Influence of biomass on metallurgical coke quality

Two industrial coal blends used in coke making were subjected to tests in order to assess the influence of waste sawdust (SC2 from chestnut and SP1 from pine) on the quality of the coke produced. The biomass was added in quantities of up to 5 wt.%. It was observed that biomass produced a substantial decrease in the plastic properties of the industrial coal blend, with reductions in Gieseler maximum fluidity of around 50% for 3 wt.% additions of the two different sawdusts. Carbonizations with sawdust additions ranging from 0.75 to 5 wt.% were carried out in a movable wall oven of 17 kg capacity. The bulk density of the charge was observed to decrease with increasing amounts of sawdust with negative consequences on the quality of the cokes produced. Mechanical strength was determined by means of the JIS test. Coke reactivity and post-reaction strength (CRI/CSR indices) were also assessed. The amount of sawdust added was low to prevent any deterioration in coke quality. The advantage of using biomass in coking blends should be seen as a possible way to reduce costs and CO2 emissions and to incorporate alternative raw materials in coke production.The authors are grateful to the Research Fund for Coal and Steel (RFCS) for financial support (Project RFCR-CT-2010-00007). M.G.M. thanks the Government of the Principado de Asturias for the award of a predoctoral grant with funds from the PCTI-Asturias within the Severo Ochoa program. Comments by anonymous reviewers on a previous version of this paper are acknowledged.Peer reviewe

Recycling tyre wastes as additives in industrial coal blends for cokemaking

Two industrial coal blends (B1 and B2) used in cokemaking were selected for this study. Two wastes from scrap tyres (TC, F) were added to these coal blends at different ratios (98:2 and 95:5). The investigation was focused on assessing the influence of the additives on thermoplastic properties of coal by means of the Gieseler fluidity test and thermogravimetric analysis. In addition, the blends were carbonized in a 17 kg electrically heated movable wall oven in order to examine the quality of the resultant cokes. Quality of the cokes produced was evaluated by measuring their cold mechanical strength, reactivity and post-reaction strength. It was found that ash composition of the additives contribute to a deterioration in coke quality. Moreover, F causes a greater decrease in coke strength after reaction with CO2 due to the diminution of bulk density in the coking process and to the higher basicity index. Trace elements were also studied in relation to waste addition.The research leading to these results has received funding from the European Union's Research Fund for Coal and Steel (RFCS) research programme under grant agreement No. RFCR-CT-2010-00007 and contract No. RFCR-CT-2006-00002.Peer reviewe

Partial briquetting vs direct addition of biomass in coking blends

In this work partial briquetting is employed as a means of biomass densification to allow for biomass inclusion in coking coal blends. The effect of increasing the bulk density was evaluated by comparison with direct addition. Two briquettes of different composition were studied. The influence of the briquettes on the Gieseler plasticity of the coals was determined. It was found that the effect of the binder was not enough to compensate for the decrease in plasticity produced by the inert components of the briquettes. Carbonizations were carried out in a movable wall oven of 17 kg capacity and the quality of the cokes produced was tested by evaluating their mechanical strength, coke reactivity to CO2 and post-reaction strength. In addition, the porosity and ash chemistry of the cokes was determined and an attempt was made to establish a relation between these results and the quality of the cokes. Coke quality results suggest that 10–15 wt.% of briquettes containing biomass can be included in coking blends.The research leading to these results has received funding from the European Union's Research Programme of the Research Fund for Coal and Steel (RFCS) research programme under grant agreement No. [RFCR-CT-2010-00007]. M.G.M. thanks the Government of the Principado de Asturias for the award of a pre-doctoral grant with funds from the PCTIAsturias within the Severo Ochoa program.Peer reviewe

The Possibility of Predicting CRI/CSR of Metallurgical Coke using Cokes Prepared at Laboratory Scale (80 g)

The chemical, physico-chemical and mechanical characteristics of coke are of great importance for the smooth running of blast furnace. Coke reactivity is one of the most commonly applied parameters for evaluating coke quality. The NSC test (ASTM-D5341) is the most widely accepted by the steel industry for this purpose. This method involves measuring the reactivity to CO2 at high temperature (CRI index) and the strength of the coke after reaction (CSR index). The ECE-INCAR reactivity test has also proven to be an effective method at laboratory scale for evaluating the reactivity of a coke. For this test, a smaller amount of sample (7 g) is employed than in the NSC test (200 g). In laboratory scale carbonization test, it is impossible to obtain a sufficiently large amount of coke to perform the NSC test. It is therefore useful to establish a relationship between the quality of the cokes prepared at different scales i.e., semi-pilot (17 kg) and laboratory (80 g), by applying the NSC and ECE INCAR tests, respectively. This will make it possible to predict the CRI/CSR of a coke merely by laboratory scale testing. 22 bituminous coals of different geographical origin, rank and thermoplastic properties, chosen from those normally used by the coking industry, were selected for this study. Carbonization tests were carried out in an electrically heated semi-pilot scale movable wall oven of approximately 17 kg capacity (MWO17). The temperature of the wall (1100 ºC) was kept constant throughout the test. The coke was pushed out 15 min after the centre of the charge had reached 950 °C. The coking time was around 3.5 h. Coals were also carbonized at laboratory scale in a sole heated oven. For each test, a sample of 80 g with a particle size <1 mm was heated from the sole at 1050 °C for two hours. The coke reactivity and mechanical strength after reaction of the semi-pilot scale cokes were assessed by means of the NSC test (ASTM D5341 standard procedure). The coke reactivity of laboratory scale cokes to CO2 was determined by the ECE-INCAR method. A linear correlation with a high correlation coefficient was observed between the CRI and CSR with RECE-INCAR index (r2 = 0.906 and r2 = 0.895) in the cokes produced at semi-pilot and laboratory scale, respectively. Coke reactivity and mechanical strength after reaction (CRI/CSR) can be fairly accurately predicted by applying the RECE-INCAR reactivity test to cokes produced at laboratory scale.Peer reviewe

Modification of coking properties due to oxidation. Effect of relative humidity

This work is a systematic laboratory study of coal oxidation under well-controlled temperature and humidity conditions that attempts to simulate those found in the transport and storage of coking coals. Four bituminous coals of different rank were oxidised at 50 °C under different humidity conditions in order to establish the effect that the moisture of the air medium has on their coking properties. The effect of oxidation was examined by means of the free swelling index (FSI), the Gieseler test, thermogravimetry and coke microstrength measurements. The point of zero charge (pHPZC) was explored as a possible method for detecting coal oxidation. In general, the results obtained revealed a deterioration of the thermoplastic properties, a decrease in the point of zero charge and a diminution of the maximum rate of volatile matter evolution. It was observed that the highest humidity level (90% rh) retarded the oxidation of the lowest rank coal during the first few days of oxidation, whereas the higher rank coals were affected more by high humidity conditions. It was also found that low volatile coals become more dangerous after oxidation regardless of the humidity conditions. No significant variations were observed in the mechanical strength of the resultant cokes attributable to the humidity conditions.The research leading to these results has received funding from the European Union’s Research Programme of the Research Fund for Coal and Steel (RFCS) research programme under grant agreement No. [RFCR-CT-2013-00007].Peer reviewe

Generación de H2 verde utilizando nitruro de carbono grafítico sintetizado en varias atmósferas de calcinación

Peer reviewe

Reactivity of biomass containing briquettes for metallurgical coke production

The reactivity of cokes from 12 briquettes prepared from ternary blends of coal, three biomasses and four binders was evaluated. In order to determine the effect of the binder, 4 briquettes without biomass were also studied. The gasification tests were carried out by thermogravimetric analysis at 900 °C. Two gas-solid models i.e. the Volumetric model and the Grain model were applied to describe the behaviour of the cokes. Chars and cokes from the briquette components were also tested to determine the degree of synergy. The two models were able to describe the gasification reaction and the predicted conversion fitted the experimental data very well. Reactivity was also determined by means of a greater scale method and a relationship between the two methods was obtained. The ash composition of the briquette components, the micropore surface area and quantitative optical microscopy were used to explain the gasification results obtained.The research leading to these results has received funding from the European Union's Research Fund for Coal and Steel (RFCS) research program under grant agreements No. [RFCR-CT-2014-00006].Peer reviewe

The effect of briquette composition on coking pressure generation

A coal normally used in coking blends was employed to study the effect of briquettes on coking pressure. The study is focused primarily on two parameters i) bulk density which increases with the use of briquettes and ii) the composition of the briquettes containing materials which have contrary effects on coking pressure. Four briquettes with different compositions were prepared, two of them containing biomass. A non-coking coal and coal tar as binder were included in the composition of all four briquettes. The permeability of the plastic phase to gas flow was studied for blends of coking coal with individual briquette components and for blends of coking coal with 15 wt% of the four briquettes. The coking pressure was measured in a movable wall oven and the mechanical strength, coke reactivity and post-reaction strength of the cokes were assessed by means of standard tests, JIS, CRI/CSR. It was found that all four briquettes produced lower coking pressure than that generated by the coking coal regardless of the increase in bulk density while the cokes retained their quality up to 15 wt% briquette addition.The research leading to these results has received funding from the European Union's Research Fund for Coal and Steel (RFCS) research program under grant agreements No. [RFCR-CT-2014-00006] and No [RFCS-CT-2010-00006].Peer reviewe

Relationship between gCN structure and photocatalytic water splitting efficiency

The influence of precursor and gas atmosphere during graphitic carbon nitride (gCN) preparation on its performance in a photocatalytic water splitting process was studied. Urea and melamine were heated up to 600 °C for 2 h in N2, CO2, air, and static air. The crystalline structure, porosity, chemical composition, and light absorption of the gCNs synthesized were investigated in depth. In addition, their capacity for H2 production was studied in a quartz top Pyrex reactor connected on-line to a Micro-GC. The best results were obtained with urea heated in a CO2 atmosphere. The results were discussed, considering the band gap and the existence of amino groups in the photocatalysts. In addition, the importance of the presence of s-triazine units was emphasized.This work was supported by Spanish National Research Council (CSIC). Project 202080E129. The authors thank Lab Ferrer for their spectroradiometer Apogee SS-110.Peer reviewe

Mechanical strength of bio-coke from briquettes

Cokes made from briquettes composed of a high volatile bituminous coal combined with four different biomasses and four different binders were analyzed in order to evaluate the influence of these materials on their mechanical strength. The results presented in this work are part of a more extensive research plan aimed at widening the range of alternative raw materials that can be included in coking blends. The briquettes were studied by means of proximate and elemental analyses and density evaluation, whereas the cokes were subjected to micro-strength, compression strength, porous characterization and quantitative evaluation of the textural composition by means of polarized light microscopy (PLM). Various parameters derived from these different techniques were used to explain the effects of biomass and binder on the strength of the coke prepared with the briquettes. Bituminous binders are the most effective because they increase Gieseler fluidity and have a lower volatile matter content than molasses and paraffin. The biomasses that gave rise to the most resistant bio-cokes were lignin and a bio-coal, derived from hydrothermally treated waste lignocellulosic biomass.The research leading to these results has received funding from the European Union's Research Fund for Coal and Steel (RFCS) research program under grant agreements No. [RFCR-CT-2014-00006] and No [RFCS-CT-2010-00006].Peer reviewe