Visual Detection of Maritime Vessels

This thesis investigates how a tailored Convolutional Neural Network (CNN) can aid autonomous surface vehicles (ASVs) in detecting and classifying maritime traffic for collision avoidance. Several state of the art CNN models are presented and trained on data sets with relevance to the above-mentioned objective. Data collected from different sources are used for training these CNN models in pursuit to obtain a good performing detector. The main data sets are large, general purpose image sets of ships and boats. A smaller image set is also developed in this thesis. This custom data set is constructed from images taken along a predefined path at sea from a video camera. This includes images along docks and of ships in transit at sea. This data set is then split into training and testing images which are in close relation to each other. Through experiments, the various data sets are used to train both a 5 layer deep and a 16 layer deep CNN model to detect ships in an image

Factors influencing dissolution of carbonaceous materials in liquid Fe– Mn

Carbon dissolution from four types of metallurgical cokes and graphite was investigated by using immersion rods in a resistance furnace to clarify the influence of factors governing the rate of carbon dissolution from carbonaceous materials into Fe–Mn melts at 1550 °C. The factors studied were the microstructure of carbonaceous materials, roughness, porosity and the wettability between carbonaceous materials and the melt. Carbon/metal interface was characterised by scanning electron microscopy accompanied with energy-dispersive X-ray spectrometry to investigate the formation of an ash layer. The results showed that coke E had the highest dissolution rate. Surface roughness and porosity of the carbonaceous materials seemed to be dominant factors affecting the dissolution rates. Further, crystallite size did not have a significant effect on the dissolution rates. Solid/liquid wettability seemed to affect the initial stage of dissolution reaction. The dissolution mechanism was found to be both mass transfer and interfacial reactions.publishedVersionOpen Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons. org/licenses/by/4.0/

Flow investigation of multiphase manganese slags

Multiphase slags form the basis of the reduction pathway for manganese ferroalloy production. The present work aims to understand the flow of slag through the coke bed based on experimentation in controlled conditions. Synthetic slags of different basicities were evaluated for their phase composition, viscosity, and flow. The two-phase slag will have two zones: a liquid slag zone and a multiphase zone. The multiphase zone will consist mostly of a solid phase with some liquid slag between the solid particles. The multiphase part will hence have a high viscosity. The liquid zone will flow into the coke bed while the multiphase area will stay. With increasing reduction, the multiphase area will decrease in size until the solid phase is gone and the whole slag will flow into the coke bed. The effective viscosity of slag will decrease with the lowering of the solid oxide phase. The results from flow experiments confirmed that the segregation of phases occurs when slag flows through the coke bed. It is observed that the flow is dependent both on the size of the void and the viscosity of slag.Flow investigation of multiphase manganese slagsacceptedVersio

CO2 Gasification of Densified Biomass: The Influence of K on Reaction Rate

The Boudouard reactivity of metallurgical coke and densified charcoals was investigated in this study. Potassium is known to accumulate in ferromanganese furnaces and hence was evaluated as a catalyst of CO2 reactivity. Samples were impregnated using a gaseous impregnation technique with K2CO3.The reactivity experiments were designed to simulate conditions occurring in an industrial furnace, as used for production of Mn-alloys. To find out the catalytic effect of potassium, the concentration varied from a fraction of a percent up to 5 wt.%. The results show that with increasing potassium content, the CO2 reactivity of coke and charcoal increased, and this change was more significant for coke. The CO2 reactivities of coke and densified charcoal were much closer to each other at the highest content of potassium. Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) showed that potassium distributed on the surface as well as on deposited carbon particles formed on densified charcoal.publishedVersio

Kinetics of Manganese Reduction Comparing Synthetic Slags and Ores for Ferromanganese Production

A fundamental understanding of MnO reduction is important to ensure optimal conditions to produce ferromanganese alloys. In this study, MnO reduction at 1550 C was studied using synthetic slags and ores of varying basicity in a CO-Ar atmosphere. The synthetic slags were of 0.6, 0.8, and 1 basicities. The basicity of Comilog ore was adjusted by adding CaO. Results from the thermogravimetric analysis of synthetic and ore slags confirm that during the reduction of primary slags, the rate of reduction would be constant in the presence of solid MnO phase in the slag. An increase in the rate of reduction would be observed close to the liquidus MnO content when the slag is transitioning from a two-zone to a single-phase slag. After the increase, the rate of reduction will gradually lower in the single-phase liquid slag due to lower activity of MnO. The synthetic slags were found to have slightly higher reactivity compared to ores. It was also seen that in the multiphase area of the reduction, the size of the solid MnO particles increased with time.publishedVersio

Kinetics of Slag Reduction in Silicomanganese Production

In this study, the reduction of three silicomanganese charges prepared from industrial raw materials was investigated under isothermal conditions between 1783 K and 1933 K (1510 °C and 1660 °C). The main reactions examined are MnO and SiO2 slag reduction following the chemical equations MnO(l) + C = Mn(l) + CO(g) and SiO2(l) + 2C = Si(l) + 2CO(g). The charges containing a combination of Assmang ore, Comilog ore, high-carbon FeMn slag with quartz were pre-reduced, melted to a MnO-SiO2-Al2O3-MgO-CaO quinary slag and reduced in presence of coke using a thermogravimetric set-up. The reduced slags were further analyzed using electro-probe micro-analysis to evaluate their MnO and SiO2 contents. It is observed that the reduction pathway occurred in two stages: a first slow and stable stage was followed by a rapid rate increase during the second stage. The rate change shift between the two stages was found to depend on the initial charge’s composition and the extent of reduction, but not on the temperature. Using an established rate equation, the kinetics of MnO and SiO2 reduction were modeled over the first stage. A good fit was obtained between simulated and experimental data.publishedVersionOpen Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/

Isothermal Reduction of Nchwaning Manganese Ore in CO/CO2/H2 Atmospheres

In the industrial production of manganese ferroalloys, incomplete pre-reduction of higher manganese- and iron oxides in the furnace causes an excess consumption of carbon and energy. Pre-treatment of the manganese raw materials in an external unit may alleviate this issue. To optimize the pre-treatment process, a deeper understanding the solid-state reduction kinetics is needed. In this work, Nchwaning manganese ore have been reduced isothermally at different temperatures at two different oxygen partial pressures in CO/CO2 and CO/CO2/H2 gas mixtures, that is four different gas compositions. Isokinetic modeling was used to identify the activation energy range for the different cases and rate expressions were derived using the reaction order model. The derived model expressions adequately reproduced the experimental curves. The effects of temperature and gas composition were quantified based on the model expressions. By reducing the CO content in the CO/CO2 gas mixtures from 70 % to 30 %, the reduction rate was reduced by a factor 3. For the equivalent change in the CO/CO2/H2 gas mixtures, the rate was reduced by a factor 2. The addition of hydrogen increased the reaction rate by a factor of 1.9-2.8 for gases with equivalent thermodynamic potential within the experimental range. If partial combustion of the furnace gas is used to fuel a pretreatment unit, the addition of hydrogen will be beneficial to avoid significantly lowering the reduction rate of the ore.publishedVersio

Effect of Moisture, Hydrogen, and Water–Gas Shift Reaction on the Prereduction Behavior of Comilog and Nchwaning Manganese Ores

The ore–gas reactions in the prereduction zone in a ferromanganese furnace are largely decisive of the overall energy efficiency, carbon consumption, and climate gas emissions in ferromanganese production. An increased understanding of the prereduction zone is thus vital for optimization of the furnace operation. The ore–gas reactions are well known to be governed by kinetics rather than thermodynamics. The raw materials contain various amounts of both chemically bound and surface moisture when fed to the furnace, which may influence the reaction kinetics. This paper presents the investigation of the potential influence of moisture on the prereduction kinetics of two commercial manganese ores, i.e., Comilog and Nchwaning. TGA experiments were carried out by comparing dry and wet ore, as well as introducing H2(g) or H2O(g) to the CO–CO2 gas mixture.publishedVersio

Wettability of cokes by Fe-Mn melt

Four metallurgical cokes were heat treated at 1250 °C to 1550 °C in argon atmosphere. The influence of heat treatment on the microstructure of metallurgical cokes was characterized using X-ray diffraction and Raman spectroscopy. Wettability experiments were carried out using the sessile drop technique. The wettability of cokes with liquid Fe-85wt%Mn at 1550 °C was measured as a function of time. The effect of coke ash content, microstructure, porosity and roughness on the wettability was investigated. In the process of heat treatment, the microstructure of the metallurgical cokes transformed toward the graphitic structure. The Raman spectra showed variations reflecting their temperature histories. Area fraction of G peak increased as the annealing temperature increased and intensity ratios of D to G band decreased with temperature. All the four coke samples showed non-wetting behavior with Fe-85wt%Mn while graphite showed wetting behavior. Coke E with the highest roughness and porosity showed the lowest wettability compared to other cokes. Crystallite size of the coke samples did not seem to have any significant effect on the wettability.publishedVersion© 2020 The Author(s). Published with license by Taylor and Francis Group, LLC This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4. 0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way