Production of High-Strength Coke from Low-Quality Coals Chemically Modified with Thermoplastic Components

Abstract

In order to produce high-strength coke from low-quality coals, noncovalent bonds between O-functional groups in coal were cleaved by pyridine containing HPC pyridine soluble and HPC-derived thermoplastic components were introduced into the pores formed by swelling; thus, the synergistic effect during carbonization of the suppression of cross-linking reactions and the fluidity amplification due to close placement of coal and thermoplastic components was investigated. When HPC was extracted with pyridine, a decrease in O-functional groups was observed in the pyridine-soluble and pyridine-insoluble components. When HPC was extracted with MeOH, on the other hand, O-functional groups in HPC selectively moved into the soluble components. When non-or slightly-caking coal was chemically-modified with the prepared HPC pyridine-soluble components by utilizing the solvent-swelling effect of pyridine, the fluidity improved compared with the coals physically mixed with the soluble components or HPC. On the other hand, the fluidity of the chemically-modified sample with the MeOH-soluble components hardly changed from that of the original sample, and no effect of the modification with the thermoplastic component was observed. Furthermore, it was clarified that higher-strength coke can be produced from the chemically-modified sample with the HPC pyridine-soluble components than from the original coal or the physically mixed coal with the soluble components. The contraction behavior during carbonization of the chemically-modified sample with the soluble components and that of the original coal was investigated; as a result, a large difference was not observed between these two. Thus, it was found that high-strength coke can be produced from low-quality coals by the present method.

Influence of Heating Conditions on the Strength of Coke Produced from Slightly-Caking Coal Containing Chemically-Loaded Thermoplastic Components

“…As is well-known, although HPC consists of hundreds to thousands of molecular weights, 18) HPC pyridine soluble is composed with lower molecular weight than original HPC, because DTG curve of the soluble gave the main peaks at around 250 and 450°C (HPC also provides the main peaks at same temperatures), and the former peak does not observed for HPC pyridine insoluble. 5) In addition, it was found that the interaction of HPC pyridine soluble and coal occurs during heat treatment of chemically loaded coal prepared by this method. Now, although we cannot obtain the direct evidence of HPC pyridine soluble introduced into coal structure produced during solvent swelling, the lighter component in the prepared HPC pyridine soluble may be loaded into coal structure.…”

“…In particular, it was demonstrated that coke manufactured from a specially-prepared input material -in which pyridine-soluble HPC components are chemically loaded into the coal pores produced by pyridine treatmentis stronger than that produced from the unloaded raw coal. 5) This result was attributed to a synergistic interplay of two mechanisms: (a) pyridine-induced cleavage of noncovalent bonds between O-functional groups in coal, and (b) suppression of cross-linking reactions during carbonization, and amplification of fluidity due to increased proximity between coal and thermoplastic components, resulting from the introduction of HPC-derived thermoplastic components into the pores produced by pyridine-induced swelling.…”

“…The detailed procedure was as reported in Ref. 5. HPC was first extracted by pyridine at room temperature, then coal was added to a solution of pyridine-soluble HPC and stir at room temperature for 24 h to achieve swelling and loading of the pyridine-soluble components.…”

“…Results of thermogravimetric analysis indicate that low-molecular-weight components is more abundant in HPC pyridine-soluble than in the pyridine-insoluble, whereupon it is hypothesized that softening also begins to occur at low temperatures. 5) It is possible that, by chemically-loading HPC pyridine-soluble components -in which low-molecular-weight components are plentifulnot only amplify the initial mobile components of TA but also contribute to the dissolution of immobile components at later stages, resulting in improved fluidity and greater coke strength. On the other hand, the pyridine-insoluble components are present in abundance in high-mass components of HPC, and the higher temperatures at which the fluidity region occurs ensure that the types of continuous dissolution phenomena envisioned by the continuous self-dissolution model are not occurring in this case; consequently, the total fluidity is low (because the components that soften at early stages are insufficiently abundant), ensuring that the coke is of lower strength than that produced from coal in which the soluble components are loaded.…”

Influence of Additive Amount and Heating Conditions on the Strength of Coke Prepared from Non-Caking Coal

“…In particular, we demonstrated that coke manufactured from a specially-prepared input material -in which HPC pyridine-soluble components are chemically-loaded into the pores produced by pyridine treatment of coal -is stronger than that produced from the unloaded input material. 8,9) We attributed this result to a synergistic interplay of two mechanisms: (a) pyridine-induced cleavage of noncovalent bonds between O-functional groups in coal, and (b) suppression of cross-linking reactions during carbonization and amplification of fluidity due to increased proximity between coal and thermoplastic components, resulting from the introduction of HPC-derived thermoplastic components into the pores produced by pyridine-induced swelling. 8,9) In addition, we showed that the extent of the improvement in strength is greater for formed coke.…”