Metallurgical Coke

Steel Industry
Met coke plays an indispensable role in the steel industry, where it is used in the blast furnace process to produce iron and steel. During this process, Met coke serves as both a reducing agent and a source of energy. As it reacts with iron ore, it reduces the iron oxides, liberating molten iron and producing carbon dioxide gas. This reduction process is vital to obtain crude iron, which later undergoes further refining to produce steel. The quality and properties of Met coke significantly influence the efficiency, productivity, and overall cost of steel production.

Beyond Steel - Non-Ferrous Metals and Smelting Processes
Met coke finds applications beyond the steel sector in the production of non-ferrous metals like aluminum, titanium, and silicon. In smelting processes, such as aluminum smelting, Met coke serves as a reducing agent to convert metal oxides into their elemental forms. This ensures the extraction of pure metals from their ores, facilitating the manufacturing of various non-ferrous metal products. Its exceptional reducing capabilities and stability in high-temperature environments make Met coke a preferred choice in these critical processes.

Foundry Industry and Casting Processes
In the foundry industry, Met coke is extensively used in casting processes. Its uniform heat distribution ensures consistent melting of metals, promoting the production of high-quality castings. Moreover, Met coke's ability to reduce impurities in the molten metal enhances casting precision and reduces the likelihood of defects. Foundries rely on Met coke for its reliability and the excellent surface finish it imparts to the final products.

Chemical Industry
A Versatile Reducing Agent: Met coke plays a crucial role in the chemical industry as a potent reducing agent. It finds application in various chemical reactions, especially in the synthesis of chemicals like calcium carbide and calcium cyanamide. Its capacity to donate electrons during chemical transformations is pivotal in these reactions, leading to the production of essential organic compounds.

Metallurgical coke is a porous, fissured, silver-black solid and is an important part of the ironmaking process since it provides the carbon (C) and heat required to chemically reduce iron burden in the blast furnace (BF) to produce hot metal (HM). It is a porous C material with high strength produced by carbonization of coals of specific rank or of coal blends at temperatures around 1100 deg C in coke ovens. It is composed of both the organic and inorganic matter. C is the major component of the organic part. Small amounts of sulphur (S), nitrogen (N2), hydrogen (H2) and oxygen (O2) also occur in the organic part. The inorganic matter in coke is called coke ash (mineral matter) and is typically around 12 % on dry basis. Both the organic and inorganic components influence coke reactivity. Thus, coke characterization is an important aspect to understand the quality of coke formed.

The basic understanding of coke quality is an important task as it determines the high temperature and gasification behaviours of coke in the blast furnace (BF). As the coke moves towards the lower zones of BF, it degrades and generates fines, which affects the bed permeability and the process efficiency. Hence, superior coke quality is critical for a stable and efficient BF operation.

Coke quality is influenced by many factors such as the rank, the maceral composition (leading to isotropic or anisotropic coke structures), the ash composition and the fluidity of the starting coals, the carbonization conditions including peak temperature, heating rate, particle size, pressure and bulk density as well as heat treatment conditions.

The important properties of coke, including mechanical strength and reactivity, are governed by the arrangement of the constituent C atoms. The principal features of the atomic arrangement are the alignment and size of C crystallites. The size of textural components is regarded as indicative of their chemical reactivity.

Microscopically coke consists of a solid matrix, organic and inorganic inclusions in the matrix, pores and rnicro-fissures. The processes of the development of the porous structure and the micro-texture of coke take place essentially within the plastic range. The structure formed in the coke by the gas bubbles occupies almost half its volume and influences two properties of coke, the mechanical strength and the bulk density. The solid material forming the pore walls consists of optically-anisotropic entities which are usually observed using polarized light microscopy (PLM). The coke micro-texture influences the coke properties which are essential for its use in the BF. 

Pore structure development
The pore structure of coke is largely determined within the plastic temperature range of the carbonization process. During carbonization, initially pores appear in large particles at a temperature near the softening point, while the medium size particles become porous at higher temperatures. No pore formation is normally detected at any temperature within particles < 125 microns in size. An increase in temperature induces an increase both in the number and the size of pores, and more particles are observed to have pores with the larger particles becoming multi-pored. With increasing temperature, particles become more rounded and swell into the inter-particulate voids. The pore structure of metallurgical coke can vary greatly over a wide range. Within a given coke and between one coke and another coke, the individual pores can vary both in size and in shape. A classification of pores on the basis of their average width was proposed in 1967 and subsequently adopted by IUPAC in 1972. As per this classification, there are three types of pores namely (i) micro-pores (less than 2 nm), (ii) meso-pores (less than 2 nm to less than 50 nm) and macro-pores (greater than 50 nm). The micro-pore size range has been further subdivided into the very narrow ultra-micro-pores (less than 0.5 nm) and super-micro-pores (greater than 1 nm to less than 2 nm). However, coke structure is dominated by large pores (greater than 2 nm) namely meso-pores and the remainder appears relatively dense and smaller than 0.5 nm to1 nm. Higher micro-pore surface area of coke is frequently related to higher anisotropic C content.

Coke ash
Coke ash is the mineral matter present in the coke. Metallurgical coke typically contains around 8 % to 12 % of mineral phases. The proportion of individual minerals present in coke can vary from coke to coke depending on the mineralogy of the original coals as well as the process conditions employed for carbonization. During carbonization, some minerals decompose and some undergo a number of complex reactions, all of which contribute to the formation of new crystalline minerals as well as amorphous phases. X-ray diffraction analysis is normally used to identify and quantify the mineral phases present in the metallurgical coke. For X-ray diffraction analysis, a sample of the mineral matter from the coke is prepared by ‘low temperature radio-frequency plasma ashing’ (LTA) as this technique results in minimal alteration of the mineral matter. Most of the mineral matter present in the coke has been found to be present as an amorphous phase (greater than 50 % in LTA samples). Partially decomposed clays and other material which become structure-less on heating due to the removal of constitutional water or other volatiles are responsible for the formation of amorphous alumino-silicate material. With the exceptions of some artifacts or hydrated minerals such as bassanite, coquimbite and jarosite, the major mineral matter in crystalline phases identified in the metallurgical coke are quartz, mullite, fluorapatite, and pyrrhotite. Metallic iron (Fe), brookite, anatase, rutile, cristobalite, iron oxides (Fe3O4, Fe2O3 and FeO), akermanite and oldhamite are common minerals present in coke.

The company now has 2 modern production workshops and 2 large storage workshops, which can meet the needs of large-scale production and fast logistics. The annual production volume has reached 100,000 tons. After years of hard work, we have worked closely with many domestic companies and exported to many countries and regions. In the future, the company will continue to adhere to the business philosophy of "quality-oriented, honesty and trustworthiness", continuously improve product quality and service level, carry out extensive cooperation and exchanges with domestic and foreign companies, and jointly promote the development of the carbon industry.