Evaluation of demineralized lignin and lignin-phenolic resin blends to produce biocoke suitable for blast furnace operation

Metallurgical coke makers could reduce carbon emissions and material costs by introducing waste lignin in coke oven charges. Two approaches have been studied here to increase the use of lignin in the preparation of metallurgical coke: lignin demineralization with H2SO4 and lignin blending with a low rank coal using phenolic resin as binder. The biocoke obtained after carbonization at 1000 °C from the hydrochar of demineralized lignin (350 °C, 6 h, biomass/water = 0.5 wt/wt) had much higher reactivity than the coke obtained from the low rank coking coal, proving that demineralization of lignin prior hydrothermal conversion is not a valid route for biocoke making. In the other approach, it was found that blends containing 70 wt% low rank coal, 24 wt% torrefied lignin (before or after demineralization) and 6 wt% phenolic resin produced biocokes with suitable mechanical strength for handling but higher reactivity than the coke obtained from the low rank coking coal alone. The microporous surface areas of the biocokes studied did not correlate with their reactivity values

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

Evaluation of demineralized lignin and lignin-phenolic resin blends to produce biocoke suitable for blast furnace operation

Metallurgical coke makers could reduce carbon emissions and material costs by introducing waste lignin in coke oven charges. Two approaches have been studied here to increase the use of lignin in the preparation of metallurgical coke: lignin demineralization with H2SO4 and lignin blending with a low rank coal using phenolic resin as binder. The biocoke obtained after carbonization at 1000 °C from the hydrochar of demineralized lignin (350 °C, 6 h, biomass/water = 0.5 wt/wt) had much higher reactivity than the coke obtained from the low rank coking coal, proving that demineralization of lignin prior hydrothermal conversion is not a valid route for biocoke making. In the other approach, it was found that blends containing 70 wt% low rank coal, 24 wt% torrefied lignin (before or after demineralization) and 6 wt% phenolic resin produced biocokes with suitable mechanical strength for handling but higher reactivity than the coke obtained from the low rank coking coal alone. The microporous surface areas of the biocokes studied did not correlate with their reactivity values

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

Comparison of the quality of the coke produced at different scales

A series of coking coals covering a wide range of coalification, thermoplastic properties and geographical origin were carbonized at two different scales. All the coals used are available in the international market and they are used by the cokemaking industry in blend preparation. The cokes were produced in two movable wall ovens of 15 and 300 kg capacity available at INCAR-CSIC facilities. The quality of the cokes was assessed by means of reactivity towards carbon dioxide and mechanical strength before and after the reaction with CO2. The results obtained are very promising and a good correlation between the quality parameters of the cokes produced in the two ovens was found. The use of a semi-pilot oven against big-capacity ovens in the optimization of complex coking blends allows to obtain valuable results by using small amount of coal (15 kg vs. 300-400 kg) with the advantages that it is quicker, more flexible and of lower cost.European Coal and Steel Community –ECSC- (project 7220-PR/119)Peer reviewe

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

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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

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

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