Influence of Modified Bio-Coals on Carbonization and Bio-Coke Reactivity

Substitution of coal in coking coal blend with bio-coal is a potential way to reduce fossil CO2 emissions from iron and steelmaking. The current study aims to explore possible means to counteract negative influence from bio-coal in cokemaking. Washing and kaolin coating of bio-coals were conducted to remove or bind part of the compounds in the bio-coal ash that catalyzes the gasification of coke with CO2. To further explore how the increase in coke reactivity is related to more reactive carbon in bio-coal or catalytic oxides in bio-coal ash, ash was produced from a corresponding amount of bio-coal and added to the coking coal blend for carbonization. The reaction behavior of coals and bio-coals under carbonization conditions was studied in a thermogravimetric analyzer equipped with a mass spectrometer during carbonization. The impact of the bio-coal addition on the fluidity of the coking coal blend was studied in optical dilatometer tests for coking coal blends with and without the addition of bio-coal or bio-coal ash. The result shows that the washing of bio-coal will result in lower or even negative dilatation. The washing of bio-coals containing a higher amount of catalytic components will reduce the negative effect on bio-coke reactivity, especially with acetic acid washing when the start of gasification temperature is less lowered. The addition of bio-coal coated with 5% kaolin do not significantly lower the dilatation-relative reference coking coal blend. The reactivity of bio-cokes containing bio-coal coated with kaolin-containing potassium oxide was higher in comparison to bio-coke containing the original bio-coal. The addition of ash from 5% of torrefied bio-coals has a moderate effect on lowering the start of gasification temperature, which indicates that the reactive carbon originating from bio-coal has a larger impact.

FINANCIAL ANALYSIS OF GREEN PETROLEUM COKE AS A COAL BLEND IN STEEL INDUSTRY TO SUPPORT NATIONAL ENERGY SECURITY

Green Petroleum Coke (GPC), produced by Pertamina RU II Dumai, is the product of refined petroleum, which still has good quality but has not been utilized to its full potential. Such as Sulfur 0.5%; FC 86.03%; Ash 0.10%; VM 13.82%; Moist 10, 52%; and the calorific value of 7500 kcal/kg. Therefore, one effort that can do is diversification, namely the use of GPC as a mixture of other fuels (fossil) to increase the selling value of GPC. This diversification is also in line with the national energy policy in PP. 79/2014 that the program aims to increase the availability of national energy sources. This study aims to determine the feasibility of using GPC as a coal mixture in Industry (Krakatau Steel) with an overview of economic aspects. Data obtained by qualitative methods consisting of interviews, observation, and documentation. Based on the research results from 2 scenarios, both scenario 1 (GPC 4%) and scenario 2 (GPC 18%), it is found that the NPV is positive, IRR is above the discount rate, and BCR> 1. Thus, the use of GPC as a coal mixture is considered feasible to run and can support national energy security.Keywords: Diversification, Feasibility, Petroleum Coke, Investment DecisionJEL: G11, G32

A Comparison of Laboratory Coal Testing with the Blast Furnace Process and Coal Injection

The injection of coal through tuyeres into a blast furnace is widely adopted throughout the industry to reduce the amount of coke used and to improve the efficiency of the iron making process. Coals are selected depending on their availability, cost, and the physical and chemical properties determined by tests, such as the volatile matter content, fixed carbon, and ash content. This paper describes research comparing the laboratory measured properties of injection coals that were used over a two-month production period compared to the process variables and measurements of the blast furnace during that study period. In addition to the standard tests, a drop tube furnace (DTF) was used to compare the burnout of coals and the char properties against the production data using a range of statistical techniques. Linear regression modelling indicated that the coal type was the most important predictor of the coal rate but that the properties measured using laboratory tests of those coals were a minor feature in the model. However, comparisons of the Spearman’s correlations between different variables indicated that the reverse Boudouard reactivity of the chars, prepared in the DTF from the coals, did appear to be related to some extent to the coal and coke rates on production. It appears that the constant process adjustments made by the process control systems on the furnace make it difficult to identify strong correlations with the laboratory data and that the frequency of coal sampling and the coal blend variability are likely to contribute to this difficulty.

The Concept of Optimal Compaction of the Charge in the Gravitation System Using the Grains Triangle for Cokemaking Process

Two isomorphic sets of grains, small and large, were analysed—without specifying their dimensions—under the acronym CMC (Curve of Maximum Compression) and taking into account the effects of segregation CMCS. The proposal is particularly valuable for optimal blend preparation in the gravity system in cokemaking. The main advantage of this work is the proposal of using the grains triangle, which limits the values calculated by the relations: bulk density-share of coarse/fine grains, for different levels of moisture content. Each system of changing shares of coarse grains is characterised by a constant C, but there is no need to determine it. Compliance of the calculated value with the experimentally determined value means that the given arbitrary grain set has reached its maximum density called the “locus”. The grains triangle practically covers the vast majority of laboratory and industrial test results, and geometrically or computationally indicates the ability of a given particle size distribution to reach maximum bulk density. This paper presents analysis of the results of tests on crushing, coal briquettes, and grinding coal blend in selected mechanical systems. Results of tests on coke quality (CRI, CSR) in connection with the grain size triangle are discussed.

Impact of the Addition of Pyrolysed Forestry Waste to the Coking Process on the Resulting Green Biocoke

The suitability of the charcoal obtained from woody biomass pyrolysis in a continuous screw reactor at 573, 773, 973, 1173 K temperature profile as fuel and reducing agent in metallurgical applications has been evaluated, in order to reduce the CO2 emissions in these processes. On the one hand, a comparative study between charcoal and commercial reducers has been carried out. On the other hand, different proportions of this charcoal have been added to an industrial coking coal blend and carbonized together in a semi-pilot movable wall oven, to study the influence in the plastic and mechanical properties of the produced biocoke. The charcoal obtained fulfills the requirements to be used as fuel and reducer in non-ferrous processes where no mechanical strength is required, like rotary kilns, in substitution of fossil reducers. Its higher heating value (>32 MJ kg−1) is in the range or over those of fossil coals, with the advantage of not containing polluting elements (S, N) and having less ash. The addition of up to 0.9 wt.% almost does not affect the quality of the biocoke; but the addition of ≥2 wt.% degrades the biocoke mechanical and plastic properties below the demanded requirements. Moreover, biocoke reactivity seems independent of the amount of charcoal added.

Characterization of bio-coal briquettes blended from low quality coal and biomass waste treated by Garant® bio-activator and its application for fuel combustion

Experimental research was carried out on the manufacturing of bio-coal briquettes from a blend of two different types of low-quality coal and biomass waste in the absence of coal carbonization, where the third blend of the material was fermented by adding a bio-activator solution before pressurizing the components into briquettes. The coal samples from Caringin–Garut Regency (BB–Garut) had a low calorific value and a high sulfur content (6.57 wt%), whereas the coal samples from Bayah–Lebak Regency (BB–Bayah) had a higher calorific value and a lower sulfur content (0.51 wt%). The biomass added to the coal blend is in the form of fermented cow dung (Bio–Kohe), and it had a calorific value of 4192 kcal/kg and a total sulfur content of 1.56 wt%. The main objective of this study is to determine the total decrease in the sulfur content in a blend of coal and biomass in which a fermentation process was carried out using a bio-activator for 24 h. The used bio-activator was made from Garant® (1:40) + molasses 1 wt%/vol, and its used amount was 0.2 L/kg. Also, the total sulfur content in the blend was 1.00 wt%–1.14 wt%, which fulfills the necessary quality requirements for non-carbonized bio-coal briquettes. The pyritic and sulfate content in the raw coal was dominant, and the organic sulfur, when fermented with Garant®, was found to be less in the produced bio-coal briquettes by 38%–58%.