Small scale determination of metallurgical coke CSR

Fuel 114 (2013) 229–234

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Small scale determination of metallurgical coke CSR Tony MacPhee a,⇑, Louis Giroux a, Ka Wing Ng a, Ted Todoschuk b, Marcela Conejeros c, Cornelis Kolijn c a

CanmetENERGY, 1 Haanel Drive, Ottawa, ON, Canada K1A 1M1 ArcelorMittal Dofasco Inc., 1390 Burlington Street East, Hamilton, ON, Canada L8N 3J5 c Teck Coal Ltd., Suite 1000, 205-9th Ave. S.E., Calgary, AB, Canada T2G 0R3 b

a r t i c l e

i n f o

Article history: Received 26 January 2012 Received in revised form 14 August 2012 Accepted 23 August 2012 Available online 12 September 2012 Keywords: Coke Cokemaking CSR CRI Carbon forms

a b s t r a c t Coke Strength after Reaction (CSR) and the concomitant Coke Reactivity Index (CRI) are useful parameters for assessing the behavior of coke in blast furnace. To measure CSR and CRI of the resultant coke from a particular metallurgical coal or blend, a pilot scale oven test for producing appropriate industrial grade coke for measurements is unavoidable. If the quantity of coal sample available is not sufficient for pilot scale oven test, CSR measurement of the resultant coke is normally not possible. CanmetENERGY has developed a procedure for producing coke to allow CSR measurement involving relatively small amounts of coal sample (15 kg). The procedure involves producing semi-coke using the Sole Heated Oven in accordance with ASTM standard D2014-97 (2004). In the Sole Heated Oven test the coal sample is heated only from the bottom (the sole) up to 950 °C with the top of the oven charge rising to 500 °C over a period of 6–7 h. The resulting semi-coke is quenched (either wet or dry) and subsequently reheated to 1100 °C under nitrogen for 1 h. CSR and CRI are measured using the coke produced using this procedure. To demonstrate the validity of CSR and CRI measured using this approach, identical coal blends were carbonized concurrently using the CanmetENERGY pilot scale moveable wall oven (460 mm wide, 350 kg capacity) and the procedures mentioned above. CSR and CRI of the cokes produced by these two approaches were compared. Statistical analysis and coke textual analysis were performed to demonstrate the relevance of this novel approach on CSR determination. Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved.

1. Introduction Current world-wide ironmaking capacity is dominated by blast furnace technology. In 2009, this technology accounted for 94% of global hot metal production, 912.2 Mt [1]. In comparison, direct reduced iron (DRI) production was limited to only 53.1 Mt [2]. The performance and efficiency of blast furnace ironmaking technology is continuously improving. One of the factors contributing to the success of blast furnace ironmaking is the continued amelioration in coke quality. Metallurgical coke is the major source of carbon in the operation of the blast furnace. Besides being responsible for producing reducing gas, coke also supports the descending burden and provides passages/voids through it for distributing reducing gas in the furnace. Moreover, the combustion of coke in the lower hearth by the injected blast generates heat for melting of the hot metal. Because of the numerous functions of coke in the blast furnace, stringent requirement on its physical and chemical properties are needed to ensure smooth operation of high productivity modern blast furnaces [3]. ⇑ Corresponding author. E-mail address: [email protected] (T. MacPhee).

In the lower hearth of the blast furnace, coke is the only solid material present to support the entire weight of the burden above. Coke, possessing high mechanical strength in extremely hot and dynamic environments, is required to cope with the increase in throughput of large sized blast furnaces. Prior to its descent to the lower hearth, coke reacts with CO2 produced from the reduction of iron ore to generate CO to replenish the source of this reducing gas required for reduction of iron ore in the upper portion of the furnace. Therefore, the coke charged into the blast furnace must be capable of generating CO by reacting with CO2 while simultaneously maintaining its physical strength after reaction. Among the important indicators for assessing the quality of coke for blast furnace application are Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) developed by Nippon Steel Corporation in the early 1970s [4]. To estimate the quality of coke produced from specific coal blends in terms of CSR and CRI, the most economical way is by carrying out carbonization in a pilot-scale coke oven having known and proven capability of producing industrial grade coke. CanmetENERGY currently operates two pilot-scale slot-type coke ovens (460 mm wide and 350 kg capacity). The pilot-scale coke oven used in this investigation is depicted in Fig. 1.

0016-2361/$ - see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fuel.2012.08.036

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specific gravity (ASG), the ratio of the mass of a volume of dry coke to the mass of an equal volume of water. Coke ASG varies with the rank and ash content of the coal carbonized, the bulk density of the coal charge in the oven, the carbonization temperature and the coking time [9]. Furthermore, microscopical analysis of the textures was performed on the sole-heated and pilot-scale oven cokes to compare them for their carbon forms. As discussed later, this technique is, among numerous advantages, extremely useful for understanding the behavior of coal during coking and for interpreting pilot movable wall oven results including pressure generation and coke quality results.

2. Experimental Fig. 1. CanmetENERGY pilot-scale coke oven.

The cokes produced in either of these ovens have been shown over time to be of similar quality to industrial coke via benchmarking against industrial ovens [5]. The pilot scale oven test requires a specific amount of coal to ensure the coke produced is appropriate for CSR evaluation. In such instances where the amount of coal available is insufficient to perform a pilot-scale test, as for the case of an exploration bore hole sample, CSR and CRI normally cannot be measured. Preparing coke in small scale oven is a common practice for evaluating coking conditions and coke properties. Lee and Lee [6] used a moveable wall oven with 30 kg capacity for studying internal gas pressure development during coking. Grigore et al. [7] compared the transformation of coke ash mineralogy prepared from ovens with 0.07 kg, 9 kg and 400 kg capacity. Sakurovs et al. [8] have examined the effects of the NCS reactivity on coke mineralogy. However, to the best of the authors’ knowledge, there is no published result on direct comparison of CSR and CRI of coke prepared from different scale ovens available in the literature. In an effort to broaden the ability to measure CSR and CRI with limited amounts of coal sample, a novel procedure for producing coke involving carbonization using a sole-heated oven was developed at CanmetENERGY. The sole-heated oven used in this study is shown in Fig. 2. To validate this new approach for producing coke for CSR and CRI evaluation, concurrent carbonization tests of identical coal blends using sole-heated oven and pilot-scale moveable wall oven were performed. CSR and CRI of the cokes produced using both carbonization routes were compared. Besides comparing sole-heated oven and pilot-scale oven cokes for their CSR and CRI, these were also evaluated for their apparent

Fig. 2. CanmetENERGY sole-heated oven.

2.1. Coke preparation in sole-heated oven for CSR/CRI determination The preparation of a coke sample for CSR evaluation using a coal sample of limited quantity involves two steps: (1) Semi-coke preparation. (2) Heat treatment. For preparation of semi-coke, the sole-heated oven was employed in accordance with the ASTM D2014-97 (2010) Standard for expansion or contraction of coal. A total of 12 kg of sample (coal or blends) is divided equally and each half-charged into chambers approximately 280 mm in width, length and depth of a double-chambered oven. A weighted piston applies a constant load of 15.17 ± 0.35 kPa on the surface of the coal in each of the chambers throughout the test. The coal bed is heated from below by the sole plate initially set at 554 °C and gradually ramped up to 950 °C according to a prescribed temperature program. The test is considered complete when the temperature at the top of the coal bed reaches 500 °C after a period of 6–7 h. Following completion of the test, the coke is pushed from the oven, quenched in water, drained and oven dried overnight at 120 °C. In cases where expansion/contraction values are reported, the measured expansion or contraction of the sample is converted to a reference base of 833 kg/m3 and 2% moisture. For heat treatment, the dried semi-coke (8–9 kg) is subsequently introduced in pieces (50  175 mm) into a stainless steel holding box hermetically sealed on top with 3 mm thick section of stainless steel with a 1 cm exit hole in the centre for venting the hot coke gases. The holding box is connected to N2 gas for continually flushing the semi-coke (5–10 L/min flowrate) to prevent its combustion. The holding box with the semi-coke inside is then heated in a Muffle Furnace from ambient to 1100 °C in 2–3 h at the rate of 5–10 °C/min. Upon attaining 1100 °C, the coke is soaked for an additional hour. Then, cooling is allowed to take place to approximately 100 °C. The entire heating and cooling cycle is carried out in a continuous flow of N2 and requires about 15 h to complete. The average weight loss of coke during the heat-treatment process has been measured to be 5 ± 2%. After the heat treatment, the coke sample produced was prepared and tested for CSR and CRI measurement as per specifications in the ASTM D5341-99 (2010) Standard. By definition, the CRI is the percent weight loss of the coke sample after reaction in CO2 at 1100oC for 2 h. The cooled, reacted coke is then tumbled in an I-drum for 600 revolutions at 20 rpm. The cumulative percent of +9.5 mm coke after tumbling is denoted as the CSR. The repeatability limit (r) of this method for CRI is 2.4 and for CSR is 5.4; the reproducibility limit (R) of this method for cokes in CRI range 20– 28 is between 5 and 7 and that for cokes in CSR range 55–70 (acceptable grade for ironmaking) is also between 5 and 7.

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2.2. Carbon form analysis Carbon form analysis in this study was carried out as per a combination of the US Steel method [10] and the CanmetENERGY method. A single point count is made for each measured field of view. For each field, the stage is rotated in order to determine the possible highest rank carbon form. Normally 500 point counts are performed on a sample. Each carbon form is derived from an assumed parent coal V-type. From the coke texture analysis, one can determine the ‘effective coal reflectance (%Ro)’ and also the percentages of low-, medium- and high-volatile parent coals used in the blend. The CMSI [11] is the coke mosaic size index defined as:

CMSI ¼

ovens were homogenized and prepared simultaneously. Hence, they were identical with same moisture content. Due to the design of the two ovens, the bulk densities of the coal blend in the oven were different as shown in Table 1. The importance of adequate bulk density on coke quality has long been recognized [12]. As described earlier, the CSR test has repeatability and reproducibility limits of 5 and 7, respectively (ASTM D5341-99 (2010). The Sole Heated Oven procedure produces coke for CSR testing that is within these limits for comparing to pilot-scale oven results. Table 2 compares CSR’s determined in the two types of ovens. CSR range of the cokes examined was between 42 and 65. The CSR difference, expressed as a %, between ovens is also listed in this table.

fð%IncipientÞ þ 2ð%CF þ %CMÞ þ 3ð%CC þ %LF þ %LMÞ þ 4ð%LC þ %RFÞ þ 5ð%RM þ %RCÞg ðiÞ ð100  %Isotropic  %Total inertsÞ

This is a mathematical method to summarize the carbon form analysis. The formula used in this work is an adaptation of Coin’s method. The higher the CMSI, the higher the rank based on carbon forms measured. 2.3. Coke apparent specific gravity (ASG) determination ASG of cokes were determined following a method developed at CanmetENERGY and related to the ASTM D167-93 (2004) and ISO 1014:1985 Standards. 3. Results 3.1. CSR and CRI Analysis in Pilot-Scale and Sole-Heated Ovens The primary objective of this work is to validate and compare the measurement of CSR and CRI of cokes produced in the soleheated oven to those generated in a pilot-scale oven. To achieve this goal, nineteen (19) coal blends were thus carbonized concurrently in both types of ovens at CanmetENERGY. Table 1 shows the proximate analysis, mean Ro and particle sizes of the 19 coal blends used in this test. In the same table, the oven charge bulk density in the pilot scale oven and the soleheated oven are also shown. The coal blends carbonized in the both

Fig. 3 shows the linear relationship existing between the CSR obtained for the Sole Heated Oven coke and that for the pilot scale oven coke. As can be seen, the data points are evenly distributed on both sides of the line of best fit, indicating that there is no bias due to the coke preparation method. A strong linear relationship (r2 = 0.87) is observed with a slope of 0.88. This indicates that CSR of the coke samples produced using both methods are very similar. The scattering observed in the data points arises from the accumulated random error in coal handling, coke preparation and CSR measurement, etc. A more detailed analysis of the difference in CSR measured between the two preparation methods reveals that the average of the difference in CSR among the measurements is 0.06% and the standard deviation is 3.6%. The calculated 95% confidence interval is 1.6%. As shown in this error analysis, the CSR measured using sole-heated coke is within ±2% of the pilot oven CSR value. Table 3 compares CRI’s of the corresponding coke measured in the two types of ovens. CRI range of the cokes examined was between 23 and 37. The CRI difference, expressed as a %, between ovens is also listed in this table. Fig. 4 shows the linear relationship existing between the CRI obtained for the pilot scale oven coke and that for the sole-heated oven coke. As for CSR, there is no apparent bias between the preparation methods on CRI measurement. A strong linear relationship

Table 1 Coal blends characteristic. Test no.

Particle size

Proximate analysis(db)

<3.35 mm (%)

Ash (%)

Volatile matter (%)

Fixed Carbon (%)

Carbon dmmf (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

81.9 77.5 75.5 80.9 83.0 81.2 83.7 82.6 80.6 82.1 80.8 83.6 81.1 82.7 80.2 80.2 81.9 82.0 81.7

7.7 6.9 8.0 7.3 7.6 7.2 7.9 8.1 8.5 8.4 7.6 9.5 7.7 8.3 7.7 7.7 7.0 6.9 7.4

28.0 29.5 28.1 29.2 28.6 29.0 28.7 27.0 28.2 27.6 29.0 27.0 29.2 28.0 27.1 26.5 29.2 28.9 28.5

64.4 63.6 63.9 63.5 63.7 63.8 63.4 64.9 63.3 64.0 63.4 63.5 63.1 63.7 65.2 65.8 63.8 64.3 64.1

70.4 68.9 70.1 69.2 69.7 69.4 69.5 71.3 69.9 70.5 69.3 71.0 69.1 70.2 71.3 72.0 69.3 69.7 69.9

Mean Ro

Oven bulk density (kg/m3) Pilot scale oven

Sole-heated oven

1.12 1.12 1.15 1.13 1.22 1.11 1.17 1.21 1.21 1.19 1.22 1.26 1.19 1.22 1.2 1.27 1.17 1.15 1.22

821.2 823.2 824.4 823.8 824.0 822.5 823.5 823.5 823.2 822.8 824.0 820.9 822.9 818.4 823.5 822.9 824.2 824.4 825.2

825.4 793.5 806.3 869.2 786.7 794.0 783.0 820.1 793.6 809.0 778.4 841.1 813.5 826.6 807.0 805.6 762.1 759.9 776.7

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Table 2 Comparison of CSR in pilot scale and sole heated oven.

40

Pilot scale oven

Sole heated oven

% Difference

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

61.9 60.5 60.3 60.3 58.0 65.0 51.3 60.5 60.6 62.7 59.9 42.8 60.9 50.6 60.3 57.1 54.5 52.1 57.9

62.4 60.8 63.9 61.8 54.7 63.2 50.9 61.4 61.5 61.4 56.7 41.5 60.2 51.8 61.7 55.6 59.0 52.4 55.6

0.8 0.5 6.0 2.5 5.7 2.8 0.8 1.5 1.5 2.1 5.3 3.0 1.1 2.4 2.3 2.6 8.3 0.6 4.0

CRI-Pilot Scale Oven

Test no.

35 y = 0.90x + 2.57 2 R = 0.81

30

25

20 20

25

30

35

40

CRI-Sole Heated Oven Fig. 4. CRI relationship between sole-heated oven and pilot scale oven.

70

CSR-Pilot Scale Oven

65 60 y = 0.88x + 7.05 2 R = 0.87

55 50 45 40 40

45

50

55

60

65

70

Fig. 5. Relationship between CSR and CRI of cokes from both ovens.

CSR-Sole Heated Oven Fig. 3. CSR relationship between sole-heated oven and pilot scale oven.

Table 3 Comparison of CRI in pilot scale and sole-heated oven. Test no.

Pilot scale oven

Sole heated oven

% Difference

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

22.7 25.1 26.9 25.3 28.1 22.5 31.0 25.3 25.6 25.9 26.6 35.9 26.0 32.0 27.6 28.8 30.1 31.5 26.1

23.9 25.1 24.9 25.0 29.1 24.2 29.9 25.8 26.2 25.8 28.0 37.2 26.9 30.8 25.9 30.3 27.0 32.8 29.0

5.3 0.0 7.4 1.2 3.6 7.6 3.5 2.0 2.3 0.4 5.3 3.6 3.5 3.8 6.2 5.2 10.3 4.1 11.1

(r2 = 0.81) is observed with a slope of 0.90 for the line of best fit. The average of the difference in CRI between the two coke preparation methods is 1.1% and the standard deviation is 5.4%. The calculated 95% confidence interval is 2.4%. Hence, the CRI measured using sole-heated coke is within ±3% of the pilot oven CRI value.

Fig. 5 shows the relationship between CSR and CRI of cokes produced from both the pilot scale oven and the Sole Heated Oven. As can be seen, cokes from both ovens exhibit the same relationship between CSR and CRI. It suggested that the after reaction strength and reactivity of the coke produced from these two different methods are very similar. Coal in the pilot scale oven is heated from both vertical walls and the heated front moves towards the center of the charge. For the sole-heated oven, the charge is heated from the bottom and the heated front moves upward with time. Despite of the configuration of the pilot scale oven and sole-heated oven are very different, the Sole Heated Oven can be considered as half of the pilot scale oven with different orientation. There is some similarity between these two ovens in terms of heating experienced by the charge during carbonization. Moreover, semi-cokes produced in the sole-heated oven undergo re-heating in inert gas atmosphere prior to CSR and CRI measurement. The difference in heat treatment makes it difficult to directly compare the effect of heating profile on coke properties. Further research is needed prior to draw a definite conclusion. 3.2. Carbon form analysis on pilot-scale and sole-heated oven cokes Carbon form analysis was performed on seven coke samples from both the pilot-scale movable wall oven (A–G) and the corresponding sole-heated oven (A0 –G0 ). A summary of the carbon form analysis results is given in Table 4. The data in this table shows the total of each category, but for circular, lenticular and ribbon carbon

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T. MacPhee et al. / Fuel 114 (2013) 229–234 Table 4 Carbon form analysis results on selected cokes. Test

Oven

Isotropic (%)

Circular, %

Lenticular (%)

Ribbon (%)

Inert (%)

CMSI

Blend Ro

LV (%)

MV (%)

HV (%)

1

Pilot scale Sole-heated Pilot scale Sole-heated Pilot scale Sole-heated Pilot scale Sole-heated

4.62 2.94 4.78 5.32 5.23 5.20 4.78 4.19

41.30 43.24 32.02 32.41 35.23 35.40 34.27 39.16

21.20 21.76 26.12 25.57 30.23 34.16 15.73 16.01

14.67 14.12 13.20 15.19 9.77 7.67 12.36 13.79

18.21 17.94 23.88 21.52 19.55 17.57 32.87 26.85

2.77 2.71 2.87 2.84 2.71 2.69 2.73 2.70

1.12 1.13 1.15 1.14 1.12 1.12 1.11 1.11

19.4 18.6 19.6 19.7 12.7 11.3 18.8 19.9

24.4 25.1 32.1 32.3 37.0 39.5 23.0 20.9

56.2 56.3 48.3 48.3 50.3 49.3 58.1 59.3

Pilot scale Sole-heated Pilot scale Sole-heated Pilot scale Sole-heated

6.36 5.15 4.08 5.07 4.46 2.94

26.06 25.57 30.46 26.27 33.86 34.07

28.60 29.90 22.54 23.88 21.26 23.04

14.19 13.61 15.59 14.03 13.12 12.01

24.79 25.77 72.66 69.25 27.30 27.94

2.95 2.90 2.87 2.90 2.80 2.76

1.17 1.17 1.16 1.16 1.13 1.14

20.9 20.0 23.4 22.6 19.5 18.2

36.1 38.6 29.0 32.1 27.8 30.4

43.1 41.4 47.5 45.3 52.7 51.4

3 4 5 6 7

forms (binder phase), each of these contain subcategories based on size of the carbon form itself, i.e., fine, medium and coarse. For isotropic, very fine (incipient) is also included. Inerts (filler phase), are also classified by subgroups such as fusinite, semi-fusinite, and unidentified inerts along with other inerts, which are summed up in the table. Table 4 shows similar results obtained from both the pilot-scale movable wall oven and the Sole Heated Oven in terms of percent binder phase (reactive) and filler (inert) phase. The good relationship between percent binder phase present in sole-heated and pilot scale oven cokes is presented in Fig. 6. Also, the sole-heated and pilot scale oven cokes show excellent relationship for ‘effective coal blend reflectance, Ro’ as presented in Fig. 7. This further denotes the similarity of the cokes produced in both types of ovens.

1.17

Blend Ro-Pilot Scale Oven

2

1.16 1.15 y = 1.01x - 0.01 2 R = 0.96

1.14 1.13 1.12 1.11 1.10 1.10

1.11

1.12

1.13

1.14

1.15

1.16

1.17

Blend Ro-Sole Heated Oven 3.3. ASG analysis on pilot-scale and sole-heated oven cokes To develop a better understanding of the influence of different carbonization methods on the properties of the resulting coke, an analysis of coke ASG was also performed. As indicated in Table 5, ASG of sole-heated oven cokes are consistently higher than that of pilot oven cokes. In fact for the nineteen (19) cokes examined, ASG of sole-heated oven coke is, on average, about 6% higher than ASG of pilot oven cokes. This finding is mainly attributed to the fact that sole-heated oven cokes are produced under a constant load of 15.2 kPa, which is higher than the pressure exerted on the coal during carbonization in the pilot scale oven, 8 kPa.

Binder Phase-Pilot Scale Oven

85

80 y = 0.80x + 14.03 2

R = 0.68

75

Fig. 7. Effective coal blend Ro relationship between sole-heated oven and pilot scale oven cokes.

Table 5 Comparison of ASG in pilot scale and sole-heated oven. Test no.

Pilot scale oven

Sole heated oven

% Difference

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

0.94 0.92 0.94 0.92 0.93 0.92 0.92 0.95 0.95 0.95 0.93 0.95 0.93 0.92 0.94 0.96 0.93 0.95 0.93

0.99 0.98 0.99 0.98 0.97 0.97 0.99 1.02 1.00 1.02 0.96 1.02 0.97 0.99 1.01 1.01 0.99 1.00 0.99

5.7 5.8 5.0 5.9 3.7 4.9 7.0 6.3 4.7 5.5 2.7 6.3 4.2 7.3 6.9 5.3 6.5 5.6 6.1

70

65 65

70

75

80

85

Binder Phase-Sole Heated Oven Fig. 6. Binder phase (reactive) relationship between sole-heated oven and pilot scale oven cokes.

Nomura et al. [13] stated that the factors determining coke reactivity are carbon structure, catalyst and pore structure. As shown in the above the carbon form analysis, the carbon structure of sole-heated oven cokes and pilot oven cokes are similar. Also, the ash chemistries of the corresponding cokes are identical since

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they are produced from the same coal blend. Because of the difference in ASG, one might expect the pore structure of the sole-heated oven cokes and pilot oven cokes are different and CRI is affected by this difference. However, as shown in Table 3, the difference in measured CRI between the sole-heated oven cokes and pilot oven cokes are small and within the repeatability as stated in ASTM D5341-99 (2010) Standard. The observed similarity between sole-heated oven cokes and pilot oven cokes suggest the dependence of CRI on ASG is relatively weak when compared with other factors. The small difference in ASG resulting from the two coke preparation methods employed in this work is not significant enough to cause noticeable impact on CRI.

4. Conclusions This paper describes the development of a novel procedure at CanmetENERGY for the evaluation of coke CSR using a small-scale carbonization oven – the sole-heated oven. A comparison between cokes produced in a sole-heated oven using the method developed in this work and those formed in a pilot-scale coke oven found the following: 1. CSR’s and CRI’s determined are very similar. 2. ASG’s for sole-heated oven cokes are higher on account of the higher pressure (load) applied on the coal bed. 3. Carbon forms expressed as binder phase (reactive) and filler phase (inert) are similar. 4. This procedure finds useful applications as a preliminary evaluation method and a reliable screening tool in both the cokemaking and coal mining industry as it provides relevant information on (i) Coking potential/ability of coal/coal blends. (ii) CSR evaluation. (iii) Carbon form development prior to designing and running pilot oven trials.

Acknowledgements The authors would like to thank the Canadian Carbonization Research Association for supporting this work. They are grateful to CanmetENERGY personnel for their excellent contribution to the experimental work and for generating the data presented in this paper. They also thank Drs. John Price and John Gransden for their review of this paper and for providing constructive comments. References [1] Statistic archive, World Steel Association. [retrieved 21.02.11]. [2] Statistic archive, World Steel Association. [retrieved 21.02.11]. [3] Geerdes M, Toxopeus H, van der Vliet C. Modern blast furnace ironmaking – an introduction. Verlag Stahleisen GmbH; 2004 [chapter 4]. [4] Ida S, Nishi T, Nakama H. Behaviour of burden in the Higashida No. 5 blastfurnace. J Fuel Soc Jpn 1971;50:645–54. [5] Leeder WR, Price JT, Gransden JF. In: ISS-AIME ironmaking conference proceedings, vol. 59; 2000. p. 55–65. [6] Lee W, Lee Y. Internal gas pressure characteristics generated during coal carbonization in a coke oven. Energy Fuel 2001;15:618–23. [7] Grigore M, Sakurovs R, French D, Sahajwallah V. Effect of carbonisation conditions on mineral matter in coke. ISIJ Int 2007;47(1):62–6. [8] Sakurovs R, French D, Grigore M. Effect of the NSC reactivity test on coke mineralogy. mineralogy. Int J Coal Geol 2012;94:201–5. [9] Price JT, Gransden JF. Metallurgical coals in Canada: resources, research, and utilization. Canmet Report 87-2E; 1987. [10] Gray RJ, DeVanney KF. Coke carbon forms: microscopic classification and industrial applications. Int J Coal Geol 1986;6:277–97. [11] Coin CDA. Microtextural assessment of metallurgical coke. BHP Central Res Lab. CRL/TC/41; 1982. [12] Loison R, Foch P, Boyer A. COKE quality and production. Butterworths; 1989. ISBN 0-408-02870-X. [13] Nomura S, Ayukawa H, Kitaguchi H, Tahara T, Matsuzaki S, Naito M, et al. Improvement in blast furnace reaction efficiency through the use of highly reactive calcium rich coke. ISIJ Int 2005;45(3):316–24.