-liter tin cans, charged an electric furnace at 800° C. and left to stand therein for four hours, then heated up to 1000° C. at a heating rate of 3.3° C./min., kept at this temperature for three hours, then discharged from the electric furnace, quenched with sprayed water and tested for coke strength in accordance with JIS K-2151-6. (This standard will be invariably used in the tests to be indicated herein below). The results are shown in Table 2. 
     
                       TABLE 1                                                     
______________________________________                                    
Proximate analysis (%)          Particle                                  
                         Fix-             size                            
                 Vola-   ed        F.I.   (Below                          
Mois-            tile    car-      (Log   3 mm)                           
ture      Ash    matter  bon  CSN  DDPM)  (%)                             
______________________________________                                    
Blend-                                                                    
ed    1.6     8.7    26.3  63.4 41/2 2.10   85                            
coal, A                                                                   
Low   2.7     8.8    34.1  54.4  1/2 No.    85                            
grade                                rota-                                
coal, B                              tion                                 
______________________________________                                    
 (Note)                                                                   
 Proximate analysis was made in accordance with JIS M8812, CSN in         
 accordance with JIS M8801-5 and F1 in accordance with JIS M8801-7        
 respectively. (These standards will be invariably used in the tests to be
 indicated herein below.)                                                 
 
    
     
                       TABLE 2                                                     
______________________________________                                    
               To-  Bulk                                                  
               tal  density                                               
               mois-                                                      
                    in tin   Coke strength                                
Run                  ture   can    DI.sub.15.sup.30                       
                                         DI.sub.15.sup.150                
No.  Blending ratio  (%)    (kg/m.sup.3)                                  
                                   (%)   (%)                              
______________________________________                                    
1    Blended coal A 100%                                                  
                     8.0    750    93.8  83.0                             
2      &#34;             6.0    800    94.1  83.9                             
3      &#34;             4.0    850    94.6  86.1                             
4      &#34;             2.0    870    94.8  86.5                             
5      &#34;             0      870    94.8  86.6                             
6    Blended coal A 90% +                                                 
                     8.0    750    89.2  75.7                             
     low grade coal B 10%                                                 
7    Blended coal A 90% +                                                 
                     5.0    810    90.8  76.8                             
     low grade coal B 10%                                                 
8    Blended coal A 90% +                                                 
                     3.0    860    94.9  86.3                             
     low grade coal B 10%                                                 
9    Blended coal A 90% +                                                 
                     0      870    95.4  86.4                             
     low grade coal B 10%                                                 
10   Blended coal A 80% +                                                 
                     8.0    750    85.2  68.7                             
     low grade coal B 20%                                                 
11   Blended coal A 80% +                                                 
                     5.0    810    87.8  74.9                             
     low grade coal B 20%                                                 
12   Blended coal A 80% +                                                 
                     3.0    860    93.3  82.5                             
     low grade coal B 20%                                                 
13   Blended coal A 80% +                                                 
                     0      870    93.8  82.9                             
     low grade coal B 20%                                                 
14   Blended coal A 70% +                                                 
                     0      870    91.4  78.2                             
     low grade coal B 30%                                                 
______________________________________                                    
 (Note)                                                                   
 Total moisture content was determined in accordance with the method for  
 simplified measurement of total moisture content defined by JIS M8811-6; 
 (This method will be invariably used in the tests to be indicated herein 
 below.)                                                                  
 Bulk density in the tin can was determined by placing a 10kg sample in an
 iron box 235 mm in width × 235 mm in length × 355 mm in      
 height, dropping the box from a height of 11 cm onto an iron plate three 
 times and finding the height of the sample held in the box. (This method 
 will be invariably used in the tests to be indicated hereinbelow.)       
 
    
     It is seen from Table 2 that the effect of the preheating of the blended coal A was particularly conspicuous in the test runs involving total moisture contents of not more than 4% and the blendability of the blended coal A for blending the low grade coal B is limited to about 20%. 
     EXAMPLE 2 
     A blended coal, A, indicated in Table 1 above, was treated with the aforementioned fluidized bed to acquire a varying prescribed total moisture content ranging from 8% to 2%, and fed into the hopper 1 of a test apparatus illustrated in FIG. 1. Separately, masec type briquettes (with a total moisture content fixed at 8% and 2%) having a composition shown in Table 3 and measuring 35 mm×35 mm×25 mm were fed into the briquette hopper 2. By the operation of the screw feeder 3 and the vibration feeder 4, the blended coal, A and the briquettes, were drawn out of the hopper 1 and the briquette hopper 2 respectively at a prescribed proportion, transferred through the medium of the scraper type conveyor 5 into the full-scale model coke oven of steel plates improvised by halving only lengthwise the carbonization chamber of a large coke oven measuring 7.1 m in height, 16.5 m in length and 0.46 m in width, and discharged through the sample outlet 7. The samples thus obtained were tested for segregation of briquettes. 
     The results are shown in Table 4. The value given in the Table 4 represent averages of the five samples in heightwise of the full-scale model coke oven. 
     
                       TABLE 3                                                     
______________________________________                                    
              Blending ratio (%)                                          
______________________________________                                    
Blended coal, A 40                                                        
Low grade coal, B                                                         
                60                                                        
Road tar (Additional)                                                     
                 7                                                        
______________________________________                                    
 
    
     
                                           TABLE 4                                 
__________________________________________________________________________
               Percentage of briquettes                                   
               contained at varying                                       
               position (%)                                               
          Blending       Midway                                           
                              Percentage                                  
          ratio of                                                        
               Oven                                                       
                   Underside                                              
                         between                                          
                              of contained                                
                                      Max. variation                      
          briquet-                                                        
               door                                                       
                   of charging                                            
                         charging                                         
                              briquettes (R)                              
                                      coefficient                         
          tes (%)                                                         
               side                                                       
                   hole  holes                                            
                              (max. - Min.)                               
                                      of briquettes                       
__________________________________________________________________________
Total moisture 8%                                                         
          20   29.3                                                       
                   11.7  30.7 19.0    1.54                                
Blended coal, A                                                           
          30   34.6                                                       
                   14.1  43.4 29.3    1.46                                
Total moisture, 8%                                                        
          40   42.8                                                       
                   17.5  55.9 38.4    1.40                                
Briquettes                                                                
          50   50.0                                                       
                   30.9  76.9 46.0    1.54                                
Total moisture 6%                                                         
          20   30.1                                                       
                   11.9  30.2 18.3    1.51                                
Blended coal, A                                                           
          30   35.3                                                       
                   13.0  42.0 29.0    1.40                                
Total moisture, 8%                                                        
          40   43.1                                                       
                   19.8  58.0 38.2    1.45                                
Briquettes                                                                
          50   51.1                                                       
                   28.5  74.0 45.5    1.48                                
Total moisture 4%                                                         
          20   14.1                                                       
                   23.6  20.4 9.5     1.18                                
Blended coal, A                                                           
          30   21.8                                                       
                   32.1  27.3 10.3    1.07                                
Total moisture, 8%                                                        
          40   49.2                                                       
                   38.0  39.6 11.2    1.23                                
Briquettes                                                                
          50   69.5                                                       
                   42.8  44.7 26.7    1.39                                
Total moisture 2%                                                         
          20   14.2                                                       
                   22.2  20.8 8.0     1.11                                
Blended coal, A                                                           
          30   27.4                                                       
                   31.2  29.8 3.8     1.04                                
Total moisture, 8%                                                        
          40   46.9                                                       
                   36.8  37.5 10.1    1.17                                
Briquettes                                                                
          50   65.9                                                       
                   41.9  45.6 24.0    1.32                                
Total moisture 2%                                                         
          20   14.5                                                       
                   22.9  21.0 8.4     1.14                                
Blended coal, A                                                           
          30   28.0                                                       
                   31.0  28.5 3.0     1.03                                
Total moisture, 2%                                                        
          40   47.5                                                       
                   37.3  38.1 10.2    1.19                                
Briquettes                                                                
          50   66.6                                                       
                   42.3  45.0 24.3    1.33                                
Total moisture 8%                                                         
          20   31.2                                                       
                   10.3  32.0 21.7    1.60                                
Blended coal, A                                                           
          30   35.0                                                       
                   13.9  44.5 30.6    1.48                                
Total moisture, 2%                                                        
          40   41.6                                                       
                   18.2  59.3 41.1    1.48                                
Briquettes                                                                
          50   48.7                                                       
                   29.7  78.1 48.4    1.56                                
__________________________________________________________________________
 (Note)                                                                   
 Max. variation coefficient of briquettes = Max. percentage of contained  
 briquettes/blending ratio.                                               
 
    
     It is seen from Table 4 that in the samples involving addition of briquettes to the blended coal, A, having a total moisture content of 8%, the percentages of contained briquettes were decreased to the order of about 50% of the blending ratio of briquettes without reference to the total moisture content of the briquettes and that in the samples blending briquettes in the blending ratio of 40%, portions having the maximum percentage of briquettes in the neighborhood of 60% occurred locally within the coke oven, suggesting the possibility of pushing troubles and other difficulties in discharging from the coke oven. 
     In the case of the samples involving addition of briquettes to the blended coals, A, having total moisture contents of 4% and 2%, the variations in the percentages of contained briquettes are fairly low in the range of 10 to 20% without reference to the total moisture content of briquettes where the blending ratio of briquettes are up to 40%, suggesting that even in the commercial operation, the blending ratio of briquettes can be increased up to 40%. 
     The data indicate that the segregation caused in the coke oven by the addition of briquettes depends more on the total moisture content of the blended coal than on that of the briquettes. The total moisture content of the briquettes was determined by the method for determination of total moisture content (toluene process) specified by JIS K-2425-9. (This method will be invariably used in the tests to be indicated herein below.) 
     EXAMPLE 3 
     A blended coal, C, indicated in Table 5 and formed solely of coking coal was treated with the same fluidized bed as used in Example 1 to acquire a total moisture content of 2%. The coal material for briquetting, having the same composition as shown in Table 3, was treated with a drier to acquire a stated total moisture content, kneaded with 7% of added road tar at 50° to 60° C. for 10 minutes and formed into masec type briquettes 35 mm×35 mm×25 mm with a roll press. The briquettes were mixed in a blending ratio of 30% with the aforementioned blended coal, C. The resultant blend was carbonized by the procedure of Example 1 and the produced coke was tested for coke strength. The relation between the total moisture content of the briquettes and the coke strength is shown in FIG. 2. 
     
                       TABLE 5                                                     
______________________________________                                    
Proximate analysis (%)          Particle                                  
                         Fix-             size                            
                 Vola-   ed        F.I.   (Below                          
Mois-            tile    car-      (Log   3 mm)                           
ture      Ash    matter  bon  CSN  DDPM)  (%)                             
______________________________________                                    
Blend-                                                                    
ed    1.7     8.7    27.2  62.4 51/2 1.36   85%                           
coal, C                                                                   
______________________________________                                    
 
    
     Separately, the aforementioned material coal for briquetting in a state retaining intact its total moisture content was kneaded with 7% of road tar added thereto at 50° to 60° C. for 10 minutes. The mixture was formed into masec type briquettes 35 mm×35 mm×25 mm with a roll press. The briquettes were treated with a drier to acquire a total moisture content of 2% and mixed in a blending ratio of 30% with the blended coal, C, having an adjusted total moisture content of 2%. The resultant mixture was carbonized under the same conditions as those of Example 1 and then tested for coke strength, DI 15   30 , which was found to be 93.5. This value is practically identical with the value 93.6 of the coke strength, DI 15   30 , found for the coke which is produced by blending the briquettes of the type (having a total moisture content of 2%) formed by first treating the material coal for total moisture content adjustment and thereafter molding the material coal with a roll press. 
     This fact shows that the effect of the blend of briquettes is the same, no matter whether the briquettes are obtained by first treating the coal material for to adjust its total moisture content and thereafter molding the material coal with a roll press or are obtained by first molding the material coal with a roll press and thereafter treating the shaped blocks of coal material to adjust their total moisture content. This means that the effect has absolutely nothing to do with the procedure to be followed in the preparation of the briquettes. 
     EXAMPLE 4 
     By following the procedure of Example 1, a blended coal, D, formed solely of coking coal and a low grade coal, E, indicated in Table 6 were treated to have their total moisture contents adjusted to 8% in some test runs and 2% in others and were mixed with each other at varying ratios indicated in Table 7. The resultant blends were mixed with the blended coal, D, low grade coal, E, and road tar at the varying blended ratios also indicated in Table 7, kneaded at 50° to 60° for 10 minutes and thereafter mixed with 40% of masec type briquettes 35 mm×35 mm×25 mm formed in advance with a roll press. The resultant mixtures were carbonized by the procedure of Example 1 and tested for coke strength. 
     The results are shown in Table 7. 
     
                       TABLE 6                                                     
______________________________________                                    
Proximate analysis (%)          Particle                                  
                         Fix-             size                            
                 Vola-   ed        F.I.   (Below                          
Mois-            tile    car-      (Log   3 mm)                           
ture      Ash    matter  bon  CSN  DDPM)  (%)                             
______________________________________                                    
Blend-                                                                    
ed    1.3      8.9   26.4  63.4 51/2 1.92   85                            
coal, D                                                                   
Low                                                                       
grade 2.6     10.0   32.9  54.5 1    1.0    85                            
coal, E                                                                   
______________________________________                                    
 
    
     
                                           TABLE 7                                 
__________________________________________________________________________
Blended coal    Briquettes                                                
       Blending ratio                                                     
                     Blending ratio                                       
   Total    Low           Low              Coke                           
   mois-                                                                  
       Blended                                                            
            grade                                                         
                Total                                                     
                     Blended                                              
                          grade                                           
                              Binder                                      
                                   Total low                              
                                          strength                        
Run                                                                       
   ture                                                                   
       coal, D                                                            
            coal,                                                         
                moisture                                                  
                     coal, D                                              
                          coal,                                           
                              Road tar                                    
                                   grade coal                             
                                          DI.sub.15.sup.150               
No.                                                                       
   (%) (%)  E (%)                                                         
                (%)  (%)  E (%)                                           
                              (%)  content (%)                            
                                          (%)                             
__________________________________________________________________________
15 8.0 100  0   --   --   --  --   --     83.4                            
16 8.0 100  0   8.0  60   40  7    16     84.1                            
17 8.0 100  0   8.0  40   60  7    24     83.4                            
18 8.0 100  0   8.0  20   80  7    32     82.6                            
19 2.0 100  0   --   --   --  --   0      85.1                            
20 2.0 80   20  --   --   --  --   20     83.4                            
21 2.0 60   40  --   --   --  --   40     82.6                            
22 2.0 80   20  8.0  60   40  7    28     84.2                            
23 2.0 80   20  8.0  40   60  7    36     83.5                            
24 2.0 80   20  8.0  20   80  7    44     82.7                            
25 2.0 80   20  2.0  60   40  7    28     84.5                            
26 2.0 80   20  2.0  40   60  7    36     84.1                            
27 2.0 80   20  2.0  25   75  7    42     83.5                            
28 2.0 80   20  2.0  20   80  7    44     83.0                            
__________________________________________________________________________
 
    
     It is seen from Table 7 that in Run No. 23, which involved combined use of the preheated coal (blended coal, D) charging process and the partial briquette charging process, the total low grade coal content was 36%, a value about 12% more than the value 24% obtained in Run No. 17, which represented sole application of the partial briquette charging system. It is further seen that in Run No. 27, which involved additional use of briquettes having an adjusted total moisture content of 2%, the low grade coal could be blended in a ratio of 42%. 
     These high low grade coal contents were ascribable respectively to the synergistic effect of the combined use of the preheated coal charging process and the partial briquette charging process and to the synergistic effect of the additional use of dried briquettes. 
     EXAMPLE 5 
     The same blended coal as used in Run No. 20 of Example 4 was mixed with 40% of briquettes indicated in Table 9 and produced by the procedure of Example 4. The resultant mixture was carbonized by the procedure of Example 1 and the coke thus obtained was tested for coke strength. The results are shown in Table 9. 
     The properties of the caking substance added in the briquettes are shown in Table 8. 
     
                                           TABLE 8                                 
__________________________________________________________________________
Softening Fixed                                                           
              Insolubles in solvent extraction (%)                        
point     carbon                                                          
              n-       Carbon    Ultimate analysis (%)                    
(°C.)                                                              
          (%) hexane                                                      
                  Benzene                                                 
                       disulfide                                          
                            Quinoline                                     
                                 C  H  N  S                               
__________________________________________________________________________
Caking                                                                    
     187  57.9                                                            
              79.2                                                        
                  48.3 34.1 14.7 85.7                                     
                                    5.9                                   
                                       1.9                                
                                          7.0                             
substance                                                                 
__________________________________________________________________________
 
    
     
                                           TABLE 9                                 
__________________________________________________________________________
                  Briquettes                                              
Blended coal            Blending ratio                                    
         Blending ratio               Road                                
                                          Coal                            
              Low            Low      tar tar                             
    Total                                                                 
         Blended                                                          
              grade                                                       
                  Total Blended                                           
                             grade                                        
                                 Caking                                   
                                      (addi-                              
                                          (addi-                          
                                               Total low                  
                                                       Coke strength,     
Run moisture                                                              
         coal, D                                                          
              coal,                                                       
                  moisture                                                
                        coal, D                                           
                             coal,                                        
                                 substance                                
                                      tional)                             
                                          tional)                         
                                               coal content               
                                                       D.sub.15.sup.150   
No. (%)  (%)  E (%)                                                       
                  (%)   (%)  E (%)                                        
                                 (%)  (%) (%)  (%)     (%)                
__________________________________________________________________________
29  2.0  80   20  8.0   25   75  --   7   --   42      83.0               
30  2.0  80   20  6.0   25   75  --   7   --   42      83.0               
31  2.0  80   20  4.0   25   75  --   7   --   42      83.4               
32  2.0  80   20  2.0   25   75  --   7   --   42      83.4               
33  2.0  80   20  8.0   13.5 81  5.5  7   --   44.4    83.0               
34  2.0  80   20  6.0   13.5 81  5.5  7   --   44.4    83.2               
35  2.0  80   20  4.0   13.5 81  5.5  7   --   44.4    83.9               
36  2.0  80   20  2.0   13.5 81  5.5  7   --   44.4    84.0               
37  2.0  80   20  2.0   9.5  85  5.5  7   --   46      83.4               
38  2.0  80   20  2.0   4.5  90  5.5  7   --   48      82.8               
39  2.0  80   20  2.0   9.5  85  5.5  --  7    46      83.4               
40  2.0  80   20  2.0   4.5  90  5.5  --  7    48      82.7               
__________________________________________________________________________
 
    
     It is seen from Table 9 that addition of the caking substance by a blending ratio of 5.5% to briquettes permitted the blending ratio of the low grade coal, E, into the briquettes to be increased by 6% in the case of briquettes having a total moisture content of 8%, and that the increase in the blending ratio was raised to 10% when the total moisture content of briquettes was lowered to 2%. 
     This fact shows that the effect of the addition of the caking substance into the briquettes is manifested more conspicuously when the total moisture content of briquettes is lowered. Thus, the reduction in the total moisture content brings about what may well be called an unexpected effect. 
     EXAMPLE 6 
     Blended coals, F and G, of the respective compositions indicated below were subjected to a varying pretreatment (I through IV) described below, and placed in 18-liter tin cans, then the blended coal was carbonized by the procedure of Example 1, and tested for coke strength. The results of the test are shown in Table 10. 
     
         ______________________________________                                    
Blended coal, F:                                                          
Strongly coking coal from U.S.A.                                          
                         25%                                              
Semi-strongly coking coal from Australia                                  
                         55%                                              
Domestic weakly coking coal                                               
                         20%                                              
Blended coal, G:                                                          
Strongly coking coal from Australia                                       
                         25%                                              
Semi-strongly coking coal from U.S.A.                                     
                         55%                                              
Domestic weakly coking coal                                               
                         20%                                              
______________________________________                                    
 
    
     Description of pretreatment: 
     I: The given blended coal was pulverized to an extent enough to produce coal particles containing 80% of particles of sizes not exceeding 3 mm and then was adjusted to acquire a total moisture content of 8%. 
     II: The blended coal which had undergone Pretreatment I was preheated at 200° C. in a fluidized bed 350 mm in diameter and then left to cool off on an iron plate. 
     III: Of the component coals making up a given blended coal, the coking coal of Australian origin was pulverized. The resultant particles were screened through a 6-mm sieve, and the coarse particles retained on the sieve were again pulverized, to produce particles containing 80% of particles of sizes not exceeding 3 mm. The remaining two component coking coals were pulverized to produce particles containing 80% of particles of sizes not exceeding 3 mm. Then, these particles (course particles pulverized again and fine particles passed the sieve of Australian origin, the other coking coals) obtained as described above were mixed. 
     IV: The blended coal which had undergone Pretreatment III was preheated at 200° C. and then left to cool off on an iron plate similarly to Pretreatment II. 
     
                       TABLE 10                                                    
______________________________________                                    
                             Coke strength                                
Pre-     Total    Bulk density                                            
                             D.sub.15.sup.30 (%)                          
Run  treat-  moisture in tin can                                          
                               Blended                                    
                                      Blended                             
No.  ment    (%)      (kg/m.sup.3)                                        
                               coal, F                                    
                                      coal, G                             
______________________________________                                    
41   I       8.0      750      92.1   92.2                                
42   II      0        870      92.8   92.9                                
43   III     8.0      750      92.5   92.7                                
44   IV      0        870      93.6   93.5                                
______________________________________                                    
 
    
     
                       TABLE 11                                                    
______________________________________                                    
             Mesh size 4 mm                                               
                        Mesh size 6 mm                                    
Kind of coal                                                              
         Screening Percentage                                             
                             CSN  Percentage                              
                                          CSN                             
______________________________________                                    
Strongly Retained  48.6 (%)  11/2 40.3 (%)                                
                                          11/2                            
coking coal                                                               
         Passed    51.4      6    59.3    51/2                            
Semi-strongly                                                             
         Retained  49.1      11/2 37.9    11/2                            
coking coal                                                               
         Passed    50.9      6    62.1    5                               
______________________________________                                    
 (Note)                                                                   
 Table 11 shows the percentages at which the coal particles resulting from
 the aforementioned pulverization of the coking coal of Australian origin 
 were partly retained on and partly passed through sieves 4 mm and 6 mm in
 mesh size when they were screened through the sieves, and the respective 
 CSN values.                                                              
 
    
     EXAMPLE 7 
     The blended coal, F, of Example 6 was mixed at a varying blending ratio with a low grade coal, H, shown in Table 12.  The resultant mixtures were subjected to the pretreatments of Example 6, with and without modifications. Specifically, Pretreatments I and II were performed in their unmodified form. Pretreatment III&#39; comprised pulverizing only the semi-strongly coking coal of Australian origin of a given blended coal, screening the resulting particles through a 6-mm sieve and pulverizing again the coarse particles retained on the sieve to produce particles containing 80% of particles of sizes not exceeding 3 mm, then mixing the pulverized course particles and fine particles which passed the sieve of Australian origin with the remaining coking coals and low grade coal H which had been separately pulverized into particles containing 80% of particles of sizes not exceeding 3 mm. And Pretreatment IV&#39; comprised causing the coal resulting from Pretreatment III&#39; to be preheated at 200° C. and then left to cool off on an iron plate similarly to Pretreatment II. The blended coal obtained by each of the pretreatments was carbonized and then tested for coke strength similarly to Example 6. The results are shown in Table 13. 
     
                       TABLE 12                                                    
______________________________________                                    
Proximate analysis (%)                                                    
                         Fix-             Particle                        
                 Vola-   ed        FI     size                            
Mois-            tile    car-      (Log   (below                          
ture      Ash    matter  bon  CSN  DDPM)  3 mm)                           
______________________________________                                    
Low   2.7     8.8    34.1  54.4 1/2  No     80%                           
grade                                rota-                                
coal                                 tion                                 
______________________________________                                    
 
    
     
                       TABLE 13                                                    
______________________________________                                    
       Blending                                                           
       ratio (%)  To-               Coke                                  
     Pre-             Low   tal  Bulk density                             
                                          strength                        
Run  treat-  Blended  grade mois-                                         
                                 in tin can                               
                                          DI.sub.15.sup.30                
No.  ment    coal, F  coal, H                                             
                            ture (kg/m.sup.3)                             
                                          (%)                             
______________________________________                                    
45   I       95       5     8.0  750      91.2                            
46   II      90       10    0    870      92.5                            
47   II      80       20    0    870      92.1                            
48   II      70       30    0    870      91.4                            
49   III&#39;    95       5     8.0  750      92.1                            
50   III&#39;    90       10    8.0  750      91.8                            
51   IV&#39;     90       10    0    870      93.2                            
52   IV&#39;     80       20    0    870      92.8                            
53   IV&#39;     70       30    0    870      92.1                            
54   IV&#39;     60       40    0    870      91.2                            
______________________________________                                    
 
    
     It is seen from Table 13 that in Run Nos. 51-54 involving Pretreatment IV&#39;, namely, the steps of selectively pulverizing the coking coal of Australian origin, mixing the resultant coal particles with the other coking coals to form the blended coal, F, combining the blended coal, F, with the low grade coal, H, and thereafter treating the resultant blend for total moisture content adjustment, blends were produced which each consisted of 70% of the blended coal, F, and 30% of the low grade coal, H. 
     EXAMPLE 8 
     The material coal for briquetting prepared by blending the same low grade coal, H, (Table 12) as used in Example 7 in a varying blending ratio with the blended coal, G, of Example 6 and road tar having a softening point of 25° C. and added thereto as a binder were kneaded at 50° to 60° C. for 10 minutes. The resultant mixture was formed into masec type briquettes 35 mm×35 mm×25 mm with a roll press. The adjusted total moisture content of the briquettes was 8% in some test runs and 2% in others. 
     Then, the blended coal blended of 70% of the blended coal, G, of Example 6 and 30% of the low grade coal, H, of Example 7 was subjected to Pretreatment IV&#39; and mixed with 40% of a varying type of briquettes prepared as described above. The resultant mixture was carbonized by the procedure of Example 6, and the coke was tested for coke strength. The blending ratio of the material coals for briquetting and the results of the test for coke strength are shown in Table 14. 
     
                                           TABLE 14                                
__________________________________________________________________________
                                   Total                                  
        Blended coal (%)                                                  
                 Briquettes (%)    low Bulk                               
        Blending ratio                                                    
                      Blending ratio                                      
                                   grade                                  
                                       density                            
                                            Coke                          
             Low           Low Binder                                     
                                   coal                                   
                                       in tin                             
                                            strength                      
Run                                                                       
   Total                                                                  
        Blended                                                           
             grade                                                        
                 Total                                                    
                      Blended                                             
                           grade                                          
                               (addi-                                     
                                   content                                
                                       can  DI.sub.15.sup.30              
No.                                                                       
   moisture                                                               
        coal, G                                                           
             coal, H                                                      
                 moisture                                                 
                      coal, G                                             
                           cla, H                                         
                               tional)                                    
                                   (%) (kg/m.sup.3)                       
                                            (%)                           
__________________________________________________________________________
55 0    70   30  8.0  60   40  7   34  950  92.3                          
56 0    70   30  8.0  50   50  7   38  950  92.1                          
57 0    70   30  8.0  40   60  7   42  950  91.1                          
58 0    70   30  2.0  60   40  7   34  950  93.0                          
59 0    70   30  2.0  50   50  7   38  950  92.5                          
60 0    70   30  2.0  40   60  7   42  950  92.1                          
61 0    70   30  2.0  30   70  7   46  950  91.7                          
__________________________________________________________________________
 
    
     It is seen from Table 14 that in the coke of the charging coal consisting of 60% of the blended coal containing 30% of the low grade coal, H, and 40% of the briquettes, the proportion of the low grade coal to the whole amount of the charging coal was 38% when the briquettes had a total moisture content of 8% (Run No. 56), whereas the proportion could be increased to 42% when the briquettes incorporated had a total moisture content of 2% (Run No. 60). 
     EXAMPLE 9 
     By the procedure of Example 8, briquettes were formed of what was obtained by mixing the low grade coal, H, indicated in Table 12 in a varying blending ratio with the blended coal, G, used in Example 6 and adding to the resultant mixture a binder (there was used coal tar or road tar) and a caking substance as shown in Table 15. Then, 60% of the blended coal which was obtained by mixing the blended coal, G, with 30% of the low grade coal, H, and subjecting the resultant mixture to Pretreatment IV&#39; was mixed with 40% of the briquettes obtained as described above. The resultant blend was carbonized by following the procedure of Example 6, and the coke was tested for coke strength. 
     The composition of the briquettes and the results of the test for coke strength are shown in Table 16. 
     
                       TABLE 15                                                    
______________________________________                                    
                   Insolubles in solvent extraction                       
Softening  Fixed   (%)                                                    
      point    carbon  n-           Carbon Quino-                         
      (°C.)                                                        
               (%)     Hexane                                             
                             Benzene                                      
                                    disulfide                             
                                           line                           
______________________________________                                    
Caking                                                                    
      187      57.9    79.2  48.3   34.1   14.7                           
sub-                                                                      
stance                                                                    
______________________________________                                    
Ultimate analysis (%)                                                     
C            H          N          S                                      
______________________________________                                    
85.7         5.9        1.2        7.0                                    
______________________________________                                    
 
    
     
                                           TABLE 16                                
__________________________________________________________________________
                                        Total                             
                                        low                               
        Blended coal (%)                                                  
                 Briquettes (%)         grade                             
                                            Bulk                          
        Blending ratio                                                    
                      Blending ratio    coal                              
                                            density                       
                                                 Coke                     
             Low           Low Caking                                     
                                   Binder                                 
                                        con-                              
                                            in tin                        
                                                 strength                 
Run                                                                       
   Total                                                                  
        Blended                                                           
             grade                                                        
                 Total                                                    
                      Blended                                             
                           grade                                          
                               sub-                                       
                                   (Addi-                                 
                                        tent                              
                                            can  DI.sub.15.sup.30         
No.                                                                       
   moisture                                                               
        coal, G                                                           
             coal, H                                                      
                 moisture                                                 
                      coal, G                                             
                           coal, H                                        
                               stance                                     
                                   tional)                                
                                        (%) (kg/m.sup.3)                  
                                                 (%)                      
__________________________________________________________________________
62 0    70   30  8.0  39.5 55  5.5 Coal tar                               
                                        40  950  92.2                     
                                   7                                      
63 0    70   30  8.0  34.5 60  5.5 Coal tar                               
                                        42  950  91.4                     
                                   7                                      
64 0    70   30  8.0  39.5 55  5.5 Road tar                               
                                        40  950  92.1                     
                                   7                                      
65 0    70   30  2.0  29.5 65  5.5 Coal tar                               
                                        44  950  92.7                     
                                   7                                      
66 0    70   30  2.0  19.5 75  5.5 Coal tar                               
                                        48  950  92.1                     
                                   7                                      
67 0    70   30  2.0   9.5 85  5.5 Coal tar                               
                                        52  950  91.6                     
                                   7                                      
68 0    70   30  2.0  19.5 75  5.5 Road tar                               
                                        48  950  92.1                     
                                   7                                      
__________________________________________________________________________
 
    
     It is seen from Table 16 that the addition of the caking substance in a blending ratio of 5.5% to the briquettes permitted the total low grade coal content to be increased by 2% in the case of briquettes having a total moisture content of 8% (Run Nos. 56-62) and that the increase in the total low grade coal content rose to 6% in the case of briquettes having a total moisture content of 2% (Run Nos. 60-66). This fact shows that the effect of the addition of the caking substance into the briquettes is conspicuously enhanced by a decrease in the total moisture content of the briquettes. 
     EXAMPLE 10 
     Of the blended coal, G, shown in Example 6, the strongly coking coal of Australian origin was pulverized. The resultant particles were screened through a 6-mm sieve. The fine particles collecting under the 6-mm sieve were mixed with the remaining semi-strongly coking coal and weakly coking coal. The resultant mixture was blended in a varying blending ratio with the low grade coal, H, shown in Table 12 of Example 7. The blended coal thus obtained was treated to be given an adjusted total moisture content of 2% and carbonized by following the procedure of Example 6, and the coke was tested for coke strength. The results are shown in Table 17. 
     
                                           TABLE 17                                
__________________________________________________________________________
Blending ratio (%)                                                        
   Particles of strongly                                                  
              Particles of strongly       Bulk                            
   coking coal of                                                         
              coking coal of                                              
                          Semi-strongly                                   
                                 Weakly                                   
                                      Low Density                         
                                               Coke                       
Run                                                                       
   Australian orgin                                                       
              Australian orgin                                            
                          coking of coal                                  
                                 coking                                   
                                      grade                               
                                          in tin can                      
                                               strength                   
No.                                                                       
   retained on the sieve                                                  
              passed through the sieve                                    
                          U.S.A. origin                                   
                                 coal coal, H                             
                                          (kg/m.sup.3)                    
                                               DI.sub.15.sup.30           
__________________________________________________________________________
                                               (%)                        
69 0          11.6        42.9   15.5  30 870  92.5                       
70 0          10.8        39.8   14.4 35  870  92.1                       
71 0          10.0        36.7   13.3 40  870  91.5                       
__________________________________________________________________________
 
    
     It is seen from Table 17 that the blended coal formed without blending the particles retained on the sieve of the strongly coking coal of Australian origin abounded with inert particles and permitted blending of as much as 35% of the low grade coal when the blended coal was treated to be given an adjusted total moisture content of 2%. 
     EXAMPLE 11 
     The particles retained on the sieve of the strongly coking coal of Australian origin which were not blended in the blended coal in Example 10 were further pulverized and used as the coal material for briquetting. By following the procedure of Example 8, briquettes were formed of what was obtained by mixing the additionally pulverized particles with the caking substance indicated in Table 15 and road tar or coal of Run No. 70 of Example 10, 40% of either varying the blending ratio of low grade coal or the varying the total moisture content of the briquettes obtained as described above were mixed. The resultant mixture was carbonized by the procedure of Example 1 and the coke was tested for coke strength. The blending ratios of material coals and the results of the test for coke strength are shown in Table 18. 
     It is seen that the low grade coal content of the blended coal can be increased to a great extent, as is plain from Example 9, by using as the coal material for briquetting the particles retained on the sieve of the strongly coking coal of Australian origin. It is also clear from the present example that one half of the entire charging coal is allowed to be substituted with low grade coal when the total moisture content of briquettes is adjusted or the caking substance is added into the briquettes. 
     
                                           TABLE 18                                
__________________________________________________________________________
Blended coal (%)        Briquettes (%)                                    
        Blending ratio       Blending ratio                               
              Particles            Particles                              
              of strongly          of strongly                            
              coking coal          coal of                                
              of                   Australian                             
              Australian           origin                                 
        Particles                                                         
              origin         Particles                                    
                                   passed                                 
        of strongly                                                       
              passed         of strongly                                  
                                   through           Total                
        coking coal                                                       
              through the    coking coal                                  
                                   the sieve,        low                  
        of    sieve, semi    of    semi              grade                
        Australian                                                        
              strongly                                                    
                    Low      Australian                                   
                                   strongly                               
                                         Low         coal                 
                                                         Coke             
        origin                                                            
              coking coal                                                 
                    grade    origin                                       
                                   coking coal                            
                                         grade                            
                                             Caking                       
                                                 Binder                   
                                                     con-                 
                                                         strength         
Run                                                                       
   Total                                                                  
        retained on                                                       
              and weakly                                                  
                    coal,                                                 
                        Total                                             
                             retained on                                  
                                   and weakly                             
                                         coal,                            
                                             sub-                         
                                                 (addi-                   
                                                     tent                 
                                                         DI.sub.15.sup.30 
                                                         5                
No.                                                                       
   moisture                                                               
        the sieve                                                         
              coking coal                                                 
                    H   moisture                                          
                             the sieve                                    
                                   coking coal                            
                                         H   stance                       
                                                 tional)                  
                                                     (%) (%)              
__________________________________________________________________________
72 0    0     65    35  8    15.2  39.8  45  0   Road                     
                                                     39  92.1             
                                                 tar 7                    
73 0    0     65    35  8    13.7  25.8  55  5.5 Coal                     
                                                     43  92.2             
                                                 tar 7                    
74 0    0     65    35  2    14.2  30.8  55  0   Coal                     
                                                     43  92.1             
                                                 tar 7                    
75 0    0     65    35  2    12.2  12.3  70  5.5 Coal                     
                                                     49  92.1             
                                                 tar 7                    
76 0    0     65    35  2    12.2  12.3  70  5.5 Road                     
                                                     49  92.2             
                                                 tar 7                    
__________________________________________________________________________