Description:TECHNICAL FIELD
The present disclosure generally relates to the field of metallurgy. Particularly, the present disclosure relates to a simple and efficient method for manufacturing metallurgical coke which employs cheaper and environmentally friendly biomass without deterioration of the coke quality. The method comprises steps of crushing the biomass, combining the crushed biomass with metallurgical coal and coal tar to form a blend, and carbonizing the blend to produce high-strength metallurgical coke. The present disclosure also relates to the high-strength metallurgical coke obtained thereof.

BACKGROUND OF THE DISCLOSURE
The term “biomass” refers to living matter formed by photosynthesis, for example plants, trees, grasses etc., as well as materials and wastes derived from living sources including animals and humans. Biomass derived from waste include municipal wastes, wastes from agriculture, forestry, construction, and human and animal habitat. About 686 MT gross biomass residue is available in India on an annual basis. Out of this, about 545 MT is contributed by cereals, oilseed, pulses and sugarcane crops put together; about 61 MT by horticultural crops and about 80 MT by others.

The chemical composition of biomass can be characterized by five primary components: cellulose, hemicellulose, lignin, extractives/volatiles, and ash. Cellulose is a polysaccharide of glucose monomers held together by ß(1?4) linkages. Hemicellulose is an amorphous heteropolymer comprised of several different carbohydrates including xylose, mannose, and glucose. Lignin is an amorphous, irregular three-dimensional, and highly branched phenolic polymer intertwined with cellulose and hemicellulose fraction of the biomass structure. This interwoven nature of the lignin helps provide rigidity to lignocellulosic materials, such as trees. The other minor components of biomass are extractives/volatiles and ash. The extractives/volatiles include both water and ethanol solubles. Water-soluble compounds include non-structural sugars and proteins, and ethanol-soluble components include chlorophyll and waxes. Ash constitutes the inorganic content in biomass and can be intrinsic or due to contamination during harvesting. Intrinsic ash includes material-like calcium and potassium ions, while anthropogenic ash is mostly silica or dirt collected during harvest.

Coke contributes around half of the cost of hot metal. Studies are being conducted on the use of cheaper carbonaceous materials to reduce the cost of hot metal. Use of biomass as a cheaper alternative energy resource has attracted a lot of interest since it is carbon neutral. Also, since biomass is considered carbon neutral, there will be a carbon credit benefit from using biomass. Woody chips, which are by-products of sawmills and the construction industry, are currently being employed as a source of energy for power generation and other purposes. However, the main problem with using biomass in manufacturing coke is that it has a lower density, a greater volatile matter content and a higher oxygen content. Hence, as a result of using biomass in coke making, the coke strength after reaction (CSR) deteriorates.

Further, prior art teaches using biomass in coke making in the form of briquettes or as charcoal. However, use of briquettes is associated with common challenges such as poor efficiency and difficulty in handling and biomass charcoal drastically deteriorates coke properties, and are hence not recommended.

Accordingly, there is a need in the art for providing simple and efficient methods of manufacturing metallurgical coke by utilizing biomass, and coke thereof, without deterioration of the coke quality.

SUMMARY OF THE DISCLOSURE
The present disclosure relates to a method for manufacturing metallurgical coke comprising steps of:
(a) crushing biomass,
(b) combining the crushed biomass with metallurgical coal and coal tar to form a blend, and
(c) carbonizing the blend to produce high-strength metallurgical coke.

In some embodiments, the crushed biomass has a size ranging from about 200 microns to about 600 microns.

In some embodiments, the blend comprises about 93.8% to about 96.2% of the at least one metallurgical coal, about 3% to about 5% of the crushed biomass and about 0.8% to about 1.2% of the binder.

The present disclosure also relates to the metallurgical coke obtained by the method of the present disclosure by utilizing biomass without deterioration of the coke quality.

In some embodiments, the metallurgical coke of the present invention has a CSR ranging from about 45 to about 66.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figure together with a detailed description below, is incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure where:

Figure 1 depicts the results of the thermogravimetric analysis (TGA) of biomass employed in the examples.

DETAILED DESCRIPTION OF THE DISCLOSURE
In view of the drawbacks associated and to remedy the need created by the art, the present disclosure aims to provide a high-strength metallurgical coke and a simple, economical and efficient method of manufacturing the same by employing biomass.

However, before describing the disclosure in greater detail, it is important to take note of the common terms and phrases that are employed throughout the instant disclosure for better understanding of the technology provided herein.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity. The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results. Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising” or “containing” or “has” or “having” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

As used herein, the term "method" and “process” are employed interchangeably.

As used herein, the term "metallurgical coke" and “coke” are employed interchangeably and refer to the product obtained by the method of the present invention post coking. Coke is an essential fuel and reactant in the blast furnace process for primary steelmaking.

As used herein, the term "metallurgical coal", “coal”, “base blend” and “coal base blend” are employed interchangeably and refer to a grade of coal that can be used to produce good-quality coke. The ash, moisture, sulphur and phosphorus content of metallurgical coal is low, and its rank is usually bituminous.

As used herein, the term "about" means to be nearly the same as a referenced number or value. As used herein, the term "about" should be generally understood to encompass ± 10% of a specified amount or value.

The present disclosure relates to a method of manufacturing high-strength metallurgical coke by utilizing biomass, and the coke obtained thereof. The present disclosure allows utilizing biomass for metallurgical coke making without deterioration of coke properties.

Generally, biomass has lower density and higher volatile matter content. So, addition of biomass in coal deteriorates its coking property therefore also reduces coke properties. So, in order to efficiently utilize biomass, the present disclosure provides a method wherein the biomass is suitably utilized and employed in the sequence of steps in the manufacture of coke. In some embodiments, the present disclosure utilizes biomass efficiently by employing a pre-carbonization technique. Particularly, the pre-carbonization technique involves selectively crushing biomass separately in a specific size range and then mixing it with the metallurgical coal/coal base blend.

In some embodiments, the optimum size range of biomass to which it should be crushed for using effectively in coke making is subject to variation based on the nature of biomass and metallurgical coal employed. The size is optimised to ensure that a uniform and homogenous mixture is obtained upon mixing the biomass with the metallurgical coal. In an exemplary and non-limiting embodiment of the present disclosure, the selective crushing is conducted to obtain biomass in the size range of about 200 micron to about 600 micron.

The method of the present disclosure also employs an additive obtained as a by-product from coke oven/plant. In particular, the method of the present disclosure employs coal tar as an additive/binder. Employing coal tar in the method of the present disclosure surprisingly improves the quality of coke obtained, despite use of biomass in the method.

The present disclosure relates to a method for manufacturing metallurgical coke comprising steps of:
(a) crushing biomass,
(b) combining the crushed biomass with metallurgical coal and coal tar to form a blend, and
(c) carbonizing the blend to produce high-strength metallurgical coke.

In an embodiment of the present disclosure, the crushed biomass employed in the method has a size ranging from about 200 microns to about 600 microns.

In some embodiments of the present disclosure, the biomass is crushed by any suitable technique known in the art including but not limiting to employing a jaw crusher and/or a drum mill. The product is then sieved to a specific size range. The specific size range has chosen so that it can be mixed homogeneously with coal

In another embodiment of the present disclosure, the content of volatile matter in the biomass is ranging from about 55% to about 70%.

In yet another embodiment of the present disclosure, the blend comprises about 93.8% to about 96.2% of the at least one metallurgical coal, about 3% to about 5% of the crushed biomass, and about 0.8% to about 1.2% of the binder.

In yet another embodiment of the present disclosure, the blend further comprises an aqueous solvent.

In still another embodiment of the present disclosure, the blend is formed into a cake prior to carbonization.

In still another embodiment of the present disclosure, the carbonization is carried out under stamp charging conditions.

In still another embodiment of the present disclosure, the carbonization is carried out in furnace selected from recovery furnace or non-recovery furnace.

In still another embodiment of the present disclosure, the carbonization is carried out at a temperature ranging from about 1050 °C to about 1150 °C for a period of about 4.5 hours to about 5.5 hours.

In still another embodiment of the present disclosure, the metallurgical coke is subjected to cooling post carbonization.

In some embodiments, the cooling of the coke post carbonization is carried out at a temperature ranging from about 1000 to about 80 °C.

In still another embodiment of the present disclosure, the coke strength after reaction (CSR) of the metallurgical coke is ranging from about 45 to about 66.

In some embodiments of the present disclosure, the method for manufacturing the metallurgical coke comprises steps of:
(a) optionally characterising/screening biomass,
(b) selectively crushing the biomass to obtain crushed biomass of a specific size/fraction so that it can be mixed homogeneously with metallurgical coal,
(c) combining the crushed biomass with metallurgical coal and coal tar, and optionally mixing, to form a blend,
(d) carbonizing the blend to produce high-strength metallurgical coke, and
(e) optionally cooling the metallurgical coke.

In some embodiments, the biomass is characterized/screened prior to use by techniques selected from a group comprising but not limiting to proximate analysis, ultimate analysis and thermogravimetric analysis or any combination thereof.

In some embodiments of the present disclosure, the biomass is characterised to assess the feasibility of its use in the method of the present disclosure. In an exemplary and non-limiting embodiment of the present disclosure, the volatile matter content of the biomass employed is ranging from about 55% to about 70%.

In some embodiments, suitable solvents such as but not limiting to water is added to the coal blend (comprising metallurgical coal, crushed biomass and coal tar) to obtain the desired value of moisture content. In some embodiments, a coal cake is made inside a cardboard box with the desired density. Before charging the coal cake into the oven, it was ensured that the empty oven temperature is 900±5°C. In some embodiments of the present disclosure, the carbonization is carried out under stamp charging conditions in a suitable furnace such as a recovery or non-recovery furnace. In an exemplary and non-limiting embodiment, the carbonization was carried out in a Carbolite oven. After about 4.5 to about 5.5 h of carbonization time, the hot coke is pushed out and quenched with water. The coke samples are tested for coke strength after reaction (CSR) and CRI (coke reactivity indices).

In some embodiments, the biomass employed in the method of the present disclosure has a low ash content and high volatile matter content. In some embodiments, the biomass employed in the method of the present disclosure has high carbon, oxygen and hydrogen content, and lower amounts of nitrogen and sulphur (if present).

In some embodiments, the biomass employed in the present disclosure includes but is not limited to materials and wastes formed/derived/obtained by plants, trees, grasses, animals including humans, etc. In an exemplary and non-limiting embodiment of the present disclosure, the biomass employed in the present disclosure includes biomass feedstocks such as but not limiting to energy crops, agricultural crop residues, forestry residues, algae, wood processing residues, wastes, etc. In another exemplary embodiment of the present disclosure, biomass derived from waste include wastes from agriculture, forestry, construction, industry, urban wood waste, human and animal habitat, food wastes, municipal wastes etc. In another exemplary and non-limiting embodiment, the biomass may be obtained from energy crops such as but not limiting to switchgrass, miscanthus, bamboo, sweet sorghum, kochia, wheatgrass, fast-growing hardwood trees etc. In another exemplary and non-limiting embodiment, the biomass may be obtained from agricultural crops or crop residues (which include the stalks, leaves, husks, cobs, straw, stubble etc.) such as but not limiting to cereals (such as wheat, oat, barley, sorghum, rice, corn etc.), pulses, oilseed, sugarcane, etc.

The present disclosure also relates to a metallurgical coke obtained by the method of the present disclosure. The metallurgical coke has high-strength and a CSR ranging from about 45 to about 66.

In still another embodiment of the present disclosure, the coke reactivity index of the metallurgical coke is ranging from about 25 to about 33, preferably about 28 to about 29.

The use of coal tar and biomass along with the metallurgical coal in the present disclosure has a synergistic effect.

In some embodiments, studies have been made in 7kg Carbolite oven by using different amount of biomass crushed in different size and using different percentage of additives. Resultant coke was then characterized for CSR value.

In some embodiments, the method of the present disclosure provides for use of as high as about 3-5 wt.% of biomass for metallurgical coke making without deterioration of coke properties.

In some embodiments, use of biomass alone resulted in deterioration of coke CSR due to lower density and higher volatile matter of biomass. However, addition of crushed biomass along with the additive coal tar did not result in deterioration of the coke properties up to 5 % of biomass.

In some embodiments, use of about 0.8% to about 1.2% of coal tar as binder improves the properties and strength of the coke without resulting in swelling of the coal cake (which could otherwise be detrimental for coke ovens/furnaces).

In some embodiments, the base blend employed in the examples has been taken as reference similar to commercial blend. The base blend that can be employed in the present invention is not limited or restricted to the same and can be suitably varied to use any suitable metallurgical coal or blend thereof. In an exemplary and non-limiting embodiment of the present disclosure, the base blend comprises metallurgical coal. The metallurgical coal may be crushed before carbonization as per established practice in stamp charge (such as but not limiting to about 90% below 3.15 mm and about 50% below 0.5 mm).

In an exemplary embodiment, advantages of the method of the present disclosure and the metallurgical coke produced thereof include but are not limited to:
- Provides a simple, cost-effective, scalable and efficient means for utilizing biomass for manufacturing high-strength metallurgical coke without deterioration of coke properties.
- Employs cheaper raw materials, viz., biomass (including biomass wastes), and coal tar which is a by-product from coke plant. Use of waste materials and industrial by-product further aids in recycling the same and improving the ecological footprint of the method.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

Any possible combination of two or more of the embodiments described herein is comprised within the scope of the present disclosure.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

Further, while the instant disclosure is susceptible to various modifications and alternative forms, specific aspects thereof has been shown by way of examples and drawings and are described in detail below. However, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention.

EXAMPLES:
The following illustrations in form of examples are described to bring more clarity of the invention and should not be considered as limitation or drawback of the invention.

Materials and Methods:
Biomass: Bamboo waste was collected and employed as the source of biomass in the following examples. Notwithstanding the same, the method of the present invention is not restricted to the said biomass and can be carried out by employing any alternate biomass.

Ash determination: Ash content was determined by following ASTM standard D 3174-11. 1 gm of 250 mm size sample was taken to a weighed capsule. Then the sample was placed in a cold muffle furnace and heated gradually at such a rate that the temperature reached 450°C to 500°C in 1 hr. At the end of 2 hr, the temperature reaches 950°C. Post cooling, the weight of the sample was measured, and ash was calculated by weight difference.

VM determination: Volatile matter (VM) content was determined by following ASTM standard D 3175-11. 1 gm of 250 mm size sample was taken in a covered platinum crucible and heated in a furnace at 950°C for 7 min. The VM was calculated by weight difference.

Ultimate Analysis: Ultimate analysis of sample was carried out by standard protocol described in ASTM D3176 to determine the carbon, hydrogen, oxygen, nitrogen, and sulphur in the material.

Thermogravimetric analysis (TGA): Thermogravimetric analysis (TGA) is one of the most common techniques used to investigate thermal events and kinetics during pyrolysis of solid raw materials such as coal. It provides a measurement of weight loss of the sample as a function of time and/or temperature. Thermogravimetric analysis of the biomass sample was performed using a TG apparatus. A total of about 15 mg of the sample was placed on a platinum cell. Then, the electric furnace was closed and purged with Ar with a flow rate of 100 ml/min and a pressure of 0.5 bar. The furnace was heated from ambient temperature to 1100 °C, with a heating rate of 3 °C/min. It records the weight loss of the sample with temperature.

Coke Strength after Reaction (CSR) and Coke Reactivity Indices (CRI): CSR and CRI were determined by following the NSC method. 200 g of coke of about 19-21 mm size was heated in a reaction tube (78 mm diameter X 210 mm length) at 1100°C for two hours during which CO2 was passed at 5 l/min. The percentage loss in weight of coke during the above reaction was reported as the reactivity (CRI). The reacted coke was placed in an I-type drum (no lifters) and subjected to 600 revolutions in 30 minutes. The percent of carbon material removed from the drum that is +10 mm is known as the coke strength after reaction (CSR).

Vertical and lateral expansion: For lab scale carbonization test, a measured coal cake has been prepared with a dimension of 335 mm, 270 mm, 90 mm. The complete cycle of carbonization is kept as 5 hrs. After 3 hrs of reaction the thickness of the cake has been measured vertically and laterally. The differences of dimensions give vertical and lateral expansion.

Example 1: Methodology of Coke making
Example 1(A): Characterisation of biomass
Biomass (bamboo waste) was collected and subjected to characterisation studies, viz., proximate analysis, ultimate analysis and thermogravimetric analysis.

The volatile matter (VM) and ash content of the biomass was determined by proximate analysis. The composition of the biomass in wt.% of carbon, hydrogen, nitrogen, sulphur and oxygen was determined by the ultimate analysis. TGA analysis was conducted to understand the high temperature properties of the biomass. The results of the proximate and ultimate analysis of biomass are provided in Table 1, and the results of the thermogravimetric analysis are depicted in Figure 1. The biomass was found to be suitable to be employed in the manufacture of metallurgical coke.

Table 1: Properties of biomass

Parameters Proximate Analysis
dry basis (db) % Ultimate Analysis
wt %
Ash VM C H N S O
Biomass 15.97 65.70 39.4 5.44 0.44 0.14 36.0

Example 1(B): Crushing biomass
Post completion of the characterization studies, 5kg of as-received biomass was crushed to a size of =1000 micron in a jaw crusher. The product obtained was then sieved in different ranges and the product obtained in the range of -600 to + 200 micron was taken for coke making. The specific size range of the crushed biomass particles was selected post different iterations to ensure that the biomass is homogeneously mixed with coal or coal base blend during the process of manufacturing the coke.

Example 1(C): Carbonization and preparation of metallurgical coke
A coal base blend was prepared similar to a commercial blend. Table 2 shows the typical properties of blend. The coal was crushed before carbonization, wherein the crushing fineness was about 90% below 3.15 mm.

Table 2: Typical blend properties
Sample Ash VM
Base blend About 12.40 About 24.65

The biomass was then taken as a blend component. The crushed biomass of Example 1(B) was combined with the coal base blend along with coal tar (additive), to obtain a homogenised blend. Water was added to the homogenised blend to obtain the desired value of moisture content (about -9-10%). A coal cake was made using the resultant blend inside a cardboard box keeping bulk density of about 1150 kg/m3.

A series of carbonization tests were carried out with the homogenised blend having different quantity of biomass, in a 7 kg Carbolite oven, under stamp charging conditions. The empty oven temperature was checked before charging the coal cake into the oven, to ensure it is 900±5°C. After about 5 h of carbonization time, the hot coke was pushed out and quenched with water. The coke samples were tested for coke strength after reaction (CSR) and coke reactivity indices (CRI).

The results obtained are depicted in Table 3. Initially, the test was carried out with the base blend alone (blend no. 1). Blend nos. 2-4 contained different quantity of crushed biomass ranging from about 3-7 % along with 1 % of additive coal tar. No deterioration of the coke properties was observed in the blend comprising up to about 5 % of biomass.

Table 3: Composition of blend and coke properties
Blend no. 1 2 3 4

Component, wt. % Base blend
100 96 94 92
Biomass (crushed in specific size) 0 3 5 7
Coal tar 0 1 1 1
CSR 49.7 49.6 47 45.8

Example 2: Coke made of blend comprising biomass in absence of coal tar
A series of carbonization tests were designed as per the protocol of Example 1(C), with blends comprising different quantity of biomass ranging from 3-10 wt. % in absence of coal tar. The results obtained are depicted in Table 4. Initially, the test was carried out with the base blend alone (Blend no. 1). The Blend nos. 2-5 were designed to further comprise different quantity of biomass in the range of 3-10 wt. %. It was found that addition of the biomass resulted in deterioration of coke CSR. This was expected due to the lower density and higher volatile matter of biomass. However, addition of biomass crushed in a specific size range used in conjunction with coal tar alleviated this drawback, as no deterioration of the coke properties was observed upon use of up to 5 wt % of biomass (see Table 3).

Table 4: Composition of comparative blend and coke properties
Blend no. 1 2 3 4 5
Component, wt. % Base blend 100 97 95 93 90
Biomass 0 3 5 7 10
CSR 49.7 47 43.5 43.8 35.8
Coke ash, db 16.2 16.7 16.5 16.8 16.8

Example 3:
With the addition of coal tar, there is an increase in coal cake swelling, which can be detrimental for coke ovens. A series of lab scale study was carried out to optimise the percentage of coal tar employed in the coal blend. Coal tar was used in different fractions ranging from about 0.5 to about 3 wt.% in the coal blend of Example 1(C). Lateral and vertical swelling of the coal cake was measured in each case to understand the swelling of coal cake and its effect on oven wall. The impact of addition of coal tar on CSR and swelling has been tabulated in Table 3. Hence, based on coke properties and oven health the percentage of coal tar has been optimized.

Table 3: Impact of addition of coal tar on CSR and swelling
Coal Tar, wt. % CSR improvement Swelling
0.5 No No
0.7 No No
1 Yes No
1.5 yes Slight
2 Yes High
2.5 Yes High

Claims:1. A method for manufacturing metallurgical coke comprising steps of:
(a) crushing biomass,
(b) combining the crushed biomass with metallurgical coal and coal tar to form a blend, and
(c) carbonizing the blend to produce high-strength metallurgical coke.

2. The method as claimed in claim 1, wherein the crushed biomass has a size ranging from about 200 microns to about 600 microns.

3. The method as claimed in claim 1, wherein content of volatile matter in the biomass is ranging from about 55% to about 70%.

4. The method as claimed in claim 1, wherein the blend comprises about 93.8% to about 96.2% of the at least one metallurgical coal, about 3% to about 5% of the crushed biomass, and about 0.8% to about 1.2% of the coal tar.

5. The method as claimed in any of the preceding claims, wherein the blend further comprises an aqueous solvent; wherein the blend is formed into a cake prior to carbonization.

6. The method as claimed in any of the preceding claims, wherein the carbonization is carried out under stamp charging conditions; and wherein the carbonization is carried out in a recovery furnace or a non-recovery furnace.

7. The method as claimed in any of the preceding claims, wherein the carbonization is carried out at temperature ranging from about 1050 °C to about 1150 °C for a period of about 4.5 hours to about 5.5 hours.

8. The method as claimed in any of the preceding claims, wherein the metallurgical coke obtained in step c) is subjected to cooling.

9. The method as claimed in any of the preceding claims, wherein the coke strength after reaction (CSR) of the metallurgical coke is ranging from about 45 to about 66.

10. A metallurgical coke obtained by the method as claimed in any of the preceding claims, having CSR ranging from about 45 to about 66.