Controlled tapping

Metallproduserende industri i Norge bidrar til eksportinntekter, verdiøkning av energi og høyteknologisk kunnskap. En viktig del av metallene som produseres i Norge er ferrolegeringer og silisium. Disse produseres i industrielle ovner ved høy temperatur, og flytende metall tappes ut av ovnene. Etter ovnen vil metallet støpes ut i former før det knuses og sendes til kundene. Tappeprosessen er en viktig delprosess. Avvik i tappeprosessen fører til et høyere energiforbruk, lavere utbytte og høyere sikkerhetsrisikoer. Mye av kunnskapen om denne delprosessen er erfarings basert. Målsetningen med dette prosjektet har derfor vært å forbedre tappeprosessen gjennom en vitenskapelig tilnærming i sameksistens med erfarings basert kunnskap. Dette krever et svært tett samarbeid mellom forsknings baserte partnere som NTNU og SINTEF og industribedriftene i prosjektet. I prosjektet er det utviklet forskjellige modeller av deler av tappeprosessen, som beskriver hvordan metallflyten ut av ovnen er avhengig av inaktive soner og semi-permeable lag i ovnen. Da disse CFD modellene er svært kostbare og tidskrevende er det utviklet forenklede modeller også kalt Reduced Order Modelling. En har sett at modelleringen samsvarer med eksperimentelle forsøk og industrielle erfaringer, og sensistivitets beregninger har vist hvilke parametre som er viktigst for tappehastigheten. Industrielle målinger har også vært prioritert i prosjektet, som kan binde fundamental forskning til eksisterende industrielle prosesser. Det har vært utgravinger av ovner, og også målt parametere som tappetemperaturer og energi i tappegass. På fundamentalt eksperimentelt nivå er det eksperimentelt bestemt SiO dannelsen i Si ovner, oppløsning av kalk i slagg, oppløsning av kvarts i slagg, slagg dannelse i kvarts, karbid dannelse og grenseflatespenninger melom slagg og metall. Prosjektet fokuserer også på rekruttering til denne industrien vha involvering av MSc studenter, PhD kandidater og PostDoc forskere.

The overall results of this project is a better knowledge base when operating the industrial furnaces. The knowledge base is three folded: 1. The industrial campaign has given information about the industrial operation that was not known or not accepted, and it can especially be mentioned the tapping temperatures and the amount of slag in silicon furnaces, that has lead to new projects. 2. The modelling of flow mechanisms inside of the furnaces, on the outside, and in the interface have shown both which mechanisms that govern the tapping, and also the sensitivity of the various parameters. These models has also lead to new activities. 3. Experimental fundamental information regarding sub-reactions that is needed both for understanding the furnace operation and for modelling. Here, both the development of experimental techniques and the reactions in it self is focused. Together this knowledge will affect the way the operational furnaces is operated, especially in the high temperature area. The potential impact from this is a lower energy consumption and CO2 emissions, but equally important an increased safety for peoples and equipment. Some examples of outcomes : - CFD model of industrial furnace flows including inactive zones - CFD model of metal slag separation during tapping in Mn-ferroalloy production - CFD model of gassing through the tap hole in Si furnaces - Reduced Order models of the tapping variations - Knowledge of industrial tapping temperatures. This knowledge has changed the way we look at the tapping process and behavior of metal and slag in the furnaces. - Knowledge of slag amount, slag composition and slag position in the industrial furnaces. This knowledge has changed the way we look at the tapping process and behavior of metal and slag in the furnaces. - New experimental technique to measure the interfacial tension between liquid slag and liquid metal. With this new method, new information on the interfacial tension between Mn-slag and metal is determined. - Industrial knowledge of inactive zones in Mn-furnaces is determined, and mechanisms on the development of TiC in inactive zones is found experimentally. - SiO production from SiO2 and Si has fundamentally been investigated and a mathematical model is developed to be used in larger furnace models. It also showed that the quartz type was not affecting the SiO production. - The development of permeability apparatus lead to permeability data for the Si-process and the Mn-process. This may broaden the possible raw materials added to the furnaces and hence lead to less waste materials.

In the metal producing processes, hot liquid metal will be tapped from the industrial furnaces. In this project NTNU and SINTEF, with the Norwegian industry, determine the fundamentals affecting the tapping operation. Existing knowledge is mainly regarding taphole maintance, the operation of the furnace and the production process. Hence, the new knowledge produced in this project will be the simultaneous effect of the furnace operation, the taphole geometry and the physical parameters of the phases in the furnace, and how they all affect the tapping operation when it comes to metal, slag and gas flow through the tap-hole. The first part of the project will be an intelligence gathering, collecting industrial experience, previous published knowledge combined with scientific input with the purpose of summarizing theories and knowledge needed. This will give the basis for knowledge needed regarding physical knowledge of condensed and liquid materials, regarding flow mechanisms and regarding geometrical knowledge as a function of furnace operation. Since tapping performance is governed by physics affecting the flow in a multi phase system, a numerical tapping model accounting for the governing physics will be applied. However, enhanced input to the tapping model is required. Data from more recent and (potentially upcoming) furnace excavation needs to be analyzed and prepared for the tapping model. This input is collected in a physical model describing furnace design, furnace-materials and their physical state. The physical model will also be strengthened by lab.scale experiments. Industrial measurements will be carried out giving fundamental competence of the real world phenomena. This competence will be used to give input to the model, as well as verifying the results from the model. In this project the recruitment base for this industry will be strengthen by the education of 2 PhD's, 1 Postdoc and more than 8 MSc.